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Comments 45501 to 45550:
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JvD at 20:04 PM on 16 May 2013A Detailed Look at Renewable Baseload Energy
@Tom Curtis. you wrote:
"1) Fail safe design, so that in the complete breakdown of power supply and or mechanical systems the reactor shuts down safely; and
2) No net environmental impact for ore to waste. The idea here being that uranium ore is a naturally occuring low level environmental hazard. That fact allows a straightforward definition of safe disposal of nuclear waste. That is, if radiation count at the surface of a waste disposal site is no greater than at the original ore body, and the waste is stored in a way that is proof to leeching and as expensive to reprocess as the original ore, then waste disposal has no net environmental impact and can be considered safe.
Do you agree that these are reasonable constraints on the nuclear industry?"
I agree. Furthermore, these constraints should count for all energy industries. What we need is a level playing field. So if there is for example a gas pipeline break that kills people (which happens all the time, in all countries using natural gas) then clearly all natural gas pipelines worldwideneed to be shut down immediately until there is a thorough review of their safety, and full list of recommendations to improve safety to the minimum level of nuclear power, just as what was done in Japan and Germany after Fukushima. Otherwise there is no level playing field. It won't do to consider deaths due to natural gas explosions, wind turbine blade tossing, people falling of their roofs while cleaning solar panels, etc as somehow different from deaths due to radiation accidents. All these deaths are known and they should be treated equally.
Concerning the safe storage of wastes, we know from the Oklo uranium deposits (which contain numerous natural nuclear reactors) that radioactive products from nuclear fission are contained by such geologies. So returning HLW to such mines is a first indication that safe storage of fission products is easy and in existence. We can engineer storage facilities that are even better than the naturally occuring nuclear waste storage sites that have been found at Oklo, but it is nonsense to suppose that 'there is no solution to nuclear waste' Clearly, there is. Even nature itself - with no engineered radiation barriers - does a very good job.
Concerning fail-safe reactor esign. The modern AP1000 and EPR NPP's contain many of such features. Most 4th generation reactor design are even safer still, because they don't rely on passive, non-energised safety systems, but rather on reactor physics that require no safety systems at all, passive or active.
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Kevin C at 19:52 PM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
JRT256:
So, I was curious as to how the study would classify a paper which stated either that we don't know how much of the warming was caused by human activity or that stated a percentage which was less than 50% of it as being caused by human activity.
A 'we don't know' paper would be counted as taking a position but uncertain (category 4b). A 'less than 50%' paper would be counted as an explicit rejection of the consensus (category 7).
Ed Davies:
One question, how would a paper which accepted the basic chain of human emissions -> more CO₂ in the atmosphere -> warming -> positive feedbacks (water vapour, etc) but then proposed that there were large negative feedbacks which cancel out most of the effect be counted?
You would have to look in the database for the answer on individual papers - the study criteria were based on past warming. Low sensitivity has implications for past warming. Is depends how this is handled in the abstract (or the paper for self ratings).
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Kevin C at 19:45 PM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
JRT256: Your post raises several distinct questions, which need separate answers.
The study examined the abstracts of 12,464 papers and about a third of them endorsed the fact that humans are causing global warming. Yet the papers conclusing is that there is a 97% consensous. I am sorry, but that just doesn't make sense.
Firstly, only a third of the abstracts stated a position on whether mankind was the principle cause of recent warming. However the author self-ratings, based on the whole paper, increased this proportion to two thirds.
Secondly, the paper is very clear that the 97% consensus is among papers which stated a position.
Finally, your confusion is based on a false assumption that every paper which mentions global warming is trying to test whether global warming is occuring and is man made. But many papers with the appropriate keywords in the title only deal with parts of the question. For example a paper on measuring the global warming signal in the instrumental temperature record may say nothing about the cause. Thus it is expected that a significant proportion of the papers will have no position on the question. Including such papers is as meaningful as including all the papers on the colours of butterfly wings.It sounds to me like most papers are scientifically proper and did not take a postition on political issues.
