Is Anthropogenic Global Warming by definition Catastrophic?

It have been said many, many times before. There supposedly is a scientific consensus that increasing anthropogenic CO₂ concentrations in the atmosphere are responsible for most of the warming we experienced. It has been said in many variants and is said to justify (immediate) action on climate change.

In the two last posts I wondered what exactly there is a consensus about? My take is that it might be something different than what is communicated.

A couple weeks ago I looked at the Crossing the 2014 Climate Divide: Scientists, Skeptics & the Media video. The first three posts of March were about the first part starring Suzanne Goldenberg (The Guardian). In it also Naomi Oreskes was present. She talked about her experiences with the skeptics and how she entered the climate debate. It was mostly about the extremists, you have them on both sides, not really interesting for me. But it was also about how she came to believe and documented the “consensus”. That was more interesting. Her work is widely cited by many alarmists as a confirmation of the existence of the scientific consensus on global warming.

This is how it was presented: BEYOND THE IVORY TOWER – The Scientific Consensus on Climate Change. What she did was downloading the abstracts of 928 peer reviewed articles which she found when entering the key words “global climate change” for the period of 1993 until 2003 in the ISI database (Institute for Scientific Information).

The question she had was how many papers disagreed with the position of the US National Academy of Science and the IPCC:

Human activities … are modifying the concentration of atmospheric constituents … that absorb or scatter radiant energy. … [M]ost of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations

The conclusion was none: 75% of the articles accepted the “consensus” and 25% were taking no position. This is a subjective thing. Some others have tried this and came to other conclusions. But I have no access to the ISI database, so I will not go there. I will try to look at the method and the definition to see how far I get.

The first statement is something everybody can agree with, at least I have not seen someone disagreeing with that. The Keeling curve learns that the CO₂ concentration is rising, at least since 1958 when measurements began. Nothing controversial here. But at such it doesn’t proves much.

Greenhouse gases absorb or scatter radiant energy. Also nothing controversial here.

The last statement seems detailed at first glance, but is a bit more ambiguous:

• Most of the warming: most is rather ambiguous. It is at least from somewhat above 50% until a bit less than 100%. Let alone how to quantify “most” in an abstract. Okay, let’s assume that this is possible and it is reliable enough to measure the abstracts.
• Likely: according to the IPCC this means larger than 66%. Okay, there is at least 66% chance that “most” of the observed warming over the last 50 years is due to increase of greenhouse gas concentrations. That means there is 34% or less chance that “most” of the observed warming over the last 50 years is NOT due to the increase of greenhouse gas concentrations.

However, the obvious missing part is the fact that nowhere is stated that this increase is dangerous or leads to catastrophic changes in our climate, therefor needing immediate action. The only thing this statements tell us is that scientists are certain that there is an increased concentration of CO₂ in the atmosphere (which is true), that this absorbs or scatters radiant energy (which is also true) and this could mean that part of this increase is caused by our emissions.

That is really uncontroversial. All the skeptics that I know of agree with that. They acknowledge that there is more CO₂ in the atmosphere because of our emissions, that it is a greenhouse gas and it will give more warming, everything else being equal. There are some differences though. Like how sure are we about the warming considering the scarce climate data we accumulated from the past? How sure are we about the projections of the temperatures into the future? How sure are we about a warmer world worse than a cooler world? Etcetera. Nothing in this position point out that this warming is bad, but that is how it is marketed.

The measured consensus is about something uncontroversial and has absolutely nothing to do with the extent of the assumed danger associated with this warming, nor with the necessity of action to prevent this increase in warming.

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