Want weaker hurricanes? Spew more pollution into the air. That’s what some scientists are saying.
If North Atlantic hurricanes are more destructive or more frequent, it may be linked to lower levels of atmospheric pollution. Conversely, sulphate aerosols and other particles from factory chimneys, vehicle exhausts, domestic fires, power stations and other human economic advances may have played a role in keeping tropical storms under control, at least a little, during the 20th century.
Climate scientist Nick Dunstone and fellow-researchers at the Met Office’s Hadley Centre in Exeter, Devon, report in the Nature Geoscience journal there is at least circumstantial evidence that aerosols play a more significant role in the storm cycle than anyone had expected.
I thought the science was settled and President Al Gore told us we’re getting more devastating storms because we’re such filthy polluters.
There was a lot of smog and soot before the first world war, then a fall in emissions. Factory exhausts faltered during the great depression of the 1930s, then built up again, but fell away during the second world war, before returning everywhere – and then falling away yet again as governments and voters began to respond to filthy cities and choking smoke.
Using climate simulations, the scientists were able to match storm records and predictions from 1860 to 2050 with recorded and predicted levels of atmospheric pollution, and identify an effect.
Through much of the 20th century, the Nature Geoscience paper suggests, aerosols actually suppressed the hurricane forces by cooling the ocean waters. It was not possible to match specific storms with a particular level of aerosol pollution, but in general there seemed to be less frequent tropical storms during periods of greater aerosol discharge.
The finding is consistent with other recent research. Smog and other discharges in the northern hemisphere in the mid-20th century were recently linked to the parching of the Sahel and the drying-up of much of Lake Chad, along with a weakening of the Indian monsoon.
However, nobody thinks the question is settled by the Met Office findings. What actually happens in a weather system, and how often, depends on many factors. Temperatures and atmospheric pollution are certainly factors, but they are not the only ones. Dust, transported over the oceans in vast clouds, must also play a role. And humans are not the only source of aerosols: volcanoes unpredictably inject huge quantities to almost stratospheric levels.