Air Pollution is Driving Fewer Monsoons?

A new study has found that pollutant emissions produced by human activity has been causing the world's total annual monsoon rainfall to decline over the past five decades. And while that may be good news for some flood-prone regions, experts do not doubt that it has had a significant adverse impact on delicate ecologies.

That's all according to a study recently published in the journal Geophysical Research Letters.

"This study shows for the first time that the drying of the monsoon over the past 50 years cannot be explained by natural climate variability," lead author Debbie Polson of the University of Edinburgh explained in a recent statement. "Human activity has played a significant role in altering the seasonal monsoon rainfall on which billions of people depend."

Polson and her colleagues determined this after calculating the average summer monsoon rainfall in the Northern Hemisphere between 1951 and 2005. They then used computer-based climate models to assess the impact of increasing aerosol emissions and greenhouse gases over the same period.

Natural factors such as volcanic activity and climate variability were of course taken into account, but even with these considered, the levels of rain recorded during the Northern Hemisphere's summer monsoon fell by as much as 10 percent during the second half of the 20th century.

Anthropogenic aerosols, tiny air particles from man-made sources, are theorized to be the cause, and the density and prevalence of these emissions has apparently soared since the 1950s.

According to the study, high levels of these aerosols in the atmosphere can cause heat from the Sun to be reflected back into space, lowering temperatures on the Earth's land and reducing rainfall.

And while reducing surface temperatures may sound strange in the wake of climate-warming talks, the NOAA has reported that it's sea warming, not land surface warming, that is driving global net temperature hikes - resulting in this year's warmest summer on record.

Now the inordinate dry weather seen across the Northern Hemisphere these past few years can be explained for, too.