Skip to comments.A sensitive matter (The Economist is stepping back from anthropogenic global warming!)
Posted on 04/01/2013 4:33:46 PM PDT by neverdem
OVER the past 15 years air temperatures at the Earths surface have been flat while greenhouse-gas emissions have continued to soar. The world added roughly 100 billion tonnes of carbon to the atmosphere between 2000 and 2010. That is about a quarter of all the CO₂ put there by humanity since 1750. And yet, as James Hansen, the head of NASAs Goddard Institute for Space Studies, observes, the five-year mean global temperature has been flat for a decade.
Temperatures fluctuate over short periods, but this lack of new warming is a surprise. Ed Hawkins, of the University of Reading, in Britain, points out that surface temperatures since 2005 are already at the low end of the range of projections derived from 20 climate models (see chart 1). If they remain flat, they will fall outside the models range within a few years.
The mismatch between rising greenhouse-gas emissions and not-rising temperatures is among the biggest puzzles in climate science just now. It does not mean global warming is a delusion. Flat though they are, temperatures in the first decade of the 21st century remain almost 1°C above their level in the first decade of the 20th. But the puzzle does need explaining.
The mismatch might mean thatfor some unexplained reasonthere has been a temporary lag between more carbon dioxide and higher temperatures in 2000-10. Or it might be that the 1990s, when temperatures were rising fast, was the anomalous period. Or, as an increasing body of research is suggesting, it may be that the climate is responding to higher concentrations of carbon dioxide in ways that had not been properly understood before. This possibility, if true, could have profound significance both for climate science and for environmental and social policy.
The insensitive planet
The term scientists use to describe the way the climate reacts to changes in carbon-dioxide levels is climate sensitivity. This is usually defined as how much hotter the Earth will get for each doubling of CO₂ concentrations. So-called equilibrium sensitivity, the commonest measure, refers to the temperature rise after allowing all feedback mechanisms to work (but without accounting for changes in vegetation and ice sheets).
Carbon dioxide itself absorbs infra-red at a consistent rate. For each doubling of CO₂ levels you get roughly 1°C of warming. A rise in concentrations from preindustrial levels of 280 parts per million (ppm) to 560ppm would thus warm the Earth by 1°C. If that were all there was to worry about, there would, as it were, be nothing to worry about. A 1°C rise could be shrugged off. But things are not that simple, for two reasons. One is that rising CO₂ levels directly influence phenomena such as the amount of water vapour (also a greenhouse gas) and clouds that amplify or diminish the temperature rise. This affects equilibrium sensitivity directly, meaning doubling carbon concentrations would produce more than a 1°C rise in temperature. The second is that other things, such as adding soot and other aerosols to the atmosphere, add to or subtract from the effect of CO₂. All serious climate scientists agree on these two lines of reasoning. But they disagree on the size of the change that is predicted.
The Intergovernmental Panel on Climate Change (IPCC), which embodies the mainstream of climate science, reckons the answer is about 3°C, plus or minus a degree or so. In its most recent assessment (in 2007), it wrote that the equilibrium climate sensitivity is likely to be in the range 2°C to 4.5°C with a best estimate of about 3°C and is very unlikely to be less than 1.5°C. Values higher than 4.5°C cannot be excluded. The IPCCs next assessment is due in September. A draft version was recently leaked. It gave the same range of likely outcomes and added an upper limit of sensitivity of 6°C to 7°C.
A rise of around 3°C could be extremely damaging. The IPCCs earlier assessment said such a rise could mean that more areas would be affected by drought; that up to 30% of species could be at greater risk of extinction; that most corals would face significant biodiversity losses; and that there would be likely increases of intense tropical cyclones and much higher sea levels.
New Model Army
Other recent studies, though, paint a different picture. An unpublished report by the Research Council of Norway, a government-funded body, which was compiled by a team led by Terje Berntsen of the University of Oslo, uses a different method from the IPCCs. It concludes there is a 90% probability that doubling CO₂ emissions will increase temperatures by only 1.2-2.9°C, with the most likely figure being 1.9°C. The top of the studys range is well below the IPCCs upper estimates of likely sensitivity.
