Climate Change Science: Lecture 5 Notes

The Science of Climate Change: Lecture 5 Study Notes

• Lecture aims to enable you to describe the history of understanding the atmosphere, discuss the greenhouse effect and gases, recount the discovery of oxygen, explain the greenhouse effect via radiation absorption, and estimate the greenhouse effect using a single-layer atmosphere model.

Epistemic Responsibility

• Scientific inquiry involves questioning, understanding, and building confidence in knowledge through methods like empiricism, rationalism, and scepticism.
• Empiricism uses evidence to propose hypotheses that explain natural causes.
• Hypotheses are tested sceptically with observations or experiments, and if predictions are fulfilled, corroborated hypotheses are used to construct logical theories.
• Rationalism and scepticism complement rational faculties, bolstering confidence in knowledge.
• A Faustian bargain considers science's role in environmental degradation, contrasted by Johann Wolfgang von Goethe's defence of science in literature.
• The course aims to unpack scientific inquiry within climate change, highlighting the responsibility to address this issue and understand its nature.
• The fossil fuel industry has undermined climate change science, offering examples of pseudoscientific thinking.
• Taking an anti-climate change stance is not only scientifically incorrect but also morally wrong due to the epistemic responsibility to base beliefs on sufficient evidence.
• It is important to justify beliefs with evidence, crucial for responsible scientific inquiry, in line with Professor Bettens' Baloney Detection Toolkit.

Sufficient Evidence

• William Kingdon Clifford and Thomas Henry Huxley posit citizens have a responsibility to base beliefs on sufficient and logically justified evidence.

Nature of the Atmosphere

• Scientific inquiry is illustrated through climate change, focusing on the increasing presence of carbon dioxide from burning fossil fuels.
• The atmosphere consists of approximately 78% nitrogen, 21% oxygen, and 1% argon, plus trace gases like carbon dioxide, methane, and nitrous oxide.
• Carbon dioxide is measured around 420 parts per million (ppm), methane at 1900 parts per billion (ppb), and nitrous oxide at 335 ppb.
• Empedocles of Agrigentum in ancient Greece proposed four universal elements: fire, air, water, and earth, further defined by Plato.
• Empedocles suggested these elements mix in proportions to form substances, combined by Love and separated by Strife, a cycle where elements are mixed then sorted.
• Love is recognized as an attractive force and strife as a repulsive force.
• Aristotle tested Empedocles' cosmogony by distilling seawater to separate salt, showing seawater as a compound.
• Leonardo da Vinci first suggested air is not completely consumed during combustion or respiration.
• John Mayow showed combustion and respiration use a part of air called spiritus nitroaereus.
• Jan Baptist van Helmont recognized reactions produce substances more subtle than vapours, naming vapours from burning charcoal as 'gas sylvestre' (carbon dioxide).
• Joseph Black discovered magnesium carbonate releases a 'fixed air' when heated that doesn't support life and confirmed its presence in exhaled breath.
• Stephen Hales suggested plants draw nourishment from air and Jan Ingenhousz identified this as carbon dioxide.
• Air is needed to sustain combustion and life.

Problem of Combustion

• Jean Rey found lead and tin gain weight when heated.
• Johann Joachim Becher and Georg Ernst Stahl established the phlogiston theory: combustible materials contain phlogiston that is released when burned.
• Johann Heinrich Pott then argued that air attracts phlogiston.
• Robert Boyle didn't see phlogiston's negative mass as a deal breaker.
• Robert Hooke, Ole Borch amongst others produced oxygen in experiments but failed to realize they created a new element.
• Michael Sendivogius described cibus vitae (food of life) in air.
• Cornelis Jacobszoon Drebbel purified a spiritous part of air for respiration and sustained 12 men in submarine down the Thames river.
• Carl Wilhelm Scheele produced oxygen by heating mercury oxide and nitrates, naming it 'fire-air'.
• Joseph Priestley liberated 'dephlogisticated air' by focusing sunlight on mercury oxide supported combustion and life.
• Antoine-Laurent Lavoisier claimed to have discovered oxygen independently and that gas was 'vital air'.
• Henry Cavendish noted that with air burnt, dew was formed.
• Lavoisier proved Cavendish wrong with regards to water, claiming water was not an element, but a compound of vital (oxygen) and inflammable (hydrogen) air.
• Priestley published findings.
• Lavoisier named inflammable air 'hydrogen' and vital air 'oxygen'.
• He stated that combustion always required only oxygen.
• He proved with Pierre-Simon de Laplace that respiration is combustion and that is law of conservation is based on the fact that when substances are burnt, the weight lost in the air, equals the substances weight gained.
• Many before Lavoisier were blinded by the phlogiston theory, not realizing it was wrong.
• On 8 May 1794, at the height of the Reign of Terror, the Revolutionary Tribunal tried, convicted, and beheaded Lavoisier.

