Why Does CO2 Affect Our Climate?
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Our atmosphere is 76% nitrogen, 21% oxygen, and 3% trace gases, which include the greenhouse gases carbon dioxide (CO2) and water. Carbon dioxide has a large infrared absorption at 16 microns, the maximum of the blackbody radiation spectrum of our atmosphere. Carbon dioxide thus absorbs heat radiation and re-emits it back to the surface of our earth to keep it warm. Water vapor increases with temperature amplifying this greenhouse effect. Non-condensing CO2 provides the stable temperature structure that sustains atmospheric water vapor and clouds (1). When the earth’s orbit and tilt triggered a cooling trend 110,000 years ago, CO2 decreased and water condensed and froze, plunging the earth into an ice age. About 18,000 years ago, orbital changes warmed the oceans which emitted dissolved CO2 gas. This greenhouse forcing warmed the earth and melted the ice. Reference: (1) Andrew A. Lacis, et. al. “Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature.” Science, 330, 356-359, 15 October 2010
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Why Does CO2 Affect Our Climate?
- 1. Why does C02, 0.04% of our atmosphere, affect our climate? Paul H. Carr AF Research Laboratory Emeritus www.MirrorOfNature.org
- 2. Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature This talk was inspired by my conversation with Peter Somssich about trace gases in automotive light bulbs.
- 3. Increasing CO2 gas density: 1. raises temperature of earth’s surface. 2. reduces temperature of the stratosphere.
- 4. -Outgoing spectral radiance at the top of Earth's atmosphere showing the absorption at specific frequencies and the principle absorber CO2 at 16 microns. -The red curve shows the flux from a classic "blackbody" at 294°K (≈31°C≈69.5°F). Schmidt, G.A., 2010 J. Geophys. Res.,115, D20106, doi:10.1029/2010JD014287.
- 5. CO2 levels now 110 ppm above the pre- industrial average 1875 • Carbon isotope ratios indicate the CO2 increase since 1850 is from burning ~300 million yr old fossil fuels.
- 6. 1750-2005: Even if the cloud albedo effect is assumed to have the maximum cooling value, there would still be a net warming of the climate due to human activities. (UN Intergovernmental Panel on Climate Change, IPCC, 2007Report) Solar Irradiance increased by only 0.2% since 1750.
- 7. The shadowing effect of clouds cools by preventing sunlight from warming the earth.
- 8. Runaway Greenhouse Effect on Venus Science, 330, 356-359, 15 October 2010 Parameter Mars Earth Venus Ts (K) 215 288 730 Tơ s exp4 (W/m2) 121 390 16,100 PS (bar) 0.01 1 100 Ultraviolet observations of VENUS’ cloud cover---- Venus surface temp hotter than Mercury’s 693K. Venus atmosphere is 96% CO2, 3% Nitrogen.
- 9. Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature Andrew A. Lacis,* Gavin A. Schmidt, David Rind, Reto A. Ruedy Science, 330, 356-359, 15 October 2010 http://pubs.giss.nasa.gov/docs/2010/2010_Lacis_etal.pdf Ample physical evidence shows that carbon dioxide (CO2) is the single most important climate-relevant greenhouse gas in Earth’s atmosphere. This is because CO2, like ozone, N2O, CH4, and chlorofluorocarbons, does not condense and precipitate from the atmosphere at current climate temperatures, whereas water vapor can and does. Noncondensing greenhouse gases, which account for 25% of the total terrestrial greenhouse effect, thus serve to provide the stable temperature structure that sustains the current levels of atmospheric water vapor and clouds via feedback processes that account for the remaining 75% of the greenhouse effect. Without the radiative forcing supplied by CO2 and the other noncondensing greenhouse gases, the terrestrial greenhouse would collapse, plunging the global climate into an icebound Earth state.
- 11. Time evolution of global surface temperature, top-of-atmosphere (TOA) net flux, column water vapor, planetary albedo, sea ice cover, and cloud cover, after zeroing out all the non-condensing greenhouse gases. The model used in the experiment is the GISS 2°×2.5° AR5 version of ModelE with the climatological (Q-flux) ocean energy transport and the 250 m mixed layer depth. The model initial conditions are for a pre-industrial atmosphere. Surface temperature and TOA net flux utilize the left- hand scale. Cooling from zeroing out all the noncondensing GHGs and aerosols. Below 0 C, water vapor becomes snow & ice
- 13. CarbonDioxide(ppm) 600 500 400 300 200 100 present Time (thousand years ago) 300 280 260 240 220 200 180 160 Science, Vol. 310, p. 1313, Nov. 2005 Historical CO2 Concentration
- 14. Temperature CarbonDioxide(ppm) 600 500 400 300 200 100 present Time (thousand years ago) 300 280 260 240 220 200 180 160 Science, Vol. 310, p. 1313, Nov. 2005 400 -Present Levels of Carbon Dioxide are Higher - 400 CO2 decrease from 300 to 200 ppm, 100,000 years ago, helped drive temperature down 3.5 C into an ice age. Ice Age
- 15. During the steepest warming, the CO2 released (dots) from the sea preceded the global temperature rise (green line) by several centuries. -CO2 RATE OF CHANGE is 1/300 of the PRESENT RISE. -CO2 greenhouse effect drove the 3.5 C increase in average global temperature. -Sea levels rose ~ 100 meters. Flood stories 4 M PEOPLE 7 B Ice Age Nature, 484, 49-54 (05 Apr 2012) CHANGES IN THE EARTH’S TILT & ORBIT TRIGGERD THE ICE AGE WARMING
- 16. • C02 CONCENTRATION IN THE INDUSTRIALIZED NORTHERN HEMISPHERE IS GREATER THAN THE SOUTHERN. • TEMP. INCREASE, SINCE 1880, OF NORTHERN = 1.1 deg. C • TEMP. INCREASE OF SOUTHERN HEMISPHERE = 0.4 deg C HUMAN CO2 FOOTPRINT Atmospheric Infrared Sounder (AIRS) Aboard NASA’s Aquilla Satellite.
- 17. At present rate of 2.5 ppm rise per year, humans are increasing CO2 at a rate 300 times faster than the recovery from the ice age 18,000 -10,000 years ago. CO2 CONCENTRATIONS, HIGHEST (33%) IN 800,000 YRS, WILL REACH 1000 PPM IN 240 YEARS.
- 18. • Our present level of 400 ppm could reach ~ 1000 ppm by 2100. • Arctic became ice-free 8 M years ago when CO2 = 300 - 450 ppm. • Antarctic melted ~ 40 M years ago, CO2 ~ 700 ppm -Earth was ice-free, sea levels 100s meters higher. Dinosaur Extinction 65M Yr. BP Figure from Dr. James Hansen, NASA GISS
- 19. Continental ice sheets grew when CO2 was low, 300 and 40 million years ago.
- 21. Atmospheric CO2 is the Principal Control Knob Governing Earth’s Temperature: 1.Resonant absorption at 16 microns. 2. Lifetime of at least 100 years.
- 22. Why does C02, 0.04% of our atmosphere, affect our climate? Paul H. Carr AF Research Laboratory Emeritus www.MirrorOfNature.org
Notes de l'éditeur
- Scientific study of sedimentary rocks suggests the Earth's atmosphere in ancient times had considerably more CO2 than today. Current CO2 % is similar to a similar lull, 300 million years ago. Note that CO2 was at least 20 fold higher and the temperature was seven degrees C hotter than it is now. Note too that there has been no tipping point as presumably occurred on the planet Venus. From a long-term perspective, Atmospheric CO2 is now VERY LOW.