Global warming forecast predicts rise in 2014

Here is the climate forecast for the next decade; although global warming will be held in check for a few years, it will come roaring back to send the mercury rising before 2014.

The overall trend in warming is driven by greenhouse gas emissions
Overall warming trend is driven by greenhouse gas emissions

This is the prediction of the first computer model of the global climate designed to make forecasts over a timescale of around a decade, developed by scientists at the Met Office.

The new model developed at the Met's Hadley Centre in Exeter, and described in the journal Science, predicts that warming will slow during the next few years but then speed up again, and that at least half of the years after 2009 will be warmer than 1998, the warmest year on record.

Over the 10-year period as a whole, climate continues to warm and 2014 is likely to be 0.3 deg C warmer than 2004.

The overall trend in warming is driven by greenhouse gas emissions but this warming effect will be broadly cancelled out over the next few years by the changing patterns of the ocean temperatures.






Earlier computer models attempted to make projections up to 100 years into the future and to do this only needed approximate information on the current state of the Earth's atmosphere and oceans, since the biggest effect comes from global warming. But their predictions were relatively uncertain over around a decade.

The new model developed by a team led by Dr Doug Smith can make these shorter term predictions significantly more accurately because it incorporates information about the actual state of the ocean and the atmosphere today, so it is possible to predict both the effects of natural factors, such as changes in ocean circulation, and those caused by burning fossil fuels.

The resulting improved climate forecasting should help decision-makers and businesses focus on where and when the most severe climate change will be happening and might provide new insights into pressing issues, such as the impact of warming on hurricanes.

As a bonus, the model could help show when the looming threat of global warming will be masked temporarily by the natural variability of the climate.

The team can be confident in its work because they tested it on past cases- hindcasts - over two previous decades it provides a more accurate predictions of global surface temperature The model successfully predicted the warming of El Niño, for example, and the effect of unusually warm or cold waters around the world.

A common criticism of conventional computer models, particularly for predicting the coming decade, has been that they only include factors, such as solar radiation, atmospheric aerosols and greenhouse gases, which are affected by changes from outside the climate system, such as the number of cars or processes in the Sun.

Likewise, they neglect natural changes within the system, like the ocean warming called El Niño, fluctuations in ocean circulation and anomalies in ocean heat content.

These lead to changes over a year to a decade, especially at the regional level, that can be opposition to those expected over the next century resulting from human activities. One example is a pattern in the variations of ocean warming, called the Atlantic Multidecadal Oscillation, which can affect climate worldwide.

The new model incorporates the effects of sea surface temperatures as well as other factors such as man-made emissions of greenhouse gases, projected changes in the Sun's output and the effects of previous volcanic eruptions - the first time internal and external variability have both been predicted.

"This is a very valuable step forward," Science was told by meteorologist Rowan Sutton of the University of Reading. "It's precisely on the decadal time scale and on regional scales that natural variability and anthropogenic (man made) effects have comparable magnitudes."

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