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  1. The “2°C/450 ppm numbers” points are very important.

    I was reminded when evacuating for Hurricane Gustav that sometimes you must make very important decisions about what direction to take well before the needed information is available, but the best immediately available info can be vital.

    John Atkeison
    New Orleans, LA, USA

    Comment by John Atkeison — 21 Oct 2008 @ 11:51 AM

  2. Thanks eric

    Setting these kind of limits is practical for policy decisions, but I’m not necessarily sure what it means for climate, ecology, etc. Making the sensitivity of arctic sea ice, Greenland, biological systems, human displacement, or other things that people are interested in into a single “threshold” number is a bit of a strange concept to me. Hansen has an interesting paper on dangerous-interference, but at some point the terminology is subjective, and people need to focus on cost-benefit analysis as well as environmental concerns (like species loss) which is not easily quantified in a dollar sign. 2 C may be too high a threshold for practical application, as for instance, sea ice is currently diminishing faster than models show.

    Strictly speaking, a 3 C per 2x CO2 climate sensitivity corresponds to a 1.9 K increase at 450 ppmv if deltaT= [5.35 ln (450/280)]*(0.75 K/W/m**2), but that is also a long-term response. It says nothing about other aerosols or GHGs either which presumably should cause a positive radiative forcing over the coming century.

    Comment by Chris Colose — 21 Oct 2008 @ 12:37 PM

  3. I am an amateur climate guy who spends about three hours per day for the past 21 years, since 1987, reading all the climate news on the web and in print as I can manage.I’ve posted to RealClimate a few times.I apologize in advance if my posts are often “off thread” or off topic, but it seems that there is latitude on this rule in the blogging sphere.
    So, here goes. First, as always, thanks to the real experts and real expert commentators and bloggers at RealClimate I always learn from them.Second, I want to mention that last year sometime I posted a comment on Realclimate about the danger of the methane at the seabed floors melting and releasing gigatons of methane. Guess what? The methane releasing seastacks are now being observed.They say that if the methane is all released it has the co2 forcing equivalent of all the coal left on earth, and way more than all the current co2 in atmosphere.It will also force a “forcing feedback mechanism” that will further release all the methane from the seabed floor. If these figures are right then “I told you so”.
    Just kidding. I want to know if the experts at RC and the expert commentators who blog on RC know if this figure on seabed methane is accurate, and, if anyone can tell me if all of it will melt, because, if it does, the news stories from last year say we’re in way more trouble than we’ve thought.
    Also, the new story in the news is that the temperature rise is now expected to be 12 degrees farenheight.(sorry I haven’t figured out how to use Celcius scale yet).And the new news story is now a projected 3 feet sea level rise.
    Can anyone out there in the blogosphere tell me if they saw the same methane sea stack article I saw in the newspaper last week, and can anyone out there tell me if the 3 feet sea level rise and 12 degree Farenheight rise is accurate, so that, when the apocalypse comes, I will have managed to spend all my money in my bank accout so as not to lose it when utter and comlete anarchy takes over on planet earth.
    Despite my paltry attempts at humor, I’d really like a response. My e mail is listed below.I’m now very, very, very worried about the seabed methane seastack observations.
    Mark J. Fiore
    45 Villa Terrac
    San Francisco CA 94114

    Comment by Mark J. Fiore — 21 Oct 2008 @ 1:21 PM

  4. We used to have a Nature Conservancy Council for Scotland (part of the UK NCC) here as well, with a sound science base and respected record. But alas, it was emasculated and renamed “Scottish Natural Heritage” in the early 1990s by the UK Conservative Government (with whose prime minister, Margaret Thatcher, who came to power in 1979, you will be familiar).

    Scottish Natural Heritage almost never buys land, and doesn’t object to planning applications even for housing estates in the few remnants of ancient (old growth) woodlands that remain in Scotland. Its most recent chairman, Andrew Thin, was formerly chairman of Scotland’s second and largest national park in the Cairngorms. At the first large public meeting after its establishment in 2003, he announced that the three greatest priorities for the Cairngorms National Park were “housing, housing, housing.”

    Sorry to be somewhat parochial, but we are sometimes tempted this side of the Atlantic to imagine that we are ahead of the US in responding to global warming and environmental destruction. Your article indicates that that is not always the case, particularly with respect to the latter.

    Comment by Slioch — 21 Oct 2008 @ 1:24 PM

  5. I think Jim Hansen has overestimated what the climate system is capable of handling in the long term. I say less than 300 ppm CO2e.

    Comment by David B. Benson — 21 Oct 2008 @ 1:28 PM

  6. Mark,

    Your information is not very good. Methane responses are potentially a large long-term effect and might have minor implications over comingdecades, but the world is not going to end thsi century.

    P.S.– just multiply by (5/9) to go from change in F to change in Celsius. For absolute values (not changes) you also need to add (C to F)or subtract (F to C) 32.

    Comment by Chris Colose — 21 Oct 2008 @ 1:29 PM

  7. Whether 2 degrees is the increase to avoid is one question and what emissions-associated radiative forcings to avoid in order to do so is another.

    As I understand it, the IPCC takes no position on the former, but if given the 2 degree target, then we need to target 450 CO2-eq.

    While there is no preordained one-to-one correspondence between CO2 concentration and CO2-eq concentration, Table 5.1 in the AR4 suggests that, for the IPCC 2007, given a 2 degree target, the CO2-alone target would be ca 350 ppm (which can be explained by the IPCC-relevant scenarios not having forcings from non-CO2 emissions continue to cancel each other).

    Is this reading correct?

    If, additionally, Hansen’s analysis shows that we actually need to target 350 CO2-eq, and we, with the IPCC, assume (if those scenarios can be called assumptions) that non-CO2-emissions forcings will not continue to cancel each other, then CO2-alone targets (whether rhetorical or not) need to be well below 350 ppm.


    Comment by paulina — 21 Oct 2008 @ 2:21 PM

  8. You cannot produce a temperature or concentration target using science alone. You need to use science to generate the best possible predictions of the effects of different levels of temperature range, as well as the likelihood of reaching and particular level of change on the basis of any concentration. You then need to make an ethical and economic decision about how much damage you are willing to accept, as well as how much caution you should employ in the face of risk and uncertainty.

    That being said, scientists could definitely do some very useful work in clarifying the issue of choosing a stabilization pathway.

    [Response:Well said. I agree! The point is without more clarity from scientists, it is hard to do the risk assessments. Of course there *are* several papers available that attempt to provide such clarify, but there is no authoritative document.–eric

    Comment by Milan — 21 Oct 2008 @ 2:47 PM

  9. I had a coworker who spent a summer internship doing legal work a few years back for the Nature Conservancy and she mentioned NC’s plans to do more policy work. I guess she was talking about things like this.
    With NC’s prestige and body of scientific knowledge they could make some valuable contributions.

    The Nature Conservancy has property all over the US which are great places. I would encourage people to find nearby Nature Conservancy properties and visit.

    Comment by Joseph O'Sullivan — 21 Oct 2008 @ 2:48 PM

  10. This is a great post. I’ve been a member of the Nature Conservancy for years and have supported their goals as well as I can with my limited resources. Eric – thank you for sharing your expertise with them. All of the RealClimate folks should be proud that it has become a benchmark for quality science blogging.

    One question . . . if the goal is 450 ppm CO2 eq, where are we today? I know that we are currently about 385 ppm CO2 but I don’t know the delta for the other GHGs.

    Thanks, Phillip

    [Response: Because of aerosols, for which the forcing is negative, we are actually at about the same CO2 ppm as we are at CO2eq. See our post on CO2e.-eric]

    Comment by Phillip Shaw — 21 Oct 2008 @ 3:22 PM

  11. Chris,

    I thought methane effects were more short-term than long-term. Does not methane dissipate from the atmosphere 5-10X faster than CO2? I thought methane lingered for approximately 10 years rather than CO2’s 100 years? I realize all these numbers are inexact, but they do indicate some approximation. Why then would methane’s effects be longer-term as you indicated, rather than shorter-term?


    Comment by Andrew — 21 Oct 2008 @ 3:50 PM

  12. I thought it was all abnout the charney limit, 550 ppmv for a 3C rise (most likely) but then James Hansen comes along and talks about Earth sensitivity (real climates term in their recent post on the subject) being over many decades or even a century or two being double this limit. Hence 450 ppmv of CO2e might destroy more than we care to admit or presently know.

    Comment by pete best — 21 Oct 2008 @ 3:52 PM

  13. Phillip Shaw (10) — My amateur understanding is that it just happens to be the case that all the other forcings approximately balance out so that 385 ppm CO2 ~ 385 CO2e.

    Comment by David B. Benson — 21 Oct 2008 @ 3:56 PM

  14. Andrew @11, but over that 10 years methane is many times more potent than CO2. And remember what methane breaks down into, namely CO2 and H2O, so it’s carbon stays in the atmosphere.

