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Cold Case vs. CSI

Filed under: — gavin @ 14 February 2007 - (Slovenčina)

If you are a follower of TV crime shows, it is likely that you’ve come across one of the CSI offshoots (CSI stands for Crime Scene Investigation) and a slightly less well known show called ‘Cold Case‘. In both these shows, difficult crimes (usually murders) are solved using the most up-to-date forensic methods and incredible detective work. However, it will be obvious to even the most jaded TV watcher that the CSI crew get to have a lot more fun with the latest gadgets and methodologies. The reason for that is clear: with a fresh crime scene there is a lot more evidence around and a lot more techniques that can be brought to bear on the problem. In a ‘Cold Case’ (where the incident happened years before), options are much more limited.

Why bring this up here? Well it illustrates nicely how paleo-climate research fits in to our understanding of current changes. Let me explain….

For the last 30 years or so, the amount of information we have about the planet has gone up by a couple of orders of magnitude – mainly due to satellite information on atmospheric (radiation, temperature, humidty, rainfall, cloudiness, composition etc.), ocean surface (temperature, ice cover, windiness) and land properties (land cover, albedo) etc. Below the surface, we are now measuring much more of the ocean changes in heat content and carbon. This data, while still imperfect, has transformed our view of the climate such that the scientists studying it can seriously discuss details of problems that twenty years ago were not even thought of as issues. “CSI – Planet Earth” if you like.

Comparatively, the amount of information we have for any period in the past is less – hundreds (in some cases a few thousand) of records of climate ‘proxy’ data (i.e. records that are related to climate, such as tree rings ot isotope ratios, but that aren’t direct thermometers or rain gauges) that are not necessarily optimally spaced, nor necessarily well-dated, nor uncontaminated by non-climate influences. However, there is the great advantage of a much longer time period to work with, as well as a greater variety of changes to investigate. Think of the people that work on that as the ‘Cold Case’ crew.

The most prevalent reasonably scientific question about current climate changes is ‘how do we know that this isn’t natural variability?’. A number of versions of that question came up in the House hearing last week (a nice report from the proceedings can be found here). Some of those comments were serious, some were ridiculous, but all essentially pointed to the same issue. Kevin Trenberth and Richard Alley answered it best when they pointed out that the causes of ‘natural variability’ – whether the sun, volcanoes or ocean changes – should be detectable (but haven’t been), and that the anthropogenic ‘hypothesis’ should have consequences that are also detectable (which have). Add in the modelling studies which indicate that current conditions can’t be explained without including greenhouse gases and you have a pretty solid case that what is happening is in large part anthropogenic.

A rather more specious comment heard often (including at this hearing) is that ‘if it was warmer before, then the current warming must be natural’ or alternatively ‘if you can’t explain all of the past changes, how can you explain anything now?’. First of all, there are many periods in Earth history that are unequivocally accepted to be warmer than the present – the Pliocene (3 million years ago), the Eocene (50 million years ago) and the mid-Cretaceous (100 million years ago) for instance. Less clearly, the Eemian interglacial period or the Early Holocene may have been slightly warmer than today. Thus, if that logic were appropriate, no-one should bother worrying about climate change until sea levels start to approach mid-Cretaceous levels (about 100m above today’s level!).

However, the logic is fatally flawed. It is akin to a defense lawyer arguing that their client can’t possibly have committed a particular murder because other murders have happened in the past that were nothing to do with them. That would get short shrift in a courtroom, and the analgous point gets short shrift in the scientific community too. Of course, it is possible that our suspect was involved in previous murders too – but obviously the further back you go, the harder it is to pin it on them. And clearly, there will be past murders where they have a clear alibi.

A better tactic for the defense is obviously to try and pin it on someone else – and if that someone else has a record – then all the better. Therefore, ‘the sun did it’ is a frequent accusation, but as we have discussed here quite often, this time around the sun has an alibi and there are reliable witnesses to back him up.

Given the better information and resources available for the CSI crew, it is natural that their assessment of the current case will generally hold sway. Cold Cases (or paleo-climate) are of course of paramount interest: they provide a much wider set of conditions that set the stage for the modern analyses and provide plenty of test cases for us to hone our techniques (such as climate modelling). However arguments from paleo are extremely unlikely to trump the modern analyses – whether they refer to the medieval warm period or the Phanerozoic.

So to summarise, CSI-Planet Earth have a good case for pinning the latest warming on greenhouse gases. Cold Case has evidence that they were involved in some previous cases (the last glacial period for instance), though they’ve definitely ruled our suspect out for a few others (e.g. the 8.2kyr event). It would be hard to argue that our suspect should be acquitted because there have been some crimes they didn’t commit!

Update: I should have linked to this Newsday piece: Hot on their global trail by Bryn Nelson where I first tried out this analogy.

168 Responses to “Cold Case vs. CSI”

  1. 1

    Dr. Schmidt, this must be why you get the big bucks! ;) This post is genius. I hope you don’t mind if I quote from this in my next Climate Project presentation.