Whether human activity is causing the majority of recent warming is not a political question, it is a scientific question. The question 'what should we do about it' is a political question.
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Ed Davies at 19:41 PM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Excellent work. One question, how would a paper which accepted the basic chain of human emissions -> more CO₂ in the atmosphere -> warming -> positive feedbacks (water vapour, etc) but then proposed that there were large negative feedbacks which cancel out most of the effect be counted? I'm thinking of the UAH guys and Richard Lindzen who, as I understand things, have views like this.
(Read this article and your Guardian post but not the main paper - sorry if this is covered in the paper.)
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Dikran Marsupial at 19:18 PM on 16 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Dr Tung I'm sorry, but you have not answered my question. It may be your opinion that there is a systematic underprediction by the CMIP3 models, but if you want others to agree with your opinion you need to be able to provide adequate justification for that opinion.
As scientists (I am also a scientist) we do indeed pay special attention to the systematic discrepancies between model and observation; however as scientists we should not stop at observing a visual discrepancy. The human eye is rather too good at seeing "systematic features" in signals where in reality there is only noise, which is why we have statistics to provide an objective test for our hypotheses (even if only a sanity check). So at the very least, a scientist should determine whether there is adequate evidence that the apparent discrepancy actually is systematic, rather than being merely an artefact of the noise (in this case internal unforced climate change). My question was intended to help you to explain the evidence for a systematic discrepancy, and so far you have provided none. I still have an open mind on this, but I require evidence.
Note I wouldn't go as far as to say that the models give good hindcasts of 20th century climate (in absolute terms), just that their hindcasts are as accurate as we have reason to expect. If someone can show that the plausible magnitude of the effects of unforced internal variability is substantially smaller than the spread of the model runs, then there may be an argument that the accuracy of the hindcasts falls below that we could reasonably expect. The problem is that we have only one realisation of the observed climate, with ever changing forcings, so it is difficult to see how we can estimate the magnitude of unforced internal variability without using models in much the way they are currently used.
At the end of the day, there needs to be an element of self-skepticism in good science, in this case, the null hypothesis should be that the apparent discrepancy is due to internal variability and the onus is on yourself to demonstrate that this is implausible, as it is your claim that a systematic discrepancy exists. That is conventional scientific practice.
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Rob Painting at 19:16 PM on 16 May 2013Another Piece of the Global Warming Puzzle - More Efficient Ocean Heat Uptake
R Gates - There are two aspects to ocean warming; increased greenhouse gas content of the atmosphere warms the cool-skin layer of the ocean and lowers the thermal gradient through that layer. Less heat (from sunlight) leaves the ocean and the surface ocean grows warmer over time. That's why the oceans are warming despite a reduction in solar radiation over the last 3 decades.
Secondly; the oceans are not passive. They have changed in response to warming, and also have a large natural variability component. Were this not so, only the surface oceans would warm, the surface layers would stratify, and surface warming would be occurring much faster than it is. The recent acceleration of ocean heat content is exaggerated due to the negative phase of the Pacific Decadal Oscillation happening on top of the long-term ocean warming trend. At some stage we are likely to see a return to the positive phase - so ocean warming will slow down.
Current observations are consistent with paleodata from warm intervals in Earth's ancient past. The equator-to-pole and, surface-to-deep ocean temperature gradients were reduced when compared to modern-day. This implies stronger transport of heat to the deep ocean and polar oceans than is going on today, and suggests the observations are tracking in that direction.
I believe a lot of the confusion stems from readers not understanding how the oceans really operate - Coriolis Effect, ocean gyres, Ekman transport, and so on. Working on fixing that.
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JRT256 at 19:15 PM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
I am trying to get this straight. The study examined the abstracts of 12,464 papers and about a third of them endorsed the fact that humans are causing global warming. Yet the papers conclusing is that there is a 97% consensous. I am sorry, but that just doesn't make sense. It sounds to me like most papers are scientifically proper and did not take a postition on political issues.
