Posted on behalf of Roberta Kwok
Scientists have found a new way to estimate past climate: snakes. 
In case you haven't seen the media flurry, researchers have uncovered the remains of a gigantic snake in northeastern Colombia (which news outlets have described as "Super-snake", "Bus-sized boa", and "Granddaddy of the snake world", among other things). The newly named Titanoboa cerrejonensis would have measured 13 metres long and weighed about 1,135 kilograms, making it the biggest known snake, living or extinct.
Why does this matter for climate predictions? The snake lived 58 to 60 million years ago, around the Palaeocene when the Earth's upper latitudes were much warmer than they are today. This was a time when ice at the poles had melted and crocodiles roamed the Arctic. But, as climate scientist Matthew Huber describes in a Nature News & Views article, researchers are less sure how hot the tropics were during that time.
Vertebrate paleontologist Jason Head of the University of Toronto in Canada and his colleagues, who reported the snake discovery in Nature, reasoned that such a large snake could only survive at a certain temperature. Snakes rely on external heat from their environment to help fuel their metabolism. The bigger the snake, the more heat it requires, which is why you don't see pythons in Minnesota.
The researchers used a model relating animal body size and ambient temperature to determine how hot the tropics must have been to support the snake. Today's tropics average 26-27 degrees Celsius, and the largest "verifiable" modern anaconda is 7.3 metres long, the study says. Assuming Titanoboa had a similar metabolic rate to today's snakes, the team calculated, the Palaeocene tropics must have been 30-34 degrees Celsius.
"We've taken the snake and turned it into a giant thermometer," says Head.
The finding suggests that as Earth's higher latitudes warmed up during the Palaeocene, the tropics got hotter as well. This goes against the argument that the Earth has a 'thermostat' mechanism that keeps tropical temperatures steady. And while the comparison between the natural global warming of the Palaeocene and modern human-induced global warming is "very tenuous", Head says, it might mean that today's tropics will heat up just as fast as the rest of the world, potentially leading to more extinctions around the equator.
Lisa Sloan, a climate scientist at the University of California, Santa Cruz, calls the study "intriguing". Although it would have been nice to get estimates from other large Palaeocene creatures as well, she says, the approach has "a lot of potential" for future research.
Image: Jason Bourque
