Saturday, 5 May 2018

April set records for warm temrperatures despite cold conditions

Surface air temperature for April 2018



4 April, 2018

Surface air temperature anomaly for April 2018 relative to the April average for the period 1981-2010. Source: ERA-Interim. (Credit: ECMWF, Copernicus Climate Change Service)
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April 2018 was warmer than the 1981-2010 average over almost all of Europe. It was particularly warm over central and south-eastern parts of the continent, with Germany recording its warmest April in a record that stretches back to 1881.
Much of the Arctic Ocean and some neighbouring land areas were again substantially warmer than the 1981-2010 average. It was, however, colder than average in a band from the north-eastern coast of Greenland to Novaya Zemlya, where sea-ice cover was slightly higher than average. Temperatures were also well above average over coastal regions of Antarctica and over the Ross and Weddell Seas. Here sea-ice cover was below average.
April 2018 was Australia’s second warmest April on record. Temperatures were also unusually high over drought-affected Argentina. Other areas of markedly above-average temperature include parts of Mexico and the American Southwest and much of North Africa, China and Mongolia.
Conversely, the month was considerably colder than average over the central USA and much of Canada. A number of other land regions had temperatures that were a little below average.
Relatively cool conditions continued to prevail over the eastern tropical Pacific and much of the tropical Atlantic. It was also notably colder than average to the east of Newfoundland and to the west and southwest of Chile. Marine air temperatures were quite substantially above average over much of the northern subtropics, the South Atlantic and the South Pacific, and over the Tasman Sea. They were mainly above or close to average elsewhere.
Surface air temperature anomaly averaged for May 2017 to April 2018 relative to the average for 1981-2010
Surface air temperature anomaly averaged for May 2017 to April 2018 relative to the average for 1981-2010. Source: ERA-Interim. (Credit: ECMWF, Copernicus Climate Change Service)
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Average temperatures for the twelve-month period from May 2017 to April 2018 were:
  • most above the 1981-2010 average in the Arctic;
  • above average over much of Europe, but generally below average over the northern mainland of the continent;
  • well above average over the Middle East;
  • predominantly above average over other areas of land and ocean;
  • below average over a few land and oceanic areas, including the equatorial eastern Pacific Ocean, where La Niña conditions predominated.
Monthly global-mean and European-mean surface air temperature anomalies relative to 1981-2010, from January 1979 to April 2018. The darker coloured bars denote the April values
Monthly global-mean and European-mean surface air temperature anomalies relative to 1981-2010, from January 1979 to April 2018. The darker coloured bars denote the April values. Source: ERA-Interim. (Credit: ECMWF, Copernicus Climate Change Service)
Access to data 

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The global temperature for April 2018 was well above average. Although not as exceptional as the values for April 2016 and April 2017, it was in line with the upward trend of 0.18°C per decade seen in global temperature data from 1979 onwards. April in 2018 was:
  • close to 0.5°C warmer than the average April from 1981-2010;
  • the third warmest April on record, though only a little warmer than April 2010;
  • about 0.2°C cooler than the warmest April, which occurred in 2016.
The warmest and second-warmest instances of each month of the year occur between October 2015 and December 2017.
The largest anomalies in European-average temperatures occur in wintertime, when values can vary substantially from month to month. Following below-average European temperatures in February and March, April 2018 became, by a clear margin, the warmest April on record. The European-average anomaly is 2.4°C for April 2018; the anomalies for the month in the years 2000 and 2011, which are the second and third warmest on record, are about 1.7°C.
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 April 2018
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 April 2018. The darker coloured bars are the averages for each of the calendar years from 1979 to 2017. Source: ERA-Interim. (Credit: ECMWF, Copernicus Climate Change Service)
Access to data 

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Averaging over twelve-month periods smooths out the shorter-term variations. Globally, the twelve-month period from May 2017 to April 2018 was 0.47°C warmer than the 1981-2010 average. The warmest twelve-month period was from October 2015 to September 2016, with a temperature 0.64°C above average. 2016 is the warmest calendar year on record, with a global temperature 0.62°C above that for 1981-2010. The second warmest calendar year, 2017, had a temperature 0.53°C above average.
The spread in the global averages from various temperature datasets has been unusually large over the past two years or so. 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 of sea-surface temperature elsewhere have been a further factor. Spread is also large for the years 2005 and 2006, for which the values shown here are relatively high and expected to be reduced when production of an updated dataset has been completed. Nevertheless, there is general agreement between datasets regarding:
  • the exceptional warmth of 2016, and to a lesser extent 2017 and 2015;
  • the overall rate of warming 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 have remained 0.5°C or more above the 1981-2010 average. The average from May 2017 to April 2018 exceeded the 1981-2010 average by 0.7°C. The warmest twelve-month period occurred from July 2006 to June 2007, when the average temperature was about 1.5°C above that for 1981-2010.
The average surface air temperature analysis homepage explains more about the production and reliability of the values presented here.

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