    I deeply appreciate the time you and your colleagues have dedicated to this site. It’s obviously a labor of love, for both the science and the planet. You’ve all become role models for my kids, and, I’m sure, for the children of other people like me who check in regularly to RealClimate. Scientists are officially “very cool dudes” to my 14 yr old son and his friends. Thank you so much.

  2. 2
    David Wilson says:

    ‘anthropogenic’ is all very well, ‘man-made’ is about the same, no? but that is a mere quibble – I do welcome essays on your site aimed at people who are not scientists, and which help me (at least) make sense of it

    a point brought to me by Leonardo Boff is that the coming changes will involve as many opportunities as potential horrors, there is a hope at least that we can change our ways for the better

    thanks again and be well.

  3. 3
    tamino says:

    Likewise, once the case goes to trial the defense may try everything possible to sow doubt in the minds of the jury members, suggesting that the evidence itself is tainted (urban-heat-island effects), that my client only assualted the victim (earth has only warmed a fraction of what is claimed), that the evidence is only circumstantial (computer models can’t be trusted), that any deviation from the simplest possible interpretation is proof of innocence (the steady rise of CO2 isn’t matched by the rise-fall-rise pattern of 20th-century temperature), that the victim was killed by roving gangs of “terrists” on a jihad (galactic cosmic rays), that the victim died of natural causes (solar variation). If Johnny Cochran (Fred Lindzen) anchors the defense, that lends it all the more credibility.

    To this juror, the prosecution’s case is true beyond a reasonable doubt. Guilty!

  4. 4
    Jeremy Kenyon says:

    The big difference between a murder investigation and climate change is that it isn’t a past killing – it’s more akin to an ongoing genocide, and our concern perhaps should be more about stopping the crime than finding out who to blame.

    Perhaps the approach to persuading the sceptics is wrong. Contrarians can always try to say it is natural, not human. By climate scientists saying it is human just puts up a case to defend (one I agree with, but a case to defend nevertheless).

    The best way to answer someone who says it is natural is to ask them what they intend to do about it. After all, if the cost of dealing with sea level and temperature rises is huge human suffering and costs in the trillions, it is still going to hurt even if it is natural.

    Also, a sceptic could quite validly say that the climate has been much hotter and sea levels 100m higher, so there is nothing wrong with that because it is natural – all we are doing is making it happen a bit sooner.

    The only problem is that we depend on the climate being what it is – we have built society around the current (give or take a bit) sea levels and temperatures. We can adapt to 100m higher sea levels, but it will take centuries of determined effort.

    It’s like driving a bulldozer through a piece of land. If the land is empty, it is not a crime. But if there is a house on the land, with a family living in it, it becomes a crime. Climate change with nobody in the way would be OK, but the majority of the worlds population are in the way right now, along with the rest of the inhabitants of the earth…

    The question becomes ‘what can we do to slow or prevent climate change, whatever the cause’, and the answer will include ‘reduce carbon emissions’. At the very least, it will give us more time to prepare for the ‘crime’.

    Still leaves the problem of those who insist there is no change happening at all though…

  5. 5
    Leonard Evens says:

    The contrarians often seem to be engaged in an ‘anything but greenhouse gases’ expedition. As you note, the argument is that it may be possible to explain current warming by some other mechanism, so that excludes greenhouse gases as the culprit. There are obvious difficulties with such reasoning. It doesn’t suffice to show that solar forcing for example may explain a large part of observed warming. You also need to show why greenhouse gas forcing doesn’t work as an explanation. Indeed, contrarians often come up with an abundance of different explanation which in total would overexplain observed warming. It appears that the ‘consensus’ climate scientists are the only ones who realy take seriously all possible explanations and who are bothered by such inconsistencies.

    A similar thing happened with supposed tropospheric decadal cooling/warming trends. Contrarians kept quoting it as evidence that no warming was taking place but never seemed particularly concerned with the diparity from surface data. The serious climate siceentists saw it instead as a puzzle demadning solution, eventually obtained through better analysis of the microwave sounding data.

  6. 6
    Taylor says:

    Thank you for such a very graspable metaphor–and for continually informative posts.

