likely to accelerate the Pacific trade winds and Walker circulation, while weakening Indian and South Atlantic subtropical highs. The next study from the same team showed that the result of those altered atmospheric patterns is a ∼30% reduction in ENSO variability and a ∼95% reduction in the frequency of extreme El Niño events. Unlike today, El Niño events become more frequent in the central rather than eastern Pacific El Niño events. At the same time, this would essentially make a La Nina state dominant across the globe, likely leading to more frequent extreme rainfall over eastern Australia and worse droughts and bushfire seasons over southwestern United States. In 2020, a study had assessed the impact of an AMOC collapse on farming and food production in Great Britain. It estimated that AMOC collapse would reverse the impact of global warming in Great Britain and cause an average temperature drop of 3.4 °C. Moreover, it would lower rainfall during the growing season by around <123mm, which would in turn reduce the land area suitable for arable farming from the 32% to 7%. The net value of British farming would decline by around £346 million per year, or over 10%. A 2021 study used a simplified modelling approach to evaluate the impact of a shutdown on the Amazon rainforest and its hypothesized dieback and transition to a savannah state in some climate change scenarios. It suggested that a shutdown would enhance rainfall over the southern Amazon due to the shift of an Intertropical Convergence Zone and thus would help to counter the dieback and potentially stabilize at least the southern part of the rainforest. Trends Reconstructions Climate reconstructions generally support the hypothesis that the AMOC is already weaker now than it was in the early 20th century. For instance, a 2010 statistical analysis found an ongoing weakening of the AMOC since the late 1930s, with an abrupt shift of a North Atlantic overturning cell around 1970. Climate scientists Michael Mann of Penn State and Stefan Rahmstorf from the Potsdam Institute for Climate Impact Research suggested that the observed cold pattern during years of temperature records is a sign that the Atlantic Ocean's Meridional overturning circulation (AMOC) may be weakening. They published their findings in 2015, and concluded that the AMOC circulation was slowing throughout the 20th century, and that the weakness it demonstrated after 1975 was unprecedented over the last millennium. They suggested