–January–December 2012 Blended Land and Sea Surface Temperature Percentiles

A natural hemispheric-scale climate pattern called the Arctic Oscillation (AO) can be a dominating driver of winter temperatures in the Northern Hemisphere. Its effects were particularly felt from the end of January to mid-February, when the AO was negative. A negative AO is associated with cold polar air that spills southward into the mid-latitudes from the Arctic region and warm air that advects northward from nearer the equator.

Due at least in part to this pattern, frigid temperatures were felt across much of Europe during this time, bringing the worst cold snap to the region in at least the past 26 years. Hundreds of people perished across a dozen countries in central and eastern Europe due to the polar outbreak. Austria's average February temperature was the coldest on record for the month since 1986. Germany also experienced its coldest February since 1986 and 15^th coldest since records began in 1881. Spain had its fourth coldest February since its records began in 1961. At the same time, part of Canada was much warmer than average, as temperatures in Ontario, Canada during February "rivaled record values set in 1998", according to Environment Canada. Temperatures across the region ranged from 3.7°C to 6.8°C (6.7°F to 12.2°F) above average. Overall, Canada observed its third warmest winter since national records began in 1948, with the average temperature 3.6°C (6.5°F) above average and virtually no parts of the country colder than average. And in contrast to the winters of 2009/10 and 2010/11, which were colder than average due to the impacts of the negative AO, the contiguous United States was not impacted in the same way by the climate pattern during this period, as it observed its fourth mildest winter since records began in 1895.

In the Southern Hemisphere, with La Niña still in place, Australia reported its 11^th coolest average maximum and 15^th coolest average minimum austral summer temperature in the country's 63-year period of record.

As winter gave way to spring in the Northern Hemisphere, warmer-than-average temperatures prevailed across much of this region. The contiguous United States had its warmest March on record. Norway also had its warmest March since national records began in 1900. Austria and Germany each had their third warmest March since records began in 1767 and 1881, respectively. The United Kingdom (UK) recorded its warmest March since 1957 and the third warmest since national records began in 1910. Provisionally, Scotland was record warm for the month.

The warmth continued in parts of North America in April, where the contiguous United States had its third warmest April on record. However, in Europe, the UK had its coolest average April temperature since 1989. According to the UK's Met Office, April 2012 was cooler than March 2012, an unusual event that last happened in 1998. It was also cooler than average in Spain, Norway, and Sweden during April.

In the Southern Hemisphere, the lingering effects of La Niña contributed to Australia's third lowest maximum March temperature and fourth lowest minimum autumn (March–May) temperature on record.

For the March–May period, the contiguous United States had its warmest spring on record and to the north, Canada had its ninth warmest such period. Across the Atlantic, Austria observed its seventh warmest spring in its 246-year period of record.

Austria's warmth carried over into June, as the country recorded its highest ever June temperature of 37.7°C (99.9°F) on the 30^th in two locations—the capital city of Vienna and in German-Altenburg, Nope. The monthly temperature averaged across Austria was the sixth warmest June on record. However, in other parts of Europe, Norway had its 25^th coolest June in its 113-year period of record and the UK had its coolest June since 1991. It was also the coolest July for the UK since 2000. In Australia, the average July maximum temperature was the lowest for that month in the past 30 years. It was a different story in North America, however, as the contiguous United States observed its hottest July (and hottest month ever) on record.

August brought warmer-than-average temperatures to many regions around the world. It was warmer-than-average across New Zealand and temperatures in Australia rebounded from July, with the average maximum temperature ranking as the sixth warmest on record for August. Two separate heat waves brought Spain its second warmest August since 1961, while Austria had its fourth warmest August on record.

The summer (June–August) period in Canada was 1.9°C (3.4°F) above the 1961–1990 average, making this Canada's all-time warmest summer in the 65-year period of record, beating the previous record set in 1998 by 0.2°C (0.4°F). A warmer-than-average August, combined with the record-high July temperatures and a warmer-than-average June brought the contiguous United States its second hottest summer on record.

Following the second warmest summer for Hungary since national records began in 1900, monthly temperatures remained above average across the entire country during September, ranging from about 1.0°–3.5°C (1.8°–6.3°F) above the 1971–2000 average.

