Articles by Joseph Romm

On the climate change ‘point of no return’

I've argued that scientists are not overestimating climate change, and in fact are underestimating it because they are omitting crucial amplifying feedbacks from their models. In this post, I'll show how these omissions suggest the climate has a "point of no return" that severely constrains the safe level of human-generated emissions.

A major 2005 study [$ub. req'd] led by NCAR climate researcher David Lawrence, found that virtually the entire top 11 feet of permafrost around the globe could disappear by the end of this century. Using the first "fully interactive climate system model" applied to study permafrost, the researchers found that if we somehow stabilize CO2 concentrations in the air at 550 ppm, permafrost would plummet from over 4 million square miles today to 1.5 million. If concentrations hit 690 ppm, permafrost would shrink to just 800,000 square miles.

A closer look at the argument for climate change underestimation

My previous post debunked an article that argued scientists have seriously overestimated climate change. Now let's look at the evidence for a serious underestimation of climate change.

To do that, we must understand the fatal flaw with the IPCC's over-reliance on the poorly named "equilibrium climate sensitivity" (ECS). Recall that the ECS is the "equilibrium change in global mean surface temperature following a doubling of the atmospheric (equivalent) CO2 concentration," which the IPCC's 2007 Fourth Assessment Report concluded was 2 to 4.5°C.

You might think that the ECS tells you how much the planet's temperature will rise if humans emit enough CO2 to double its atmospheric concentration. But it doesn't. It is just a theoretical construct. It tells you only how much the planet's temperature will rise if CO2 concentrations double and then are magically frozen.

That's because the ECS omits key carbon cycle feedbacks that a rise in the planet's temperature will likely trigger. For instance, a doubling of CO2 to 550 ppm will lead to the melting of the permafrost and the release of huge amounts of carbon currently frozen in it. These amplifying (or positive) feedbacks are the main subject of this post.

Read on

A study by Stephen Schwartz of Brookhaven National Lab, to be published in the Journal of Geophysical Research (JGR), has the deniers and doubters delighted.

"Overturning the 'Consensus' in One Fell Swoop" gloats Planet Gore, which says the study "concludes that the Earth's climate is only about one-third as sensitive to carbon dioxide as the IPCC assumes" and so we "should expect about a 0.6°C additional increase in temperature between now and 2070″ [0.1°C per decade] if CO2 concentrations hit 550 parts per million, double preindustrial levels.

Is this possible? Aren't we already warming up 0.2°C per decade -- a rate that is expected to rise? Has future global warming been wildly overestimated by the Intergovernmental Panel on Climate Change (IPCC) consensus?

Or, as I argue in my book, has future global warming been underestimated by the IPCC? This is perhaps the central issue in the climate change debate, so this will be a long post. To cut to the chase, it is not possible for one study to overturn the consensus, and in any case this inadequately researched, overly simplistic, and mistake-riddled study certainly doesn't.

Climate sensitivity expert James Annan points out key mistakes that rip the guts out of Schwartz's analysis. That is strike one. Now I'll offer my two cents.

Sea levels may rise much faster and higher than predicted

Popular Science has published a terrific article, "Konrad Steffen: The Global Warming Prophet," about one of the world's leading climatologists. Steffen has spent "18 consecutive springs on the Greenland ice cap, personally building and installing the weather stations that help the world's scientists understand what's happening up there." The article notes:

Water from the melting ice sheet is gushing into the North Atlantic much faster than scientists had previously thought possible. The upshot of the news out of Swiss Camp is that sea levels may rise much higher and much sooner than even the most pessimistic climate forecasts predicted.

What is going on in Greenland? Steffen explains what he and NASA glaciologist Jay Zwally figured out from their study of fissures in the ice sheet (called moulins -- see figures above and below):