global and regional climate in 2010
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Global and regional climate in 2010John Kennedy, Colin Morice and David ParkerMet Office, Exeter
Global climateThe global average temperature near the surface of the earth calculated from the third version of the Hadley Centre and Climatic Research Unit’s (HadCRUT3) (Brohan et al., 2006) data set in 2010 was 0.50 ± 0.09 degC above the 1961–1990 aver-age (Figure 1(a)). 2010 is nominally the sec-ond warmest year in HadCRUT3, but the uncertainties are such that it is statistically
indistinguishable from any of the seven warmest years.
The largest component of the uncertainty in recent years arises from large areas of missing data at high latitudes where there are few observing stations. The National Climate Data Center (NCDC) and the National Aeronautics and Space Administration’s Goddard Institute for Space Studies (NASA GISS) data sets estimate temperature anom-alies in these regions, with GISS extrapolat-ing temperatures the most extensively. The Arctic has warmed much faster than the rest of the globe and so GISS has reported higher global average temperatures than NCDC and HadCRUT3 in recent years. The
analyses produced by NASA GISS (Hansen et al., 2010) and NCDC (Smith et al., 2008) rank 2010 as the joint warmest year.
The warmth of 2010 was due in part to the El Niño that developed in 2009: El Niño events normally lead to a rise in global aver-age temperature. The effects of El Niño on global temperature typically lag tempera-ture changes in the tropical Pacific (Figure 2) by a few months (Trenberth et al., 2002). The recent El Niño reached its peak strength in December 2009 with an average sea-surface temperature anomaly in the Niño 3 region (150°–90°W, 5°S–5°N, Figure 2) of around +1.5 degC. There was a rapid transition from El Niño to La Niña conditions in 2010 and
Figure 1. (a)–(c) Annual combined land-surface air and sea-surface temperature anomalies (degC, blue bars) and uncertainty range for 1850–2010. (a) Globe, (b) Northern Hemisphere, (c) Southern Hemisphere. The red line shows the annual values after smoothing with a 21-point binomial filter and highlights interdecadal variations. Data are an update of Brohan et al. (2006). (d)–(f): as for (a)–(c) but for the (d) Tropics 20°N–20°S, (e) Northern Hemisphere north of 20°N, (f ) Southern Hemisphere south of 20°S.
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sea-surface temperature anomalies in the Niño regions fell to typically −1 degC by late 2010. Although sea-surface temperatures were not unusual compared to previous La Niña events, related indicators such as surface pressure gradients and cloudiness suggested that this was an unusually strong La Niña.
Compared with the 1961–1900 averages for all regions, the near-surface positive temperature anomaly averaged over the northern hemisphere was 0.70 ± 0.10 degC (Figure 1(b)), making 2010 one of the six warmest years on record; for the southern hemisphere, it was 0.30 ± 0.13 degC (Figure 1(c)), so that 2010 was one of the
twelve warmest years, and in the tropics (20°S–20°N) it was 0.52 ± 0.02 degC (Fig-ure 1(d)): 2010 was the joint second warmest year on record in this region, with 1998 warmer with an anomaly of 0.62 ± 0.02 degC. Uncertainties in tropical average tempera-tures are typically smaller than for the hemi-spheres and globe because temperature anomalies are geographically more coher-ent in the tropics and the anomaly for a single station is representative of a much wider area.
Figures 3 and 4 show near-surface tem-perature anomalies and percentiles for 2010. There was widespread warmth throughout the tropics from Brazil east to
the western Pacific warm pool. Temperatures over most of the north Atlantic were mark-edly above average, continuing a pattern that began in the mid 1990s. These high sea-surface temperatures are partly a mani-festation of the positive phase of the Atlantic Multi-decadal Oscillation (AMO). The AMO has been shown to influence rain-fall in northeast Brazil and the African Sahel, Atlantic hurricane formation, and North American and European summer climate (Knight et al., 2006).
During the 2009–2010 northern winter (December 2009 to February 2010, Figure 5), extreme warmth – temperatures above the 98th percentile of the 1961–1990 distribu-tion – was experienced in large areas of the tropics in response to El Niño. Although temperatures in northern Europe were lower than average, they were not extreme in comparison with the 1961–1990 climatol-ogy period, due partly to the warmer than average sea-surface temperatures in the neighbouring seas. Abnormal cold - tem-peratures below the 2nd percentile of the 1961–1990 distribution – was experienced in central Russia and in the southern USA. The general pattern of northern hemisphere temperatures was typical of the negative phase of the Arctic Oscillation characterized by above average pressure over the North Pole and below average pressure at lower latitudes. The related winter North Atlantic Oscillation index was the most negative it has been in a record extending back more than 100 years (Figure 6).
