HSI1000 Free Notes PDF

Week 1 Scientific method Observe → Explain → Test Observation: - Enable us to identify and focus in on relevant facts and phenomena under investigation - What we observe can provide clues as to what might explain the phenomena - Can provide the evidence by which we can determine whether va...

Week 1 Scientific method Observe → Explain → Test Observation: - Enable us to identify and focus in on relevant facts and phenomena under investigation - What we observe can provide clues as to what might explain the phenomena - Can provide the evidence by which we can determine whether various explanations succeed or fail. Considerations to be taken into account when making careful scientific observations - Have a very clear sense of the relevant and irrelevant phenomena - Don't overlook anything when carefully observing - Know what was based on fact and conjecture - Make sure the observations are not contaminated by expectational or belief Steam engine Industrial revolution Occurred with the invention of practical steam engines to power machines. - Manufacture in far greater numbers Replace old forms of production and drew many into urban centers, increasing city population Income growth, increase in standard of living and population explosion - Relied on coal Used steam engines to pump water out of coal mines to dig deeper - Steam-powered trains and ships to move material around - Machinery to assist farming which reduced famine However, conditions in crowded cities worsened - Pollution from burning coal - No proper sanitation (cholera, typhoid, typhus and tuberculosis) - Despite this, there was an overall drop in mortality as humans on average survived for longer, alongside high birth rates - Improvements in agriculture (More food) - Improvements in food distribution (reduced shortages) - Improvements in sanitation (sewage systems) This resulted in a population surge - Happened around the world as well Eventually the internal combustion engine would be created Week 2 Human population growth and relationship to climate crisis - Doubled every 138 years - Reason: drop in human mortality Baloney Detection Toolkit (BDTK) → developed by Carl Sagan, updated by various people (Michael Shermer) over the years - Set of questions to establish if something is true or not - Intuitively used in every scientific investigation 3 things to prepare before applying BDTK Is this true?/How do I know?/Where’s the proof? - Skeptical mindset (don’t overdo it) - Fundamental to the practice of science - Scientific explanation → can be falsified - Speculation → can't be falsified - Karl Popper’s philosophy of science - Be aware of your own biases - Practice of science should be objective - Biases affect critical thinking - Awareness of biases can negate their effect - Guard your buttons - Something that sets you off - Something that makes you feel - Something that triggers strong emotions - Make sure your own emotions do not get the better of you - Be aware of claims that makes one feel a certain emotion eg. fear/greed/pity/anger 3 Important types of biases Confirmation bias - Tendency to seek out information that confirms one’s beliefs - Self-fulfilling prophecies Availability bias/availability heuristics - Tendency to use information we can quickly recall - 2 types of decisions - Decisions made quickly and automatically - Decisions made after careful and rigorous analysis - Combat availability bias → make decisions after careful and rigorous analysis, make decisions with a team - Be on the lookout for reflex-based decisions - Ensure that all known evidence and not just available evidence has been considered before the decision is made Illusory truth bias/effect - Tendency to believe false information to be correct after repeated exposure - Exploited by advertisers/marketers/purveyors of fake news Detect nonsense by helping answer 3 questions - Who is behind the information and why - What is the evidence for the claims - What do other sources say about the source and its claims BDTK 1: How reliable is the source of the claim - Identify the source - Find out reliability of source - Look at author/their professional background - Look at organization - Lateral reading → see what other reliable sources say about the source which we are considering - Look and feel of websites are not indications of reliability BDTK 2: What is the source’s perspective? Author’s perspective/bias can be overtly inserted into communication in an attempt to sway you into their way of thinking - Misrepresentation - Falsification - Fabrication Find out the source’s perspective/why were you shared this info/purpose of the info you're looking at - Note that many news organizations have a perspective when reporting - Eg. fox news is considered conservative whereas guardian is considered liberal - Perspective can color a description of something → so it is more/less than what it really is Source funding: where does the money come from? - Advertisement → info will paint the product to be in a good light even if it is not very good - Conflict of interest BDTK 3: Is the claimant providing positive evidence? What is not scientific evidence? - Testimonials - Eyewitness accounts - Sworn statements - Signed affidavits Eyewitness accounts are not scientific evidence → point the scientific investigative team towards where to start looking for evidence What is evidence? - Texts - Photos - Videos - Citations to scientific articles - Data and infographics Evidence must support the claim Evidence must be reliable - Lateral reading Evidence must be relevant - Must support the claim or argument Keep a critical eye out for reliability and misrepresentation - Eg. if the data is presented graphically → is it presented honestly and fairly? - Reverse image searching - Photos can be doctored - Look for context as well as how current the image is → old images can be doctored and used as evidence for current events - Use reverse image search to reveal the source and age of images - Videos can be taken out of context by saying its about something else/edited/not show an entire sequence - Where the video came from - Who created it - Has the video been altered Spurious correlations - Can be used to wrongly convince someone to believe that something is caused by something else Positive evidence - Evidence provided to shoot down other alternative possibilities → not evidence that the current explanation is correct - Claims need positive evidence to support them → not negative evidence against alternative explanations BDTK 4: Where does most of the evidence point? Well established scientific facts require a significant amount of scientific evidence - Generally the explanation where majority of the evidence points is the one that is most often correct BDTK 5: Have the claims been verified by somebody else? Reputable fact checking site - www.snopes.com - Berkeley library - Duke reporter’s lab Reproducibility - Being able to reproduce scientific findings → fundamental to science BDTK 6: Does the claimant use flawed reasoning? Reminds you to think carefully about what the claimant is saying - Arguments involving data → should be presented as a rate instead of absolute numbers Why did world population suddenly increase after WW2 What determines population size - Fertility rate - Mortality rate Mortality dropped in Asia and Latin America - Improvements in public health, sanitation, nutrition Food production and resulting improvement in nutrition → greatest impact Green revolution - Adoption of modern farming methods - Pesticide use - Use of synthetic fertilizers Nitrogen → limiting nutrient - Most of nitrogen is in atmosphere as N2 - Plants cannot access N2 in the air - Nitrogen fixation → converting N2 into usable form of nitrogen Fritz Haber → synthesised ammonia from N2 in the air and H2 gas Carl Bosch → chief engineer at BASF who scaled the experiment to industrial levels - Haber-Bosch process - Took off after WWII - Dramatically increased crop yields - US corn: 5x - France wheat: 6x - China wheat: 4x - Japan wheat: 3x - Leads to fall in famine - Consumes 1% of the world’s energy - Produces 1.4% of world CO2 emissions Inefficient fertilization processes - At most only half the N2 is taken up by plants, usually only a third or less is used → 85-90% of the N2 could actually be used - Rest of the N2 either: - Evaporates - Converted back to N2 by denitrification - Goes into water supply - Lost through soil erosion - Result in considerable environmental damage Week 3 Theories and hypotheses - Scientific explanation - 2 basic ways in which theory differs from hypothesis Scientific explanation - Account to why something is the case - Must be testable or falsifiable - Eg. “it was fate” is not a scientific explanation as it is untestable and unfalsifiable Hypothesis - Tentative or unproven scientific explanation - Not yet subject to testing or falsification Theory - Scientific explanation with broad and deep explanatory power - Conceptual framework for providing explanations - Experimentally well tested rules and principles that reveal underlying explanatory similarities between diverse phenomena Well established theories: - Newton’s law of motion - Law of gravitation - Germ theory - Evolution - Atomic theory - etc. - Serve as “conceptual frameworks” for providing scientific explanations - Tested rigorously and continue to pass all tests Obsolete theories - Thought to be correct at the time but now proven wrong - Eg. aristotelian world view Novel theories - Explain what is known but also anomalies - Still under investigation and testing Well-established theories undergo revision when new evidence is uncovered → science is self correcting - Well established explanations - Contested explanations - Even wrong or obsolete explanations Causation and correlation Causation - Cause always precedes the effect - Causal explanation may help in explaining phenomena - May not be simple to provide - Combination of causes which leads to the effect - Cause and effect can refer to groups - The same effect may result from more than just 1 cause - An effect might not always result from a given cause eg. not all smokers get lung cancer (survivor bias) - Causal explanations can be negative eg. wearing mask prevents COVID transmission - Causal explanations can involve a series of linked causes and effects eg. A causes B which then causes C - A is a proximate cause of B which is a proximate cause of C, A is thus a remote cause of C Correlation Degree to which two properties move in coordination with each other - Eg. tendency for larger men to have larger shoe sizes Perfect, positive, negative and no correlation Perfect - Direct 1 to 1 correspondence between changes in 2 properties - Eg. age of tree = no. of rings in its trunk Positive - When one quantity goes up → the other will go up as well and vice versa - Eg. child mortality rate with fertility rates Negative - When one quantity goes up → the other will go down as well and vice versa - Eg. number of hours spent studying in a week vs. number of hours spent gaming in a week Perfect correlation → all data points lie perfectly on the line Strong correlation → data points are not scattered very much away from the line Weak correlation → data points are significantly scattered away from the line No correlation - No relationship at all between the two properties → data plot