Report: ----- National ----- National Overview Drought Wildfires Hurricanes & Tropical Storms National Snow & Ice Tornadoes Synoptic Discussion ----- Global ----- Global Analysis Upper Air Global Snow & Ice Global Hazards El Niño/Southern Oscillation ----- Entire Report ----- Year: 2013 2012 2011 2010 2009 2008 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 Month: January February Winter March April May Spring June July August Summer September October November Autumn December Annual

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National Overview

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National Overview

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In 2010, the contiguous United States (CONUS) average annual temperature of 53.8 degrees F (12.1 degrees C) was 1.0 degrees F (0.6 degrees C) above normal, and was the 23^rd warmest year on record. Since 1895, the CONUS has observed a long-term temperature increase of about 0.12 degrees F (0.07 degrees C) per decade. Precipitation across the CONUS in 2010 was 1.02 inches (25.9 mm) above the long-term average (LTA). Over the long-term, precipitation averaged across the CONUS, is increasing at a rate of about 0.18 inches (4.6 mm) per decade.

Seasonal highlights in 2010 included a winter with abnormally cold temperatures and abundant moisture, which resulted in a historic December-February period in the East and Northeast. Several locations broke monthly and seasonal snowfall records. During the spring period, record warmth dominated much of the Northeast contributing to the limited amount of snow fall across the country. Satellite measurements indicated that the U.S. had its 8^th smallest April snow cover extent in the 44-year period of record. The North Atlantic High played a large role in the summer weather pattern along the east coast, contributing to record heat in the South and East. A persistent storm track brought prolific summer rains to the Northern Plains and Upper Midwest. The number of tornadoes, as reported by the Storm Prediction Center (SPC), during the summer was abnormally high—sixth busiest in 60 years. Drought conditions, while record low at the beginning of the summer period, expanded in area by late summer. Nonetheless, the U.S. footprint of drought reached its smallest extent which help limit wildfire activity in 2010. For the second consecutive year, no hurricanes made landfall in the U.S., despite the active tropical cyclone season in the Atlantic Basin.

This annual report places the temperature and precipitation averages into historical perspective, while summarizing the notable events that occurred in 2010. More detailed analysis on individual months can be found through the Climate Monitoring home page.

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Top Ten U.S. Weather/Climate Events for 2010

The following is a list for the top ten U.S. weather/climate events which occurred during 2010. These events were selected by a panel of weather/climate experts from around the country. For additional information on these events, please see our Top Ten U.S. Events webpage.

Rank	Event
1	Consecutive Winter Blizzards/ Extreme Snow Season
2	Nashville and Central TN flooding
3-tie	Hot Summer in the East
3-tie	Midwest Super Storm
5	Hawaiian Drought
6	No hurricanes made U.S. landfall despite active Atlantic
7	Near Eradication of CONUS Drought
8	Vivian, SD Hailstone
9	New England Flooding
10	Minnesota as tornado leader

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Temperature and Precipitation Seasonal Analysis

Winter

The 2009/2010 winter season was marked by anomalously cold air in the South and East. Temperatures for the three-month period (December–February) were dominated by the historically strong negative phase of the Arctic Oscillation (AO). The negative AO allowed cold Arctic air to slide south while warmer air was displaced to the north. This created warmer-than-normal conditions in some of the Northeast, Great Lakes and Northwest, while below to much-below-average temperatures were present from the Rockies eastward into the Mid-Atlantic. The coldest temperature anomalies for the period occurred in the Southeast and Southern Plains. Florida was greatly affected by the persistence of the cold air. In January, its citrus crop sustained heavy damages from sub-freezing temperatures as an estimate by the U.S. Department of Agriculture totaled the crop losses to be more than $450 million. Florida then experienced its fourth coldest February on record. Temperature anamolies were nearly eight degrees F (4.4 degrees C) below the 20^th average. Meanwhile, Maine had its third warmest winter, nearly six degrees F (3.3 degrees C) above the 20^th century average. The average winter temperature across the contiguous U.S. was 1.8 degrees F (1.0 degrees C) below the 20^th century average, or 15^th coolest on record.

The strong presence of El Niño coupled with the negative AO, greatly influenced the jet streams and general weather pattern across the U.S. during the winter period. The average precipitaton for the period was 0.88 inch (22 mm) above normal partly due to a series of winter storms that were generated by the subtropical and polar jets. As a result of the persistent pattern, much of the South, East, and Upper Midwest experienced above to much-above-normal precipitation. One of the note-worthy events during the season were the back-to-back winter storms that affected the Washington D.C. area in February. The first occurred on February 4^th when the Reagan National Airport received 32.4 inches (82.3 cm) of snow, a record amount for that location. On February 9^th-11^th, while digging out from the previous storm, D.C. residents suffered through another storm as 10.5 inches (26.7 cm) of snow fell at the Reagan National Airport. While there were no record precipitation amounts statewide, monthly and seasonal snowfall records were shattered.

Spring

The nationally averaged temperature for the spring period (March-May) was 1.4 degrees F (0.8 degrees C) above the LTA. The season brought record warmth to the Northeast, which was 5.3 degrees F (2.9 degrees C) above normal. Eight northeastern states experienced their warmest such period on record: Connecticut, Rhode Island, Maine, Massachusetts, New Hampshire, New Jersey, New York, and Vermont. Michigan also had its warmest spring period. It was one of the ten warmest spring seasons for ten other states. Conversely, the majority of the western U.S. experienced temperatures that were 2-4 degrees F (1.1-2.2 degrees C) below normal during the spring season. A persistent pattern of a high pressure ridge (associated with warmer conditions) in the East and a western trough (cooler conditions) was especially evident during the period. Much of the coolness in western U.S. can be attributed to unrelenting troughs which filtered in cool moist Pacific air during April and May.

