Monday, February 19, 2007

The Stern Review: A Dual Critique (Part II)
One Angry Christian

So I’m wading through this report. Here’s some of the more meaty stuff in it. I’ve broken it down into categories and the major points supporting those categories.

Climate Science is a new and immature science that has yet to be honed.

  • In its last Assessment Report, the IPCC still rated the “level of scientific understanding” of nine out of twelve identified climate forcings as “low” or “very low”,5 highlighted the limitations and short history of climate models,6 and recognised large uncertainties about how clouds react to climate forcing.7

  • None of the climate models being used take into account several factors such as solar heat increases, cosmic winds, and the effects of aerosols. They also do not account for new assertions that methane forcing maybe underestimated by half.

  • Moreover, given that the estimated temperature change over the late twentieth century amounted to only a few tenths of a degree, there must be significant doubt as to whether model simulations of external forcings are even required as an explanation. Such minor fluctuations may rather be due to natural, internal, unforced variability.

Exaggerating warming trends and more examples of bad science

  • Early in the OXONIA Technical Annex, it was said with unjustified certainty that “The rate and scale of 20th century warming has been unprecedented for at least the past 1,000 years.” While the Review backtracks somewhat,12 the claim raises the issue of context.

    • The only genuinely global records of measured temperature come from weather balloon radiosonde measurements (since 1958) and satellite microwave sounding units (since 1978). These data, for what they are worth over such short time periods, indicate a gentle warming trend of about 0.1–0.2 degrees C/decade.13

    • The trend, such as it is, is at least in part an artifact caused by irregularities such as volcanic eruptions and El Nino events,15 and anyway—prima facie—it is unalarming in both rate and magnitude.

    • Nor is there any sign of acceleration either in surface or tropospheric data, calling into question the Review’s emphasis on outcomes involving decadal trends of 0.3–0.6 degrees C. Despite the accumulation of CO2 in the Earth’s atmosphere since 1900, and especially since 1950, no global temperature databases exhibit temperature trends of such magnitude.

    • If comparison is made with the ‘global average temperature’ statistic since 1860 that is computed from near-surface thermometer measurements, 17 then the late twentieth-century warming is similar in both amount and rate to an earlier (natural) warming between 1905 and 1940.

    • the oxygen isotope (proxy air temperature) record from the Greenland GRIP drilling project shows that the late twentieth-century warming represents an intermittent high on a sinusoidal, millennial temperature pattern18 of possible solar origin.19 This record shows that recent warming occurred at a similar rate, but was of lesser magnitude, than the earlier, millennial warmings associated with the Mediaeval, Roman and Minoan warm periods.

Thus the Review’s apodictic claim that “An overwhelming body of scientific evidence indicates that the Earth’s climate is rapidly changing, predominantly as a result of increases in greenhouse gases caused by human activities”20 is without foundation.

-One Angry Christian


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