Climate change could pose a greater risk to tropical insects and other species sensitive to the slightest shifts in temperature than to creatures living in the world's tundra, US scientists warn.

While cold weather animals are used to huge temperature changes, tropical species live under a much smaller temperature range and face a bigger risk of extinction with an increase of just 2 or 4°C, according to a team led by University of Washington scientists.

"In the tropics many species appear to be living at or near their thermal optimum, a temperature that lets them thrive," says Dr Joshua Tewksbury, an assistant professor of biology.

"But once temperature gets above the thermal optimum, fitness levels most likely decline quickly and there may not be much they can do about it," he says.