As is typical, precipitation was variable throughout the country during the spring season (March–May) resulting in a near-normal value based on the LTA. Only three states were in the top or bottom tenth percentile. Louisiana had its fifth driest period while Rhode Island and Massachusetts had their second and tenth wettest period, respectively. During the period, warm conditions across the Northeastern quadrant of the country helped limit U.S. snowfall. Several cities in New York did not receive any snow during the month of March for the first time on record. Satellite measurements indicated that the U.S. had its 8th smallest April snow cover extent in the 44-year period of record, while North America as a whole had its smallest spring snow cover extent. As estimated by the U.S. Drought Monitor (USDM), the area of drought in the CONUS increased slightly from 8.8 percent at the beginning of March to 9.3 percent near the end of May. Flooding occurred in Nashville, Tennessee when a stagnant storm system brought more than 13.0 inches (330.0 mm) of rain to the area on May 1^st-2^nd. It was estimated that over $1 billion worth of damages were done. By the second day of the month, Nashville had recorded its wettest May and fifth wettest month on record.

Summer

The summer of 2010 was marked by the persistent Bermuda High that parked itself in the western Atlantic. This area of high pressure was situated abnormally west ushering in warm humid conditions along the east coast and as far inland as the Midwest. This not only lead to record heat in a vast area of the country, but also acted as a block preventing smaller storm systems from entering into the regions. It was the hottest June on record for several states along the mid-Atlantic Coast as well as Louisiana. Nationally, it was the eighth warmest June and August on record. During the first week of July, an oppressive heat wave led to soaring temperatures throughout the eastern half of the CONUS. Hundreds of maximum high and minimum high temperatures were broken, contributing to the third and the fifth warmest July on record for the Southeast and Northeast climate regions, respectively. For the entire summer period (June-August), 12 states were record warm, while only two experienced average temperatures below normal. Overall, it was the fourth warmest summer on record for the CONUS with an average temperature of 1.9 degrees F (1.0 degrees C) above the 20^th century average.

Despite record warm temperatures during the summer period, the nationally averaged precipitation was the ninth wettest in 116 years, 1.09 inches (27.7 mm) above the LTA. As a result of the persistent track of storm systems across the northern-tier states, areas around the Upper Midwest and Great Lakes had an anomalously wet summer. Wisconsin had its wettest June–August on record, while many other surrounding states, including Iowa, Michigan, Nebraska, South Dakota, Minnesota, and Illinois, had near record precipitation averages. New Jersey was the only state to experience a summer that ranked in the bottom ten percent (6^th driest), based on data that date back to 1895. Regionally, both the West and Southeast had below-normal precipitation averages during the summer season.

Fall

Warmer-than-normal temperatures were predominant throughout much of the country during the fall season (September–November). Based on divisional temperature averages, no state experienced a below-normal fall period. These conditions were mostly reflective of the above-average warmth during September and October, a result of the lingering Bermuda high in the Atlantic. The average fall temperature for the CONUS was 1.5 degrees F (0.8 degrees C) above the 20^th century average, ranking 14^th warmest. The constant lack of precipitation in Florida resulted in the second driest September-November period on record. Meanwhile, the tireless storm track over the upper Midwest resulted in much-above-normal precipitation for Minnesota and North Dakota. Maine, Vermont, and New Hampshire also averaged precipitation amounts that were among their wettest ten percent. Overall, precipitation when averaged nationally, was about average for the fall period.

Fall highlights consisted of:

• On September 27^th Los Angeles, California experienced its all-time warmest day (113 degrees F or 45 degrees C) since record keeping began in 1877.
• Major flooding occurred along the Atlantic coast attributable to the remnants of Tropical Storm Nicole
• Severe weather caused eight tornadoes in a single day in Arizona, which only averages four per year
• A powerful low pressure system developed in the Upper Midwest and broke state records for lowest atmospheric pressure observed in Wisconsin
• Winter weather impacted areas in the Upper Midwest as Duluth, Minnesota had its sixth snowiest autumn on record.

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Alaska Annual Summary

Alaska temperatures in 2010 were above the 1971-2000 average, continuing the upward trend of the last 20 years. Winter temperatures in 2009-2010 were 3.1 degrees F (1.7 degrees C) above average. Spring temperatures were 0.7 degrees F (0.4 degrees C) above average, summer was 0.4 degrees F (0.2 degrees C) above average, and fall was 3.1 degrees F (1.7 degrees C) warmer than the average.

Precipitation in Alaska in 2010 was near normal. While it was the fifth driest winter, spring was near normal. Summer precipitation was about 11 percent above the 1971-2000 average and fall precipitation was near normal.

In November, a widespread rain-event coupled with sub-freezing surface temperatures in Alaska resulted in a major ice storm. It was reported that the affected area was the combined sizes of Texas, Oklahoma, and New Mexico. The rainfall amount was the second largest daily rainfall amount between November and March in Fairbanks since record keeping began in 1904.

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Very Warm/Cold and Wet/Dry Percentages

One way to assess the magnitude of warm/cold and wet/dry episodes is to compute the percent area of the contiguous United States that was "very warm/very cold" and that which was "very wet/very dry". The figures above depicts these values for each month in the past 30 years. These percentages are computed based on the climate division data set. Those climate divisions having a monthly average temperature/precipitation in the top ten percent (> 90^th percentile) of their historical distribution are considered "very warm/very wet" and those in the bottom ten percent (< 10^th percentile) are "very cold/very dry".

During 2010, the U.S. experienced an extremely cold winter which transitioned into a record breaking warm summer. In terms of the area of the contiguous U.S., 38 percent experienced temperatures that were in the bottom 10^th percentile or categorized as "very cold" in December. This definition correlates well with "much below normal" in terms of NCDC ranking methods. The anomalously cold temperatures infiltrated into the U.S again in February when 27.4 percent of the country was categorized as "very cold". Influenced by a weakening El Niño and a strengthening Bermuda High, "very warm" conditions prevailed in the spring and culminated in the summer months. During April, June, and August at least 30 percent of the country experienced conditions that are categorized as "very warm".

