Scientists find the world has been getting fatter

It really has all gone pear-shaped: the Earth has now become fatter around the middle after 19 years of a shrinking waistline.

The equator has been expanding for four years, according to two American scientists who have been studying the Earth's girth for 25 years. Christopher Cox and Benjamin Chao found a measurement of the Earth's width called J2, which excludes tidal effects, had been decreasing for most of that time.

But they then discovered that about four years ago the Earth's "dynamic oblateness", its girth, began to increase and was continuing to do so.

According to their calculations, neither global sea level rise nor faster melting of glacial ice could have produced such a sharp change. Mr Cox, of Raytheon Information and Scientific Services, and Dr Chao, a Nasa scientist, suggested that shifting of mass between the Earth's core and near-molten mantle layer might be responsible.

Mr Cox added later that the increase in the Earth's width was in the order of only a few millimetres.