IAC, the issues in the anthropogenic global warming hypothesis are considerably more complex than just yes or no. This has become even more the case in the last few years as the earth's average surface temperature doesn't seem to increase -- at least for now. This will clearly result in more papers trying to explain this fact on subjects such as climate sensitivity, as well as whether or not CFCs caused more warming than originally thought, radiation of heat into space as earth's effective temperature increases, and whether the saturation of absorption of EMR by CO2 in the atmosphere actually fits the logrithmic curve. Papers on these subjects as well as recent ones already publised on water vapor feedback will be the interesting ones and they may not be found by a survey such as this.
I also note that it is clear that some global warming has clearly been caused by human activity. So, I was curious as to how the study would classify a paper which stated either that we don't know how much of the warming was caused by human activity or that stated a percentage which was less than 50% of it as being caused by human activity. -
MarkR at 19:15 PM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
I think it's important to remember the specific question we asked: are we causing most recent global warming?
Logically, this means there is also a strong consensus that the rise in CO2 is man-made, the greenhouse effect is real etc. The 'skeptics' that say otherwise are backed up by basically no research that was good enough to pass peer review.
The evidence for man-made global warming is far too strong to throw out, but on some of the other details we might find more interesting answers if we get the chance to expand this sort of analysis.
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cRR Kampen at 17:42 PM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Zapped onto CNN this morning (local Dutch time) to find John Cook talking to me about this survey, great :)
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MS1 at 16:32 PM on 16 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Dear Prof Tung,
thank you for this impressive posting and the valuable comments. As you mentioned Rahmstorf/Forster, I think their paper failed due of the assumption that the ENSO index is linear to the global temperature effect of the ENSO process. Such linearity is a basic prerequisite of a linear regression. The reason for the non-linearity is mainly due to El Nino warm water pools drifting out of the ENSO index region and continuing to warm for years, though no longer measured by the ENSO index. Detrended AMO appears to be the better choice, PDO may be another good choice IMHO.
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bill4344 at 16:04 PM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
I'll buy that T-shirt, by the way. (With maybe a bit less text)
That's a strong graphic.
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KR at 14:47 PM on 16 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Tom Curtis - Also worth noting are data discrepancies during the war years, and during the change-over from bucket/engine-room/buoy measures of ocean temperatures. I'm not convinced that all of those data issues for the 1940's have been resolved.
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dana1981 at 14:44 PM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Yes, the paper is all over the media. More coverage than we even expected, which is awesome. We can't even keep up with all the articles!
The he/she mistake actually originated in the Reuters article. Innocent enough – you only talk with people over the internet, they never actually see you, and Dana could be either gender. I've emailed Doyle at Reuters about the mistake as well.
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KR at 14:43 PM on 16 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Tom Curtis - Quite right, dates (and variability) are not exact. Just keep in mind that while the ENSO represents a major portion of the climate variability, it doesn't cover all of it. However, the 1915-1935 La Nina's and the 1935-1945 El Nino have a significant effect on short term temperature slope over that range.
I would not at all be surprised by significant black carbon influences - without satellite measures in the WWII period, it would be difficult to say how much BC was present due to basic fire effects during war years. To estimate that would require extrapolating war damage to black carbon production, and I am not aware of any work in that respect.
Does anyone know of relevant papers?
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chriskoz at 14:20 PM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
skywatcher@8
I've sent an email to Peter Hannam today at 14:00AET (Sydney) requesting the correction. Will see how long this simple fix takes him.
Everyone in climate blog circles (I guess also most climate scientists) know Dana. But pupolar press editors still don't know him and make big gaffes about him. It's like AGW scientific concensus vs. lack of public awareness about it.
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Tom Curtis at 14:17 PM on 16 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
KK Tung @34, here is Fig 9.5 A of AR4 overlaid with HadCRUT4 running 12 month mean along with the trends from 1900-1960 and 1910-1940:
Clearly both trends are greater than that of the multimodel mean over equivalent periods. That being said, the 1900-1960 trend clearly lies above the data from 1945 on, suggesting that it has been dragged up by the 1937-1946 temperature excursion. It is fair to say, therefore, that the multimodel mean accurately predicts temperatures in the early and mid twentieth century except from 1937 to 1946. Given that the world was in a state of war durring that period (remembering not just WW2, but Spain, Manchuria and the Sino-Japanese wars) it is at least plausible that the excursion is either an artifact of reduced temperature measurements or the result of unusual and as yet undetermined forcings resulting from the devestation of modern warfare.
