Posted on 08/11/2007 12:40:50 AM PDT by neverdem
Climate scientists are used to skeptics taking potshots at their favorite line of evidence for global warming. It comes with the territory. But now a group of mainstream atmospheric scientists is disputing a rising icon of global warming, and researchers are giving some ground.
The challenge to one part of the latest climate assessment by the Intergovernmental Panel on Climate Change (IPCC) "is not a question of whether the Earth is warming or whether it will continue to warm" under human influence, says atmospheric scientist Robert Charlson of the University of Washington, Seattle, one of three authors of a commentary published online last week in Nature Reports: Climate Change.
Instead, he and his co-authors argue that the simulation by 14 different climate models of the warming in the 20th century is not the reassuring success IPCC claims it to be. Future warming could be much worse than that modeling suggests, they say, or even more moderate. IPCC authors concede the group has a point, but they say their report--if you look in the right places--reflects the uncertainty the critics are pointing out.
Twentieth-century simulations would seem like a straightforward test of climate models. In the run-up to the IPCC climate science report released last February (Science, 9 February, p. 754), 14 groups ran their models under 20th-century conditions of rising greenhouse gases. As a group, the models did rather well (see figure). A narrow range of simulated warmings (purple band) falls right on the actual warming (black line) and distinctly above simulations run under conditions free of human influence (blue band).
But the group of three atmospheric scientists--Charlson; Stephen Schwartz of the Brookhaven National Laboratory in Upton, New York; and Henning Rodhe of Stockholm University, Sweden--says the close match between models and the actual warming is deceptive. The match "conveys a lot more confidence [in the models] than can be supported in actuality," says Schwartz.
To prove their point, the commentary authors note the range of the simulated warmings, that is, the width of the purple band. The range is only half as large as they would expect it to be, they say, considering the large range of uncertainty in the factors driving climate change in the simulations. Greenhouse-gas changes are well known, they note, but not so the counteracting cooling of pollutant hazes, called aerosols. Aerosols cool the planet by reflecting away sunlight and increasing the reflectivity of clouds. Somehow, the three researchers say, modelers failed to draw on all the uncertainty inherent in aerosols so that the 20th-century simulations look more certain than they should.
Modeler Jeffrey Kiehl of the National Center for Atmospheric Research in Boulder, Colorado, reached the same conclusion by a different route. In an unpublished but widely circulated analysis, he plotted the combined effect of greenhouse gases and aerosols used in each of 11 models versus how responsive each model was to a given amount of greenhouse gases. The latter factor, called climate sensitivity, varies from model to model. He found that the more sensitive a model was, the stronger the aerosol cooling that drove the model. The net result of having greater sensitivity compensated by a greater aerosol effect was to narrow the apparent range of uncertainty, as Schwartz and his colleagues note.
"I don't want certain interests to claim that modelers are dishonest," says Kiehl. "That's not what's going on. Given the range of uncertainty, they are trying to get the best fit [to observations] with their model." That's simply a useful step toward using a model for predicting future warming.
IPCC modelers say they never meant to suggest they have a better handle on uncertainty than they do. They don't agree on how aerosols came to narrow the apparent range of uncertainty, but they do agree that 20th-century simulations are not IPCC's best measure of uncertainty. "I'm quite pleased with how we're treating the uncertainties," says Gabriele Hegerl of Duke University in Durham, North Carolina, one of two coordinating lead authors on the relevant IPCC chapter, "but it's difficult to communicate" how they arrived at their best uncertainty estimates.
Hegerl points out that numerical and graphical error ranges in the IPCC report that are attached to the warming predicted for 2100 are more on the order expected by Schwartz and his colleagues. Those error bars are based on "a much more complete analysis of uncertainty" than the success of 20th-century simulations, she notes. It would seem, as noted previously (Science, 8 June, p. 1412), IPCC could improve its communication of climate science.
They are not just “gazing at them”. They actively change “k” factors in the model to try to get them to fit what they think they should do. That is how these models work. There are so many factors that we cannot accurately measure, that they just assume a number, then try it. If it doesn’t give them what they want, they substitute another number. It is GIGO..Garbage In, Garbage Out.
No responsible researcher is denying that human activity is significantly influencing climate. They're simply unsure of the magnitude and direction of that influence.
Since none of the effects are intentional - they're the results of garbage spewed into the atmosphere by human attempts to get rich and powerful - I'd be very worried about what's coming.
Terrified.
So I guess nature is impossible to understand and science is worthless.
Fish are part of the environment. Weather affects the fish, their food supplies, and the humans who catch and eat them, along with all the other predators out there. Watch. Worry. Watch the government! Aside from the moments of absolute horror, you’ll also find quite a few moments of slapstick comedy...
“No responsible researcher is denying that human activity is significantly influencing climate.”
The problem is you use “responsible” to mean any quality that advances a socialist agenda; that is, any promotion of that which is antithetical to rational thought.
The temperature measurements that they take from airports in cities where there is a heat island effect (like Phoenix, Tucson or Fresno) distort the numbers further...
