Al Gore’s movie

Several of my colleagues complained that a more significant error is Gore’s use of the long ice core records of CO2 and temperature (from oxygen isotope measurements) in Antarctic ice cores to illustrate the correlation between the two. The complaint is that the correlation is somewhat misleading, because a number of other climate forcings besides CO2 contribute to the change in Antarctic temperature between glacial and interglacial climate. Simply extrapolating this correlation forward in time puts the temperature in 2100 A.D. somewhere upwards of 10 C warmer than present — rather at the extreme end of the vast majority of projections (as we have discussed here). However, I don’t really agree with my colleagues’ criticism on this point. Gore is careful not to state what the temperature/CO2 scaling is. He is making a qualitative point, which is entirely accurate. The fact is that it would be difficult or impossible to explain past changes in temperature during the ice age cycles without CO2 changes (as we have discussed here). In that sense, the ice core CO2-temperature correlation remains an appropriate demonstration of the influence of CO2 on climate.

For the most part, I think Gore gets the science right, just as he did in Earth in the Balance. The small errors don’t detract from Gore’s main point, which is that we in the United States have the technological and institutional ability to have a significant impact on the future trajectory of climate change. This is not entirely a scientific issue — indeed, Gore repeatedly makes the point that it is a moral issue — but Gore draws heavily on Pacala and Socolow’s recent work to show that the technology is there (see Science 305, p. 968 Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies).

I’ll admit that I have been a bit of a skeptic about our ability to take any substantive action, especially here in the U.S.

Gore’s aim is to change that viewpoint, and the colleagues I saw the movie with all seem to agree that he is successful.

In short: this film is worth seeing. It opens in early June.

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245 comments on this post.
  1. Pharyngula:

    Al Gore is looking awfully good right now. Josh Marshall thinks he has a shot at the presidency; Blog of the Moderate Left has an interesting ranking of potential candidates, and while he puts Gore at #5, but says…

  2. Adam:

    Re: 69 & response etc.

    RPSr has some problems with the article:

    Anyone got any comments (none on that page as of time of posting)?

  3. pat neuman:

    re 102.

    The RPSr rebuttals of the WSJ article by Sharon Begley deal with ocean temperatures and hydrology.

    Based on the NOAA link below there was no need for a rebuttal on ocean temperatures.

    Global surface Ocean temperature plot (1880-2005)

    Based on the 1868-2006 elevation of Devils Lake in northeastern ND, shown at the link below, the discussion by RPSr on drought variablility while not discussing excessive runoff seems like an oversight.

    Click on Devils Lake at:

  4. Roger Pielke Sr:

    Pat- Regarding your comments in #103, the issue is that today (May 15, 2006) there are large regions with negative ocean temperature anomalies, both at the surface and at depth. These regional cool anomalies need an explanation. They also illustrate why we need to move beyond a global average trend (or an ocean-wide average trend) to a regional perspective with respect to human- and natural climate change.

    On your second comment about drought, I am unclear on your point. I just presented two examples in my weblog of historical-and paleo-studies to show that the 20th century was not excepetional in terms of dry periods. What is new is the apparent greater vulnerability of society to weather extremes of all types, as we saw in Katrina, and, with respect to drought, to the 2002 drought in Colorado.

    [Response: Roger, it’s important to state the base-line for the anomalies in the link you point to – it’s 1984 to 1993. Whereas most claims for ocean warming use a much longer time series – for instance with respect to 1951-1980, the anomalies for 2005 were almost uniformly positive.
    The claims made in the Begley piece about the possible role of long term natural variability causing the 20th Century trends in global mean temperature are a statement about the multi-decadal time scales – not a few years of interannual variability. – gavin]

  5. James:

    I posted a comment that was filtered.
    All I said is that the Antarctic Ice sheets are experiencing a net gain, not a loss as poster 97 is stating, and his post was not true. What is wrong with that?

    [Response: Please keep your comments polite. But you are not correct in your assessment – the net mass balance for the whole continent appears slightly negative (according to the preliminary GRACE measurements), but given the uncertainties and shortness of that record, a clear statement either way is not justified. – gavin]

  6. Mark A. York:

    “the 20th century was not excepetional in terms of dry periods.” While I don’t know this for sure, I can say that land alteration has left us more susceptible to disastrous results that magnify this effect. It seems to me increasing the global mean temperature can do nothing if not exacerbate natural variabilities of local climates.

  7. Hank Roberts:

    PhysicsWeb this month has an article on the Antarctic mass balance measurements here, both historical and new, written by Andrew Shepherd (School of Geosciences, University of Edinburgh, co-ordinator of the European Space Agency’s VECTRA SAR interferometry consortium).

    It’s a quick read, a review, with footnotes; it may clarify what we know now.

  8. pat neuman:

    re 104. 103. 2nd point.


    In your rebuttal of the WSJ article by Sharon Begley, of a statement by Michael Oppenheimer (“We have never seen natural variability on a global scale like we’ve had in the last 100 years” says atmospheric physicist Michael Oppenheimer of Princeton University), you gave examples of dry but not wet.

    I brought up Devils Lake as an example of wet, that records show the elevation of Devils Lake, which was a closed basin from 1830- early 2006, is at a level not experienced for at least 177 years.

    Also, I think it’s important to add that her article began with “For laypeople, …” . I think the article is a good one for laypeople to grasp some of the important elements regarding the global warming crisis we’re heading into.

  9. raypierre:

    Regarding Barton Paul Levenson’s comment #90,on what convection does to temperatures:

    I assumed that the article was referring to a surface budget calculation with the surface non-radiative heat fluxes turned off, because that calculation does give you about 350K and my own pure radiative equilibrium calculations suggested to me that the comment regarding the role of convection didn’t make sense if the author had pure radiative equilibrium (i.e. no convection) in mind. However, in looking at the references Barton mentioned, I think I know where the JunkScience author might have picked up some misconceptions about pure radiative equilibrium. The relevant material is at the end of Chapter 9.3 of Goody and Yung — there isn’t anything in Chapter 2 or 4 of Houghton that points to a 360K surface temperature in pure radiative equilibrium.

