The benefits of clean energy are widely discussed, and there is a wide consensus among people in government, science, media, and business that cutting greenhouse gas emissions and other forms of pollution will lead to a cooler globe, or at least limit the warming that it is feared could be catastrophic for the planet.
However, in a new study published in the journal Geophysical Research Letters, Canadian researchers report that that the reduction in the amount of sulfur dioxide (produced by fossil fuel combustion) in the atmosphere has actually contributed to an increase in the amount of Arctic sea ice melt that has taken place since 2000.
In an article titled, “Impact of aerosol emission controls on future Arctic sea ice cover” researchers state that the increased amount of aerosols in the atmosphere before reaching a peak at around the turn of the century have contributed to the cooling of the atmosphere, and have offset the amount of global warming that had taken place.
From the abstract of the paper:
The overall decrease in aerosol loading causes a warming, largest over the Arctic, which leads to an annual mean reduction in sea ice extent of approximately 1 million km2 over the 21st century in all RCP scenarios. This accounts for approximately 25% of the simulated reduction in sea ice extent in RCP 4.5, and 40% of the reduction in RCP 2.5. In RCP 4.5, the Arctic ocean is projected to become ice-free during summertime in 2045, but it does not become ice-free until 2057 in simulations with aerosol precursor emissions held fixed at 2000 values. Thus, while reductions in aerosol emissions have significant health and environmental benefits, their substantial contribution to projected Arctic climate change should not be overlooked.
The authors say that the reason for the cooling effect is caused by sulfate and organic carbon in the atmosphere scattering solar radiation which result in a net cooling of the climate system.
I find this an interesting study, and perhaps one that will be seen as rather controversial, since it predicts that one of the effects of burning fossil fuels is a cooling one, even though greenhouse gases and black carbon are also produced, which are considered to contribute to warming. Volcanoes and wildfires also contribute to sulfur dioxide in the atmosphere.
It would seem that reduction of sulfur dioxide in the atmosphere would be very desirable from the point of view of reducing health problems and environmental contamination. But like the authors say, there may be some consequences of a move to more clean energy sources that need to be considered when looking at the big picture.
One of the study’s authors, Nathan Gillett, is quoted on the Arctic Newswire website as saying that he does not want to give the impression that air quality standards should be reduced, but that that there is a warming role played by reducing sulfur dioxide. ““We’re really just pointing out that it’s part of the picture and should be considered . . . We’re not trying to weigh costs and benefits of sulfur dioxide here.”