Large Snake Fossil Discovered

According to the New York Times a very large snake fossil was found in Columbia. In life it was as long as a school bus and weighed more than a ton.

From the article:

But the existence of such a large snake may also help clarify how hot the tropics became during an era when the planet, as a whole, was far warmer than it is now, and also how well moist tropical ecosystems can tolerate a much warmer global climate.

all emphasis mine. So how is it again that it was decided that warmer than it is now is BAD?