will look very random, no trend line - Eg. no correlation between student’s exam scores and their height Relationship between cause and correlation Correlation does not imply causation - 2 properties moving in coordination does not mean one caused the other - Causal relationships tend to have correlated properties Types of scientific explanations Providing a scientific explanation enhances understanding of phenomena Causal mechanism - Linked chain of proximate cause and effects leading to the final effect - Enhances our understanding of the phenomenon - May even provide us with a means of reducing/enhancing the effect Underlying processes - Redescribe observations in terms of fundamental processes - Reductionist approach - Eg. brownian motion → discovered in 1828 by Robert Brown → cause by random motion of water particles Scientific laws - Generalized descriptions of regularities observed in nature - Eg. Boyle’s law → discovered in 1662 by Robert Boyle → pressure of gas is inversely proportional to its volume - Eg. of scientific laws → Law of motion/gravitation → expected to be universally held - Eg. of laws in humanities → Law of supply and demand Function - Explanation based on the purpose it serves - Eg. why do humans have a heart → needed as the organ to pump blood around the body Interdependence between different ways of explaining phenomena → often one explanation may require another explanation of its own Type of strategy adopted → depends on what/how detailed the required explanation is Sometimes there are multiple explanations for a particular phenomenon → on what basis to choose from competing scientific explanations? Occam’s razor (named after William of Ockham in 1825) - Methodological principle - Given competing explanations, any of which would, if true, explain a given puzzle, we should initially opt for the explanation which itself contains the least number of puzzling notions - Choose the simplest explanation that provides the correct answer - There is no guarantee that the simplest explanation is the correct one, but it is a better starting point Scientific models: Tools to understand nature - Simplified representation of nature - 3 categories - Physical models - Mathematical/computer models - Conceptual models Physical models - Physical objects representing an aspect of nature, physical objects to better understand nature - Eg. globe → model of planet earth / architectural models of buildings - If the scale is correct → physical models can simulate complex air and water flow to a high degree of accuracy not possible with other types of models Conceptual models - Cut down versions of reality with only the most important parts of interest included to understand what is happening - Depict concepts within science to explain phenomena and make predictions - Eg. maps, diagrams, figures - Models may be abstract (not representative of its real world counterpart) but still useful in assisting understanding of the topic - Eg. lewis chemical structures are used to explain phenomena and make predictions even if chemists know there are no lines between atoms/structures do not resemble the real world counterparts Mathematical/computer model - Maths is able to explain nature in some way 𝐴 - Eg. boyle’s law → can be expressed in a mathematical formula eg. P = 𝑉 - Eg. drawing a trend line → mathematical model of ideal relationship between 2 properties - Many scientific laws are represented by mathematical formulae - Consider all the necessary laws relevant to the phenomenon before modeling it Projections vs predictions Prediction → something expected to happen Projection → a “what-if” prediction - Eg. climate forecast model to project what would likely happen if no action is taken regarding carbon emissions Different types of models can all be interrelated to each other Models, when made too simplistic, can produce wrong results - Can be revised as science is self-correcting Models - Based on theories - Can be used to test hypotheses → make a prediction about the outcome if the hypothesis is correct - Subordinate to higher level theories - Eg. law of motion and gravitation → can be used to generate a computer model for the solar system Tutorial 1 The 3 cardinal sins - Fabrication - Construction of results/data that never occurred during experimentation - Falsification - Alteration of results/data to support certain claims - Plagiarism - Using/representing the works of others as your own - Pass yourself off as an expert when you are not → make a claim that is dubious (but others will be more inclined to believe you) CItations - Establishes a paper trail - Allows reader to verify evidence from the original source on their own - Allows writer to establish academic accountability - Gives credit where due Rules of citations - Whenever article mentions something that requires support → reader should be able to locate sources with ease - Have citation appear at the appropriate place (eg. intext citations) - Citations should be complete Types of sources - Primary - First Hand source eg. Marie Curie’s notebook - Secondary - Eg. summary paper written by someone who read the primary source - Tertiary - Eg. wikipedia article referencing the secondary source Credibility vs accessibility - Secondary and tertiary sources are more accessible → but some information may be lost Credible sources - Complete citations at appropriate places even just for ideas - Primary sources tend to be less accessible - Higher chance for tertiary sources to be corrupted → less credible - Primary sources are not always reliable - Choosing appropriate sources is situational Illusory truth bias - Tendency to confuse familiarity with the truth - Repetition causes statements to be easier to process, leading people to believe them as more truthful Confirmation bias - Tendency to seek out evidence in line with our beliefs Availability bias - Tendency to reach conclusions and make decisions based on what is readily available Buttons - Something that triggers strong emotions in you - Triggered buttons cause your emotions to override your objective critical thinking Week 4 Testing of scientific explanations How do we test explanations? - By simple observation (if possible) Figure out something that should happen - Eg. if planets orbit the sun → all phases of Venus observable Theory → model → prediction → experiment Main concerns of scientific observation Have we overlooked anything? Issues to address when designing an experiment - False confirmation - Results suggest explanation is correct when it is not - Encountered when alternate explanations give the same result - Eg. cold fusion/polywater - False rejection - Results suggest explanation is wrong when it is not Poorly designed/controlled experiments can lead to false confirmation/rejection Community provides critical review of scientific explanation Contemporary scientific research - Observation/question - Observe → explain → test - Research topic area - Literature search - Searching published works to see if others observed similar phenomena - Have others observed similar phenomena - Did they provide an explanation - Do you agree with them - Did you overlook anything - Hypothesis - Speculative/tentative, falsifiable explanation - Does an explanation already exist - Do you have a novel/better explanation - Test with experiment - Design and run experiment to falsify hypothesis - Can we test predictions of the hypothesis - Can we produce a model - Research requires funding → Proposals need to be approved to obtain funding, and results need to be delivered - Analyze data - Does the data support or refute the hypothesis - Report conclusions - Getting published - New works are only accepted into the literature after rigorous reviews Publishing process - Perform original research - Prepare manuscript following guidelines - Submit to editor and suggest referees - Editor briefly reviews journal, if deemed unsuitable for their journal it will be rejected → find a new journal to publish the work in - Sent for peer review/reviewed by referees - Peer reviewers make recommendation to editor on changes that need to be made → or it may get outright rejected - Editor sends the manuscript back to researchers → revise manuscript and address comments - Resubmit manuscript → potentially reviewed again - If manuscript is not rejected → published Uncertainty All measurements have associated uncertainty - Measurement ± uncertainty - Use a more precise instrument to give more decimal places → reduces uncertainty of the measurement - Repeat experiment many times to observe difference in readings - Due to human error - Uncertainty can also be called margin of error - Uncertainties are associated with confidence levels (usually 95%) - Confidence level → confidence that true value lies in range of uncertainty - Confidence interval → range of values (mean ± uncertainty) Uncertainty in average of measurements - Relevant when observing specific number/quantity Uncertainty in individual measurements - Relevant when observing range of measurements Uncertainty contingency table Precision The smaller the uncertainty, the higher the precision → more precise measurements means a smaller uncertainty High precision → more significant figures - Digit of uncertainty → significant figure - Eg. 20 ± 1 → 2sf - Eg. 20 ± 10 → 1sf - Eg. 20.0 ± 0.1 → 3sf Accuracy Closeness of measured average value to true value - Systematic error: How far off measured average value is from its true value Accuracy of an instrument → how far off averaging a lot of readings is from the true value using this instrument If the method/instrument being used is inaccurate → margin of error will give no information on where the true value is → validate and calibrate the method first Eg. measuring tree → tilt distortion - Ensure camera is level with the ground - When using smartphone → don’t expect the result to be super accurate - Unlikely for true value to be within the confidence interval Uncertainty in individual measurement does not include systematic errors If systematic error > uncertainty → uncertainty can no longer tell us where true value lies Testing causal explanations in health science How to establish a causal link? - Randomized control trial (RCT) - Intervention group → receives the medicine of interest - Control group → standard care or placebo - Participants blinded to treatment they receive - Both groups followed for specific duration of time or until occurrence of outcome of interest - When RCT concludes → 2 groups are compared to assess the differences in the outcome of interest Control group necessary - Serves as baseline for comparison Random selection - Eliminates selection bias, ensures baseline characteristics are distributed equally - Eliminates confounding and establishes basis for testing statistical differences between the groups and the measured outcome - Any significant differences between the randomized groups in the measured outcome can be attributed to the intervention and not to other factors - Random selection allows for use of mathematics associated with random numbers in stats to generate particular margins of error To halve the margin of error → 4x the number of test subjects are needed Does sample size matter - Participants in a RCT are a sample of the population - If the sample size is not large enough → inconclusive if the treatment results