Climate models consistent with ocean warming observations

Jun. 18, 2007

Climate models consistent with ocean warming observations

LIVERMORE, Calif. - Climate models are reliable tools that help researchers better understand the observed record of ocean warming and variability.

That's the finding of a group of Livermore scientists, who in collaboration with colleagues at Scripps Institution of Oceanography, had earlierestablished that climate models can replicate the ocean warming observed during the latter half of the 20th century, and that most of this recent warming is caused by human activities.

The observational record also shows substantial variability in ocean heat content on interannual-to-decadal time scales. The new researchby Livermore scientists demonstrates that climate models represent this variability much more realistically than previously believed.

Using 13 numerical climate models, the researchers found that the apparent discrepancies between modeled and observed variability can be explainedby accounting for changes in observational coverage and instrumentation and by including the effects of volcanic eruptions.

The research, which will appear in the June 18 early online edition of the journal Proceedings of the National Academy of Sciences ,casts doubt on recent findings that the top 700-meters of the global ocean cooled markedly from 2003-2005.

"Our analysis shows that the 2003-2005 'cooling' is largely an artifact of a systematic change in the observing system," said Krishna AchutaRao, previously of Livermore's Program for Climate Model Diagnosis and Intercomparison (PCMDI), now at the Indian Institute of TechnologyDelhi and the lead author of the paper. "The previous research was based on looking at the combined ocean temperature observations from several different instrument types, which collectively appear to have a cooling effect. But if you look at the observational instruments individually, there is no cooling."