This study has not been peer-reviewed; it may be unreliable. But its projections are not unique. Work by Julia Hargreaves of the Research Institute for Global Change in Yokohama, which was published in 2012, suggests a 90% chance of the actual change being in the range of 0.5-4.0°C, with a mean of 2.3°C. This is based on the way the climate behaved about 20,000 years ago, at the peak of the last ice age, a period when carbon-dioxide concentrations leapt. Nic Lewis, an independent climate scientist, got an even lower range in a study accepted for publication: 1.0-3.0°C, with a mean of 1.6°C. His calculations reanalysed work cited by the IPCC and took account of more recent temperature data. In all these calculations, the chances of climate sensitivity above 4.5°C become vanishingly small.
If such estimates were right, they would require revisions to the science of climate change and, possibly, to public policies. If, as conventional wisdom has it, global temperatures could rise by 3°C or more in response to a doubling of emissions, then the correct response would be the one to which most of the world pays lip service: rein in the warming and the greenhouse gases causing it. This is called mitigation, in the jargon. Moreover, if there were an outside possibility of something catastrophic, such as a 6°C rise, that could justify drastic interventions. This would be similar to taking out disaster insurance. It may seem an unnecessary expense when you are forking out for the premiums, but when you need it, you really need it. Many economists, including William Nordhaus of Yale University, have made this case.
If, however, temperatures are likely to rise by only 2°C in response to a doubling of carbon emissions (and if the likelihood of a 6°C increase is trivial), the calculation might change. Perhaps the world should seek to adjust to (rather than stop) the greenhouse-gas splurge. There is no point buying earthquake insurance if you do not live in an earthquake zone. In this case more adaptation rather than more mitigation might be the right policy at the margin. But that would be good advice only if these new estimates really were more reliable than the old ones. And different results come from different models.
One type of modelgeneral-circulation models, or GCMsuse a bottom-up approach. These divide the Earth and its atmosphere into a grid which generates an enormous number of calculations in order to imitate the climate system and the multiple influences upon it. The advantage of such complex models is that they are extremely detailed. Their disadvantage is that they do not respond to new temperature readings. They simulate the way the climate works over the long run, without taking account of what current observations are. Their sensitivity is based upon how accurately they describe the processes and feedbacks in the climate system.
The other typeenergy-balance modelsare simpler. They are top-down, treating the Earth as a single unit or as two hemispheres, and representing the whole climate with a few equations reflecting things such as changes in greenhouse gases, volcanic aerosols and global temperatures. Such models do not try to describe the complexities of the climate. That is a drawback. But they have an advantage, too: unlike the GCMs, they explicitly use temperature data to estimate the sensitivity of the climate system, so they respond to actual climate observations.
The IPCCs estimates of climate sensitivity are based partly on GCMs. Because these reflect scientists understanding of how the climate works, and that understanding has not changed much, the models have not changed either and do not reflect the recent hiatus in rising temperatures. In contrast, the Norwegian study was based on an energy-balance model. So were earlier influential ones by Reto Knutti of the Institute for Atmospheric and Climate Science in Zurich; by Piers Forster of the University of Leeds and Jonathan Gregory of the University of Reading; by Natalia Andronova and Michael Schlesinger, both of the University of Illinois; and by Magne Aldrin of the Norwegian Computing Centre (who is also a co-author of the new Norwegian study). All these found lower climate sensitivities. The paper by Drs Forster and Gregory found a central estimate of 1.6°C for equilibrium sensitivity, with a 95% likelihood of a 1.0-4.1°C range. That by Dr Aldrin and others found a 90% likelihood of a 1.2-3.5°C range.
It might seem obvious that energy-balance models are better: do they not fit what is actually happening? Yes, but that is not the whole story. Myles Allen of Oxford University points out that energy-balance models are better at representing simple and direct climate feedback mechanisms than indirect and dynamic ones. Most greenhouse gases are straightforward: they warm the climate. The direct impact of volcanoes is also straightforward: they cool it by reflecting sunlight back. But volcanoes also change circulation patterns in the atmosphere, which can then warm the climate indirectly, partially offsetting the direct cooling. Simple energy-balance models cannot capture this indirect feedback. So they may exaggerate volcanic cooling.
