Researchers at James Cook University looked at long-term satellite measurements, atmospheric balloon soundings and climate models in determining that the tropics have widened by more than 300 miles (500 km) over the past 25 years.

The accompanying expansion of sub-tropical climates could also dry out fertile regions that currently receive ample rainfall. Such a development would have devastating effects on health and food production, the researchers warn.

Professor Sandra Harding said tropical climates had already moved more than six degrees of latitude beyond the traditional confines of the Tropics of Cancer and Capricorn, and were continuing to expand.

Regions of temperate Mediterranean climate that border the subtropics appear to be particularly vulnerable, and are already experiencing the effects of climate change, Harding said.

Map Data: Earthbrowser