  7. 7
    mike says:

    It is helpful now and then to air our minor differences of viewpoint here at RC, and I present this comment in that spirit. It is certainly the case that paleoclimate evidence is just one line of evidence in support of the case for anthropogenic impacts on climate. We’ve said as much several times before (see e.g. here and here) of course. However, the targets provided by paleoclimate information are important for far more than simply “honing our techniques”. They are essential for independently testing the models, and determining whether or not they can be relied upon outside of the relatively narrow range of modern observation that informs the parameterizations of unresolved physical processes in the models. We probably would have relatively little faith in current generation climate model predictions if not for the fact that they seem to be able to describe some important changes in the past reasonably well (e.g. the LGM cooling). However, until we can solve e.g. the equable climate problem (the fact that climate models cannot reproduce the apparent greatly reduced equator-to-pole temperature gradient of e.g. the Eocene), we have to take some pause in fully trusting them to make accurate predictions of possible future climate change. The paleoclimate evidence suggests the possibility that models may underestimate future changes, and we ignore this evidence at our peril. This is particularly true with respect to certain phenomena (e.g. El Nino). We can’t yet trust the global coupled models to be getting El Nino (and changes therein) right as long as certain known deficiencies (e.g. the “split ITCZ problem” in the Pacific) persist in the models. The modern record of El Nino is simply too short to determine the natural variability of El Nino, no matter how spatially or temporarily dense our modern measurements are. Paleoclimate observations provide our best hope to get a handle on this, and help us determine when we’ve probably got El Nino right in the models. This isn’t a trivial issue. Until we are sure how climate change impacts El Nino, regional climate change forecasts over most regions of the world are likely to remain of somewhat limited utility. Its important to keep all of this in perspective.

  8. 8
    Ed G. says:

    Great article!
    Minor typo: In the next to last line of the next to last paragraph I think you mean “unlikely to trump the modern analyses”

  9. 9
    Pat Cochran says:

    I’m not sure I agree with the analogy. So climate murder has been committed and there are several suspects. Some of them have been convicted of climate murder in the past ( volcanoes, solar events, etc). They are natural. Civilization has never been convicted of climate murder in the past but because there are no clues pointing to the naturals, we use circumstanial evidence to convict civilization. So we find them guilty and go about reforming them so they can’t do it again. That’s all well and good.
    What I can’t understand is why we think we can control the climate in the future. We don’t know what natural forces will be in play even a year from now.
    Can anyone here explain how we know that we can control the climate? What if the climate started cooling for natural reasons? How would we stop that? Would cooling be good since we’re so warm now? How long would we let the cooling go on? Till it was as cool as in 1850? If this warming were found to be natural should we interfere with a natural process?
    I think there are two things certain, we have no clue as to what the future holds, we have no way to control the massive forces of nature.

    [Response: Unfortunately for civilisation, it’s more than just circumstantial. They were seen leaving the scene of the crime, their fingerprints are all over the murder weapon and while motive is still in doubt, there was plenty of opportunity. However, the issue is not whether we can ‘control’ the climate. I don’t think we can (hence my scepticism over geo-engineering efforts). But it’s precisely because we can’t predict precisely where our current course will lead that makes me wary of pushing the system much further. – gavin]

  10. 10
    John Gribbin says:

    It is also worth emphasising that the pace of change now is greater than during previous “natural” warming events. Ecosystems that adapt to a change of a couple of degrees in 10 kyr find it impossible to cope with two degrees every fifty years!

    [Response: Yes, this is really the key point. Arguably, if we had been firmly within the grip of glacial period during the pre-industrial period and had adapted to that state over tens of thousdands of years, and Co2 increases were taken us towards an ‘anthropogenic’ state resembling, say, the Little Ice Age, we’d be in much greater trouble. We’d be facing much greater sea level increases and coastal flooding. Its not the absolute state as much as the rate of change, which presents the real challenges and threats. -mike]

  11. 11
    RBH says:

    I’m nowhere near a climate scientist (I do evolutionary modeling in an applied context), but I read RC fairly often. I’ve noticed that it has begun to suffer from creeping acronymism which makes it less and less accessible and comprehensible to the lay reader. For example, in Mike’s comment above there’s a reference to “the LGM cooling”. Try as I might, I find no prior referent for that acronym in the main post or other comments, and can construct no plausible interpretation (“Little Green Men cooling”?). It’s a great help to non-specialist readers if on first use, folks give the full phrase with the acronym in parentheses, so those of us not in the in-group can follow along. While I appreciate that many of the posters are professionals debating among themselves, a fair proportion of your readers are not professionals, are not conversant with every acronym, and appreciate it when the professionals remember they’re also in a teaching mode on RC.

    [Response: Last Glacial Maximum – around 20,000 years ago. Sorry about that – we will try harder in future. – gavin]

    [Response: This is defined in past RC posts. But in most cases, as here, just stick “LGM” in our search window, and you’ll get an answer instantly. Unfortunately, our glossary is still a bit sparse. This should have been in there. -mike]

  12. 12
    SecularAnimist says:

    gavin wrote: “… there are many periods in Earth history that are unequivocablely accepted to be warmer than the present …”

    The word you want there is “unequivocally“, from “unequivocal” meaning unambiguous; clear; having only one possible meaning or interpretation; absolute; unqualified; not subject to conditions or exceptions.

    [Response: whoops. thanks. -gavin]

    gavin wrote: “If you are a follower of TV crime shows, it is likely that you’ve come across one of the CSI offshoots (CSI stands for Crime Scene Investigation) and a slightly less well known show called ‘Cold Case’. In both these shows, difficult crimes (usually murders) are solved using the most up-to-date forensic methods and incredible detective work […] it illustrates nicely how paleo-climate research fits in to our understanding of current changes.”

