New Study on Precipitation in Lower Latitudes May Portend More Flooding, Drought in Arctic

Jun 9, 2017

A portent of a wetter – or drier – Arctic …


Because they’re skeptics, scientists know to tread carefully when they come across stories that begin with the words “According to a new study…” But, a new study published last week about the impact of global warming on precipitation patterns in the lower and middle latitudes has caught the eye of John Walsh and other researchers.

“It’s the first study that’s brought together the various contributing factors, the wetness and dryness, into a single story,” says Walsh, chief scientist of the University of Alaska Fairbanks’ International Arctic Research Center. “And I think that’s where the authors deserve some credit.”

In this map from the study published in Science Advances, regions shown in green and blue will likely get wetter as the planet warms, and regions show in brown shades will get drier.
Credit Intergovernmental Panel on Climate Change

Walsh says he’s impressed by a study published last week in Science Advances, a journal of the American Association for the Advancement of Science, on how a warming atmosphere that’s able to hold more moisture may disrupt rainfall patterns in lower and mid-latitudes in the coming decades.

“On the one hand, we have the tendency for more rain when it gets warmer. That’s pretty well-established,” he said. “That’s the thermodynamic side of the story.”

But on the other hand, according to the study, the so-called “dynamical” influence of warming will alter that basic assumption and instead cause more rain in some regions and less or no rain in others.

“And those regions are going to shift, as climate warms,” Walsh said.

Global map included with the study shows temperature trends from 1951 to 2015. Graph at right of zonally averaged temperature trends shows the northern middle and high latitudes have warmed about twice as much as corresponding southern latitudes over the past half-century or so.
Credit Putnam, Broecker et al.

The study’s authors say warming may increase rainfall in the tropics and decrease it in the subtropics and mid-latitudes. Or, they say it could force the heavy precipitation that typically falls in those regions farther northward. Or, it may result in a combination of both scenarios.

Walsh says the study does not address whether the scenario of heavier tropical and subtropical rainfall moving northward will impact the Arctic and subarctic – perhaps because of a lack of data.

“The reason the Arctic and Antarctic did not get really mentioned in the arctic is because the dynamical changes that relate to dry and wet areas (in the region) is just not well-known,” he said.

Walsh says ongoing research by UAF and other institutions may fill those data gaps. He says that’s important to anticipate possible impacts in the far north such as increased flooding, drought and wildfires.