Greenhouse Gases: Carbon Dioxide PDF

Greenhouse gases: Carbon Dioxide ATMO 310/ OCN 310 September 16, 2024  Distribution of Carbon on Earth The deep and surface C reservoirs are not completely separate…… Deep C reservoirs: mantle and crust Surface C reser...

Greenhouse gases: Carbon Dioxide ATMO 310/ OCN 310 September 16, 2024  Distribution of Carbon on Earth The deep and surface C reservoirs are not completely separate…… Deep C reservoirs: mantle and crust Surface C reservoirs Atmosphere, oceans, land Volcanic degassing Metamorphic degassing Rock weathering Subduction or deep burial of carbonates and organic C Pre-industrial values https://www.sciencenews.org/article/where-earth-stores-its-carbon Source : Suarez et al (2019). doi: 10.2138/gselements.15.5.301. Global Carbon Cycle- anthropogenic influence  Anthropogenic CO2 emissions 2010-2019 Burning fossil fuels 9.4 ± 0.5 Pg C yr-1 (~85%) Land-use change 1.6 ± 0.7 Pg C yr-1 (~15%) Total C released since 1750: 700 ± 75 Pg C Friedlingstein et al. (2020). Earth Syst. Sci. Data, 12, 3269–3340 https://doi.org/10.5194/essd-12-3269-2020  Anthropogenic CO2 emissions Total C released since 1750: 700 ± 75Pg C 46 % 31 % 23 % Friedlingstein et al. (2020)  Seasonal fluctuations in atmospheric CO2 driven by land vegetation https://www.youtube.com/watch?v=x1SgmFa0r04  World’s forests net change growth loss The world’s forest area is decreasing, but the rate of loss has slowed (due to reduction in deforestation in some countries and forest expansions in others) Source: FAO. 2020. Global Forests Resources Assessment Earth’s Mean Energy Budget The Earth’s energy budget and climate change Since at least 1970, there has been a persistent imbalance in the energy flow that has led to excess energy being absorbed by different components of the climate system  T/F: Incoming radiation is characterized by short wavelengths and outgoing radiation is characterized by long wavelengths.  Energy balance summary Earth receives shortwave radiation from the sun, ~30% is reflected back into space (albedo), the remaining is absorbed by the atmosphere and the Earth’s surface Earth absorbs energy from the sun as well as energy re-emitted back towards the Earth by greenhouse gases Earth radiates long wave radiation to balance the energy inflow Greenhouse gases absorb and re-emit long-wave energy emitted by the Earth, warming the planet With no greenhouse gases the temperature of the planet would be -18 C or 0 F Due to the increase in greenhouse gases the planet is currently out of balance, with energy inflow exceeding outflow  Composition of Earth's atmosphere Composition of Earth’s atmosphere The major constituents in our excluding water vapor atmosphere: N2, O2, and Ar are NOT greenhouse gases Greenhouse gases absorb and emit radiation within the thermal IR range Most important greenhouse gases: Water vapor (H2O) Carbon dioxide (CO2) Methane (CH4) Ozone (O3) Nitrous oxide (N2O) In addition to the gases, aerosols are also in the atmosphere and are important for Earth’s energy balance Changes in radiative forcing due to humans activities Effective radiative forcing =energy gained or lost by the Earth How long have we known about the greenhouse effect?  Discovery of the greenhouse effect In 1827 French mathematician Jean-Baptiste Joseph Fourier realized that the Earth would be much colder without an atmosphere Earth’s surface temperature is the balance between two energies: light from the sun and “dark heat” (infrared radiation) Photo credits: Wikipedia  Discovery of the greenhouse gases In 1859 Irish physicist John Tyndall discovered that carbon dioxide and water vapor had the ability to absorb infrared radiation He speculated that the Earth would be much colder in the absence of these gases in the atmosphere Tyndall’s invented radio spectrophotometer to measure the absorbance of infrared radiation by different gases Photo credits: Wikipedia Impacts of atmospheric CO2 on climate In 1896, Swedish scientist Svante Arrhenius followed Tyndall’s work and predicted (after one year of by-hand calculations!) the impact of CO2 on global temperature He was interested on whether changes in atmospheric CO2 could trigger ice ages He was awarded the Nobel Prize in Chemistry in Photo credit: Wiikipedia 1903 for his electrolytic theory of dissociation Arrhenius equation Doubling of atmospheric CO2 would F =  ln (C/C0) increase global temperatures by 5-6 C  Trends in atmospheric CO2 In 1958 Charles David Keeling started The “Keeling Curve” monitoring the concentration of CO2 in the atmosphere He was the first to report seasonal fluctuations in atmospheric CO2 as well as the rise of atmospheric CO2 due to human activities The “Keeling Curve” has become an icon symbolizing the impact of humans on Earth https://www.youtube.com/watch?v=dXBzFNEwoj8 Trends in atmospheric CO2 Gruber&Sarmiento (2002) Mauna Loa Observatory  Carbon dioxide and temperature Consistent higher and lower CO 2 concentrations during warms and cold intervals of the past, respectively In this 800k record, CO2 is never higher than ~300 ppm Parrenin et al. 2013; Snyder et al. 2016; Bereiter et al. 2015.  Glacial-Interglacial CO2 records “Multiple lines of evidence show that the rate at which CO2 has increased in the atmosphere during 1900–2019 is at least 10 times faster than at any other time during the last 800,000 years (high confidence), and 4–5 times faster than during the last 56 million years (low confidence). How do we know that the growth in atmospheric CO2 is caused by humans ?  Lines of evidence 1. Difference between the Northern and Southern hemisphere 2. Carbon isotopes of atmospheric CO2 3. Trends in atmospheric O2 “ These three lines of evidence confirm unambiguously that the atmospheric increase of CO2 is due to an oxidative process (i.e., combustion)“  1, Differences between the Northern and Southern Hemisphere The difference between atmospheric CO2 records in the Northern (Mauna Loa) and Southern (South Pole) Hemisphere is caused primarily by the increase in emissions from fossil fuel combustion in industrialized regions, which are predominantly in the Northern Hemisphere 2. Stable isotopes of carbon in atmospheric CO2 Plants and algae prefer 12C over 13C Stable isotopes of carbon Plants and algae have lower 13C/12C relative to the atmosphere 12C → 98.9% of all carbon Fossil fuels are ancient organic material 13C → 1.1% of all carbon that used to be plants or algae, they are depleted in 13C Also deforestation returns carbon previously stored in plants (low 13C/12C) Higher 13C/12C Lower 13C/12C https://www.youtube.com/watch?v=b4QDokHJFIg  3. Trends in atmospheric O2 For every molecule of carbon burned from fossil fuels, 1.17- 1.98 molecules of O2 are consumed Declining trend in atmospheric O2 More O2 Less O2  How do we know that the growth in atmospheric CO2 is caused by humans ? 1. Difference between the Northern and Southern hemisphere 2. Carbon isotopes of atmospheric CO2 3. Trends in atmospheric O2  Summary The greenhouse effect: natural vs anthropogenic The ice core archive shows a tight coupling between temperature and carbon dioxide oscillations; natural variations in the past Both the current CO2 levels in the atmosphere and the rate of change are unprecedent for the past 800,000 years Three lines of evidence for anthropogenic change  Equilibrium climate sensitivity Equilibrium climate sensitivity measures how climate models respond to a doubling of atmospheric CO2 Arrhenius