Why does C02, 0.04% of our
atmosphere, affect our
climate?
Paul H. Carr
AF Research Laboratory Emeritus
www.MirrorOfNature.org

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.

Increasing CO2 gas density: 1. raises temperature of earth’s surface.
2. reduces temperature of the stratosphere.

-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.

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.

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.

The shadowing effect of clouds cools by
preventing sunlight from warming the earth.

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.

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.

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

Temperature
600 500 400 300 200 100 present
Time (thousand years ago)
Science, Vol. 310, p. 1313, Nov. 2005
Historical Temperature
Ice
Age

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

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

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

• 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.

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.

• 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

Continental ice sheets grew when CO2 was low, 300 and 40 million years ago.

Atmospheric CO2 is the Principal Control
Knob Governing Earth’s Temperature:
1.Resonant absorption at 16 microns.
2. Lifetime of at least 100 years.

Why does C02, 0.04% of our
atmosphere, affect our
climate?
Paul H. Carr
AF Research Laboratory Emeritus
www.MirrorOfNature.org