ESRL Quarterly Newsletter - Summer 2009

Annual Greenhouse Gas Index 2008

New data show unrelenting rise in carbon dioxide and other greenhouse gases

Several factors associated with CO2 emissions.

Several factors associated with CO2 emissions, presented on a logarithmic scale. Anthropogenic CO2 refers to CO2 levels above pre-industrial. Adapted from Hofmann et al. 2008.

The climate-warming gases carbon dioxide and methane continued to increase in the atmosphere last year, despite the global economic slump and a decrease in activities that consume fossil fuels.

ESRL researchers released the annual greenhouse gas index in April, based on atmospheric data collected from 60 sites around the world. Researchers here measured an additional 16.2 billion tons of carbon dioxide (CO2)—a byproduct of fossil fuel burning—at the end of 2008, compared with 2007’s yearend- figures. There were also an additional 12.2 million tons of the potent greenhouse gas methane, according to the new report. Methane's sources include wetlands, agriculture, natural gas activity, and landfills.

“Only by reducing our dependence on fossil fuels and increasing energy production from renewable resources will we start to see improvements and begin to lessen the effects of climate change,” said ESRL scientist Pieter Tans, of the Global Monitoring Division. The Global Monitoring Division has monitored carbon dioxide emissions and other greenhouses gases for decades and will continue to do so to help assess the climate situation and advise decision makers, Tans said.

The increases in CO2 and methane during 2008 are slightly less than those measured in 2007, but fall well within the range of yearly fluctuations from natural changes, according to NOAA experts. CO2 levels vary from year to year along with plant growth and decay, wildfire activity, and soil conditions. But people’s burning of coal, oil, and gas for transportation, power, and industry create the insistent increase underlying those fluctuations.

Global averages of the concentrations of carbon dioxide and methane.

Global averages of the concentrations of the major, well-mixed, long-lived greenhouse gases - carbon dioxide, and methane from the NOAA global flask sampling network since 1978.

At the end of 2008, global average CO2 concentration was 386 parts per million (ppm); before the Industrial Revolution began in the 1880s, CO2 concentration was 280 ppm.

Methane levels rose in 2008 for the second consecutive year after a 10-year lull, for a 2008 global average concentration of 1,788 parts per billion (ppb). Pound for pound, methane is 25 times more powerful as a greenhouse gas than carbon dioxide, but because there is far less of it in the atmosphere, methane’s overall climate impact is half that of carbon dioxide.

Carbon dioxide growth rates have increased by more than two percent each year since preindustrial times, doubling every 31 years, according to a study published in Atmospheric Environment in December by ESRL’s David Hofmann, James Butler, and Tans.

The CO2 record does have dips: A slowdown occurred in 1930–1936 after the Great Depression, and another during the 1940s, possibly related to World War II. The large volcanic eruptions of Indonesia’s Mount Agung in 1963 and the Phillippines’ Mount Pinatubo in 1991 each slowed CO2 buildup for several years. Volcanic emissions cool the lower atmosphere and scatter sunlight. Those changes can reduce plant respiration, a process that releases CO2, and boost photosynthesis, which removes CO2 from the air.

“Atmospheric CO2 growth is best reflected by the world population trend,” said Hofmann. “The two have tracked each other extremely well over the past century.”

A break in the close relationship between population growth and CO2 growth would be a clear sign of progress in efforts to limit atmospheric CO2, Hofmann said.

—contributed by Anatta, NOAA

Read the Paper

Hofmann D. J., J. H. Butler, and P. P. Tans, 2008, A new look at atmospheric carbon dioxide, Atmospheric Environment, doi:10.1016/j.atmosenv.2008.12.028.