in the observed change - The differences observed could be due to transvariation which is often found in small samples - Smaller samples may have overlaps in the margin of error → uncertain if the treatment was the cause of the observed change Blinding - Ensures objectivity - Minimises risk of conscious and unconscious bias - May not always be possible to double blind - Open label RCT → no parties are blinded - Some RCT may be single blind → only participants are blinded 3 rules of thumb RCT with double blind → apply the rules of thumb - No overlap in confidence intervals means that the difference is statistically significant at 95% confidence level - If overlap is less than ⅓ → difference could be statistically significant - If overlap is more than ⅓ → difference is not statistically significant If effect size < margin of error → overlap is greater than ⅓ and the difference is not statistically significant Effect size → experimental group result - control group result Week 5 Epistemic responsibility - What is scientific inquiry - Why need to know how science works - Why is this relevant 3 philosophies of science - Empiricism - Rationalism - Skepticism Observe - Explain - Test - Propose hypotheses with empirical evidence - Test hypotheses skeptically → explanations might be fallacious - New observations or experiments - Explain the universe by corroborated hypotheses Critical thinking - Ability to reason - Critical look at what and why we know what we know Why study climate change - Understanding it allows us to combat it more effectively - Illustrate pseudoscientific thinking → climate change has become the focus of anti scientific positions - Epistemic responsibility → William Kingdon Clifford/Thomas Henry Huxley Scientific inquiry → way of interpreting the world we live in - Epistemic responsibility - Justify beliefs with evidence → positive evidence Cause of climate change - Increased CO2 due to burning of fossil fuels - How do we know there is O2 in the atmosphere - How do we know that combustion involves O2 Composition of atmosphere - 78.08% Nitrogen - 20.94% Oxygen - 0.93% Argon - 0.04% Trace gases - CO2 → 420 ppm (parts per million) - CH4 → 1900 ppb (parts per billion) - Nitrous Oxide → 335 ppb Empedocles of Agrigentum → introduced idea that matter is made up of 4 universal elements fire, air, water and earth (Empedocles’s cosmogony) - Proposed that the 4 elements could be mixed in different proportions and produce complex substances - Combined by love and separated by strife - Substances are temporary and elements are everlasting - Love as an attractive force and strife as a repulsive force Is this a scientific theory? - Well-substantiated explanation - Rigorously tested evidence - Widely accepted Empedocles’s cosmogony - Conceptual framework to explain all forms of matter - Was standard dogma for 2000 years - Ancient greeks → loathe to perform experiments - In an experiment → intervene in nature, thus results will be artificial reflecting only the results of intervention - To them → scientific inquiry requires them to stand back and observe the nature of things to reveal themselves Aristotle → test of Empedocles’s cosmogony - Simple distillation of seawater Ancient Greeks’ view of atmosphere - Air was a single element - Aristotle water cycle - Evaporation of water into the atmosphere ←→ condensation as clouds and its return to earth as rain - Successful application of Empedocles’s Four Elements Theory Da Vinci → proposed that atmosphere might be something other than a single substance - Observed that air is not completely consumed during combustion John Mayow → showed that combustion and respiration requires only a part of air which he called spiritus nitroaereus - Experiment with lit candle or mouse in closed container over water - Caused water to rise and replaced 1/14 of the air’s volume before extinguishing the subjects - Referring to oxygen Jan Baptist van Helmont (1630) → recognized that many reactions produce substances “far more subtle or fine than a vapor, mist, or distilled oiliness, although many times thicker than air” - Experiment where he burned charcoal → vapor given off termed “gas sylvestre” (wood gas) - Referring to CO2 → coined the term “gas” - Recognized that CO2 was produced in other processes ie. fermentation of wine Joseph Black (1756) → searching for cure for gallstones - Found that magnesium carbonate gave off a gas when heated - Gas turns limewater milky - Did not support life or combustion - Proved that this gas is naturally present in the atmosphere → confirmed that air is not a single substance - Identified that CO2 is present in exhaled breath Stephen Hales (1727) → suggested that the atmosphere may play a role in the growth of plants - “Plants very probably draw through their leaves some part of their nourishment from the air” → referring to CO2 - Recognized by Jan Ingenhousz (1796) The above discoveries identified: - The importance of CO2 - Carbon transportation mechanism - Respiration is another form of combustion What is combustion? - Solution required the discovery of O2 - Understanding of the role of O2 in combustion Jean Rey → discovered: - Metals changed and gained weight when heated - Explanation: incorporation of air into metal Johann Becher & Georg Stahl → credited with establishing the phlogiston theory for combustion - All combustible materials are made of 2 parts - Phlogiston → part given off when a substance burns - Remaining part → dephlogisticated part to be the substance’s true form - If substance gave off a lot of heat → rich in phlogiston Defects of the theory - Air has no role in phlogiston theory → modified by Johann Heinrich Pott, argued that air attracts phlogiston - Increase in weight of metal after combustion → implies that phlogiston has negative mass Phlogiston theory → prevailing theory for much of the 18th century Discovery of oxygen → critical - Robert Hooke → Produced O2 - Ole Borch → Failed to realize it was a chemical element - Mikhail Lomonosov → Due to widespread of phlogiston theory - Pierre Bayen → Did not isolate O2 Michael Sendivogius (1604) → described substance in air termed “cibus vitae” (food of life) - Recognized that this substance is the same as the gas when saltpetre (potassium nitrate) is heated - Isolated O2 and correctly associated it with the part of the atmosphere required for life Cornelis Jacobszoon Drebbel (1621) → performed similar experiments on potassium nitrate - Purified the “spirituous part of it that makes it fit for respiration - Could sustain up to 12 men in a submarine for 1-3 hours Carl Wilhelm Scheele (1771) → produced O2 by heating mercury oxide and various nitrates - Termed this gas “fire-air” → candle burns more brightly in its presence - Published in 1777 Joseph Priestley (1774) → conducted experiment where he focused sunlight on mercury oxide in a glass tube - Liberated gas was termed “dephlogisticated air” → supported combustion - Candles burned brighter in this gas, mice were more active and lived longer breathing this gas - Published in 1775 Antoine-Laurent Lavoisier (1774) → received guidance from Priestley and Scheele - Claimed later to have discovered O2 independently → termed “vital air” - Struggled to prove whether O2 was a new element or a compound Henry Canvendish (1766) → water formed when “inflammable air” was burnt - Lavoisier proposed “water is not an element but is a compound made of inflammable air and vital air” - Inflammable air → Hydrogen, vital air → oxygen Lavoisier’s insight → created greatest Kuhnian paradigm shift in the history of Chemistry Antoine-Laurent Lavoisier - Demolished phlogiston theory and revised all chemical theory - Oxygen combines with other substances during combustion - Respiration is a slow form of combustion → established in a collaboration with Pierre-Simon de Laplace - Established law of conservation of mass - Wielded Occam’s razor → cleaved ontological belief from the body of science - Wrote first modern chemistry textbook - Recognized that combustion is solely about the reaction with oxygen Who discovered O2? National bias → attribution of priority - Scheele → first to isolate oxygen - Priestley → first to publish - Lavoisier → first to understand Occam’s razor applied (principle of parsimony) → none are credited - O2 discovered and isolated more than a century before their births - Sendivogius isolated O2 and correctly associated it as part of the atmosphere Development of explaining Earth’s surface temperature Jean-Baptiste Fourier - Modeled Earth’s temperature - Contemplations of heat flow → consider Earth’s temperature - Realized Earth itself must radiate → termed “radiant heat” (IR radiation) - Calculated Earth’s temperature as -18°C - 1824 → realized his model was missing the atmosphere → insulator preventing some radiant heat escaping to space and returning it to warm the surface of Earth - First formulation of greenhouse effect Nils Gustaf Ekholm → coined the term “greenhouse effect” in around 1900 Observe - Explain - Test - Fourier observed Earth’s surface temperature - Developed theoretical explanation to account for this temperature → energy received from the sun would be balanced by the radiant heat from the Earth - Measured radiant heat from the Earth - Inputting the numbers into his model → substantial discrepancy - Result of test: inferred that atmosphere must play a role in keeping Earth warm Fourier → different roles of scientist - Theoretical scientist → develops testable theories, putting together mathematical and computer models - Models make predictions that can be tested against observations collected by experimental scientists - Experimental scientists → collect observations Work of Fourier led to several questions - What role does atmosphere play in warming Earth’s surface - What is it about atmosphere that explains this role - What and who discovered the underlying process John Tyndall (1859) → credited with explaining greenhouse effect - Measure absorption of radiation by gases - Built his own equipment → ratio spectrophotometer - Realized importance of water vapor in absorption of terrestrial radiation Tyndall determined - CO2 90x more effective at absorbing IR radiation than air - CH4 403x more effective - H2O vapor 16000x more effective Eunice Foote (1856) - Experiments where she filled glass jars with water vapor, carbon dioxide and air - Compared how much H2O, CO2 and air were heated up in the sun - CO2 has highest effect of being heated up - Speculated that concentration of CO2 could influence global temperatures Greenhouse effect - Absorption of terrestrial IR radiation by gases in atmosphere → primarily H2O and CO2 - Ratio spectrophotometer → “science revolution is frequently precipitated by invention of instruments” - Ability to determine absorbance of IR radiation due to different gases rather than simply the broad absorption of all radiation Arvid Högbom (1890) - Attempted to quantify sources of CO2 emission → to understand the global carbon cycle - Industrial sources was comparable to natural sources Svante Arrhenius - Considered effect of changing amount of CO2 in the atmosphere - Calculated that doubling atmospheric CO2 → raise average global temperature by 5-6°C - Expected global warming would take thousands of years → thought it would be beneficial to humanity Guy Callendar (1938) - First to demonstrate Earth’s surface