At first listen, it sounds like something that would go against the core beliefs of any eco-expert, but recent research shows that air polluted skies are helping plants to reduce global warming. A study from 1960 to 1999, led by Dr. Lina Mercado from the UK Centre for Ecology and Hydrology, was published earlier this year in the Nature scientific journal reporting that plants stored 23.7 percent more CO2—the leading greenhouse gas causing climate change—thanks to more efficient photosynthesis in plants shaded by smog. Does this mean that burning fossil fuels might actually be the solution to cooling the earth?
The study attests that plants, ranging from broadleaf trees to grasses, photosynthesize at greater rates and take in more CO2 in dimmer lighting. The study’s co-author Dr. Stephen Sitch said that “although many people believe that well-watered plants grow best on a bright sunny day, the reverse is true. Plants often thrive in hazy conditions such as those that exist during periods of increased atmospheric pollution.” A separate 2003 study, by the United Nations’ Intergovernmental Panel on Climate Change, showed similar findings for the benefits of hazy skies, concluding that aerosols may counteract 75 percent of the warming effect, thus preventing the planet from becoming almost two degrees warmer than it is now.
We want to make it clear that these findings are not to suggest that aerosols (air particles) created by the industrial pollutants and smoke of burning rainforests, crop waste and fossil fuels are good for the earth. Both studies stress that this is not the only solution and calls for lower emission standards to combat global warming, which they predict will increase earth’s temperatures 10 degrees by the end of the century. Mercado notes that “global dimming” could only go so far before it reaches a threshold after which the benefits of diffused light no longer offset the drawbacks. If the atmosphere reached the threshold it would reduce plant photosynthesizing, while also increasing asthma and lung problems for humans and animals.
The other point to consider is that global dimming has not been found as a benefit for arctic regions, and that aerosols are causing catastrophic damage in those regions. Drew Shindell of the NASA Goddard Institute for Space Studies, New York, has been studying the Arctic region over the past 40 years and concludes that 45 percent or more of the warming that has occurred as a result of industrial pollutants. This is due to the Arctic’s proximity to North America and Europe, the two regions which have produced most of the world’s aerosol emissions over the last century, and also because of low precipitation levels which normally flush aerosols out of the atmosphere.
Discovering that global dimming increases carbon intake by plants might become a topic for special interest groups to lobby against change in emission standards, but we do not believe that these findings will put a halt to major international efforts against pollution reduction. Climatology experts from these studies do not refute the need to reduce pollutants. Their goal is to point out the complexity of monitoring climate change, and to consider the benefits of global dimming when designing policies and standards.
Via BBC News