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Is climate science settled? Especially the important parts?

Posted on 4 September 2010 by James Wight

Skeptics often claim that the science of anthropogenic global warming (AGW) is not “settled”. But to the extent that this statement is true it is trivial, and to the extent that it is important it is false. No science is ever “settled”; science deals in probabilities, not certainties. When the probability of something approaches 100%, then we can regard the science, colloquially, as “settled”.

The skeptics say that results must be double-checked and uncertainties must be narrowed before any action should be taken. This sounds reasonable enough – but by the time scientific results are offered up to policymakers, they have already been checked and double-checked and quintuple-checked.

Scientists have been predicting AGW, with increasing confidence, for decades (indeed, the idea was first proposed in 1896). By the 1970s, the scientific community were becoming concerned that human activity was changing the climate, but were divided on whether this would cause a net warming or cooling. As science learned more about the climate system, a consensus gradually emerged. Many different lines of inquiry all converged on the IPCC’s 2007 conclusion that it is more than 90% certain that anthropogenic greenhouse gases are causing most of the observed global warming.

Some aspects of the science of AGW are known with near 100% certainty. The greenhouse effect itself is as established a phenomenon as any: it was discovered in the 1820s and the basic physics was essentially understood by the 1950s. There is no reasonable doubt that the global climate is warming. And there is also a clear trail of evidence leading to the conclusion that it’s caused by our greenhouse gas emissions. Some aspects are less certain; for example, the net effect of aerosol pollution is known to be negative, but the exact value needs to be better constrained.

What about the remaining uncertainties? Shouldn’t we wait for 100% certainty before taking action? Outside of logic and mathematics, we do not live in a world of certainties. Science comes to tentative conclusions based on the balance of evidence. The more independent lines of evidence are found to support a scientific theory, the closer it is likely to be to the truth. Just because some details are still not well understood should not cast into doubt our understanding of the big picture: humans are causing global warming.

In most aspects of our lives, we think it rational to make decisions based on incomplete information. We will take out insurance when there is even a slight probability that we will need it. Why should our planet’s climate be any different?

This post is the Basic version (written by James Wight) of the skeptic argument "The science isn't settled".

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Comments

Comments 1 to 29:

