May 14, 2008
Lucia Liljegren on Real Climate's Approach to Falsification of IPCC Predictions
Posted to Author: Pielke Jr., R. | Climate Change | Prediction and Forecasting | Scientific Assessments
Lucia Liljegren has wonderfully clear post up which explains issues of consistency and inconsistency between models and observations using a simple analogy based on predicting the heights of Swedes.
I think a simple example using heights is helps me explain the answer to these questions:
Please go to her site and read the entire post.
She concludes her discussion as follows:
The IPCC projections remain falsified. Comparison to data suggest they are biased. The statistical tests accounts for the actual weather noise in data on earth.Posted on May 14, 2008 02:06 PM
When you also take into account that the CO2 emissions have been above scenario A1, the Constant scenario should no longer be considered. The lower error bar should have a definitely positive slope. Estimating from Figure 4 graph from Lucia's post, I estimate that lower error bar should be 1 degree over 60 years or 0.167 C per decade. The mean for the models then would be well above 0.2 C per decade.
John M Reynolds
Posted by: jmrsudbury at May 14, 2008 09:05 PM
Yes, why would we use scenarios that don't have the emissions correct? What would that prove?
Posted by: Lupo at May 15, 2008 02:18 PM
Sly point Lupo.
Including the lesser emission scenarios proves one of, or a combination of, three things:
John M Reynolds
Posted by: jmrsudbury at May 15, 2008 07:54 PM
Yes John, I have the same conclusions that scenarios with incorrect emissions is an embarassment to notions anything other than sun and water run the weather the weather patterns and the climate. But when you guess and guess and guess a lot so you can get a wide enough range of data to prove anything you should expect to be wrong a lot individuallly and especially with your far out guesses, don't you think?
Posted by: Lupo at May 16, 2008 02:16 PM
This discussion of how one or another emissions trajectory influences results neglects one critical factor: emissions have no direct impact on radiative forcing. It is the atmospheric concentration, i.e. emissions less uptake integrated over time, that matters.
Take a really simple model of the carbon cycle (from Nordhaus' original DICE model):
Thus, regardless of what one thinks about recent temperature, short term deviations in the CO2 emissions trajectory have little effect on the outcome. If some anthropogenic forcing matters, it would have to be one of the short term ones like aerosols.
Posted by: Tom Fiddaman at May 19, 2008 02:54 PM
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