[updates at end of post- I am not so sure that the issues are as I originally laid out - comments welcomed] I was a little cautious about one element of the critique of the leaked IPCC report. This was the strong claim made by Alec Rawls that the leaked IPCC report highlights the importance of the sun in driving climate change. There was a backlash to this. For example, the New Scientist said this:
Climate scientists are lining up to debunk this claim, and to explain that the bloggers have simply got it wrong. “They’re misunderstanding, either deliberately or otherwise, what that sentence is meant to say,” says solar expert Joanna Haigh of Imperial College London.
The sentence in question is the bold sentence in this passage:
Many empirical relationships have been reported between GCR or cosmogenic isotope archives and some aspects of the climate system (e.g., Bond et al., 2001; Dengel et al., 2009; Ram and Stolz, 1999). The forcing from changes in total solar irradiance alone does not seem to account for these observations, implying the existence of an amplifying mechanism such as the hypothesized GCR-cloud link. We focus here on observed relationships between GCR and aerosol and cloud properties.
Alec Rawls has provided a rebuttal of the critiques. It is long, and I believe quite complex, and can be found here. As such, I thought I would have a go at simplifying the point that he is making (in as simple language as possible), although do so at some risk I will get it wrong. I am not very familiar at all with this area of science, but I think I have grasped the key principles of his argument:
- There is good empirical evidence that links the activity of the sun and global temperature
- One of these influences is total solar irradiance
- Total solar irradiance (which is known and can be accounted for) is, of itself, not sufficient to explain the linkage between the activity of the sun and the correlations with global temperature.
- Therefore something else must explain the linkages i.e. there is some other forcing mechanism from the activity of the sun that explains the linkage or ‘something’ is ‘amplifying’ the influence of the sun
- This might be the theoretical mechanism (backed by results from experimental work) in which solar activity impacts upon cloud formation
This is (in very simple terms) what I think is the gist of the paragraph quoted. There are points to note here.
- Observations are indicating a role for the activity of the sun on temperatures beyond what is currently being used in used in climate models. The models include solar irradiance, but not the other still uncertain/undiscovered amplifying mechanism.
- The passage accepts that the sun has a greater role in temperature than is currently used in climate models.
As you will have seen, there has been a response to Alec’s discussion which suggests that the context of the whole gives a different understanding. Indeed, there are even suggestions of ‘cherry picking’ and even outright dishonesty in the discussions of Alec’s argument. Central to the claim that the rest of the IPCC report is dismissive of the point in the paragraph is that other sections of the report cast doubt on the cloud formation theory. Therefore, they claim that the rest of the report does not support a greater role for sun activity in the climate, and this is why there is nothing in the report which supports a greater role in climate change for the sun.
However, this is a very, very large problem, if that is their logic. For the moment we will accept their claim that the cloud theory is poorly supported (which is questionable). That merely means one explanation of the larger role of the sun in temperatures is poorly supported, and does nothing to argue against the evidence that the sun is a larger influence on temperature than is currently accepted in the climate models.
It just means that scientists should be looking harder for explanations of the larger role of the sun in the determination of climate [Update: RichardC reasonably points out that some scientists are already working hard on this, but the IPCC is uninterested]. In the interim they should still alter their models to include the larger role of the sun in driving climate [update: see John Hutlquist's comment below for reasonable questions on this subject]. Whilst they might argue that they do not know what the additional amplifying mechanism is, they still need to accept the evidence that there is indeed an amplifying mechanism.
In summary, the argument in the IPCC report pretends that by casting doubts on a theory that exlains observation, they can then ignore the real implications of actual observations. These are not theory, and are observations. Casting doubts on a theoretical explanation of observations in no way makes the observations any less real! To pretend this is the case, is a sleight of hand, a magicians trick. It is getting you to look over there, whilst making the subject of interest disappear. If I have understood this correctly (and I am not certain of this), this is either a result of incompetence, or purposefully hiding an ‘inconvenient’ piece of evidence.
Important Note: In light of stepping out of my ‘comfort zone’ I welcome comments and corrections; for those who are reading; you should therefore check the comments below to see if any corrections have been made. Please note there may also be some comments which are from people who will seek to obscure rather than clarify the discussion that I have presented.
Update: In response to a comment below, I have added a large quote from the Economist, which discusses some of the science regarding the sun, climate and cloud formation. Being the Economist, it is well written, and for a lay audience. There is also a video with the original article which, if I remember when I first read the article, is very good.
Clouds are formed by the condensation of water vapour in the atmosphere around clusters of molecules such as ammonia and sulphuric acid. Ions created by the passage of cosmic rays can trigger the formation of such molecular seeds—a process of particular interest because the arrival of cosmic rays is regulated, in part, by the sun. The 11-year solar cycle, which governs the appearance of sunspots, also changes the sun’s magnetic field. That, in turn, affects the passage of cosmic rays (which are mostly protons released by distant supernova explosions), and thus the number of such rays that make it to Earth. Since clouds help regulate the climate, by reflecting sunlight back into space and cooling the atmosphere, some researchers think cosmic rays are a means by which changes in solar activity are translated into terrestrial climate change.
