Is This Global Warming?

Boston experienced its warmest winter ever and the past couple of weeks have been way warmer than usual. By this Thursday we are supposed to hit a record-shattering 86 F, weather that belongs in July or August. My students, my neighbors, and it seems everyone is asking "is this global warming?"

The short answer would have to be "no." If you check out today's New York Times weather map you will see a simple explanation for this weather. On one side of the continent the jet stream has dipped way south, providing the West with unusual coolness and rain, even into Phoenix. Meanwhile, the pattern of the jet stream in the midwest and east coast is experiencing the "flipside" of the circulation coin, traveling far to our north.

So, simply put, the flow dynamics of the jet stream, while unusual, are immediately responsible for this weather.

Another part of the story...in Boston we boast that the month of March lasts here for ninety days. What do we mean by that? Again the simple answer is that the Atlantic Ocean, a huge body of water that takes relatively long to warm up in the spring, is right at our front door. Ocean breezes come inland through June, taking even the warmest days down into the 50s. Why isn't that happening now? Simply because the southwesterly flow of air, which is linked to the flow of the Jet Stream, is strong enough to keep an onshore breeze from occurring. The result? We stay warm.

A third part of the story is explained by our weather last week. A "back door cold front" bathed the city in cool ocean air carried on a breeze from the northeast. This wasn't a nor'easter because there was no precipitation involved with it. It was simply part of the dynamic of an air current circulating around a high pressure area to our north and east. The weather last week was more like San Francisco than Boston, consistently cool, oceany, and never warming up even in full sunlight.

So, it all these patterns point to a "no" for global warming, why do scientists insist that the phenomenon is real?

For an answer to this question all you have to do is go to the superb "Earth Observatory" sponsored by NASA. All kinds of interactive maps will show you that there have been long-term warming trends, not necessarily on land, not necessarily in the temperate zones where most people would notice it, but in the Arctic Ocean and waters adjacent to it.

Scientists have demonstrated without question that the planet is warming by using simple methods of observation. That doesn't mean we notice it on a day to day basis. Certainly if we compare last winter's notable cold and abundant precipitation with this year's winter, we see a big difference. But that is not the evidence for global warming.

Global warming and global climate change are planet-wide phenomena that are measured not day to day, but over decades, and not in a single locality like Boston, but all over the Earth, including our oceans.

Enjoy the nice weather but think hard about how your own activities can calm the trend to global warming. Walk, ride a bike, or take public transportation instead of driving. Turn down the heat and skip the AC. Eat less meat. Try to travel less by air.