Monthly summaries of what has been happening in the world's climate.
Our climate bulletins give brief summaries of what was happening in the climate in recent months and years. Please also see our page providing explanation of some of the terms used in the bulletins.
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The global average temperature for October 2012 as estimated from the HadCRUT4 data set was 0.52 ± 0.16 °C above the 1961-1990 average, bringing the average temperature for the first 10 months of 2012 to 0.44 ± 0.10 °C above the 1961-1990 average. 2012 is likely to be between the 4th and 14th warmest year on record.
Conditions in the tropical Pacific remain neutral, with no indication of either El Niño or La Niña conditions.
In October near-surface temperatures were significantly - above the 90th percentile of occurrence - above average across the north Atlantic, northern Africa and parts of western Eurasia, far eastern Eurasia and eastern South America. Large areas of the Indian Ocean were also significantly warmer than average. Significant cold - temperatures below the 10th percentile - were recorded in limited areas of the north Pacific, south Atlantic and in western Canada.
The global average temperature for the first 9 months of 2012 estimated from the HadCRUT4 data set was 0.43 ± 0.11 °C above the 1961-1990 average. NASA GISS and NOAA NCDC also produce estimates of the global average temperature anomaly. The former shows that the nine month average for 2012 was 0.42 °C above the 1961-1990 average and the latter shows it as 0.44 °C above.
In the early summer sea-surface temperatures in the Tropical Pacific were approaching El Niño thresholds. Over the past few months sea-surface temperatures in the Tropical Pacific have dropped to ENSO neutral levels consistent with other atmospheric indicators such as cloudiness, trade wind strength and sea level pressure.
September saw temperatures that were significantly above average across large areas of the north Atlantic, parts of Eurasia, Canada. South America and the Indian Ocean. Significantly below average temperatures were recorded in parts of the north Pacific. The pattern of temperatures in the north Atlantic and north Pacific are consistent with the positive phase of the Atlantic Multidecadal Oscillation and the negative phase of the Pacific Decadal Oscillations respectively.
The global average temperature for the first eight months of 2012 was 0.42 ± 0.12 °C above the 1961-1990 average according to the HadCRUT4 dataset. Estimates from NASA GISS and NOAA NCDC were 0.41 °C and 0.43 °C respectively. Sea surface temperatures in the tropical Pacific approached El Niño thresholds in July, but have since fallen to more neutral conditions. Even when sea surface temperatures were at their peak, the atmospheric response did not show the definite characteristics of El Niño.
The global average temperature estimated from the HadCRUT3 data set for January to June 2012 was 0.33 ± 0.10 °C above the 1961-1990 average. Comparable estimates from NASA GISS and NOAA NCDC were 0.41 °C and 0.40 °C.
The average temperature for the year to date is higher than the equivalent period in 2011. However, in the latter half of 2011, a La Niña developed which was followed by a dip in global average temperature. As of August 10th 2012, conditions in the tropical Pacific are close to El Niño thresholds. With elevated temperatures in the tropical Pacific, temperatures in the second half of the year could well be warmer than the same period in 2011.
June 2012 saw temperatures that were significantly above average (that is above the 90th percentile based on 1961-1990 statistics) across the Mediterranean region and over many parts of Asia. Large areas of the north Atlantic and Indian Ocean were also significantly warmer than average. There were also areas which were significantly colder than average (below the 10th percentile). Northern Australia, areas of northern Europe and parts of the north Pacific and south Atlantic were significantly cooler than average.
The global average temperature for January to May 2012 was 0.31 ± 0.10 °C above the 1961-1990 average according to the HadCRUT3 data set. Similar estimates are available from NASA GISS (0.48 °C) and NOAA NCDC (0.38 °C). HadCRUT3 has tended to be cooler than the GISS and NCDC estimates in recent years because of its relatively poor coverage of the Arctic and high latitude land areas.
Conditions in the tropical Pacific across a range of indicators are becoming more El Niño like, but sea-surface temperatures remain below El Niño thresholds. Global average temperatures have increased since ENSO conditions returned to neutral following the double-dip La Niña of 2011.
Colder-than-average surface temperatures were observed in the north Pacific, the tropical Atlantic, Australia, Alaska and parts of western Canada. Areas of the southern ocean were also cooler than the long term average. Warmer than average surface temperatures were observed across much of north America, the north Atlantic, Eurasia, the western tropical Pacific and the Indian Ocean.
The global average temperature for April 2012 was 0.48 ± 0.15 °C above the 1961-1990 average. The average for the year so far was 0.28 ± 0.10 °C.
ENSO conditions are now near neutral with sea surface temperatures (SSTs), sub-surface ocean temperatures, pressure differences and cloud cover at near normal levels. Global temperatures tend to lag variations in the tropical Pacific SSTs by a few months.
In April 2012, most northern hemisphere land areas were warmer than average. The southern US and central Asia were much warmer than average. Western Europe was colder than average. Over the oceans, the north Atlantic continues to be unusually warm, but SSTs in parts of the tropical Atlantic were below the 2nd percentile of occurrence. Parts of the north east Pacific were also unusually cold. In contrast the western Tropical Pacific and the eastern Indian Ocean were much warmer than average. Colder than average conditions persist in the Southern Ocean.
February and March 2012
The global average temperature for the first three months of 2012 was 0.21 ± 0.10 °C above the 1961-1990 average. 2011 saw a double-dip La Niña, with a strong La Niña at the start of the year and a weaker La Niña developing towards the end. Conditions in the tropical Pacific are now near normal for a range of indicators, but short term variations in global temperatures typically lag the ENSO cycle by a few months so last year's La Niña is likely still having a cooling effect on global temperatures.