    Goody and Yung reproduce a figure from a 40 year old paper (Moller and Manabe, 1961) which does have a 350K surface temperature in pure radiative equilibrium. However, that curve includes the radiative effect of clouds, and it is meaningless to hold the cloud forcing fixed if one is eliminating convection, since most of the clouds are due to convection or other moisture transporting motions. Even given that, the cloud results in Moller and Manabe are questionable, since nobody knew the net radiative effects of clouds in 1961. In fact, I’m at a complete loss to account for their result (and couldn’t lay hands on a copy of their paper today to see what they did), given that we know now that clouds have a modest net cooling effect in the midlatitudes, whereas in Moller and Manabe the clouds produce a 50K net warming. That’s about what you’d get if you kept the cloud greenhouse effect, but ignored the cloud albedo effect, but I’m not sure that’s what’s going on.

    Now, sticking with Moller and Manabe, if you ignore the dubious cloud calculation, the pure radiative equilibrium surface temperature in the clear sky case is a more modest 310K. Even that is an unrealistic estimate of what you’d get in the absence of convection, since convection is what redistributes water in the vertical. Without surface fluxes and convection, the atmosphere would be dry. When I run the NCAR radiation model without convection, then in the dry case the equilibrium surface temperature in pure radiative equilibrium with global mean solar radiation (assuming an albedo of .2, to account roughly for removal of clouds) is a chilly 273K. There is a jump in temperature between the ground and the overlying air, whose temperature is 266K. This jump is a familiar phenomenon from grey gas models; when the air is not too optically thick, it arises because the low layer air is heated by absorption of upwelling infrared from the surface, but radiates from both sides — yielding a temperature smaller than the surface temperature by a factor of 1 over the fourth root of 2. The jump is smaller than the thin limit, because there is enough CO2 in the atmosphere to make the layer moderately optically thick. I used 300ppm of CO2.

    Actually, even with water vapor I can’t reproduce a surface temperature quite as warm as Moller and Manabe. To be specific, if I assume the boundary layer relative humidity is 70% and that the free troposphere relative humidity is 50%, then the low layers of the atmosphere cool to where they are not so terribly optically thick. In this case, my equilibrium surface temperature rises to about 284K, and the air temperature at 995mb (relative to surface pressure 1000mb) is 255K. Perhaps the 40 years of improvement in radiative transfer in the NCAR model since Moller and Manabe has resulted in a better estimate of the optical thickness due to water vapor. It’s rather tricky to do the pure radiative equilibrium right, since you need a lot of low level resolution, owing to the optical thickness of warm, moist air; the radiative equilibrium temperature gradient in the lowest few mb of the atmosphere is huge, as noted already by Goody and Yung. When I add more resolution at low levels, I don’t increase the surface temperature significantly, but I do resolve the gradient better, and the temperature jump between the lowest model level and the surface temperature goes down. It’s all rather academic, since the pure radiative equilibrium is irrelevant to anything going on in Earth’s actual atmosphere, except perhaps in the Antarctic night. That’s probably why everybody seems to still use the figure from Moller and Manabe (1961).

    The upshot is that, however you slice it, there is no sound basis for the statement that the surface temperature would be over 350K in the absence of convection. I suppose there is one sense in which you could say that convection “helps” heat escape to space. The upper tropospheric temperature is warmer than it would be in pure radiative equilibrium: there’s a balance between convective heating and infrared cooling there. Since that warming helps to increase the outgoing longwave radiation relative to what it would be in pure radiative equilibrium, it could be said that the convection is helping the heat to escape. I don’t know what it adds to the understanding of the system to put it this way, but there is some grain of truth in it.

    Rather a long and technical diversion, but it was something I needed to sort out anyway, for other reasons. Thanks to Barton for raising the issue.

  10. Mauri Pelto:

    Re #104: Roger you seem to have a tree focus instead of a forest focus on the SST issue. The Hoerling article in EOS last week looked at the SST warmth of 2004, but of course 2005 would have been even more substantially yellow-red hued on the ocean anomaly maps. The same observation cannot be missed for 2005 that they noted for 2004 “Every ocean witnessed warm sea surface conidtions in 2004, with only the middle latitudes of the Southern Ocean epxeriencing below average values”. The actual magnitude of the temperatues anomalies are not large in terms of degrees for the year, thus, any given day as you mention above has plenty of cool spots. I liked a conclusion in the aforementioned paper, ..”the simulations indicate that much of the global mean land warmth is (at least currently) arising from a feedback processes involving air-sea interactions.” If the ocean adjacent to a coastal region has a dominantly positive temperature anomaly, it does not matter if it does everyday, your land temperature will be positively influenced. The regional changes are important as you note, but the temporal changes cannot be looked at too narrowly. The PDO has been dominantly positive since 1977 off the Pacific Northwest coast, but has many variations in its signal, yet the overall impact is three decades now of warmer conditions than otherwise.

  11. lisa brooks:

    I know I promised I would stick to the topics discussed (sorry Hank), but I didn’t know where else to ask…

    Has there been a comprehensive RealClimate discussion related to the current volcanic activity of the Merupi and Bezymianny volcanoes? If I understood correctly, the Bezymianny volcano has generated gas plumes of up to 23,000 ft., and the Merupi volcano is still extremely volatile. Is it known what (if any) climatic impact these eruptions will have? Is it known how much gas and ash is needed before a climate change occurs?

