1. Atmospheric Greenhouse Gas Levels

2. Estimated global warming potentials relative to CO2
(Warming effect = kilograms of CO2 per kilogram of gas)
Gas
Lifetime (years)
Warming effect for durations of:
20 years
100 years
Carbon Dioxide (CO2)
5 to 200a 1
Methane (CH4) 12 62 23
Nitrous Oxide (N2O)
114
275
296
Some halocarbons (produced only by humans)
HFC-23
260
9,400
12,000
HFC-125 29
5,900
3,400
HFC-134a
13.8
3,300
1,300
CF4
50,000
3,900
5,700
C2F6
10,000
8,000
11,900
SF6
3,200
22,200
32,400
a No single lifetime can be defined for CO2 due to different rates of uptake by different removal processes.
Note: The uncertainty in the global warming potentials is typically about 35%.

3. Global CO2 Budgets (billion metric tons/year)
Process
Atmospheric Increase
12.2 ± 0.37
11.73 ± 0.37
Fossil Fuel Emissions Increase
19.8 ± 1.1
23.1 ± 1.47
Ocean-atmosphere Uptake
−6.23 ± 2.2
−8.8 ± 2.57
Land-atmosphere Uptake
−1.47 ± 2.57
−2.57 ± 2.93
Land Use Change
7.33 ± 2.93
8.07 ± 2.93
Source: Joos, F., G-K. Plattner, T.F. Stocker, A. Kortzinger and D.R. Wallace. Trends in marine dissolved oxygen: Implications for ocean circulation changes and the carbon budget, EOS, 84, 197, 27 May 2003.

4. Atmospheric Residence Time for a Pulse of CO2
This graph shows the decay of a pulse of CO2 added to the atmosphere. In 100 years a third of the CO2 from that pulse is still in the atmosphere, and in 1000 years 19% still remains.

5. This thin-section of part of an ice core shows parts that are used to determine past climates and past abundances of atmospheric constituents.

6. Greenhouse Gases for the Past 650,000 Years
Greenhouse gas abundance is higher than anytime in at least the past 800,000 years from the latest measurements. Atmospheric carbon dioxide (red), methane (blue), and nitrous oxide (green) concentrations for the past 650,000 years derived from Antarctic ice cores and direct measurements. The bottom black curve is a temperature proxy from the cores. The shaded area is the present interglacial period, the Holocene. The rise in these greenhouse gases is unprecedented during the past 800,000 years. The steep rise began in about 1850, about 100 years after the start of the Industrial Revolution in From IPCC 4th Assessment 2007.

7. Analysis of air bubbles trapped in an Antarctic ice core extending back 800,000 years documents the Earth’s changing CO2 concentration. Over this long period natural factors have caused the atmospheric CO2 concentration to rary within a range of about 170 to 300 ppm. Temperature related data make clear that these variations have played a central role in determining the global climate. As a result of human activities, the present CO2 concentyration of about 385 ppm is ablut 30% above its highest level over at least the last 800,000 years. In the absence of strong control measures, emissions projected for this century would result in the CO2 concentration increasing to a level that is roughly 2 to 3 time the highest level occurring over the glacial-interglacial era that spans the last 800,000 years or more.

8. This graph shows the atmospheric concentration of CO2 from Ice core data, and measurements of the atmosphere from 1959 to The present interglacial period (Holocene) is indicated.

9. These graphs show the abundance of carbon dioxide, nitrous oxide, and methane over the past 1000 years. Also shown is the abundance of sulfate aerosols from 1400 to Aerosols cool the atmosphere. The rapid increase in greenhouse gases began about 1850, some 100 years after the start of the Industrial Revolution. It coincides with the rapid increase in industrialization and the rapid increase in the world population. From IPCC 3rd Assessment, 2001.

11. Measured Increase in CO2, Nitrous Oxide, Methane and CFC’s Since 1979
In the CO2 and methane curves the blue line is the monthly mean and the red line is the yearly mean. The sinuous nature of the monthly curve is due to seasonal variations in the emissions. Methane increased from 1625 ppb during 1984 to 1751 ppb during Since then it has remained nearly constant to This may be the result of about 10 million metric tons of decreased CH4 emissions above 50 N latitude in the early 1990’s due to a 30% decrease in fossil fuel burning in the former Soviet Union. This may have pushed the global methane abundance towards the present level concentration (Dlugokencky, et al., 2003). Also new methods of rice farming and methane capture from waste sites have also contributed to the stability. However, the present level may only be a temporary pause in the increase. Current releases from peatlands, permafrost and methane hydrates may reverse this trend. If fact this has already occurred. There has been a 0.5% increase in 2007 that is biogenic and probably due to the release of methane from melting permafrost and methane hydrates (See slide under Artic).

12. Methane Beginning to Increase After 8 Years of Stability
This graph shows the methane atmospheric abundance from 1990 through Beginning in 2007 the methane began to increase after 8 years of stability. Data from NOAA for the Baring Head Station.
From 1999 to 2006 (8 years) the methane abundance has been relatively stable due to industrial changes in Russia, changes in the methods of rice farming, and methane capture from landfill sites.
In 2007 the world methane abundance began to increase.
Based on carbon isotope analyses the methane is of biogenic origin.
The source is probably the release from melting permafrost, and the Siberian Arctic continental slope methane hydrates.
We may now be entering a non-linear climate response.

13. The rapid rise in atmospheric CO2 from direct systematic measurements begun on the Island of Hawaii in The rise is shown in this graph of the mean annual CO2 abundance, and is called the Keeling Curve.

14. The variation of the yearly rate of CO2 increase is shown on this graph. Also shown is the Pinatubo eruption in 1991 that cooled the climate resulting in more uptake of CO2, and the major El Nino event of 1998 the resulted in a larger release of CO2. The thick line is a linear fit to the data. There has been a rise in the average rate from about 0.8 ppm/yr in 1960 to a present average rate of about 2 ppm/yr. This rate continues to increase. (Source is National Oceanic and Atmospheric Adm.)