    Comment by Jim Eager — 21 Oct 2008 @ 4:26 PM

  15. What happens with 2 K warming? Here is a review of Mark Lynas’s “Six Degrees” which summarizes his studies:

    What will climate change do to our planet?:

    Comment by David B. Benson — 21 Oct 2008 @ 6:07 PM

  16. Phillip Shaw (#10),

    The IPCC summarised the combined radiative forcing of CO2, other long-lived greenhouse gases, aerosols, and landuse changes as follows:

    “Atmospheric CO2 concentrations [reached] 379 ppm in 2005 … The direct effect of all the long-lived GHGs is substantial, with the total CO2 equivalent concentration of these gases [in 2005] estimated to be around 455 ppm CO2-eq (range: 433-477 ppm CO2-eq). The effects of aerosols and landuse changes reduce radiative forcing so that the net forcing of human activities is in the range of 311 to 435 ppm CO2-eq, with a central estimate of about 375 ppm CO2-eq.”

    See the IPCC (2007) Working Group III report at page 102, available at

    Comment by Chris McGrath — 21 Oct 2008 @ 6:22 PM

  17. The question of what levels of greenhouse gases constitute “dangerous climate change” seems to cry out for a full post from RealClimate, rather than being treated as merely an aside here.

    The policy objective of avoiding “dangerous climate change” comes from Article 2 of the United Nations Framework Convention on Climate Change 1992 (UNFCCC), which states three qualitative criteria for what this means:

    “The ultimate objective … is to achieve … stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner.”

    Considering current levels of greenhouse gases appear likely to completely alter the Arctic sea ice, it seems obvious that we have passed the threshold of radiative forcing sufficient to cause of “dangerous climate change.”

    Considering one of the world’s most sensitive ecosystems, coral reefs, stabilising greenhouse gases and aerosols around 350 ppm CO2-eq and allowing a rise in mean global temperature of 1°C appear to be the highest targets that should be set if coral reefs are to be protected from serious degradation.

    There is a discussion of the policy objectives necessary to protect Australia’s Great Barrier Reef at

    The 450 ppm CO2-eq / 2°C targets will lead to dangerous climate change. The decision by the EU and many conservation groups to focus on them is driven not by the science or close adherence to the criteria in Article 2 of the UNFCCC, but pessimistic assumptions on what is practicable and politically feasible to achieve in the real world.

    Comment by Chris McGrath — 21 Oct 2008 @ 6:24 PM

  18. Andrew @11: What Chris (@6) was talking about was not methane emissions, but rather methane feedbacks: eg, methane clathrates and permafrost releases. And I think he is right that researchers in the field, despite some recent results, mainly believe that these positive feedbacks will be small in comparison to anthropogenic emissions this century. Next century, all bets may be off (there’s a LOT of carbon locked up in the permafrost).

    Philip Shaw @10: Depends on what calculation you do. claims 422 CO2e using CO2 + CH4 + N2O (I calculate 430 for that same combination). One could argue we’re at 458 CO2e using the basket of 6 Kyoto gases and the Montreal gases. Or one could, as I presume David Benson (@13) has done, take the net anthropogenic forcing of about 1.6 W/m2, in which case, yes, we’d be at about 385 CO2e. Of course, if you believe that we _will_ clean up SO2 + BC + the other tailpipe emissions in the near future (none of which are stock pollutants), then we’re closer to the higher numbers than the lower numbers…

    Comment by Marcus — 21 Oct 2008 @ 7:55 PM

  19. On targets: It has been my personal opinion for a while that all this talk of long term targets and Kyoto caps and stabilization pathways has been an unfortunate distraction from what we _should_ have done (and perhaps should still do, though we’ve lost a decade, unfortunately).

    Namely, if I were to write up a list of attributes of the ideal climate policy that Congress would pass next session it would include this:
    a) A low carbon price – either a tax, or a cap-and-trade with a low safety valve.
    b) A clear progression of upward costs of either the tax or the safety valve (5% a year or so)
    c) A clear mechanism by which, as the science and economics and international situation inform, Congress can adjust the rate up or down as needed.
    d) Appropriate mechanisms to balance the regressive nature of higher energy prices, and to compensate those states/industries most badly damaged WITHOUT subsidizing their continued existence.
    e) Incentives/tariffs/bilateral or multilateral agreements/GEF funding/whatever to encourage other international actors to follow suit in an appropriate (but not necessarily identical) way.
    f) A few additional policies to deal with areas in which the incentives don’t work right (eg, tenant/landlord issues, energy research and public transit subsidies, standards to deal with less-well characterized sources that may not work so well under economic instruments such as agricultural methane, N2O, or BC, and public information campaigns).

    My reasoning is thus: We aren’t yet near the point at which we can really define what “Dangerous Anthropogenic Interference” with the Climate System might be in terms of temperature. We aren’t yet near the point where we can determine a temperature from concentration without large uncertainty. We aren’t at the point where we can make good estimates of costs of meeting emissions targets. We _DO_ know, however, that climate change is likely to be a problem, that we should start earlier rather than later, that a price signal will stimulate conservation and energy technology investment and deployment, etc.

    My speech to green groups would be: You always claim that reducing carbon emissions will be cheap. So, we shouldn’t need a large price. And isn’t a small price now better than no price? Also, you believe that climate change signals will become clearer every year. So put a little trust in our future Congresses to recognize that and increase the prices appropriately.

    My speech to industry would be: take a low, certain price now and a fairly clear path forward rather than an uncertain price (possibly large, possibly zero) in the future. Every industry person I talk to claims they hate policy uncertainty. And if you are a climate skeptic, you believe that the lack of warming should eventually become clear. So put a little trust in our future Congresses to recognize that and decrease the prices appropriately.

    But I realize I’m politically naive, and my approach would never work. Alas.

    Comment by Marcus — 21 Oct 2008 @ 8:10 PM

  20. Surely there are sufficient indications that we are already at a tipping point for dear Gia. Ignoring mans own efforts today’s climate is giving us melting glaciers, melting ice sheets, advancing desertification, rotting tundra, increased storm intensities and now dismantling calthrates.

    No point fretting about what doubling CO2 will do, or about ‘sensitivities’. We know enough to know that the time to do a U-turn is NOW! Every step forward in the business-as-usual (or worse the business-as-likely) direction merely takes us deeper down a black hole of our own creation.

    We know we have a car wreck – telling us the tail light is broken too is kinda surplus information!

    Comment by Nigel Williams — 21 Oct 2008 @ 8:11 PM

  21. Finally: thanks for an interesting post. I approve of Nature Conservancy’s tactics, and would love to see their reasoning and science posted in a clear blog fashion paralleling that of realclimate.

    I was impressed with this USA Today article about the Nature Conservancy and their thinking about protecting ecosystems in the face of climate change:

    Comment by Marcus — 21 Oct 2008 @ 8:13 PM

  22. Eric, a sandbox-I question if I may. I’m not familiar with the term 450ppm “CO2 radiative equivalent.” My gut guess is that it is a concentration of all greenhouse gases normalized to CO2 concentration. Is this correct? If so what ballpark concentration would CO2 be with 450ppm CO2 radiative equivalent?

    Comment by Rod B — 21 Oct 2008 @ 8:57 PM

  23. Phillip (10),


    Comment by Arch Stanton — 21 Oct 2008 @ 8:59 PM

  24. I understand it somewhat differently.

    If the GHG concentration reaches 450 ppm and stays there for a while (path matters: how long we take to get there, how long we stay there, how rapidly we reduce afterwards), there is a 50% chance that the temperature increase this century will be less than 2.0°C, and 50% that it will be larger. There is a 90% probability that the increase will be between 1°C and 3.8°C. The 5% tails go to 0.8°C and up to 5°C or warmer.

    So stabilizing at 450 ppm CO2e doesn’t guarantee that the temperature increase will stay below 2°C.

    It’s worth pointing out that International Energy Agency’s Energy Technology Perspectives ( describes the path to a median probability of a 2.4°C increase as difficult, eg, requiring unprecedented levels of cooperation. Also, the current rate of increase in GHG emissions is faster than the fossil intensive scenario in IPCC (well, it was up until very recently).

    If we want a greater than 50% chance of a 2°C cap, we need to reduce GHG emissions even faster than the ambitious and possibly expensive proposal from IEA.

    I support rapid reductions. I’m for paying what it costs, and finding ways to limit our choices, so flying and driving and etc become less attractive choices. I just raise this issue because discussions of a 2°C cap occur in the public, but I am not seeing such discussions from groups like IEA.

    Comment by Karen Street — 21 Oct 2008 @ 8:59 PM

  25. Re #11 and 14, I think the real danger is the speed with which the methane hydrates and permafrost melt. If enough methane is put into the atmosphere within a 10 year frame, that could really compound and add up to a lot of warming, & also speed up the melting of the rest of the frozen methane emissions even faster.

    It seems to me that this human-induced warming episode is a much faster warming than any episode in the past.

    Comment by Lynn Vincentnathan — 21 Oct 2008 @ 9:38 PM

  26. Hi Andrew,

    I actually wasn’t referring to the atmospheric residence time of the gas (which is about 10-12 years), but rather the transition timescale for a tipping point of mass release of methane from seafloor hydrates (which Lenton et al 2008 put on the order of 100 to 100,000 years). Permafrost release (as opposed to methane on the seabed) of CO2 and CH4 is a gradual thing over this century, and that will probably be non-trivial but not the doomsday scenario as portrayed in comment #3.