  12. Roger Pielke Sr:

    Gavin- Regarding #104

    “Response: Roger, it’s important to state the base-line for the anomalies in the link you point to – it’s 1984 to 1993. Whereas most claims for ocean warming use a much longer time series – for instance with respect to 1951-1980, the anomalies for 2005 were almost uniformly positive.
    The claims made in the Begley piece about the possible role of long term natural variability causing the 20th Century trends in global mean temperature are a statement about the multi-decadal time scales – not a few years of interannual variability. – gavin]’

    Roger Sr. Reply: The use of sea surface temperature data prior to global satellite coverage is not appropriate. Data periods that are as homogeneous as possible are required. Moreover, with the claims that recent years have been so warm, the assessment of the current SST record should show this as a dominance of warm anomalies even usung the period of 1951-1980 as the baseline. The current SST data does not show this.

    I agree that we also need to examine the surface heat storage changes below the surface, but the heat is not being stored near the surface (as represented by the SST anomaly plots). Thus where are the excess Joules of heat being stored?

    [Response: Roger, I think you’ll find yourself a little out on a limb if you are claiming that no SST data before 1979 are valid. While I would agree that global estimates back to the 19th Century are a little problematic (we’ve found discrepencies in the SST estimated changes after Krakatoa in 1883 for instance), SST estimates certainly from the end of WWII are good over large parts of the ocean. Merging of data from different sources needs to be done carefully of course but I am not aware of any evidence that this has not been done reasonably (see Rayner et al for instance). Indeed, there is substantial high resolution ocean proxy data (from corals, anoxic basins etc.) that confirm exceptional late 20th Century SST. The best estimates of ocean heat content from the 1950’s indicate widespread increases in storage despite the poor coverage in southern oceans, and recent more accurate estimates (Willis et al, 2004; Gille 2002) show very similar trends. There is substantial interannual and interdecadal variability in the ocean and I don’t want to diminsh the importance of that for many aspects of climate, but in the long term records, there is no doubt that the oceans are warming, and this is inconsistent with a big role for natural variability in late 20th Century trends in SAT. – gavin]

  13. daCascadian:

    A little fuel to the fire…

    “Last month was the warmest April on record for the United States, offering many Americans a pleasant spring month.

    For the 48 contiguous states the average temperature was 4.5 degrees Fahrenheit above normal for the month, the National Climatic Data Center reported Tuesday.

    That made it the nation’s warmest April since record keeping began in 1895.

    Worldwide it was also an above-normal month, but not a record breaker, finishing as the seventh warmest April worldwide, according to the Data Center, a branch of the National Oceanic and Atmospheric Administration…”

    “…playin with matches in a pool of gasoline…” – Swamp Mama Johnson

  14. pat neuman:


    In 104 you said you were unclear on the second point I made in 103, on variability. I hope my additional explanation in 108 cleared that up. I also hope that you, and some others, will soon publicly acknowledge that earth is in a global warming crisis due to our use of fossil fuels. I think that would help.

  15. joel Hammer:

    I haven’t seen the film.

    We know that Mr. Gore is not a scientist, and so he is listening to someone. Do you know who he listens to?

    Do you know if any of these guys have Al Gore’s ear?

  16. gringo:

    I haven’t seen the movie but I’ve already seen the attacks on it.

    Someone over there at DailyKos claims this:

    I’ve seen the film and he tells at least two easilly debunkable lies. the first concerns the so-called “Little Ice Age” an anomolous cold period that caused much damage to civilization in the form of famine, desease and other such stuff.

    He denies that it even took place.

    Not that he mentions it by name, of course, he shows a graph of average temperatures from the last eight hundred years (he calls it a thousand) and claims that this is normal for the Holocene, which simply isn’t true. Then he derides “skeptics” who say that the previous centuries were actually WARMER than it is today.

    If you see the film please notice this segment.

    The other easilly debunkable lie is that he uses false information to deny any “anti-global warming” scientific studies exist. They do. I’ve seen some.

    Is it true that Gore denies Little Ice Age in the movie? I would find it fairly strange as Gore was writing about Little Ice Age in his book.

    And does any peer-reviewed scientific study exist today which denies that global warming has been taking place over the last 100 years?

    And which century in the Holocene was warmer than the 20th? And what kind of data supports that conclusion?


    [Response: The LIA stuff will be ref to the “hockey stick” stuff – you’ll find that in our index easily enough. Previous centuries weren’t warmer than today, as far as we can tell. But neither of those two points has much to do with whether people are causing GW today – see our what-if post. That the globe has warmed over the past century is accepted by all but the wacko fringe – William]

  17. gringo:

    joel Hammer wrote:

    Do you know if any of these guys have Al Gore’s ear?

    Which of those people denies anthropogenic climate change?

  18. joel Hammer:

    Which of those people denies anthropogenic climate change?

    I doubt any of them, in public, would.

    There are just some things you can’t say in public. You know what I mean. Without committing professional suicide.

    But, they are all publishing stuff about the affect of variable solar output on Earth climate. That is to say, many of them think their research shows that variations in solar output have had great influence on Earth’s climate, and still does.

    Does Mr. Gore’s movie mention their work?

    If not, how can you say that Mr. Gore’s movie “gets the science right” when he is leaving out a lot of the science?

    [Response: Ah! the climate mafia at work maybe? Look, the problem is that you appear to see solar versus anthropogenic as opposing thoughts. That is just not so. Many of us (myself, Stefan, Mike, Eric at least) have worked on issues related to solar forcing (modelling, historical records of solar forcing, potential impacts of solar in the paleo record) and yet none of us have a problem with the radiative effect of greenhouse gases. I can assure you I’m not being forced to say this! – gavin]

  19. Stephen Berg:

    Re: #118, “‘Which of those people denies anthropogenic climate change?’

    I doubt any of them, in public, would.

    There are just some things you can’t say in public. You know what I mean. Without committing professional suicide.”

