''The Industrial Revolution is turning Earth into an alien planet, at least for creatures like humans who are endemic to an icehouse environment. Homo sapiens and many other life forms alive today evolved to thrive under icehouse conditions, where the planet has polar ice caps, relatively low temperatures, and carbon at 250-350 ppm in the atmosphere. As you can see in the graphic below, the planet hasn't always been an icehouse during its more than 4 billion years in the Solar System. But we and our ecosystems happened to evolve during millions of years of cooling, and we need to keep things chill."
-- Annalee Newitz. io9 editor