The temperatures a country, state, or any particular area experience over many decadestend towards a bell curve probability distribution, such that the mean value is the center of the distribution, and the range of values experienced can be quantified by the standard deviation, or sigma, around the mean value. This is how a temperature climatology is typically defined. Global warming is the documented increase in the temperature averaged over the entire planet, due primarily to the increase in greenhouse gas concentration, but global warming also suggests that the climatology of any given region has changed over time. In order to assess the change in climatology across any region in time, I defined a climatological base period of 1951-1980 and calculated the frequency of observed local monthly standardized temperature anomalies above +2 and +3, or 2-sigma and 3-sigma events, using the NOAAv5 Global Land and Ocean Temperature Anomaly dataset from 1880 to 2020. From 1980 to 2020, the frequency of 2-sigma and 3-sigma events increased exponentially across all seasons for both ocean and land. In the most recent decade (2010-2020), 2-sigma events occurred 12-20 times statistical expectation, while 3-sigma events occurred 83-222 times expectation. The increase was largest in Summer (JJA), as well as over the ocean. By definition, a climatology suggests that hot extremes rarely occur in any particular region, but my results show that hot extremes are now far more common in every season and across most regions of the world.