In March to May 2010, notable warmth was again observed in much of the tropics, with unprecedented sea-surface tempera-tures in many grid boxes in the tropical Atlantic. Mongolia and Northern China were exceptionally cold; eastern Canada and mid-latitude North Atlantic were unusually warm.
Temperatures for June to August 2010 were much above the 1961–1990 average in western Russia (where several grid boxes showed their highest recorded summer average temperatures), eastern Europe and parts of the Middle East. The eastern US, eastern Asia and Indonesia were also unusu-ally warm. Abnormally high sea-surface temperatures persisted in the tropical Atlantic, whilst unusually low sea-surface temperatures were observed off the west coast of the USA.
In September to November 2010, unusual warmth was observed in the Middle East, central Asia, east Africa and in the western Pacific. Abnormal cold affected central Australia and the central and eastern Pacific.
Figure 7 shows series and trends in lower troposphere and lower stratosphere tem-peratures since 1958 (radiosonde era) and since 1978 (satellite era). For reference, these are compared with surface temp erature trends and they illustrate the uncertainty
Figure 2. Three-month (January to March, April to June, July to September and October to December) average sea-surface temperatures from 1953 to February 2011 (2010 and 2011 are highlighted in green) for four regions in the Tropical Pacific: Niño 1 + 2 (80°–90°W, 0°–10°S), Niño 3 (90°–150°W, 5°S–5°N), Niño 3.4 (170°W–120°W, 5°S–5°N) and Niño 4 (160°E–150°W, 5°S–5°N). Data are an update of Rayner et al. (2006).
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Figure 3. Land-surface air and sea-surface temperature anomalies (degC, relative to 1961–1990) for 2010. The value for each 5º latitude × 5º longitude pixel is derived by averaging at least one month’s anomaly. Data are from Brohan et al. (2006).
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arising from imperfections in observing systems and analysis techniques. The fluc-tuations in global surface temperature associated with El Niño and La Niña are amplified in the troposphere. This tropo-
spheric amplification is expected to be larg-est in the tropics and, although it is seen at short time-scales, its apparent absence over longer periods is a source of enduring controversy (Thorne et al., 2010).
Regional and local climateIn Europe, 2010 was the coldest year since 1996 with an annual average temperature anomaly of +0.24 ± 0.13 degC (Figure 8); in the UK and Central England regions it was the coldest year since 1986 with anomalies of −0.4 degC and −0.6 ± 0.1 degC respec-tively. In both the Central England Temperature (CET) and UK series, January, February, November and December were all a degree or more below the 1961–1990 average (Table 1).
During the winter of 2009–2010, cold conditions (Figures 5 and 9) caused a great deal of disruption across northern Europe and Russia. The cold period coin-cided with a record negative winter North Atlantic Oscillation (NAO) index (Figure 6). The NAO index is an indicator of the strength of westerly winds blowing off the warm Atlantic: when the NAO is negative, westerly winds are weaker and cold east-erly winds become more common. The daily NAO index turned negative in mid-December 2009 and remained below aver-age for the rest of the winter except for a spell in mid-January. Although northern Europe experienced a cold winter, tem-peratures in southern Europe were above average.
Figure 4. As Figure 3 but expressed as percentiles of the 1961–1990 distribution of annual temperatures calculated by the method of Horton et al. (2001). Crosses indicate that 2010 was the warmest year on record in that 5° pixel, dashes that 2010 was the coldest. In some pixels there are too few data for 1961–1990 for the calculation of accurate percentiles; as a result there are more missing data points in Figure 3 than in Figure 4.
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Figure 5. Land-surface air and sea- surface temperature anomalies (degC, relative to 1961–1990) for December 2009 to February 2010, March to May 2010, June to August 2010 and September to November 2010. Data are an update of Brohan et al. (2006). The crosses and dashes show the extreme anomalies expressed as percentiles of the 1961–1990 distribution of seasonal temperatures calculated by the method of Horton et al. (2001).
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Because of the associated lapse in west-erlies, the negative phase of the NAO is typi-cally accompanied by drier-than-average conditions, particularly in the west and north of the UK. The winter and early spring
were drier-than-average in the west of the country, with drier-than-average condi-tions extending further east in April. The dry spell lasted until June (Table 1) with the UK average precipitation for January–June
2010 being only 74% of the 1961–1990 average. In the past 100 years, only 1929 had a drier first half to the year. The dry spell ended in July which was wetter-than-average over much of the country. The southeast, which remained dry in July, had a wet August.
Throughout the summer, above average temperatures were experienced across most of Europe and western Russia. Although the most extreme temperatures were recorded in the region around Moscow, which reported a July anomaly of almost 7 degC, the positive temperature anomaly in north-ern Europe in July was 2.95 ± 0.25 degC, the highest July average on record for the region. The summer average temperature in northern Europe was comparable to that of 2003.
