Climate change deniers have been having a field day with all the snow this winter. If global warming is real, they say, then why are we getting buried in so much snow? Sunday, February 20, 2011 was the largest snowfall in a single 24-hour period ever recorded in Minneapolis, and in Minnesota overall, this has been the second snowiest February on record -- and the month isn't over yet. So, the skeptics say, how can it be getting warmer if we are buried in blizzards? And even if it is getting warmer, how can a few degrees make any difference?
Apparently it is making a big difference. Normally, we get cold weather in January and February here, but not much snow until March-April. But this winter, it has been as if the calendar moved up a month or two, and we are getting April's weather in February. And this, the scientists say, is indeed due to global warming.
To understand how global warming can produce more snow, we need to understand a basic fact of physics: warmer air holds more moisture! More moisture can mean more precipitation, either as snow or as rain. If you look at the Jet Stream on recent weather maps, you will see that it has repeatedly dipped way down south toward the Gulf of Mexico -- where the air is very warm and moist -- then it swings back up north, dragging all that extra moisture with it. The warm damp air hits the cold arctic air and whammo! Lots of snowfall on the good ol' USA.
But hasn't the Jet Stream always done this? To some extent, yes. But I'm over 60 years old and I can't ever remember it going down way into Texas like it has done recently. In the past, the Jet Stream remained pretty much up in Canada, with an occasional dip into Minnesota. It formed a relatively stable circle of air flowing around the arctic that fenced in the really cold air up there. Now, however, the Jet Stream has become unstable and is moving up and down the northern hemisphere rather erratically, causing extreme temperature swings (here in Minnesota, we have had a range of 35 below zero (F) to 60 above in a period of a mere two weeks) and a lot more precipitation.
Why is it doing this? According to a recent study released in January 2011, the melting of ice in the arctic is allowing the Earth to absorb more heat from the sun instead of reflecting it back into space like it used to.(Second basic physics fact: dark ocean water absorbs more sunlight that light snow and ice.) And it is doing this at a much higher rate than previously thought. Now, 32-degree sea water might not seem very warm to you and I, but it is a heck of a lot warmer than the below-zero snow and ice that used to be there. And once it absorbs that sunlight, it holds the heat, melting still more ice. This warming of the arctic is destabilizing the Jet Stream, which, as I explained above, results in more snow further south.
So, although it may seem paradoxical for warmer air to produce bigger snowstorms, the phenomenon is scientifically sound. You can't just look at a few local storms, you have to take into account the whole pattern of changes globally. And while a few degrees might not seem like much, we are not really talking about the difference between a 70 degree day and a 74-degree day. We are talking about the overall warming of the entire planet. It doesn't take much to alter the ocean and wind currents. Scientists say an overall change of 6 degrees can be disastrous. Already there has been a rapid increase in volcanic activity, earthquakes, severe hurricanes and other storms -- including snow! -- yet so many of us are still in denial about this!
How much do we humans contribute to climate change? Quite a lot, according to most climate scientists. Yes, the earth goes through natural cycles, but since the Industrial Revolution the greenhouse effect has accelerated at an unprecedented rate. The science is pretty firm now, with the vast majority of climate scientists agreeing there is a rapidly-accelerating problem. Yet I am often appalled at how many of people not only don't believe the science, they think it is merely a matter of politics, a sort of left-wing hoax perpetrated by the Democrats. (If Ronald Reagan had produced An Inconvenient Truth instead of Al Gore, would the right-wingers take global warming more seriously today? I wonder.)
James Hoggan, in his book Climate Cover-Up, presents a well-researched argument that from the 1980s onward, there has been an organized campaign on the part of Big Oil and Big Coal to convince us that global warming is a hoax. (Remember that notorious ad trying to convince us that excess carbon dioxide in the atmosphere was good?) I'm not normally into conspiracy theories, but this one is pretty convincing. Unfortunately, a lot of people have bought that argument, which delayed us doing anything about changing our lifestyles or lowering our carbon footprints. But I think it is becoming pretty evident that global warming is real -- even if is does produce more snow sometimes. Next time you are shoveling the stuff, blame it on that melting arctic ice.