“So I guess nature is impossible to understand and science is worthless.”
No, part of science is knowing the limitations of what you can measure. Very little in nature is subject to accurate computer modeling. Some physics, such as Newtonian astronomy, does fairly well in limited scenarios because the number of variables are small and the equations governing the interactions are well known and tested.
This is not the case with extremely complicated systems where we do not know many of the interactions and the difference between a warming climate and a cooling climate can be the difference of a percent or less between many interacting factors that are difficult to measure.
We understand the basic gas laws very well, and we can model the expansion of a gas under a number of situations quite well. But, when you have a mixture of gases in a natural (not controlled) environment, with numerous variable such as cloud cover, water vapor interaction with the surface, including plants, variable solar radiation and variable albedo of the surface, computer models only give us a glimpse of how things may work together. They are worthless for forecasting far into the future.
We simply do not know enough to do so. There are too many interactions involving unknown feedback loops where what we are interested in is the balance between large numbers that we cannot measure well.
Terrified.
Remains of 8000 year old Stone Age settlement found under English Channel
Comment# 1:
"No SUVs or smokestacks, how can this be true?"
Man, get a grip on yourself.
I'm just using the article. Are any of the researchers denying human influence in climate change? No. So where do you find such? In Bible-thumping 1? In paleo-capitalism 101?
The other part is making educated - and very, very, clever - guesses. Both Copernicus and Einstein did that...and look where it's got us.
Look, we are - unquestionably - radically altering our environment, and one of the ways we're doing so is by tossing vast amounts of garbage, much of it known to be dangerous to life, into the atmosphere. It's only reasonable to try to gain a better understanding of the consequences.
Unfortunately, that might have unfortunate consequences for those who are doing the dumping and those who profit from the activities which generate the garbage. And there are those who would like to stop those activities for other reasons - because they are not profiting, because they are jealous of those who are. And there are those who are antagonistic to those who would like to stop the activities for their own reasons.
So politics rears its ugly head.
How can it be true that climate can change without mans influence and that climate can change due to mans influence? How is it possible for both Chevys and Fords to be automobiles which work?
If you want to return to living in the stone age, be my guest. IMHO, you need some healthy scepticism via Freeman Dyson.
BTW, the climate modelers are are playing games, if not engaging in fraud.
What do you think when they modify data, and don't reveal methods?
I don't want to return to the Stone age. We are simply of different minds about how to avoid it.
BTW, the climate modelers are are playing games, if not engaging in fraud.
Nah.
There're struggling to understand some very difficult stuff. Some, of course, are not very good, others exagerate the importance of their findings...the usual stuff.
Bullsh**.
I'd be very worried about what's coming.
Then buy Lurkers Cut Rate Carbon Credits and go back to sleep.
L
Until they do it's the height of folly to demand that several hundred million people change their lifestyle in order to avoid some imaginary hobgoblin they can't even prove exists.
Pssst. Buddy. Can you spare a carbon credit?
The best NOAA and NWS meteorologists the world has ever seen flat out refuse to make forecasts any farther than a week out. Yet we are supposed to believe that this bunch of 'climatologists' are able to accurately foretell global climactic conditions a hundred years hence?
If you believe that, I've got a bridge I'd like you to take a look at.
L
You could be speaking of a natural oscillation in North Pacific ocean temperatures called the Pacific Decadal Oscillation. Consider this scientific paper:
http://www.atmos.washington.edu/~mantua/REPORTS/PDO/pdo_paper.html
The popular press habitually mis-attributes the effects of the ongoing intensely positive phase of the Pacific Decadal Oscillation in Alaska to “global warming.” This oscillation has run positive since flipping circa 1977; it earlier flipped to negative circa 1942, so its period is obviously quite long.
Let's have some names.
Until they do it's the height of folly to demand that several hundred million people change their lifestyle in order to avoid some imaginary hobgoblin they can't even prove exists.
Sorry, no. This is a situation where you might be damned if you do, and might be damned if you don't.
Consider the investing analogy. If you only invested in sure things you wouldn't invest at all. In that case you would almost certainly lose your fortune to inflation, living costs, and unexpected events.
The best...meteorologists...refuse to make forecasts any farther than a week out. Yet we are supposed to believe that ...'climatologists' are able to accurately foretell global climactic conditions a hundred years hence?
You bet.
Meteorologists have no trouble predicting that winter will follow summer 100 years from now...and that winters will be colder than summers. Also that days will be hotter than nights, it will be warmer at the equator than at the poles, etc. etc.
Think about it.
Discovery Channel stopped by my house to see if we had any GW effects on our permafrost. Don’t know about GW effects, but we sure have the usual permafrost manifestations. Showed them where to look, about a mile down the road where a nice ranch house sank into the ground one end first like the Titanic.
Not even close my friend. I work quite closely with the NWS and NOAA geeks and to a man they deride this 'global warming' claptrap as ignorant vodoo peddled universally by frauds and hucksters.
Think about it.
I have. You should try it. It'd be a refreshing change from swallowing Al Gores crap.
L
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