September 2019



Surface air temperature anomaly for September 2019 relative to the September average for the period 1981-2010. Data source: ERA5. Credit: Copernicus Climate Change Service/ECMWF.

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Temperatures over Europe for September 2019 were above the 1981-2010 average over most of the continent, especially in the south and south-east. Below-average temperatures occurred over much of Norway and Sweden, and over the far east of the continent.

Elsewhere, temperatures over the northern hemispheric land masses were markedly above average over parts of the Arctic, over most of the USA, and over Iran, Afghanistan, Mongolia and northern China. Temperatures were likewise above average over central South America, South Africa, south-western Australia and West Antarctica.



Temperatures over land were notably below average only over south-western Russia, the Central Asian Republics and parts of Antarctica, although several other regions experienced temperatures that were slightly below average for the month.

Although regions of below-average temperature occurred over all major oceans, including the tropical eastern Pacific, marine air temperatures were predominantly higher than average, especially so over the north-eastern Pacific Ocean and over several Arctic and West Antarctic seas.



Monthly global-mean and European-mean surface air temperature anomalies relative to 1981-2010, from January 1979 to September 2019. The darker coloured bars denote the September values. Data source: ERA5. Credit: Copernicus Climate Change Service/ECMWF.

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Global temperatures were substantially above average in September 2019. The month as a whole was:

• 0.57°C warmer than the average September from 1981-2010, making it by a narrow margin the warmest September in this data record;

• 0.02°C warmer than September 2016, the second warmest September;

• 0.1°C warmer than September 2017, the third warmest September.

European-average temperature anomalies are generally larger and more variable than global anomalies, especially in winter, when they can change by several degrees from one month to the next. The European-average temperature for September 2019 was:

• 0.7°C warmer than the average September from 1981-2010;

• not remarkably warm in the context of values over the past two decades.

The last 12 months - October 2018 to September 2019



Surface air temperature anomaly for October 2018 to September 2019 relative to the average for 1981-2010. Data source: ERA5. Credit: Copernicus Climate Change Service/ECMWF

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Temperatures averaged over the twelve-month period from October 2018 to September 2019 were:

• much above the 1981-2010 average over most of the Arctic, peaking over and near Alaska and over the central parts of northern Siberia;

• above average over almost all of Europe;

• above average over most other areas of land and ocean, especially so over north-eastern China, the Middle East, south-east Asia, Australia, southern Africa and some parts of the Antarctic;

• below average over several land and oceanic areas, most notably over much of Canada and one sector of Antarctica.



Running twelve-month averages of global-mean and European-mean surface air temperature anomalies relative to 1981-2010, based on monthly values from January 1979 to September 2019. The darker coloured bars are the averages for each of the calendar years from 1979 to 2018. Data source: ERA5. Credit: Copernicus Climate Change Service/ECMWF.

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Averaging over twelve-month periods smooths out the shorter-term variations. Globally, the twelve-month period from October 2018 to September 2019 was 0.55°C warmer than the 1981-2010 average. The warmest twelve-month period was from October 2015 to September 2016, with a temperature 0.66°C above average. 2016 is the warmest calendar year on record, with a global temperature 0.63°C above that for 1981-2010. The second warmest calendar year, 2017, had a temperature 0.54°C above average, while the third warmest year, 2018, was 0.46°C above the 1981-2010 average.

0.63°C should be added to these values to relate recent global temperatures to the pre-industrial level defined in the IPCC Special Report on “Global Warming of 1.5°C”. Monthly temperatures over the past twelve months have averaged close to 1.2°C above this pre-industrial level. The September temperature is 1.2°C above the level.

The spread in the global averages from various temperature datasets has been unusually large over the past three years. During this period the twelve-month average values presented here are higher than those from several independent datasets, by between 0.05°C and 0.15°C for the twelve months for which spread is largest. This is due partly to differences in the extent to which datasets represent the relatively warm conditions that have predominated over the Arctic and the seas around Antarctica. Differences in estimates both of sea-surface temperature elsewhere and of temperatures over land outside the Arctic have been further factors. There is nevertheless general agreement between datasets regarding:

• the exceptional warmth of 2016, and the warmth also of 2015, 2017, 2018 and 2019;

• the overall average rate of warming of around 0.18°C per decade since the late 1970s;

• the sustained period of above-average temperatures from 2001 onwards.

There is more variability in average European temperatures, but values are less uncertain because observational coverage of the continent is relatively dense. Twelve-month averages for Europe were at a high level from 2014 to 2016. They then fell, but remained 0.5°C or more above the 1981-2010 average. Twelve-month averages have risen since then, but have again fallen in recent months. The latest average, for the period from October 2018 to September 2019, is 1.1°C above the 1981-2010 norm. The warmest such period, from April 2018 to March 2019, was 1.5°C above average.

The average surface air temperature analysis homepage explains more about the production and reliability of the values presented here.