temperature had increased over last 50 years - Argued that this increase was due to rising CO2 concentrations - Callendar effect → link between atmospheric CO2 and global temperatures - Thought warming would be beneficial Charles Keeling (1958) → received funding to collect CO2 samples at Mauna Loa observatory in Hawaii - Produced data in 1961 showing that CO2 levels were rising steadily - Known as Keeling curve - National Science Foundation used Keeling’s research in 1963 in its warning of rapidly increasing amounts of heat-trapping gases Lyndon B Johnson (1965) → science advisory committee published landmark report “restoring quality of our environment” - Warned harmful effects of fossil fuel emissions - Burning fossil fuels directly increased atmospheric CO2 James Hansen (1981) → published study - High probability of warming in the 1980s - 1988 → 99% certain that warming trend is not natural (grounded in statistics) - Cause-and-effect relationship between increased CO2 and warming trend - Global warming was human caused Greenhouse effect vs global warming Greenhouse effect → process that causes surface to be warmer due to atmosphere - Metaphor: atmosphere acts like a blanket - Limit: emissions to atmosphere which does not follow this metaphor - Eg. emissions of sulfate aerosols from volcanic eruptions will lead to cooling of the planet Global warming → expected increase in magnitude of greenhouse effect Metaphors → important in communicating scientific ideas but reduction of ideas to a metaphor comes at the cost of precision - Consider audience which is being addressed - Also used by unscrupulous to peddle pseudoscientific nonsense Why is Earth’s surface warmer in the presence of its atmosphere Surface is warmer as it receives energy from 2 sources: - Sun - Atmosphere Mathematical model to estimate magnitude of greenhouse effect The model of Fourier - Recognized that the atmosphere was responsible for keeping the Earth warm and conducive to life - Repeat Fourier’s calculations predicting the temperature at the Earth’s surface in the absence of an atmosphere, then modify the model to include an atmosphere Earth’s most significant source of energy → the sun - Energy emanating from the Earth’s core → amount is several orders of magnitude smaller than the energy received from the sun - Models as simplifications of real systems → will always introduce errors - Scale analysis used to decide which effects are to be neglected in the model - If the amount of energy entering and being absorbed by the Earth ≠ amount of energy being emitted and leaving the Earth → Earth system would be getting hotter or colder depending on the direction of imbalance - Relationship between temperature and emitted energy → Stefan-Boltzmann law - Emitted energy from an idealized object → proportional to the 4th power of the absolute temperature measured in K - Assumes that the emitting object can be treated as a blackbody - Theoreticians make assumptions that never fully hold in nature in order to be able to provide deep insight into the structure of nature Emission of radiation from the Earth and the sun follow the Stefan-boltzmann law to a good approximation - Calculate temperature of Earth in the absence of atmosphere → assume that temperature is constant - Untrue as there are fluctuations in the Earth’s temperature → range of 4°C - If the model accounted for this variation, we would need to account for: - Elliptical orbit of Earth around the sun and the tilt of the Earth’s axis - Distribution of land and ocean across Earth’s surface - Assumption → no seasons, use average of the amount of solar radiation that the Earth receives over a year If the amount of energy being absorbed by the Earth = amount of energy being emitted by the Earth → constant Earth surface temperature - Energy from the sun reaching the top of the atmosphere → Solar constant, S - Measured and given by 1370 W/m2 Total amount of solar energy being absorbed by Earth every second → S x πr2 (cross section of the Earth where r = radius of Earth) Absorbed energy = Emitted energy Emitted energy → σTE4 x 4πr2 where σ = Stefan-Boltzmann constant (5.67 x 10-8 W·m-2 K-4) TE calculated by this model to be 279K (6°C) - Not the temperature calculated by Fourier - 30% of the incoming solar radiation will be reflected either by the Earth’s surface, clouds, or the atmosphere itself → only 70% of solar radiation is absorbed and acts to heat the Earth - Fraction of incoming solar radiation that is reflected → referred to Earth’s albedo - Given by the symbol A - Multiply solar constant by (1-A) to calculate a new temperature for the Earth’s surface - Calculated that Earth’s temperature is 255 K(-18°C) 255K → uninhabitable - Need to account for the effect of the atmosphere - What should be included in the model to account for atmosphere Model requirement → capable of representing the differential absorption of solar and terrestrial radiation - Allow us to represent changing atmospheric concentrations of greenhouse gases - By modifying how well the atmosphere absorbs infrared radiation - Model does not need to account for temperature of the atmosphere or how temperature varies with altitude → required to include a lot of radiative theory which would greatly complicate the model - Unnecessary as we are not interested in the temperature of the atmosphere - Only interested in the temperature of the Earth’s surface Model parameters - Accounts for the absorption of solar radiation - Accounts for the absorption of terrestrial radiation Assume Earth is 0K - Solar radiation → absorbed energy = (1-A) x S x πr2 - Sphere to circle area ratio = 4, reduce result by factor of 4 - Effective radiation hitting the top of the atmosphere → 240 W/m2 Atmosphere absorbs 90% of Earth’s emitted radiation and 20% of incoming solar radiation → emits half of this absorbed radiation upwards into space and the other half is emitted downwards to the Earth’s surface Stefan-Boltzmann law → Earth with atmosphere TE = 288K (15°C) - Greenhouse effect resulted in a 33°C increase in the global temperature Observations from the model and thought experiment - Solar radiation charges up the atmosphere like a battery → atmosphere becomes a bigger source of radiation to heat up the Earth’s surface than direct radiation from the sun - Earth’s system moved towards equilibrium → amount of radiation absorbed by the atmosphere is proportional to the amount entering the atmosphere (1+τ𝑠) Simple mathematical model → Fg = Fs (1+τ𝑔) - Fg → Terrestrial radiation, τg → Terrestrial transmittance 𝑆(1−𝐴) - Fs → Solar radiation = 4 , τs → Solar transmittance Fs ↑ ⇒ Fg ↑ ⇒ Tg ↑ τs ↑ ⇒ Fg ↑ ⇒ Tg ↑ τg ↓ ⇒ Fg ↑ ⇒ Tg ↑ Climate change has causal origins - Identified underlying process explaining the greenhouse effect - Underlying processes → alternative form of scientific explanation - Role of CO2 in absorbing IR radiation → underlying process Model is able to quantitatively predict the effect of increasing greenhouse gases on temperature Week 6 Climate change Climate vs Weather Climate - Conditions in one region over a long time - “What is expected” Weather - Conditions in one location at one time (short term) - Combination of temperature, humidity, precipitation, cloudiness, visibility, wind - Reflects short term conditions of atmosphere - “What is actually gotten” Climate change → shift in long-term weather conditions - Global warming - Resultant large scale shift in weather patterns Global warming (cause) and climate change (effect) Scientific consensus on climate change: - IPCC (intergovernmental panel on climate change) - Unequivocal that human influence warmed the atmosphere, ocean and land - Unprecedented, inevitable and irreversible Climate change is real: argument from authority? → should we accept that it is real because there is a scientific consensus? Consensus: general agreement of opinion Scientific method argues for objective framework - Facts or observations explained by hypothesis → tested and retested until refuted (refined by testing) - As more observations are gathered → build off one explanation and add details to complete the picture - Group of hypotheses may be integrated and generalized into a scientific theory or scientifically acceptable general principle or body of principles offered to explain phenomena Scientific consensus achieved - Majority of scientists agree upon a position - Based on a large amount of evidence - Not just a general agreement → dependent of the expertise of the scientists in question - Based on the accumulation and verification of evidence Scientific consensus can shift (proved by Galileo) - Scientists are human - Science is a human endeavor Climate change is real → consensus reached only after many experiments were conducted and verified by many scientists Scientific communities vs scientific consensus and its significance - Scientific community → prerequisite for emergence of a consensus - Discoveries discussed, debated and tested - Led to consensus on climate change - Eg. of scientific community → royal society of london (Francis Bacon) - Ultimate goal of scientific inquiry → power over nature Scientific consensus is not an appeal to authority → fallacy of appeal to authority - Cognitive bias to respect authority - Forfeit of reason to the group comes from its authority and desire to belong - Fallacious when said authority is not a subject matter expert (does not possess the expert knowledge required to make judgment on the subject of discussion) - Scientific consensus is formed by community of experts Establishing the scientific consensus To build scientific consensus - Significant number of scientists needed - Working on the problem and making measurements - Developing conceptual and mathematical models - Verifying each other’s work 1st mathematical model to predict the effect on global temperature of increasing CO2 - Svante Arrhenius → built upon conceptual work of Joseph Fourier → experimental analysis of John Tyndall and Eunice Foote CO2 → greenhouse gas → impact climate Scientists agreed CO2 was a greenhouse gas - Increase in atmospheric concentrations → affects climate - Argued that water vapor is a greenhouse gas → so much more H2O than CO2 - Skeptical that small increases in CO2 has a big effect in climate - Present today in arguments from climate change deniers H2O and CO2 do not absorb IR radiation at the same wavelengths - Wavelengths where H2O absorbs very little but CO2 absorbs greatly - Increased CO2 → increased absorption of IR at these wavelengths → affecting Earth’s surface temperatures Roger Revelle & Hans Suess (1957) → recognized that there was a need to return to the work of Guy Callendar - Published an influential paper recognizing the importance of studying the Callendar effect - Acknowledge inadequacy of current data - Advocated for accurate measurements of CO2 International Geophysical Year (1 July 1957 - end of 1958) - Crucial in bringing together scientists from across the globe - Study many issues of geophysical concern → including climate change - Keeling curve → showed that instruments had the sensitivity to measure accurately small changes in CO2 - Showed that from 1958 - 1965 → CO2 concentrations rose by 1% or 3 ppm - Greatly concerning to the scientific community By 2000 → about 25% more CO2 in atmosphere than at present - Modify heat balance of atmosphere - To the