You published an article about the Gulf Stream that highlights the most speculative and preliminary finding that was presented at the recent Rapid climate change conference (Sea change: why global warming could leave Britain feeling the cold, October 27).
Unfortunately, the information was put in a context that it was never given at the conference and that makes no scientific sense. Some climate models have suggested that as the world will warm, the Atlantic Ocean, overturning circulation (which is only a fraction of the mostly wind-driven Gulf Stream), might dramatically slow down. If that happens it will reduce the atmospheric warming in coastal areas. But in all those scenarios the ocean circulation-induced cooling will not even cancel the (global) warming. So a "new ice age" is not predicted by any model. The current consensus is a 25-30% reduction of the ocean overturning by 2100 and no detectable trend for the next 20 years.
At the conference, at least six papers were presented that showed that the "apparent" slowdown of the Atlantic Oceans overturning circulation was not consistent with a large number of other observations in the Atlantic. It is also not found in ocean models that have used all the available observations. Thus more than 95% of the scientists at the workshop concluded that we have not seen any significant change of the Atlantic circulation to date, but quite a bit of variability.
As a side point, Harry Bryden showed the short period of apparently no southward flow in the deep. But he also cautioned that there is no explanation for this, meaning that this could also be an artifact of the analysis. In no way has he presented this "oddity" an indication of something alarming.
Professor Martin Visbeck
Head of research unit in physical oceanography, Leibniz-Institut für Meereswissenschaften
Harry Bryden's paper last year in Nature claimed that "[t]he comparison suggests that the Atlantic meridional overturning circulation has slowed by about 30 percent between 1957 and 2004". This is a controversial claim. It is strange that such a decease hasn't produce any cooling effects on Europe's climate since a complete shutdown of the system has been estimated by climate models to see a 4°C drop in temperatures.