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Vincent Gray Says:
22 December 2007 at 8:52 PM
This argument is not about a PREDICTION. It is about a a SIMULATION. There is so much variability between models and between data collections that it is not surprising that some madels can be found which simulate some data.
This does not prove the correctness of the models because of the well-known (but little accepted) maxim that a correlation, however convincing does not prove cause and effect.
No model has ever convincingly predicted future climate. Global temperatures, however measured, have been relatively unchanged for some eight years, in violation of all model PROJECTIONS. Until models can be shown to be successful in prediction, why should anybody believe in them?
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Hank Roberts Says:
22 December 2007 at 10:43 PM
But, Vincent, can you cite any source to support any of what you write above? I can understand you saying you believe it. But I’ll be surprised if you can show anyone else has published research supporting what you believe. Please provide your evidence that my hypothesis about this is wrong by giving cites — that’s how science works, after all.
Hansen’s Scenario C looks very good so far, after 20 years.
http://www.realclimate.org/index.php/archives/2007/05/hansens-1988-projections/
Eight years is insufficient data to reliably demonstrate a trend (or lack of one) against the noise level in climate. Didn’t I find this for you earlier? Has someone told you different? Who? Where?
William Connolley gives you the information to be appropriately skeptical about what people tell you, and points out how you can download the data set and do your own statistics to test what you’re being told and shows you what you will get using standard tests of significance on one sample data set, and comments:
“15 year trends are pretty well all sig and all about the same; that about 1/2 the 10 year trends are sig; and that very few of the 5 year trends are sig. From which the motto is: 5 year trends are not useful with this level of natural variability. They tell you nothing about the long-term change.”
http://scienceblogs.com/stoat/2007/05/the_significance_of_5_year_tre.php#
So, even Hansen’s 20 year old model has been quite good at predicting (and over a long enough period of years for the trends to be statistically interesting). Does having a factual basis to believe this change what you believe? Do facts make a difference?
# Barton Paul Levenson Says:
23 December 2007 at 7:12 AM
Dr. Gray writes:
[[No model has ever convincingly predicted future climate. Global temperatures, however measured, have been relatively unchanged for some eight years, in violation of all model PROJECTIONS. Until models can be shown to be successful in prediction, why should anybody believe in them?]]
Climate models successfully predicted that the climate would warm, that the stratosphere would cool, that the poles would warm more than the equator, that nights would warm more than days, and they predicted quantitatively how much the Earth would cool after the eruption of Mount Pinatubo. What else do you want?