Monthly Archives: September 2014

Is there a consensus whether global warming is dangerous?

One of the many things that I found remarkable in the Cook presentation was the slide with the well known tweet of the President of the United States (actually the organization that manages his tweet account):

twitter 20130516 ninety-seven-percent

This tweet was not a surprise as such. I have seen this tweet many times before and I know how it was used. The surprise is that it was presented here.

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It is all about perception

Looking back at my trip to Bristol, it was a wonderful experience. Bristol is a nice city and I made several enjoyable walks in Clifton and surroundings. I also had the opportunity to be in the presence of other skeptics. I was humbled by so many prominent bloggers. Being able to experience that was a honor to me. Many thanks to Richard and Caroline for making this possible.

The lectures on the other hand were a weird experience. There was a strange lacking of science. I was expecting a bit more scientific backbone in both talks. They didn’t deliver on that one and stayed very superficial. “The debate is over” and all that.

The biggest thing I realized from the lectures is: this has nothing to do with the science anymore. The science is used to gain trust of the public. That is where the consensus comes in. If the public has the perception that there is a consensus between scientists, it increases their acceptance and support of climate policies. It is political in nature. There is no doubt that this was the goal of the Cook et al paper. They written it in the introduction as well as in the conclusion.

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The Mann lecture: the science missing in action


Been to the Mann lecture “The Hockey Stick and the Climate wars – the battles continues” yesterday. It was a weird experience, to say the least.

The lecture itself was bland. There was absolutely no depth and it was extremely one-sided.

We saw Mann the green activist, the political activist, the noble man, the preacher, the sales man, stirrer of emotions, the poor victim. I missed one person on stage and that was Mann the scientist.

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The accuracy of the proof or the accuracy of the selection?

cook presentation 97% consensus

There wasn’t anything new in the Cook lecture, yet there was one thing that showed me a new way of looking at the consensus. I already knew there were different studies and I knew they show about the same results, but I had not yet seen the results shown in one image.

If I would look at it with the eyes of somebody who was ignorant on the matter, I would be really impressed by such results. They get the same result every time, even with different methodologies. Looking like that, I would surely think that this 97% value is a pretty plausible figure, a robust quantification of the consensus.

But by looking at those numbers next to each other, it dawned on me. My first thought was: “No way!”. I looked into the methodologies of those three studies earlier and I must admit that I have a hard time believing that with such crude methodologies and rather ambiguous statements, one could get about the same results with just a couple tenths of a percent difference!

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The Mother Of All Hockey Sticks

My visit to Bristol wasn’t reserved for the Cook and Mann lectures alone. Some months ago, I was already planning for visiting this area of the UK, some undefined time in the future. Both lectures were the perfect opportunity to make this trip a reality, sooner than I was thinking. So I am more or less functioning in holiday mode right during my stay.

Today I went for a long hike in Clifton, Cliftonwood and the Old City. I combined two hikes and improvised an additional part. Accumulating quite some miles with my faithful hiking shoes.

It was a diverse route with beautiful lanes, cozy parks, steep hills with a view, a stroll along the river Avon and many boats, old and young, displayed along it. Above all the weather was real nice. Although the locals seem to be dressed much lighter than me. I guess they are used to much cooler weather. I even forgot to bring sun protection, I thought that “Britain and sun milk were not really compatible”.

Wrong. Wrong. Couldn’t be more wrong. Probably has to do with, ahem, global warming, or so.

Anyway, I will have a nice tan tomorrow 🙂

I arrived at the hotel in the early evening, took a well deserved hot bath and went for a bite. Refreshed and replenished I checked my email and the WordPress Dashboard. Nothing could prepare me for what I saw next in the stats:

stats 20140921

Woooooow, what’s that?!?! That is not even a hockey stick, that is The-Mother-Of-All-Hockey-Sticks! When I last looked at it in the morning, I counted exactly five views. That is on average the normal amount for this tiny little blog, so I thought that would be it for the day. Now after the hike my blog suddenly had more views in one day than I would have in two months! The same was true for the comments. And the day wasn’t even over yet (in the meanwhile when I am posting this it seems total views were well above 300-mark and had to rescue some comments from the spam folder).. It caught me completely by surprise.

Is it already enough to be in the same city as The Mann to notice hockey sticks all over the place?

The answer to the mystery was a bit more down to earth. Most of the traffic came from wattsupwiththat. Anthony linked to my previous post. Thanks, Antony. Thanks also for the many visitors for passing by and for the commenters who took the effort to write their valued thoughts or corrected me were needed.

You all made my day.

One analogy too far

Several times in the Cook lecture I couldn’t resist smiling and thinking that he couldn’t believe that himself. Could he? The first time was when Cook said that for complicated issues we rely on the experts and then gave an analogy: bridges. The public is trusting those who build bridges. They trust that bridges are save to cross. The implication seems clear. Why shouldn’t we give the same trust to our climate scientists? Those are the “experts” when it comes to the climate.