  1. Given the lives in the balance, it would seem to me that the deniers should be required to prove their allegations that AGW is false, and that their "proof" should be beyond a shadow of a doubt. After all, it is their premeditated obstructionism that will contribute to the suffering of millions.
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  2. Heads up - Ice caps in Greenland and West Antarctica melt is not as hard as thought 02 september 2010 door M&C September 2, 2010 by M & C http://translate.google.com/translate?js=n&prev=_t&hl=nl&ie=UTF-8&layout=2&eotf=1&sl=nl&tl=en&u=http%3A%2F%2Fwww.tudelft.nl%2Flive%2Fpagina.jsp%3Fid%3D7a6c3d15-1c1e-4869-b378-840a000c6803%26lang%3Dnl
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  3. But, but... "...And I’m going to show you the latest science, which now doesn’t leave the question unsettled anymore this is now settled science, it is now settled science that there is not a problem with our influence over Climate. The science is in, the truth is out and the scare is over.” -- Christopher Monckton. 10/14/9 Minnesota Free Market Institute presentation H/T to Citizen's Challenge
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  4. Global warming is settled, the why is not.
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  5. Re. 6 MattJ. I thoroughly agree.
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  6. Colorado Bob at 00:23 AM on 5 September, 2010 Thanks for that link. The various GRACE estimates of mass loss are known to disagree (sometimes by significant factors) due to the relatively short time series, and this paper looking at GIA correction is actually in line with other recent GPS based work. However all trend estimates show unquestionable significant mass loss and acceleration of loss. Better absolute estimates of this loss are important for the sea level budget, but do not change the mean sea level rise measurements.
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  7. One interesting resource on the "when did we know CO2 was bad" topic is the 1965 report to US President Johnson. The appendix that refers to CO2 is: http://bit.ly/dvbtRN (That's a link to a PDF in a public folder in my DropBox account.)
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  8. "Just because some details are still not well understood should not cast into doubt our understanding of the big picture: humans are causing global warming." One can look at this from another angle-the skeptical one (since this site is supposed to be about skepticism). Most of the history of the world has been about exploiting uncertainties for power. Nations go to war based on it. Religions and ideologies arise from the fear of it, and totalitarian regimes attempt to wipe it from the face of the earth. Exploiting uncertanties in climate is nothing new to the 20-21st centuries. Most of the ancient religions stumbled on the idea that you can exploit the fear and uncertainties regarding projected climate/weather (floods, droughts etc) for power. Why do you think humans were ever sacrified to a Sun God?. It is essentially about replacing uncertainty of future climate with a false certainty about future climate, whilst at the same time eliminating dissent -either real dissedents or simply 'potential' dissedents- by a formalised ritual tradition. Sound too extreme? Thousands of people per year were sacrificed in Central and South America (notably-in areas prone to climate swings and El Nino-La Nina) to serve a political structure based on fear and uncertainty surrounding climate. Spanish conquistadors found 100's of thousands of skulls sacrificed simply for the sake of exploiting fear of climate and climate projections, and to eliminate dissent, and doubt, of a political system built on false climate certainties. In the common case of sacrificing young female virgins, this also served the purposes of male patriarchy, but it was ultimately and largely for reasons of personal and class-based power. Nothing more. Climate scientists are not going to fool skeptics with this possible recent revival of an old-age trick-denying and using uncertainty in the Earth's climate and weather as a means to social control. A completely opposite way of looking at it (the skeptical one, by the way), is that you should actually never 'cast aside' one's 'doubt of climate science'; such is the road to ideology, blind faith, and false certainty as a means to social power and control. The Aztecs and Mayans discovered it, and now 21str century ‘scientists’ have discovered it (but not the sceptical ones). If you think this view is extreme, take a look at human history, or ask anyone who has actually ived under a totalitarian regime. They don’t take their scepticism lightly. Jacob Bronowksi was very clear in his conclusions about human history in his infamous 'Ascent of Man' series and book; if history teaches us anything, its that humans should never be too sure of themselves.
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  9. I live with uncertainty routinely, and so do you. I pay my insurance, I do up my seatbelt, I wear sunscreen, I had children, I buy garden plants. I do not understand these problems with certainty and / or uncertainty. We are living beings surrounded by other living things as well as lots of other people. This is all uncertain, and crossing the road is risky - but I manage this by obeying road rules and keeping my eyes open, as I'm sure you do. My "doubt" about climate science is the same as most people's. Don't know the size or the direction of the uncertainties. But not knowing the timing or the extent of possible storm damage to my house doesn't stop me from paying the insurance premium.
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  10. jdsykes, the burden of proof is always on the proponent, not the skeptic. However, the proponents of AGW have well and truly met the burden of proof; otherwise the scientific community would not be convinced. Some of the evidence that convinced scientists is discussed here and here. thingadonta, did you actually read my post? I wrote: “Science comes to tentative conclusions based on the balance of evidence. The more independent lines of evidence are found to support a scientific theory, the closer it is likely to be to the truth.” This is very different to the way that religions arrive at conclusions. Religious “truth” is based on authority and revelation and myths, whereas AGW is based on scientific evidence. Religious dogma is usually asserted to be absolutely certain, regardless of what empirical evidence might say. Scientific conclusions are not dogmatic; for example, the IPCC acknowledges there is a possibility that global warming is not anthropogenic. AGW is not a religion.
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  11. Thingadonta You say " Most of the history of the world has been about exploiting uncertainties for power". Like the oil companies / corporates regarding climate change for example?