It is interesting to compare the relative significance of the cold and warm spells in Europe. The unusual cold in January extended over much of northern Eurasia, whereas the unusual warmth in July was more localized, with an area of below aver-age temperatures further east. Although January was cold in northern Europe, it was well within the historical range of January temperature anomalies, whereas July was locally the warmest on record, exceeding
Figure 6. Winter average North Atlantic Oscillation (NAO) index 1867 to 2010. The blue bars show the yearly values for December to February and the red line shows the data after they have been smoothed on near-decadal time scales by applying a 21-term binomial filter three times. The green bar shows the average for the 2009–2010 winter.
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Figure 7. Global seasonal-average lower stratospheric (a) and tropospheric (b) temperature anomalies from satellites and weather balloons. The trends in the series are shown in the panels to the right where the tropospheric trends are also compared to temperature changes at the surface over the periods 1958–2009 and 1979–2009. RSS (Mears and Wentz, 2009a; 2009b) and UAH (Christy et al., 2003) are based on satellite data. HadAT2 (Thorne et al., 2005) is based on weather balloon data, which have been vertically weighted to resemble the satellite data. Place names in red indicate major volcanoes.
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HadAT2 radiosonde data and HadCRUT3 surface data are produced by the Hadley Centre and are available at www.hadobs.orgUAH MSU satellite data are produced by the University of Alabama in Huntsville and are available at www.nsstc.uah.edu/public/msu courtesy of John Christy and Roy SpencerRSS MSU satellite data are produced by Remote Sensing Systems and are available at www.remss.com courtesy of Carl Mears
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Figure 8. (a) Annual average mean Central England (Parker and Horton, 2005, updated) and European (Brohan et al., 2006, updated) temperature anomalies (degC relative to 1961–1990, blue bars) from 1880 to 2010 and two standard-deviation uncertainties (fine black lines). The red lines show the annual values smoothed with a 21-point binomial filter and highlight the interdecadal variations. The dashed portions of the red line show where the smoothed values are liable to change as new data are added to the end of the series. (b) Mean daily Central England Temperature (°C, CET) for 2010 (dark blue line). The heavy black line shows the normal for 1961–1990 after smoothing, and the red lines are the corresponding 10th and 90th percentiles for each day of the year. The yellow band is the interval between the 5th and 95th percentiles. The light grey lines represent the highest and lowest values of mean CET in the daily record since 1772 (Parker et al., 1992).
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Monthly and annual mean CET (Manley, 1974; Parker et al., 1992), UK temperature (Perry and Hollis, 2005a, 2005b), total England and Wales precipitation (Alexander and Jones, 2000) and UK precipitation for 2010.
CET 2010°C (anomaly, degC) UK 2010°C (anomaly, degC) EWP 2010 mm (anomaly, %) UK precip. 2010 mm (anomaly, %)
January 1.4 (−2.4) 0.9 (−2.1) 79 (86) 79.7 (71)
February 2.8 (−1.0) 1.9 (−1.1) 88 (135) 74.8 (95)March 6.1 (0.4) 5.1 (0.4) 72 (96) 79.4 (86)April 8.8 (0.9) 8.0 (1.2) 31 (50) 48.0 (71)May 10.7 (−0.5) 9.8 (0.0) 36 (54) 39.0 (55)June 15.2 (1.0) 14.2 (1.5) 43 (65) 38.6 (54)July 17.1 (1.1) 15.6 (1.2) 69 (110) 107.6 (146)August 15.3 (−0.5) 14.2 (0.0) 103 (134) 97.6 (108)September 13.8 (0.2) 12.8 (0.6) 85 (109) 114.0 (113)October 10.3 (−0.3) 9.4 (0.0) 86 (98 ) 101.1 (90)November 5.2 (−1.4) 4.3 (−1.2) 93 (101) 123.2 (108)December −0.7 (−5.4) −1.0 (−4.8) 38 (40) 47.4 (41)Annual 8.8 (−0.6) 8.0 (−0.4) 820 (90) 950.3 (86)
temperatures recorded in both July 2003 and July 2006. Cattiaux et al. (2010) and Osborn (2011) showed that the 2009–2010 winter in Europe was not as cold as might have been expected given the atmospheric circulation.
The unusual circulation pattern associ-ated with the heatwave over Russia and Europe consisted of an anomalous upper level ridge over eastern Europe. Downstream of this was an anomalous upper level trough that extended south towards Pakistan. The interaction of this with the monsoon system led to heavy and persistent rain that caused widespread and catastrophic flooding in Pakistan in July and August.
The summer was also marked by unusu-ally low Arctic sea-ice extent. The minimum extent for 2010 was 4.60 × 106km2, reached on 19 September. The median ice extent for September 2010 was 4.83 × 106km2 (Figure 10). This is the third lowest extent on record, 630 000km2 above the record low of 2007 and 280 000km2 above the 2008 fig-ure. The pressure patterns that contributed to the low extent in 2007 returned in 2010 but were less persistent, breaking down temporarily in July then reforming in August.
