The strength of mid-latitude storm tracks shapes weather and climate phenomena in the extra-tropics, as these storm tracks control the daily to multi-decadal variability of precipitation, temperature and winds. By the end of this century, winter mid-latitude storms are projected to intensify in the Southern Hemisphere, with large consequences over the entire extra-tropics. Therefore, it is critical to be able to accurately assess the impacts of anthropogenic emissions on these storms to improve societal preparedness for future changes. Here we show that current climate models severely underestimate the intensification in mid-latitude storm tracks in recent decades. Specifically, the intensification obtained from reanalyses has already reached the model-projected end-of-the-century intensification. The biased intensification is found to be linked to biases in the zonal flow. These results question the ability of climate models to accurately predict the future impacts of anthropogenic emissions in the Southern Hemisphere mid-latitudes.

中纬度风暴轨迹的强度决定了热带地区的天气和气候现象，因为这些风暴轨迹控制着降水、温度和风的每日到数十年的变化。到本世纪末，预计冬季中纬度风暴将在南半球加强，对整个温带地区产生重大影响。因此，能够准确评估人为排放对这些风暴的影响，以提高社会对未来变化的准备，这一点至关重要。在这里，我们表明当前的气候模型严重低估了近几十年来中纬度风暴路径的加剧。具体来说，从再分析中获得的集约化程度已经达到了模型预测的世纪末集约化程度。发现有偏差的强化与纬向流中的偏差有关。这些结果质疑气候模型准确预测南半球中纬度地区人为排放的未来影响的能力。