Australia had its third warmest maximum September temperatures on record; and monthly-averaged daily, maximum, and minimum temperatures were all above average across Argentina, particularly in the central and northern regions of the country. These warm temperatures contributed to record September warmth across global land and ocean surfaces—the only globally-averaged record warm month of 2012.

A series of low pressure systems that plagued the UK during part of the year kept temperatures below average during October, with the lowest October temperature recorded since 2003. Scotland was the coolest since 1993. Meanwhile, central and southeastern Europe were warmer than average during the month. Temperatures were up to 1.6°C (2.9°F) above the 1961–1990 average across large parts of Croatia, while the Republic of Moldova reported monthly temperatures across the country that ranged from 2.5° to 3.5°C (4.5° to 6.3°F) above average.

November was cooler than average in New Zealand, while maximum temperatures were the fourth highest for November on record in Australia. In Europe, Hungary, Austria, Croatia, and the Republic of Moldova were warmer than average. However, in East Asia it was the fifth coolest October maximum temperature for South Korea. It was also colder than averge in China, with the national average temperature 0.9°C (1.6°F) below average. The regions of northern Xinjiang and central Inner Mongolia were 2°–4°C (4°–7°F) colder than average.

Beginning in late November, severe cold swept across much of Eurasia as the Arctic Oscillation became negative and remained strongly negative through December. This negative phase led the polar jet stream to dip down over Eurasia bringing frigid air from the north to the region to close out 2012. Northern and eastern China had its coldest period for this time of year in the past 28 years, according to China's National Climate Center. The capital city of Beijing observed its lowest average temperature since at least 1951. Through December, Russia experienced its coldest winter to date since 1938, with temperatures as much as 10°–15°C (18°–27°F) below average. Temperatures fell to as low as -50°C (-58°F) in some parts of Siberia. In Europe, the Republic of Moldova, Hungary, Sweden, Finland, and Norway were all colder than average during December. The U.S. state of Alaska observed its 18^th coolest December since records began in 1918, with the average monthly temperature 3.3°C (5.9°F) below the 1971–2000 average. Conversely, Australia had its fourth highest December maximum temperatures since records began in 1910. And in New Zealand, many record or near-record monthly temperatures were reported across the North Island, around Nelson, and parts of the South Island.

Notably, for 2012 as a whole, the contiguous United States had its warmest year in its 118-year period of record, surpassing the previous record set in 1998 by 0.6°C (1.0°F). A list the top 10 weather and climate events for the United States is also available.

With winter, spring, and summer all among Canada's top 10 warmest for their respective seasons, the January–November period for 2012 was the fourth warmest since records began in 1948, according to Environment Canada. A list of Canada's top 10 weather and climate events of 2012 is also available.

In Europe, Austria experienced its seventh warmest year since national records began in 1767, at 1.0°C (1.8°F) above the long-term average. Norway had its 45^th warmest year since records began in 1900, at 0.4°C (0.7°F) above average.

The 2012 temperature across the United Kingdom was 0.1°C (0.2°F) below the 1981–2010 average. This is in part attributed to the UK's coolest summer since 1998 and coolest autumn since 1993.

With the first half of 2012 cooler than average and the second half warmer than average, on balance the annual 2012 temperature across Australia was 0.06°C (0.11°F) above the 1961–1990 average. Only the year 2011 has been below average in the past decade.

––January–December 2012 Land-Only Precipitation Percent of Normal

La Niña conditions brought heavy rainfall to Australia, especially in the east, during the first few months of 2012, but conditions turned drier during the latter half of the year after ENSO-neutral conditions took hold. From April through December, rainfall was generally below average for the period. According to the Bureau of Meteorology, a positive Indian Ocean dipole, associated with cooler sea surface temperatures off the northwest coast of Australia and typically drier conditions across parts of the continent, emerged in early August and continued into October. This likely contributed to drier-than-average conditions across southern Australia. Overall, following the record wet year of 2011, 2012 precipitation was near the median of annual values dating back to 1900.

The year started off rather dry for the United Kingdom and then changed fairly abruptly. Following its driest March on record, the UK observed its all-time wettest April. A series of low pressure systems continued to impact the country, with June also being record wet. Remarkably, even with the dry conditions early on, the UK had its second wettest year since records began in 1910, falling just 7.3 mm (0.29 inches) shy of the record wetness of 2000. Provisionally, England had its all-time wettest year on record.

