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Warming to Create Previously Unknown Climates, Study Says

Hannah Hoag
for National Geographic News
March 27, 2007
 
Global warming will redraw Earth's climate map by the end of the
century, causing some of today's climates to disappear and creating
other climates unlike anything known today, according to a new study.

Specifically, brand-new climates will appear in the tropical and subtropical regions, while some climates of the tropical mountains and the regions around the Poles will be entirely replaced by 2100.

For the new study, researchers used forecasts from the most recent report from the Intergovernmental Panel on Climate Change (IPCC) to create a computer model that estimates how different parts of the world would be affected by warming.

The results appear in this week's issue of the online early edition of the Proceedings of the National Academy of Sciences.

"So much of the novel and disappearing climates are occurring at the low latitudes [around the Equator]," said study co-author Steve Jackson of the University of Wyoming, Laramie. "None of us expected this."

That's because Jackson and colleagues thought the greatest shifts would happen at Earth's Poles, where the largest temperature changes are expected to occur.

Instead, small changes in temperature and humidity in other regions, particularly in the tropics, will have greater affects on those overall climates, the study shows.

The researchers also found that the predicted changes could trigger local extinctions, reshuffle current plant and animal communities, and make conservation efforts more difficult.

From Novel to Nonexistent

Jackson and colleagues' computer model shows that the overall climates of North America and Europe will shift, but will resemble climates we already know.

The Florida peninsula, however, will develop a never before seen climate that is much hotter and drier in the summer.

The Amazon Basin will also develop a new climate that will be hotter and wetter between June and August than it is now, the model predicts.

"It won't be like anything we've experienced since the last interglacial period," Jackson said. "Some of these novel climates have probably never existed on Earth, or at least not in the last few million years."

At the same time, climates along the highest points of the Andes mountains of South America will disappear due to temperature increases.

"These are the coolest parts of the tropics, and that climate is being pushed off the mountaintops and into the atmosphere," Jackson said.

The climates of the mountains along Africa's Great Rift Valley, southeast Australia, portions of the Himalaya, the Indonesian and Philippine archipelagos, and some circum-Arctic regions are also among those that will disappear, according to the model.

Hot Spots at Risk

The predicted changes would create conservation challenges, the authors note, because many of the areas where climates are disappearing are concentrated in biodiversity hot spots—areas rich with unique and threatened plants and animals.

Climate change appears to already be causing extinctions for some species, especially those confined within narrow temperature ranges and those living in colder parts of the globe (related news: "Global Warming Already Causing Extinctions, Scientists Say" [November 28, 2006]).

"Some species will respond quite quickly to climate change and move into a region or out of a region, but others will move more slowly," said John Williams, a study co-author at the University of Wisconsin, Madison.

When a climate disappears, some of the plants and animals adapted to it might not be able to adjust or migrate to a friendlier but far-away climate.

"Plants in biodiversity hot spots [for example] are very poor at dispersing their seed" in a relatively short time frame, said Guy Midgley of the South African National Biodiversity Institute.

"There is very little chance that they would be able to disperse on the order of tens of kilometers, let alone hundreds of kilometers."

And animal species that are already at risk wouldn't be helped by traditional conservation techniques such as reintroducing captive-bred creatures to the wild if their native habitats are drastically altered.

Even more radical moves such as assisted migration would no longer be viable if the animals didn't have a receptive region to move to.

Alan Pounds is a biologist at the Monteverde Cloud Forest Preserve in Costa Rica, where he has linked amphibian declines to climate change.

"We could lose entire cloud forest communities. As climate spaces disappear, it will be very difficult to save species," Pounds said.

"We're going to lose a large number of species if we don't reduce our greenhouse gas emissions."

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