Conditions that are categorized as "very wet" existed throughout the U.S. during January–December, resulting in a historically low drought footprint on July 6^th. While the high pressure systems, which typically deliver very little precipitation, dominated the east, the persistant upper level jet stream over the northern tier states produced copious amounts of precipitation for the Upper Midwest. During six of the first seven months of the year (each month except March) conditions categorized as "very wet" prevailed over conditions categorized as "very dry". Furthermore, conditions categorized as "very dry" only existed for greater than 10 percent of the country during three months—March, September and December.

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Lower Tropospheric

The 2010 temperature in the lower troposphere was slightly above-average. Data collected by NOAA's TIROS-N polar-orbiting satellites and adjusted for time-dependent biases by NASA and the Global Hydrology and Climate Center at the University of Alabama in Huntsville, indicate that temperatures in the lower half of the troposphere (lowest 8 km of the atmosphere) over the U.S. were approximately 0.2 degrees F (0.1 degrees C) above the 1979-1998 average.

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Climate Extremes Index

The U.S. Climate Extremes Index (CEI) measures the occurrence of several types of climate extremes, such as record or near-record warmth, dry spells or rainy periods. During 2010, the most prominent and wide-spread extremes occurred during two seasons: winter and summer. At the National level, the winter season ranked as the 15th coldest winter on record, while the summer ranked as the 4th warmest based on records which date back to 1895. The change in seasonal temperatures was a record in the Southeast, which experienced its 11th coldest winter and its hottest summer on record. Winter precipitation was above average across the nation with the Southwest and the Southeast ranking among the top ten wettest such periods on record. Summer ranked 9th wettest for the nation, with the bulk of the precipitation occurring in the West North Central and East North Central regions.

For the contiguous U.S. (CONUS), the spatial extent of extremes, as depicted by the CEI, was approximately 6% greater than the historical average for winter (December 2009 - February 2010). Factors contributing to the elevated 2009-2010 winter value were large footprints of cold maximum temperatures, areas of extreme wetness as denoted by the Palmer Drought Severity Index (PDSI) and an abundance of days in which precipitation fell. The seasonal wetness can also be seen in the precipitation state rank map. Regions of the country which were most significantly impacted were the Central, South and Southeast regions. More than half of the Southeast region experienced extremes in cold maximum temperatures, excessive wet conditions and large 1-day precipitation events. Approximately one-third of both the Central and South regions experienced extremes in cold maximum temperatures, excessive wetness and a large number of days with precipitation. Other regions which had prologed periods of wetness were the West North Central, East North Central and the Northeast regions.

For as cold as the winter was in the Central, South and Southeastern regions, the summer months were filled with record warmth, primarily seen in the warm minimum temperatures. Approximately 30% of the CONUS was impacted by extremes during the summer (June August), which is 10% above the average spatial extent for extremes. Much of the credit for this above average value can be attributed to warmth in both maximum and minimum temperatures as well as excessive wetness across parts of the contiguous U.S. More than half of the East North Central region experienced extremes in warm minimum temperatures, excessive wetness, large 1-day precipitation values and a large number of days with precipitation. The Southeast region sweltered under large-scale heat in both maximum and minimum temperatures, which covered nearly the entire region during the summer months. Nearly all of the Northeast, Central, Southeast, South and East North Central regions experienced extreme warm minimum temperatures during this period. The Southwest and West North Central regions had large, yet less-extensive areas which experienced warm minimum temperatures during this period. Additional areas of extreme wetness were also seen in the West North Central, Northwest and Central regions.

In 2011, the regional CEI data and graphics will be updated on a monthly basis and accessible through the CEI webpage. Please visit our main CEI webpage for national CEI data as well as updates on the timing of the release of the regional CEI products.

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NOAA's National Climatic Data Center is the world's largest active archive of weather data. The preliminary temperature and precipitation rankings are available from the center by calling: 828-271-4800.

NOAA works closely with the academic and science communities on climate-related research projects to increase the understanding of El Niño and improve forecasting techniques. NOAA's Climate Prediction Center monitors, analyzes and predicts climate events ranging from weeks to seasons for the nation. NOAA also operates the network of data buoys and satellites that provide vital information about the ocean waters, and initiates research projects to improve future climate forecasts.

Global Analysis

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Contents of this Section:

• Global Temperatures
• Regional Temperatures
• Global Precipitation
• References

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2010 Global Significant Weather and Climate Events

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Global Highlights

• For 2010, the combined global land and ocean surface temperature tied with 2005 as the warmest such period on record, at 0.62°C (1.12°F) above the 20^th century average of 13.9°C (57.0°F). 1998 is the third warmest year-to-date on record, at 0.60°C (1.08°F) above the 20^th century average.


• The 2010 Northern Hemisphere combined global land and ocean surface temperature was the warmest year on record, at 0.73°C (1.31°F) above the 20^th century average. The 2010 Southern Hemisphere combined global land and ocean surface temperature was the sixth warmest year on record, at 0.51°C (0.92°F) above the 20^th century average.


• The global land surface temperature for 2010 tied with 2005 as the second warmest on record, at 0.96°C (1.73°F) above the 20^th century average. The warmest such period on record occurred in 2007, at 0.99°C (1.78°F) above the 20^th century average.


• The global ocean surface temperature for 2010 tied with 2005 as the third warmest on record, at 0.49°C (0.88°F) above the 20^th century average.


• In 2010 there was a dramatic shift in the El Niño–Southern Oscillation, which influences temperature and precipitation patterns around the world. A moderate-to-strong El Niño at the beginning of the year transitioned to La Niña conditions by July. At the end of November, La Niña was moderate-to-strong.