    Comment by Chris Colose — 21 Oct 2008 @ 9:53 PM

  27. “its method of protecting land: buying it. Neither free-market boosters (if there are there any remaining) nor lefty environmentalists have any trouble with this.”
    Wrong. It is a class warfare issue. The Nature Conservancy is denying habitat for humanity. Housing for humans IS an issue. Poor people, and that includes new graduates with jobs, are made homeless or inadequately housed by the Nature Conservancy. Nobody has the foresight to build cities on the badlands so that housing can be built in a place where the Nature Conservancy isn’t interested. Then again, there is no place where the Nature Conservancy isn’t interested. Nobody has the foresight to create factories and jobs in the badlands. Nobody is doing planning at that level. The Nature Conservancy would find some reason why we shouldn’t build houses in a lifeless place, like on the moon. The Nature Conservancy is just a means of excluding everybody who earns less than some threshold, like $250,000/year, and a means of raising the price of land so that the wealthy can increase their profits.

    Cities are built upside down: The buildings are where the parks should be and the parks are where the buildings should be. Look at San Jose, CA or Vancouver or Anchorage. The city is next to the sea level and the mountain tops are uninhabited. The cities should be on the mountain tops where sea level rise will not affect them. History has put cities in the farmland. The cities should be at higher altitude where the soil is untillable, but where we live is dictated by history and the Nature Conservancy.

    Global warming makes the Nature Conservancy’s efforts useless anyway. Polar bears, for example, should be counted as extinct already because global warming will surely make them extinct. For every one species the Nature Conservancy and the Endangered Species Act saves, a thousand go extinct because of global warming. The Nature Conservancy is the epitome of impracticality. The Nature Conservancy will die when Homo Sapiens goes extinct in a century or 2. The Nature Conservancy may as well not exist now. It should be disbanded or re-organized to concentrate its efforts exclusively on global warming. The Nature Conservancy should sell all the land it owns now and buy up coal mines to prevent the mining of coal because burning coal to make electricity is the thing that will make Homo Sapiens extinct.

    I have also heard about methane escaping from the Arctic ocean and from melting permafrost. I saw pictures of snow seemingly on fire because of methane escaping from tundra. I didn’t keep the reference, but a NASA or other science web zine seems a likely place to find it. Since this huge positive feedback has begun, I have heard nothing from RealClimate on how this changes everything, or even confirmation or denial from RealClimate. If this positive feedback is unstoppable, the methane alone makes The Nature Conservancy already irrelevant. Natural positive feedbacks already in action mean that the present 380 ppm CO2 is already past the threshold beyond which we humans can control the climate and prevent our own extinction. Yet RealClimate ignores this issue and continues to talk about 450 ppm equivalent or more as the threshold. Why?

    Comment by Asteroid Miner — 21 Oct 2008 @ 10:16 PM

  28. (3,6) I tend more towards Chris’ position here. We need to numerically evaluate the expected rate of any potential Methane release. Presumably methane hydrate decomposition requires the thermal pulse (from a delta T of climate change) to diffuse downwards through water/mud, and in the permafrost case permafrost. Beyond the top couple of meters, isn’t the timescale of thermal diffusion too long for a significant volume of methane hydrates to be involved? (Note this is a question, not an assertion, real data, and real numbers, and some simulation must be performed to make decent predictions). In any case, it is my observation that the number of laymen who are frightened of a runaway methane-hydrate release triggered by climate change is not a trivial number. Perhaps RC should do a post on what is known about this subject. Otherwise the considerable angst generated by the information vacuum will persist.

    Comment by Thomas — 21 Oct 2008 @ 10:35 PM

  29. I wouldn’t worry to much about methane, it’s been warmer during previous interglacials and the polar bears did just fine.

    Comment by don — 21 Oct 2008 @ 11:23 PM


    Published: October 18, 2008

    WASHINGTON (AP) — The Interior Department has advanced a proposal that would ease restrictions on dumping mountaintop mining waste near rivers and streams, modifying protections that have been in place, though often circumvented, for a quarter-century.

    The department’s Office of Surface Mining issued a final environmental analysis Friday on the proposed rule change, which has been under consideration for four years. It has been a priority of the surface mining industry.

    30 days to comment.

    Comment by Hank Roberts — 22 Oct 2008 @ 12:36 AM

  31. Maybe a pendant on the CO2E thing ought ot notice another little AGW misaprehension which is repeated here, vis, “ecosystem change with … changes in precipitation”. What matters to tallgrass prairie, as to vegetation everywhere away from the wettest regions, is soil moisture – not precipitation.

    Specifically, it is the depth, duration and frequency of soil moisture deficit which tends to determine vegetation communities. And as climate scientists well know, soil moisture is a complex temporal function of both precipitation and evapotranspiration. AGW may well decrease the former in the midwest (or markedly alter its temporal distribution), but it is virtually certain to increase the latter. As a first approximation, potential evapotranspiration is a direct function of mean temperature. In Australia, we’re realising that changes on both sides of the soil moisture equation are important to increasing aridity.

    [Response: A very good point. Of course the Nature Conservancy folks know this too; I was just giving an example of the kind of thing they need to think about, that motivates their concern about climate change. But my example would have been better had I simply said soil moisture, as you point out. Thanks for adding that.–eric]

    Comment by GlenFergus — 22 Oct 2008 @ 4:36 AM

  32. don (29),

    I’ve seen this argument used by Bob Carter. From what I understand, polar bears as we know it evolved after 120kya so no previous interglacial would really provide a decent analog to a continued rise in CO2 over this century. Didn’t Cecilia Bitz and others project a seasonally free arctic sea ice at 2040? Again, no biologist, but everything I read shows that polar bears depend heavily on year-round ice. And the arctic ecosystem is changing on many levels– not just the polar bear


    Comment by Chris Colose — 22 Oct 2008 @ 8:06 AM

  33. #29. Molecular clock data show a rather messy and very rapid speciation event for polar bears, and I am not sure they were around (or that they persisted) during the Pleistocene interglacials. You may be correct, but you certainly do not make a strong argument.

    Comment by TomRooney — 22 Oct 2008 @ 9:15 AM

  34. #29. The polar bear represents a recent speciation event, and the extant lineage may not have existed during prior to the final glacial event during the Pleistocene.

    Comment by TomRooney — 22 Oct 2008 @ 9:22 AM

  35. Not sure if this is a relevant post for this question ….. can anyone tell me how much of the T rise between an ice age and an interglacial period is due to the CO2 forcing alone (ie. without other feedbacks – which were happening anyway). How much global T rise does an increase in CO2 from 180ppm to 280ppm give ? On its own. All I have is the commonly quoted number of 1 degree F for every doubling of CO2 (without additional feedbacks). So the 180 to 280 ppm CO2 increase should contribute about half a degree F ? Give or take – is this roughly correct ?

    Comment by John C — 22 Oct 2008 @ 9:35 AM

  36. Clearly, the 2°C/450 ppm numbers have completely permeated the policy-advocacy realm. Yet while they are arguably derivable from the IPCC reports, it is actually not clear to what extent the larger scientific community really believes these are the right numbers. There simply has not been a process to evaluate this that compares in depth and breadth with the IPCC. A new and much more comprehensive analysis, by a much greater group of scientists, would be valuable at this juncture.

    YES! The IPCC has previously convened special workgroups to tackle important issues. This is strongly needed, there is much confusion out there on what the IPCC has and has not said.

    Comment by John Wilson — 22 Oct 2008 @ 10:16 AM

  37. Asteroid Miner wrote: “Poor people, and that includes new graduates with jobs, are made homeless or inadequately housed by the Nature Conservancy.”

    What in the world are you talking about? Got specifics? Evidence? Anything?

    Comment by SecularAnimist — 22 Oct 2008 @ 11:07 AM

  38. I’m glad the subject of targets has been raised again (having gone on about it for months I would say that, I suppose!) Eric’s call for a new scientific analysis is welcome, but how can this be arranged with all due haste? Copenhagen 2009 is now only 14 months away, and I guess the community can’t just dump it on their conference on day one. But they do need more to go on – as many here have said, there is literally a world of difference between a very hard 450ppm target that won’t do what is required, and a very very very hard 350ppm target that hopefully will.

    This question – surely – is the most pressing that Real Climate can engage in.

    Comment by Guy — 22 Oct 2008 @ 11:10 AM

  39. Re don @29: “I wouldn’t worry to much about methane, it’s been warmer during previous interglacials and the polar bears did just fine.”

    But how did our agriculture, coastal cities, ports, refineries and other infrastructure do during previous interglacials?

    Oh, right, there weren’t any.

    Comment by Jim Eager — 22 Oct 2008 @ 11:41 AM

  40. Last year, I delivered my State of the Oceans presentation to the Nature Conservancy branch in Seattle. They showed me one of their planning maps for the Puget Sound, and I was very impressed. They have a sophisticated rugosity model, and the use this to plan their habitat buys. Made me want to do computer modeling for them!

    Comment by Jim Galasyn — 22 Oct 2008 @ 12:56 PM

  41. Don, the polar bear species is, at most, 200,000 years old, which means it has seen only one interglacial. Like humans.

    Comment by Jim Galasyn — 22 Oct 2008 @ 1:00 PM

  42. After comment #10 and the response, I should retract my comment in post #2 on “It says nothing about other aerosols or GHGs either which presumably should cause a positive radiative forcing over the coming century.” I was not thinking of the equivalent– live and learn.

