When it comes to the biggest climate change culprit, the finger is often pointed at carbon dioxide (CO2) but a recent study by the National Oceanic and Atmospheric Administration (NOAA) has found that while CO2 remains the “undisputed king of recent climate change”, other greenhouse gases also have a considerable role to play. But, even if we could target these gases, would it be enough to reduce the impacts of climate change? Perhaps.
Three NOAA scientists — Stephen Montzka, Ed Dlugokencky and James Butler of NOAA’s Earth System Research Laboratory in Colorado — were inspired to find out about these other gases around the time of the 2009 United Nations’ climate conference in Copenhagen.
Like CO2, other greenhouse gases trap heat in Earth’s atmosphere. Some of these chemicals have shorter lifetimes than CO2 in the atmosphere. Therefore cutting emissions would quickly reduce their direct radiative forcing — a measure of warming influence.
As part of their 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 study found that steep cuts (around the 80 percent mark specifically) would be difficult. Without substantial changes to human behavior, emissions of the non-CO2 greenhouse gases are expected to continue to increase.
What’s more, even if all human-related, non-CO2 greenhouse gas emissions could be eliminated today, it would not be enough to stabilise the warming influence from all greenhouse gases over the next 40 years – unless CO2 emissions were also cut significantly.
The scientists also note the complicated connections between climate and greenhouse gases, some of which are not yet fully understood. Accoridngt o Dlugokencky , 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. 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.”
Graphs courtesy of NOAA