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Matt Ridley does a little bit more investigating on something I’ve been yawping about for a long time now: climate models are no better than macro-econometric models, and furthermore, there is absolutely NO consensus on what the magnitude (or possibly even the sign) of climate feedbacks is:

How can there be such disagreement about climate sensitivity if the greenhouse properties of CO2 are well established? Most people assume that the theory of dangerous global warming is built entirely on carbon dioxide. It is not.

There is little dispute among scientists about how much warming CO2 alone can produce, all other things being equal: about 1.1°-1.2°C for a doubling from preindustrial levels. The way warming from CO2 becomes really dangerous is through amplification by positive feedbacks—principally from water vapor and the clouds this vapor produces.

It goes like this: A little warming (from whatever cause) heats up the sea, which makes the air more humid—and water vapor itself is a greenhouse gas. The resulting model-simulated changes in clouds generally increase warming further, so the warming is doubled, trebled or more.

That assumption lies at the heart of every model used by the IPCC, but not even the most zealous climate scientist would claim that this trebling is an established fact. For a start, water vapor may not be increasing. A recent paper from Colorado State University concluded that “we can neither prove nor disprove a robust trend in the global water vapor data.” And then, as one Nobel Prize-winning physicist with a senior role in combating climate change admitted to me the other day: “We don’t even know the sign” of water vapor’s effect—in other words, whether it speeds up or slows down a warming of the atmosphere.

Climate models are known to poorly simulate clouds, and given clouds’ very strong effect on the climate system—some types cooling the Earth either by shading it or by transporting heat up and cold down in thunderstorms, and others warming the Earth by blocking outgoing radiation—it remains highly plausible that there is no net positive feedback from water vapor.

The rest is worth reading.

In short: We can now estimate, based on observations, how sensitive the temperature is to carbon dioxide. We do not need to rely heavily on unproven models. Comparing the trend in global temperature over the past 100-150 years with the change in “radiative forcing” (heating or cooling power) from carbon dioxide, aerosols and other sources, minus ocean heat uptake, can now give a good estimate of climate sensitivity.

The conclusion—taking the best observational estimates of the change in decadal-average global temperature between 1871-80 and 2002-11, and of the corresponding changes in forcing and ocean heat uptake—is this: A doubling of CO2 will lead to a warming of 1.6°-1.7°C (2.9°-3.1°F).

This is much lower than the IPCC’s current best estimate, 3°C (5.4°F).

But you see of course that this was published in the rag called the Wall Street Journal and Mr. Ridley is a paid lackey of the oil interests. Here is some more information on the leak of the IPCC 5th Assessment Report. Read it.

5 Responses to “Let the Ad Hominem Attacks Begin!”

  1. Speedmaster says:

    I do love Matt Ridley. Did you get to read his book Rational Optimist ( http://bit.ly/Sz4aNl )? Very Julian Simon, recommended.

  2. Trey says:

    The quip is “all models are wrong, some are useful”. I do modeling in the area of semiconductor manufacturing. Our product is evidently useful; we have paying customers.

    I’m curious whether this could be said about GCMs (global climate models)? One could argue that the customer is the government, which has to make policies. Governments effectively pay for most of the modeling. Still, I think a really good GCM would be viable in the free market, say hedging against risk of long term weather (climate, decadal trends). To my knowledge, these products are not available, which makes me suspicious that GCMs are useful.

  3. Harry says:

    Matt Ridley is an accomplished writer and reporter, and thanks to WC for this reference to his article in the WSJ. The crickets chirp, not just in Rochester classrooms, but also in Turtle Bay and Washington.

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