For years, readers of this site know that I have argued that:
- CO2 is indeed a greenhouse gas, and since man is increasing its atmospheric concentration, there is likely some anthropogenic contribution to warming
- Most forecasts, including those of the IPCC, grossly exaggerate temperature sensitivity to CO2 by assuming absurd levels of net positive feedback in the climate system
- Past temperature changes are not consistent with high climate sensitivities
Recently, there have been a whole spate of studies based on actual observations rather than computer models that have been arriving at climate sensitivity numbers far below the IPCC number. While the IPCC settled on 3C per doubling of CO2, it strongly implied that all the risk was to the upside, and many other prominent folks who typically get fawning attention in the media have proposed much higher numbers.
In fact, recent studies are coming in closer to 1.5C - 2C. I actually still think these numbers will turn out to be high. For several years now my money has been on a number from 0.8 to 1 C, sensitivity numbers that imply a small amount of negative feedback rather than positive feedback, a safer choice in my mind since most long-term stable natural systems are dominated by negative feedback.
Anyway, in an article that was as surprising as it is welcome, NY Times climate writer Andy Revkin has quite an article recently, finally acknowledging in the paper of record that maybe those skeptics who have argued for alower sensitivity number kind of sort of have a point.
“Worse than we thought” has been one of the most durable phrases lately among those pushing for urgent action to stem the buildup of greenhouse gases linked to global warming.
But on one critically important metric — how hot the planet will get from a doubling of the pre-industrial concentration of greenhouse gases, a k a “climate sensitivity” — someclimate researchers with substantial publication records are shifting toward the lower end of the warming spectrum.
By the way, this is the only metric that matters. All the other BS about "climate change" and "dirty weather" are meaningless without warming. CO2 cannot change the climate or raise sea levels or any of that other stuff by any mechanism we understand or that has even been postulated, except via warming. Anyway, to continue:
There’s still plenty of global warming and centuries of coastal retreats in the pipeline, so this is hardly a “benign” situation, as some have cast it.
But while plenty of other climate scientists hold firm to the idea that the full range of possible outcomes, including a disruptively dangerous warming of more than 4.5 degrees C. (8 degrees F.), remain in play, it’s getting harder to see why the high-end projections are given much weight.
This is also not a “single-study syndrome” situation, where one outlier research paper is used to cast doubt on a bigger body of work — as Skeptical Science asserted over the weekend. That post focused on the as-yet-unpublished paper finding lower sensitivity that was inadvisedly promoted recently by the Research Council of Norway.
In fact, there is an accumulating body of reviewed, published researchshaving away the high end of the range of possible warming estimates from doubled carbon dioxide levels. Chief among climate scientists critical of the high-sensitivity holdouts is James Annan, an experienced climate modeler based in Japan who contributed to the 2007 science report from the Intergovernmental Panel on Climate Change. By 2006, he was already diverging from his colleagues a bit.
The whole thing is good. Of course, for Revkin, this is no excuse to slow down all the actions supposedly demanded by global warming, such as substantially raising the price and scarcity of hydrocarbons. Which to me simply demonstrates that people who have been against hydrocarbons have always been against them as an almost aesthetic choice, and climate change and global warming were mere excuses to push the agenda. After all, as there certainly are tradeoffs to limiting economic growth and energy use and raising the price of energy, how can a reduction in postulated harms from fossil fuels NOT change the balance point one chooses in managing their use?
PS- I thought this was a great post mortem on Hurricane Sandy and the whole notion that this one data point proves the global warming trend:
In this case several factors not directly related to climate change converged to generate the event. On Sandy’s way north, it ran into a vast high-pressure system over Canada, which prevented it from continuing in that direction, as hurricanes normally do, and forced it to turn west. Then, because it traveled about 300 miles over open water before making landfall, it piled up an unusually large storm surge. An infrequent jet-stream reversal helped maintain and fuel the storm. As if all that weren’t bad enough, a full moon was occurring, so the moon, the earth, and the sun were in a straight line, increasing the moon’s and sun’s gravitational effects on the tides, thus lifting the high tide even higher. Add to this that the wind and water, though not quite at hurricane levels, struck an area rarely hit by storms of this magnitude so the structures were more vulnerable and a disaster occurred.
The last one is a key for me -- you have cities on the Atlantic Ocean that seemed to build and act as if they were immune from ocean storms. From my perspective growing up on the gulf coast, where one practically expects any structure one builds on the coast to be swept away every thirty years or so, this is a big contributing factor no one really talks about.
She goes on to say that rising sea levels may have made the storm worse, but I demonstrated that it couldn't have added more than a few percentage points to the surge.