Climatide

Katkamin / Flickr

The pre-Halloween nor'easter that swept through New England last weekend dumped up to three feet of snow, downing trees still laden with green leaves and causing widespread power outages.

Was last weekend’s intense snow storm just a freak occurrence? Or a symptom of climate change? It’s a question that has been bouncing around in the wake of the storm that dumped feet of snow on parts of New England and left millions in the region without power. Few things touch us as frequently and personally as the weather, so it’s no wonder this kind of question arises whenever the weather turns unusual.

Unfortunately, a definitive answer will take time (not to mention some cutting edge science). But AP’s Seth Borenstein offered this preliminary assessment earlier this week:

The most recent bizarre weather extreme, the pre-Halloween snowstorm that crippled parts of the Northeast last weekend, cannot be blamed on climate change and probably isn’t the type of storm that will increase with global warming, according to four meteorologists and climate scientists.

Experts on extreme storms have focused more closely on the increasing number of super-heavy rainstorms, not snow, NASA climate scientist Gavin Schmidt said.

A note of caution here: scientists initially said that the Russian heatwave of 2010 was unlinked to climate change but a new study released last week found there was an 80% chance climate change was a contributing factor. So we really will just have to wait for the jury to come back.

In the meantime, here’s something we already know:

National Climatic Data Center

Data compiled by the National Climatic Data Center show that extreme one-day precipitation events have spiked in recent years.

Extreme cold season precipitation events in the northeast are definitely getting more common, as the Washington Post reported earlier this week. The graph at right tells the story pretty plainly. Historically, about 10% of weather stations in the northeast have reported extreme one-day precipitation events between October and March. But four of the last six years have seen levels above 40%. That spiked to a record-setting 77% in 2010.

Of course, it’s not just the northeast. Weather events worldwide have been hitting new extremes in recent years. There are any number of reports or statistics one could point to in support of this idea. Most recently, the Intergovernmental Panel on Climate Change (IPCC) is soon to issue a special report on extreme weather and climate change. Seth Borenstein obtained a draft copy of the report:

A draft summary of an international scientific report obtained by The Associated Press says the extremes caused by global warming could eventually grow so severe that some locations become “increasingly marginal as places to live.”

Predictions in the report include more extreme heat waves and droughts, stronger (but not more frequent) hurricanes and tropical cyclones, and more intense monsoons. By the end of the century, what have been 20-year rainstorms will likely be 5-year rainstorms, Borenstein reports. What’s more:

The draft says there is at least a 2-in-3 probability that climate extremes have already worsened because of man-made greenhouse gases.

Because of the difficulties inherent in linking any one weather event to the long-term processes of climate change, scientists are often somewhat hesitant in their public statements in this area. But there is now compelling scientific evidence (not to mention the personal experiences of millions of people) that the weather is getting more extreme – as climate scientists have long predicted it would – and that climate change is to blame.