This paper examines the trends in the Southern Hemisphere Annular Mode (SAM) using both observational data and reanalyses. The SAM is the dominant mode of atmospheric variability in the Southern Hemisphere, and recent studies have reported a significant trend toward its positive phase. However, the National Centers for Environmental Prediction–National Center for Atmospheric Research (NNR) reanalysis data are known to have spurious negative trends in high southern latitude pressure, which could invalidate findings on SAM changes. To address this, the study uses station data to calculate a proxy zonal mean sea level pressure (MSLP) at 40° and 65°S, revealing a statistically significant increase in the difference between these pressures since the mid-1970s. The NNR data exaggerate these trends by factors of 3 and 2, respectively, due to errors in high southern latitude pressures. The European Centre for Medium-Range Weather Forecasts (ECMWF) reanalyses, particularly ERA-40, provide a more accurate representation of high southern latitude atmospheric circulation variability and are ideal for examining recent SAM trends. The study concludes that the SAM has indeed increased since the mid-1960s, with the trend being most pronounced since the mid-1970s. The NNR data overestimate the SAM trend by a factor of 2, while the ECMWF reanalyses provide a more reliable benchmark for future climate scenarios. The study highlights the importance of using accurate reanalysis data to assess climate change trends in the Southern Hemisphere.This paper examines the trends in the Southern Hemisphere Annular Mode (SAM) using both observational data and reanalyses. The SAM is the dominant mode of atmospheric variability in the Southern Hemisphere, and recent studies have reported a significant trend toward its positive phase. However, the National Centers for Environmental Prediction–National Center for Atmospheric Research (NNR) reanalysis data are known to have spurious negative trends in high southern latitude pressure, which could invalidate findings on SAM changes. To address this, the study uses station data to calculate a proxy zonal mean sea level pressure (MSLP) at 40° and 65°S, revealing a statistically significant increase in the difference between these pressures since the mid-1970s. The NNR data exaggerate these trends by factors of 3 and 2, respectively, due to errors in high southern latitude pressures. The European Centre for Medium-Range Weather Forecasts (ECMWF) reanalyses, particularly ERA-40, provide a more accurate representation of high southern latitude atmospheric circulation variability and are ideal for examining recent SAM trends. The study concludes that the SAM has indeed increased since the mid-1960s, with the trend being most pronounced since the mid-1970s. The NNR data overestimate the SAM trend by a factor of 2, while the ECMWF reanalyses provide a more reliable benchmark for future climate scenarios. The study highlights the importance of using accurate reanalysis data to assess climate change trends in the Southern Hemisphere.