    Hmmm. Consider the insights into climate research and the global warming policy debates that might be revealed by extending this metaphor to include Law And Order, Without A Trace and The Closer.

  13. 13
    Mike says:

    I’m pleased to see that your articles seem to be more frequent. A daily fix would be most appreciated. Ps – that’s not how you spell comparatively or unequivocally!

    Keep up the good work


    [Response:You are unequivocally correct. -gavin]

  14. 14
    teacher ocean says:

    They made a big deal about AGW on Boston Legal last night and the lead character’s argument before the jury was that AGW is not only real but a big problem and we should all, on an individual basis, do something to minimize our impact. The story line and evidence were meant to be humorous and has no scientific relevance because Boston Legal is mostly a comedy, but it was good.

  15. 15
    Lynn Vincentnathan says:

    RE how the contrarians trot out past warming as evidence AGW is not happening (even if GW may be happening), I’ve learned to jump the gun on them at social gatherings.

    I trot out past warmings first, as evidence that it’s happened in the past, with 90% of life dying 251 mya, and it could happen again, only this time we’re triggering it & faster — esp if we get to the 6C increase (upper projection for 2100, but who knows for 2200 or 2300).

    Then before they can even criticize Gore’s AIT, I criticize it for being too conservative and not including the possibility of limited runaway warming (hysteresis), in which our AGW triggers nature to emit more GHGs, causing more warming, causing more GHGs, and so on, all the way to oblivion for a large chunk of life on earth.

    I’ve learned to get in and out fast at various social gatherings…moving on to a more benign conversation, before the contrarians can sicken me ad nauseum with their usual criticisms. I leave the contrarians with, “Just check out; they’re top climate scientists, and they have all the refutations to your issues.”

  16. 16
    raypierre says:

    To carry further Gavin’s fine analogy, let’s extend it to the fact that the most viable theory for Cretaceous warming, and for a large part of glacial-interglacial warming, is also CO2 change — though not CO2 change caused by humans. I have some ideas how the storyline would go for that, but instead of writing down my own analogy, I thought I’d toss it out to the crowd to play around with. Just as a way to remind us that CO2 has indeed been implicated in past climate changes, and that the role of CO2 in past climate changes tells us something about the present, even though this time around it’s humans that are causing the CO2 increase.

  17. 17
    Benny says:


    I thought all you New Yorkers were too busy going to museums and attending art openings to waste time on commercial television…..Good grief. You probably watch Stephen Colbert.

    [Response: Actually, I never watch TV – I’m just trying to get with the zeitgeist. (The good Colbert clips can be found on though…. – gavin]

  18. 18
    Ray says:

    My class and I reviewed paleoclimate over the last two weeks and the “lightbulb” moment was when we took the derivative of the Vostok ice core record in the Holocene to the last glacial (+1.95 degC every 1000 years). That is 0.2 deg/century. When you are talking about 1.5 deg C per century it’s dimes and dollars.

  19. 19
    Philippe Chantreau says:

    A Seattle PI blogger mentioned a study apparently published yesterday about glaciers, whose title suggest the melting trend is not as clear cut as was accepted. Do you know anyting about it?

    These were the references provided:
    Title:Glaciers Not on Simple, Upward Trend of Melting
    Author: University of Washington
    Published on Feb 13, 2007, 06:42
    Published Online February 8, 2007
    Science DOI: 10.1126/science.1138478

  20. 20
    tamino says:

    Re: #18

    Don’t forget, that the Vostok ice core measurements indicate temperature in the Antarctic region; that’s why the net change glacial-to-interglacial is so high (about 10 deg.C). The global change is less than that, about 5 deg.C. So, the indicated Antarctic rate, 0.2 deg.C/century, translates to a global rate of only about 0.1 deg.C/century. The modern rate (using the latest version of HADCRUT3 from 1975 to the present) is nearly 1.9 deg.C/century. So, it’s not dimes and dollars, it’s nickels and dollars.

  21. 21
    Lynn Vincentnathan says:

    #16, here’s one. People walking through the woods sometimes eat poisonous mushrooms and die (past GW & mass extinctions). However, Mrs. Smith wanted to bump off her husband, so she fed him poisonous mushrooms (our GHG emissions & GW now). The defense tried to claim it was his accidental eating of these natural fungi growing in the wild. But the detectives found the stems in her Mrs. Smith’s garbage can and forensics detected trace amounts of poisonous mushroom on the dirty dishes, and on Mrs. Smith’s knife and hands. Furthermore, Mr. Smith had not been near that woods for the past week, according to witnesses, but Mrs. had been.

