Simulations underestimate air pressure changes
Current climate models are not able to reproduce the changes in air pressure that have been observed over the last few decades. However, this also means that they miss a realistic picture of the weather conditions in the northern hemisphere that are influenced by this, warns Nathan Gillett from the University of East Anglia.
Over the past few decades, air pressure over the Arctic has fallen during the winter months, while at the same time it has risen over the northern hemisphere subtropics. Researchers associate this with, among other things, the warmer European winters, increased precipitation in Scotland and lower rainfall in Spain. However, as early as 2003, Gillett and his colleagues found that current climate models do not adequately depict the effect.
Now Gillett calculated an index from the difference between the air pressure conditions north and south of the 45th degree of latitude from observation data from the winter months. He compared these values with the results of nine of the most modern climate models - with and without taking into account the human influence of greenhouse gases and sulfate aerosols. In both cases, the actual trend exceeded the simulated one.
The previous climate models are therefore able to depict the temperature changes caused by climate change reasonably realistically, but they fail when it comes to the pressure conditions and the associated changes in the North Atlantic circulation. However, since these are weather-determining for our latitudes, it would be urgently necessary to adapt the models accordingly.