1. Antarctic ice cores showing lag between warming and rise in CO2 concentrations:

Antarctic ice core samples show that the rise in carbon dioxide levels lags behind temperature rise by 800 years, therefore cannot be the cause of it.

[Answer - This is based on correct info, but presented in a misleading way:

Not quite as true as they said, but basically correct; however they misinterpret it. The way they said this you would have thought that T and CO2 are anti-correlated; but if you overlay the full 400/800 kyr of ice core record, you can’t even see the lag because its so small. The correct interpretation of this is well known: that there is a T-CO2 feedback…

The RealClimate scientists then go on to provide a link to one of their previous posts on the subject.]

2. Mid-century cooling:

From the 1940’s until the 1980’s, the Earth experienced a significant cooling period, despite the fact that industrial production and release of CO2 vastly accelerated during this time.

[Answer - It is also correct that there was a slight cooling from the 40’s to the 70’s while CO2 concentrations continued to rise, but this is not because the two are not correlated. The climate is very complex. There are many factors at play. During this period, sulphate aerosols became a dominant negative forcing, which means that they had a cooling effect. Since that time, we have successfully cut aerosol emissions because of concerns about the ozone and acid rain. Consequently, CO2 has become an even more dominant positive forcing:

They presented this as a major flaw in the theory, which is deeply deceptive, because as they and their interviewees must know, the 40-70 cooling type period is readily explained, in that the GCMs are quite happy to reproduce it, as largely caused by sulphate aerosols.

The RealClimate scientists again provided more links.]

3. Solar activity parallels temperature change:

Sun spot and solar radiation activity almost exactly parralel temperature change on the Earth. “Solar activity very precisely matches the plot of temperature change over the last 100 years. It correlates well with the anomalous post-war temperature dip, when global carbon dioxide levels were rising.”

[Answer - It does seem to, until after 1980. Let’s look at the graph that was shown in the documentary:

You’ll notice that the data for solar activity stops at 1980. There is a specific reason for this: the rest of the data does not follow the temperature data anymore. This is the point at which temperature breaks away from the solar activity, in a sharp upward trend:

First off, notice that the data plotted *isn’t* solar variation directly, but an index of solar cycle length. There was speculation that it might be related to solar variation, but this was never clear. Now notice that the solar graph stops in 1980. Why could that be? Look at D+L’s figure 1c: when the correct data is used, the upturn after 1980 disappears and the correlation with temperature disappears. Oops. Best not mentioned…

The actual corrected solar activity graph can be found in Figure 1-c in this paper by Damon and Laut. The solar activity, superimposed on the temperature data can be found in Figure 2. Once again, the documentary presented the data in a very misleading manner.]

4. Troposphere heating slower than surface:

If the Earth was laboring under an accelerated greenhouse effect caused by human produced CO2, the troposphere (the layer of the earth’s atmosphere roughly 10-15km above us) should heat up faster than the surface of the planet, but data collected from satellites and weather balloons doesn’t support this fundamental presumption.

[Answer - This argument comes from antiquated satellite and weather balloon data that has since been corrected. In 2003, Dr. John Christy, professor at the University of Alabama at Huntsville, published a paper that was the result of almost 25 years’ worth of collected satellite and weather balloon data, which seemed to suggest that not only was there almost no warming, there was possibly even cooling occurring in the tropical regions of the planet. This data also seemed to show a discrepancy between the warming at the surface and in the troposphere. Since that time, other scientists have published papers that served to correct Christy’s data to the point that it basically mirrored that of the predictions of models that most other climate scientists used. As RealClimate says, Christy even admitted as much:

Christy (naturally enough) features in this section, though he seems to have forgotten the US CCSP report, and the executive summary which he authored says, “Previously reported discrepancies between the amount of warming near the surface and higher in the atmosphere have been used to challenge the reliability of climate models and the reality of human induced global warming. Specifically, surface data showed substantial global-average warming, while early versions of satellite and radiosonde data showed little or no warming above the surface. This significant discrepancy no longer exists because errors in the satellite and radiosonde data have been identified and corrected. New data sets have also been developed that do not show such discrepancies.”

I do not know why Christy would appear on this documentary and make claims that contradict his own corrected research and his own written statements, but that doesn’t matter. What matters is what the data shows, and according to the data, this is yet another false claim.]

5. Man-made CO2 minimal in comparison to natural sources:

The human contribution to carbon dioxide in our atmosphere is minimal in comparison to other natural means, including volcanic emission and CO2 produced by animals, bacteria, decaying vegetation and the ocean. The human “carbon footprint” is vastly outweighed by all of these factors.

