Geoengineering the climate could reduce vital rains

Attempts to geoengineer the climate in order to lower greenhouse gases in the atmosphere could reduce vital rains in several parts of the world, including East Asia, a new study has found.
Although a significant build-up in greenhouse gases in the atmosphere would alter worldwide precipitation patterns, a widely discussed technological approach to reduce future global warming would also interfere with rainfall and snowfall, researchers said.
The international study, led by scientists at the National Centre for Atmospheric Research (NCAR), finds that global warming caused by a massive increase in greenhouse gases would spur a nearly seven per cent average increase in precipitation compared to preindustrial conditions.

However, trying to resolve the problem through "geoengineering" could result in monsoonal rains in North America, East Asia, and other regions dropping by 5-7 per cent compared to preindustrial conditions.
Globally, average precipitation could decrease by about 4.5 per cent, the study found.
"Geoengineering the planet doesn't cure the problem," said NCAR scientist Simone Tilmes, lead author of the study.

"Even if one of these techniques could keep global temperatures approximately balanced, precipitation would not return to preindustrial conditions," said Tilmes.
As concerns have mounted about climate change, scientists have studied geoengineering approaches to reduce future warming.
Some of these would capture carbon dioxide before it enters the atmosphere. Others would attempt to essentially shade the atmosphere by injecting sulfate particles into the stratosphere or launching mirrors into orbit with the goal of reducing global surface temperatures.

The new study focuses on the second set of approaches, those that would shade the planet. The authors warn, however, that Earth's climate would not return to its pre-industrial state even if the warming itself were successfully mitigated.
"It's very much a pick-your-poison type of problem," said John Fasullo, a co-author.
"If you don't like warming, you can reduce the amount of sunlight reaching the surface and cool the climate. But if you do that, large reductions in rainfall are unavoidable. There's no win-win option here," said Fasullo.
The study appears in the Journal of Geophysical Research.