Climate Change Impacts the Weather: Earth's Wind and Rain Belts Shift North

Could we change the weather? As the climate changes and as wind patterns shift, we may accomplish just that. As the planet warms, Earth's wind and rain belts are shifting northward. This could make a broad swathe of regions much wetter while leaving others high and dry.

In order to learn exactly how warming conditions might impact weather patterns, the researchers looked to the past. They examined the warming that brought Earth out of its last ice age around 15,000 years ago. In all, they examined tree rings, polar ice cores, cave formations and ocean and lake sediments.

The scientists found that in the past, Arctic sea ice melted and set up a temperature contrast with the southern hemisphere where sea ice was expanding around Antarctica--much like what we're seeing today. The temperature gradient between the poles appeared to have pushed the tropical rain belt and mid-latitude jet stream north. This particular shift occurred somewhere between 14,600 years ago to 12,700 years ago.

So what impacts did this shift have? At the southern edge of the tropical rain belt, the great ancient Lake Tauca in the Bolivian Andes nearly dried up. Rivers in eastern Brazil also slowed to a trickle. In the middle latitudes, Lake Lisan, a precursor to the Dead Sea, began to shrink along with several prehistoric lakes in the western U.S.

While some areas dried up, though, other areas became wetter. The rivers that drained Venezuela's Cariaco Basin and East Africa's Lake Victoria and Lake Tanganyika were recharged. In addition, there were stronger Asian monsoons.

This particular shift mirrors what we're seeing today. The Arctic sea ice is again in retreat and the northern hemisphere is heating up far faster than the south.  It's not unusual for winds and rains to rearrange themselves. Yet exactly how long they rearrange themselves could greatly impact climate. For example, in the 1970s and 1980s, a southward shift of the tropical rain belt, attributed to air pollution cooling the northern hemisphere, ended up bringing a devastating drought to Africa's Sahel region. Since then, the tropical rain belt has reverted back and may now be moving north.

"It's really important to look at the paleo record," said Dargan Frierson, an atmospheric scientist at the University of Washington, in a news release. "Those changes were huge, just like we're expecting with global warming."

Currently, the researchers are examining the possibility of these shifting weather patterns a bit more closely. In the past, changes in sea ice cover drove the temperature gradient between the two hemispheres. In contrast, today the rapidly rising carbon emissions are responsible for the temperature shift. Even so, it's likely we'll see weather patterns change in the near future.

The findings are published in the journal Proceedings of the National Academy of Sciences.