Long-term Global Warming Scenarios Computed with an Efficient Coupled Climate Model



(Climatic Change 43, pp. 353-367)

We present global warming scenarios computed with an intermediate-complexity atmosphere-ocean-sea ice model which has been extensively validated for a range of past climates (e.g., the Last Glacial Maximum). Our simulations extend to the year 3000, beyond the expected peak of CO2 concentrations. The thermohaline ocean circulation declines strongly in all our scenarios over the next 50 years due to a thermal effect. Changes in the hydrological cycle determine whether the circulation recovers or collapses in the long run. Both outcomes are possible within present uncertainty limits. In case of a collapse, a substantial long-lasting cooling over the North Atlantic and a drying of Europe is simulated.

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The video shows the development of surface air temperature anomalies from 1900 up to the year 3000 for a global warming scenario involving a collapse of the Atlantic thermohaline ocean circulation. The scenario shown is the 'worst case' of a sensitivity study investigating a range of plausible changes in the water cycle as a result of global warming. In this 'worst case', a relatively large amount of freshwater due to enhanced precipitation and meltwater runoff enters the North Atlantic and shuts down convection and deep water formation around the year 2100. This leads to a cooling over the North Atlantic and parts of Europe, clearly seen in the later part of the animation.