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Please Note: The data presented in this report are preliminary. Ranks and anomalies may change as more complete data are received and processed. Effective with the July 2009 State of the Climate Report, NCDC transitioned to the new version (version 3b) of the extended reconstructed sea surface temperature (ERSST) dataset. ERSST.v3b is an improved extended SST reconstruction over version 2. This report uses the ERSST.v3b dataset to assess the entire year. Therefore, values for individual months of January-June presented in this report may differ slightly from those reported when ERSST.v2 was the operational dataset. For more information about the differences between ERSST.v3b and ERSST.v2 and to access the most current data, please visit NCDC's Global Surface Temperature Anomalies page.

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Global Temperatures

The year 2010 tied with 2005 as the warmest year since records began in 1880. The annual global combined land and ocean surface temperature was 0.62°C (1.12°F) above the 20^th century average. The range associated with this value is plus or minus 0.07°C (0.13°F). The 2010 combined land and ocean surface temperature in the Northern Hemisphere was also the warmest on record, while the combined land and ocean surface temperature in the Southern Hemisphere was the sixth warmest such period on record. The annual globally averaged land temperature was 0.96°C (1.73°F) above average, which tied with 2005 as the second warmest year record. The range associated with this value is plus or minus 0.11°C (0.20°F). The warmest year was 2007, at 0.99°C (1.78°F) above the 20^th century average. The decadal global land and ocean average temperature anomaly for 2001–2010 was the warmest decade on record for the globe, with a surface global temperature of 0.56°C (1.01°F) above the 20^th century average. This surpassed the previous decadal record (1991–2000) value of 0.36°C (0.65°F).

The El Niño-Southern Oscillation (ENSO) is a periodic fluctuation in sea surface temperature (El Niño) and the air pressure of the overlying atmosphere (Southern Oscillation) across the equatorial Pacific Ocean, affecting weather patterns in many parts of the world. The year began in a moderate-to-stong warm (El Niño) phase. The globally averaged January ocean surface temperature was the second warmest on record, behind 1998—a year that also began with a strong El Niño. Temperature anomalies across the equatorial Pacific declined through the year, although the ENSO warm phase offically remained through April. The global ocean surface temperatures for the period January–April were the second warmest on record, behind 1998. In May, sea surface temperature anomalies in the eastern equatorial Pacific Ocean cooled below the El Niño threshold (0.5°C), signifying a return to ENSO-neutral conditions. By July, ENSO officially shifted into a cold (La Niña) phase as the eastern equatorial Pacific Ocean continued to cool to below-average temperatures. With La Niña firmly in place, and central and eastern equatorial Pacific Ocean temperatures continuing to cool, the globally averaged ocean temperature for the period September–November was tenth warmest on record. For the period January–December, the shift from a warm phase to a cold phase ENSO contributed to a globally averaged ocean surface temperature anomaly of 0.49°C (0.88°F) above the 20^th century average, tying with 2005 as the third warmest such period on record. The range associated with this value is plus or minus 0.06°C (0.11°F). 2003 and 1998 tied for the warmest years on record, at 0.51°C (0.92°F) above average. According to NOAA's Climate Prediction Center (CPC), La Niña was expected to peak during the end of 2010 into early 2011 and last at into the Northern Hemisphere spring 2011 with a lesser intensity.

January–December	Anomaly		Rank (out of 131 years)	(Next) Warmest on Record
	°C	°F		Year	°C	°F
Global
Land	+0.96 ± 0.11	+1.73 ± 0.20	2nd warmest*	2007	+0.99	+1.78
Ocean	+0.49 ± 0.06	+0.88 ± 0.11	3rd warmest*	2003*	+0.51	+0.92
Land and Ocean	+0.62 ± 0.07	+1.12 ± 0.13	Warmest*	(1998)	+0.60	+1.08
Northern Hemisphere
Land	+1.08 ± 0.14	+1.94 ± 0.25	2nd warmest	2007	+1.15	+2.07
Ocean	+0.51 ± 0.07	+0.92 ± 0.13	3rd warmest*	2005	+0.53	+0.95
Land and Ocean	+0.73 ± 0.10	+1.31 ± 0.18	Warmest	(2005)	+0.72	+1.30
Southern Hemisphere
Land	+0.65 ± 0.06	+1.17 ± 0.11	5th warmest*	2005	+0.81	+1.46
Ocean	+0.49 ± 0.06	+0.88 ± 0.11	5th warmest	1998	+0.54	+0.97
Land and Ocean	+0.51 ± 0.06	+0.92 ± 0.11	6th warmest	1998	+0.57	+1.03

*Signifies a tie

* Global Land tied with 2005 as the 2^nd warmest year on record.
* Global Ocean tied with 2005 as the 3^rd warmest year on record.
* Global Land and Ocean tied with 2005 as the warmest year on record.
* Northern Hemisphere Ocean tied with 2003 as the 3^rd warmest year on record.
* Southern Hemisphere Land tied with 2003 as the 5^th warmest year on record.

Global Top 10 Warmest Years (Jan-Dec)	Anomaly °C	Anomaly °F
2010	0.62	1.12
2005	0.62	1.12
1998	0.60	1.08
2003	0.58	1.04
2002	0.58	1.04
2009	0.56	1.01
2006	0.56	1.01
2007	0.55	0.99
2004	0.54	0.97
2001	0.52	0.94

The 1901-2000 average combined land and ocean annual temperature is 13.9°C (56.9°F), the annually averaged land temperature for the same period is 8.5°C (47.3°F), and the long-term annually averaged sea surface temperature is 16.1°C (60.9°F).

Top Ten Global Weather/Climate Events for 2010

The following table list the top ten global weather/climate events of 2010. These events are listed according to their overall rank, as voted on by a panel of weather/climate experts. For additional information on these and other significant 2010 climate events, please visit NCDC's Top Ten Global Events webpage.