    No. There are some things you can’t say in public because it will make you look silly.

  20. raypierre:

    I’ve re-opened this thread, given the renewed interest associated with the wider release of the movie.

  21. Brian Gordon:

    Someday, this movie will come to Victoria, BC, Canada. :-) Until then, may I suggest that Gore is focusing on the moral aspect because this is the key to the problem: Americans see themselves as somehow separate from other people, from the environment, and from the consequences of their actions. (Canadians are not much better.) Until this changes, Americans will continue to exploit other nations, weaker people, the environment.

    What is the root cause of our environmental and social problems? Gore would seem to be saying a lack of morality, or twisted morality. I would agree.

  22. Grant:

    Not just a movie — it’s a book too!

    I just picked up a copy yesterday. I found it a very good read. I plan to pass it along to some skeptics I know. In fact, it might be worthwhile to buy several copies, and distribute them to acquaintances with an appeal to “pass it along” when you’re done.

    *We* can help spread the word.

  23. Steve Sadlov:

    RE: #88. Consider the impact of the massive diversions of Asian rivers by the USSR. These used to flow into the Artic undammed. But now, they water the Central Asian deserts to grow cotton and food crops. The Arctic, as a semi enclosed, somewhat shallow ocean, is a key place to consider the impacts of human induced changes in salinity.

  24. Steve Sadlov:

    RE: #92. Indeed, endothermic phase changes will be what they must be. Nothing is free, not even phase changes. Input and time required.

  25. Tom Fiddaman:

    The WSJ published an editorial on the movie, which trots out the usual claptrap (CO2 saves us from impending ice age) as well as a new 4th level of skepticism: “we’re all dead in the long run”:

    Warmed Over
    May 31, 2006; Page A13

    …a valid service is performed in satisfying the eternal human appetite for gloom and doom (and no virgins were sacrificed), distracting people from the reality of life, which is that we all are doomed, while the universe, the earth and all that environmentalists hold dear will go remorselessly on and on without us.

    In a million years, the time it takes the earth to sneeze, the planet will likely be shorn of any conspicuous sign we were ever here, let alone careless with our CO2, dioxins, etc. Talk about an inconvenient truth.

    How much more securing, in a way, to believe we are ruining the planet than the planet just does not care about us, and will run rampant with life long after we are dust. And how pleasant to be able to transmute our fury over our fate into incoherent feelings of self-heroism against our present “enemies.” …

    [Response: The WSJ isn’t even right that our impact on the planet will be erased after a million years. The climate might have returned to normal (or maybe not, if we manage to mess up the weathering cycle somehow), but regardless of that, evolution generates species very slowly. The biodiversity we eliminate now, whether through climate change or other means, will take many millions of years to replace, and there is no doubt that it will take a different course than it would have. Disasters are not necessarily a bad thing for the planet (look at the role of the asteroid impact at the KT boundary in helping to give mammals a shot at the future; some people think that the Snowball Earth catastrophe played some role in the evolution of multicellular life and the Cambrian explosion of biodiversity). They usually are a rather bad thing for current inhabitants. –raypierre]

  26. Roger Powelson:

    This is slightly off topic; but in this article, Eric writes:

    “Another complaint is the juxtaposition of an image relating to CO2 emissions and an image illustrating invasive plant species. This is misleading; the problem of invasive species is predominantly due to land use change and importation, not to “global warming”.”

    Importation and land use change may have been the leading cause of here’s more, but to me that’s a very striking example of how global warming is already effecting massive growth and die-off of different specieinvasive species in the past; but that is not to say that global warming won’t take first place in the very near future. Just to quote on example of a huge problem caused by global warming in Canada, I’d like to quote from a article recently published in the Washington Post:

    ” Millions of acres of Canada’s lush green forests are turning red in spasms of death. A voracious beetle, whose population has exploded with the warming climate, is killing more trees than wildfires or logging.

    The mountain pine beetle has infested an area three times the size of Maryland, devastating swaths of lodgepole pines and reshaping the future of the forest and the communities in it.”
    (Rapid Warming’ Spreads Havoc in Canada’s Forests: Tiny Beetles Destroying Pines By Doug Struck
    Washington Post Foreign Service Wednesday, March 1, 2006)

    The article goes on to explain that the killing cold temperatures that used to control the beetle no longer exist, and that the problem has been growing for twenty years.

    One could argue that the pine beetle doesn’t really count as an invasive species, since it was there before global warming..but I think you’d be splitting hairs if you did.

    Othere examples spring to mind: West Nile Virus, malaria, and cholera are other organisms that are already expanding their geographical spread.

    Other than that, I think this is a great site!

  27. munge:

    Speaking of inconvenient truths…

    “The National Hurricane Center released a summary report on Katrina this week that downgraded the storm’s intensity at landfall in Louisiana on Aug. 29 from Category 4 to Category 3. The winds in New Orleans, which lay to the west of the storm’s center, were probably even weaker than that, at Category 1 or 2 speeds, the report said.” — Joby Warrick and Peter Whoriskey, Washington Post, Dec. 22, 2005

    [Response: Could you clarify what you mean by this statement, and what’s supposed to be “inconvenient” about it? However Katrina is classified, you have to admit that no previous hurricane that hit New Orleans did what Katrina did. If I had to hazard a guess, what’s really inconvenient about this truth is that the Corps of Engineers (by their own admission) was not providing protection at the level they claimed; a good thing that a real Cat 5 hurricane hasn’t hit. By the way, the difficulty of predicting the enormous damage done by Katrina and the particular failure mode that led to the damage, makes me very skeptical indeed of the estimates of AGW contribution to hurricane damage in Pielke’s and Landsea’s attempts. –raypierre]

  28. munge:

    Ray — Your last sentence ably answers your first question. The “inconvenient truth” is that the producers should have chosen anything but tying Katrina so intimately visually into GW (poster, website, interview background, etc.). Gore has a history of hyperbole (much of it of little import), and using Katrina as a GW ‘prop’ was foolish; particularly when juxtaposed, as Eric pointed out, against the context of what he actually says in the movie.