[Answer - This is a tricky one. It is very similar to the skeptical argument that water vapor by far the most abundant greenhouse gas, so human activity could not possibly be causing global warming. However, both of the arguments fail to differentiate between static concentrations of GHGs and changes in GHG concentrations. It is the change that we are worried about. There is a natural, static amount of certain GHGs in the atmosphere, which help to keep the Earth warm. However, if human activity results in the manufacture of additional GHGs, this has an added warming effect, which can heat the Earth too much. In recent years, the concentration of CO2 in the atmosphere has sky-rocketed, and there is little if any debate on the cause of this significant increase:

Over the last 150 years, carbon dioxide (CO2) concentrations have risen from 280 to nearly 380 parts per million (ppm). The fact that this is due virtually entirely to human activities is so well established that one rarely sees it questioned.

This recent increase in CO2 concentrations, as a result of human activity is what is responsible for the increase in temperature that we are currently seeing.]

6. Lag between warming and increase in CO2 concentrations prior to 1980’s:

…why is the lag period between temperature rise and CO2 rise prior to the early 1980s not compelling evidence of a causal link that increasing global temperature causes rising CO2?

[Answer - There was indeed a time lag, but there were two factors at play in the middle of the last century that caused the anomalous cooling trend. First, it takes some time for new amounts of CO2 to rise into the atmosphere. Second, there was an increase in sulphate aerosols during that time period, which are negative forcings (they provide a cooling effect):

They then proceed to give an overly simplistic view of the climate, stating that during the heaviest industrialisation post-WWI, there was global cooling - therefore CO2 had no effect. They fatally neglect the time lag for warming from CO2, or the cooling impact from aerosols like SO2.

So, the new CO2 that resulted from heavy post-WWII industrialization had not yet taken effect, while at the same time, an increase in sulphate aerosols was causing more of a cooling effect. As I explained in an earlier answer, we’ve since curbed aerosol emissions because of concerns about acid rain and the ozone layer.]

7. Dominance of solar activity:

…why is it not possible that since the 1980s the effect of industrial CO2 rises have added (proportionately or otherwise) to a predominantly solar driven event?

[Answer - First, if you look at the links I provided in response to question 3, you’ll see that, due to mathematical errors, it is now clear that there is no correlation between solar activity and temperature increase after 1980. Second, as the “Radiative Forcing Components” chart on page four of the latest IPCC report’s summary shows, solar activity accounts for a very small portion of the warming effect on out planet, when compared to the many other factors that are involved, especially greenhouse gases.]

8. Explanation for localized Little Ice Age:

having visited several sites today i have seen doubts cast over the validity of sun spot data and the apparent correlation between reduced solar activity (as crudely measured by sun spot counts) and the so called Maunder Minimum. If this event was ‘localised’ as is being suggested, why did it last so long and effect most of Europe for decades?

[Answer - As I understand it, much of this observed cooling is attributed to oceanic changes:

Shindell et al (2001) alluded, however, to the possibility that a sustained negative phase of the NAO would lead to a minor weakening of the North Atlantic meridional overturning circulation,

The GISS model results and empirical reconstructions both suggest that solar-forced regional climate changes during the Maunder Minimum appeared predominantly as a shift toward the low AO/NAO index. Although global average temperature changes were small, modeled regional cooling over the continents during winter was up to five times greater. Changes in ocean circulation were not considered in this model. However, given the sensitivity of the North Atlantic to AO/NAO forcing (37–Delworth and Dixon, J. Climate, 2000), oceanic changes may well have been triggered as a response to the atmospheric changes (38–Broecker, PNAS, 2000). Such oceanic changes would themselves further modify the pattern of SST in the North Atlantic (39–Visbeck et al, 1999) and, to a lesser extent, the downstream air temperature anomalies in Europe.

Jones and Mann later expanded on this point in a review paper published in 2004 in the journal Reviews of Geophysics (see final paragraph of section 5.3 therein). The argument basically goes as follows: a sustained forced negative state of the NAO pattern would lead, based on the experiments done by Delworth and Dixon (2000), to a small, but detectable [1-2 Sverdrups (’Sv’) - or about 5-10%) decrease in the North Atlantic meridional overturning circulation (MOC), which in turn would lead to an additional pattern of cooling over the North Atlantic during the height of the LIA. This seems consistent with the small change in the strength of the “Gulf Stream” inferred by Lund et al study for the LIA.

This view that the LIA was localized is widely accepted among climate scientists.]

9. Cosmic ray theory of cloud formation:

I am also reading that the cosmic ray theory of cloud formation is highly faulted. Yet the indirect data relating to cloud cover and solar activity again at first sight seems compelling. What is wrong with this data?

