Dr. James E. Hansen used current theories based on greenhouse gases, changes in solar, volcanic, ozone, land use and aerosol concentrations to create temperature reconstruction of the last 130 years.  Hansen's model is shown below as the black line.  The blue line with stars is the actual temperature data we have.  As you can see the model reflects the observed temperature data very well.  This is very strong proof that the models do in fact work.  What is especially striking is the fact that the models "are not statistical, but are physical in nature."  Statistical models use training data to find correlations.  For example a batting average in baseball is based off of ones batting history.  This can be used as a statistical model to predict the future.  A physical model of a player at bat would likely use equations based on the velocity of the baseball, force of the swing, etc and ignore the players batting history.  The climate models used by the IPCC and NASA are not statistical models.  NASA's climate models make their predictions based off of the laws of physics.  Since the models are based off of physics comparing them to the past is almost as good as testing them with predictions of the future.  Another advantage of physical models over statistical models is best described by physicist Ulf Bossel: "the laws of physics are eternal and cannot be changed with additional research, venture capital or majority votes."  There may be gaps in our knowledge but once a mechanism is understood the physics used to describe that mechanism is not going to change.

Fig 1. Source: Hansen et al. 2005 doi:10.1126/science.1110252.

Past Attempts of Climate Models to Predict the Future
        On June 23, 1988 James Hansen testified in front of congress on global warming.   Hansen said he could state "with 99% confidence" that a long-term warming trend was underway, and he strongly suspected that the greenhouse effect was to blame. He provided the following graph as part of his Congressional testimony on global warming. (Figure 2)   So fast forwarding 20 years later Hansen releases an updated version of his graph in the proceedings of the National Academy of Sciences "Global temperature change".  (Figure 3) Again his models are very accurate.   Professor Rabett has the full analysis on his blog entry titled Well lookee that....

Hansen's Original 1988 Graph of Predictions	Hansen's 2006 Graph Confirming 1988 Predictions
Fig 2. Hansen and Lebedeff, 1988	Fig 3. Source: PNAS, Hansen et al. 103 (39): 14288. (2006)

        If you are wondering why there is a dip in temperatures after 1991 it's because that is the year Mount Pinatubo erupted.  The ash tends to block light and cool the earth.  The models do account for volcanic eruptions.  However, it's simply impossible to predict the exact time and date these events will occur.  Unless you are an expert you won't have the background to understand why one year is slightly off and the next year is lined up with the models.  This is why it's important to view the general trend and not any specific year.  And as you can see the overall trend is a very good match.  



In 1998 NASA's James Hansen updated his 1988 graph.  The temperature measurements are in red.  Hansen's predictions were very accurate.   The growth rate of greenhouse gases in the period 1988-1998 has been relatively linear, very similar to scenarios B and C (which are nearly the same until year 2000).1  However, when Pat Michaels testified in front of Congress he erased scenarios B and C of Hansen's graph.  Climate blogger Coby Beck claims Pat Michaels "lied by omission".  Professor Tim Lambert prefers to use stronger words "fraud, pure and simple" on his blog.  Nobody can know with absolute certainty what is going on in anyone's mind.  However, the facts are that Pat Michaels not only erased what Hansen stated would be the most likely scenario, but he had also erased the two most accurate scenarios.  This is where the controversy of Hansen's "inaccurate" models started.

Hansen's Graph Updated	Pat Michaels Portrayal of Hansen's graph.
Fig 4. Hansen et al, 1998	Fig 5. Pat Michaels testimony

Most notable is that the models have not only correctly predicted temperature trends but they've predicted how the earth will change.  The following is a list of successful predictions made by the models:

• Models predict that surface warming should be accompanied by cooling of the stratosphere, and this has indeed been observed;
• Models have long predicted warming of the lower, mid, and upper troposphere.  For a while satellite readings seemed to disagree but it turns out the satellite analysis was full of errors due to changing orbit (gravity pulling on satellite), sensor issues, etc and on correction, this warming has been observed;
• Mears et al, Santer et al and Sherwood et al show that the discrepancy has been mostly resolved, in favor of the models.
• Models predict warming of ocean surface waters, as is now observed.
• Models have successfully reconstructed ocean heat content. (Fig 6)

705m heat content Reconstructed

Fig 6 Source: Hansen et al. 2005 doi:10.1126/science.1110252.

• Models predict an energy imbalance between incoming sunlight and outgoing infrared radiation, which has been detected;
• Models predict sharp and short-lived cooling of a few tenths of a degree in the event of large volcanic eruptions, and Mount Pinatubo confirmed this; (Figure 7)
• Models predict an amplification of warming trends in the Arctic region, and this is indeed happening;  (Figure 8)

Mount Pinatubo Eruption	Observed Arctic Polar Amplification
Fig 7 relevant info:: Hansen et al. 2005 doi:10.1126/science.1110252.	Heating of the North Pole but not the South Pole for the next 100 years was correctly predicted by the models. Fig 8 Source: NASA 2005 GISS Surface Temp Trends

• Models predict continuing and accelerating warming of the surface, and as you can see from figures 2 & 3, they have had a very good track record.

The models have had a very good track record since 1988.  They also strongly indicate that the recent warming is not natural.  Despite this, some skeptics and denialists continue to attack their credibility.








More info:

• IPCC TAR: Comparison of Natural and Model Forcings
• Real Climate: Meteors, Nuclear Tests and Global Warming
• Real Climate: Inhofe and Crichton: Together at Last!
• Real Climate:No man is an (Urban Heat) Island, 2 Jul 2007
• Deltoid: Pat Michaels: "fraud, pure and simple"
• Deltoid: Climate Fraudit
• Cato: STATEMENT of Patrick J. Michaels on the Kyoto Protocol
• Junkscience: Kyoto Protocol: A useless appendage to an irrelevant treaty
• Exxonsecrets:  FACTSHEET: Patrick J. Michaels
• NASA: Hansen, et al. 1998,  A common-sense climate index: Is climate changing noticeably?
• NASA: The Global Warming Debate
• Hansen et. al, Earth's energy imbalance: Confirmation and implications. Science, 308, 1431-1435, doi:10.1126/science.1110252.
• NASA: Hansen et al. 2007, Dangerous human-made interference with climate: a GISS modelE study
• NASA: Hansen: The Global Warming Debate
• NASA: Hansen: Climate forcings in the Industrial era
• Proceedings of the National Academy of Sciences, Hansen et al. 103 (39): 14288. (2006)
• Proceedings of the National Academy of Sciences, Santer, et al, Forced and unforced ocean temperature changes in Atlantic and Pacific tropical cyclogenesis regions., September 19, 2006, vol. 103, no. 38, 13905-13910
• Prometheus: Evaluating Jim Hansen’s 1988 Climate Forecast
• Rabett Run: Business as usual in 1988
• Rabett Run: Scenerio A B and C
• Rabett Run: As Mr Dooley says, trust everyone, but cut the cards....
• Rabett Run:  RTFR (I)
• Rabett Run:  Man bites dog......
• Rabett Run: Continuing our series.....
• Rabett Run: Well lookee that....
• Gristmill: How to Talk to a Climate Skeptic, 'Climate Models Are Unproven' Coby Beck

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