Warmer Temperatures: More Snow

February 12th, 2013 | Simcha Weinstein | Comments Off on Warmer Temperatures: More Snow

blizzardFor decades scientists have been predicting that increased greenhouse gas emissions would lead to an increase in extreme weather events, especially more intense precipitation. With snow blanketing much of the northeast over the weekend, the anti-science crowd (who have been doing an amazing job pushing the myth that big snowstorms somehow undercut our understanding of human-caused global warming) took the opportunity to remind us that global warming and climate change are basically a joke. In their minds snow automatically refutes the idea that global temperatures are rising, for after all, if we’re getting warmer it shouldn’t snow, right?

For scientists who study the climate, it’s all a bit much. Aside from the fact that precipitation isn’t temperature (oddly these two are often confused for one another), it turns out that the common wisdom – lots of snow means we must be getting colder rather than warmer – is simply not true, and not the reason for the heavy snowfall in new England. The climate in New England has actually been changing for quite some time. Snow cover is decreasing and spring arrives earlier. And the number of extremely hot summer days has also been increasing. According to a report from the Northeast Climate Impacts Assessment (NECIA) team, since 1970, the Northeast has been warming at a rate of nearly .5 degrees F per decade, with winter temperatures rising even faster, at a rate of 1.3 degrees F per decade from 1970 to 2000 – all changes consistent with those expected to be caused by global warming.

To understand the severity of this weekend’s storm here are some helpful facts:

– Ingredients for a big snowstorm include temperatures just below freezing. In past years temperatures at this time in the northeast would have been significantly below freezing. The ideal temperature for a blizzard is just below the freezing mark – just cold enough to crystallize water into snow. Below that, the atmosphere’s ability to hold moisture to create those snowflakes drops by 4 percent for every one degree Fahrenheit fall in temperature, and so in the past we would have had a snow storm with the fronts that came through, but not with these amounts.

– The moisture flow into the storm is also important and that is enhanced by higher than normal sea surface temperatures (SSTs). Sea surface temperatures are about two degrees Fahrenheit warmer than they were before 1980, raising the potential for a big snow by about 10 percent, according to climate science.

So here’s the very simple, short version of how this works – warming temperatures mean more precipitation. Warmer water means more water vapor rises up into the air, and what goes up must come down. Snow has two basic ingredients: cold and moisture. Warmer air collects moisture like a sponge until it hits a patch of cold air. When temperatures dip below freezing, a lot of moisture creates a lot of snow. That’s basic science. The fact that we still get snowfall (particularly in the northeast) during the winter months only means one thing – that it’s winter. Just because we’re experiencing global warming, doesn’t mean that suddenly winter will disappear and we’ll never see snow again. If we were warming at that fast a clip, we would have already experienced sea levels rising to a point where hundreds of millions of lives would either have been displaced from their homes or lost altogether. Much of the earth as we know it would literally be underwater and uninhabitable by human beings if our winter months had warmed to a point where it no longer snowed in the northeast.

It’s a pretty ridiculous leap to assert that a snowstorm – even a blizzard – means that the earth is not warming. Precipitation is different than temperature. And while this seems pretty apparent, our national conversation on climate seems like a conversation second grade school kids might have (although they are probably more keen to the issue than many of our elected leaders) after a big snowfall. And facts matter. If we are ever going to move forward with reasonable action that can create a sustainable future for the next several generations, then we need to have a dramatic mind shift when it comes to our understanding of climate change… and we need to have it very soon. And apparently, summer will be the best time of year to have this discussion.