In a parched corner of the Sahara desert rears a block of pink stone decorated with prehistoric rock art. Human figures by the dozens are daubed in red-brown paint alongside the occasional antelope and lion. But what makes these pictographs so famous are figures that appear to be swimming in what is now the world's largest hot desert.
"Six thousand years ago, the Sahara was a grassland. At some point, it switched from being a place with lakes to a desert. And that is really amazing to me," says John Chiang, a UC Berkeley professor of geography.
Egypt's Cave of the Swimmers, or Wadi Sora, is emblematic of the climate conundrums Chiang likes to unravel. A climatologist, he studies how interactions between the oceans and our atmosphere can drive climate conditions from drought to deluge, or transform a landscape from green and lush to virtually uninhabitable.
The broad reach of tropical ocean-atmosphere interactions can be seen close to home in California. The El Niño Southern Oscillation cycle, which dictates winter droughts or flooding in the Bay Area and beyond, is dependent upon sea surface temperatures in a swath of the Pacific Ocean from Indonesia to Peru.... Read the rest of the story