[Answer - One of the commonly cited works on this subject is not even peer-reviewed literature:

The argument from Nigel Calder and Danish space science skeptics has featured on this blog before, and on BBC’s Newsnight - where Calder was thoroughly demolished by an atmospheric physicist from Imperial College. Basically, the Danes have found that cosmic rays produced ionized particles, an published it in a peer reviewed paper here. The article made no mention of global warming or climate change, but Calder and the Danes wrote a book anyway, making numerous jumps of assumption to say that those ionized particles would produce more clouds and thus cool the Earth. However, those assumptions have not been peer-reviewed, and there exists no long-term trend for cosmic ray flux, while global mean temperature keeps rising.

The scientists at RealClimate have provided an impressive critique of this theory:

The working hypothesis of the cosmic ray crowd is that the (weak) correlations between low clouds and cosmic rays are causal (i.e. a cosmic ray increase - due to a solar magnetic field weakening - causes low clouds to increase, cooling the planet). The ’spin’ on this new paper is that this has been demonstrated, and is significant, and furthermore, is responsible for the 20th Century rise in global temperatures. But let’s look carefully at what is required in this logic:

First, the particles observed in these experiments are orders of magnitude too small to be Cloud Condensation Nuclei (CCN). In the press release, this is why they talk about the ‘building blocks’ of CCN, however, aggrandisation of these small particles is in no sense guaranteed (Missing step #1). Secondly, the focus is on low clouds over the ocean. However, over the ocean, there are huge numbers of condensation nuclei related to sea salt particles. Thus to show that the cosmic ray mechanism is important, you need to show that it increases CCN even in the presence of lots of other CCN (Missing step #2). Next, even if more CCN were made, you would need to show that this actually changed cloud cover (or optical thickness etc.) (Missing step #3). And given that change in cloud properties, you would need to show that it had a significant effect on radiative forcing - which despite their hand waving, is not at all well quantified (even the sign!) (Missing step #4). Finally, to show that cosmic rays were actually responsible for some part of the recent warming you would need to show that there was actually a decreasing trend in cosmic rays over recent decades - which is tricky, because there hasn’t been (see the figure) (Missing step #5). All of this will require significant work and there are certainly no guarantees that all the steps can be verified (which they have been for the greenhouse gas hypothesis) - especially the last! However, they would seem essential to justifying the claims in the press releases.

It seems that so far, the version of this theory that is heralded by climate skeptics such as the Mr. Durkin consists of weak correlations and lots of spin, rather than sound science.]

10. Assumption that curbing CO2 production necessitates limiting progress:

I am concerned about the political ramifications of dictatorial measures to curb CO2 production in the future where it involves pressurising developing countries to limit their technological progress and industrialisation. My concerns are that (what ever the cause) should the worst predictions of climate change prove correct, how are the people in these countries going to adapt quickly to cope with the impacting changes if they are not allowed to develop?

[Answer - Stifling industrialization and development is not the only way to curb CO2 emissions. We can invest in and transition to cleaner sources of energy:

By associating CO2 emissions with industrialisation and economic growth, the documentary plays an emotional trick by making us think that the quality of life we have will be taken away from us if the environmentalists had their way. While CO2 emissions are indeed associated with industrialisation, it is not a relationship that cannot be undone. For example, Vestas in Denmark have generated immense wealth by producing wind power generators. China has recently decoupled economic growth from greenhouse gas emissions growth (link).

This is another common straw man argument that is used by skeptics.]

11. Potential political advantages of having global warming as “enemy”:

I am aware that there are political advantages of having an enemy (Global climate change in this case) that can, with great effort be overcome. The great efforts (additional taxes, continued cheap labour forces in developing countries and a slowing of the use of a finite resource; oil, coal, gas)are potential politically stabilising goals. Additionally a ‘defeatable’ enemy allows governments to focus the attentions of the masses if somewhat fearfully, in a controlled fashion.

[Answer - Assuming motives doesn’t prove anything about the validity of the findings of the scientific community on climate change. There is also the potential motive of those in the energy industry, who stand to gain from not being forced to take action. While this may make me skeptical of the arguments funded by them, it does not, by itself, convince me that they are wrong. What is most important is that we not get caught up in conspiracy theories, and instead focus on the science behind prevailing theories on climate change.]

12. IPCC censored dissenting scientists:

The UN’s much vaunted IPCC report was heralded as closing the case on the argument of man-made global warming. But as the show explains, they deliberately censored any dissenting scientists while still listing them as participants, leading many to threaten legal action against the IPCC to have their names removed from the report. Scientists who were invited to participate in the IPCC report expose the fundamental flaws contained throughout the document.

[Answer - This is one that I simply do not have an answer for right now. I live in the United States, so I was not able to see the documentary. I would need more information about who was making these claims, what they specifically disagreed with, and what the response from the IPCC leaders is. I will look into it.]

I hope these responses help to provide some insights on the assertions that were made in the “Great Global Warming Swindle” documentary. Please let me know if there are any further questions or concerns.