Scientists stirred to ridicule ice age claims
Climate scientists have been stirred to ridicule claims in an upcoming Hollywood blockbuster that global warming could trigger a new ice age, a scenario also put forward in a controversial report to the US military.
The $125-million epic, The Day After Tomorrow, opens worldwide in May. It will show Manhattan frozen solid after the warm ocean current known as the Gulf Stream shuts down.
The movie's release will come soon after a report to the US Department of Defense (DoD) in February predicting that such a shutdown could put the northern hemisphere into a deep freeze and trigger global famine within 15 years.
But in the journal Science on Thursday, Andrew Weaver of the University of Victoria in British Columbia, Canada, surveys the current research and concludes "it is safe to say that global warming will not lead to the onset of a new ice age".
Salty water
The DoD's doomsday scenario, which is very similar to that in the film, was drawn up by Peter Schwartz and Doug Randall of the San Francisco-based Global Business Network. Neither is a climate scientist.
The scenario suggests that as global warming melts Arctic ice packs, the North Atlantic will become less salty. This would shut down a global ocean circulation system that is driven by dense, salty water falling to the bottom of the north Atlantic and that ultimately produces the Gulf Stream.
This much is respectable scientific theory, and some researchers believe it could happen for real in 100 years or so. But the film-makers and DoD authors go further.
They say it could happen very soon. And that if it did, the northern hemisphere would cool so much that that ice sheets would start to grow, creating a catastrophic new ice age.
This is too much even for sympathetic climatologists. Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research in Germany, whose own models say the Gulf Stream could shut down within a century, told New Scientist: "The DoD scenario is extreme and highly unlikely."
Achilles heel
And Wallace Broecker of Columbia University, New York, US, who has warned for two decades that the Atlantic circulation is "the Achilles heel of our climate system", seriously questions both the speed and severity of the changes proposed.
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In a letter to Science, he accuses the DoD authors of making exaggerated claims that "only intensify the existing polarisation over global warming". He adds: "What is needed is not more words but rather a means to shut down CO2 emissions." Such action could avert any Gulf Stream shutdown in the next 100 years.
Schwartz defends his scenario, saying that while it is "not the most likely scenario, it is plausible, and would challenge US national security in ways that should be considered immediately".
Weaver notes that the movie's budget "would fund my entire research group for my entire life, 10 times over". That might even allow him to discover which scenarios are most plausible.
But there are no sour grapes. "I will be one of the first to see the movie.," he says. "It'll be the Towering Inferno of climate - extremely entertaining." It will not confuse the public, he thinks, but it will not help them understand climate science either.
Fred Pearce