Contrary Thermometers

The improved temperature record will guide efforts to refine computer models of the world's climate so that the behaviour of the models more closely resembles the observed behaviour of the atmosphere.

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Current models suffer from several shortcomings.

For example, clouds are not well represented by the models. The resolution of current models is too coarse for features as small as clouds, Spencer said. Yet clouds clearly play a crucial role in climate due to their influence on humidity, precipitation and albedo (the percentage of solar energy reflected back into space as light).

"The role of clouds is still regarded as one of the biggest uncertainties in global warming predictions," Spencer said.

The ability of plants to remove carbon dioxide from the atmosphere and the role of soils have only recently been added to the models, and scientists aren't confident yet of how the models portray these factors, Spencer said.

"While we know that vegetation takes up some of the carbon dioxide we generate from burning of fossil fuels, how that sink of carbon will change in the future is still pretty uncertain," Spencer said.

Climate models are also limited by the computing power available.

"The global models would be much better if computers were much faster," Spencer said. "Instead, a lot of approximations are made to make the models simple enough to do climate simulations over the whole globe.

"Unfortunately," Spencer continued, "we know that many of the processes that are crudely represented are quite non-linear, and so have the potential to respond in unexpected ways."