Much of North America was warmer than average in January, February and March. March in particular was a warm month over the USA with record temperature anomalies for March in some areas. March was also very warm over the UK and western Europe. In contrast Alaska and much of Australia were colder than average. A distinctive pattern of cooler than average sea-surface temperatures along the west coast of the USA, coupled with warmer than average sea-surface temperatures in the central north Pacific continues to be a feature of the global temperature anomaly pattern.
The global average temperature for 2011 was 0.35±0.09 °C above the 1961-1990 average. 2011 was therefore cooler than the average for the past decade (0.43±0.06 °C). However, the temperature of 2011 was influenced by the effects of a double-dip La Niña: a strong La Niña was active at the start of the year and, after a brief return to ENSO-neutral conditions, a second, weaker La Niña developed in the second half of the year. 2011 was warmer than all other strong La Niña years in the record.
The effect of La Niña on global average temperature tends to lag temperature changes in the tropical Pacific by a few months so the recent warming in the tropical Pacific has not yet shown up in global temperatures. The global average temperature in January 2012 was 0.22±0.16 °C above the 1961-1990 average, marginally warmer than January 2011 and warmer than January 2008.
Parts of the eastern Indian Ocean and western Pacific Ocean remained significantly warmer than average, with the remnants of the La Niña cold tongue still evident in the central Tropical Pacific. Further east, however, sea-surface temperatures in January were above average. Large areas of the North Atlantic remain significantly warmer than average, reflecting, at least in part, the continuing warm phase of the Atlantic Multidecadal Oscillation. In the south Atlantic an area of much lower than average sea-surface temperatures was seen north of 30°S, with a band of much warmer than average waters to the south.
During northern hemisphere winter it is common to see large temperature deviations from normal over the continents. January 2012 was no exception. While Alaska and southern Asia were colder than average (Alaska exceptionally so), the rest of North America and northern Eurasia were warmer than average. In the southern hemisphere western parts of Australia were significantly colder than average, and the southern part of South America, South Africa and some of the Indian Ocean islands were much warmer than average.
The global annual average temperature for 2011 was estimated to be between 0.35 and 0.45 °C above the 1961-1990 average according to figures from the HadCRUT3, NOAA NCDC and NASA GISS analyses. This places 2011 among the 15 warmest years and most likely between the 9th (HadCRUT3) and 12th (GISS) warmest. Although 2011 was significantly warmer than the average for the 1990s, it was cooler than average for the 2000s. The cooling relative to recent years is partly due to the double La Niñas which bookended 2011.
La Niña conditions continue, but have shown signs of weakening over the past few weeks, with sea-surface temperatures in the eastern Pacific returning to near normal. Further west, however, sea surface temperatures remain close to La Niña thresholds.
In December significant warmth - temperatures exceeding the 90th percentile - were recorded over large areas of Europe, Canada and northern Eurasia. Areas of the western Pacific, north Atlantic and Indian Ocean were also significantly warm. Significant cold - temperatures below the 10th percentile - were recorded across Australia, parts of the Eastern Pacific, a region east of the Caspian Sea, in the South Atlantic and along parts of the Antarctic coastline.
The global average temperature calculated from HadCRUT3 for the period January to November 2011 was 0.35 ± 0.10 °C above the 1961-1990 average. Taking this average as an estimate for the year as a whole would place 2011 as the joint 11th warmest year on record together with 1997. Current estimates from NOAA NCDC and NASA GISS place 2011 as the 11th and 9th warmest year, respectively.
The second dip of the double-dip La Niña continues and sea-surface temperatures remain below average across much of the tropical Pacific. This is reflected in the continuing run of global temperatures that are lower than the average for the past decade.
The area around the Black Sea and the Caspian sea was unusually cold for November with temperatures for the month falling below the 2nd percentile (based on 1961-1990 statistics). Other areas of unusually low temperatures included parts of the tropical Pacific and in the Atlantic at around 30°S. In contrast, much of the Indian Ocean was significantly warmer than average, with temperatures in some areas exceeding the 98th percentile. Parts of the western Pacific, the north east Atlantic and north west Europe were also significantly warmer than the 1961-1990 average.
Weak La Niña conditions continue with sea-surface temperatures in the tropical Pacific close to or just below La Niña thresholds. Pacific sub-surface temperatures are below average in the east and above average in the west.
La Niña conditions persist in the tropical Pacific, but indicators show that for the moment, the event is weaker than the strong La Niña of 2010/11. Nevertheless, the cooler conditions are likely to affect global temperatures with a lag of a few months.
Sea-surface temperatures in the tropical Pacific have fallen since July, and are close to the threshold for La Niña. Sub-surface ocean temperatures in the tropical Pacific show a large volume of colder than average water in the eastern Pacific.
Global temperatures have increased since the start of the year, reflecting the return from La Niña to neutral ENSO conditions. Sea-surface temperatures are currently slightly below average (1961-1990) across the central Pacific, but are slightly above average in the east.
The global average temperature for the first half of 2011 was 0.31 ± 0.10 °C above the 1961-1990 average. Global average temperatures have increased since the start of the year reflecting the shift from La Niña to neutral ENSO conditions in the Tropical Pacific that has occurred since the start of the year. The January to June average for 2011 was warmer than the equivalent period in 2008 and the 12-month running average global temperature remains higher than the minimum value seen after the 2007/08 La Niña.