The tropical region has been expanding since 1979

From satellite temperature data collected between 1979 and 2005, US researchers calculated that the earth's tropics expanded two latitudes, equivalent to 225 km.

The Sahara will move several hundred kilometers to the extreme.( Photo: NASA )

Dr. Thomas Reichler, professor of meteorology at the University of Utah in Salt Lake City and colleagues - the author of the study - admitted they were not sure whether global warming was the cause of this phenomenon.

" It is a big change ," Reichler said. This phenomenon could explain the increase in drought and precipitation in recent years in subtropical regions, such as the southwestern United States and the region. Mediterranean basin of Europe .

" Tropical belt expansion may be an entirely new aspect of climate change. We don't know what triggered it, " Reichler admitted.

In addition to global warming, another possible cause is depletion of stratospheric ozone due to pollutants.

Meteorologists have long conventioned the tropical region between 30 degrees north latitude and 30 degrees south latitude. However, according to Reichler and colleagues, at both hemispheres at these medium latitudes, the low air layer near the ground (or the troposphere) has become warmer than other latitudes in over the past 26 years, while the stratosphere has become cooler.

The team believes that this change has pushed tropical turbulence winds into two poles.

" These vortex currents mark the edge of the tropics, so if they are moving towards the two poles of the earth, that means the tropics are expanding ," said study co-author John Wallace. He said that the movement of these vortices would have a long-term effect on rainfall.

Wallace predicted that the tropical belt would " move another 2-3 degrees to the extreme in this century, while extremely arid regions such as the Sahara desert could go further to the ends of the earth, perhaps hundreds of miles ".

T. An