UPDATE 5/10/13 10:30 AM: And so the threshold has been passed—at least according to the National Oceanic and Atmospheric Administration. The agency reported that the daily average of carbon concentration levels at the Mauna Loa observatory on May 9 was 400.3 ppm—as far as I know, the first time carbon has passed the 400 ppm mark since well before modern humans were making a mark on the planet. It’s all new from here on in.
As I wrote last week, the carbon concentration in the Earth’s atmosphere is nearing 400 parts per million (ppm). (399.71 ppm right now, according to the Scripps readings Mauna Loa.) The last time carbon levels in the atmosphere were that high was at least 800,000 years ago, and quite possibly much, much longer. What we do know is that the climate was much warmer—up to 11 F warmer on average—and very, very different than the one we’ve lived in rather successfully for thousands of years.
Just how different the climate was is underscored by a new study published in the May 9 Science. Researchers at American, Russian and German universities traveled in the winter of 2009 to the ice-covered Lake El’gygytgyn in far northeastern Russia, more than 50 miles north of the Arctic Circle. The lake was formed some 3.6 million years ago when a massive meteorite struck the Earth’s surface, gauging out a deep crater. Sediment collected in the crater over time, which has made the lake a gold mine for geoscientists, who are able to analyze the past climate of the surrounding area through the rock record.
The scientists took core samples of the sediment—records in rock of the past that go back millions of years ago. And their findings suggest that the Arctic was very warm between 3.6 and 2.2 million years ago, during the middle Pliocene and Early Pleistocene epochs. So warm in fact—with balmy summer temperatures in the between 59 and 61 F, more than 14 F warmer than they are today—that the Arctic was largely without sea ice, and was thickly forested, more like southern Canada than the forbidding region we know today. And this came during a time period when atmospheric carbon levels were not much higher than they are today.
Lead author Julie Brigham-Grette of the University of Massachusetts-Amherst said in a statement:
While existing geologic records from the Arctic contain important hints about this time period, what we are presenting is the most continuous archive of information about past climate change from the entire Arctic borderlands. As if reading a detective novel, we can go back in time and reconstruct how the Arctic evolved with only a few pages missing here and there.
And that detective novel may not have a happy ending—at least for human civilization as we know it. As the authors write in the Science paper: “this could tell us where we are going in the near future. In other words, the Earth system response to small changes in carbon dioxide is bigger than suggested by earlier climate models.”
There are still pieces to the climate puzzle that need to be filled in. The study shows that unusually warm temperatures in the Arctic seemed to persist even as glaciers we’re begin to expand in the Northern Hemisphere. But studies like this one help us understand just how changeable our climate—so secure during the history of human civilization—has been in the past, and underscores just how momentous our impact on the planet through the burning of fossil fuels is likely to be. We are well into uncharted territory.
But there’s something about the sheer scale of what’s happening that makes it hard for us to really comprehend. The same day the Science paper came out, a new Yale University poll came out showing that the percentage of Americans who believed global warming had dropped to 63% from 70% in the fall—a change that pollsters blamed on the unusually cold winter and spring that hit parts of the country. That’s not surprising—belief in climate change has usually been broad but deep, easily affected in either direction by passing weather events. But as the deep past show us, the climate works on time scales far bigger than a single season. It’s something we may have to experience before we can ever understand it.