This month, we’ve had a striking run of below-zero weather, so we can expect to hear this trumpeted by some as proof positive that global warming (climate change) is a hoax. But that, of course, is wrong — and here’s why.
What we experienced this month is nothing more than “weather,” experienced on one tiny part of Montana, on one really tiny part of the earth. Global warming, or climate change, deals with what’s happening with temperature, CO2 and weather planet-wide, and on a scale of multiple decades or centuries — not yesterday.
So, how do we know that the earth is warming? Well, we’ve got good temperature records going back to the late 1870s; the role of CO2 in global warming has been known for longer than that; tree rings give a good climate picture stretching back nearly 5,000 years; and ice cores in Greenland and Antarctica give us accurate, observable data on CO2 and temperature levels going back 800,000 years. And what all of those sources show is a gradual temperature increase around 1850 coming out of the Little Ice Age (1350-1850), followed by a significant increase in the 1880s after the discovery of oil, and temperatures taking off globally around 1980.
And the same data looking at past climates suggests that the last time global temperatures were at their current levels was about 125,000 years ago, and the last time CO2 levels hit the current level of 400 ppm (parts per million) was 3 million years ago. So what? Well, what we consider modern human civilizations with towns and cities, domesticated crops and livestock only date back about 12,000 years, and arose during a period of comparatively moderate, stable climate — something we’re rapidly leaving behind.
OK, so the global climate is getting hotter, and we just blew through the bright red line of CO2 above 400 ppm, but isn’t that all just part of a natural cycle? Sorry folks, can’t help you there. Peer-reviewed science by thousands of the world’s top climatologists from nearly 100 countries over the last 40 years clearly shows that “it is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century… there are no alternative explanations supported by the evidence that are either credible or that can contribute more than marginally to the observed patterns" (Intergovernmental Panel on Climate Change, 2016).
The only question now is whether we’ll pull together to solve this self-created crisis, or continue our sleepwalk into oblivion.