Swindles in the “The Great Global Warming Swindle”

The author of today’s post, Lisa Moore, is a scientist in the Climate and Air Program.

In March of this year, British TV Channel 4 aired a 72-minute diatribe called "The Great Global Warming Swindle". The program is filled with old data, data taken out of context, data misattributed, and general misinformation, and at the time it aired we thought it not worth responding to.

But people keep mentioning it, so here are the program’s main arguments and why they’re wrong. Now the next time someone brings this up, you’ll have the facts to give them.

Swindle: Ice core data shows that higher CO2 concentrations follow, rather than precede, temperature increases, therefore higher CO2 concentrations don’t cause higher temperatures.

The Truth: The ice core observation is correct, but it doesn’t mean higher CO2 concentrations don’t cause higher temperatures. It just means that other things can cause warming, too.

Human impact on climate change has been statistically discernable for only the last 50 years. Prior to that, change was initiated by natural factors such as variations in solar energy output. But this warming then caused the release of CO2 into the atmosphere, leading to more global warming. What the ice core data actually show is an amplification effect. Warming (however triggered) leads to the release of CO2, which causes more warming. (For more, see Bill’s previous post on "Causes of Past Climate Change".)

Swindle: Sun spots show a near-perfect correlation with temperature over the last 400 years – the more sun spots the higher the temperature. This is because sun spots cause solar wind, solar wind prevents cosmic rays from reaching the earth, fewer cosmic rays mean fewer clouds, and fewer clouds mean more heat. This accounts for all climate change.

The Truth: Sun spots are a proxy for solar energy output, which is also influenced by solar flares and other phenomena. Solar energy output does affect global temperature, and it made a clear contribution to global warming until 50 years ago. But the temperature spike in the last 50 years cannot be explained by a change in solar energy output.

As you can see in the graph below, solar output has not been trending upward since 1978.

Source: Foukal et al. 2006. Variations in solar luminosity and their effect on the Earth’s climate. Nature 443: 161-166.

Neither have cosmic rays, but temperature is spiking.

Sources: temperature data, cosmic ray counts.

Swindle: From 1900 to 1940, temperatures rose though CO2 from industry was low. From 1940 to 1975, temperatures fell though CO2 from industry was high. Therefore CO2 does not drive temperature.

The Truth: CO2 concentration is not the only factor influencing global temperature change, but that doesn’t mean it’s not a factor. Rising CO2 concentrations from human activity have been detectably driving up global temperature for just the last 50 years. From 1900 to 1940, increased solar energy output accounted for higher temperatures. Temperatures fell from 1940 to 1975 because air pollution was dimming the sun. After the Clean Air Act was passed in 1970, warming resumed.

Swindle: Water vapor is the most abundant greenhouse gas, and the effect of CO2 is insignificant by comparison.

The Truth: Yes, water vapor is the most abundant greenhouse gas, but that doesn’t mean that the effect of CO2 isn’t critical. When temperatures increase due to higher CO2 concentrations, the atmosphere becomes more humid, thus amplifying the global warming effect. (For more, see Bill’s previous post on "The Water Vapor Fallacy".)

Swindle: If greenhouse gases cause global warming, models say that the troposphere (lower atmosphere) should be warmer than the earth’s surface, but it isn’t.

The Truth: The troposphere is, in fact, warmer than the surface. A U.S. government commissioned study, released in 2006, showed there were errors in earlier measurements. (Amusingly, one of the study’s authors is John Christy, a scientist who is heavily quoted in the TV show.)

Swindle: CO2 concentrations in the past have been 3 to 10 times higher than what they are today, but this is not reflected in the "temperature reconstruction". Therefore CO2 does not cause global warming.

The Truth: CO2 concentrations are higher today than they’ve been in the last 650,000 years. And as noted elsewhere in the TV program, CO2 concentration is strongly associated with global temperature.

Swindle: Global warming will lead to prosperity, not catastrophe. This is demonstrated by the Medieval Warm Period, which was a very prosperous time.

The Truth: The so-called Medieval Warm Period was (1) not as warm as today, and (2) a local rather than global phenomenon. For more, see Bill’s previous post on the Medieval Warm Period.

Swindle: Storms and hurricanes are caused by the difference in temperature between the tropics and the poles, and with global warming this difference is less. Therefore global warming does not cause more intense storms and hurricanes.

