New paper finds climate computer models exaggerate global warming and don't reproduce Pacific Ocean oscillations

A paper published today in Geophysical Research Letters finds "Most [climate] models overestimate trends, whereby the models predict less warming or even cooling in the earlier decades compared to observations and too much warming in recent decades." Furthermore, the paper finds that the most influential ocean oscillation on the planet, the Pacific Decadal Oscillation (PDO), is poorly reproduced by climate models.

Note: A very simple climate model incorporating just the ocean oscillations PDO & AMO and the "sunspot integral" reproduces global temperatures with near perfect accuracy (R²=.96).

GEOPHYSICAL RESEARCH LETTERS, VOL. 39, L10701, 7 PP., 2012
doi:10.1029/2012GL051644

Evaluation of short-term climate change prediction in multi-model CMIP5 decadal hindcasts

Key Points

• CMIP5 models overestimate trend for global mean surface temperature
• The multi-model ensemble mean has better-forecast quality than single-model
• The Atlantic Multi-decadal Oscillation index is well predicted in all models

Hye-Mi Kim

School of Earth and Atmospheric Science, Georgia Institute of Technology, Atlanta, Georgia, USA

Peter J. Webster

School of Earth and Atmospheric Science, Georgia Institute of Technology, Atlanta, Georgia, USA

Judith A. Curry

School of Earth and Atmospheric Science, Georgia Institute of Technology, Atlanta, Georgia, USA

This study assesses the CMIP5 decadal hindcast/forecast simulations of seven state-of-the-art ocean-atmosphere coupled models. Each decadal prediction consists of simulations over a 10 year period each of which are initialized every five years from climate states of 1960/1961 to 2005/2006. Most of the models overestimate trends, whereby the models predict less warming or even cooling in the earlier decades compared to observations and too much warming in recent decades. All models show high prediction skill for surface temperature over the Indian, North Atlantic and western Pacific Oceans where the externally forced component and low-frequency climate variability is dominant. However, low prediction skill is found over the equatorial and North Pacific Ocean. The Atlantic Multidecadal Oscillation (AMO) index is predicted in most of the models with significant skill, while the Pacific Decadal Oscillation (PDO) index shows relatively low predictive skill. The multi-model ensemble has in general better-forecast quality than the single-model systems for global mean surface temperature, AMO and PDO.