    The problem with this legal analogy is that policy-makers and we (as mini-policy-makers) do not have to establish “beyond reasonable doubt” or even “preponderance of evidence” (civil standard) to take AGW seriously and address it; the amount of evidence & certainty Bush had for WMDs in Iraq would be more than enough to dig in and mitigate GW.

    Wouldn’t it have been great if instead of spending all that money on the Iraqi war, we would have plowed even a tenth of that into GW mitigation measures, most of which pay for themselves & go on to save…like investments. And we could have used those savings to give even greater help to the poor of the world. Then the whole world would have become our ally. Even terrorists may possibly have started thinking, we can’t attack such good people, bad PR for our cause.

  22. 22
    Sashka says:

    Re: 18

    It would be another lightbulb moment if somebody took trouble answering questions about diffusion of gases within ice cores.

  23. 23
    Steve Bloom says:

    Re #11: As a sort of consumer warning, be aware that the bulk of the comments made on RC are not from climate scientists. There are some climate scientists who comment, a rather larger number of non-climate scientists, and a yet larger number of laypeople who have made a serious (albeit amateur) study of climate science (I’m one of those), but all of these taken together are probably no more than half of the total comments. As well, bear in mind that you can’t rely on there being a refuting comment to every single contrarian claim that gets made here. So, while you can rely on the main posts and the highlighted responses, everything else should be taken with a grain of salt.

    Note to RC authors: When you post individual comments, please highlight them as Mike did in #7 above. Regulars know who you are (most of the time, but was that possibly Ray Bradley in #18?), but nobody else does. Thanks.

  24. 24
    Bill says:

    Well argued sir. I had the pleasure of listening to Dr. Pachrui (head guy at IPCC) speak not long ago. Thankfully this group’s model is so comprehensive and conservative it isolates the climate change denies into a tiny indefensible pocket.
    For those who want to carry the banner forward & get involved:
    I work for the American Council On Renewable Energy ACORE and we have a package deal for young professionals who are already working in the field. The largest all-renewables trade show is 3 weeks off and we have a special offer for RE professionals in their 30’s and early 40’s. It’s great opportunity to network and see the latest technology. The show is Power-GEN Renewable Energy & Fuels and it’s in Las Vegas.
    Here�s the link:

  25. 25
    coby says:

    ‘if you can’t explain all of the past changes, how can you explain anything now?’.

    This illogic is the subject of one of my “How To Talk To a Sceptic” articles:

    A very common attack.

  26. 26
    Hank Roberts says:

    > 19, P. Chantreau.
    This is sad. A new NYT blogger–not a science writer– got this ball rolling recently.

    Best response so far I think was this one there:

  27. 27
    SecularAnimist says:

    Lynn Vincentnathan wrote: “Wouldn’t it have been great if instead of spending all that money on the Iraqi war, we would have plowed even a tenth of that into GW mitigation measures, most of which pay for themselves & go on to save…like investments. And we could have used those savings to give even greater help to the poor of the world.”

    The governments of the world spend around ONE TRILLION DOLLARS per year on the military — on weapons and other means for human beings to kill each other — and more than half of that is the US military budget.

    Imagine what those many, many billions of dollars might accomplish — what they might long ago have accomplished — towards developing and deploying appropriate technologies for a sustainable human civilization living respectfully of all life and within the carrying capacity of the Earth’s biosphere, providing the means for health, happiness, peace and prosperity for all human beings everywhere. It is almost painful to think about it.

    Many critics of taking action to reduce fossil fuel related GHG emissions to mitigate anthropogenic global warming and climate change complain about the supposed “high cost” of doing so. A trillion dollars a year would go a long way towards addressing the problem. But we humans — or at least a number of humans who are in the positions of power to direct such vast resources — prefer to spend that amount on building weapons and killing each other.

    Perhaps the reason the SETI project has been unable to detect signals from any technogically advanced civilizations on planets in other star systems is that all technologically advanced civilizations inevitably follow the same course that we are on, and thus they only have very short periods of time (decades) when they are sufficiently advanced to generate such signals, before they destroy the capacity of their planets to support life, and themselves with it.

    [Response: The NYT had an interesting series in the business section a few weeks ago called basically “What could you do with a trillion dollars.” They had lots of good examples, but unfortunately they left out climate stabilization. In a recent talk at Chicago, Steve Pacala estimated that a gross cost of about US$100 per ton of carbon would be enough to stabilize US emissions at a climatically acceptable rate, using present technologies only. Net cost would be lower, since if you used a carbon tax some of that spending would get plowed back, and even without a carbon tax, there’s the contribution to GDP from people working in carbon sequestration, photovoltaic factories, etc. I think the same numbers can be gotten from Pacala and Sokolow’s paper here but it was stated a bit more transparently in the talk. That would mean a gross cost of 168 billion per year to stabilize the US carbon emissions, given our current emission rate. (about $550 annually per person, gross cost, less if you rebated some carbon tax as income tax rebate). Not something to break the bank. You can compare that $168 billion with your favorite government spending number. –raypierre]

  28. 28
    Dave D says:

    Someone was making a point about time resolution of ice-cores in another thread on this site the other day. I think his question is relevant here, and I didn’t see an answer, so I will give my dumbed-down understanding of it, and ask for an expert to help.