I heard that one in several variations and it is rather funny if you think about it.

Sure, I trust that crossing a bridge is save. I realize that bad things can happen (like for example the Tacoma bridge), but this happens rather seldom. It is fair to say that bridge engineers know what they are doing and I have no problem trusting their expertise when walking across a bridge.

Analogies are great, but only go as far as the similarities go. Climate science is a different kind of breed compared to engineering. People build bridges for many thousand years. In engineering the basis is well established, the properties of the materials well known. Feed this into a model and it will work pretty reliable.

Compare that to climate science which is a fairly new science that is studying a very complex matter. Many things are not (well) known, observational data is only available from the end of the 1970s, uncertainties are huge, the science politicized,…

So the comparison is rather flawed. Let’s make the correct comparison.

Suppose you knew that the technology of building bridges was fairly new. Suppose you knew that the technology of bridge building was based on scarce and incomplete observational data. Suppose you knew that only few bridges were build and that most of them collapsed. Suppose you knew that the properties of the materials were hardly known, there were huge uncertainties on how all these things fit together and nobody knew exactly how they would act under a load.

Would you be able to cross that bridge in a relaxed way?


When lookingt at other commentaries they seem to focus more on the question “if 97% say the bridge will collapse and 3% who say the bridge will not collapse, who to believe?”. Maybe I missed something while making notes. For some reason I connected the “expert” statement with the analogy, probably because they followed each other. Have to check with the video how it was actually brought.

Whatever be the case, the analogy will always fail because of the incorrect comparison of bridge engineers (who study a well defined, well understood topic) with climate scientists (who study a complex system with huge uncertainties). Therefor it can easily be reversed. If that 97% agreement is based on incomplete data, processes not yet (well) understood,… then whatever the level of agreement is that the bridge will fail, it will be basically meaningless.

There are also many other possible analogies. See below in the comments for additional thought experiments.

The consensus explained: cats are difficult to herd, but apparently can agree with each other

Just a quick post on the Cook lecture yesterday. It was an interesting lecture and there seemed to be quite some skeptical voices present. For whatever reason, there were however a lot of seats still empty.

In general I didn’t hear anything new in the lecture. If one reads his paper and visited the skepticalscience blog it would all be very recognizable.

It started a bit odd however. Cook showed the statement that scientists rely on testable evidence and that they are like cats, difficult to herd. To be honest, I didn’t really expect such quotes. These are usually used by skeptics. It made me even more curious about what would come next. His research can not possibly follow from those … this promised this be an interesting lecture…

Then came a question to the public if someone could explain the process global warming. He said he asked it several times in other occasions, yet only one seemed to have answered it correctly until now. To him it was a two way process and most of the people who answered it, explained only one of them.

The two processes are: carbon dioxide is transparent for sunlight, but laying a blanket over the earth so less heat escapes to space. To him these were testable processes. Less heat escapes to space, more heat getting trapped, so a cooling of the upper atmosphere, hence shrinking, etcetera, etcetera. He says that the observations of these lines are consistent with carbon dioxide being the main culprit.

Then came the jump. The fact that scientists agree with each other (despite being cats which are difficult to herd) means there must be many lines of evidence. Otherwise it would been impossible to agree with each other…

Wow, I am not sure if I follow that one!

In school we learned about logical fallacies. The teacher explained us that a conclusion can only be reliable if all the premises are valid. In this case there are two premises. The first is: scientists are like cats, difficult to herd. One could of course debate everything, but this one I could accept.

The second premise is a bit more tricky. When history teaches us something, it is not necessarily true that scientists agree on something because of multiple lines of evidence. It can be true that some scientists agree with the theory of global warming because of multiple lines of evidence or the evidence they found their field. But this is not necessarily true for all the scientists who have an opinion on the issue. In the Cook survey most, if not all, papers were not on attribution, but the theory was their starting point. These authors believed in it, but it is not sure if they concluded that from the different lines of evidence or that they did it because they just had trust. In the Cook survey it was not analyzed WHY they endorsed it.

In short, there are several reasons possible why scientists agree with each other. Knowing the evidence could be one of them, but this is not certainly the only one.

Put a scientist in a place where his tenure or his income depends on adhering the consensus and that could change the game completely. Or consider a scientist in a very polarized debate where the respect of his peers comes into the line (see the peer pressure on Bengtsson). Then we have a different situation were contradicting the current theory is not that interesting anymore, yet adhering is. Also climate is a very complex system, involves different specialization, comes with huge uncertainties and very little reliable data before the 1980s. In such a system it would be a downright miracle if scientists agree with each other in such a high degree.

To me that is the Achilles heel of this survey. Sure they made a big effort in analyzing the title/abstracts of 12,000+ papers and I admire them for their persistence. Yet the basis of their conclusion is not holding much water.