The Earth's seemingly widening midsection is proving something of an environmental puzzle for scientists.
New research in the journal Nature Geoscience suggests the Earth's tropical belt has expanded a few hundred miles over the past 25 years. The growing belt could mean more arid weather for some already parched regions, such as the American Southwest and the Mediterranean. And it's not clear if the expansion is temporary.
Climate scientists have long predicted a growing tropical belt toward the end of the 21st century because of man-made global warming. But the study's author says the expansion is larger and more puzzling than initially predicted.
Some say changes in El Nino since the 1970s probably affected the weather data collected.
Others say computer models have consistently underestimated the ill effects of global warming.