extent that marked changes in climate could occur Scientific consensus informs public policy - Lyndon Johnson’s special message to US congress in 1965 - In the 1970s in US → impact of rising CO2 on climate → informing national policy in terms of energy, national security and economy - End of 1970s → National Academy of Sciences (US) evaluated evidence for CO2 induced climate change - Plethora of studies from diverse sources indicates consensus that climate changes will result from man’s combustion of fossil fuels and changes in land use - Consensus of not just conceptual understanding of CO2’s effect on Earth’s temperature - Consensus of expectation: if fossil fuels continue to be burnt, climate changes will result Scientific consensus established on theory and impact but not yet on timing - Established consensus that burning fossil fuels leads to climate change - No consensus on when this climate change will happen Scientific consensus - Can inform public policy - Is not an argument from authority - Is not simply a general agreement Scientific consensus established on what will happen but not on when (regarding climate change) - Required to guide public policy - Profound impact on society - Most scientists at the time thought the changes would not begin to become detectable until the 21st century Determining when climate change would be detectable - Requires sophisticated climate models - Mathematical descriptions of the climate programmed into computer models - Need to estimate natural climate variability 1988 → James Hansen published a seminal paper - Provided first estimate of natural climate variability → 0.13℃ - Not standard deviation of temperature → actually standard error of average temperature - Standard deviation of temperature is larger than 0.13 - Observed rise of 0.4℃ → 99% confident that global warming was observed How does 0.4℃ rise in global average temperature give 99% confidence that global warming is happening - 68-95-99.7 rule - 68 → percentage of events that occur within 1 standard deviation from the mean - 95 → percentage of events that occur within 2 standard deviations from the mean - In the social sciences → 2 standard deviation threshold used to identify statistical significance (event beyond 2 standard deviations is considered statistically significant) - 99.7 → percentage of events that occur within 3 standard deviations from the mean 3 standard errors → 0.13 x 3 = 0.39 - Only 0.3% of naturally occurring global average temperatures are expected beyond this limit - We only expect a naturally occurring global annual average temperature beyond this limit once in 370 years IPCC → published first assessment report in 1990 - Global mean surface air temperature has increased by 0.3 to 0.6℃ over the last 100 years - Broadly consistent with predictions of climate models but also of the same magnitude as natural climate variability IPCC 2nd assessment report in 1995 - Balance of evidence suggests a discernible human impact on global climate Between the 2 reports - Scientific consensus shifted understanding - Initially - The greenhouse effect is well understood, greenhouse gases are increasing largely due to human activity and therefore should lead to significant global warming - Lack of scientific understanding and limited specific regional predictions - Afterwards - Greater understanding, despite continuing uncertainties that global warming continues and is most likely due to human activity IPCC 3rd assessment report in 2001 - Stated that human activities are modifying the concentrations of atmospheric constituents that absorb and scatter radiant energy - Most of the observed warming over the last 50 years is likely to have been due to an increase in greenhouse gas concentrations Systematic review of scientific literature revealed the scientific consensus → human-induced climate change through burning fossil fuels was being identified in the observational record Following the 3rd report → doubt and skepticism of the scientific consensus arose in the public - 1997 → only 48% of the US public thought that most scientists believe that global warming was occurring - 2001 → 61% of US public thought this - 2006 → 65%, but fell to 52% in 2010 - By 2021 → this figure rose to 68% - Measure of US public’s perception of the scientific consensus around climate change 1st attempt to determine level of scientific consensus in the published, peer-reviewed scientific literature → 2004, Naomi Oreskes - Found that in 928 papers published between 1993 and 2003 → no one rejected the scientific consensus - John Cook (2013) → found that 97.1% agreed with the scientific consensus that human induced climate change is real and happening - Disconnect between public perception of the level of consensus present among scientists studying climate change and the consensus among scientists themselves - Public perception was 64% in 2001 and 62% in 2013 Always possible that scientific consensus may be wrong - Further research can be done to better understand climate dynamics - Strong scientific consensus on human induced climate change - Doing nothing is not an option Convincing the scientific community How was the strong scientific consensus on human-induced climate change established - Is there evidence of global warming - Is this temperature rise unusual - Are greenhouse gases also increasing - Is it due to burning fossil fuels - Do we understand human induced climate change Is there evidence of global warming - We can observe global surface temperature records, but which one - Multiple datasets available → NASA and NOAA from US, and also UK and Japan - In general, the datasets agree but there are small differences - Datasets use 1951-1980 as the baseline for temperature change - Pairwise correlation of 99.04% → very strong correlation but imperfect - Why? → nature of sources of the data used in these constructions - Data used in these constructions collected at thousands of meteorological stations, buoys and ships around the globe - NASA tends to run slightly higher than the Japanese record while the UK and NOAA records are usually in the middle - Accurate measurement of air temperature across the entire planet is not simple → thousands of standardized weather stations spaced evenly across the globe is ideal but impossible due to large gaps over the oceans and polar regions Japanese record → leaves areas without plenty of weather stations out of the analysis so it covers 85% of the globe UK met office → similar approach, covers 86% of the globe NOAA → uses nearby stations to interpolate temperatures so it covers 93% of the globe NASA → interpolates aggressively and offers 99% coverage Homogenisation → correcting for differences in instruments and measurements Why is satellite data not used - Only goes back to 1979 → lack of historical data - Raw satellite data requires extensive homogenisation 1850-1900 is a suitable proxy - Earliest reliable instrumental records - Before significant impact of burning coal Observational temperature record → confirms that global temperatures are increasing - BDTK5 → have the claims been verified by someone else - Generally, all datasets agree that global average temperatures are increasing Science is open to testing and refinement, open and welcomes verification - Berkeley earth project (2010) founded by Richard Muller, climate change skeptic - Did not believe prior studies on global warming due to problems identified - Published findings in 2013 → found that global warming was real and the estimates of rate of warming were correct, and humans are almost entirely the cause Is this temperature rise unusual - Could the observed temperature rise be part of a long-term natural variation - Solution: extend the temperature record - IPCC 6th report → observed warming since 1850 is unprecedented in more than 2000 years Danger of extrapolating local data to global phenomenon - Medieval warm period lasting between 950-1250 - Little to no evidence → average global temperatures show no signal of the warming - Warm period was isolated to North Atlantic region and was not global - Areas such as tropical Pacific were colder than normal - Danger of relying on data from a limited region and extrapolating that data to infer a global phenomenon Proxy method - Sometimes it is necessary to study a variable which cannot be measured directly - Proxy method uses other variables correlated to variable of interest - Other variables with correlation are measured and used to infer the value of the variable of interest - Method used in constructing temperature records before modern times when direct measurements of temperature were available - Proxy records require calibration against independent temperature methods or against a more directly calibrated proxy Dendroclimatology - Most well known proxy method in temperature reconstructions - Width of tree rings used to determine past climate - Tree rings are wider when conditions favor growth and narrower when conditions do not favor growth - Ring width correlated with temperature - Calibrated with cross dating → easy to date tree rings Coral reefs - Add seasonal layers which appear as bands in the calcium carbonate shells - Can be used to date coral samples to an exact year and season similar to tree rings - Temperature is determined by measuring the composition of O2 isotopes present in the coral’s carbonate chemistry - Coral bands isotopes correlated with temperature Ice cores - One of the best available climate proxies - Provides fairly high resolution estimate of climate changes into the deep past - Ice core is a core sample that is typically removed from an ice sheet or high mountain glacier - Ice forms from the incremental build up of annual layers of snow → lower layers are older than upper layers - Ice core contains ice formed over a range of years → can reach depths of 3km and contain ice up to 800k years old - Temperature determined similarly to how it is determined in coral samples → composition of O2 found in the water itself - Glacial cycles caused by Milankovitch cycles → variations in eccentricity, axial tilt and precession that result in cyclical variations in the solar radiation reaching the Earth system - Shows that current temperatures have not been witnessed in the last 100k years - Vostok station ice core → reconstruct temperatures from 420000 years ago Natural temperature fluctuations take place over thousands of years - Recent global warming is far more rapid than has been seen in the last 800k years BDTK4 → where does the majority of the evidence point - All datasets point towards global warming being real BDTK3 → is the claimant providing positive evidence - Data from multiple sources provide positive evidence for unprecedented global warming - All the evidence that temperatures have risen is positive, reliable and relevant - Positive evidence supports a claim → opposed to negative evidence that seeks to discredit a rival claim - Climate change skeptics → like to introduce negative evidence to discredit scientific reports without providing evidence in support of their own claim Are greenhouse gases increasing concurrently - View observational records of greenhouse gases - Start with CO2 → important trace gas in Earth’s atmosphere Mauna Loa observatory in Hawaii → Keeling curve shows atmospheric CO2 concentrations rising - 315 ppm in 1958 to 415 ppm today - Seasonal variation → CO2 content falls during Northern Hemisphere summer - Photosynthesis surpasses respiration and decomposition - Rises during late autumn to early spring → respiration and decomposition of the previous season’s crop of leaves exceeds photosynthesis Connection between biosphere and atmosphere in the short term terrestrial carbon cycle Ice core record - CO2 and other gas concentrations can be determined from composition of air in bubbles trapped in the ice - Pre industrial revolution concentrations confirmed to be 280 ppm - Current CO2 concentrations have not been seen in at least the last 2 million years Similar records of other greenhouse gases have been on the rise - Methane → pre industrial value of 600 ppb to levels over 1800 ppb - Nitrous oxide → 270 ppb to 338 ppb Greenhouse gases have increased at an unprecedented level and rate since the industrial revolution - Current concentrations have not been witnessed in the last several hundred thousand years - Rapidity of these increases have never been seen in the record - Need to consider any necessary comparative information when making proper scientific observations Is the rise in atmospheric CO2 due to the burning of fossil fuels Carbon cycle - Carbon is a constituent of all organic compounds - Greatest physical reservoir of carbon → located in the Earth’s crust and inaccessible to biological organisms - Source of all carbon found in living organisms is CO2 → atmospheric or dissolved in H2O Global carbon cycle - Series of reservoirs of carbon in the Earth system which are connected by exchange fluxes of carbon - Exchange flux → amount of carbon which moves between reservoirs each year - Before human activities eg. land use changes and industrial processes had a significant impact → global carbon cycle was roughly balanced - CO2 increased by almost 50% from 280 ppm in 1750 to current level of 415 ppm 9 petagrams of additional fluxes of carbon arise from human activities annually - 5 petagrams is taken up by the land and the ocean annually - 4 petagrams are left in the atmosphere → explaining the rising atmospheric CO2 concentration - Scientists have been able to conclusively show that the increase in atmospheric CO2 is due to burning fossil fuels - Done through measuring the atmospheric concentrations of carbon-14 Carbon-14 - Isotope formed in the upper atmosphere through the impact of cosmic radiation - Oxidized to CO2 and incorporated into the biosphere through photosynthesis - Anything made of organic material will have carbon-14 present in its structure - Radioactive and has a half-life of 5730 years - Amount of carbon-14 as a function of time in the past → can use measurements of carbon-14 to date materials → basis of carbon dating Hans Suess realized that burning fossil fuels dilutes the amount of atmospheric carbon-14 present - Fossil fuels are devoid of carbon-14 as they are formed from the fossilized remains of animal and plant life that died millions of years ago (carboniferous period) - Any carbon-14 present in the organic material of these dead animals and plants would have decayed - Burning fossil fuels increases amount of carbon-12 in the atmosphere - Carbon-14 amount is unchanged → Suess effect: decrease in the C-14 to C-12 ratio - Influence of this dilution → affects accuracy of radiocarbon dating - Ratio of C-14 to C-12 has dropped dramatically since 1963 → mechanism is not radioactive decay but due to dilution through the burning of fossil fuels - Human-caused disruption to C-14 amount in atmosphere through the testing of nuclear weapons cited to mark the transition from Holocene to the current period → humans became a dominant force of global environmental change - Paul Crutzen (1995) → coined term anthropocene to denote the current period Do we understand human induced climate change - Science not only produced a vast amount of knowledge on a wide range of phenomena - It also enhanced our understanding of these phenomena - Understanding is one of the central aims of science → how do we scientifically understand something Scientists achieve understanding of phenomenon P if they construct an appropriate model of P on the basis of a theory T → Henk de Regt - Constructing models → helps scientists acquire understanding of phenomena - Climate science community has built such models → using relevant physical, chemical and biological theories - Mathematical models based on conceptual models have been built → computer based climate models - Describe how each part of the Earth system is interconnected - Aim → attempt to quantitatively explain the rise in temperatures witnessed since the industrial revolution CMIP6 → coupled model intercomparison project - Consists of simulations from 100 distinct climate models produced across 49 modeling groups - Simulated temperature response to both human and natural drivers, as well as natural drivers only - Found that human drivers causes a greater increase than natural drivers - Simulates the physics, chemistry and biology of the atmosphere, land and oceans in great detail - Average of all the model simulations closely follows the observed temperature record - Simulations excluding human influence show no warming across 1850 to present day - Simulations argue that it is impossible to reproduce the observed warming in global surface temperatures without including the increase in greenhouse gases due to the burning of fossil fuels Simulations follow observe explain test → scientists attempting to determine whether the observed increase was due to natural variability - Observed temperatures are rising - Explain → caused by natural variations - Test → put natural variations into the model - Evidence to support that the increase was due to natural variability does not exist - Result from test → explanation was wrong and need new hypothesis - Hypotheses ought to be falsifiable New observe explain test - Observed temperatures are rising - Explain → caused by humans - Test → put natural variations and greenhouse gases into the model - Result from test → explanation consistent with observation New instruments can lead to new discoveries - Invention of the computer → most important instrument in climate science - First attempt at performing a meteorological forecast through computation → Lewis Fry Richardson in 1922 - Forecast took months to calculate by hand and full of errors → was not repeated for 30 years - Without computers → projections would be tedious and erroneous - We would not be able to project the effects of climate change → simply not possible to couple together all of the different parts of the Earth system or even understand isolated elements of the Earth system Week 7 Why did the public doubt the scientific consensus Affirmation without action - Bush signed United Nations framework convention on climate change at Earth summit (Rio de Janeiro 1992) - Concrete action to protect planet → no binding targets or timetables - Treaty lacked binding targets and timetable for emission reductions John Sununu (PhD mechanical engineering MIT) → no training in climate science → fallacy of appeal to authority - Felt qualified to pass judgment on Hansen’s work - Criticized Hansen’s work as “technical poppycock” despite having no relevant expertise - Hansen → submitted report to White House as per protocol → global warming cause heat waves and other extreme events such as floods - Sununu → heavily edited Hansen’s testimony leaving it “meaningless” - Efforts to oppose climate change at the expense of economic growth increasing - Sununu instrumental in sabotaging the first attempt by international community to produce treaty to limit carbon emissions Nov 1989 (Noordwijk Declaration) → discuss framework for global treaty on greenhouse gas emissions - Sununu appointed climate change skeptic to US negotiating team - Given orders to prevent any US commitment - No agreement forged Sununu 2018 → leaders of the world at that time looking at how to seem like they were supporting the policy without having to make hard commitments that would cost their nations serious resources Questioning authority of a source - Qualifications and expertise of source Fallacy of appeal to authority - When said authority is not a subject matter expert - Climate change deniers use authority to promote their own agenda - Scientific consensus formed by community of experts - BDTK → how reliable is the source of the claim → Sununu leverage his phd in mechanical engineering to argue his case when he is not a climate science expert 1980-1990 → growing disconnect between rhetoric and action Rise of the doubt mongers George C. Marshall Institute (1984) → focus on science and public policy - Nonprofit conservative think tank established by renowned scientists - Robert Jastrow, William Nierenberg, Frederick Seitz - Defend strategic defense initiative Opponents to strategic defense initiative → Carl Sagan and Hans Bethe Marshall Institute → demanded equal air-time on news media to confront opposition (3 scientists against 6500 scientists and engineers) → threatened to sue if not met - Appearance that debate around the initiative was waged by sides of similar size - Proved important when the debate turned to climate change Marshall Institute needed new enemy in 1989 (collapse of Berlin wall) - New enemy → environmental extremism - Environmentalism → socialism - Issues of concern to environmentalists → acid rain, ozone hole, DDT - Require government intervention - Antithesis of free market - Popular neo-liberalism denounced such intervention - Regulation loss of freedom → give up economic freedom by allowing government to regulate the market → matter of time before other freedoms is lost Not just environmental issues which caused Marshall institute’s opposition to regulation 1950 → tobacco industry launched strategy that refuted and ridiculed science linking smoking to health issues and lung cancer - Seitz hired in 1979 by RJ Reynolds tobacco company to head their medical research committee - Learnt many ways of doubt mongering which was later useful in his contrarian efforts to cast doubt on the science of climate change Marshall institute against regulating 2nd hand smoke → joined by Fred Singer - Environmental physicist - 1994 → wrote report criticizing environmental protection agency’s study on cancer risks of 2nd hand smoke - Called the study “junk science” - “If government’s role in regulating dangers is not carefully delineated → essentially no limit to how much government can ultimately control lives” - Anti-environmental contrarianism of Marshall institute was driven by political agenda to thwart government regulation Cast doubt on environment science - CFCs and ozone layer → argued CFCs not responsible for ozone loss in stratosphere - Wrote papers questioning link between UVB and skin melanoma - Argued SO2 emissions released by coal-fired power plants not responsible for acid rain → blamed it on volcanic emissions - Global warming caused by natural variations in solar radiation → any warming caused by greenhouse emissions swamped by natural climate variations - Claimed no scientific consensus → benefits to increased CO2 in the atmosphere through higher agricultural productivity Merchants of doubt → recognized peddling doubt in science and scientific consensus was essential - Singer used credentials as environmental physicist → promote