Finland was wetter than average for 2012, with many stations observing their wettest year in the past half century. The capital city of Helsinki reported its second wettest year, behind 1944, since records began in the early 19^th century.

In northern Brazil, lack of rain during first half of 2012 led to the worst drought in five decades and resulted in "water wars" which provoked extreme behavior and led to fatalities. An estimated 4 million people were affected. Water supplies were threatened in 1,100 municipalities. Some regions in northeastern Brazil had their record driest January–October on record, according to the World Meteorological Organization (WMO).

In the contiguous United States, in addition to the summer being hot for a large part of the country, it was also dry, resulting in a drought footprint comparable to the drought episodes of the 1950s. The drought peaked in July, when the percent area of the CONUS in at least moderate drought was 61.8 percent, according to the Palmer Drought Severity Index (PDSI). The summer was the 14^th driest on record for the country. The epicenter of the drought stretched from the Rockies through the Great Plains and into the Midwest. The drought resulted in a multi-billion dollar agricultural disaster—the most severe and extensive drought impact since 1988.

At the same time, drought gripped western Russia, western Siberia, Ukraine, and Kazakhstan, damaging agricultural crops. According to the WMO, more than $630 million U.S. dollars in damages were incurred in western Russia and western Siberia alone.

Several countries in eastern Europe, including Romania, Hungary, Bulgaria, and Poland, experienced drought during September. It was one of worst droughts for Hungary in two decades.

It was also extremely wet in some areas of the world. According to the Japan Meteorological Agency, record 24-hour rainfall of up to 500 mm (20 inches) was observed on Japan's southern island of Kyushu in mid-July. Subsequent flooding and landslides killed more than two dozen residents. In and around Beijing, China, up to 170 mm (6.7 inches) of rain fell within a 16-hour period on July 21^st, leading to the worst flooding in six decades in the region.

The South Asian monsoon season in India starts around the beginning of June and lasts into October. Rainfall during the pre-monsoon season was the lowest on record since 1901 and rainfall continued to be deficient during the first half of the monsoon season. However, the monsoon stalled over northwestern India before beginning its annual withdrawal, bringing excessive rainfall to most of the region during the month of September. The heavy rainfall brought seasonal precipitation totals to within the normal range and alleviated drought conditions for much, but not all, of the country. By the withdrawal date on October 10^th, India as a whole experienced rainfall that was 92 percent of average, within the normal range, according to the India Meteorological Department.

During mid-September, Super Typhoon Sanba—the year's first category 5 storm among all tropical cyclone basins—brought locally heavy rainfall to Okinawa Island, Japan, parts of the Philippines, including the capital city of Manilla, and both North and South Korea. Super Typhoon Jelawat—the year's second category 5 storm—also impacted part of the eastern Philippines and parts of Japan, including Okinawa and Tokyo.

At the end of September, Sandy dumped copious rain over Jamaica, Haiti, the Dominican Republic, Cuba, and much of the eastern United States. Post-tropical storm Sandy also brought blizzard conditions to the Central and Southern Appalachians, shattering all-time U.S. October monthly and single storm snowfall records.

The rainy season was wetter-than-normal across western and central Africa. From July to October, over 3 million people were affected across 15 countries, most notably in Nigeria, Niger, Senegal, and Chad.

Tropical cyclones rarely hit the southern Philippines; however, Category 5 Super Typhoon Bopha struck southern Mindanao Island in early December, dumping copious rainfall over the region, killing more than 900 residents, and leaving more than 600 missing. This is the same region where Tropical Storm Washi hit just one year earlier, in December 2011, killing more than 1300 people.

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References

Peterson, T.C. and R.S. Vose, 1997: An Overview of the Global Historical Climatology Network Database. Bull. Amer. Meteorol. Soc., 78, 2837-2849.

Quayle, R.G., T.C. Peterson, A.N. Basist, and C. S. Godfrey, 1999: An operational near-real-time global temperature index. Geophys. Res. Lett., 26, 333-335.

Smith, T.M., and R.W. Reynolds (2005), A global merged land air and sea surface temperature reconstruction based on historical observations (1880-1997), J. Clim., 18, 2021-2036.

Smith, et al (2008), Improvements to NOAA's Historical Merged Land-Ocean Surface Temperature Analysis (1880-2006), J. Climate., 21, 2283-2293.

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