New Study On The Prediction Skill Of The Multi-Decadal Global Climate Models

On May 31, 2007 there was an article in Nature by Harvey Leifert that was titled “Warmer world gets wetter – Satellite observations suggest climate models are wrong on rainfall”.

Excerpts from the article read

“Global warming will increase worldwide precipitation by three times the amount predicted by current climate models, according to a study based on two decades’ worth of satellite observations.

The discrepancy between the models and the data might mean that the models are wrong. Or it might be that two decades is not long enough to test their predictions….”

This study conflicts with the claims such as that of

Richard Seager, Mingfang Ting, Isaac Held, Yochanan Kushnir, Jian Lu, Gabriel Vecchi, Huei-Ping Huang, Nili Harnik, Ants Leetmaa, Ngar-Cheung Lau, Cuihua Li, Jennifer Velez, and Naomi Naik: Model Projections of an Imminent Transition to a More Arid Climate in Southwestern North America Published online 9 April 2007 [DOI: 10.1126/science.1139601] (in Science Express Reports)

as discussed on Climate Science (see and see).

The new study

Frank J. Wentz, Lucrezia Ricciardulli, Kyle Hilburn, and Carl Mears: How Much More Rain Will Global Warming Bring? Published online 31 May 2007 [DOI: 10.1126/science.1140746] (in Science Express Reports)

clearly shows that we have a poorer understanding of the climate system than has been communicated by assessments such as the 2007 IPCC Report.

The abstract of their paper reads

“Climate models and satellite observations both indicate the total amount of water in the atmosphere will increase substantially due to global warming at a rate of 7% K-1. However, the climate models predict global precipitation will increase at a much slower rate of 1-3% K-1. A recent analysis of satellite observations does not support this prediction of a muted response of precipitation to global warming. Rather, the observations suggest that precipitation and total atmospheric water have increased at about the same rate over the last two decades.”

Of course, this study conflicts with the findings of

Smith, T. M., X. Yin, and A. Gruber (2006), Variations in annual global precipitation (1979–2004), based on the Global Precipitation Climatology Project 2.5° analysis, Geophys. Res. Lett., 33, L06705, doi:10.1029/2005GL025393,

where they write for the period 1979–2004 that precipitation tends

“have spatial variations with both positive and negative values, with a global-average near zero.â€?

Indeed, the diversity of observational results exemplifies our large remaining uncertainty of both the models and observations.

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