Of course, if the appropriate trend comparison is 1910-1940, such possibilities will be inadequate to explain the discrepancy. However, for 1910-1940 to be the appropriate period of analysis, we need an independent reason for distinguishing that period. Without that independent reason, focusing on an interval starting with an unusual low and ending with an unusual high in tempertures is just another game of cherry picking.
You will argue, no doubt, that the existence of the AMO give sufficient reason to focus on that interval. I would disagree. You have not established the existence of an AMO prior to the twentieth century, and your reason to consider the twenteith century AMO independent from known forcings comes down, in the end to the 1940s temperature discrepancy. Consequently, the is not evidence of a globaly influental AMO, but only that something occurred in the 1940s which is not yet adequately explained. The AMO is one candidate explanation among others. Indeed, the lack of a regular, influental AMO prior to the twentieth century makes it, IMO, a very weak alternative explanation. So weak that it is in danger of being merely ad hoc.
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Tom Curtis at 13:53 PM on 16 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
KR @36, the cool aberation from 1907-1914 at least partially overlaps the strong El Nino event starting in 1910, and hence is not entirely explained by ENSO. Likewise the warm aberation from 1937-1946 is longer, and starts earlier than the major El Nino of 1940-1943. (Dates determined by eye so not exact.) Consequently while ENSO may partially explain these aberations, there remains something to be explained once we have accounted for ENSO. I personally am inclined to think that Black Carbon forcing durring the war years has been underestimated, but obvoiously that is just a guess.
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Rob Honeycutt at 13:22 PM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Yeah, I'm really glad we did the self-rating thing. It removes any notion that the results are just the SkS rating being biased. In fact, it shows that the SkS ratings were very conservative in their judgement.
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DSL at 13:14 PM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Let the whining begin. Congratulations, people! The self-ratings results are a slap upside the head of the Watts-bots.
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Miriam O'Brien (Sou) at 13:12 PM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
You can't argue with the evidence. Looks to be an excellent effort all around. Congratulations to John, Dana and all the authors and everyone who worked so hard to bring this to fruition. Also to the donors.
I see it's popping up all over the mainstream press. It's having a solid impact.
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skywatcher at 13:11 PM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Awesome work everyone, very impressive indeed. Also a nice article in The Age, but someone should maybe tell them Dana's a bloke! -
Bob Loblaw at 12:54 PM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Yes, congratulations are in order. A team of volunteers, contributing significant amounts of their personal time - an accomplishment to be proud of. And to get such a large number of scientists to participate by rating their own papers - that in itself is an indication of the respect that active climate scientists give to the team and the leadership of John Cook.
And kudos to the rush of SkS readers that provided the funds (10 hours!) to make the paper Open Access. Readers that were obviously willing to put their money where there eyes are...
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Bob Loblaw at 12:41 PM on 16 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
KK Tung @34: " As a scientist we pay special attention to the systematic discrepancies between model and observation, and I see a systematic underprediction of the observed warming rate in the early part of the twentieth century by the CMIP3 models. "
[Refering to the graph presented by KR @23]
Other than your eye, what basis do you have to say that it is a systematic underprediction? Exactly how are you determining which part of the observations represent systematic behaviour, and which part represent random behaviour? (Note that I am asking a somewhat rhetorical question: from what I've read in the posts and your comments, my impression is that you have determined that the observations have systematic behaviour because you've assumed that the behaviour you see is systematic.)
GCM simulations, by their nature, will have random variations over time, if you start them from slightly different initial conditions. Each simulation represents a realistic sequence, but any one of them will be possible. The observations only represent one sequence. It's like rolling dice: you can have one sequence of numbers originating from rolling the dice 100 times, and a computer model "throwing" dice via a random number generator. When you compare the two, you don't expect an exact match. Doing 20 computer simulations and averaging them will give a sequence closer to the middle, but the observations can still fall anywhere in the expected range for a single sequence. (The analogy isn't the best - rolling dice is purely random, with no systematic pattern in the trend over time.)
