Friday, March 28, 2008

Another Word on Climate Change

It was a pleasant surprise to see Physics Today feature an article1 questioning the consensus on global climate change. The piece is rather technical, but from what I can glean, it sounds like the authors are pointing to at least circumstantial evidence that the "majority" opinion is ignores some key information.

Earth's atmosphere, landmasses, and oceans absorb and redistribute the total solar irradiance (TSI) by means of coupled nonlinear hydrothermal, geochemical, and radiative dynamic processes that produce Earth's globally averaged temperature at a given time. Versions of those physical mechanisms are included in the GCMs [global climate models], but what is not addressed in the simulations are the statistics of the time series. Those series consist of the monthly values of temperature anomalies. The statistical variability in Earth's average temperature is interpreted as noise; the temperature fluctuations are thought to contain no useful information and are consequently smoothed to emphasize the presumably more important long-time changes in the average global temperature, typically on the order of years. According to the central limit theorem, the statistics of the fluctuations in such large-dimensional networks ought to be Gaussian. The fact that they are not remains unexplained.

In other words, the difference between global climate model predictions and the actual global temperatures (on short time scales) are supposed to be random in a normal sense ("Gaussian distribution"), but aren't. This fact implies that there is some sort of non-random dynamic at work. The models can't account for this dynamic. The authors however show that the statistics of the fluctuations are similar to the statistics for solar flares. While this isn't proof that the two are connected, it is at least circumstantial evidence. But it does clearly show that the majority consensus is insufficiently thorough and far from the certainty they tout.

The authors then go on to show the sensitivity of global temperature to the 11- and 22-year solar cycles. That global climate models reflect neither this long-time-scale sensitivity nor the short-term sensitivity shows that these models are underestimate the contribution of total solar irradiance (TSI) to Earth's temperature.

The nonequilibrium thermodynamic models we used suggest that the Sun is influencing climate significantly more than the IPCC report claims. If climate is as sensitive to solar changes as the above phenomenological findings suggest, the current anthropogenic contribution to global warming is significantly overestimated. We estimate that the Sun could account for as much as 69% of the increase in Earth's average temperature, depending on the TSI reconstruction used. Furthermore, if the Sun does cool off, as some solar forecasts predict will happen over the next few decades, that cooling could stabilize Earth's climate and avoid the catastrophic consequences predicted in the IPCC report.

It's a hopeful sign that Physics Today would publish this article. Still, I expect to read outraged responses in the letters section in coming months. People refuse to listen to an alternative point of view once their mind is made up. Kinda like refusing a prisoner a hearing to determine if he's a terrorist because you're already convinced he's a terrorist.


1. Featured as "opinion" probably because they fear the PC backlash.

Unfortunately all of these articles require subscription for access:

Nicola Scafetta and Bruce J. West, "Is climate sensitive to solar variability?," Physics Today 61:3 (March 2008), pp. 50-51.

N. Scafetta, B. J. West, "Solar Flare Intermittency and the Earth’s Temperature Anomalies," Phys. Rev. Lett. 90, 248701 (2003).

N. Scafetta, B. J. West, "Phenomenological reconstructions of the solar signature in the Northern Hemisphere surface temperature records since 1600," J. Geophys. Res. 112, D24S03 (2007).


Anonymous said...

The authors however show that the statistics of the fluctuations are similar to the statistics for solar flares.

It's interesting that the second article in your notes begins tracking temperature after the controversy surrounding the temperature fluctuations and lack of sunspots in the late 18th, early 19 centuries.

I cannot access the first article and am curious if it mentioned anything about the "Maunder Minimum"?

Lawrence Gage said...

Hi Jennifer,

Shows how poorly informed about this issue I am, but I hadn't heard of the Maunder Minimum. I've now read up a little about it and it is certainly a suggestive occurrence. Thanks for bringing it up.

To answer your question, the two-page article does not mention the Minimum.