The Truth: It’s true that the temperature difference between the tropics and poles is less with global warming, but it’s not true that this differential is what drives storm intensity. The factor that best predicts storm intensity is sea surface temperature – the warmer the seas, the stronger the storms. And there is no doubt that global warming is causing a rise in sea surface temperatures.

This entry was posted in News. Bookmark the permalink. Both comments and trackbacks are currently closed.


  1. vk279
    Posted July 12, 2007 at 12:23 am | Permalink

    I think you’ve misrepresented the arguments somewhat – for instance, they don’t make claims such as ‘higher CO2 concentrations don’t cause higher temperatures’ and ‘CO2 does not drive temperature’, they claim that CO2 is not the primary driver of temperature.

    I have a problem with the idea that the ice core data shows an amplification or positive feedback effect due to CO2.
    I understand that as a GHG CO2 will contribute to temperatures at least a little in this way but I know of no reason why the vast majority of the warming and CO2 release cannot be caused by the same thing that triggered it.
    Also, what is the explanation for the periods in which temperature decreases while CO2 is still increasing?

    I also have a problem with what you’ve said about sunspots.
    My understanding is that sunspots correspond to the solar magnetic field strength rather than solar energy output and it is the magnetic field that affects the solar wind and cosmic rays. The sun’s level of magnetic activity has been increasing over the past 100 years – this results in fewer clouds and an increasingly greater amount of the (approximately constant) solar energy output reaching Earth’s surface.

    The cosmic ray count data shows a slight decrease in counts over time. This is what is expected for a solar magnetic contribution to global warming.

  2. Posted July 12, 2007 at 2:14 pm | Permalink

    Hi vk279. Thanks for your comments.

    Re the amplification effect… The issue is that the orbital change – and resulting variation in solar energy output – is not enough to account for the large temperature fluctuations. The amount of warming this can produce is easily calculated – there’s no dispute about this. Something else has to be going on. It turns out that this “something” is an amplification effect from the release of CO2 from the initial warming. The TV show itself talked about how warming leads to the release of CO2 from the oceans and other sources. That’s not in dispute, either.

    Re your second point… Sunspots are one of the main causes of the variability we see in solar irradiance (energy), which has increased slightly since 1750, but not nearly enough to explain today’s rapid global warming. As shown above, irradiance has been flat over the past three decades. But let’s say that sun spots are related to warming through their magnetic field strength. For the “Swindle” theory to be correct, you’d need to see a decrease in cosmic rays. But look at the graph – it’s not there. The cosmic ray trend is flat, while global temperatures are spiking upward.

    You can dig into all the details in the IPCC report. Chapter 6, Section 6.4 (pg. 444) covers glacial-interglacial cycles and CO2. Chapter 2, Section 2.7 (pg. 188) covers solar variability. RealClimate also has good posts here and here.

  3. Brian
    Posted July 12, 2007 at 2:59 pm | Permalink

    It seems to me that those who still discount the scientific fact of global warming have a tendency to try to reduce this to a binary problem. But this is not a true/false question.

    CO2 is not THE cause of global warming. It is A cause… one factor in the complicated system that is our atmosphere.

    It just so happens that atmospheric CO2 is largely a byproduct of our own activities. That means we can change our behavior and reduce CO2 output. That one change, which we have control over unlike most of the other variables, may be enough to avoid disaster.

    Why is that so hard to understand?

    Off topic, but… The Economist had a great chart recently showing US gasoline consumption stacked up against every other industrialized nation in the world. We use more than all of them combined. This is our issue to take leadership on. If the US takes commits to action, the world will follow. Most of Europe is already on board.

    Look at the recent furor over Chinese food safety. If China’s, India’s, et al, “customers” demand change they won’t have a choice.

  4. vk279
    Posted July 15, 2007 at 3:35 am | Permalink

    I appreciate the feedback on this.

    On CO2 amplification: I assume the orbital changes you referred to are the ~100ka and longer Milankovitch cycles. There are apparently many problems with this model ( http://en.wikipedia.org/wiki/Milankovich_cycles#Problems ) yet it seems to be uncritically accepted at RealClimate and by the IPCC. I don’t see how it can be valid to attribute most of the warming observed in glacial/interglacial transitions to CO2 when it seems so unlikely that the trigger has been properly understood.

