Greenhouse gas growth rates

TitleGreenhouse gas growth rates
Publication TypeJournal Article
Year of Publication2004
AuthorsHansen, J, Sato M
JournalProceedings of the National Academy of Sciences of the United States of America
Date PublishedNov
ISBN Number0027-8424

We posit that feasible reversal of the growth of atmospheric CH4 and other trace gases would provide a vital contribution toward averting dangerous anthropogenic interference with global climate. Such trace gas reductions may allow stabilization of atmospheric CO2 at an achievable level of anthropogenic CO2. emissions, even if the added global warming constituting dangerous anthropogenic interference is as small as 1degreesC. A 1degreesC limit on global warming, with canonical climate sensitivity, requires peak CO2 approximate to 440 ppm if further non-CO2 forcing is +0.5 W/m(2), but peak CO2 approximate to 520 ppm if further non-CO2 forcing is -0.5 W/m(2). The practical result is that a decline of non-CO2 forcings allows climate forcing to be stabilized with a significantly higher transient level of CO2 emissions. Increased "natural" emissions of CO2, N2O and CH4 are expected in response to global warming. These emissions, an indirect effect of all climate forcings, are small compared with human-made climate forcing and occur on a time scale of a few centuries, but they tend to aggravate the task of stabilizing atmospheric composition.