Worst-case global warming predictions are the most accurate, say climate experts

A recent study indicates that if emissions follow a commonly used business-as-usual scenario, there is a 93 per cent chance that global warming will exceed 4 C by the end of this century.

Based on a “business-as-usual” scenario in which emissions continue at the same rate, present climate models range in their predictions from a 3.2 C increase in global temperatures till the end of the century to a 5.9 C increase.

The new study, published in the journal Nature, sought to resolve this situation and establish whether the upper or lower estimates are more accurate.

To do this, Dr Caldeira and his collaborator Dr Patrick Brown reasoned that the most accurate models would be the ones that were best at simulating climate patterns in the recent past. Their conclusion was that models with higher estimates were more likely to be accurate, with the most likely degree of warming 0.5 C higher than previous best estimates.

This video from the Yale School says that carbon emissions are likely to double from pre-industrial levels by about the middle of the century. The average global temperature may then be closer to 4 degrees, the video implies..

Scientists recently estimated that the time lag between a carbon dioxide emission and the maximum warming response is a decade on average. This is an important finding as it indicates that the full climate damages expected to occur in response to a CO2 emission will already be felt by the generation responsible for those emissions. Conversely, the relatively short response timescale implies that CO2 emission cuts implemented today have the potential to influence the rate of warming in the short term. Thus, their finding corroborates the notion that the rate of warming over the next decades is not inevitable, but will be determined by future CO2 emissions