The UK 2010–2011 winter weather began unusually early. In late November, winds from the east or north brought two spells of persistent snow and very low tempera-tures which lasted until just after Christmas. Temperatures fell below −10°C across wide areas and in Scotland temperatures below −20°C were recorded. Snow depths accu-mulated to more than 50cm across the high ground of eastern England and eastern Scotland. These were the most significant and widespread snowfalls in late November since November 1965, whilst December was the coldest in the UK in the last 100 years, with temperatures 5 degC below the 1961–1990 average, and the coldest in the Central
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England region for 120 years. The mean CET for December was −0.7°C. The 31-day period beginning 27 November, with an average CET of −1.5°C, was, by more than half a degree, the coldest 31-day period begin-ning in November in the entire 239-year daily CET record.
In the north African Sahel, on the south-ern fringes of the Sahara, rainfall in 2010 was slightly below the long-term average (Figure 11). Despite this, it was the wettest year since 1999. Although the past decade was drier than the long-term average, it was moister than during the droughts of
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Figure 9. (a) Surface air-temperature anomalies for Europe and sea-surface temperature anomalies for neighbouring waters (degC, relative to 1961–1990) for December 2009 to February 2010, March to May 2010, June to August 2010, and September to November 2010. Data are an update of Brohan et al. (2006). The crosses and dashes show the extreme anomalies expressed as percentiles of the 1961–1990 distribution of seasonal temperatures calculated using the method of Horton et al. (2001). (b) Seasonal precipitation totals expressed as a percentage of the 1961–1990 average. Data are from Rudolf and Rubel (2005), Rudolf and Schneider (2005), Schneider et al. (2010).
Figure 10. Arctic sea-ice extent (106km2) for September (1953–2010). Ice extent is defined as the total area of 1° latitude × 1° longitude grid boxes in which the sea ice concentration is 15% or above. The analysis is an update of Rayner et al. (2003).
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1982–1987 and 1972–1973. The Sahel rainfall series is not representative of some semi-arid areas of North Africa, such as mountainous, data-sparse Ethiopia (Conway et al., 2004), but Dai et al. (2004) have con-firmed the overall reliability of the multi-decadal variations in the series.
Hurricane formation in the Atlantic basin is favoured by the transition to La Niña and above-average tropical SST. The 2010 Atlantic hurricane season (1 June–30 November) was the most active since 2005. In the period from 1 June to 30 November, 19 named storms developed in the Atlantic,
with 12 becoming hurricanes, including 5 major hurricanes (category 3, 4 and 5 hur-ricanes). The climatological averages (1950–2005) are 10.3 named storms, 6.2 hurricanes and 2.7 major hurricanes. It was, however, fortunate (and fortuitous) that most of the storms in 2010 stayed out over the ocean and did not hit inhabited regions. La Niña favours hurricane formation in the Atlantic but it suppresses it in the Pacific. This contrast was particularly marked in 2010 with the north Pacific experiencing one of the quietest hurricane seasons on record.
More detail on the climate in 2010 is to be found in the World Meteorological Organization’s (WMO’s) statement on the status of global climate in 2010 on http://www.wmo.int and in the State of the Climate report published in the August issue of the Bulletin of the American Meteorological Society and online at http://www.ncdc.noaa.gov/bams-state-of-the-cli-mate/. Selected global and UK data sets can be accessed from http://www.metoffice.gov.uk/hadobs
AcknowledgementsThe authors were supported by the Joint DECC/Defra Met Office Hadley Centre Climate Programme (GA01101). We would like to thank Phil Jones at the University of East Anglia who contributed to the land-surface temperature analysis. Andrew Colman pro-vided data for the Sahel rainfall. John Prior and Mike Kendon of the National Climate Information Centre assisted with the UK information.
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Figure 11. Annual rainfall anomalies (in standardized units) for the Sahel during 1901–2010. The approximate region is indicated by a red box on the inset map. Standardization is based on averages and standard deviations of stations’ data for generally around 50 years ending in 1973 (Nicholson, 1985). The smooth red curve was created by applying a 21-term binomial filter to the annual values. The values from 1901 to 1984 are from Nicholson (1985); from 1985 to 2000 they are calculated from internationally transmitted monthly climate data, whilst those for 2001 onwards are based on NCEP gridded gauge data (Chen et al., 2002).
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Correspondence to: John Kennedy, Met Office, Hadley Centre, Fitzroy Road, Exeter EX1 3PB, UK
© British Crown copyright, the Met Office, 2011, published with the permission of the Controller of HMSO and the Queen’s Printer for Scotland
DOI: 10.1002/wea.820