    The time constant for a perturbation of CO2 concentration to decay is about 100 to 150 years (currently). Is this about correct?

    How long does it take a snow layer to be compressed to hermetically trap air bubbles? One website I found said snow is compressed to ice at about 80 meters down. How far back in time is that, say, for Vostok? Ice cores come from up to 3000 m down. Beyond that the bubble collapse under pressure(?). How long ago is that?(600,000 yr?).

    It seems like the trap rate is much slower that the CO2 sink rate. Doesn’t this low-pass filter the CO2 time-signal? For instance, hypothetically, in 1 year a volcano could quadruple CO2. This excess CO2 would drain out over 100 to 200 years. If it takes 1000 years to trap, you would almost totally miss this excursion ( in concetration and temperature from isoptope analysis).

    These numbers are just examples. What is the time resolution of ice cores? Should’nt we be careful saying CO2 concentration is higher now than in any time in past 600,000? Our instantaneous Co2 concentration is higher now than the highest time averaged CO2 over XXXX (?) years , seen in the past 600,000 years.

    Also, does CO2 follow ocean temperature ( outgassing) or lead it?

    Thanks. This is a great site.

  29. 29
    Daniel Goodwin says:

    One problem with this paleoclimatic crime scene, for purposes of figuring out where we’re headed, seems to be that the most recent precedents for current or impending CO2 levels may only be viewed as pre-icecore fuzzy daguerreotypes. Perhaps scientists have a technical definition of planetary disequilibrium, but today seems close to such a state, and that’s a significant problem: disequilibrium is grossly chaotic, thus nearly impossible to reliably predict. The current lag of the models behind what the splendid GRACE data is saying about the ice sheets is an example of a reality fatigue which will persist in studies of an Earth in a continuing state of disequilibrium.

  30. 30
    Steve Bloom says:

    Re #22: Couldn’t stay away, eh, Sashka? Actually the issue you raise has been discussed here before, so a search should locate the information. It happens that Eric Steig, one of the RC co-authors, is an expert on such matters.

  31. 31
    Ray Ladbury says:

    Excellent post–and the analog between the denialist camp (yes I’ll continue to us this word) and the defense is appropriate, as all defense views it’s sole duty to sew doubt, not to reach the truth. However, for someone who truly takes a scientific view, it is not sufficient to say “It’s all natural variation.” We are witnessing changes, and changes do not occur without an underlying driver. Thus far, they have advanced no credible candidate mechanism for the changes we are seeing, while the anthropogenic greenhouse mechanism explains what we are seeing very well and is physically reasonable. To demand that we drop the best candidate mechanism without advancing a credible scientific alternative is anti-science, every bit as much as demanding Darwin not be taught in biology class is anti-science.
    Re 22: Given that diffusion is controlled by molecular size and pressure, it would be expected to occur differentially for different molecules. Moreover, the deuterium/hydrogen ratio does not even depend on the gas, but rather on the water/ice. The expectation if diffusion were a significant issue would be chaos (indeed that is what is seen for very old ice), not a self-consistent body of evidence that favored climate change. That is indeed a lightbulb moment if you understand it.

  32. 32
    Alexander Ac says:

    Good post, as always ;-)

    Though, the comment is slightly off-topic, but I miss one point. We are talking about (inevitable??) reduction of CO2 emissions.

    Let’s consider the Japan, which is country with very high energy use efficiency, on the other hand, “they can’t afford the Kyoto”. Why? Because they are so developed, that they use so much energy and the ONLY way, how to significantly reduce the emissions is simply to use it LESS.
    But is it even possible in practise, to start use LESS energy without any APPARENT reason? On the other hand, everybody wants to be like Japan. Highly efficient and highly developed.

    P.S. For those who don’t know, Chzech president Vaclav Klaus is the new defender of climate and environmental truth ;-)

    of course, backed-up by Sen. Inhofe and Vaclav Klaus chzech fan Lubos Motl…

  33. 33
    Eli Rabett says:

    Perhaps this is a good thread for a question I have had for a long time. Multiproxy reconstructions appear to underestimate climate sensistivity. Was this an artifact from early reconstructions or a sign that preinstrumental forcings have been overestimated?

    [Response: Don’t know why you would think that. Hegerl et al (Nature, 2006) did a reasonable job on the implications for climate sensitivity in the paleo-reconstructions and find a range that is similar to that inferred elsewhere – given the uncertainties in both the forcings and the response. Did you have some other study in mind? – gavin]

  34. 34
    Marco Parigi says:

    Ok, great so you’ve proven Humans guilty beyond reasonable doubt… Stunning. Now for the punishment – I vote we just let the Global warming take its course as a suitable punishment for our collective sins. The Easter Islanders were greedy and cut down all their trees and as a punishment they lost their Island paradise. That’s fair. However bad things get, or what actions we take, the punishment will be proportional to our collective stupidity.

