Human activity is changing rainfall pattern across the world, according to a new study appearing in this week's issue of the journal Nature.
The scientists found that about 1.8 inches (4.5 centimetres) more rain fell annually in Canada, Russia, and Europe in recent years than it did in 1925, while in the northern tropics and subtropics, such as Mexico and northern Africa, rainfall decreased by nearly 2.8 inches (7 centimetres) per year.
Elsewhere, the southern tropics and subtropics such as Peru and Madagascar, witnessed increased rainfall of about 2.4 inches (6 centimetres), the study revealed.
According to lead author Xuebin Zhang of Environment Canada in Toronto, altogether humans account for about two-thirds of the precipitation increase in Canada, Russia, and Europe, a third of the drying out in the northern tropics and subtropics, and nearly all of the increase south of the Equator.
In the new study, Zhang and his team examined precipitation trends in different sections of land north and south of the Equator, rather than the globe as a whole.
They then compared the observations to the changes in rainfall that multiple climate models predict should be attributable to human activity.
The comparison showed that most of the changes in precipitation were due to human actions.
"You have this large-scale engine that moves moisture around the planet, and under greenhouse gas forcing, this engine essentially become more intense. Since we have this large number of simulations, we can average them all together in essence and filter out the effects of internal variability ... to obtain a best estimate," National Geographic quoted study co-author Francis Zwiers, a climate scientist with Environment Canada, as saying.