June 2023 didn’t seem like an exceptional month at the time. It was the warmest June on record, but monthly records are not at all unusual in a period in which the top 10 warmest years on record have all occurred in the past 15 years. And monthly records tend to occur in otherwise unexceptional years. At the time, the warmest July on record occurred in 2019, a year that was relatively unremarkable compared to other years in the past decade.
However, in July 2023, the monthly record for maximum temperature was broken, easily surpassing the record set in 2019. Then, in August, the monthly record for maximum temperature was broken again. And every month since then, records have been broken, making 2023 the warmest year since records began.
On Wednesday, the European Union’s Earth observation service Copernicus Announced We’ve now come to the end of a year in which every month has been its warmest since there have been enough instruments in place to track global temperatures.
As the graph shows, most years have a wide range of temperatures, with some months above average and some below average. Exceptionally warm months tend to be concentrated over a shorter period than one year.
A similar one-year record-breaking event occurred once in 2015 and 2016, according to the Copernicus data. NASA uses slightly different data and methodology, but has not seen a similar record-breaking event in any previous period. NASA has not yet released its May temperature results (they are expected to do so within the next few days), but those results are likely to also show a one-year record.
Beyond the records, the EU highlighted the fact that temperatures in the year to May were 1.63°C warmer than the 1850-1900 average, which is used as the benchmark for pre-industrial temperatures. This is notable because many countries have ostensibly committed to striving to keep temperatures no higher than 1.5°C above pre-industrial levels by the end of the century. While it’s likely that temperatures will fall below that target again within the next few years, the new records suggest that there is an extremely limited time before temperatures will consistently exceed the target.