It is simply a mistake to think that the ensemble model mean is what nature is supposed to do: even with a perfect model, nature could follow any one of a large number of different sequences from the model. The correct thing to do, if the observations fall wihtin the range of the individual model runs, is to accept that there is little else you can say about the comparison.
You simply can't expect the non-stochastic behaviour of the model (average of a number of runs) to follow the stochastic nature of a single run (or observations). If you try to do so by adjusting the model, you are fitting to the noise. In such a case, fitting to a different sequence (e.g., a different time period) with different noise will require different adjustments to the model - and it won't mean anything because the underlying physics is still the same and you've just taken noise and interpreted it as signal.
...which appears to be exactly what you are doing with your study: you have mistaken noise for signal, and see a pattern that you think means something, but the pattern is just an artifact of the particular sequence of noise in the data.
I, like others here, remain unconvinced.
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KR at 12:24 PM on 16 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
scaddenp - Indeed, which makes the 2000-2012 "slowdown" accompanied by more of a balanced ENSO distribution (ending in significant La Ninas) far more understandable; the expected effects of short term variations against recent history.
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Doug Bostrom at 12:17 PM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
A huge amount of work; well done!
It's remarkable to see in black and white numbers how isolated contrarians have made themselves.
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scaddenp at 12:12 PM on 16 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Interesting graph KR. I note too though there is an unually large no. of EN events from 1975 to 2000 which would imply observed warming about background levels.
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KR at 11:25 AM on 16 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Dr. Tung - Given the large number of La Nina events from ~1915-1935, followed by a decade long El Nino state centered around 1940, the first qualification of the IPCC report should apply:
Differences between model and observations should be considered insignificant if they are within:
1. unpredictable internal variability (e.g., the observational period contained an unusual number of El Niño events),
2. ...
[Source]
I believe that unusual run of ENSO is a more than adequate reason for a slightly higher slope than non-ENSO modelling in the beginning of the 20th century - without invoking huge internal variations inconsistent with ocean heat content. I consider your claims of poor focing/climate modelling in the early 20th century unfounded.
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Tom Curtis at 10:55 AM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Congratulations to John Cook and the SkS team for this important paper. I know how much work was involved and the team that carried it out have done a marvelous job.
Moderator Response:[JH] You were an integral part of the SkS team and made major contributions to the TCP effort. Thank you for that as well.
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Rob Honeycutt at 10:50 AM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
But they are very very noisy!
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Alexandre at 10:23 AM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Albatross at 09:26 AM on 16 May, 2013
I agree with you that this disagreement among 'skeptics' should be more stressed. They are:
1) a very heterogeneous group, with conflicting theories among them
2) a very tiny minority, as shown here (again)
3) not backed up by evidence
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Alexandre at 10:19 AM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Man, this was fast. Congrats to all co-authors and volunteers.
About the skeptics, I think a more accurate sentence would be
We fully anticipate that some climate contrarians will move the goalposts by saying "we don't dispute that humans cause some global warming."
I'll add this paper to the Wikipedia article on Global Warming (Portuguese version).
PS: SJI link is incomplete and not working.
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KK Tung at 09:56 AM on 16 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Correction to my post 26: 1700s should be 1800s.
Moderator Response:[Sph] Original comment revised to help avoid confusion.
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KK Tung at 09:54 AM on 16 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
In reply to post 31: "So the question I would like Dr Tung to answer is "Exactly how close to the multi-model mean would you expect the observations to lie in order to give a good hindcast of 20th century temperatures, and how would you justify this estimate of the magnitude of the unforced component?""
