Do human greenhouse gases play less of a role in global warming than initially suspected? A new study suggests that's the case, blaming water vapor for up to a third of the global warming throughout the 1990s. Damn you, water!
The discovery is the result of research carried out by a team from the US National Oceanic and Atmospheric Administration, led by Susan Solomon, who argues that it doesn't lessen the responsibility humanity has for global warming but may explain why global warming has slowed in the past decade:
[T]his [new study] shows there are climate scientists round the world who are trying very hard to understand and to explain to people openly and honestly what has happened over the last decade... We call this the 10, 10, 10 problem. A 10% drop in water vapor, 10 miles up has had an effect on global warming over the last 10 years.
If the theory holds, it also explains a rise in the rate of warming in the two last decades of the 20th century, where there was a rise in water vapor. What remains unexplained is why the levels of vapor have fluctuated so much, and whether their drop over the last ten years is, itself, related to global warming.