There is no shortage of articles or arguments about how much humans contribute to climate change and extreme weather- you could even say there is a flood of them. What there is less of, though, perhaps a trickle, is hard evidence of a cause and effect relationship between human behavior and extreme weather events. Researchers from Environment Canada claim to have established the definitive link between greenhouse gasses and extreme precipitation.
The number of intense precipitation events (when a near-record amount of rain falls in few hours or days) has been increasing, albeit slowly, over the past 50 years. But even if the numbers show this to be true, is it because of global warming? The core message of the study seems to be that climate change is not causing extreme weather events, but it is changing the probability. While that may infuriate people on both sides of the issue, it also opens the door for some middle ground.
Xuebin Zhang, senior climate scientist at Environment Canada in Toronto, was the lead on a 2007 study that found human emissions of greenhouse gasses have “helped lead to an increase in total precipitation in some regions, and a decrease in other parts of the globe.” Environment Canada’s most recent study examined data from over 6,000 weather stations across North America, Europe and Asia. They found that “the increasing amount of heat-trapping gases, like carbon dioxide (CO2), in the atmosphere have contributed to heavier rainfall, and that the changes are not solely due to natural variations in climate.”
The researchers are not claiming that climate change is the sole cause of increasing extreme weather, but that it is making it more intense and more frequent. It’s interesting that a conclusion like that may be harder to deal with than the extreme opinions on either side. While we may not have to take the full blame for bringing apocalyptic rains, it seems we do have an effect on the probability of those rains coming down.
Photo Credit: Hanoi Mark via Flickr under CC