Giant Snakes And Global Warming...Together At Last!

Yesterday, I touched briefly on the subject of Titanoboa cerrejonensis, the 40+ foot fossil snake discovered recently in a Colombian coal mine. Interestingly enough, the discovery of such a huge snake has implications for the AGW theory. From Not Exactly Rocket Science:

The giant snake's measurements even tell us something about the climate of this ancient world. Snakes are cold-blooded. Their body temperature, and therefore their metabolism, depends on their surroundings, which slaps an upper limit onto the evolution of giants. At any given temperature, a snake can only become so large before its metabolic rate becomes too low to support its bulk. If Titanoboa was bigger than living species, its environment must have been much hotter.

Head estimated that the tropical rainforests where it lived must have had average yearly temperature of 32-33 degrees Celsius, far hotter than the equivalent temperatures for modern tropical forests. These estimates suggest that the forests of that period were experiencing greenhouse conditions. These conditions, part of the planet's history, have been written in stone, left for us to glean among the petrified bones of an ancient snake.

Now, so what if the tropics at the time were quite a bit warmer than today? Well, according to researchers like Lindzen and, more recently, Spencer, the Earth possesses an

...“adaptive infrared iris” that opens and closes to keep the earth’s temperature fairly steady even in light of increasing atmospheric carbon dioxide levels. It was proposed to work something like this—when the temperature in the tropical oceans begins to warm up, it causes in increase in the amount of low-level water clouds and an even greater decrease in total coverage of high-altitude ice clouds. Since ice clouds are net warmers (that is, they trap more outgoing longwave radiation (heat) than they reflect away incoming shortwave (solar) radiation) and water clouds are (generally) net coolers (reflecting back to space more incoming solar shortwave radiation than they absorb outgoing longwave radiation), more of the latter and a lot less of the former leads to a net cooling, and the temperatures of the tropical oceans decrease. However, cooler tropical ocean temperatures lead to less low-level (water) clouds and more high altitude ice clouds. This configuration tends to lead to a net radiation increase and to higher temperatures. And the cycle starts over again. Lindzen’s moniker “adaptive infrared iris” refers to the mechanism in which the tropical ice cloud cover opens and closes in response to tropical ocean temperatures to allow more heat to escape to space when the oceans are warm and less heat to escape to space when the oceans are relatively cool (much like the iris of an eye which opens and closes in response to varying light levels to try to maintain a constant level falling on the retina). Lindzen et al. proposed that the iris acts as a global thermostat that will keep the earth’s temperatures from rising very far even as atmospheric concentrations of greenhouse gases increase.

In other words, there are planetary feedback mechanisms that kick in whenever temperatures become too hot or too cold, and keep the global average temperature in essentially the same place (Gaia fights back! as it were).

...which is to say that a tropical temperature high enough to allow the existence of Titanoboa ought not to occur. If Jason Head and co. (the paper's authors) are correct, then Lindzen's Iris Theory, not in particularly good shape these days to start with, takes another hit.

Dot Earth's Andy Revkin also suggests that the discovery of Titanoboa challenges

...those using the specter of tropical warming — including the Amazon rain forest turning into a desert — as another reason to move swiftly to curb greenhouse gases.

...because clearly this much hotter tropical forest was a "steamy thriving" place.

Interesting stuff.

Oh, and read the dinosaur list archives for speculation on the answer to the most important question: In a Fight, who would win? Giant snake or T-Rex?