in an interview.

On average, storms have been peaking 56 kilometers closer to the poles each decade for the past 30 years, so they are now 169 km deeper into each basin, according to the research by Kossin and his co-authors, Kerry Emanuel, a professor of atmospheric science at the Massachusetts Institute of Technology in Cambridge, and Gabriel Vecchi, a scientist at the Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey.

The shift is consistent with independent studies that have shown tropical regions have expanded because of climate change, Kossin said.

Expanding tropics

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The previous studies have found that the depletion of the ozone layer, an increase in greenhouse gases and more aerosols, such as black carbon, in the atmosphere may all be contributing to the expansion of the tropics, Kossin said.

TheGerman soldier posed as Syrian refugee and 'planned attack' Published duration 27 April 2017

image copyright Reuters image caption The German soldier did not speak Arabic but received refugee aid, reports say

A German soldier who pretended to be a Syrian refugee and was allegedly planning a gun attack has been arrested in southern Germany.

Prosecutors in Frankfurt said the 28-year-old suspect was motivated by a "xenophobic background".

A student, 22, said to be a co-conspirator, has also been arrested.

The soldier was first detained by Austrian police in February after he tried to retrieve a handgun he had hidden in a toilet at Vienna airport.

He was released but police subsequently discovered the suspect had registered as a Syrian refugee at a shelter in central Germany in December 2015 and later officially requested