The ensemble mean, especially multi-model ensemble mean, should reveal only the forced response. The difference should be accounted for by the unforced variability (if we assume that the models' forced response is correct). Although there is quite a bit of inter-model scatter, about 0.3 C, as often happens when you have an ensemble of different models with different levels of quality, one can see in AR4's Figure 9.5 a difference in slope between the red curve and the black curve. I hear what some of you are saying about the fact that the difference still lies within the scatter, and therefore there is no need for an unforced variability and that the AR4 models are doing well simulating the historical data in the early twentieth century as well. As a scientist we pay special attention to the systematic discrepancies between model and observation, and I see a systematic underprediction of the observed warming rate in the early part of the twentieth century by the CMIP3 models. This just my opinion. You do not need to agree with me on this.
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Albatross at 09:26 AM on 16 May 2013Skeptical Science Study Finds 97% Consensus on Human-Caused Global Warming in the Peer-Reviewed Literature
Congrats to everyone involved! Undertaking this research clearly required an immense amount of work and dedication, not to mention enduring an illegal hack on the SkepticalScience website (the stolen material which fake skeptics were [and are] only too happy to disseminate, is evidence that ethics and morality are extremely low on the list of priorities of fake skeptics).
Regardless, this independent study by Cook et al. (2013) corroborates previous research, and once again underscores the fact that anthropogenic warming is indeed a theory, with multiple independent lines of evidence have lead to this consensus (consilience in fact).
In stark contrast, the radical 3% cannot even seem to agree on what to disagree about, they are in a state of chaos, have an alarming propensity to engage in conspiracy ideation and routinely contradict each other and even themselves. The spectrum of positions held by this fringe element range from those who deny the existence of the so-called greenhouse effect, to self proclaimed "lukewarmers" and fake skeptics. Indeed, this fringe element seem even more disorganized than those who deny the theory of evolution.
Climate "skepticism" is in disarray, hardly surprising given that their position/beliefs are based on ideology and politics and not on sound physics.
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scaddenp at 07:24 AM on 16 May 2013The last time carbon dioxide concentrations were around 400ppm: a snapshot from Arctic Siberia
William, in that past period there has been time for full equilibrium to be established. 8C warmer is consistant with estimates of ECS. It takes 1000s of years for ice sheet to melt but when gone, your albedo is reduced. Ditto for ocean equilibrium. Noone disputes that climate has changed in the past without human influence. That statement is just rhetoric and verging on sloganeering. The important point is that climate has changed in the past for well understood reasons and those causes dont apply now. With different milankovich forcings, interglacials were at different temperatures. However, consider that in pliocene, milankovich cycles were still happening but glacial werent. Why? CO2 too high.
Because fires can start naturally, does that mean you cant charge someone for arson?
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Rob Honeycutt at 07:13 AM on 16 May 2013The last time carbon dioxide concentrations were around 400ppm: a snapshot from Arctic Siberia
William @ 23... The fact that atmospheric CO2 has radiative properties that cause the planet to warm does not have to be re-examined in each and every paper that discusses it. This is a fact that has been well established for over 100 years.
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William Haas at 07:07 AM on 16 May 2013The last time carbon dioxide concentrations were around 400ppm: a snapshot from Arctic Siberia
So according to this article there is more evidence of huge changes in climate that could not possible be caused by man. It talks about CO2 levels about what they are today but with temperatures as much as 8C higher. (-snip-). This paper is consistent with the idea that some of the past interglacial periods were much warmer than the current one.
Moderator Response:[DB] Sloganeering snipped.
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HK at 06:52 AM on 16 May 2013The last time carbon dioxide concentrations were around 400ppm: a snapshot from Arctic Siberia
David Archer has a good explanation of how greenhouse gases work in chapter 4 in his textbook Global warming - understanding the forecast.
You can also try out the Modtran model of infrared light in the atmosphere on his website here.
This model doesn’t calculate climate change directly, only the changes in IR flux for a given surface temperature with changing concentrations of CO2, methane and ozone.
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rockytom at 05:38 AM on 16 May 2013The last time carbon dioxide concentrations were around 400ppm: a snapshot from Arctic Siberia
John, Thank you for an excellent and in-depth explanation of the Lake 'E' results so far. As you point out, this is on-going research and a great deal of data remain to be published. I, for one, look forward to additional information from this site as it appears to be a unique terrestrial record for the past 3.6 Ma.
