June 2023 did not seem like an exceptional month at the time. It was the warmest June in the instrumental temperature record, but the monthly records haven’t exactly been unusual in a period when the 10 warmest years on record occurred in the last 15 years. And monthly records have often occurred in otherwise unexceptional years; At the time, the warmest July on record had occurred in 2019, a year that doesn’t stand out much from the rest of the past decade.
But July 2023 set another monthly record, easily eclipsing the high temperatures of 2019. Then August set another monthly record. And the same thing has happened every month since: a series of records that propelled 2023 to be the warmest year since tracking began.
On Wednesday, the European Union’s Earth monitoring service, Copernicus, Announced which has now been a full year in which each month has been the warmest version of that month since there have been enough instruments to track global temperatures.
The history of monthly temperatures shows how extreme temperatures have been over the past year.Courtesy of C3S/ECMWF
As you can see from this graph, most years feature a mix of temperatures: some higher than average, some lower. Exceptionally high months tend to cluster together, but those clusters also tend to be shorter than a full year.
In the Copernicus data, a similar streak of one-year records occurred once before, in 2015/2016. NASA, which uses slightly different data and methods, does not show a similar streak in that earlier period. NASA has not yet released its results on May temperatures (they are expected in the next few days), but it is very likely that the results will also show a year-long streak of records.
Beyond the records, the EU highlights the fact that the one-year period ending in May was 1.63 degrees Celsius above the average temperatures of the period 1850-1900, which is used as a reference point for temperatures preindustrial. This is notable because many countries have apparently committed to trying to prevent temperatures from rising above 1.5 degrees Celsius above pre-industrial conditions by the end of the century. While temperatures will likely fall below the target again at some point within the next few years, new records suggest we have a very limited amount of time before temperatures persistently exceed it.
For the first time on record, temperatures have consistently remained above 1.5 degrees Celsius above the pre-industrial average.Courtesy of C3S/ECMWF