A Question of Priority

• Scheele, Priestley, and Lavoisier are the most credited as discoverers of oxygen.
• Sendivogius should be credited with the discovery of oxygen for isolating it and linking it to the part of the atmosphere required for life.

Conclusion

• Discussion provides insight into the discovery of the atmosphere's nature and development of scientific inquiry/method.

Earth's Blanket

• Atmospheric carbon presence is critical for understanding how atmosphere warms Earth's surface.
• Jean-Baptiste Joseph Fourier discovered that the atmosphere plays a role in controlling the climate.
• He explained that the Earth must radiate although at wavelengths we cannot see, and he called this "radiant heat" (now infrared radiation).
• Something was missing relating to the understanding of the Earths temperature. In 1824 Fourier realized this something was the atmosphere.
• In 1824, Fourier posited that the atmosphere acts as an insulator preventing radiant heat from escaping to space.
• The term 'greenhouse effect' was coined by the Swedish meteorologist, Nils Gustaf Ekholm, around 1900.
• Fourier created a model to explain the Earth's surface temperature.
• John Tyndall studied how gases absorb radiation, which in his words, was “a perfectly unexplored field of inquiry".

John Tyndall

• In 1861, Tyndall realized the importance of water vapour in terrestrial radiation absorption.
• Carbon dioxide is 90 times more effective at absorbing radiation than air, methane 403 times more, and water vapour is 16,000 times more.
• Tyndall discovered gases like water vapor and carbon dioxide are opaque to radiant heat, helping to keep the planet warm.
• In opposition, Eunice Newton Foote demonstrated that air with gasses heated up in glass.
• Foote identified carbon dioxide as a greenhouse gas, noting its role in controlling Earth's surface temperature.

Understanding the Greenhouse Effect

• In the 1890s, Arvid Högbom compared industrial and natural carbon dioxide emissions and presented at a meeting.

Svante August Arhenius

• Svante August Arrhenius calculated that doubling atmospheric carbon dioxide would raise global temperatures by 5-6 °C.
• Arrhenius concluded with the other calculations, that Earth would warm, but such warming would take thousands of years.
• Guy Stewart Callendar demonstrated Earth's surface temperature increased in the previous 50 years.
• Charles David Keeling started collecting carbon dioxide samples at the Mauna Loa Observatory and produced data showing its levels were rising steadily - the 'Keeling Curve'.

It's Happening Now

• In 1965, U.S. President Lyndon B. Johnson's Science Advisory Committee warned of fossil fuel emissions harmful effects.
• They stated that, similarly to gasses in a greenhouse, they raised the earth's temperature.
• In 1981, James Hansen published a study saying that carbon dioxide warming should emerge from the noise level of natural variability by the end of the century
• In 1988, Hansen testified to the U.S. Congress that the warming trend was not a natural variation, but caused by carbon dioxide and other artificial gases.

On Metaphors

• 'Greenhouse effect' and 'global warming' aren't the same thing.
• The greenhouse effect is the process making Earth warmer.
• Global warming is increased greenhouse effect magnitude.
• Greenhouse gases absorb terrestrial radiation, but sulphate aerosols cool the planet.
• Greenhouses behave in exactly the same way as blankets, the glass inhibits convection and prevents the exchange of air between inside and outside.

A Correct Explanation

• The Earth's surface is warmer with an atmosphere that includes gasses because it receives energy from the Sun and the atmosphere.

Model Building

• Fourier recognized that the atmosphere warms the Earth.
• With measuring temperature as constant you can calculate the approximate Earth temperature and energy it receives over the course of the year.
• Josef Stefan deduced his relationship using data by Tyndall.
• They assumed their model was a black-body, meaning it wasn't literally black and the exact assumptions did not matter for the purposes of the experiment.
• Using calculations you can produce estimates of approximate Earth temperatures which match closely.

What Have You Learnt

• Revisit: The discoveries of da Vinci, Mayow, van Helmont, Black, Hales and Ingenhousz.
• Revisit: The development of Fourier's conception of heat flow.
• Revisit: The overturning of the phlogiston theory with the theory of combustion described by Lavoisier.
• Revisit: The absorption of radiation by gases in the atmosphere affects the Earth surface temperature.
• Revisit: Calculating the greenhouse effect.