    Comment by Chris Colose — 22 Oct 2008 @ 1:08 PM

  43. Chris Colose (32) — According to Wikipedia

    According to both fossil and DNA evidence, the polar bear diverged from the brown bear, Ursus arctos, roughly 200,000 years ago.

    which implies polar bears survived

    “Less Ice In Arctic Ocean 6000-7000 Years Ago”:

    and presumably even less during the Eemian interglacial.

    [Response: Guys, I’m not claiming expertise on polar bears, which I don’t have. But the comparison with the last interglacial, and the Eemian, is not necessarily at all relevant. In neither of these past times did it get warm as fast as is happening now. Rates matter, usually more than magnitudes. In any event, we may well be heading for warmer-than-Eemian in the long term–eric]

    Comment by David B. Benson — 22 Oct 2008 @ 2:12 PM

  44. David (43), thanks

    I just did a bit of research out of curiosity. I’m not well read in polar bear evolution here, but I think whoever wrote the wiki article misread the reference. Reference 14 in the wiki article says, “polar bears are thought to have originated from a segment of the Siberian populations of brown bears (Ursus arctos) which was isolated during the glacial advanced of the mid-pleistocene.”

    A more thorough and recent document says, “It has been proposed that polar bears are believed to have originated from a group of grizzly bears (Ursus arctos) which became isolated during the glacial periods of the mid-Pleistocene approximately 200,000 – 250,000 years
    ago (Talbot and Shields 1996b).”

    and also,

    “Based on the relatively few specimens of polar bears in the fossil history Kurten (1964) estimated that polar bears may have evolved as recently as 70,000 to 100,000 years ago….Age models based on molecular studies of evolutionary relationships among extant species of bears differ considerably as to the divergence time of polar bears from grizzly bears. Wayne et al. (1991) suggested this happened 70,000 – 100,000 yrs ago while Yu et al. (2004) concluded this might have happened 100,000 – 150,000 yrs ago.”

    I read this as geographic isolation began ~200 kya and actual “polar bears” evolved ~100 kya, presumably there would be quite a long time for speciation to occur. I don’t really know how significant the distinction is when it comes to the dependance on sea ice, but the report also divides polar bears into 19 populations, which would be different back in the last interglacial. I suppose various populations would be effected differently by sea-ice losses, depending on nearby landmass.

    The main point is I still doubt the last interglacial is an appropriate paleoclimate-paleobiological proxy for how modern polar bears will fare, especially as we approach later in the century. I don’t doubt that there was less sea ice in the mid-Holocene a few thousand years ago because of more summer sunshine (how do you get a good sea ice extent proxy though?), but we don’t know how polar bears were effected or adapted back then.

    Comment by Chris Colose — 22 Oct 2008 @ 3:21 PM

  45. Well, one magnificent difference… There were no ~6.74 billion homo sapiens sapiens to encroach on their habitat and areas of retreat, nor were any other Arctic regulars under threat that the PB was living off. Any recent counts on Bow heads e.g.

    Was 6-7 thousand years ago not a period when the last mammoths died out? Was 6-7 thousand years ago, half way from the last main glacial period, the climate fully stabilized? Was it then not when the Oceans rose or finished their rise to cause for instance the Black Sea to go from sweet to salt? Then is not now me thinketh.

    Comment by Sekerob — 22 Oct 2008 @ 4:37 PM

  46. Bow heads live of what? The PB did not live specifically of Bow heads of course. Will there this time around develop dead-zones in the Arctic Ocean due men’s contribution to the water quality?

    Comment by Sekerob — 22 Oct 2008 @ 4:41 PM

  47. Regarding polar bears, when the earth warms they will evolve very rapidly into another new subspecies of brown bear that will survive on the diet available to them at that time. They’ll have do less swimming amongst the ice for fish and will spend more time digging for grubs. The ones that don’t adapt… well that’s evolution!

    Comment by Ed — 22 Oct 2008 @ 4:54 PM

  48. He’s back….

    An open letter from The Viscount Monckton of Brenchley to Senator John McCain about Climate Science and Policy

    Too bad he’s courting the wrong candidate

    Comment by Dill Weed — 22 Oct 2008 @ 4:57 PM

  49. John C writes:

    How much global T rise does an increase in CO2 from 180ppm to 280ppm give ?

    Myhre et al. 1998 give the radiative forcing equation for CO2 in the 1-1,440 ppmv range as

    RF = 5.35 ln (C / Co)

    where C and Co are final and beginning values in ppmv. 5.35 ln (280 / 180) is about 2.36, so the extra radiative forcing would be 2.36 watts per square meter. With a climate sensitivity of 0.75 K/W/m2 this yields a change in temperature of 1.8 K.

    Comment by Barton Paul Levenson — 22 Oct 2008 @ 5:05 PM

  50. Mark Fiore…(Comment #3)…You are one of my favorite cartoonists of all time.


    Comment by Jason — 22 Oct 2008 @ 7:24 PM

  51. RE #27, and the methane issue. RC has covered it & presented a possible (though not probable) disaster scenario. See:

    And BTW, a portion of CO2 could be in the atmosphere for up to 100,000 years, a lot more than the 100 years most people talk about. See:

    I see your point about the rich buying up the good land, but what we need is better urban planning, and rural planning. And a society that makes sure that all people have good, affordable housing, without harming the environment.

    When I went to Germany 20 years ago and saw all their houses built so well, with thick walls and tile roofs, I turned to our German friend and asked where the poor people lived (since I didn’t see any bad, ramshackle houses), and she said they live in these same good houses, perhaps more people per house, but in these good ones. Why is our nation (U.S.) so behind in important things?

    Comment by Lynn Vincentnathan — 22 Oct 2008 @ 7:40 PM

  52. > Rates matter, usually more than magnitudes

    Easy to find in the journals. Just one example of many:

    Science 27 April 2001:
    Vol. 292. no. 5517, pp. 673 – 679
    DOI: 10.1126/science.292.5517.673

    Range Shifts and Adaptive Responses to Quaternary Climate Change
    Margaret B. Davis,* Ruth G. Shaw

    Tree taxa shifted latitude or elevation range in response to changes in Quaternary climate. Because many modern trees display adaptive differentiation in relation to latitude or elevation, it is likely that ancient trees were also so differentiated, with environmental sensitivities of populations throughout the range evolving in conjunction with migrations. Rapid climate changes challenge this process by imposing stronger selection and by distancing populations from environments to which they are adapted. The unprecedented rates of climate changes anticipated to occur in the future, coupled with land use changes that impede gene flow, can be expected to disrupt the interplay of adaptation and migration, likely affecting productivity and threatening the persistence of many species.

    Comment by Hank Roberts — 22 Oct 2008 @ 9:57 PM

  53. Re # 27 Asteroid Miner

    “Look at San Jose, CA or Vancouver or Anchorage. The city is next to the sea level and the mountain tops are uninhabited. The cities should be on the mountain tops where sea level rise will not affect them. History has put cities in the farmland. The cities should be at higher altitude where the soil is untillable, but where we live is dictated by history and the Nature Conservancy.”

    I’m guessing it is far cheaper to build and operate cities at sea level than in the mountains. Can you give a single example of a city who location was dictated by the Nature Conservancy?

    Comment by Chuck Booth — 22 Oct 2008 @ 10:13 PM

  54. odd, post gone.

    Comment by Sekerob — 22 Oct 2008 @ 11:22 PM

  55. okay, I only see my posts when I post again which is even odder. Did ctrl-f5 to specifically refresh page.

    @ mod. plz feel free to delete these latter 2. Tech glitch maybe.

    Yes, I’m human. No RFID chip implant yet, nor bar-code on back of neck.

    Comment by Sekerob — 22 Oct 2008 @ 11:25 PM

  56. Re eric in no. 43: “In neither of these past times did it get warm as fast as is happening now.” How can you know that? We see a rise of around 0.7 degC in the past century – from instrumental data. Any type of proxy is smoothed compared to instrumental data, and has an error margin of typically around 0.2 degC (see Mann et al 2008)- though the error is variable. So, I don’t believe you can demonstrate that the recent rate of temperature rise is exceptional or unprecendented.

    Comment by PHE — 23 Oct 2008 @ 1:35 AM

  57. Polar bears … find me any era when climate changed as fast as projected for this century, and you’ve probably found a mass-extinction event (I’m not sure if there has been a comparable event; time scales for example during the Permian-Triassic extinction are hard to pin down precisely this long after the event).

    In another form of response, there are people in the UK arguing for a “Green New Deal“, emphasising economic sustainability, not just the climate (an idea I picked up independently).

    We need to couple arguments about climate change with sound economics to debunk those who claim that we will destroy the economy if we deal with the science the way we should (luckily, the same people who are making these claims are now revealed as economic incompetents as well, so we have some chance).

    While some may consider the economic debate irrelevant if we are facing the possibility of destroying the conditions that make large-scale human society viable, it seems to be just as well to fight on all fronts, as climate inactivism is a many-headed monster.

    Comment by Philip Machanick — 23 Oct 2008 @ 3:52 AM

  58. The references for Contraction and Convergence [C&C] provided by its author GCI are: –

    The description of C&C given on the RealClimate website attributed to GCI was not provided by GCI and the Hohne Report which compares C&C with CBDR is inaccurate and generically inappropriate.

