Temperature changes recorded over 50 years closely match projections in a computer simulation of the effects of atmospheric greenhouse gases such as carbon dioxide. Besides supporting the widely held scientific view that global warming is real, the research bolsters confidence in a computer model that projects temperatures will increase 5 to 6 degrees in some areas by the end of the century. The Scripps findings and a similar but independent study by a Princeton, N.J., laboratory that reached the same conclusion were published today in the journal Science . Oceanographer Tim P. Barnett, lead author of the Scripps paper, said a comparison of the computer model to actual measurements in the Atlantic, Pacific and Indian oceans indicates the temperature change likely is caused by greenhouse gas emissions, not natural factors. The computer model makes the link to human activity at least 95 percent certain, the Scripps team reported.
Greenhouse gases warm the planet by trapping heat from the sun in the atmosphere.
They are widely believed to threaten weather changes that could bring on crop failures and rising sea levels. Emissions blamed on human activity include carbon dioxide from burning fossil fuels, methane from energy production and waste management, nitrous oxide from motor vehicles and hydrofluorocarbons, once used in aerosol cans. Much of the evidence so far for global warming has come from atmospheric temperature readings showing an increase of about 1 degree over the last 100 years. The ocean temperature increase has been slower, averaging 0.06 degree Celsius since 1955. The change has been greater at the ocean surface, however, and could build up in the future.