Global Warming to Slow Down, Then Speed Up Again

The pace of global warming may slow down over the next few years, before speeding up again, a new study says.

The results of the study, detailed in the Aug. 10 issue of the journal Science, are based on a modified climate model that better predicts potential climate change on shorter time scales, the authors say.

"It's really aimed at the coming 10 years, whereas previous projections are aimed at the coming century or so," said lead researcher Doug Smith of the U.K. Met Office.

Unlike most models, Smith's model predicts changes in the internal variation of Earth's climate (from phenomena such as El Niño), in addition to the outside forcings to the climate from greenhouse gases, aerosols and solar radiation.

Models predicting what could happen by 2100—as most models do, including those used in Intergovernmental Panel on Climate Change (IPCC) estimates—don't need to directly predict internal variability. While they do still include internal variations in Earth's climate system, the global warming signal tends to overwhelm any effects of natural variability when forecasting out so far.

"By a hundred years' time, the global warming will be much greater than any sort of internal variability," Smith explained. "But in the coming 10 years, the internal variability and global warming could be comparable, especially regionally."

To test whether the modifications improved short-term projections, Smith and his team ran the model from starting points in the 1980s and 1990s and found that the model did "improve the skill of the forecast," Smith told LiveScience.

Decade-scale and more regional projections are important to planners and businesses who are trying to prepare for the effects of climate change.

"There's a lot of people interested in the coming 10 years," Smith said. "We can improve our forecasts on the sort of 10-year period, so we can give information that's likely to be very useful for planners and businesses to adapt to climate change."

The model's projections, which were run starting from June 2005, have been on-track so far, predicting that internal variations will offset some of the globe's overall warming.

But that doesn't change the ultimate outcome of global warming, Smith said. According to the model results, at least half of the years after 2009 will be warmer than 1998, the warmest year on record.

"Climate change is still going to happen, it's still going to warm over the coming century," Smith said. "By the end of the coming 10 years it's still going to have warmed up substantially."