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  12. Thingadonta, there is a qualitative difference between science and the "exploitation of uncertainties" you describe, and for once I'd like to see you actually admit that you're capable of learning (being a skeptic is pointless otherwise). It would make many here much more willing to be patient with you. In addition to what James Wight has said, understand that science--unlike any of the other practices you mentioned--is completely open about what it doesn't know. That is, in fact, the opposite of those historical 'exploitations'. The rich and powerful sought (and still seek) to control what is known and unknown by hiding their uncertainty behind a convenient "truth." Once truth is claimed, science has stopped. But you keep looking for certainty. I suggest you find a church, because you won't get it in science. You will, however, get people who are willing to act on a certain level of probability. There is a high probability that AGW is occurring. That probability, according to the people who have dedicated their lives to studying climate (and who definitely wish they were wrong, for a number of reasons), is much higher than any other scenario for the near future. Given the evidence, and looking at the math, I agree. Certainty in science doesn't mean the discovery of absolute truth; it means reaching the point of willingness to act. With climate change, I'm there. With C-section vs. natural birth for twins, I'm still not sure, and I only have a few months to figure it out and may not even then, but I'll be forced to act. Something tells me that even if we get 10 C warming in the next 20 years, you'll still be like, "It has to be something else. Couldn't possibly be AGW." I've asked this of others: what would be convincing evidence of AGW? What would it look like to you? Btw, you do manage to actually act, don't you? Even in the midst of the storm of uncertainty and doubt that is your life?
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  13. J Bowers I hope you are being fectitious, quoting Monckton. If not, are you questioning the validity of science agreed on by 97% of climate scientists and virtually every major scientific organization in the world, and then offering Monckton as proof they are all wrong? You must be kidding. I'm sure a journalist with no science background, who claims to have invented cures for all kinds of diseases, and who tells you the earth is cooling and then tells you, the warming is due to something other than greenhouse gases, and then tells you not to worry because global warming will be benficial, is a better source than all those scientists.
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  14. Okay, see how the title says the science isn't settled, the plastic sceptics say the alarmists say it is settled, yet Monckton says it is settled as well... It's ironic. Maybe I should have been explicit about it, but I'd have thought my stating that I agree with MattJ would have helped you figure that one out. Try the link I posted to Citizen's Challenge.
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  15. jbowers: you nailed the deniers position very well: the science isn't settled, unless it's their science.
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  16. @thingadonta #8 To summarize your viewpoint: you can never be sure about anything. Indeed. You can never be sure that tomorrow the laws of thermodynamics will still apply or that the sun will still rise in the east. Indeed. And you cannot eliminate this uncertainty by doing irrational things like sacrificing people. Indeed. You then suggest that this is the same as what climate scientists try to do: to take away the uncertainty with irrational hocus-pocus. That’s where you’re wrong. No science is ever completely settled. Science strives to minimize the uncertainty but a 100% certainty is not achievable. Nevertheless, in the past this hasn’t stopped us from using the laws of thermodynamics to construct cars and power plants, using the laws of electromagnetism to build cellphones, using the laws of mechanics to launch space ships. I never heard anyone demanding that the science should be settled for a 100% before using this knowledge. If we had waited, we would still be living in caves. Using the knowledge you have to your best advantage (taking into account the uncertainty that still exists) is not irrational. It is the best we can do. We don’t know absolutely everything about climate science. We know enough to act. That’s the message climate scientists try to get across.
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  17. Thingadonta @8 Jacob Bronowksi was very clear in his conclusions about human history in his infamous 'Ascent of Man' series and book; if history teaches us anything, its that humans should never be too sure of themselves. Ahh, the truth is out - Climate change deniers are not human ! Perhaps they are alien beings from a hot planet planning to invade us... :-)
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  18. thingadonta wrote : "Climate scientists are not going to fool skeptics with this possible recent revival of an old-age trick-denying and using uncertainty in the Earth's climate and weather as a means to social control. A completely opposite way of looking at it (the skeptical one, by the way), is that you should actually never 'cast aside' one's 'doubt of climate science'; such is the road to ideology, blind faith, and false certainty as a means to social power and control. The Aztecs and Mayans discovered it, and now 21str century ‘scientists’ have discovered it (but not the sceptical ones)." These are very skewed comments(politically and scientifically), which reveal a lot more about you and your beliefs than about global warming itself. Politically, you seem to see "social power and control" as an inherent desire of scientists and others involved with research into global warming. Apart from the "skeptics", of course - whoever they might be and however you define them, beyond your belief that anyone who doesn't like or accept global warming must, by default, be a skeptic. That would seem to include everyone from Monckton to Lindzen, and every position from 'It's all a UN, secret government conspiracy' to 'The Greenhouse theory is false' to 'Maybe the effects won't be quite so serious as some suggest'. All skeptics/skeptical but few worthy of being taken seriously. With regards to the science, you have no answers or rebuttal and can only denigrate and belittle what you define as 'scientists', who are, again, all those apart from the "skeptical" ones you like. Again, they are undefined by you and so, presumably, run the gamut from Gerlich/Tscheuschner to Singer to Lindzen. They you would no doubt call scientists without the qualifying quote marks; the rest you smear by association. I find that reprehensible and snide but you are somehow allowed to make such assertions without ever backing up your beliefs. Shameful but very revealing of your motivations, beliefs and lack of serious credibility.
