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Cool summer doesn’t invalidate climate change

Despite New England’s experience, 2013 was, worldwide, the hottest year on record, and 2014 may be hotter still.Matthew J. Lee/Globe Staff/File

Labor Day has come and gone. Autumn looms. But how can summer be over when it never really began?

If you feel cheated — where were the scorchers and leaden humid nights? — it’s not your imagination. July and August really did feel more like an extension of spring than a separate season. The Boston area had but four days over 90 degrees; usually it has 10. Average temperatures for the summer were well below normal too. This, of course, followed on the heels of a cold and snowy winter that felt like it would never end. And, to top it off, the Farmers’ Almanac predicts that the winter to come will be even worse than last.


So much for this global warming nonsense, huh?

Admit it. In some fashion, you’ve probably given voice to the thought. If climate change is real — if the world is supposedly heating up — then how come last winter was so long and our summer so cool? It’s because our perspective is skewed. We’re like a guy with his head in the refrigerator while his house is burning down, thinking nothing’s wrong. In fact, climate change proceeds apace. Our cool summer offers proof.

The world continues to get warmer. Of that, there is no doubt. The United Nations’ Intergovernmental Panel on Climate Change just released drafts of its most recent assessment (the final version should be issued in October), and the news is grim. “Each of the past three decades has been successively warmer at the earth’s surface than all the previous decades in the instrumental record, and the first decade of the 21st century has been the warmest,” it notes. Indeed, despite New England’s experience, 2013 was, worldwide, the hottest year on record, and 2014 may be hotter still. And the impacts of that rise are now being observed everywhere. The oceans are warmer. Ice sheets in Greenland, the Antarctic, and Arctic are getting smaller. Glaciers are retreating. The acidity of the oceans (caused by the absorption of carbon dioxide) has gone up 30 percent since the mid-1800s. Sea levels are rising too — 6.7 inches in the last 100 years. Extreme weather events are on the rise.


So why did we have such a cold winter and cool summer? It all has to do with the polar vortex. That’s the age-old weather phenomenon that we all learned about last year. The vortexes (there are two, north and south) are like slow-moving cyclones high in the atmosphere that circle the poles. They’re cold, not surprisingly, because the poles are cold. But, in the case of the Arctic, the impacts from the vortex to the lower levels of the atmosphere usually stay close to the pole because warmer air in the continental United States, acting as a front, keeps them there. But — thanks to global climate change — the Arctic is actually warming up faster than the rest of the world. (The reason is that ice reflects the sun, while water absorbs it. As Arctic ice is melting, there is now more sea water to absorb the sun’s energy.) That makes the difference in temperatures between the continent and the Arctic less, and so now the colder air on occasion swoops lower. Thus, the seeming contradiction: Our cold weather proves global warming.

The fact that such contradictions exist underscores the complexity of figuring out global climate change. It’s that same complexity that gives rise to those who would deny it. They’ll point to anomalous events such as a cool summer. They’ll wonder how we can know what temperatures will be like 40 years from now when the best of forecasters can’t tell for certain whether tomorrow will rain or shine. And they’ll dispute the models themselves, filled with uncertainty and assumptions.


But it’s not possible to refute what we are already seeing. And it’s not possible to refute as well that carbon dioxide concentrations in the atmosphere have climbed dramatically, now 40 percent greater than at the time of the American Revolution. If you count yourself a climate-change skeptic, read the full UN report. Keeping your head stuck in the refrigerator doesn’t change the reality of what is happening around you.

Tom Keane can be reached at