Nothing But Words

Cross-posted to TPMCafe

UPDATE: the Editor of Technology Review posted a comment (apparently they’re watching their incoming links), saying that there was enough demand for the “scary chart” that they’ve now posted it to their site as a PDF (it’s much nicer than my scan).

Technology Review’s “Scary Chart” depicting the effects of greenhouse gases on climate over the past 400,000 years View at Picasa Technology Review’s “Scary Chart” depicting the effects of greenhouse gases on climate over the past 400,000 years

Technology Review’s latest issue contains an excellent set of articles on global warming. Unfortunately, the online version is lacking “the scariest graph in climate science, a 420,000-year record of carbon dioxide and temperature, inferred from a 3.6-kilometer ice core recovered at Russia’s Vostok station in Antarctica.” I’ve taken the liberty of scanning it and posting it here (click it for a larger view, and then click the magnifying glass icon in the upper right for the full-size view). It’s the clearest illustration I’ve ever seen of the relationship between atmospheric CO₂ levels, temperature, and sea level. While the article says that “atmospheric concentrations of carbon dioxide have increased 32 percent since 1850,” you don’t get a gut-level feel for what that means until you see the CO₂ level going way off the top of the chart at the end of the graph. Here’s the key portion of the inset text that accompanies the graph:

…Geological records show that in the past 400,000 years, atmospheric concentrations of carbon dioxide, average Earth temperature, and sea levels have risen and fallen roughly in tandem, in 100,000-year cycles paced by slight oscillations in Earth’s orbit. These oscillations affect the distribution of sunlight, hardly affecting the total amount reaching Earth; yet, scientists believe, this has been enough to set in motion chains of events that raise and lower temperatures, launch and end ice ages, and trigger vast changes in sea level.

What’s coming next? Carbon dioxide — the number one greenhouse gas — has much more power to affect Earth’s temperature than the orbital changes do. And in just the past 150 years, humankind has boosted carbon dioxide concentrations by 32 percent. NASA planetary scientist Jim Hansen says that if we continue to increase greenhouse-gas emissions, temperatures will rise between 2 and 3 ºC this century, making Earth as warm as it was three million years ago, when seas were between 15 and 35 meters higher than they are today….

The article that goes with the graph – The Messenger – is also highly worth reading. It covers the career of leading climatologist Jim Hansen, and among other things, describes the censorship of his work by the Bush Administration:

According to NASA memorandums provided by Hansen, senior political appointees at NASA headquarters in Washington quickly called career public-affairs officers at the agency and directed them to give headquarters advance notice of Hansen’s speaking schedule, his “data releases,” and his attendance at scientific meetings. The career officers also understood from the phone calls that the posting of all content on the GISS website, including scientific data sets, would now require headquarters approval; that no NASA employees or contractors could grant media interviews without approval; and that public-affairs officers had the right to stand in for scientists in all interviews. Hansen emphasizes that the political appointees made sure to leave no paper trail…He says he’s been muzzled before — during the Reagan and first Bush administrations — but that in more than three decades as a government employee, he has seen nothing to equal the recent clampdown.

What makes Hansen’s work compelling is that he uses multiple sources to check the accuracy of his models. You’ll need to read the article for a detailed explanation, but the bottom line is this:

Global-warming deniers like to complain that scientists base their predictions on faulty computer models. But Hansen’s calculations show that we don’t need a computer to know how temperature will respond to a given change in the greenhouse — or a change in dustiness, or forest cover, or the amount of ice on the Arctic Ocean. Solid geological field data give us everything we need — and provide a check for computer models. And lend credibility to Hansen’s predictions.