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R. Gates at 04:43 AM on 16 May 2013Another Piece of the Global Warming Puzzle - More Efficient Ocean Heat Uptake
Rob,
I completely agree with you about SST's as a poor diagnostic tool for global warming. They really just tell more about the energy leaving the ocean to the atmosphere. After the 97-98 El Nino with such high SST's, it would be more accurate to have said "look how much heat WAS in the ocean", rather than "look how much the oceans are warming."
I think overall we are saying the same thing about ocean heat storage and simply differ on perspective. You say the oceans are getting better at heat uptake, and I look at it as they are not passing as much back to the atmosphere-- but the net result is exactly the same in that much of the measured TOA imbalance can be found in the oceans, albeit we need a lot more data below 2000 meters.
Incendentally, here's some independent research that seems to confirm ocean warming over the past 40 years, showing that despite the uncertainties and calibration issues, even the older XBT data was accurate at showing the upward trend:
http://phys.org/news/2013-05-fish-thermometer-reveals-long-standing-global.html
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Dikran Marsupial at 04:38 AM on 16 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
From Page 595 of the IPCC AR4:
8.1.2.3 Testing Models Against Past and Present Climate
...
Differences between model and observations should be
considered insignificant if they are within:- unpredictable internal variability (e.g., the observational period contained an unusual number of El Niño events);
- expected differences in forcing (e.g., observations for the 1990s compared with a ‘pre-industrial’ model control run); or
- uncertainties in the observed fields.
Note in particular, item 1. If someone wants to show that the model hindcast is poor, they need to be able to show that the error exceeded the uncertainty due to internal variability.
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heijdensejan at 03:18 AM on 16 May 2013The last time carbon dioxide concentrations were around 400ppm: a snapshot from Arctic Siberia
Rob,
That's the best explanation I have heard so far! -
Dikran Marsupial at 02:17 AM on 16 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
On second reading, Dr Tung wrote "Compare the slope of the red curve with the slope of the black curve." They look rather similar to me, provided you aren't looking at decadal variation, which is largely due to unforced variability (e.g. ENSO) which is deliberately averaged out in computing the multi-model mean (as the "ENSO" in individual model runs can't reasonably be expected to be synchronised with the observed ENSO, as ENSO is a chaotic phenomenon).
It seems to me that the purpose of computing the multi-model mean is not well understood in discussions of climate, but the bottom line is that it is not a prediction/hindcast of the observed climate change, just a prediction/estimate of the effects of the forcing on the climate. These are not at all the same thing!
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Dikran Marsupial at 02:11 AM on 16 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Dr Tung wrote "Figure 9.5 from AR4 is the figure that I often used to show that while the warming since midcentury has been simulated quite well, the early twentieth century warming has not been simulated"
Like KR, I find this a rather odd statement. The multi-model mean is not directly a prediction/hindcast of GMST, but only of the forced component of the change in GMST. As such there is absolutely no reason to expect the observed GMST to lie any closer to the multi-model mean than within the spread of the model runs (as the spread is implicitly an estimate of the plausible magnitude of the unforced response). The figure shows that the models give as good a hindcast of 20th century temperature variations as we could reasonably expect, given what the models are actually intended to achieve.
Even if the model physics were exactly perfect, the observation would still be expected to lie only within the spread of the model runs, and there would be absolutely no reason to expect them to be any closer.
So the question I would like Dr Tung to answer is "Exactly how close to the multi-model mean would you expect the observations to lie in order to give a good hindcast of 20th century temperatures, and how would you justify this estimate of the magnitude of the unforced component?".
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KR at 01:58 AM on 16 May 2013The anthropogenic global warming rate: Is it steady for the last 100 years? Part 2.
Dr. Tung - The comparison of models to observations show that observations are within the 2-sigma range of those models. That's not a failure of the models, but rather an indication of their success, even though the model mean averages out ENSO variations across the models.
Models that are fit to forcings and to observed ENSO variations, such as the one Kevin C pointed out, are much closer fits to the data.