    Comment by Aubrey Meyer — 23 Oct 2008 @ 5:39 AM

  59. PHE writes:

    Re eric in no. 43: “In neither of these past times did it get warm as fast as is happening now.” How can you know that? We see a rise of around 0.7 degC in the past century – from instrumental data. Any type of proxy is smoothed compared to instrumental data, and has an error margin of typically around 0.2 degC (see Mann et al 2008)- though the error is variable. So, I don’t believe you can demonstrate that the recent rate of temperature rise is exceptional or unprecendented.

    So your position is that the present rise is unexceptional because it might have happened in the past, although we have no evidence for it? Some kind of logic-alone reasoning about climate in the ancient Greek style, evidence be damned?

    Comment by Barton Paul Levenson — 23 Oct 2008 @ 5:41 AM

  60. Thanks Barton. I’m just a little confused because I am pretty sure I heard that a doubling of CO2 would only cause the temeperature to rise by 1 degree F … without additional amplification feedbacks.

    Comment by John C — 23 Oct 2008 @ 7:13 AM

  61. Here’s another thing to get you worried: check out what the British Antarctic Survey is saying about the Amundsen Sea Embayment. There’s a possible 1.5 metre sea level rise of uncertain likelihood. More here: recent ice thinning is happening at more than 10 times the rate over the last 14,500 years.

    Comment by Philip Machanick — 23 Oct 2008 @ 7:33 AM

  62. # 60 (John C)

    The 0.75 K/W/m2 number Barton used includes feedbacks. That number is how you go from a change in forcing to a change in temperature. To get it you simply divide the change in temperature (~3 C) for a doubling of CO2, by the radiative forcing for a doubling of CO2 (4 W/m2). So the no-feedback number would be about 0.3 K/W/m2 if the no-feedback temperature change is 1.2 K (not degree F by the way).

    Comment by Chris Colose — 23 Oct 2008 @ 11:51 AM

  63. John C: A doubling of CO2 should lead, absent feedbacks to about 1 degree C of warming (not F).

    Comment by Marcus — 23 Oct 2008 @ 11:56 AM

  64. John C., I wonder if you might not be falling into a common trap–that of thinking that CO2 by itself would be benign if we could just show that all the feedbacks are exaggerated. The thing is that the feedbacks apply to any forcing, not just CO2, so if you impose lower feedbacks in the model, you wind up with less responsiveness to changes in solar irradiance, volcanic forcing, etc. Again, the models fail very badly to match the real world when you decrease feedbacks. It doesn’t really pay to consider forcers independent of feedbacks–that’s not the world we live in.

    Comment by Ray Ladbury — 23 Oct 2008 @ 12:22 PM

  65. John C, I think your question was answered here:

    You’re thinking of the purely hypothetical experiment in which the number of CO2 molecules in the atmosphere is doubled, instantaneously, with no other change.

    This is a physics thought experiment you’re recalling.

    I hope the physicist who likes to talk about this number finds a way to _cut_ the number of CO2 molecules by half, instantaneously, with no other change — thus solving the problem. Just find a way to pull the right strings ….

    Comment by Hank Roberts — 23 Oct 2008 @ 12:46 PM

  66. RE: BPL (59). Sounds like you’re trying to belittle me. That’s not very scientific. I think you are misunderstanding my logic. To claim that the RATE of temperature rise is greater now than in the past, you need evidence. Comparing short wavelength instrumental data to long wavelength (ie. smoothed) proxy data is not satisfactory evidence.

    [Response: This is a fair point (sort of; I don’t want to get into another debate about the “hockey stick” here). It is probably strictly true that one cannot (yet) demonstrate that the rate of temperature increase is unprecendented. The rate of CO2 rise is, however, unprecendented at least in the last 100s of thousands of years. That’s the relevant point for thinking about the future. –eric]

    Comment by PHE — 23 Oct 2008 @ 1:33 PM

  67. Re 450ppm CO2 equivalent the AGGI which gives the component gas contributions may be found at NOAA’a website
    This shows we are way above the 450ppm equivalent already but I suspect you are working on increase in other gases, notably CH4, NO2 and CFC’s against a non zero baseline. Is this correct? and if so what do you think the current CO2 equivalent number is. Politically I guess we all know that, barring some unforseen catastophe we are going to get to 450ppm at least whatever we do so we better hope the extreme forecasts are wrong

    Comment by colin Aldridge — 23 Oct 2008 @ 4:09 PM

  68. Chris Colose (44) — Good for you! Wikipedia is a fine starting point, usually, but going to the sources is always wise. Here is another take on polar bears:

    The Hudson Bay polar bear population do fine on land during the (ice-free) summer. I opine that the Arctic Ocean populations can likely do the same. After all those creatures can (and do) still interbreed with brown bears, so (I opine) easily adopt something of the same diet. Brown bears have been around for, at least, more than one million years; that species survived interglacial 4, thought to be warmer than interglacial 2 (the Eemian).

    Eric — Thanks for the response. Rates certainly do matter. Not strictly comperable, because starting from a temperature quite a bit colder than now, at the 8.2 kybp event (seen in Greenland ice cores but also, it seems, in Pacific Warm Pool marine proxies) it certainly appears that the recovery was about as fast as the warming of the last century. (I would like to be able use proxies other than just Greenalnd ice cores, but I don’t know of any other suitable choices which will adequately resolve at centennial scales.)

    Comment by David B. Benson — 23 Oct 2008 @ 5:32 PM

  69. Re # 47 Ed:

    when the earth warms they will evolve very rapidly into another new subspecies of brown bear

    And your basis for making this prediction is what?

    Comment by Chuck Booth — 23 Oct 2008 @ 10:48 PM

  70. To get back to the targets needed…

    Policy makers require a fixed target such as 450 ppm CO2e. This provides for predictable economic and social impacts as the effort to achiev this target can be set.

    The problem is that as time passes the targets become revised. I like the approach of Marcus (19) who allows for modification of the targets over time.

    I am happy to let the policy makers target the 450 ppm because it is such a hugh task to put the mechanism for change in place. In Oz we have had a report by Garneau, an economist that suggests 5 – 10% reductions by 2020 be the initial target. (He does say that 20% would be preferable.) This is for a cap and trade system we are to introduce here by 2010.

    I believe this is too weak and cannot be considered a serious attempt at emissions reductions. However, I can understand why Garneau is proposing this as he sees the problems that accompany the changes. He is focused on getting the system up and running first. Then probably expecting that Australia will follow the 2009 Conference and modify our tergets to align with the international agreements (he explicitly sets out international alignment mechanisms in his report).

    Anyway, the question of 450 or 350 is moot at this point in time. There is simply not the data to be that specific. Certainly Table 2 in IPCC report 4 indicates we would be negligent to accept 550 ppm.

    Comment by Ricki (Australia) — 23 Oct 2008 @ 10:54 PM

  71. Opps,

    sorry that should be Garnaut (see for more info).

    Comment by Ricki (Australia) — 24 Oct 2008 @ 5:16 AM

  72. Since we’re on the tangent of climate sensitivity, am I right in thinking that there’s no real evidence that sensitivity differs significantly between forcings, that the climate response to each should be broadly similar?

    I’m sure we can concede some modest differences (a uniform 1 W/m2 change would presumably give a different response to spatially heterogenous forcing changes with the same mean value), but I don’t envisage a magic mechanism that conveniently reduces climate sensitivity to CO2.

    I’ve recently run into this argument, and I suspect it’s easy to shoot down (there’s a lack of evidence supporting it in the literature for a start). Any takers?

    Comment by Nelson — 24 Oct 2008 @ 6:31 AM

  73. Re 70, I heard a talk Wednesday from someone who had worked as a AAAS fellow with the US Congress. She talked about two types of risk, the risk from not addressing climate change adequately (to stay below 450 ppm CO2e reqires the Annex 1 countries to make a 25-40% decrease from 1990 levels by 2020, even while population increases in many) vs the political risk that nothing will be done if the plan is too ambitious.

    She feels that politically, we are coming to terms here with the idea or returning to 1990 levels by 2020, the California plan.

    All rich countries need to look at our use of coal. Funding for carbon capture and storage was highly inadequate before the world economic meltdown, and it’s hard to see the public accepting this as a make-work project. I mention this because Australia will have a bit of a wrangle on this. If the US and Australia want to export coal, aren’t we obligated to fund research and adequate testing?

    Comment by Karen Street — 24 Oct 2008 @ 7:29 AM

  74. Nelson, How would the climate system know where a Watt of power came from? Yes, adding a Watt at different positions around Earth might produce slightly different results, especially intitially, but I suspect over time, these perturbations would smooth out in a dynamic rotating system without partitions. Of course one exception might be the deep oceans, which interact with the rest of the system only on much longer timescales. However, energy fluxes here are small compared to those at the surface. Just my SWAG as a physicist. I’m sure Gavin or someone else will correct me if I’m wrong.

    Comment by Ray Ladbury — 24 Oct 2008 @ 8:09 AM

  75. Re #70, ricky, its not a matter of 450 ppmv but a matter of how much CO2 the atmosphere can handle in realtion to warming. James Hansen has recently switched to this thinking I believe. I did read an article recently on this matter. I will try and find it.

    Comment by pete best — 24 Oct 2008 @ 9:16 AM

  76. Re: Nelson (@72): Look up “climate efficacy”. There are some outliers (for example, black carbon snow-albedo effect is claimed to have an efficacy of 3x CO2 for a given forcing), but for the most part I think you are correct that any given forcing will have a similar global temperature impact to another forcing of the same magnitude.