contrarian view on climate change, argue no consensus existed regarding human induced climate change - 2003 letter to financial times → wrote “no convincing evidence that global climate is actually warming” - 2007 → polemical documentary film “great global warming swindle” released on national television by promoters of contrarian position - Singer appeared in the film denying scientific consensus about the reality and causes of climate change - Critics argued the film misused and fabricated data, relied on outdated research, employed misleading arguments and misrepresented IPCC’s position - Damage was done even after the UK broadcasting regulatory agency upheld complaints of misrepresentation Public trust in science and scientific consensus around climate change was being damaged - Political rhetoric changing - Frank Luntz (political and communications consultant) in 2002 → wrote letter in white house stated “scientific debate closing but not yet closed, still a window of opportunity to challenge the science” - Voters believe no consensus about global warming within scientific community - Need to continue making lack of scientific certainty a primary issue in the debate - Defer to scientists and other experts in the field - Approach outlined → encapsulates history and continuing approach of those peddling contrarian position inside and outside of politics - Significant fraction of public accepts denier’s allegations as true or confused by them → do not know what to think or who to trust - Science effectively undermined → eroded public support for decisive action needed to avoid worst effects of global warming Intent to confound and mislead public on climate change - Political lobbyists able to mainstream contrarian positions to exploit uncertainty and monger doubt - Malicious and not genuine attempt to critically review the issue of controversy Reveals source’s perspective - BDTK 2 → what is the source’s perspective - Confound public, contrarian view, political agenda Why did the public doubt the scientific consensus - Vested interests of fossil fuel industry - Doubt mongering by political lobbyists and contrarian scientists → deeply damaged prospects of action - Advent of internet in 1990s and 24/7 news cycle, pervasiveness of social media → deeply divided opinion on this topic - Political lobbyists able to use the new technology to mainstream contrarian positions Applying BDTK on climate change myths Climate has changed before - Quadrant, July 2009 → Richard Lindzen wrote article “Resisting climate hysteria” - Wrote “climate is always changing, have had ice ages and warmer periods” - Ice ages occur in a 100k cycle for the last 700k years, have been previous periods that appear to be warmer than present despite lower CO2 levels - More recently → medieval warm period and little ice age Reliability of the claim → Richard Lindzen - Professor of meteorology at MIT - Lead author of IPCC’s 3rd assessment report - Credible claimant with highly valued expertise in climate science - We should pay attention to what he has to say Source’s perspective → contrarian - Long standing relationship with Cato institute - Founded by Koch brothers whose wealth derived largely from oil and natural gas - Actively sought to limit climate change legislation - Conflict of interest Positive evidence → relies on primary literature - Comes from peer-reviewed journals eg. Science and Nature - Measure of quality → journal’s impact factor (IF) - Not published in a predatory journal - Check whether evidence that underpins his argument is both reliable and relevant - Lindzen references articles that back his claim → providing positive evidence - References Tsonis et al. (2007) → claiming that variability seen in Earth system is enough to account for all climate change since 19th century Where does the majority of evidence point - Unknown if google directs us to authoritative website - Check IPCC reports → thousands of pages, require expert knowledge to understand the arguments - AI → CGPT can hallucinate and give out misinformation - Wikipedia → google “wikipedia climate has always changed” - Wikipedia’s page on climate variability and change - Highlights that climate has always been changing - Recent climate change cannot be explained by natural variation - Further links to other pages that attributes recent climate change - Scientific consensus at odds with claim made by Richard Lindzen → natural change happened on time scales of millions of years - Current rise in global temperature is unprecedented Have the claims been verified by someone else - Theory predicts upper troposphere (atmospheric layer) to warm faster than the surface - Lindzen cited 2 papers against this - Argued lack of observational confirmation indicates that observed warming at the surface not due to increased CO2 - 2 papers cited → 1 by Lindzen himself (inherent bias) and the other by David Douglass - Douglass paper co authored by Fred Singer - Verify conclusion of the papers → papers that cite the Douglass paper - Allen & Sherwood (2008) → explained non climatic biases found in direct temperature observations from radiosonde and satellite data - Analysis using thermal wind shear calculations reproduced expected warming trend in the upper atmosphere - Lindzen only selected papers that support his position → cherry picking Does the claimant use flawed reasoning - Cherry picked articles that agree with his view - Misrepresents state of literature on atmospheric temperature → did not share with reader that there was great deal of concern within climate science community about reliability of direct measurements in upper troposphere - Straw man fallacy → misrepresents a position that is easier to defeat than the opponent’s real argument - Disingenuous to suggest that there was no uncertainty in the temperature measurements in the tropical troposphere - Claimed current climate change is natural because past climate changed naturally (single cause fallacy) → assumes because climate changed from natural causes before, can only be changing from natural causes now Single cause fallacy → phenomenon falsely attributed to single cause when there may be multiple causes BDTK → climate has changed before - Highlights red flags around source’s perspective, verification and reasoning - Suggest caution → should not accept the conclusions in the article before investigating further It’s due to the sun BBC article 2004 → sunspots reaching 1000-year high - Written by David Whitehouse - Reports that over the past few hundred years, there has been a steady increase in the numbers of sunspots - At the time when the Earth was getting warmer - Suggests solar activity influences the global climate causing global warming Reliability of the claim → David Whitehouse (profile on desmog.com) - Phd in astrophysics → not in climate science - In the article → Whitehouse did not claim to be writing the article as a climate scientist - Claimed the role of science correspondent → responsibility to report faithfully the science behind the article - Appears to faithfully report the science - Science came from paper published in Nature by Solanki → technical - Does not appear to be any significant misrepresentation on the part of Whitehouse - Caveat → elements that appear to be opinions that Whitehouse has drawn from his read of the paper - Article may contain his own opinions Source’s perspective → many articles by Whitehouse take contrarian position on climate change - Whitehouse holds position on academic advisory council on contrarian global warming policy foundation - Would have had the autonomy to report the stories he wanted to, regardless of whether his editor exerts editorial rigor - Career since BBC → suggests we should have concerns over whether the selection of stories was the result of acknowledged importance in science or due to personal bias Positive evidence → reports evidence presented in work published by Solanki - Reports that over the past few hundred years, there has been a steady increase in the numbers of sunspots at the time when Earth was getting warmer - Changing solar activity influencing in some way the global climate causing the world to get warmer - 1st statement acknowledges correlation but implies causation given the context - 2nd statement explicitly makes case for causation → does not explain how - Not how science works → claim of causation requires theory and explanation that makes testable predictions False cause fallacy → assuming correlation implies causation Evidence that these statements are Whitehouse’s own opinion - Solanki wrote → although rarity of current episode of high average sunspot numbers may indicate that the Sun contributed to the unusual climate change during the 20th century, pointed out that solar variability is unlikely to be dominant cause of strong warming over past 3 decades - Solanki believes current work insufficient to make the statements the BBC article made - Providing positive evidence to support his claim → there is reason to believe this evidence is not being faithfully reported, misrepresenting conclusion of the paper Where does the majority of evidence point - Claim that sun is responsible for global warming is wrong - Google solar activity vs temperature → NASA’s climate change figure - Shows that in the last 40 years of global warming → Sun has shown slight cooling trend - Correlation evident in 1880-1980 is gone - Stated in IPCC’s executive summaries → intended to be read and understood by non-experts Have the claims been verified by someone else - Article does not coordinate any other work that argues for its conclusions - Conclusion inconsistent with the scientific consensus Does the claimant use flawed reasoning - Inconsistency between conclusions made in the article and that made in the underlying research paper - Cherry picking → paper used to argue for Whitehouse’s opinion - Attempt to cover himself → acknowledge consensus opinion that observed temperature rise due to rising concentrations of CO2 - Point only made in penultimate paragraph → many readers would have taken the statements made earlier as the conclusions and current state of scientific knowledge and would not have read the article to the end - Argued correlation is causation → false cause fallacy, did not refer to the causal mechanism as he knows that measured changes in solar output cannot explain magnitude of temperature increase - Cherry picking data that supports his claims → incomplete data fallacy, ignores data from last 40 years showing correlation present in previous century is now absent - Ignoring data from last few decades showing result where solar and climate data are non correlated BDTK → due to the sun - Skeptical of the conclusions drawn in the article - Not take the article at face value - Access underlying research and laterally read reports that present scientific consensus Challenge to scientific consensus on global warming Article written in 2007 by Hudson Institute - Claimed that animals and plants can adapt to climate change → wrote that corals, trees, birds, mammals and insects are adapting well to the routine reality of changing climate Reliability of the claim → Hudson Institute does not discuss climate change specifically as an area of interest - No fellows on staff are experts in climate science - Unclear who wrote the article - Names Dennis Avery (senior