This means that if, for some reason, there were factors that temporarily muffled the impact of greenhouse-gas emissions on global temperatures, the simple energy-balance models might not pick them up. They will be too responsive to passing slowdowns. In short, the different sorts of climate model measure somewhat different things.
Clouds of uncertainty
This also means the case for saying the climate is less sensitive to CO₂ emissions than previously believed cannot rest on models alone. There must be other explanationsand, as it happens, there are: individual climatic influences and feedback loops that amplify (and sometimes moderate) climate change.
Begin with aerosols, such as those from sulphates. These stop the atmosphere from warming by reflecting sunlight. Some heat it, too. But on balance aerosols offset the warming impact of carbon dioxide and other greenhouse gases. Most climate models reckon that aerosols cool the atmosphere by about 0.3-0.5°C. If that underestimated aerosols effects, perhaps it might explain the lack of recent warming.
Yet it does not. In fact, it may actually be an overestimate. Over the past few years, measurements of aerosols have improved enormously. Detailed data from satellites and balloons suggest their cooling effect is lower (and their warming greater, where that occurs). The leaked assessment from the IPCC (which is still subject to review and revision) suggested that aerosols estimated radiative forcingtheir warming or cooling effecthad changed from minus 1.2 watts per square metre of the Earths surface in the 2007 assessment to minus 0.7W/m ² now: ie, less cooling.
One of the commonest and most important aerosols is soot (also known as black carbon). This warms the atmosphere because it absorbs sunlight, as black things do. The most detailed study of soot was published in January and also found more net warming than had previously been thought. It reckoned black carbon had a direct warming effect of around 1.1W/m ². Though indirect effects offset some of this, the effect is still greater than an earlier estimate by the United Nations Environment Programme of 0.3-0.6W/m ².
All this makes the recent period of flat temperatures even more puzzling. If aerosols are not cooling the Earth as much as was thought, then global warming ought to be gathering pace. But it is not. Something must be reining it back. One candidate is lower climate sensitivity.
A related possibility is that general-circulation climate models may be overestimating the impact of clouds (which are themselves influenced by aerosols). In all such models, clouds amplify global warming, sometimes by a lot. But as the leaked IPCC assessment says, the cloud feedback remains the most uncertain radiative feedback in climate models. It is even possible that some clouds may dampen, not amplify global warmingwhich may also help explain the hiatus in rising temperatures. If clouds have less of an effect, climate sensitivity would be lower.
So the explanation may lie in the airbut then again it may not. Perhaps it lies in the oceans. But here, too, facts get in the way. Over the past decade the long-term rise in surface seawater temperatures seems to have stalled (see chart 2), which suggests that the oceans are not absorbing as much heat from the atmosphere.
As with aerosols, this conclusion is based on better data from new measuring devices. But it applies only to the upper 700 metres of the sea. What is going on below thatparticularly at depths of 2km or moreis obscure. A study in Geophysical Research Letters by Kevin Trenberth of Americas National Centre for Atmospheric Research and others found that 30% of the ocean warming in the past decade has occurred in the deep ocean (below 700 metres). The study says a substantial amount of global warming is going into the oceans, and the deep oceans are heating up in an unprecedented way. If so, that would also help explain the temperature hiatus.
Lastly, there is some evidence that the natural (ie, non-man-made) variability of temperatures may be somewhat greater than the IPCC has thought. A recent paper by Ka-Kit Tung and Jiansong Zhou in the Proceedings of the National Academy of Sciences links temperature changes from 1750 to natural changes (such as sea temperatures in the Atlantic Ocean) and suggests that the anthropogenic global-warming trends might have been overestimated by a factor of two in the second half of the 20th century. It is possible, therefore, that both the rise in temperatures in the 1990s and the flattening in the 2000s have been caused in part by natural variability.
So what does all this amount to? The scientists are cautious about interpreting their findings. As Dr Knutti puts it, the bottom line is that there are several lines of evidence, where the observed trends are pushing down, whereas the models are pushing up, so my personal view is that the overall assessment hasnt changed much.
But given the hiatus in warming and all the new evidence, a small reduction in estimates of climate sensitivity would seem to be justified: a downwards nudge on various best estimates from 3°C to 2.5°C, perhaps; a lower ceiling (around 4.5°C), certainly. If climate scientists were credit-rating agencies, climate sensitivity would be on negative watch. But it would not yet be downgraded.