    Why is this important? Because it acts to the contrary of so many earnest posts above, who want the ‘right’ people to see this movie. An average moviegoer makes decisions based on first impressions; and given the recent spate of polls which reaffirmed Americans Still Not Highly Concerned About Global Warming, it is a given that the average 25-50 moviegoer who can’t get into a sold-out “M:I:III” will take one glance at that Katrina poster and tune completely out, based on the prevailing CW about Gore — rightly or wrongly so.

    Could more have been done to overcome the ‘hard sell’ nature of any documentary in the US? Maybe not. Will it play entirely to the choir while in the theaters, without the hope of the crossover appeal of F911? Probably. One hopes that Gore does not eventually tape-loop it on CurrentTV but rather rapidly offers it to mainstream cable where I believe it has a better chance of being viewed by the ‘right’ people.

    As for “However Katrina is classified, you have to admit that no previous hurricane that hit New Orleans did what Katrina did.”, quite the contrary. Betsy also hit NO as a strong Cat 3 on Sept. 9, 1965, pushing Lake Ponchartrain into NO, submerging the 9th Ward and other parts of the city. The River Gulf outlet & Industrial Canal levees were also topped.

    However, your last two statements are irrefutable.

  29. Tom Fiddaman:

    In a follow-on WSJ article yesterday (Al Gore, Envirotechnologist), Gore replies to the May 31 Holman Jenkins editorial:

    Mr. Gore had little tolerance for an editorial in The Wall Street Journal that took the position that there’s no certainty that carbon emissions are causing global warming. “Gravity may repel us from the earth’s surface. It’s an open question,” he says with dripping sarcasm. It’s only propagandists – “immoral and unethical,” he calls them ” that fight the reality of global warming.”

  30. S Molnar:

    I tend to agree that Katrina as advertising for the film is more Hollywood than science, but the fact that Katrina happened to weaken just before landfall is both well-known and irrelevant. It was a huge category 5 hurricane just before landfall (with a category 5 storm surge when it hit) in a season of many and huge hurricanes. A visual of shrinking glaciers or late-arriving monsoons or healthy mountain pine beetles might appeal to the choir, but I suspect hurricanes are more likely to pull in the masses. However, I like the claim about people not bothering to see the film because it’s sold out – it reminds me of Yogi Berra’s line about a popular restaurant: “Nobody goes there anymore, it’s too crowded”.

    [Response: On the poster the hurricane graphic coming out of the smokestack does have the form of a question mark, albeit reversed; that does imply that we’re talking about risks not certainty to some extent. The poster I like best though is the one that’s up in the local cafe where I live: A line of penguins trying to march over desert sand dunes. It does make one think about what’s going to happen to the Emperors once southern hemisphere warming catches up to the radiative forcing. –raypierre]

  31. S Molnar:

    Whoops, I just realized that munge’s “M:I:III” reference is to a Hollywood movie, and not to a multiplex numbering scheme; my apologies for the misunderstanding. I guess that casts some doubt on my qualifications as an expert on popular culture (although I gather the Gore movie is pretty much selling out so far).

  32. Michael Tobis:

    Just saw An Inconvenient Truth on opening night in Chicago. I wasn’t alone, but it was a small room (one of four in the city) and far from sold out.

    My main complaint was that the word “nuclear” was never utterred during the movie. Whether or not it provides the way out of our quandary, it certainly is an option worth considering. Failure to mention it leaves me seeing Mr. Gore (for whom I nevertheless have great admiration in many ways) as still not entirely
    forthright, still somewhat in the grips of short-run political calculation.

    The best part of the movie for me was the “earth in the balance” cartoon, which he handled with panache. (I guess he’s had a lot of practice with that one, as it insired the title of his previous book.) It is a fine example of the delusional way of looking at the world that is all too common among commercial and economic circles, and Gore does a fine job with it.

    Something of a missed opportunity, I think, was the Haitian-Dominican border image. Its lesson might have been missed by some because that astonishing image went by too quickly.

  33. Damien:

    Hello. I am a non-scientist who has been following the Global Warming/Climate Change debate for about 8 years. One thing that occurs to me is that with or without humans, the Earth’s climate has always changed and will always change. It seems that much of Gore’s presentation is geared towards human impact on those natural cycles. Whether or not we are making the climate warmer, I don’t think it is a valid policy to effectively say “Stop!”. It is not enough to say that we will reduce human impact and just let whatever happens “naturally” happen. A policy should have more of the form that a certain global temperature is desirable, and we should act to reach that temperature. Whether or not it is CO2 or other factors, our policy should be to reach or maintain a certain temperature.

    If the climate were “too cold”, Global Warming would be a good thing. So, what is the climate right now: Too cold, too warm, or just right? Without an opinion on where we are and where we want to be, I don’t see how one can criticize or be ambivalent about change. Al Gore seems to want us to take action, but that action shouldn’t just be to reduce or eliminate human impact on the climate – it should be to reach or maintain the “correct” climate.

    That’s my non-scientific view, and I would love for someone to explain what I am missing about this controversy.

    [Response: The simple answer to your question is that the climate we had up until around 1900 was the climate we had for the past 10,000 years during which agricultural civilization arose. The climate we had in the past 2 million years, with its glacial-interglacial cycles is the climate that our species and most of the species we rely on now, and many of the species we now share the Earth with evolved. A doubled CO2 climate goes through the roof of anything experienced during that time. You want to gamble with that being a good climate for us and the agricultural and natural ecosystems we share the Earth with? –raypierre]

  34. Hank Roberts:

    I’m just another reader here. To answer that, it’d help to have an idea where you starting from, Damien Do you have any sources of information you are relying on now? (if so, will you tell us what they are?)
    Have you had a physics or general science class or need background in that?