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The linear detrending of the AMO used in your paper is wholly inappropriate for attribution studies, as is noted by one of the very papers you rely on for your argument (Enfield and Cid-Serrano 2010). Forcings over the last century are non-linear, and a linear detrend leaves much of the warming signal in the AMO component, causing an underestimation of global warming as in your paper. Your assumption of linear warming is therefore a circular argument. Your cycle identification, and use of the CET, has other issues of non-periodicity as noted by Tom Curtis. And you have continued to completely ignore the energy balances (Anderson et al 2012, and for that matter Levitus et al 2001, Levitus et al 2005, and other works) that show the AMO and other internal variation cannot be contributing significantly to global warming given observed ocean heat content.
You have not, in my opinion, made your case, and I would continue to agree with the analysis first raised here - that your conclusions regarding a low warming trend are unsupported.
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Rob Honeycutt at 01:30 AM on 16 May 2013The last time carbon dioxide concentrations were around 400ppm: a snapshot from Arctic Siberia
I've always found it interesting too. I liken it to harmonics. If you open up a piano and can sing loud enough, if you sing a D note each of the D strings in the piano will begin to vibrate symathetically. Sing a G and the G strings will vibrate.
Same thing is working, on a much smaller scale, with IR radiation. Since a CO2 molecule is configured in a way as to allow it to vibrate, it has a frequency where it will vibrate.
Sing that G note again in front of the piano. What happens when you stop? You can hear the G strings continuing to vibrate. They are "re-emitting" the note you sang.
Same thing with CO2. When it begins to vibrate in the presence of the right IR frequencies, it is "re-emitting" that same energy it absorbed.
I'm sure there's a point where the analogy breaks down but this is how I get my head around the concept.
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Paul D at 00:03 AM on 16 May 2013The last time carbon dioxide concentrations were around 400ppm: a snapshot from Arctic Siberia
Re the Saadi Aubydi and Atomant discussion.
I actually find the concepts of distinguishing between greenhouse gases and non-greenhouse gases fascinating and I learnt a lot discovering the difference. Not just about the greenhouse effect either.
Once you get your head around the basics, you can see why molecules that are more complex than CO2 can be potent GHGs. I'm probably better at visualising what is happening than I am at understanding the maths.
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John Mason at 23:53 PM on 15 May 2013The last time carbon dioxide concentrations were around 400ppm: a snapshot from Arctic Siberia
Thanks guys - people do come on here to learn and some of them may be genuinely inexperienced in this field of science - but we should support anybody who wants to learn - in fact I would be delighted to see more people not afraid to ask even the most basic questions.
One thing to consider is perhaps an open Q&A thread for such a purpose.....
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Tom Curtis at 23:29 PM on 15 May 2013The last time carbon dioxide concentrations were around 400ppm: a snapshot from Arctic Siberia
Atomant @13, H2O is a greenhouse gas because the molecule has electrical poles. Specifically, the Oxygen atom atracts electrons more strongly than does the Hydrogen atom, resulting in the hydrogen atoms being positively charged when in a water molecule, with the Oxygen atom being slightly negatively charged. Further, because of the molecular configuration the water molecule has a number of vibrational modes, which makes it a strong absorber.
Of course, Hydrogen and Oxygen atoms which are neither ionized nor part of a chemical compound have no net electrical charge and cannot have no vibrational modes within the molecular bonds (which they do not have) and so do not absorbe IR light. They will absorbe light of higher frequency based on the energy levels of their electron shells.
I am glad you are so willing to go back to class on this.
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Dikran Marsupial at 23:05 PM on 15 May 2013The last time carbon dioxide concentrations were around 400ppm: a snapshot from Arctic Siberia
@Atomant, it was a reasonable question; there is nothing to be gained by being rude and dismissive to those seeking knowledge, it does not create a good impression. See Tom's answer @ 6 for a much better approach. Skeptical science is a forum for discussing the science, which is why we generally try to adopt a calm rational tone, unlike the hyperbole and rhetoric that you tend to see in climate blogs that want to avoid discussing the science.
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