    On the Sun: There is evidence for the Sun’s activity increasing and cosmic ray flux decreasing (from proxies) to 1960. As you wrote in your third point, air pollution is believed to have caused cooling from 1940-1975. With pollution levels decreasing after 1975 it seems reasonable to expect to see temperatures return to 1940 levels and then continue to increase by an amount corresponding to the ‘masked’ solar activity increase from 1940 to 1960, despite there being no apparent trend in solar activity since 1960. Is this expectation realistic and if so is it accounted for in models?

    There seems to be an assumption at RC, in the IPCC report and elsewhere that the lack of a recent trend in solar activity implies warming in this time period cannot be solar in origin (i.e. that the above process and any similar lagged solar influences are unrealistic) and much of the warming is thus (perhaps incorrectly) attributed to CO2. I know there will be some contribution to temperature changes in this period from CO2 and other sources – it is the magnitude of the contributions, that I question.

  5. J.D.
    Posted July 28, 2007 at 1:53 am | Permalink

    Brian, two things:

    First, most skeptics understand that global climate is a “complicated system” as you say, and that’s precisely why we aren’t ready to accept “An Inconvenient Truth” as absolute truth. We recognize — in the spirit of scientific questioning — that there might be undiscovered explanations and we are therefor not willing to make the radical changes the true believers demand.

    Second, be cautious about the country comparison charts. While it may be true that the U.S. uses more gasoline than Europe or Japan, what these comparisons FAIL to tell you is that the other countries use MASSIVE amounts of nuclear power. The U.S. has decided to limit use of nuclear power for a number of reasons. If we were to start building more plants, then you’d see the comparisons level off…. but you’d also see the environmentalists complain about use of nuclear fuel.

    Additionally, the other factor is economic output. Sure we use more oil than France, but we also have a robust economy that allows for a high standard of living. France — where the people were protesting in the streets during the last presidential election because they didn’t want to work more than a 30-hour-a-week schedule — has an economy that is LESS THAN THE STATE OF CALIFORNIA! It’s true: California is the 5th largest economy in the world and regularly rivals France.

    Bottom line: We could slow down our economy, work less, do less, and ultimately use less oil. But the United States just isn’t that kind of a country. And for that reason country-to-country comparisons are quite misleading.

  6. Posted July 31, 2007 at 11:40 am | Permalink

    Hi J.D. Your comment makes two assumptions:

    1. …that the changes needed to reduce greenhouse gas emissions would damage the U.S. economy.
    2. …that there is no cost to inaction.

    Both of these assumptions are incorrect.

    Studies show that the cost of inaction is far greater than the cost of taking action. Here are links to two posts that explain why in detail:

    Green Technologies
    We Can Do It, and at Moderate Cost

    It’s not hard to see that Wall Street under water will have a serious economic impact!

  7. stateoffear
    Posted January 30, 2008 at 7:50 pm | Permalink

    First Swindle:
    Wait . . . so solar energy caused a warming trend, and the warmth caused a large output of CO2, right? So . . . how does the CO2 output cause more warming?
    Second Swindle:
    I actually agree with you on this one! The sun is a significant factor, there are several other earth based factors (what they are, however, we disagree on.)
    Third Swindle:
    Once again, sun dimming.
    Fourth Swindle:
    9-26% of the so called “Greenhouse Gas” concentration is CO2. It is said that most of the CO2 is fromthe burning of what are called fossil fuels. Fossil fuels include all forms of petroleum and coal. Note that coal–one of those evil fossil fuels–has been burned increasingly for an estimated 10,000 years; however, global warming is noted as a warming trend occuring over the last 100 years, with a 10-20 year break around the 1970s
    Fifth Swindle:
    Your explanation is a bit sketchy, could you expand upon it a bit more?
    Sixth Swindle:
    Same as fifth.
    Seventh Swindle:
    I don’t trust the proxies. The Medieval Warming Period was followed by a cooling trend from about 1400-1900 called the Little Ice Age. Even if glaciers had melted during the MWP (which isn’t necessarily true, the MWP is specualted to have only warmed .1-.2 Celsius degrees), about the same amount of water would have frozen during the LIA. The water in glaciers is fresh, which would have caused a decrease of ocean salinity. Ocean water has an average temperature of 4 Fahrenheit degrees, well below the freezing point (Salt water doesn’t freeze as easily as fresh water). During the LIA, the less salty ocean water would (a. re-freeze the thawed water from the MWP, and (b. precipitate back onto the barely-thawed glacier, causing a recoating of the missing top layer. Regular summers and regular precipitation have caused the newer top layer to go unnoticed, as the partial thawing and refreezing would be considered regular and very normal natural processes.

One Trackback