That certainty again

It was reassuring to see the condensed lists that Judith Curry made as a preparation for the NARUC Panel Discussion on Climate Change. In her post she also described the opening statement of Dr. Joe Casola. It is interesting to hear the other side. As expected the difference is rather small.

Joe Casola is Staff Scientist and Program Dir. Sciences & Impacts at the Center for Climate and Energy Solutions. This is the first list that was found in his presentation:

The big picture:

1. Carbon dioxide (CO₂) and other greenhouse gases make the planet warmer
2. CO₂ is accumulating in the atmosphere
3. The planet is warming
4. Warming is best explained by humans’ emissions of CO₂ and other greenhouse gases
5. Future warming should be expected

The first three points are no problem. They can be agreed on by believers and skeptics alike. We saw them in my list as well as in Judith’s list.

The fifth point is a bit more controversial. Some skeptics seem to strongly believe it will cool down in the future. I don’t know what it will bring, but it would not surprise me if temperatures could go up again. The difference with the alarmist view is that I don’t think it is not necessarily an all bad thing.

The third point is however something in which alarmists and skeptics differ in opinion. Although it seems valid at first sight, logically it is not really sound. He explains it further in his presentation:

Warming is best explained by our emissions:

• Magnitude and rate of warming is large (warmer than in last 400 years, at least; ice ages only ± 5°C)
• Spatial and vertical pattern of warming matches what greenhouse gases “should” do
• Changes in other factors that drive climate (like the Sun) don’t explain warming
• Models can only replicate 20th century warming when greenhouse gases are included

I don’t know much about the second point, but the other points are rather weak. That the magnitude and rate of warming over the last 400 years is large doesn’t necessarily mean that it is humans that are doing it. We have reliable data for temperatures for the last 30-40 years and sparse, less reliable data from around the middle of the 19th century. How on earth can we make conclusions over long-term variability with this data? Casola seem to ignore the many uncertainties that are there because of the incompleteness of the available data.

Those other factors don’t seem to explain the warming since the half of the 19th century doesn’t mean that there isn’t another factor that we didn’t look at or didn’t considered yet. Suppose there was a cold period (in history it is called “The Little Ice age”), then it is entirely possible that there is a long-term cycle going on, longer than when we measured temperatures reliable. Then it is entirely possible that we came out of a cold part of a long-term cycle and what can we expect from this other than warming? So I am not really sure that there no alternative to the CO₂ theory.

There is also the problem that the temperature as it is recorded shows cycles of about 60 years and we see an increasing part from 1850s-1880s, from 1910s-1940s and also one from 1970s-1990s, both with a similar slope. The first two apparently attributed to natural variations, the latter to global warming… Plus the recent stabilization of temperatures in the last 1,5 decade when CO₂ levels went through the roof. Is this really how CO₂ works? If natural variation is strong enough to suppress the effect of CO₂ in the last 1.5 decade, then why would natural variation have had little or no effect from the 1970s until the 1990s?

That models aren’t able to replicate the 20th century warming without greenhouse gases is a fallacy. Due to the complexity of the climate system, the mathematical models only consist of a limited number of variables and as far as I know they are build on the assumption of CO₂ being the main reason. So failing to replicate the 20th century warming in such a modeled system doesn’t mean that the real climate system depending on CO₂. In that case it is circular reasoning. By the way, if the models were able to replicate the climate system, fully or even mostly, then there would only be a need for one model and it would have predicted the “pause”.

These are the conclusions he came to:

What does this mean for regulators and the electricity sector?

• The BIG PICTURE is not a subject of debate within the scientific community
• There ARE many aspects of climate that are not completely understood, but do not undermine the BIG PICTURE understanding
• Best translation into a policy context = RISK MANAGEMENT approach
• Compared to other business and environmental risks, we actually have lots of information about climate change!

That is big picture as he sees it is not subject of debate, I dare to doubt. The thing that strikes me again in this list is the ignoring of uncertainties. He assumes that models can mostly replicate the climate system. That the aspects that are not yet really understood have no relation to the big picture. How does he know? How could we know? He assumes that the information we now have from a chaotic complex system is sufficient to base decisions on.

Where does that certainty originates from? Does he know the intrinsic uncertainties of a chaotic, complex system, but doesn’t deem them important? Or is it just trust in those who claim there is no uncertainty?

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