    Note that the fingerprint might be different: 1 W/m2 of solar irradiation would be expected to warm the stratosphere and the day-time in different ways that 1 W/m2 of GHG forcing (which would cool the stratosphere and warm both day + nighttime), for example, but the surface temperature change should be within +- 30% or so (I’d guess).

    Comment by Marcus — 24 Oct 2008 @ 9:27 AM

  77. Nelson, I think climate sensitivity has several prior topics still open and continuing. I think you’re right.

    On rate of change, PHE above pastes in the old claim that because we don’t feel the full effect already, there’s no reason to believe it will happen. Same argument that’s made against ocean pH change.

    Bogus. And this is what the Nature Conservancy has found it has to deal with. What we know now is going on, and is clearly going to happen, really does change the goals and methods of conservation biology.

    I hope the topic can be kept focused on the Nature Conservancy’s work rather than accumulating another round of copypaste denial and copypaste refutation of frequently debunked bogosity. We need focus.

    “The warming rate of about 1°C per millennium during the Pleistocene-Holocene transition was an order of magnitude less than the projected changes for the 21st century.”

    ” Our data suggest that climate changes in these systems have been gradual, perhaps averaging less than 1°C per millennium even during the height of the Pleistocene-Holocene transition. Conservatively, if temperatures change only 1°C this century (the minimum International Panel on Climate Change estimate), that rate would be an order of magnitude higher than the fastest rate observed in this record; the projected climate change in the next 100 years will be fundamentally different from any in the last 50,000 years. Given the relatively short geographic distances between elevations and the concomitantly short migration distances required to move among them, Andean plants with broad elevational distributions should be able to remain in equilibrium with climate. For taxa with narrow elevation ranges, however, the predicted rate of climate change may move them completely outside of their climatic niche space within only one or two plant generations. Coupled with habitat destruction preventing colonization from adjacent metacommunities, Andean plant communities may experience greatly increased extinction rates.”
    Cited by 48 articles since publication in 2004. Look it up.

    See also
    CLIMATE CHANGE: Did You Say “Fast”?
    Science 1 August 2008: 650-651
    DOI: 10.1126/science.1159821;321/5889/680
    “The pivotal question in the debate on the ecological effects of climate change is whether species will be able to adapt fast enough to keep up with their changing environment. If we establish the maximal rate of adaptation, this will set an upper limit to the rate at which temperatures can increase without loss of biodiversity.”

    Comment by Hank Roberts — 24 Oct 2008 @ 10:24 AM

  78. You mention using technology to avoid the need to travel to conferences. To a large degree, I think that simply requires a mindset change. I counted up the other day: I think I’ve traveled by plane for business five times in the past nine years. Almost all of the people I work with are scattered around the globe; I’ve never seen the overwhelming majority of them, nor do I ever expect to. The technology has been in place for years to work effectively in distributed settings; the technology is /not/ in place to replicate a collocated work setting through technology. The key is figuring out how to achieve the purpose of the meeting or work under the constraints of the technology (and there are constraints to face-to-face work, too — I’ve found that communications channels are often quite constrained in f2f settings as compared to online work).

    Comment by Bill Harris — 24 Oct 2008 @ 10:24 AM

  79. A little off topic, but have you noticed this handy collection of climate change and other environment related news:

    I keep it open on my browser most of the time

    Comment by John UnDoe — 24 Oct 2008 @ 10:28 AM

  80. Nelson #72

    I doubt that not finding anything about it in the literature necessarily invalidates the argument and not finding a mechanism doesn’t mean it has to be ‘magic’. It may just be yet unknown or underestimated or considered in a totally wrong context. Considering how little we know about so many aspects of climate and how ‘unprecedented’ the entire composition of the various factors is, you’ll probably find noybody who is prepared to definitely rule out that a magic mechanism might be in there somewhere. I, for one, would be very happy if it turned out that – say – Lindzen was right after all with his iris theory or Spencer’s causality argument really turned everything upside-down and we discover, that the sensitivity really was just 1C. I just don’t believe it.

    Comment by dagobert — 24 Oct 2008 @ 2:01 PM

  81. Nelson (72) — There is a ‘magic mechanism’. See Radiative forcing recommendations, NRC report:

    Comment by David B. Benson — 24 Oct 2008 @ 2:03 PM

  82. It seems unlikely that cap-and-trade approaches are going to halt the growth in CO2 concentration in the atmosphere – that will require ending the use of fossil fuels as an an energy source, as well as keeping what remains of the world’s 50-plus year old trees (tropical forests, mainly) intact.

    This is because the way in which offsets are calculated ignores the basics of the carbon cycle. For example, how should forests be valued? Do forests uptake carbon?

    Well, a growing tropical forest stores some ten tons of CO2 per acre per year while growing. A fully mature tropical forest, however, is in steady-state, oxidizing as much carbon as it stores. That’s the normal state of the biosphere, which is why even though the biosphere takes up and emits far more CO2 than humans do each year, the atmospheric CO2 levels did not change until fossil emissions began to rise.

    This is why programs aimed at re-foresting are the ones that will actually increase biosphere carbon storage. It is equally important to preserve mature tropical forests for other reasons – biodiversity, transpiration effects, etc.

    However, if you really are concerned about climate change, then you have to acknowledge that a central goal has to be the elimination of fossil fuels as an energy source – and that is something that the Nature Conservancy is careful never to advocate.

    The fact that Royal Dutch Shell is a contributor might have something to do with it…

    The Shell Conservation Internship Program is made possible by support from Shell Canada Limited. A partner in conservation with NCC for more than 25 years, Shell Canada has donated more than $5 million in financial resources, land and mineral rights to NCC.

    That’s the competition, folks… so perhaps RealClimate could set up a countering donation fund? How many readers are there? We need 500,000 people to donate $10 each, and then you could have a RealClimate Conservation Internship Program at the Nature Conservancy…

    In comparison, the cost of replacing the world’s fossil fuel infrastructure with solar, wind, biofuel, nuclear, geothermal or tidal energy is estimated to be at least $15-20 trillion. For a country with one tenth of the world’s population and energy demand, say, this becomes a somewhat more plausible $1.5-2 trillion.

    On a regional basis, this indicates that at least $200 billion in energy investments would be needed to replace Midwestern coal-fired power plants alone. On a national basis, coal produces about half the electricity used in the U.S., and more in China.

    A whole new approach to the economics of energy is needed, and that’s probably not what the Nature Conservancy is all about – they’re a public land-purchase group, sort of a private version of the National Parks system.

    However, the involvement of Shell in a “nature group” is a bit strange, since Shell is also involved in many of the world’s dirtiest fossil fuel projects, from billions in tar sands investments to offshore Alaskan oil fields to the environmental devastation in the Niger Delta.

    If the Nature Conservancy wants to keep taking money from the fossil fuel industry for land purchases, they should stay out of the climate policy debate entirely, or, failing that, directly address the conflict of interests that are involved, particularly when your directors are also from financial institutions (Goldman Sachs, Blackstone, Capital Research, etc.) that are heavily invested in Exxon, Shell, BP, Conoco and Chevron, as well as in all the major coal-fired utility companies in the U.S.?

    Maybe the NC should instead consider getting some funding from Google, who is also backing renewable energy (servers take a lot of electricity)? Instead of just buying land, perhaps the NC should also think about promoting clean energy?

    [Response: I can’t of course argue that Nature Conservancy has no conflict of interest, and indeed, it probably isn’t appropriate for me to offer an opinion on this at least not on these pages. Still, I will say that I think it is a weak argument to say they should say out of energy advocacy. We are all “tainted” by our love of fossil fuels. And Nature Conservany’s membership will, I suspect, push them much harder than the oil companies might push back. In any case, it is clear that at least some of the oil companies have recognized that regulation changes are on the table, and that they had better prepare for it, if only because companies like to be able to plan for future demand scenarios, so that they can remain profitable. For that reason, some of them are actually pushing for cap and trade. You may think this is simply good P.R. (and you might be right) but nevertheless, there it is. In this context, I found it fascinating during the meeting to see a talk from a Shell exec, who told us about the future energy business “scenarios” they have looked at. In their sort of “best case scramble” scenario (business and governments trying to cut CO2 emissions, but with little coordination), we are still emitting >20 GT a year in 2050. In their “blueprint” scenario, in which cap and trade is serious and global, and in which investments are made in alternative energies, we’re still at around 16 GT. He said “this is probably not enough” of a reduction in CO2 emissions, which is pretty obvious considering global emissions are only now about 20 GT/year, and most observers think we need to be at less than 20% of today’s emission. The point of the talk, though, was that even with cap and trade, fossil fuels are going to be a big part of future energy demand. Unless we change the economics somehow, so that the demand goes away, the supply is unlikely to go away either. Ted Stevens was not wrong in saying “don’t blame Alaska” because we down in the lower 48 are the ones doing all the driving. All of which is to say, yes, you are probably right that a new “economics of energy” is needed. The question, of course, is how to get there? {Take these emissions numbers with a grain of salt by the way; I’m reporting only what I read off the graph that the Shell guy presented. I may be off a bit (though not substantially, I think)}–eric]

    Comment by Ike Solem — 24 Oct 2008 @ 2:41 PM

  83. > A fully mature tropical forest, however, is in steady-state,
    > oxidizing as much carbon as it stores. That’s the normal state of
    > the biosphere

    Ike, aren’t you describing the tropical forest biosphere?