Rank	Event	When Occurred
1	Russo- European- Asian Heat Waves	Summer
2	2010 as [near] warmest on record	Calendar Year
3	Pakistani Flooding	Late July into August
4	El Niño to La Niña Transition	Mid-to-Late Boreal Spring
5	Negative Arctic Oscillation	December–February
6	Brazillian Drought	Ongoing
7-tie	Historically Inactive NE Pacific Hurricane Season	May 15th–November 30th
7-tie	Historic N. Hemispheric Snow Retreat	January through June
9	Minimum Sea Ice Extent	Mid-September
10	China Drought	First half of 2010

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Regional Temperatures

Warmer-than-average temperatures occurred during 2010 for most of the world's surface. The warmest annual above-average temperatures occurred throughout the high latitude regions of the Northern Hemisphere, Canada, Alaska, the lower North Atlantic Ocean, the Middle East, eastern Europe, and northern Africa. Temperatures were notably cooler across the Southern oceans, most of the eastern Pacific Ocean, western Scandinavia, part of central Russia, and parts of Australia.

The map, above left, is created using data from the Global Historical Climatology Network (GHCN), a network of more than 7,000 land surface observing stations. Temperature anomalies are with respect to the 1961–1990 average. The map, above right, is a product of a merged land surface and sea surface temperature anomaly analysis developed by Smith et. al (2008). For the merged land surface and SST analysis, temperature anomalies with respect to the 1971–2000 average for land and ocean are analyzed separately and then merged to form the global analysis. For more information, please visit NCDC's Global Surface Temperature Anomalies page.

The year 2010 was marked by several notable extreme temperature events. During the beginning of the year, a strong negative Arctic Oscillation—a climate pattern which allows chilly Arctic air to slide south while warmer air moves north—brought snow storms and record cold temperatures to much of the Northern Hemisphere, including eastern North America, Europe, and Asia. Polar air reached far into the deep southern U.S. during January and February. The record cold weather caused ocean temperatures in the Florida Keys to drop below 15°C (59°F), bleaching and killing coral reefs, which cannot survive the sustained cool water temperature. Area coral experts reported that they had not seen a bleaching of this magnitude due to cold temperatures since the winter of 1977/78. According to the United Kingdom (UK) Meteorological Office, the UK experienced its coldest winter (December 2009–February 2010) since 1978/79. In contrast, warm air moving northward into Canada brought the country its warmest winter since records began in 1948. Among Canada's climate regions, the Arctic Tundra, Arctic Mountain and Fjords, and the Northwestern Forest all had their warmest winter on record. In the Southern Hemisphere, according to Australia's Bureau of Meteorology (BoM), the country experienced its warmest summer (Northern Hemisphere winter) on record, with average temperatures 0.2°C (0.4°F) higher than the previous record set during the summer of 1997/98.

Several exceptional heat waves occurred during 2010, bringing record high temperatures and affecting tens of millions of people. Warm conditions were present across India during April. On the 18^th, Delhi recorded its warmest April temperature since 1958 when temperatures soared to 43.7°C (110.7°F). Another heat wave baked northern India and Pakistan at the end of May. According to the Pakistan Meteorological Service, a maximum temperature of 53.5°C (128.3°F) was recorded in Mohenjo-Daro on May 26^th. This was the warmest temperature ever recorded in Pakistan and the warmest temperaure recorded in Asia since 1942. In mid-June, a strong blocking pattern settled over western Russia, bringing an unprecendented two-month long heat wave to the area. On July 29^th, the Moscow Observatory recorded its highest-ever temperature—38.2°C (100.8°F), breaking the previous record of 37.2°C (98.9°F) set just four days earlier. Prior to 2010, the hottest temperature in Moscow was 36.8°C (98.2°F), recorded 90 years ago. That same day, Finland recorded its highest ever temperature as the mercury reached 37.2°C (99.0°F) in Joensuu, breaking the old record set in Turku in July 1914 by 1.3°C (2.3°F). The massive heat wave brought Russia its warmest summer (June–August) on record. At least 15,000 deaths in Russia were attributed to the heat.

Extreme summer warmth was felt in other areas around the world as well. According to the the Beijing Climate Center, China experienced its warmest summer on record since 1961. And the Japan Meteorological Agency reported that the country had its warmest summer since records began in 1898. On average, temperatures across Japan were 1.64°C (2.96°F) greater than the 1971–2000 average. According to Environment Canada, Canada had its third warmest summer since national records began in 1948, behind 1998 (warmest) and 2006 (second warmest). In fact, the January–August period was Canada's warmest such period on record. In contrast, Australia experienced its coolest winter (Northern Hemisphere summer) in 13 years.

In September, following on the heels of its second coolest summer on record, a scorching heat wave in part of the western U.S. brought downtown Los Angeles, California its highest ever recorded temperature on the 27^th. A temperature of 45°C (113°F) was recorded, breaking the old record of 44.4°C (112°F) set on June 26^th, 1990.

Similar to the beginning of the year, December was marked by a strong negative phase of the Arctic Oscillation. According to the UK Met Office, during the month of December, the UK was, on average, about 9°F (5°C) below the 1971–2000 average, making it the coldest December in more than 100 years. It was also the coldest month recorded since February 1986. The United States as a whole experienced its seventh snowiest December on record, while the Southeast had its 3^rd coldest December on record. The negative Arctic Oscillation also contributed to the lowest December Arctic sea ice extent on record, according to the National Snow and Ice Data Center. The low sea ice conditions occurred in regions where the ice coverage would typically expand this time of year; however, above-normal temperatures were recorded in these areas. ENSO also impacted temperature patterns toward the end of 2010. According to the Bureau of Meteorology, La Niña influenced the precipitation patterns over Australia during the latter part of the year. Heavy rainfall across the country brought cooler temperatures, leading to the country's fourth coolest spring (September–November; Northern Hemisphere fall) on record. Nationally averaged maximum temperatures were 1.23°C (2.21°F) below normal, the lowest since 1999. December brought even cooler anomalies to the country. The average temperature for the month was 1.35°C (2.43°F) below normal, the second coolest December on record, behind 1999. Overall, it was the coolest year for Australia since 2001, but was still 0.19°C above the 1961–1990 average. On a decadal scale, the years 2001–2010 were the warmest decade on record for the country.