Equilibrium climate sensitivity is a benchmark in climate science. But it is a very specific measure. It attempts to describe what would happen to the climate once all the feedback mechanisms have worked through; equilibrium in this sense takes centuriestoo long for most policymakers. As Gerard Roe of the University of Washington argues, even if climate sensitivity were as high as the IPCC suggests, its effects would be minuscule under any plausible discount rate because it operates over such long periods. So it is one thing to ask how climate sensitivity might be changing; a different question is to ask what the policy consequences might be.
For that, a more useful measure is the transient climate response (TCR), the temperature you reach after doubling CO₂ gradually over 70 years. Unlike the equilibrium response, the transient one can be observed directly; there is much less controversy about it. Most estimates put the TCR at about 1.5°C, with a range of 1-2°C. Isaac Held of Americas National Oceanic and Atmospheric Administration recently calculated his personal best estimate for the TCR: 1.4°C, reflecting the new estimates for aerosols and natural variability.
That sounds reassuring: the TCR is below estimates for equilibrium climate sensitivity. But the TCR captures only some of the warming that those 70 years of emissions would eventually generate because carbon dioxide stays in the atmosphere for much longer.
As a rule of thumb, global temperatures rise by about 1.5°C for each trillion tonnes of carbon put into the atmosphere. The world has pumped out half a trillion tonnes of carbon since 1750, and temperatures have risen by 0.8°C. At current rates, the next half-trillion tonnes will be emitted by 2045; the one after that before 2080.
Since CO₂ accumulates in the atmosphere, this could increase temperatures compared with pre-industrial levels by around 2°C even with a lower sensitivity and perhaps nearer to 4°C at the top end of the estimates. Despite all the work on sensitivity, no one really knows how the climate would react if temperatures rose by as much as 4°C. Hardly reassuring.
Paul Ehrlich failed.
Al Gore failed.
Next up for the globalist control movement is; water.
Yadda, yadda, yadda.
Meanwhile, China alone is building dozens of new coal-fired electric power plants. There is really no evidence (which is admittedly different from evidence of absence) that CO2 has or will cause global climate change. If it doesnt, well and good - and if it does, well - it did. But there wasnt anything practical for us to have done about it in any event; that train left the station decades ago.But even if the climate changes, we, or our grandchildren, might have a post hoc ergo prompter hoc fallacy to debate.
But if theres one thing we do know, its that whether or not their warnings correspond to any reality at all or not, the people who are telling us that the sky is falling are acting in their own best interests by doing so. We also know that they presume that they can simply change the subject any time it becomes obvious that a prediction of theirs is groundless. And that fraud has been committed by scientists who wanted to sell the thesis that the sky is falling.
>>>Despite all the work on sensitivity, no one really knows how the climate would react if temperatures rose by as much as 4°C. Hardly reassuring.<<<
No one knows how the climate would react if temperatures stayed the same for the next century, either. It’s a dynamic system. Simply keeping the temperature the same, while the Earth’s orbit shifts and changes, and solar radiation rises and falls, would still mean that changes would happen that we can’t predict.
Despite the fearmongering, I can’t figure out how a warmer and wetter planet would be bad for people, either. (All the screaming about “drought” misses the point that severe global droughts last occurred at the height of the Ice Ages, when much of the water was taken up as ice in contintential glaciers. Warmer air holds more moisture.)
My own theory about all this - and much of the social sciences - is that we tend to see patterns in everything. It’s our nature. Even in places where no patterns exist. We’ve become so good at measuring every little nuance, every speck of group behavior and dynamics, every little molecule of air, that we’re imposing our own biases and beliefs on the patterns that data creates. Global warming is a great example of trying to extrapolate future trends from current data, but there are many more examples, from disparities in women’s and men’s pay to differences in statistics based on race to links between substance exposure and cancer. We love to find the pattern in everything. It’s a strength sometimes and a weakness, too.
God help us.
May God help us, but we must help ourselves when we can.!
Whether its title or its subtitle is A sensitive matter, this admission by The Economist that, "If climate scientists were credit-rating agencies, climate sensitivity would be on negative watch. But it would not yet be downgraded..." was the kind of story that I made a list for every state and then some.
