Slow climate change by cutting other gases
For the new analysis, the researchers considered methane; nitrous oxide; a group of chemicals regulated by an international treaty to protect Earth’s ozone layer; and a few other extremely long-lived greenhouse gases currently present at very low concentrations.
The new review paper describes the major human activities responsible for these emissions, and notes that steep cuts (such as 80 percent) would be difficult. Without substantial changes to human behavior, emissions of the non-CO2 greenhouse gases are expected to continue to increase.
click image to zoomNOAAThe direct radiative forcing (warming effect) of greenhouse gases under various scenarios. a) Red: constant 2008 emissions of both CO2 and non-CO2 greenhouse gases. b) An 80% cut in non-CO2 emissions. c) An 80% cut in CO2 emissions. d) An 80% cut in all greenhouse gas emissions. In all scenarios, emissions cuts are phased in between 2009 and 2050. The climate-related benefits of reductions in non-CO2 greenhouse gases have limits, Montzka and his colleagues showed. Even if all human-related, non-CO2 greenhouse gas emissions could be eliminated today, it would not be enough to stabilize the warming influence from all greenhouse gases over the next 40 years – unless CO2 emissions were also cut significantly.
The scientists also noted in the paper the complicated connections between climate and greenhouse gases, some of which are not yet fully understood. The non-CO2 gases studied have natural sources as well as human emissions, and climate change could amplify or dampen some of those natural processes, Dlugokencky said. Increasingly warm and dry conditions in the Arctic, for example, could thaw permafrost and increase the frequency of wildfires, both of which would send more methane and carbon dioxide into the atmosphere.
“The long-term necessity of cutting carbon dioxide emissions shouldn’t diminish the effectiveness of short-term action. This paper shows there are other opportunities to influence the trajectory of climate change,” Butler said. “Managing emissions of non-carbon dioxide gases is clearly an opportunity to make additional contributions.”