  35. 35
    Blair Dowden says:

    I am wondering how Cretaceous sea level could be 100 meters higher than today when there is only about 70 m worth of water in the remaining ice caps. Is there 30 m of thermal expansion? And how can you compare sea level when the paleogeography (arrangement and size of the continents) was completely different?

  36. 36
    Marco Parigi says:

    Instead of beating the drum on AGW, why not get a little perspective on the range of GHG’s. After all, there is plenty of damning evidence against CH4, CFC’s etc. (This is a serious question by the way) Is it plausible that ALL (>90%) of the recent temperature increases can be attributable to GHG’s other than CO2? This would be reasonably hard to prove/disprove as all GHG’s have risen sharply in previous decades, and all have demonstrated mechanisms of warming. This would have immense policy implications don’t you think?

  37. 37
    Jim Crabtree says:

    Re #27: Raypierre’s response

    I think your number for $168 billion may be off by a couple orders of magnitude when you consider that the US has about 5% of the world’s population and produces about 25% of the worlds CO2. Even if we cut our CO2 production to zero, that leaves the other 75% out there, most of it being produced by third world countries where most of the population is in survival mode or slightly better. They are going to need LOTS of foreign aid to cut their CO2 which will be needed to stablize the CO2.


  38. 38
    Jim Crabtree says:

    Correction on #34

    I should not have indicated that this was Raypierre’s number, but that of Pacala and Sokolow’s.


  39. 39
    Gene Hawkridge says:

    Re 19: I think a couple of the things about glaciers that confuse some folks are that warming might actually result, sometimes, in glacial surges – meaning that the glacier rapidly advances rather than retreating(and thinning at the same time – which may not be as obvious). As I understand the theory behind this, melt water under the glacier provides lubrication, thereby accelerating glacial advance. The other aspect of this issue is that precipitation increases could actually add to glaciation in some cases – precipitation increases that perhaps are due to warming, due to increased evaporation rates. Denialists will latch onto these counterintuitive effects and reach possibly erroneous conclusions – but it is more complicated than just pointing to retreating glaciers.

  40. 40
    Craig Allen says:

    May I make a suggestion for your website:

    Given the very broad range of subscribers to this site and the quantity of jargon and acronyms that are necessarily used, it would be very helpful if you could add a readily accessible glossary. I think I’ve seen on a site somewhere a button that hovers at the bottom right of the screen that maintains it’s position independent of page scrolling. If this were to open a popup window with an alphabet menu at the top, it would be a very useful resource for us all.

  41. 41
    Charles Muller says:

    Let’s fill the analogy…

    All warming, past or present, is a collective crime (in French we say crime en réunion, i.e. several authors for one murder, I don’t know the American terminology). Here, the crimes are approx. 0,75 K for 1850-2005 (CSI). Or approx. 5 K for LGM-midHolocene, for example (Cold Case).

    I notice that the first crime is not so… criminal – because of course, CSI never investigate on putative future crime, so far there’s no crime scene for exerting their precious forensic methods. The problem for CSI experts is to carefully look for and analyze the clues, in order to confound one culprit, and prove the others innocent.

    For Climate Scene Investigation, the big problem (limits of analogy, maybe) is the collective nature of the crime. Suspects are numerous, here, and few think they are totally innocent. Intrinsic variability, sun, aerosols, land-use, GHGs of course are all under suspicion to have some responsibility for the horrible offense of 0,75 K on 150 yrs. And some detectives even look for exotic-but-still-under-exam clues like GCR. The case in even more complicated so far the usual suspect (CO2) is a hopeless murderer, needing the help of pernicious and elusive accomplices (e.g. water vapour, nebulosity, lapse rate).

    What is at stake for CSI ? Not to point out one culprit and expose him/it to public condemnation. But to precisely adress (quantify here) its responsability in the past, present (and eventual) future collective crimes of warming. Not an easy job. And much more complex than rough controversies “all-solar” vs “all-GHGs” so appreciated by popular jury.

  42. 42
    Gareth says:

    I’d suggest that the paleo guys are a bit more like Midsomer Murders (Mike Mann as Barnaby, of course) – dead bodies all over the place, all connected in some sort of obscure way, solvable by the application of detective skill. Perhaps those working on current climate areThe Bill?

    Which actually leads to what I hope is a sensible point. The paleo data is used to validate modelling work by constraining the way that models represent known climate events. However, we have currently booted the planet into a set of conditions not seen in the paleo record: interglacial, high CO2, major deforestation etc. It seems to me that the paleo record is relevant to a climate system operating within its normal bounds, but may not be much help when it’s operating way out of its design parameters. We’re into the “unknown unknowns”, and there’s a danger that the models can’t help much here…

  43. 43
    Eli Rabett says:

    No. I was thinking more of a comment in von Storch and Zorita, but I have seen the comment elsewhere also. What do you get as the sensitivity from say MBH 98 when you make reasonable assumptions about the forcings.