    As I recall the tropical forest is a thin layer of living material over mineral soil, though, almost all the carbon is in the living trees and plants. Clearcut a tropical forest and you get a mineral area with almost no topsoil.

    Temperate forests and prairies can be fully mature and still be creating topsoil — and can go on creating more topsoil for centuries.

    It would be a shame to start clearcutting mature temperate forests on the false argument that they aren’t continuing to capture carbon, eh?

    Comment by Hank Roberts — 24 Oct 2008 @ 7:53 PM

  84. Just a couple of sources on topsoil recovery, almost at random:

    (not clickable — copy and paste into the browser and take out the space after the // — the parens break the clickable link in this software)

    Comment by Hank Roberts — 24 Oct 2008 @ 8:06 PM

  85. 74,76: I suspect that adding an increment of heating/cooling can have an enhanced effect if it occurs on or near a marginal snow/ice surface, i.e. a disproportionate amount melts snow/ice and via the albedo feedback produces a bigger effect. This is probably what Marcus was getting at with the black-carbon snow effect. There of course could be incremental effects on ocean/atmospheric circulation if a change in radiative balance were locally or regionally concentrated. I can imagine trying to obtain some cooling by deliberately increasing the albedo of human controlled surfaces (pavement, roofs, farmland etc.), such a (negative) forcing would of course be unevenly distributed.

    Comment by Thomas — 24 Oct 2008 @ 10:04 PM

  86. Oil at $67a barrel. That is usefully below the $80+ production cost of many fields, and particularly of already-silly sources like tar sands. So production from those sources is now problematic. This will usefully ease emissions, and expedite the cascade into post-peak oil deficit. Tidy, eh.

    Comment by Nigel Williams — 25 Oct 2008 @ 12:20 AM

  87. Ike, citation on the $15trillion.

    PS what’s that in real money..!

    (I bet the Canadians are happy as larry now that the US can’t use that jibe against the CAD$)

    PS at some point, you WILL have to spend that money anyway.

    Comment by Mark — 25 Oct 2008 @ 4:36 AM

  88. re #82: “the atmospheric CO2 levels did not change until fossil emissions began to rise”.
    Did you read the recent paper by van Hoof et al: A role for atmospheric CO2 in preindustrial climate forcing.
    “Inferred changes in CO2 radiative forcing are of a magnitude similar to variations ascribed to other mechanisms, particularly solar irradiance”
    and volcanic activity, and may therefore call into question the
    concept of the Intergovernmental Panel on Climate Change, which
    assumes an insignificant role of CO2 as a preindustrial climateforcing

    Comment by Francis Massen — 25 Oct 2008 @ 12:43 PM

  89. # 83 Hank (and #82 Ike) One needs to consider not only rates of sequestration by forests but also the size of the carbon pools they maintain in biomass and soils. Sequestration slows after forests mature, but respectable rates can continue for hundreds of years (Luyssaert, S., E. D. Schulze, et al. (2008). “Old-growth forests as global carbon sinks.” Nature 455(7210): 213-215.)

    Given the extensive depletion of old-growth forests in temperate regions, the potential for increased storage is considerable. Even when carbon uptake slows to very low levels in very old forests, they typically maintain very large pools of carbon. Logging will release most of the carbon in biomass to the atmosphere, even accounting for the portion that may end up in long-lived wood products.

    With apologies for the seeming self-promotion, I recently completed a paper on these and other topics relating to climate change and forests. It’s intended for an interested but non-technical audience and has extensive references to the primary scientific literature. It can be downloaded (PDF) at

    Comment by Rick Brown — 25 Oct 2008 @ 12:57 PM

  90. We actually had an economy that used very little fossil fuel, and not that long ago.

    Up until around 1950 (approximately the year they bought their first tractor, were connected to the grid, and installed a propane furnace and stove), members of my family collected firewood from the Trice-Dedman woods. That meant they did not have to burn fossil fuel to heat the farmhouse or to cook their food. They farmed the bottom land with mules. It produced fantastic crops and plenty of fat livestock. Plenty for them, and plenty extra to help feed the people of Kansas City. They were happy as clams:

    Now nobody collects firewood in the Trice-Dedman woods, so I guess the woods have stopped sequestering carbon. Doesn’t have to be that way. It is possible to manage an old-growth forest.

    Comment by JCH — 25 Oct 2008 @ 1:13 PM

  91. You need to keep up. Mark, the Canadian dollar has fallen back down to below US$0.80.

    Comment by Jim Eager — 25 Oct 2008 @ 3:01 PM

  92. Don’t have the link, but the 2007 CE emissions are close to 10 GtC, counting both fossil carbon and deforestration. That’s (44/12)*10 = 36.7 Gt CO2.

    Comment by David B. Benson — 25 Oct 2008 @ 3:11 PM

  93. 82, 83: The argument that we should save forests to slow climate change is a tricky one, and could come back to haunt us in several ways.

    1. Forests affect climate not just by absorbing CO2, but though evapotranspiration (the loss of Costa Rican cloud forests is as much a result of deforestation in the Atlantic lowlands as it is a result of any warming trends) and the degree to which they reflect or absorb heat. There have been a few studies suggesting that although temperate forests do act as carbon sinks, any cooling effect this may have is more than offset by the warming effect produced by their absorption of heat (e.g. Otterman et al 1984 J. Clim. Appl. Meteorology; Betts 2000 Nature). Thus in terms of overall effect on climate, one might reasonably argue that clearcutting temperate forests is the way to go. Not something I’d like to see.

    2. There’s a time-scale disconnect in the concept of compensating for releasing carbon stored in fossil fuels by storing carbon in forests. Trees are a relatively short-term carbon storage site, particularly in light of the predicted increase in wildfires. No matter how well protected a forest is, one good wildfire releases most of the carbon stored in that forest (and the upper layer of topsoil, too).

    To paraphrash Ken Caldeira, it’s a much better argument to stop climate change to save the forests than to save the forests to stop climate change.

    Comment by Jennie — 25 Oct 2008 @ 6:00 PM

  94. Hank Roberts (77) — Thanks for the links! Looking at this graph (on the right)

    from the Steffensen et al. paper, notice that a temperature minimum was established about 74,000 years ago. This is the approximate date for the Mt. Toba super-eruption, which led to 3–6 years of intensely cold weather, estimated to be a sufate induced global cooling of 4–8 K by the volcanologist. (Before becoming too excited about this, there is no hint of it in the Vostok ice core temperature proxy study by Petit et al., data on centennial scales.)

    But it was quite serious for at least Bengal tigers with a almost exterpating population bottleneck; no surprise, the ash in South Asia was meters deep in places. It was also rather serious for humans:

    See bottleneck 2, but ignore the choices of habitation as it now appears that modern humans had probably already left Africa for Yeman and the Persian Gulf by this time, and possibly as far as Southeast Asia.

    In this event we can understand something of the impact of very rapid climate change; not good.

    Comment by David B. Benson — 25 Oct 2008 @ 6:22 PM

  95. 82: For those interested in the corporatization of big environmental groups and their relationship with companies not known for their green behavior, I’d recommend a book called Green, Inc written by a former Conservation International employee. As a scientist who recently worked for one of the three biggest environmental groups, I’d say that at the management level the big environmental groups do not live up to the expectations of their membership or even many of the scientists who work for them. For instance, my organization explicitly prioritized fundraising over science and education on its website. We were not allowed to post anything linking to an external site, because that reduced the likelihood that someone would give to our organization. The recent story ( about a WWF-sponsored 25-day trip with a carbon footprint of 14 tons of CO2 per person (3.6 times as much carbon as the average person emits in an entire year) is not all that surprising to people who’ve worked with the big environmental NGOs. At the upper level, the focus is on raising money and advertising much more than it is on science (and the CEOs are paid like CEOs–the CEO of the Wildlife Conservation Society, for instance, makes over $800,000/year). This is not to denigrate the science that gets done–there are heaps of committed and talented scientists working for WWF, TNC, etc. It’s just to comment that at the upper level, the focus isn’t always on science-based conservation anymore, and greenwashing is a symptom of that. As far as the Nature Conservancy goes, I think that their state-based offices illustrate the importance and effectiveness of being truly local for doing conservation. The state offices are generally better at keeping the focus on real-world conservation than their global programs.

    Comment by Jennie — 25 Oct 2008 @ 6:27 PM

  96. Hank Roberts @ 77 quoted:

    Thanks for including this: when the scenarios that talk of the ability of vegetation communities and plant species to adapt to rapidly rising mean global temperatures are discussed, my observation is that the last sentence in the quote you give is often ignored. Most reports and discussions of the potential impacts of climate change on vegetation communities that I’ve seen (and I’ve not seen either all the models or all the discussion by a long way) talk about the need for species to migrate polewards by Xkm a year. This is tricky enough for wind pollinated and/ or wind-dispersed species (grasses, pines), but much worse for species that rely on some other vector for either pollination or dispersal or both. But if these proposed migration rates are bad enough, the picture gets worse once other factors critical to migration and contineud survival are considered. In natural landscapes, where do these plants migrate to that isn’t already occupied by a range of plant species already in competition for resources (space, light, nutrients, water)? Even if migrants can find a place, in many cases one or more factors will not be suitable (soil type, nutrient status, water availability and, importantly, local climate). And even if these migrants are successful in finding alternative sites, do they not themselves then have the potential to become “weeds”, displacing other local natives that are also struggling in the now modified climatic regime?

