PNAS
These climate change maps indicate that novel climates are projected for tropical and subtropical regions, and disappearing climates are predicted to be concentrated in tropical mountains and the poleward regions of continents. The left column represents an extreme scenario for future climate change and the right a more moderate scenario.
msnbc.com news services
updated 3/26/2007 5:32:21 PM ET 2007-03-26T21:32:21

Global warming could re-make the world's climate zones by 2100, with some polar and mountain climates disappearing altogether and formerly unknown ones emerging in the tropics, scientists said on Monday.

Such changes would endanger some plants and animals while providing new opportunities for others, said John Williams, a study co-author and an assistant professor of geography at the University of Wisconsin, Madison.

"What we've shown is these climates disappear, not just regionally, but they're disappearing from the global set of climates, and the species that live in these climates really have nowhere to go as the system changes," said Williams.

Previous studies have raised the concern about species extinctions in specific areas — such as the cloud forest of Costa Rica or the Cape region in South Africa — but this is the first to predict this global change, Williams said.

Using global change forecasts prepared for the Intergovernmental Panel on Climate Change, researchers led by Williams used computer models to estimate how climates in various parts of the world would be affected. Their findings were published in this week’s online edition of Proceedings of the National Academy of Sciences.

The IPCC, representing the world’s leading climate scientists, reported in February that “warming of the climate system is unequivocal, as is now evident from observation of increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level.”

Very different tropics?
The models suggest that existing climate areas will shift toward higher latitudes and higher elevations, squeezing out the climates at the extremes — tropical mountaintops and the poles — and creating new climates around the equator, particularly the rain forests in the Amazon and Indonesia, Williams’ researchers concluded.

This was surprising, Williams said, since the tropics tend to have little variation in weather.

But that also means temperature changes of 3 or 4 degrees in these regions might have more impact than a change of 5 to 8 degrees in a region that is accustomed to regular changes.

Species living in tropical areas may be less able to adapt, he said, adding that that is speculative and needs further study.

Areas like the Southeastern United States and the Arabian Peninsula may also be affected, the researchers said.

And they said mountain areas such as in Peruvian and Colombian Andes and regions such as Siberia and southern Australia face a risk of climates disappearing altogether.

That doesn’t mean these regions would have no climate at all — rather their climate would change and the conditions currently in these areas would not occur elsewhere on Earth.

That would pose a risk to species living in those areas, Williams observed.

The unknown of 'novel' climates
If some regions develop new climates that don’t now exist, that might provide an opportunity for species that live there, Williams said. “But we can’t make a prediction because it’s outside our current experience and outside the experience of these species.”

Alan Robock, a professor of environmental sciences at Rutgers University welcomed the report, calling it the first he has seen “that not only looks at species extinctions, but also looks at regions where novel climates will appear.”

“While the idea of novel climates may seem like a positive consequence of humans using the atmosphere as a sewer and causing rapid, unprecedented climate change, I would argue that mitigation of our pollution should be an even stronger reaction to these results,” said Robock, who was not part of the research team.

“The potential consequences and how these new regimes will be populated are poorly known, and the potential for new threats to humans through disease vectors could be a real danger,” he said.

Williams noted that existing strategies to deal with warming are based on current conditions, not potentially altered climate regions. “How do you make predictions for these areas of the unknown?” he asked.

A key question is becomes not just whether a given climate still exists, Williams said, but “will a species be able to keep up with its climatic zone? Most species can't migrate around the world.”

The Associated Press and Reuters contributed to this report.

Video: Disappearing climates

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