    [Response: This is getting off topic. There is a whole slew of papers by Hegerl et al, Crowley, and others looking at this, using all of the different reconstructions. You can find the references in the Hegerl et al Nature article. The bottom line is that you get sensitivities in the range of 1.5-4.5C for all reconstructions, including MBH98 and all the others. However, one point that is poorly appreciated in many discussions is that random uncertainties in the forcing estimates will necessarily act to systematically underestimate the sensitivity, because of the way sensitivity is defined: as the covariance between forcing and response divided by the sqrt(forcing variance). The random uncertainties in the forcing therefore lead to inflation of the denominator, even if they have no impact on the covariance term (which one would expect for random uncertainties). There is a detailed discussion of this in the appendix to Waple et al (2002). Incidentally, the von Storch et al stuff (and problems therein) has been discussed on site previously here and here. We’ll leave it at that. -mike]

  44. 44
    mark s says:

    Re #28,

    I think Steve(#30) and Ray(#31)’s replies to the ever-dependable Sashka apply to your questions, Dave.

    For a minute i thought your ‘dumbed-down’ understanding, might have had the IPCC on the ropes. Phew, close shave on that one.

    Maybe next time, eh! :-)

  45. 45
    Steve Bloom says:

    Re #28 (Dave D): “For instance, hypothetically, in 1 year a volcano could quadruple CO2.” Let’s hope it stays hypothetical, as few of us could hope to survive such an event. For fun, you might look up “Siberian Traps” and “Deccan Traps.” But the short answer is that volcanos emit very little CO2 in global terms (although lots of dust in the case of big eruptions). Regarding the ice cores, bear in mind that while there is a degree of smoothing, rates of global CO2 change are so slight that it’s not a problem. Even with a really sharp change (much sharper than the record rate of change happening now), I doubt that there would be enough of a smoothing effect to hide such an event (even ignoring the fact that anything of the sort would leave plenty of other evidence). But I’m no expert, so see this RC post for details, and in particular look in the comments for some remarks by Eric Steig.

  46. 46
    Wang Dang says:

    Back to the main topic of popular TV shows, science and climate change. My wife loves these shows but she hates watching them with me, because I am an analytical chemist and I understand and have hands on experience with many of the techniques and instrumentation frequently presented on the CSI type shows. They feed in the sample, and out pops the answer. The never have to deal with sample matrix issues, extraction, recovery, interferences, misleading results, etc. Also, the lead detective is always full of obscure information directly related to the case at hand.
    I also like it when the detectives are wearing leather pants and high heels in the lab, and they they drive a Hummer too, very realistic for science nerds. I’m guessing that the RC climatologists are the similar, leather pants, disco shirt, carefully messed hair, but instead of a hummer they drive a $90,000 Tesla all electric sports car. (Am I right?)
    My favorite GW moments on TV have been when Al Gore was on SNL and during the news segment he showed an old picture of some barren frozen glacial wasteland followed by the current mountian lake that it had become and he debated with Amy Pohlar, his position, that this was a bad thing, and her position was that the new lake looked awesome.
    South Park has also done some shows on GW (taking the skeptical side). One with GW related to human flatulance, another ridiculing (an rightfully so) that horrible pile of garbage movie “Day After Tomorrow”, and another mocking Gore.

  47. 47
    Wang Dang says:

    Re #15
    Wow Lynn sounds like you’re a real barrel of fun at the evening cocktail party. Have you ever seen the SNL bit about Debbie Downer, you should. By the way, you may be contradicting yourself if you are calling Gore’s AIT conservative and talking about a runaway greenhouse effect and then citing RC as your source.

  48. 48
    Jon Ellis says:

    Re 32: Japan has most definitely grow it’s GDP with considerably less growth in energy consumption than other economies.

    However, as someone who has spent the last 5+ years living around Tokyo, there is still a huge amount of wasted energy.

    Programs like Cool biz are an encouraging sign, but there is much more than can be done to further reduce energy use in Japan.

  49. 49
    Paul M says:

    I enjoyed reading that article, If I were to give it a grade, it would be an A.

  50. 50
    John D. says:

    One should never equate spending war chest money on trying one global problem to make peoples lives better and achieve peace on earth and goodwill. There are a multitude of problems associated with why there are wars such as Religious and social differences, race, borders, greed, tyranny, world banks, oil, nasty neighbors, Taliban, terror cells, government structuring, ignorance, to name a few. There will always be a group that will be pissed bacause they did not get as much as their neighbor when the pie is being divided.

    Unfortunately, the only solution to a warless planet is to have one world religion, run by that religion and it would have to be a total tyranny that subdues it’s subjects with fear. Then you would not need to spend on wars but you would still require an army to police it.