Record and near-record breaking temperatures dominated the eastern two-thirds of the nation and contributed to the warmest March on record for the contiguous United States, a record that dates back to 1895. More than 15,000 warm temperature records were broken during the month.
The average temperature of 51.1°F was 8.6 degrees above the 20th century average for March and 0.5°F warmer than the previous warmest March in 1910. Of the more than 1,400 months (117+ years) that have passed since the U.S. climate record began, only one month, January 2006, has seen a larger departure from its average temperature than March 2012.
Also, science once again undercuts and eliminates one of the deniers most important arguments:
Climate scientists have long argued that ancient air trapped in Antarctic ice is the smoking gun that links carbon dioxide to global warming. Over the past 800,000 years or so the planet has gone through a series of ice ages interspersed with relatively warm periods (during which glaciers retreat back toward the poles) — and inevitably, these warm interludes happen when there’s more CO2 in the atmosphere.
The only tricky part of this argument is that the smoke seems to come before the gunshot. It’s most apparent in the most recent warming period, which began about 19,000 years ago: the temperature seems to begin rising before CO2 concentrations increase. Climate skeptics have argued that since effects don’t come before causes, the whole theory falls apart.
In fact, it’s not much of an argument, since even little bit of warming would release extra carbon dioxide into the air, leading to a feedback loop, causing even more warming. But whatever feeble merit the skeptic argument might have had, a new study just published in Nature — one of two climate studies from that prestigious journal that we’re reporting on — pretty much demolishes it. It’s the most comprehensive analysis ever done of carbon dioxide and temperature at the end of the last ice age, and it shows quite clearly that in most of the world, the thermometer began to shoot up only after the atmosphere was spiked with carbon dioxide. “I think,” said Jeremy Shakun, a Harvard postdoctoral fellow and the lead author of the study, at a press conference, “this ends the skeptic argument.“
Shakun’s confidence is based on the comprehensiveness of the research. Most of the evidence for an ancient CO2-warming link comes from cores drilled out of Antarctica’s 2-mile-thick blanket of ice. Air bubbles from different levels show how much of the heat-trapping gas the atmosphere held at different times, and the chemistry of the ice trapping the bubbles shows what the temperature was.
The problem, Shakun said, is that “these cores tell you only about temperatures in the Antarctic.” Just as you’d never infer global temperatures today from just a couple of sites, it’s not really reliable to look only to ice at the South Pole for global temperatures back then. So Shakun and his co-authors gathered no fewer than 80 different records of ancient temperatures, including lake sediments (different types of pollen at different depths point to what growing conditions were like) or sea-bottom cores (the shells of marine plankton, whose chemistry depends sensitively on ocean temperatures). It was, writes the British Antarctic Survey’s Eric Wolff in an accompanying Nature commentary, “. . . a major achievement: the difficulties of synchronizing the records and of ensuring that they are sufficiently representative of the whole planet, are considerable.”
What they found was that in Antarctica, there was indeed a bit of warming that preceded the rise in atmospheric carbon dioxide — but just a little, and only by a couple of hundred years. In the rest of the world, Shakun said, “global temperature clearly lags the CO2 buildup.” Cause, in short, really did come before effect.