Global and regional climate in 2010
Article first published online: 24 JUN 2011
© British Crown Copyright, 2011, published with the permission of the Controller of HMSO and the Queen's Printer for Scotland.
Special Issue: Climate perspectives and public perception
Volume 66, Issue 7, pages 188–194, July 2011
How to Cite
Kennedy, J., Morice, C. and Parker, D. (2011), Global and regional climate in 2010. Weather, 66: 188–194. doi: 10.1002/wea.820
- Issue published online: 24 JUN 2011
- Article first published online: 24 JUN 2011
The 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 average (Figure 1(a)). 2010 is nominally the second 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 anomalies in these regions, with GISS extrapolating 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 average temperature. The effects of El Niño on global temperature typically lag temperature 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 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 (Figure 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 temperatures are typically smaller than for the hemispheres and globe because temperature anomalies are geographically more coherent in the tropics and the anomaly for a single station is representative of a much wider area.
Figures 3 and 4 show near-surface temperature 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 markedly above average, continuing a pattern that began in the mid 1990s. These high sea-surface temperatures are partly a manifestation of the positive phase of the Atlantic Multi-decadal Oscillation (AMO). The AMO has been shown to influence rainfall 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 distribution – 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 climatology period, due partly to the warmer than average sea-surface temperatures in the neighbouring seas. Abnormal cold - temperatures 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 temperatures 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 unusually 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 temperatures since 1958 (radiosonde era) and since 1978 (satellite era). For reference, these are compared with surface temperature trends and they illustrate the uncertainty arising from imperfections in observing systems and analysis techniques. The fluctuations in global surface temperature associated with El Niño and La Niña are amplified in the troposphere. This tropospheric amplification is expected to be largest 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 climate
In 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 respectively. 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).
|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)|
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 coincided 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 easterly winds become more common. The daily NAO index turned negative in mid-December 2009 and remained below average for the rest of the winter except for a spell in mid-January. Although northern Europe experienced a cold winter, temperatures in southern Europe were above average.
Because of the associated lapse in westerlies, the negative phase of the NAO is typically 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 conditions 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 northern 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 average 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 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 associated 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 unusually 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 figure. 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 temperatures 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 accumulated 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 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 beginning in November in the entire 239-year daily CET record.
In the north African Sahel, on the southern 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 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 confirmed 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 hurricanes). 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-climate/. Selected global and UK data sets can be accessed from http://www.metoffice.gov.uk/hadobs
The 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 provided 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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