It seems pretty obvious to most people living in northern Europe, and both northern and southern states in America this winter that global warming is certainly not happening to them. Yes, it’s warmer in Alaska than usual, but banks of snow further south are as high as 20 feet, a shaft of bitterly cold air called a polar vortex has arrived from the arctic, and even southern states are experiencing unusually frosty temperatures. Forecasters are warning that this winter weather could go on through March. Nobody but an idiot snowman would call this global warming, would they?
As a matter of fact, harsher winters in the north, both more droughts and floods in farmlands, and more extreme weather events like tornadoes and hurricanes are what climatologists have predicted would be likely outcomes of global warming. The surprise for the climatologists is that these effects might be happening sooner than almost any one predicted.
How might global warming give millions of us colder winters? The explanation is in the jet stream. It forms when the cold air of the Arctic bashes into the warmer air arriving from the south. The bigger the temperature differences between the two air masses, the faster the resulting weather passes on. But in recent decades, while the air from both the north and south has been getting warmer, the northern arctic air has been getting warmer 2-3 times faster than its southern counterpart.
As a result, the cold Arctic weather dips further south than it used to, resulting in that polar vortex causing unaccustomed havoc so far south. Then when the two masses of air do clash, their temperature differences are less extreme than they used to be and the storms of snow or rain resulting from the clashes tend to pass on more slowly. Instead, storms tend to stick around.
If this change in the jet stream continues, whatever may be causing it, the changes on agriculture could be dire. It is not so much the average temperature change that will affect crop and animal production, but the temperature and weather extremes that tend to do the damage.
But a single winter, no matter how many weather records may be broken, are not a certain sign that it is a result of global warming. To achieve reasonable certainty, climate change will have had to produce a pattern of several decades – by which time we won’t need the scientists to tell us what’s happened.
Unfortunately, the only chance we have of avoiding the destructive effects of global warming is to prevent it from happening in the first place. Once it’s established, we are unlikely to be able to reverse it.
Why that is so is the subject for a future post.