The cold truth about climate change

That brings us to another problem with the word "consensus." It can mean "unanimity" or "the judgment arrived at by most of those concerned." Many, if not most, people hear the second meaning: "consensus" as majority opinion.

The scientific consensus most people are familiar with is the IPCC's "Summary for Policymakers" reports. But those aren't a majority opinion. Government representatives participate in a line-by-line review and revision of these summaries. So China, Saudi Arabia and that hotbed of denialism -- the Bush administration -- get to veto anything they don't like. The deniers call this "politicized science," suggesting the process turns the IPCC summaries into some sort of unscientific exaggeration. In fact, the reverse is true. The net result is unanimous agreement on a conservative or watered-down document. You could argue that rather than majority rules, this is "minority rules."

Last April, in an article titled "Conservative Climate," Scientific American noted that objections by Saudi Arabia and China led the IPCC to remove a sentence stating that the impact of human greenhouse gas emissions on the Earth's recent warming is five times greater than that of the sun. In fact, lead author Piers Forster of the University of Leeds in England said, "The difference is really a factor of 10."

How decent of the IPCC not to smash the last hope of deniers like Fred Thompson, whose irrational sun worshiping allows them to ignore the overwhelming evidence that human emissions are the dominant cause of climate change.

How else does the IPCC lowball future impacts? The 2007 report projects sea level rise this century of 7 to 23 inches. Yet the IPCC itself stated that "models [of sea level rise] used to date do not include uncertainties in climate-carbon cycle feedbacks nor do they include the full effect of changes in ice sheet flow."

That is, since no existing climate models fully account for the kinds of feedbacks we are now witnessing in Greenland and Antarctica, such as dynamic acceleration of ice sheet disintegration or greenhouse gases released by melting tundra, the IPCC is forced to ignore those realities. The result is that compared to the "consensus" of the IPCC, the ice sheets appear to be shrinking "100 years ahead of schedule," as Penn State climatologist Richard Alley put it in March 2006

According to both the 2001 and 2007 IPCC reports, neither Greenland nor Antarctica should lose significant mass by 2100. They both already are. Here again, the conservative nature of the IPCC process puts it at odds with observed empirical realities that are the basis of all science.

It's no surprise then that three scientific studies released in the past year -- too late for inclusion by the IPCC -- argue that based on historical data and recent observations, sea level rise this century will be much higher than the IPCC reports, up to 5 feet or more. Even scarier, the rate of sea level rise in 2100 might be greater than 6 inches a decade!

And it's no surprise at all that sea-level rise from 1993 and 2006 -- 1.3 inches per decade as measured by satellites -- has been higher than the IPCC climate models predicted.

The deniers are simply wrong when they claim that the IPCC has overestimated either current or future warming impacts. As many other recent observations reveal, the IPCC has been underestimating those impacts.

Since 2000, carbon dioxide emissions have grown faster than any IPCC model had projected.

The temperature rise from 1990 to 2005 -- 0.33°C -- was "near the top end of the range" of IPCC climate model predictions.

"The recent [Arctic] sea-ice retreat is larger than in any of the (19) IPCC [climate] models" -- and that was a Norwegian expert in 2005. Since then, the Arctic retreat has stunned scientists by accelerating, losing an area equal to Texas and California just last summer.

"The unexpectedly rapid expansion of the tropical belt constitutes yet another signal that climate change is occurring sooner than expected," noted one climate researcher in December.

This last point, though little remarked on in the media, should be as worrisome as the unexpectedly rapid melting of the ice sheets. As a recent study led by NOAA noted, "A poleward expansion of the tropics is likely to bring even drier conditions to" the U.S. Southwest, Mexico, Australia and parts of Africa and South America. Also: "An increase in the width of the tropics could bring an increase in the area affected by tropical storms." And finally: "An expansion of tropical pathogens and their insect vectors is almost certainly sure to follow the expansion of tropical zones."

Why are recent observations on the high side of model projections? First, as noted, most climate models used by the IPCC omit key amplifying feedbacks in the carbon cycle. Second, it was widely thought that increased human carbon dioxide emissions would be partly offset by more trees and other vegetation. But increases in droughts and wildfires -- both predicted by global warming theory -- seem to have negated that. Third, the ocean -- one of the largest sinks for carbon dioxide -- seems to be saturating decades earlier than the models had projected.

The result, as a number of studies have shown, is that the sensitivity of the world's climate to human emissions of greenhouse gases is no doubt much higher than the sensitivity used in most IPCC models. NASA's Hansen argued in a paper last year that the climate ultimately has twice the sensitivity used in IPCC models.

The bottom line is that recent observations and research make clear the planet almost certainly faces a greater and more imminent threat than is laid out in the IPCC reports. That's why climate scientists are so desperate. That's why they keep begging for immediate action. And that's why the "consensus on global warming" is a phrase that should be forever retired from the climate debate.

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