    Basic info — look at the right hand column of the home page here and click those links.

    After that, this is worth reading through and will answer many questions:
    Discovery of Global Warming (Weart)
    The history of scientific research on climate change from the 19th century to the present, told in a set of hyperlinked essays.

    Also, what is your time horizon for wanting to know? How far in the future do you want to think about?

  35. Grant:

    Re: #133

    Damien, it’s not that a different climate is a threat, it’s that climate *change* is dangerous. The more rapid the change, the more danger.

    For example, if sea level had always (for the last several thousand years at least) been 20 feet higher, that would be no problem for people living in south Florida or Bangladesh. People wouldn’t be living there! But if sea level *rises* 20 feet, much of south Florida and Bangladesh will be underwater. With millions living in the greater Miami area, and tens of millions in Bangladesh, that’s a recipe for human misery. Another example: if the glaciers in the Himalayan mountains disappear, there’ll be no more flow into the major rivers supplying fresh water to Asia. If there had never been glaciers in the Himalayan plateau, that wouldn’t be a problem for asians; they’d have adapted long ago. But if the glaciers disappear in a matter of decades, billions of human beings will be threatened with the loss of their primary water supply.

    There’s nothing “magical” about a particular global average temperature. But there is astounding danger in rapid global temperature change.

  36. Coby:

    Hi Damien,

    Try reading this:

    And come back with follow up questions.

  37. Rob Cole:

    I just saw the movie and like the reviewer here on RealClimate I take a generally positive view of the film. Note: I’m a lay person with no specialized scientific training but am someone who has tried to understand global warming from both the consensus and skeptic views (and in the end sided with the consensus).

    One question about some of the facts in the film: towards the end, Gore points out that we already have the technology to reduce CO2 levels, and points out that all the technologies added up together will lower the CO2 levels below current levels. Is the information Gore uses here taking into consideration that just because technology A might reduce CO2 X% and technology B might reduce CO2 Y% that the two technologies used together might not reduce CO2 X+Y%? Or is it true that you can add them all up like that and their cummulative impact is a simple sum of their individual impacts? I would think that some CO2 is easier to reduce than others, and that after a while each successive technology will not have the same marginal impact that it would have if it was the only one used.

  38. Glen Raphael:

    I just saw the movie. Speaking as a skeptic, I thought it did little to counter Gore’s “patronizing and insincere” reputation mentioned in #61 and others. The arguments and presentation favored rhetorical force over strict truth or defensibility, so if I were already inclined to trust Gore’s judgment, I’d likely find the film powerful. As it was, I kept noticing selective presentation of data designed to imply a stronger case than was actually present. Plus the occasional big whopper.

    Take the story that a frog in slowly-heated water won’t jump out until it dies or is rescued. This is a great metaphor for Gore and he uses it well with cute computer graphics and a twist ending, but it’s an urban legend. Gore doesn’t say “there is a story that…” but presents it as a solid fact that frogs act this way, leaving the audience a little dumber than before – a little more certain of a false fact.

    Take the claim that US gas mileage standards are pathetic by comparison to China’s. Al Gore makes fun of our automakers for claiming they can’t meet tougher standards if even China can do better. Left out is the fact that China’s cars don’t yet meet their own announced standards and that their cars really aren’t of comparable quality to ours.

    Take the claim – both direct and implied – that Katrina in particular is evidence of global warming and a portent of things to come.

    At one point the film shows a chunk of ice falling off the outside edge of a glacier into the water while the voice-over says that people who come to see glaciers witness this. Strongly implied: crumbling isn’t normal behavior for a glacier’s edge that meets the water (and there aren’t any places one might witness glaciers growing).

    And so on. Gore is wearing a filter that only admits bad news. Warming is undoubtedly good for many species, including a few endangered animals, but he manages to dwell on the negative – “invasive species”, mosquitoes, and diseases will do better too! When he brought up the example of baby birds that eat caterpillars but now the caterpillars are born earlier due to warming so the birds have less food, my thought was: “Hey, this must be GOOD for the caterpillars, right? And for some other predator that is getting the caterpillars that before would have been eaten by birds?” Why, exactly, am I supposed to sympathize with this bird more than the caterpillar or whatever else eats it?

    At the end of the movie they direct viewers to the site “”. There’s a page on “The Science” here but it’s pretty sketchy. Looks like we’ll need to look at the book to see where Gore’s numbers and charts come from.

    [Response: The ‘frog in boiling water story’ is a metaphor not a fact, and metaphors can only be appropriate or not – in this case it is regardless of what would actually happen if (unethically) tried to boil frogs yourself. Katrina was specifically not given as evidence of global warming. Glaciers do of course calve at the edge regardless of whether the mass balance is postive or negative, but the overall point that mountain glaciers almost everywhere are melting (Norway is a regional exception) is absolutely true. And finally the point of the caterpillar/bird story is that ecosystem patterns that have existed for a long time are being disrupted – and given the complexity of ecosystems – and with consequences that are very hard to predict. -gavin]

    [Response: It’s funny (maybe tragic) how often I see comments prefaced by things like “speaking as a skeptic,” or “being a skeptic, … ” and the like, as if it were a club one were enrolled in or a religion one subscribed to. To me, those words are beginning to take on the tinge “Speaking as someone whose opinions are set in stone, who will filter all new information through my own preconceptions, and who is unlikely to let any new information change my mind …” It’s a strange evolution of the meaningof the word “skeptic” (but see Gavin’s post How to be a Real Sceptic). Still, it’s interesting to see how somebody with this mindset reacts to Gore’s movie, so thank you for sharing your reaction with us. By the way, I agree with you that warming is good for some species. Tree-eating pine bark beetles and oporinia larvae, potato blight, and insect vectors for malaria and West Nile are a few that come to mind. –raypierre]

  39. CM:

    I was wondering if you could respond to the “global warming skeptic” Robert Balling’s recent article “Inconvenient Truths Indeed,” in which he outlines six scientific criticisms of Gore’s movie

    This article has been trumpeted by lay pundits and certain segments of the political blogosphere as a “full debunk of the misleading scientific arguments.” Even a cursory glance reveals that it is anything but a “full debunk,” but it would be useful to know, point by point, what is the scientific consensus on the issues Balling raises.


