Because of the complexity of the Earth system, most forecasts of climate change are long-range predictions. External forcing becomes dominant over the long term (decades to centuries), but in the near term natural signals such as El Nino play a larger role. Now a new method which includes the initial state of the ocean and atmosphere and accounts for this natural variability provides improved near term forecasts:
When called on to forecast the coming decade, [the Decadal Climate Prediction System] produced a 10-year temperature curve distinctly different from those predicted by conventional models. The curve is based on 20 different model runs starting on 20 different days in 2005, each with its own set of initial conditions.
If the model is correct, in the next few years natural variability — mainly in factors affecting the heat content of the ocean — will offset some of the climate warming resulting from humanity's greenhouse emissions. But global warming will be taking only a brief breather: [at least] half the years from 2009 to 2014 will be warmer than 1998, which is currently the warmest year on record.
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