Monday, December 2, 2013
With the conclusion of COP19 and renewed attention to the problem of climate change, an important point seems to need making again. So if you will permit me, I would like to do so here:
Reducing short-lived climate pollutants (SLCPs) does not decrease the urgency of reducing carbon dioxide emissions (CO2).
This is something the CCAC says repeatedly. Reducing emissions of SLCPs, or non-CO2 forcers, can have a large benefit through reduced near-term warming and improved human and ecosystem health. But SLCP mitigation does not have much impact on long-term peak warming and so does not “buy time” for reducing CO2.
As we say in our basic brochure and all our literature, “Fast action to reduce [SLCPs], especially methane and black carbon, has the potential to slow down the warming expected by 2050 by as much as 0.5°C, as well as prevent more than two million premature deaths each year and avoid annual crop losses of over 30 million tonnes. These actions need to be complemented by deep and rapid cuts in carbon dioxide emissions if global mean temperature increase over the 21st century is to be held below 2°C.”
Action on SLCPs doesn't take the pressure off the need to limit CO2 emissions. But to say, as some people have, that reducing SLCPs is of little value to climate unless action is also taken on CO2, is not accurate. Reducing SLCPs is a way to reduce the damages over the next several decades, which are likely to be more of the type that are already having large impacts, for example on agriculture as rainfall patterns change, on snow and ice melt, and on storm and rainfall intensity. Reducing those impacts is certainly a very worthy societal goal alongside trying to keep peak temperatures in the more distant future from getting too high. The latter is obviously a worthy goal, but it's not the only one.
Indeed, for the broader community beyond scientists, it's quite important to consider all the effects caused by releasing pollutants into the atmosphere, including impacts on long-term peak warming, impacts on near-term warming rates, impacts on rainfall, and impacts on agriculture and health via pollution. Perspectives that look only at the first effect are necessarily relevant only to that first one, and they don't give the full picture that decision-makers should keep in mind.
I continue to believe that there is convincing evidence that societies need to reduce both emissions of CO2 and emissions of SLCPs and not one or the other.