Aviation weather patterns change dramatically in the 21st century

We calibrated the observed AMOC decline to be 3 ± 1 Sv (around 15%) since the mid-twentieth century, and reconstructed the evolution of the AMOC for the period 1870–2016. […] Our findings show that in recent years the AMOC appears to have reached a new record low, consistent with the record-low annual SST in the subpolar Atlantic (since observations began in 1880) reported by the National Oceanic and Atmospheric Administration for 2015. Surface temperature proxy data for the subpolar Atlantic suggest that “the AMOC weakness after 1975 is an unprecedented event in the past millennium”. This is consistent with the coral nitrogen-15 data that led Sherwood et al. to conclude that “the persistence of the warm, nutrient-rich regime since the early 1970s is largely unique in the context of the last approximately 1,800 yr”. Although long-term natural variations cannot be ruled out entirely, the AMOC decline since the 1950s is very likely to be largely anthropogenic, given that it is a feature predicted by climate models in response to rising CO2 levels. This declining trend is superimposed by shorter-term (interdecadal) natural variability. The AMOC weakening may already have an impact on weather in Europe. Cold weather in the subpolar Atlantic correlates with high summer temperatures over Europe, and the 2015 European heat wave has been linked to the record ‘cold blob’ in the Atlantic that year.

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