  40. Hank Roberts:

    Good catch.

    The experimenter “heated gradually at about 2 degrees Fahrenheit per minute” and the frog had the opportunity to jump out” — and it did.

    Doesn’t of course prove the folk tale couldn’t have happened. I don’t doubt it did sometime. I think the folk tale probably refers to a pot heated more slowly, and most likely a pot with sides too steep to jump out of.

    Outdoor laundry tubs for boiling large amounts of water — for laundry — over wood fires, for example, were used for millenia. I’ve seen that sort of tank left open with water and catch frogs.

    People’s containers of all sorts sometimes catch frogs when left with water in them overnight. Not all of them get noticed.

    Casual bykill happens in all sorts of human interactions.

    There’s also the folk tale about the fortunate frog that fell into a churn left full of milk in the barn — who doesn’t drown because in splashing around trying to jump out of the tall container he churns butter, which floats, and she sits on the lump of butter til the milkmaid comes in and throws her out.

    We should be so lucky, I guess.

    Later lecturers may make an example of Homo “sapiens”:
    staying on its planet, while heating it past survivability:
    — as experimenter, they could have reduced the rate of heating;
    — as frog they could have thrashed in useful ways, long enough that they could make themselves able to jump out.

    It’ll be more about lack of science than lack of sensation. Same basic point, you can’t notice everything.

    There are other better examples. I recall reading a few years ago about Central American civilizations that disappeared after having severely degraded their environments, but at maybe 3 percent per year, far too little for a nonscientific culture to remark on. Old irrigation systems showed up from satellites, that they’d used to eventually salt their own fields, I think it may have been.

    [Response:Camping near Iso Molossj√§nkka once, I accidentally scooped up a small frog in my Trangia coffee pot, along with water for coffee. I didn’t notice this and stuck the lid back on and set the kettle down on a rock near my stove. Big surprise when the kettle lid starts banging wildly. Spontaneous boiling? Kettle haunted by ancient Sami spectres? No, just poor froggy trying to get out, before the water is even warming up.

    What do I conclude from all this? That some frogs have more sense than most politicians. –raypierre]

  41. S Molnar:

    I think it’s safe to say that the New York Post has settled the debate:

  42. luke:

    just gotta throw this out there: warmer surface temps do increase the severity of a hurricane. Mr. bush has done his best to block the prevention of global warming. he is directly responsible for some tiny fraction of a degree of warming, and therefore: Mr. bush helped make katrina a (slightly) stronger storm. its logically follows.

  43. Don Baccus:

    Re: #139

    OK, here’s the first “inconvenient truth” trumpeted by Dr. Robert Balling, Jr.:

    “Near the beginning of the film, Gore pays respects to his Harvard mentor and inspiration, Dr. Roger Revelle. Gore praises Revelle for his discovery that atmospheric CO2 levels were rising and could potentially contribute to higher temperatures at a global scale. There is no mention of Revelle’s article published in the early 1990s concluding that the science is “too uncertain to justify drastic action.”

    So a paper published by Revelle (who died FIFTEEN YEARS AGO), in which he says the science is too uncertain to justify drastic action is relevant today … how, exactly?

    Apparently Balling thinks that sixteen additional years worth of extensive research by researchers around the world can safely be ignored because of a paper written by someone who died in 1991.

    I don’t think there’s much reason for me to read Balling’s five additional “inconvenient truths”.

    [Response: On top of that, I wouldn’t immediately assume that Balling is even quoting Revelle correctly. Just remember Pat Michael’s systematic fabrications on what Hansen said in congressional testimony. The article Balling cites is (S.F. Singer, C. Starr, and R. Revelle, “What to do about Greenhouse Warming: Look Before You Leap. Cosmos 1 (1993) 28-33.). Revelle is the last author and signed on to this at a rather advanced age; one doesn’t know what part of the article he actually supported. For that matter, what is the journal “Cosmos?” I haven’t been able to locate it or find a copy of the article to see what it actually said. Has anybody tracked it down? –raypierre]

  44. Hank Roberts:

    Luke, “gotta throw this out there” — got a reference? It’s always helpful to know why people believe what they believe, which sources you rely on. Then we can talk about science instead of opinion.

  45. CM:


    Thanks for your response. I completely agree with your statement about Balling’s first criticism. I easily reached the same conclusion regarding this first point. Unfortunately, the fact that his first criticism is incredibly inane does not a priori disqualify the remaining five, which because they deal with technical aspects of climate research, are much harder to address.

    I was hoping with a scientific background in climatology could give refutations (or confirmations, if they exist) to Balling’s “scientific” criticisms. (see Post #139).

  46. Glen Raphael:

    On “speaking as a skeptic”: Gore preaches within the church of environmentalism. If you don’t happen to subscribe to the tenets of that faith it’s much harder to take his fire and brimstone prophecies seriously. He has more work to do. He has to either convince you to convert or convince you that you should agree with his conclusions based on the few axioms you share in common with the churchgoers. Skepticism with regard to environmentalism is much like skepticism with regard to catholicism – it’s based on the rejection of one or more underlying religious principles.