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  19. First, why is anyone taking thingadonta seriously? Come on, people. Climate scientists are the equivalent of Aztec or Mayan priests sacrificing thousands of people? The goal of climate science is world domination? It's funny. Second, why didn't the moderator delete that post? It has zero science content, is off-topic, and entirely political. If it's real, it's evidence of a paranoid psychosis, and if it's fake, it's pure trolling. Either way, it has no place here.
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  20. thingadonta wrote: A completely opposite way of looking at it (the skeptical one, by the way), is that you should actually never 'cast aside' one's 'doubt of climate science'; such is the road to ideology, blind faith, and false certainty as a means to social power and control. The Aztecs and Mayans discovered it, and now 21str century ‘scientists’ have discovered it (but not the sceptical ones). The pre-Columbian peoples of America did not have "blind faith" in their religions - they followed them because they seemed to work. They offered sacrifices, the Gods responded with rain, good crops and victory in war. A year of drought could be cured by more sacrifices, and the Gods would be appeased. Unfortunately, the series of good years were accompanied by expansion in populations and farming (slashing and burning hill areas, for example) that were unsustainable in prolonged periods of drought. These were followed by revolutions, overthrow of the city elites, population collapse, desertion of the large cities, and (sometimes) mass murder and cannibalism. These societies were essentially conservative, led by elites who aggrandized themselves with buildings, temples, expanded populations for bigger armies and personal display. If there were a few Mayan radicals they might have said "We have enough large temples - let us build granaries to store grain and resevoirs to retain water. Let us limit our wars to defence only. Instead, we should be limiting our population growth and ensuring our agriculture is sustainable. We know from history this region endures catastrophic droughts every few centuries - let us plan to mitigate those because one will surely happen, maybe in the times of our children or grandchildren." The elites would have replied "The Gods will punish us if we do not build larger temples. Other cities will have bigger temples, and the Gods are fickle. We need a bigger population to provide us with the young men to fight and win wars to bring back slaves to build those temples. And droughts? If we please the Gods, they will not punish us with droughts. We must expand our agricultural base to please the Gods and our wise rulers." Which one was exercising "social power and control"? Which one was offering the solution most likely to work in the long term?
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  21. IMHO, the predictive skill of the climate models have not been formally and empirically demonstrated (as in IV&V). I am not sure if this should be considered a "The Science Is Settled" issue or not. Besides sensitivity studies, the models are primarily used as the basis of political policy -- not the thrust of this blog, of course. If the topic seems interesting, there has been a recent discussion on the current adequacy of verification and validation of the models here. For example, Dr. Steve Easterbrook argues there that conventional IV&V for the climate models may well be meaningless.
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  22. gmcrews, I suggest you read Steve Easterbrook's recent post, "I Never Said That!"
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  23. Hi Tom (#22): Thanks for the suggestion. But the entire post is based on a quote I took out of that exact post by Easterbrook. Should I aver that I did not stop reading when I got to that quote in the post? Or that I subscribe to Dr. Easterbrook's blog? I would be glad to discuss the merit of Argument From Authority to decide if IV&V for climate codes is meaningless. George
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  24. That's strange, George--I don't see the quote you say you took. However, I suggest the best venue for discussion of this particular topic is in the comments section of your blog, where Steve Easterbrook himself has responded well.
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  25. Adelady: I'm glad you pay insurance. Most of us pay some form of insurance - we rarely view ourseloves as winners when we get an insurance payout. I guess some have issues about the costs of some proposed premiums.
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  26. Article asks... "Shouldn’t we wait for 100% certainty before taking action?" What would define "taking action"?... or rather, how much action, (and what actions) would be enough action? ...no matter how much action is taken, there will always be those clamoring that not enough action is being taken, that and a never ending stream of scientific papers to back up these claims...
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  27. RSVP, there will always be people clamoring for some kind of action on everything that goes on in the world. But if we were to take action that significantly reduced the risks posed by climate change, it would be the science that would tell us that the risks were reduced.
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  28. CBW If the science is "good enough", it should be able to quantify the trade offs and make clear exactly what action is needed. In fact, if the science is so advanced, peers should produce a chart that has "ocean rise cm" vs. "action", where "action" quantifies how much GHG needs to be cut back. If you are aware of this "recipe", please let me know. Thanks in advance.
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  29. RSVP, this is what I mean about not living in a world of certainties. For climate modelers to be able to do what you suggest, they’d have to exactly quantify the various feedbacks and time-lags at each stage of the process. I don’t think it’s reasonable to expect that from science. However, the IPCC does model the range of possible temperature rises for a range of possible emissions scenarios (the scenarios having been defined in a previous report). See this page from the Summary for Policymakers. Under the best-case B1 scenario, global temperatures are projected to rise 1.1-2.9°C. In the worst-case A1FI scenario, the temperature rise is 2.4-6.4°C. The large error bars are because of lingering uncertainties to do with cloud feedbacks and so on. The same table also includes numbers for sea level rise as well, but bear in mind these do not take into account the contribution from ice sheets. More recent models which do include ice sheets predict around one to two metres of sea level rise over the next century. Projecting future climate change is probably the most uncertain aspect of climate science. But I would still argue that these uncertainties shouldn’t be used to justify inaction. The prognosis might well be better than we currently think, but it is equally likely to be worse than we think.
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