The Finnish Meteorological Institute reported that 2010 was Finland's coolest year on record since 1987, at 0.6°C below average. The Institute also reported that the decade 2001–2010 was warmer than the preceding decades for the country, with records dating back to the 1840s. The average temperature for this decade was 0.30°C above the 1930s average, Finland's next warmest decade. In addition, the temperatures for each season (three-month period) averaged over the decade was among the two warmest such seasons within the past 160 years, with the winter warming the most.

According to the India Meteorological Department (IMD), India's 2010 mean annual temperature was 0.93°C (1.67°F) above the 1961–1990 average—resulting in the warmest year since national records began in 1901. It was also reported that the decade 2001–2010 was India's warmest decade on record, with an anomaly of 0.4°C (0.7°F)—surpassing the previous decadal record set in 1991–2000 by 0.2°C (0.4°F).

Most of Canada experienced above-average temperatures throughout the year. According to Environment Canada, Canada experienced its warmest winter (December–February) and spring (March–May) on record during 2010. The national average temperature during summer (June–August) 2010 and autumn (September–November) 2010 was the third and second warmest, respectively, since national records began in 1948. Overall, the national average temperature for Canada during 2010 was 3°C (5°F) above the 1961–1990 average, ranking 2010 as the warmest year on record since national records began in 1948.

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Global Precipitation

Global precipitation in 2010 was well above the 1961–1990 average, ranking as the wettest on record since 1900. Precipitation throughout the year was variable in many areas. Regionally, drier than average conditions were widespread across much of French Polynesia, the Solomon Islands, Hawaiian Islands, northwestern Canada, extreme northwest and northeast Brazil, and southern Peru. The wettest regions induded most of Central America, much of India, southwestern China, east Asia, Borneo, and parts of Australia.

El Niño and La Niña, monsoonal rains, and tropical storms played large roles in some of the extreme precipitation patterns observed during the 2010 year-to-date. During the year, numerous tropical cyclones brought copious amounts of rain to various regions around the world, including northern Australia, southern and eastern Asia, Mexico, and most of Central America. Please visit NCDC's Global Hazards and Hurricanes & Tropical Storms web pages for more detailed information about specific storms.

Canada experienced its driest winter (December 2009–February 2010) since national records began in 1948, with 22 percent below-average precipitation. According to Environment Canada, many locations across Ontario, Canada received no snow or traces of snow during March 2010, setting new low snowfall records. Toronto City, which typically receives 22 cm (8.7 inches) of snow during March recorded no snow this year. This broke the low snowfall record which dates as far back as 1898. To the west, Alaska had its third driest January on record since 1918.

Following its driest February and March on record, drought was declared for Auckland, New Zealand and surrounding areas. Dry conditions continued in New Zealand as the country as a whole experienced autumn (March–May; Northern Hemisphere spring) precipitation that was 50–80 percent below average.

The first half of 2010 was dry in parts of Europe as well. According to the UK Meteorological Office, the United Kingdom experienced its driest January–June period since 1953 and the second driest since 1929, receiving only 361 mm (14.2 inches) of precipitation. This is almost 30 percent below the long-term average of 512 mm (20.1 inches).

Near the end of July, the same blocking pattern that brought Russia its record-breaking heatwave contributed to a heavy deluge of rainfall in Pakistan. Over 300 mm (12 inches) of rain fell from July 28^th–30^th in Peshawar province, leading to extreme flooding that eventually submerged approximately 20 percent of the country. An official of the Pakistani government reported the flooding was the worst since 1929. At least 1,500 people were killed due to flooding and landslides. Heavier-than-normal monsoon rains continued into September, affecting both Pakistan and India. Conversely, Bangladesh had its driest monsoon season since 1994.

A series of strong storms brought heavy rainfall to northeastern China and North Korea during August. Subsequent flooding was said to be the worst in that region in more than a decade. Heavy monsoon rains affected Vietnam, Thailand, and southeastern China in October. Thailand reportedly suffered its worst floods in decades.

By October, Brazil's north and west Amazonia was in the midst of one of its worst droughts in 40 years. The Rio Negro—one of the most important tributaries of the Rio Amazonia—fell to its lowest level since record keeping began in 1902.

La Niña brought record rainfall to most of Australia toward the end of the year. The country had its wettest spring (September–November; Northern Hemisphere fall) on record. Nationally averaged rainfall was 163.0 mm, which was 125 percent above normal for the period. However, it is noted that in contrast to the rest of the country, southwestern Western Australia had its driest spring on record. With continued extreme wetness in December—particularly in the northeastern state of Queensland, which had its wettest December on record and experienced major flooding—the average precipitation for December was 99 percent above normal, ranking as Australia's second wettest on record, behind December 1975. For the year, 2010 was the country's third wettest since records began in 1900 and the wettest sonce 2000. Southwest Western Australia reported its driest year on record.

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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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National Snow & Ice

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Much of the United States experienced a record breaking 2009–2010 winter. Long–standing monthly and seasonal snowfall records were shattered and record cold temperatures were set over the eastern two-thirds of the nation. According to 44 years of satellite data analyzed by the NOAA supported, Rutgers Global Snow Lab, a new monthly snow cover extent record was set during December 2009. This was partially due to snow falling across the Southern Plains, Gulf Coast, and the Southeast — regions which do not typically receive much December snowfall. Persistent cold and snow across much of the country during January and February was associated with those months ranking in their top ten largest snow cover extents for the U.S. — January was 6^th largest and February 3^rd largest. A far–reaching storm the second week of February brought snow to the Deep South, and every state in the U.S. had snow on the ground, including Florida and Hawaii. More information on the 2009–2010 winter can be found in the 2009–2010 Cold Season Special Report. As the season transitioned into spring, conditions were almost the complete opposite of the winter, with low snow cover extents reported across the United States during April (8^th smallest) and May (10^th smallest). The low spring snow cover extent was driven by anomalously warm conditions over the regions which had experienced the heavy snow during the December–February period.