    And all the above assumes that between their current location and the new site are unbroken tracts of land able to support these migrating plant species: as anyone with access to Google Earth can verify, the nature of large areas of temperate and tropical land has been radically altered by human activity – agriculture, industry, resource extraction and so on all make it nigh impossible for any but the most mobile and adaptable organisms to live in: what chance that plants can migrate through such landscapes? And in the unlikely event that they can, what chance is there that the various pollinators and dispersers will go with them? What of mycorrhizal fungi that a great number of plant species rely on to obtain soil nutrients – how can these “migrate”? And what of plant species listed as threatened, or rare, or which have restricted climatic or edaphic parameters? In Australia, up to a quarter of thee members of one of most widespread genera (Eucalyptus) are at risk of failing to be able to adapt (see Lesley Hughes’ rather depressing summary here:

    My knowledge of the workings of the planet’s climate is rudimentary at best, and I am a long way from understanding the more technical side of the discussions here, but as a biologist-in-training, even I can see that a 2 or 3 degree shift in global mean temperatures spells trouble for amny plant species, even without the continuing rapid loss of native vegetation across the world. In short, even if we ignore the spectre of climate change, we *need* islands of native vegetation, no matter how apparently small or insignificant: anything the Nature Conservancy Council or its equivalents in other countries can do to ease the pressure on natural landscapes is to be thoroughly applauded, and thank you to RealClimate for bringing this matter into focus.

    Comment by Steve Chamberlain — 26 Oct 2008 @ 4:23 AM

  97. I don’t know why, but the quote from Hank Roberts’ post disappeared (operator error probably). The excerpt I wanted to highlight was:
    ” Our data suggest that climate changes in these systems have been gradual, perhaps averaging less than 1°C per millennium even during the height of the Pleistocene-Holocene transition. Conservatively, if temperatures change only 1°C this century (the minimum International Panel on Climate Change estimate), that rate would be an order of magnitude higher than the fastest rate observed in this record; the projected climate change in the next 100 years will be fundamentally different from any in the last 50,000 years. Given the relatively short geographic distances between elevations and the concomitantly short migration distances required to move among them, Andean plants with broad elevational distributions should be able to remain in equilibrium with climate. For taxa with narrow elevation ranges, however, the predicted rate of climate change may move them completely outside of their climatic niche space within only one or two plant generations. Coupled with habitat destruction preventing colonization from adjacent metacommunities, Andean plant communities may experience greatly increased extinction rates.”

    The link to Hughes’ paper (also disappeared in my post):

    Comment by Steve Chamberlain — 26 Oct 2008 @ 4:27 AM

  98. PHE #66, and eric:

    To claim that the RATE of temperature rise is greater now than in the past, you need evidence. Comparing short wavelength instrumental data to long wavelength (ie. smoothed) proxy data is not satisfactory evidence.

    The point to make here is that what is unique for the past several decades, is the combination of a high rate of temperature rise and its sustainment over these several decades, producing an upturn of about 0.7K.

    Yes there have been faster rates of temperature rise in the past. Heck, there have been in the recent past. Heck squared, there was one early this morning after sunrise ;-)

    The data from proxies indeed does not exclude the possibility of, e.g., a single year, or a short run of years, in the Middle Ages being warmer than 1998. It is the physics that excludes this: global mean temperature just doesn’t behave like this. We know this from the instrumental record — valid evidence for these high-frequency variations (and confirmed by model simulations): the variability power spectrum of global mean temperature anomaly (with forcings removed) is of 1/f type; which solidly rules this out.

    Lower-frequency variations as fast as today would produce an upturn at least as large as today, which would clearly show in the proxies, smoothed as they are.

    Comment by Martin Vermeer — 26 Oct 2008 @ 4:56 AM

  99. [Response: Guys, I’m not claiming expertise on polar bears, which I don’t have. But the comparison with the last interglacial, and the Eemian, is not necessarily at all relevant. In neither of these past times did it get warm as fast as is happening now. Rates matter, usually more than magnitudes. In any event, we may well be heading for warmer-than-Eemian in the long term–eric]

    The above is a false statement see out put from Vostock Ice Cores Robert Carter U tube.


    [Response: No it is not, and Eric is correct. See Otto-Bliesner et al (2006, Science) and compare with projections for 2100. – gavin]

    Comment by stuart harmon — 26 Oct 2008 @ 7:46 AM

  100. One of the problems is the shear economic expense, which if you consider the running of a country to be similar to that of a business makes conservationism and of paramount importance – enviromental issues a luxury, what with the global economic meltdown and all, although the general public is in a position where they are placated by a t-shirt for life and a few extra tubs for recycling, most people (who look out of the window, read the papers or ex-cathode ray nipple) would like to do more, there’s seems to be serious lack of highly effective economically viable solutions.

    I read a few months ago (apologies i should be quoting this appropriately, but i can’t find it) in New Scientist that many conservationist are now looking at species extinction as a collateral damage foregone conclusion.

    Another really interesting post many thanks.

    Comment by schmert — 26 Oct 2008 @ 8:48 AM

  101. Just read the thread. Asteroid Miner’s suggestion(27) that the Nature Conservancy buy coal mines seems brilliantly focused to me. I support the NC now, but would definately dig deeper if I knew my contribution were directly reducing coal extraction. We have to stop mining coal, and it’s politically hard to imagine ceasing in one fell swoop, so reduction, if it happens, will be incremental. Time to start.

    Comment by Rich Creager — 26 Oct 2008 @ 3:39 PM

  102. Hank, #84:

    soil ecology as an essential component of ecosystem management

    Soil recovery from human disturbance in tropical woodlands in Hong Kong

    Comment by llewelly — 26 Oct 2008 @ 11:52 PM

  103. I am Mark J. Fiore, and I posted comment # 3. I read thru all the comments after mine, and was quite impressed with the level of discourse.
    However, Re:Comment # 50, Jason,I am NOT Mark Fiore the San Francisco famous political cartoonist. I get that mistake a lot, with phone calls to me asking if they have reached the cartoonist Mark Fiore. He is an entirely different person than me, and someday I’ll look up and view his work, because lots of people tell me it is great.
    Thanks for all the “feedback” comments on methane.Pun intended. I liked them all.
    Let’s just hope for the best on the massive methane releases, shall we?
    Mark J. Fiore (not the political cartoonist)!!

    Comment by Mark J. Fiore — 27 Oct 2008 @ 12:58 AM

  104. This is a good introduction to the work by cartoonist Fiore:

    Comment by Hank Roberts — 27 Oct 2008 @ 10:00 AM

  105. Re #82, the world allegedly wants/needs 50% more energy come 2030 at the presrnt time but I would imagine that the world could grow their economies by this 50% energy without requiring much more energy if countries like the USA embarked on a large scale energy efficiency drive. However this is unlikely whilst oil remains relatively cheap at around $3-4 a gallon and whilst oil can be imported to the tune of 20 mbpd overall use. It is just too easy to keep that 10 – 20 mpg car.

    Another issue of interest here is patents and spreading the new technology around. Giving China the new technology once the west has developed and deployed it might be seen an anti capatalist due to patent infringement and the costs of development may be inhibitive.

    My personal opinion for what it is worth it that there is at present little incentive to develop and deploy new technologies to reduce overall global carbon output. By the time there is we will be cutting it fine on the timeline.

    Still it is possible that a massive offshore wind expansion coupled with solar thermal a new low resistance grid might do the job to some degree but fossil fuels will always be part of the plan. As an example the worlds 13,000 commercial aircraft would require a land area the size of europe to grow enough crops for biofuel to fuel those planes. We would need a efficiency gain of 8x before it became viable or some other source such as algae maybe.

    Comment by pete best — 27 Oct 2008 @ 10:10 AM

  106. RE: 69 Chuck
    The basis for my prediction is that the Polar bears will adapt. They evolved originally from brown bears to survive in an Artic environment. IF, and it’s a big if, the planet warms enough to completely melt artic ice then polar bears will move to land and compete for food there. The jury is still out on whether AGW is part of a cycle or a flawed prediction using GCM’s to project 30-100 years from now. In case you have not noticed, global temperatures are not warmer than they were 700-1000 years ago and the Polar bears survived that time period fairly well. Global temperatures are not any warmer over the last 10 years and that is something the GCM’s did not predict.

    Comment by Ed — 27 Oct 2008 @ 11:30 AM

  107. Ed (106) — Sigh. I fear you have it quite, quite wrong. First, read “The Discovery of Global Warming” by Spencer Weart:

    Review of above:

    is help you to discover that AGW has already happened and is happening now, a few years of less than maximum global annual temperature notwithstanding. See the five year averages for the HadCRUTv3 global surface temperature product:

    Global temperatures are certainly warmer now than 700–1000 years ago; see the latest paper by Mann et al. Here is a direct observation that in Britich Columbia temperatures are warmer than at any time in the last 7000 years;

    Similar ancedotal data for many parts of the world is easy to find; try for the Alps.

    Comment by David B. Benson — 27 Oct 2008 @ 12:37 PM

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