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Politics : Politics of Energy -- Ignore unavailable to you. Want to Upgrade?

To: Hawkmoon who wrote (36365)

12/10/2012 12:33:44 PM

From: Wharf Rat

Read Replies (2) | Respond to of 86356

"It certainly applies to the extremely dire predictions of James Hansen in 1988 when he started this AGW debate."

AGW debate began in 1897, IIRC. First president to discuss the issue was Nixon.

That's cuz you don't know what Hansen really said. You only know what some people wanted him to say. Like everybody else, he's a bit conservative. Underestimated it in '81.

Hansen's 1988 prediction was wrong
'On June 23, 1988, NASA scientist James Hansen testified before the House of Representatives that there was a strong "cause and effect relationship" between observed temperatures and human emissions into the atmosphere. At that time, Hansen also produced a model of the future behavior of the globe’s temperature, which he had turned into a video movie that was heavily shopped in Congress. That model predicted that global temperature between 1988 and 1997 would rise by 0.45°C (Figure 1). Ground-based temperatures from the IPCC show a rise of 0.11°C, or more than four times less than Hansen predicted. The forecast made in 1988 was an astounding failure, and IPCC’s 1990 statement about the realistic nature of these projections was simply wrong.' ( Pat Michaels)

What the science says...

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Although Hansen's projected global temperature increase has been higher than the actual global warming, this is because his climate model used a high climate sensitivity parameter. Had he used the currently accepted value of approximately 3°C warming for a doubling of atmospheric CO2, Hansen would have correctly projected the ensuing global warming.

Hansen et al. (1988) used a global climate model to simulate the impact of variations in atmospheric greenhouse gases and aerosols on the global climate. Unable to predict future human greenhouse gas emissions or model every single possibility, Hansen chose 3 scenarios to model. Scenario A assumed continued exponential greenhouse gas growth. Scenario B assumed a reduced linear rate of growth, and Scenario C assumed a rapid decline in greenhouse gas emissions around the year 2000.

Misrepresentations of Hansen's Projections The 'Hansen was wrong' myth originated from testimony by scientist Pat Michaels before US House of Representatives in which he claimed "Ground-based temperatures from the IPCC show a rise of 0.11°C, or more than four times less than Hansen predicted....The forecast made in 1988 was an astounding failure."

This is an astonishingly false statement to make, particularly before the US Congress. It was also reproduced in Michael Crichton's science fiction novel State of Fear, which featured a scientist claiming that Hansen's 1988 projections were "overestimated by 300 percent." Moreover, Michaels has continued to defend this indefensible distortion.

Compare the figure Michaels produced to make this claim (Figure 1) to the corresponding figure taken directly out of Hansen's 1988 study (Figure 2).

Figure 1: Pat Michaels' presentation of Hansen's projections before US Congress

Figure 2: Projected global surface air temperature changes in Scenarios A, B, and C ( Hansen 1988)

Notice that Michaels erased Hansen's Scenarios B and C despite the fact that as discussed above, Scenario A assumed continued exponential greenhouse gas growth, which did not occur. In other words, to support the claim that Hansen's projections were "an astounding failure," Michaels only showed the projection which was based on the emissions scenario which was furthest from reality.

skepticalscience.com

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The linear warming trends from 1981 through 2011 are approximtely 0.17°C per decade for Hansen’s Fast Growth scenario, 0.13°C per decade for the Slow Growth scenario, vs. 0.17°C per decade for the observed global surface temperature from GISTEMP. Estimating that the actual energy growth and greenhouse gas emissions have fallen between the Fast and Slow Growth scenarios, the observed temperature change has been approximately 15% faster than the projections of the Hansen et al. model.