Just how much cosmic rays affect cloud formation has, however, remained elusive. A team at CERN, led by Jasper Kirkby, therefore decided to recreate both the solar cycle and the atmosphere in a lab. Their “cosmic rays” are generated by one of CERN’s particle accelerators. To simulate the atmosphere, they have built a special cloud chamber of their own, with the air manufactured from scratch, using liquid nitrogen and oxygen together with precise amounts of trace compounds, including sulphuric acid and ammonia.
A typical run at CLOUD, as the experiment is unimaginatively named, begins by tracking the growth of seeds from single molecules into clusters in the presence of ultraviolet radiation, which is known to encourage such growth. An electrical field removes any ions present, so the rate of seed growth should be equivalent to that in nature with no cosmic rays around. Next, the field is switched off, allowing actual cosmic rays to permeate the chamber for a while. Finally, a beam of artificial rays from the accelerator is added to the mix.
By comparing rates of seed formation during the different phases of the experiments, the researchers have been able to put a figure on cosmic rays’ contribution to the process. The results, reported in this week’s Nature, suggest naturally occurring rays enhance seed-formation rates by a factor of ten. That implies the rays’ varying intensity could indeed affect the climate.
Dr Kirkby and his colleagues remain cautious about the result, however, because of a second finding. To their surprise, they discovered that the seed-formation rates for sulphuric acid and ammonia are between a tenth and a thousandth of those needed to account for the cloud seeding actually seen in the atmosphere. That suggests other compounds are important, too—and this, in turn, implies that current climate models, which assume most seeds are made of ammonia or sulphuric acid, may require revision.
You may also wish to see this earlier article in the Economist, which gives further background, as it highlights the theory of Henrik Svensmark, who is a key theorist on the subject of cloud formation. I believe the science has moved ahead since these articles, but they do give a sense of the science at issue.
Another update in response to the comments and a little more consideration: This is with regards to the findings of correlations between the activity of the sun. There is a well worn statement that correlation does not equal causation (I recently stumbled across an interesting history of this, but forget where I found it, sorry). The best example I have seen as a simple illustration is that ice cream eating is highly correlated with hot weather, therefore eating ice cream causes hot weather (or the sun to shine). The point here is that correlations need a causal explanation. This is why the cloud seeding theory is important, as are other theories that link the activity of the sun to climate. However, as John Hutlquist points out in his comment, there are some correlations that are hard to ignore.
As you will note, I am starting to rethink a little on this issue. Science is about theory and observation, and that theory should be tested to see whether it is a true description of reality. There has to be theory in addition to observation. Added to this we have the question of intuitive plausibility. It seems intuitively plausible that the major driver of climate is the sun, but that does not make it true. However, when considering an intuitively plausible explanation and a less intuitively plausible explanation (i.e. the plausibility that human derived CO-2 emmissions are more influential in climate change than the sun), then it seems that there should be a desire to examine the more plausible explanation in great depth before settling on the less plausible.
In other words, we have some interesting observational evidence that is suggestive that the sun is more influential as a driver of climate than manmade CO_2. However, the mechanism for how the sun might have greater influence than the know solar irradiance is still a subject of hypothesis and theory testing. It appears, however, that certain members of the scientific community are resistant to the possibility of the sun as a more significant driver of climate than CO_2, and wish to stick with their own (less intuitively plausible) explanation in the face of a more plausible explanation. They do not seem to want to engage with those who are engaging in the process of testing of an alternative hypothesis. Further, whilst their current hypothesis has resulted in model predictions, the predictions are not doing well in face of observation. This should be a driver towards greater interest in the alternative (and more intuitively plausible) hypothesis.
As I have pointed out earlier in the post, I am not in a position to evaluate the science, but I think I am starting to see something of the questions raised in the IPCC leaked report. If they can demonstrate that the current theories of amplification of the influence of the sun are wrong (which I gather they have not), then they could argue that there is no mechanism given for how the sun might be a more important driver for climate than CO_2, and then argue that without a mechanism, the observations are nothing more than coincidence. Correlation and causation are not enough. However, their own theory, as expressed in models, is failing to predict, meaning that their theory is problematic, and that the observations of solar drivers of climate seem to better fit observations of the climate.
In these circumstances, rather than seeking to discredit the sun as a more significant driver of climate, they should be actively looking themselves at the possibilities, and seeking their own explanations. Instead, their minds seem made up so that, whatever faults there are in their own theory, it must be defended to the hilt. After all, the big ball of energy that is the sun seems a plausible candidate for being a major driver of the climate. This stiff-necked approach now seems to me to be the issue at hand. Why are the IPCC scientists so resistant to the alternative explanation for climate variability in the face of the problems with their own theory? There are observations, there are possible causal mechanisms, there are interesting questions which should spur scientific interest (all science commences with questions). Why the disinterest?
Note: A second thanks to John for his comment on models, which spurred this rethink. I think he was gently making the correlation/causation point in the question about models.