No Turning Back From Climate Change

The wheels of global climate change are in motion, and there is little we can do to stop them, at least in the short-term, researchers say in the 18 March 2005 issue of the journal Science.

Though it is generally accepted that global surface temperatures will keep rising as long as atmospheric greenhouse gas levels do, that's only part of the picture. Because the ocean responds relatively slowly to climate change, it will continue to contribute to global warming and sea-level rise even if we do stabilize greenhouse-gas levels in the atmosphere.

Two studies now predict the effects of this ocean lag. Tom M. L. Wigley uses a relatively simple climate model to investigate the long-term climate warming "commitment" we have made already. He looks at how temperature and sea level are likely to be affected if the atmosphere's composition of greenhouse gases stays constant from now on. He also predicts the likely effects if greenhouse emissions stay constant, in which case carbon dioxide concentrations would continue to grow. "Avoiding these changes requires, eventually, a reduction in emissions to substantially below present levels," Wigley writes.

In a second study, Gerald Meehl and colleagues use a pair of more complex global climate models to show that if greenhouse gases had been stabilized in the year 2000, we would nonetheless be facing further global warming of about another half degree Celsius and a 320 percent increase in sea-level rise by the end of this century. Sea level could also rise even more than projected due to melting from ice sheets and glaciers, the authors say.

— Kathy Wren

18 March 2005