The paper quantifies the effect of atmospheric circulation changes on monthly, seasonal and annual mean surface air temperature trends in the years 1979–2018 by applying a trajectory-based method on the European Centre for Medium-Range Weather Forecasts ERA5 reanalysis data. The results suggest that circulation trends only had a minor impact on observed annual mean temperature trends in most areas. Exceptions include, for example, a decrease in annual mean warming by about 1 °C in western Siberia, and increased warming in central Europe and the Arctic Ocean. However, the effect of circulation trends on seasonal and particularly monthly temperature trends is more substantial. Subtracting the effect of circulation changes from the ERA5 temperature trends leaves residual trends with a smoother annual cycle than the original trends. These residual monthly mean temperature trends also agree better with the multi-model mean temperature trends in CMIP5 climate models than the original ERA5 trends do, with a 42% decrease in the mean square difference over the global land area.
Reference
Räisänen, J., 2021: Effect of atmospheric circulation on surface air temperature trends in years 1979–2018. Climate Dynamics, https://doi.org/10.1007/s00382-020-05590-y
The article can found here at: https://link.springer.com/article/10.1007/s00382-020-05590-y