fellow of institute) and names Fred Singer as source of claims made Source’s perspective → avowed climate change deniers - Article puff piece → promote Avery and Singer’s book “unstoppable global warming every 1.5k years” - Book reviewed by institute of which he is a fellow → suggests conflict of interest Positive evidence → does not identify evidence which the claims is based on - Claims the evidence exists and is published in journals eg. Science and Nature - Requires readers to find the evidence rather than providing it → red flag Where does the majority of evidence point - Google scholar → reveals wealth of scientific evidence that counters the position made in the article - Research paper published in Science → estimates plants and animals dying at a rat 100-1000 times faster than the average rate of extinction over geological timescales - Work published in Proceedings of National Academy of Sciences (PNAS) → identifies specific climatic changes causing extinction and processes which may help species to survive - Research explaining why climate change causes extinctions → published in Proceedings of Royal Society B - Clear that majority of of evidence points to conclusions that human caused climate change is occurring too rapidly for plant and animal species to adapt Have the claims been verified by someone else - Quote from Singer → climate cycle has been moderate, trees, bears, birds and humans have quietly adapted - Absence of reputable sources agreeing - Wealth of research showing animal and plant life adapting, but not adapting well Does the claimant use flawed reasoning - Wholesale misrepresentation of scientific consensus - Straw man arguments used → misrepresents scientific consensus which is easier to counter eg. 70% of global warming occurred between 1850-1940 - Unsupported by global temperature record → 70% of global warming occurred since 1940 - Suggest medieval warm period was global phenomenon than regional affair → easier to argue that current temperature rises will not lead to widespread extinction as no such extinctions were seen in earlier warming BDTK → article is absolute nonsense - Every tool raises red flags Challenge for scientists → getting their message across to public - Graphical representations are a powerful medium - Global warming stripes (Ed Hawkins) and biodiversity stripes (Miles Richardson) → side by side show a 69% drop in global living planet index since 1970 has strong negative correlation with global average temperatures The Earth is cooling 2009 article published by Henrik Svensmark in website Watts Up With That - Wrote “global warming has stopped and cooling is beginning, no climate model has predicted cooling of Earth, means projections of future climate are unreliable” Reliability of the claim - Svensmark → physicist at center for sun climate research with the Danish National Space Institute - Working and publishing research in the area of climate change throughout his career - Should be considered an expert on this subject Source’s perspective - Little evidence that Svensmark is climate change denier or disputed role of greenhouse gases in global warming - Skeptical of extent to which increases in greenhouse gases have influenced the observed increase in surface temperatures - Website which the article is published in is skeptical of climate change Positive evidence - Stating global warming has stopped and cooling is beginning - Claimed sun is going through quiescent phase with implication that the sun is playing dominant role in determining Earth’s surface temperatures - Points to his own published and peer reviewed research indicating importance of cosmic rays on nucleating cloud droplet formation → publications in physical review letters and Proceedings of Royal Society A Where does the majority of evidence point - Cherry picking only air temperature as indicator of global warming when there are many other indicators → disingenuous - Key indicators of global warming moving in direction expected of a warming globe Have the claims been verified by someone else - Does not point to the research of others and does little to counter any arguments opposed to his position - Claimed that the cooling will continue through next 10-20 years → claim did not withstand scrutiny of the following 5 years since publication Does the claimant use flawed reasoning - Website’s climate change denial perspective → cherry picking articles that support its stand - Concerning that author does not address the counter evidence to his position - Points to his research as evidence → lack of support for his position in the science community - Engaging in black or white thinking → asserts temperature rise is mainly due to solar activity - Ignores other sources of temperature decline, selects time periods that agree with his argument BDTK → the Earth is cooling - Claims made are wrong - Perspective of the forum is a red flag - Reasoning used in article was concerning and check on the claims revealed that significant counterpoints were being ignored Global warming stopping is often raised in the light of recent weather events eg. big snowfall or drought-breaking rain - Just weather phenomena, global warming is entirely compatible with such events - Weather → conditions in one location at one time - Climate → conditions in one region over a long time - Cherry picking time window of global temperatures → allows for finding of contrarian trends Climate scientists do not rely on any one indicator to claim that global warming is happening → rely on the preponderance of evidence from many different indicators Climate change is not due to humans Article published in Houston Chronicle in 2010 → written by Neil Frank - Writes in polemical style - What do skeptics believe - Concur with believers that Earth has been warming since the end of a little ice age around 1850 - Cause of the warming is the question - Believers think the warming is man-made while skeptics believe the warming is natural and contributions from man are minimal Reliability of the claim - Frank → meteorologist with phd in meteorology - Director of US National Hurricane Center 1974-1987 - Expertise to write on subject of climate change Source’s perspective → skeptic - Author is a climate change skeptic → based on religious belief that Earth and its ecosystems are robust, resilient, self regulating and self correcting - Change is anathema to this belief - Signatory → Evangelical declaration on global warming Positive evidence - Makes 3 claims - Claims without evidence that cause of global warming since 1850 is natural with minimal contributions from humans - States that CO2 is not a pollutant but vital for plant life → argues that contribution to global warming from CO2 is minor compared to that of H2O - Arguing without evidence that CO2 is good and any attempts on reducing temperatures should focus on H2O instead - Claims without evidence that climate models are grossly over predicting future warming from rising CO2 concentrations Where does the majority of evidence point - Scientific consensus is that climate change is human induced - Climate change skeptics use carbon fertilization effect to argue that increased CO2 is a good thing as more CO2 is better for plants → in reality, climate change will have a complicated effect on plant growth - Increased temperature, reduced moisture content in soils, water stress → reduced plant growth despite higher CO2 levels Have the claims been verified by someone else - Does not provide citations to support his assertions - Onus is on claimant to provide evidence - Claimant does not provide breadcrumbs to point to potential sources of evidence → red flag Does the claimant use flawed reasoning - Polemical style of article - Calls the climate scientists identifying dangers of climate change “alarmists” - Argues that emails reveal conspiracy between US and UK climate scientists to adjust the data to make it look as if global warming is real - Language → red flag - Absence of evidence → ad hominem attack (targeting people rather than the argument) - Straw man argument → CO2 is vital to plant growth - False equivalence fallacy → comparing weather forecasts to climate modeling - Appeal to inappropriate authority → identifying non-experts in the field BDTK → climate change not due to humans - Ignore the article despite expertise of author - Ad hominem attack on climate scientists instead of a reasoned argument that global warming is natural Satellites measuring less IR radiation escaping to space at the wavelengths which CO2 absorbs Surface measurements reveal the radiation is returning to Earth to warm the surface Attribution of climate change to human activity - Not based solely on computer modeling - Empirical measurements eg. nights warming faster than days point to the conclusion that humans are causing the planet to warm Bias and denial - Disconnect between public perception and science - Climate change myths used to cast doubt Why do individuals doubt climate change - Fossil fuel industry, political lobbyists, media have spent 30 years casting doubt on reality of climate change - World’s 5 largest publicly owned oil and gas companies alone spend about 200 million USD a year on lobbying to control, delay or block binding climate policy How do they convince the public - Science denial → there is no consensus and climate change is just part of the natural cycle - Economic denial → climate change is too expensive to fix - Self fulfilling prophecy → economists estimate that climate change can be fixed now by spending 1% of world GDP - If delayed to 2050 → could cost over 20% of world GDP - Recognizes the need for intergenerational equity - Humanitarian denial → climate change is good for us, warmer summers make farming more productive and plants need CO2 - Pernicious → considers effect on people living in temperate climates and not those living in tropical climates - Untrue, but points to need for international equity - Political denial → others need to act first - Cannot take action as other countries are not taking action - Ignores historical legacy of greenhouse gas emissions - Highlights need to recognize ethical responsibility of developed nations to take action first - Crisis denial → it is still uncertain - Should not rush into committing to binding international agreements given the uncertainty raised by previous areas of denial Why do individuals accept these forms of denial - Susceptible to cognitive bias - Recognizing this bias is key to thinking critically Time discounting bias - Discount future to a greater degree than can be rationally defended - Over focus on short term considerations - Over discounting the future → contribute to broad array of environmental problems - Overharvesting of oceans and forests - Failure to invest in new technologies to address climate change - Most likely to discount future when it is uncertain, distant, and when intergenerational distribution of resources is involved - When people view that Earth’s resources should be preserved → tend to think about their descendants - However when consumptive opportunities arise today which inflict environmental costs on future generations → begin to view “descendants” as a vague group of people living in a distant time - Overweighting present concerns → viewed as foolish and immoral - Robs future generations of opportunities and