Winter and spring mountain snowpack provide a crucial water source across much of the western United States. The total annual water budget for agriculture and human use in the mountainous West is based upon the amount of snow melt that will occur in spring and is proportional to the amount of snow on the ground. The annual snowpack typically reaches its maximum values at the end of March. During the 2009–2010 Cold Season, the West generally experienced much–below average snowpacks. Mountain snowpack in the Pacific Northwest was less than 25 percent of normal in several locations. The pattern was evident in the high-elevation station (SNOTEL) network, especially in maps of the end-of-March snowpack and snow water content. Some individual SNOTEL stations in the northern Rockies had early April snow water equivalent in the driest fifth percentile of the historical record (95 percent of the years for this date were wetter). Conversely, the snowpack was much above average in Arizona, New Mexico, and southern Utah.

In October, the cold season returned as well as snowy conditions across the United States. During October, the U.S. experienced near average snow cover extent, while strong storms across the northern tier of the U.S. during November led to widespread snowfall. The U.S. experienced its fourth largest November snow cover extent on record.

Select 2009–2010 Cold Season Snowfall Records

The numerous snow storms affecting the country during the late 2009 and early 2010 led to hundreds of record snowfall accumulations. Many of the records broken were along the densely-populated Northeast corridor. Provided is a table of select seasonal snowfall records. Please visit NCDC U.S. Records for additional information.

City, State	Amount	Previous Record, Date
Washington, District of Columbia–Dulles	73.2 inches (185.9 cm)	61.9 inches (157.2 cm), 1995–1996
Washington, District of Columbia–Reagan	56.0 inches (142.2 cm)	54.4 inches (138.2 cm), 1898–1899
Baltimore, Maryland	80.4 inches (204.2 cm)	62.5 inches (158.8 cm), 1995–1996
Philadelphia, Pennsylvania	78.7 inches (199.9 cm)	65.5 inches (166.4 cm), 1995–1996
Wilmington, Delaware	72.7 inches (184.7 cm)	55.9 inches (142.0 cm), 1995–1996
Atlantic City, New Jersey	58.1 inches (147.6 cm)	46.9 inches (119.1 cm), 1966–1967
Beckley, West Virginia	132.9 inches (337.6 cm)	100.1 inches (254.6 cm), 1995–1996
Wichita Falls, Texas	16.6 inches (42.2 cm)	14.3 inches (36.3 cm), 1957–1958

Select Significant Events

A strong storm developed on December 4^th 2009 over the Gulf of Mexico, while arctic air was moving in behind an upper level trough. This combination led several locations in the Gulf Coast region to receive their earliest accumulating snowfall. Houston, Texas received 1.0 inch (2.5 cm), Lake Charles, Louisiana observed 0.2 inches (0.5 cm), and Lafayette, Louisiana measured 0.3 inches (0.8 cm). The previous earliest snowfall records for this area occurred the previous year on December 11^th, 2008 when a similar weather situation occurred.

A major winter storm of December affected the Mid-Atlantic and Northeast on December 18^th–21^st 2010, leaving behind 1–2 feet (30.5 cm–61.0 cm) of snow from North Carolina to New England. The storm at one point was over 500 miles (800 km) in width, eventually affecting 14 states and tens of millions of Americans. The heavy snow crippled the densely populated corridor from Richmond, Virginia to Boston, Massachusetts. Reagan National Airport in Washington, DC experienced its largest calendar day snowfall acumulation on record with 15.0 inches (38.1 cm). The storm was given a preliminary score of Category 3 on the Northeast Snow Impact Scale (NESIS), categorizing the storm as 'Major' and ranking it in the top 25 winter storms to affect the region.

Another major winter storm during December presented a huge part of the country with a white Christmas. The large storm produced blizzard conditions from Texas to the U.S.–Canadian border on December 24^th–27^th 2010. Dallas, Texas observed its first Christmas Eve snowfall on record. The storm was associated with the most snowfall to affect Oklahoma City, Oklahoma in a 24-hour period (14.1 inches or 35.8 cm) and was the second biggest storm accumulation for Sioux City, South Dakota on record (20.7 inches or 52.6 cm). The storm left travelers stranded in airports and on highways, as many people were in transit for the holiday season.

On February 4^th a storm that originated in the southwest U.S. traversed eastward, pumping in moisture from the Gulf of Mexico and the Atlantic. Some locations in Maryland, Pennsylvania, Virginia, and West Virginia recorded more than 30 inches (76 cm) of snow. In Washington, DC (Reagan National Airport), the two-day total of 32.4 inches (82.3 cm) ranked as the highest total storm amount in history. In Philadelphia, the 28.5 inches (72.4 cm) ranked as the second highest amount, behind the 30.7 inches (78.0 cm) received on January 7^th–8^th, 1996. The 25.0 inches (63.5 cm) that fell in Baltimore was its third highest storm total amount since official records began in 1891.

Another blizzard created havoc during February 9^th–11^th on the areas that were still digging out from previous storms. This powerful Nor'easter produced as much as 14 inches (35.6 cm) of snow in the Washington, DC area, 17 inches (43.2 cm) in New Jersey, 20 inches (50.8 cm) in Baltimore, as much as 24 inches (61.0 cm) in northern Maryland, and more than 27 inches (68.8 cm) in Pennsylvania. As a result of these two storms, several locations broke seasonal snowfall records, some of which were more than a century old.

On February 11^th–13^th, as much as 6 inches (15 cm) of snow fell in Louisiana, Alabama, Mississippi, and even the northwest Panhandle of Florida. The largest daily accumulation on record fell in Dallas, Texas. The Dallas/Fort Worth National Weather Forecast office reported that 11.2 inches (28.4 cm) bested the old record of 7.8 inches (19.8 cm) set on January 15^th, 1964 and January 14^th, 1917. On February 13^th every contiguous U.S. state had snow on the ground.

