Rivers of air that move both storms and airplanes around the planet have been creeping poleward over the past 26 years. The migration of these so-called ‘jet streams’ has widened the planet’s tropical belt and could expand dry regions around the world in coming decades, a new study reports. ‘If they move another 2 to 3 degrees poleward in this century, very dry areas such as the Sahara Desert could nudge farther towards the pole, perhaps by a few hundred miles,’ said study team member John Wallace from the University of Washington. The researchers used satellites to measure heat in the form of microwave radiation emitted by oxygen molecules in the atmosphere from 1979 to 2005. The troposphere at 30 degrees latitude in both hemispheres - roughly the location of Austin, Texas, and Cordoba, Argentina - has warmed by about 1.5 degrees Fahrenheit (1 degree Celsius) during that time. The troposphere extends up to about 7.5 miles (12 kilometers) from Earth’s surface and is the part of the atmosphere in which most weather occurs. Anatomy of the air The warming of the atmosphere at these latitudes causes the troposphere to expand and bulge poleward. This […]