    This doesn’t mean skeptics can’t be convinced, merely that the arguments to do so have to rely on areas of commonality rather than areas of dispute.

    I thought the movie was suprisingly well done given the constraints of the medium and the messenger, but still in places had a “preaching to the choir” feel. As with the book _Earth in the Balance_, I believe Gore honestly believes what he is saying and is making an effort to speak my language as well as that of his own faith, but he’s not very good at it. He’s better at tending to his own flock than reaching us heathens.

    As for species being helped by global warming, how about endangered green sea turtles?

    [Response: The arguments Gore uses are almost without exception scientifically respectable arguments that would be recognized as such by virtually any scientist working in the field. I really don’t understand what you could be complaining about, or what it would take to convince you, if you’re not willing to accept those kinds of arguments. Are you saying that there was something in the nature of the messenger that prevented you from listening to them? It would be valuable to know whether there’s some different way that the same material could have been presented that would get through to people like you, without compromising the basic science. Of course, Gore has to present the material in a vivid and stark way: this is after all a movie that has to engage the attention of the moviegoer. As for your turtles, I’m sure that with all the species out there one can find a few cases where warmer conditions can help. However, it’s a stretch to think that’s going to happen in many cases. Arctic and Antarctic and alpine species have no cooler climate zones to migrate to. The Tropics is a hotbed of biodiversity, and tropical species can’t just migrate to the temperature zones as the tropics warms — even if there were space for them there. A hotter temperate zone is not like the tropics, because the temperate zones have a strong seasonal cycle and a very different precipitation distribution. Evolution works slowly, and you’re hitting an ecosystem that has evolved over the past ten million years to be adapted to the present kind of climate with having to adapt in a century to a wildly different one. Even for your turtles, I don’t think the ABC news report is the last word: you’ve got to wonder what is going to happen to fungal diseases, ocean productivity, distribution of nutrients, etc. as the ocean acidifies, the wind patterns shift, and the major deep water formation zones change. –raypierre]

  47. raypierre:

    Here are two other Balling things that can be easily disposed of:

    Balling says:
    “(2) Gore discusses glacial and snowpack retreats atop Mt. Kilimanjaro, implying that human induced global warming is to blame. But Gore fails to mention that the snows of Kilimanjaro have been retreating for more than 100 years, largely due to declining atmospheric moisture, not global warming. Gore does not acknowledge the two major articles on the subject published in 2004 in the International Journal of Climatology and the Journal of Geophysical Research showing that modern glacier retreat on Kilimanjaro was initiated by a reduction in precipitation at the end of the nineteenth century and not by local or global warming.”
    Response: The IJC paper is widely misinterpreted, and the precipitation claim is based on an incomplete reading of the record of past climates. There is considerable evidence (e.g, from Lonnie Thompson’s work) that Kilimanjaro melting really is due to warming, and even if you don’t buy that it’s undeniable that tropical mountain glaciers worldwide are in retreat — that’s incompatible with a precipitation interpretation, and even if Kilimanjaro has contributions from precip, some of those may be associated with tropical circulation shifts associated with global warming. See my post “Tropical Glacier Retreat” (linked in the sidebar).

    Balling says:
    “(3) Many of Gore’s conclusions are based on the “Hockey Stick” that shows near constant global temperatures for 1,000 years with a sharp increase in temperature from 1900 onward. The record Gore chooses in the film completely wipes out the Medieval Warm Period of 1,000 years ago and Little Ice Age that started 500 years ago and ended just over 100 years ago. There is evidence from throughout the world that these climate episodes existed, but on Gore’s Hockey Stick, they become nothing more than insignificant fluctuations (Gore even jokes at one point about the Medieval Warm period).”

    Actually, very few of Gore’s conclusions rely on the hockey stick; in any event, as discussed on RC in a half dozen posts or more, the Hockey Stick conclusions have been reproduced by other research groups, and the criticisms of Mann’s original work have not proved scientifically valid.

    Balling isn’t even trying hard. He’s recycling last year’s fish. As the Russians say, “There is no fish of the second freshness.”

    That leaves only Balling’s “inconvenient truth” about Katrina. I’ll leave that one for somebody else.

  48. Hank Roberts:

    Glen, you said:
    “… the arguments to do so have to rely on areas of commonality rather than areas of dispute.”

    As Ray says, none of the science is in dispute. What did you find a problem?

  49. Steve Latham:

    Regarding Endangered Sea Turtles (#146): Glen, I just read the article quickly but even ignoring caveats that Ray mentions, I am far from convinced that this is a good news story. What in that article suggests good news? A green sea turtle laid her eggs further north than they usually do, so people collected the eggs to protect them and are considering releasing the offspring in Florida because they’re worried that Virginia is an inappropriate place for them. Seems like this is more likely a bad news story. In addition, does the fact that a green sea turtle laid eggs further north indicate that the historical sites are becoming inappropriate? More time/work/data would be required to conclude that this is a real range expansion with a positive consequence like increased population size.

  50. Hank Roberts:

    Just saw the movie. Wish it could be recut as the science changes (he said Arctic sea ice gone in 30-50 years, I think; now we have the recent Navy study saying ten years and it’ll be gone in the summertime.

    If any of the moviemakers are reading, I found the times Mr. Gore was a small figure standing in front of a huge screen far more interesting and human-scale than the frequent presentation of closeups of his full face filling the whole screen with a bit of blurred moving scenery outside. I realize those were interview shots. Just personal reaction, he seems more human when he’s not Mt. Rushmore sized.

    I’m glad he makes it clear he as VP was the one who got the Arctic sea ice info declassified from the Naval submarine records (what the Navy grad school thesis mentioned elsewhere here calls the ‘Gore Box’ area on the map; someone in the Navy declassification program wanted him to have the blame or credit for revealing that info back then, I guess. Credit, in hindsight.