It's been referenced by a few essays so far:
Michael Barone: The Economist's Emily Litella moment on global warming (Barone thought it was the title too.)
The Economist essay is worth the read and wide dissemination by email, not just a few echo chambers on the right. The Economist was always hawking global warming alarmism!
FReepmail me if you want off of my list.
AGW is a classic case of the correlation equals causation fallacy. The world started industrializing and dumping carbon into the air around 1850 and the Earth began warming about then. Therefore carbon caused the warming. They then began building computer models to "prove" their theory.
Only problem is the Earth is not acting per their models.
Then they jumped on the AGW bandwagon, which they never should have done. Looks like they are starting, ever so slowly, to get off.
This nonsense has been going on for almost 30 years. People need to start asking hard questions. Why has there been no significant warming for so many years? Where are the great seaports that were supposed to be flooded? Where are the small island nations that were supposed to dissappear? Where are the vast swaths of lost cropland in the Northern Hemisphere? Why have the predictions not come true? Why no reaction to the exposure of the Hockey Stick as a fraud? Why no reaction to the Climagate evidence of rigged "science"?
If mainstream publications like The Economist start asking these questions the tried and true response of calling the questioner names and screaming "settled" isn't going to satisfy them.
Put it all together, and as a professional meteorologist and a scientist, I will tell you what it means:
They do not know squat. They cannot predict the future out 1 month, 1 year, 10 years. Yet they want us to put all of the economic decisions of the world in their hands, because they have told us that the sky will fall if we do not.
A pure con game. Many wanted to believe their own con, and did. This is common. It is not excusable.
Our excessive emissions of CO2 should be drastically increasing global temperatures except that secret government agencies are seeding the clouds with reflective metals so sunlight bounces back into the upper atmosphere.
That's why all our kids are autistic, have asthma, and food allergies.
If only the lizard people from the 7th dimension would violate their prime directive and finally come down here and put a stop to all of this Illuminati-driven tinkering with our environment then we could get back on the road to sanity!
There was a science fiction story (Fallen Angels, by Niven and Pournelle) which had as part of the plotline that Earth was overdue for another Ice Age, and “global warming” was the only thing holding it off...
Oxymoron of the month.
Interesting that you would describe "climate science" as a "social science".
While it is nominally concerned with the study of physical effects, "climate science" is best described as a "social science" because it is actually driven by political agendae.
Thanks for the links
As far as I can tell, this is the only experimentally demonstrable aspect of "global warming." CO2 does have a rather wide absorption/emission band within the infrared portion of the spectrum (the exact wavelengths escape me for the moment). It is unusual, in that most fluorescence bands occupy far narrower portions of the spectrum. Its behavior as a fluorophore, however, is identical to the behavior of every other fluorophore: it absorbs a photon of light and emits it at a slightly lower energy (which equates to a slight increase in the wavelength). The remaining energy (that is not re-emitted) contributes to the kinetic energy of the molecule.
I have never seen any explanation of why or how the fluorescence of CO2 within that particular band has a more significant effect on atmospheric energy than the fluorescence of all the other gasses in the atmosphere, or even than the fluorescence of CO2 at other wavelengths. Nor have I seen any evidence to suggest that the peculiar behavior of CO2 stands out from the general fluorescent noise all around us.
The idea that CO2 could have a disproportionate effect on atmospheric temperatures is not one that is rigorously tested in a scientific manner. Its scientific basis lies in the fact that many people throw in the line "because of climate change" in papers about completely unrelated subjects.
Unfortunately, IMO, the idea that humans could effect climate change is one that fits into certain politicians' schemes very nicely. Trying to convince us to give up our freedom so they can have more power hasn't worked very well. But if they can convince us that all life on earth will go extinct unless we give up our freedom, they get what they want. So the (leftist power-hungry) politicians pick up on climate change, and they do choose the research they want funded. It's a rather unholy arrangement between politicians and scientists that should not exist. I'm not saying politicians shouldn't fund science--but that they should not set up a situation where you produce results they want (or say your results are what they want--they don't know the difference) or you don't get funded.
Oops, I did go on here. But "global warming" is one of my pet peeves--and you did ping me! < /soap box >