BREDASDORP, South Africa — A scruffy crew of scientists barreled down a dirt road, their two-car caravan kicking up dust. After searching all day for ancient beaches miles inland from the modern shoreline, they were about to give up.

Suddenly, the lead car screeched to a halt. Paul J. Hearty, a geologist from North Carolina, leapt out and seized a white object on the side of the road: a fossilized seashell. He beamed. In minutes, the team had collected dozens more.

Using satellite gear, they determined they were seven miles inland and 64 feet above South Africa’s modern coastline....

In any given era, the earth’s climate responds to whatever factors are pushing it to change.

Scientists who study climate history, known as paleoclimatologists, focus much of their research on episodes when wobbles in the earth’s orbit caused it to cool down or warm up, causing sea level to rise or fall by hundreds of feet....