State of the climate in 2014

The key parameters which indicate the Earth's changing climate, including land and ocean temperature, sea level and greenhouse gases, have set new records in the year 2014, according to "State of the climate in 2014" – Special Supplement to the Bulletin of the American Meteorological Society released this month. These essential climate variables, carefully monitored and recorded each year, have continued to follow the long-term rising trends throughout the year. 

Four independent surface temperature observational analyses have reached a conclusion that the year 2014 was the warmest year on record. However, one needs to bear in mind a measure of uncertainty for annual rankings in the process of analyses, due to uncertainty in the underlying annual global temperature anomalies themselves. Read more about it at the end of the article.

​Global average surface temperature anomalies (1981–2010 base period). Image credit: State of the Climate in 2014 report, American Meteorological Society.

Above average warm conditions were present across the globe, land and ocean surfaces, during 2014. According to four in-situ analyses, the global average temperature was reported highest since it's recording began in the mid-to-late 1800's. The 2014 globally averaged surface temperature was between 0.27°C and 0.29°C above the average measured in the period between 1981 to 2010.  Seventeen of the eighteen warmest years on record have occurred over the last 18 years. (A. Sánchez-Lugo, P. Berrisford and C. Morice,2015: Surface Temperature[in "State of the climate in 2014"].Bull.Amer.Meteor.Soc.96(7),S9)

The major greenhouse gases, including carbon dioxide, methane and nitrous oxide have all reached high atmospheric concentrations. For example, carbon dioxide has increased by 1.9 ppm and it reached a globally averaged value of 397.2 ppm for the year 2014. These five major greenhouse gases, in combination with 15 minor ones have contributed 2.94 W/m² of direct radiative forcing, 36% greater contribution than only quarter a century ago.

Distributions of observed net longwave radiation at the surface under clear skies, ice clouds, and liquid clouds at four Arctic locations. Image credit: State of the Climate in 2014 report, American Meteorological Society.

The highest annual global surface temperature was observed in at least 135 years of modern record keeping, according to four independent observational analyses. Europe has observed it's warmest year on record, and many of it's countries broke the national temperature records. A number of Asian countries have had annual temperatures among their 10 warmest on record. The above average temperatures have been reported across most of the Africa, the third warmest year on record was measured in Australia while Mexico reported 2014 to be the warmest year on record. Argentina and Uruguay reported their second warmest year on the record, while eastern North America was the only part of the world to report below-average annual temperature.

It is highly likely that the oceans were responsible for driving the global surface temperatures. The globally averaged sea surface temperature (SST) was also highest recorded, although the year was mainly ENSO neutral.

The oceans absorb more than 90% of excess greenhouse gas forcing heat. Due to ocean warming accompanied with the land ice melt, global average sea level in 2014 was record high, 67 mm higher than measured in 1993. An increased hydrological cycle has also been observed, as reflected in salinity anomalies in the sea surface salinity (SSS) trends, where the salinity was increasing in the salty regions while fresh regions were observed to become fresher.

Precipitation over the world's oceans was above the average, while it was below across the land surfaces. Southeastern Brazil and the western U.S. reported droughts, while above-normal summer monsoon rainfall was reported over the southern coast of west Africa. Summer monsoon rainfall was above average across the eastern Africa, apart in the areas of western south Sudan and Ethiopia. The south Asian monsoon was below average, setting a record for the dry period during June.

The rainfall data are from the NOAA/TRMM analysis (Huffman et al. 2007), averaged over Jan–Mar 2014, as a percentage of the 1998–2012 average. Image credit: State of the Climate in 2014 report, American Meteorological Society.

Precipitation was quite variable across the globe. On balance, precipitation over the world’s oceans was above average, while below average across land surfaces. Drought continued in southeastern Brazil and the western United States. Heavy rain during April–June led to devastating floods in Canada’s Eastern Prairies. Above-normal summer monsoon rainfall was observed over the southern coast of West Africa, while drier conditions prevailed over the eastern Sahel. Generally, summer monsoon rainfall over eastern Africa was above normal, except in parts of western South Sudan and Ethiopia. The south Asian summer monsoon in India was below normal, with June being record dry.

91 major tropical cyclones were observed during the year 2014, which is above the global average of 82 for the 1981-2010 period.

The temperatures over the land surface in the Arctic were the fourth highest in a period of 115 years of records. The snow melt occurred about 20-30 days earlier than the 1998-2010 average during 90% of the melt season, which has contributed to lowering the average summer albedo to the second lowest recorded over Greenland since the observations began in 2000. New record high temperatures at 20 m depth were measured on the North Slope of Alaska.

Lemon Creek Glacier, Alaska, in September 2014: the area of retained snowcover is insignificant. For this glacier an equilibrium balance requires 62% snowcover. Image credit: Chris McNeil.

Arctic minimum extent of the sea ice was the sixth lowest since satellite records began in 1979, in September 2014. In the Antarctic, the sea ice extent set several new records for the year. On September 20, 2014, a record large daily Antarctic sea ice extent measuring 20.14 x 106 km² occurred.

The 2014 Antarctic stratospheric ozone hole was 20.9 million km² when averaged from September 7 to October 13, the sixth smallest on record and continuing a decrease, albeit statistically insignificant, in area since 1998. (J. Blunden and D.S. Arndt, 2015: Abstract in ["State of the climate in 2014"].Bull.Amer.Meteor.Soc.96(7),Sxiv)

Four independent surface temperature observational analyses have reached a conclusion that the year 2014 was the warmest year on record. However, one needs to bear in mind a measure of uncertainty for annual rankings in the process of analyses, due to uncertainty in the underlying annual global temperature anomalies themselves.

There is an estimated 48% probability that 2014 was the warmest year over the period between 1880 and 2014, in the NOAA record. This means that "while we cannot conclusively claim that 2014 was the warmest year in the real world when uncertainty is factored in, the 48% probability does not imply that 2014 was anything other than a very warm year, and it certainly does not cast doubt on the unprecedented warmth over the last 20 years". (A. Arguez and S. Applequist, 2015: Understanding the statistical uncertainty of 2014's designation as the warmest year on record in "State of the climate in 2014"].Bull.Amer.Meteor.Soc.96(7),S12)

Source: State of the Climate in 2014, report. American Meteorological Society.

Reference:

• Blunden, J. and D.S.Arndt, Eds., 2015: State of the Climate in 2014. Bull. Amer. Meteor. Soc.96(7),S1-S267

Featured image: Ice calving from the terminus of the Perito Moreno Glacier in western Patagonia, Argentina. Image credit: Luca Galuzzi.