Temperature change over past 11,300 years (in blue, via Science, 2013) plus projected warming this century on humanity’s current emissions path (in red, via recent literature).
A stable climate enabled the development of modern civilization, global agriculture, and a world that could sustain a vast population. Now, the most comprehensive “Reconstruction of Regional and Global Temperature for the Past 11,300 Years” ever done reveals just how stable the climate has been — and just how destabilizing manmade carbon pollution has been and will continue to be unless we dramatically reverse emissions trends.
Researchers at Oregon State University (OSU) and Harvard University published their findings today in the journal Science. Their funder, the National Science Foundation, explains in a news release:
With data from 73 ice and sediment core monitoring sites around the world, scientists have reconstructed Earth’s temperature history back to the end of the last Ice Age.
The analysis reveals that the planet today is warmer than it’s been during 70 to 80 percent of the last 11,300 years.
… during the last 5,000 years, the Earth on average cooled about 1.3 degrees Fahrenheit–until the last 100 years, when it warmed about 1.3 degrees F.
In short, thanks primarily to carbon pollution, the temperature is changing 50 times faster than it did during the time modern civilization and agriculture developed, a time when humans figured out where the climate conditions — and rivers and sea levels — were most suited for living and farming. We are headed for 7 to 11°F warming this century on our current emissions path — increasing the rate of change 5-fold yet again.
By the second half of this century we will have some 9 billion people, a large fraction of whom will be living in places that simply can’t sustain them — either because it is too hot and/or dry, the land is no longer arable, their glacially fed rivers have dried up, or the seas have risen too much.
We could keep that warming close to 4°F — and avoid the worst consequences — but only with immediate action.
This research vindicates the work of Michael Mann and others showing that recent warming is unprecedented in magnitude, speed, and cause during the past 2000 years — the so-called Hockey Stick — and in fact extends that back to at least 4000 years ago. I should say “vindicates for the umpteenth time” (see “Yet More Studies Back Hockey Stick“).
Lead author Shaun Marcott of OSU told NPR that the paleoclimate data reveal just how unprecedented our current warming is: “It’s really the rates of change here that’s amazing and atypical.” He noted to the AP, “Even in the ice age the global temperature never changed this quickly.”
And the rate of warming is what matters most, as Mann noted in an email to me:
This is an important paper. The key take home conclusion is that the rate and magnitude of recent global warmth appears unprecedented for *at least* the past 4K and the rate *at least* the past 11K. We know that there were periods in the past that were warmer than today, for example the early Cretaceous period 100 million yr ago. The real issue, from a climate change impacts point of view, is the rate of change—because that’s what challenges our adaptive capacity. And this paper suggests that the current rate has no precedent as far back as we can go w/ any confidence—11 kyr arguably, based on this study.
Katharine Hayhoe, an atmospheric scientist at Texas Tech University, told the AP:
We have, through human emissions of carbon dioxide and other heat-trapping gases, indefinitely delayed the onset of the next ice age and are now heading into an unknown future where humans control the thermostat of the planet.
Unfortunately, we have decided to change the setting on the thermostat from “Very Stable, Don’t Adjust” to “Hell and High Water.” It is the single most self-destructive act humanity has ever undertaken, but there is still time to aggressively slash emissions and aim for a setting of “Dangerous, But Probably Not Fatal.”
This article was originally posted on Climate Progress. Re-posted with permission.