A strong storm brought heavy snowfall from the Rocky Mountain Front Range across the Southern Plains on March 19^th–22^nd, creating a white start to the beginning of spring. The snowfall, coupled with strong winds, caused near-blizzard conditions in Oklahoma, Texas, Arkansas, and Missouri. The storm brought over 20 inches (51 cm) of snow to portions of Wyoming, Colorado, and New Mexico. Accumulations over 10 inches (25 cm) were common across the rest of the Southern Plains, with portions of Missouri, Kansas, and Arkansas receiving over a foot (30 cm) of snow. This storm also topped off a very snowy season for the region. Oklahoma City, Oklahoma had its fifth snowiest winter with 23.3 inches (59.2 cm) of snowfall, and Wichita Falls, Texas had its snowiest season with 16.6 inches (42.2 cm).

Tornadoes

Issued: 10 January 2011

According to the Storm Prediction Center (SPC), the final tornado count for the U.S. during 2010 was 1,282. The final 2010 count ranks as the seventh most acive year since records began in 1950. During 2010, seven months experienced above to much–above normal tornado counts — January, April, May, June, July, October, and November.

During 2010, tornadoes were reported in all but four states in the Lower 48 — Delaware, Massachusetts, Rhode Island, and Nevada. Tornadic activity during the year tended to occur in clusters, with the most active regions including the Front Range of the Rockies, the Southeast, the Central and Northern Plains, and the Great Lakes.

Two states in particular had very active tornado years. Arizona had 17 preliminary tornado reports during 2010, tying the state’s annual record, which was set in 1972. The second most tornadoes occurred in 1992 with 13 reports. Eight of the tornadoes occurred on October 6^th, marking the most tornadoes to strike in Arizona during a calendar day since records began in 1950. Arizona on average receives four tornadoes annually. The other state with above–normal tornado activity was Minnesota. The state experienced 113 tornadoes during 2010, the most of any state in the country this year, and the most the state has experienced on record. The 2010 tornado count surpassed the previous record which was 74 set in 2001. The annual tornado average for the state is 25. The most active day for the state was June 17^th, when 48 tornadoes were confirmed. This bested Minnesota's previous one day tornado count set on June 16, 1992 when 27 tornadoes were confirmed. Minnesota was also the national tornado leader, for the first time on record.

During 2010, there were 44 fatalities directly related to tornadoes across the U.S. during 2010. The count is higher than the 22 reported during 2009, which also had fewer tornadoes. The 2000-2009 average for annual tornado–related fatalities is 62. The deadliest tornado of the year occurred on April 24^th, when 10 people were killed in Mississippi. More information on this tornado can be found in the April State of the Climate tornado report.

On June 17^th, there were at least 74 confirmed tornadoes reported across the Upper Midwest and Northern Plains, marking the most active tornado day of 2010. This ranks the event as the 17^th most active day on record for the U.S., and the largest event since May 23^rd, 2008. The time of year for the outbreak was also unusual. This event was the second highest number of tornadoes during a single event during meteorological summer (June–August) on record, behind June 24, 2003. Forty–eight of those tornadoes occurred in Minnesota, helping the state break its annual tornado record. Tornadoes were also reported in North Dakota, Iowa, and Wisconsin. There were four EF–4 tornadoes for this event, which is unusual for the region. According to information from the National Weater Service offices in Grand Forks, North Dakota and the Twin Cities, Minnesota the previous EF–4 or stronger tornado in Minnesota occurred on July 25^th, 2000, and the outbreak marked the most EF–4s or stronger in any single event in Minnesota since April 1967. For the entire nation, this was the first time that an outbreak produced four EF–4s since the “Super Tuesday” outbreak of February 2008. There were three deaths reported across the region during the outbreak. This outbreak was associated with one of the most active tornado days in the U.S. during the past 10 years, and was the worst tornado outbreak to occur across the Northern Plains and western Great Lakes in decades.

A storm system moving through the center of the country brought a severe weather outbreak to the middle and lower Mississippi River Valley on December 31^st. Fifty-three tornadoes were preliminarily reported across Arkansas, Missouri, Illinois, Louisiana, and Mississippi, marking the 5^th most active tornado day during 2010. Four fatalities were reported in Arkansas, and four were reported in Missouri. A tornado outbreak this large during the month of December is uncommon — the 1980-2009 December monthly average tornado count is 23. The current record for the number of confirmed tornadoes during a single day during December is 34, which occurred on December 18^th, 2002. Once the tornado count is confirmed, it is likely that this outbreak will rank as the largest single-day December outbreak on record. There were three EF-3 tornadoes confirmed with the outbreak — one near Macon, Mississippi; one near Sunset Hills, Missouri; and one near Cincinnati, Arkansas. An EF-1 tornado hit near downtown St. Louis, but no significant injuries were reported there.

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Hurricanes & Tropical Storms

• Atlantic Basin
• Pacific Basin

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Atlantic Basin

2010 Season Summary:

The 2010 North Atlantic hurricane season was extremely active with 19 named storms, 12 hurricanes, and five major hurricanes. The 2010 season ties with 1887 and 1995 for third most named storms on record and tied with 1969 for second most hurricanes. The years 2005 and 1933 had more named names, while only 2005 had more hurricanes. The basin on average experiences 11 named storms, six hurricanes, and two major hurricanes during a season. Only one tropical storm and no hurricanes made landfall in the U.S., despite the active season. This marks the second consecutive season with no U.S. landfalling hurricane and only the 14^th time on record that no hurricanes made landfall in the United States. The last time there were two consecutive seasons without a U.S. hurricane landfall was 2000 and 2001. This is the first time that no hurricanes made landfall during such an active season.

The Accumulated Cyclone Energy (ACE) index was 169x10⁴ knots² for the 2010 North Atlantic hurricane season, which is much above average. This value is 11^th largest since 1948 and about 190 percent of the 1951–2000 median value. A "hyperactive season" is defined by having a seasonal ACE value greater than 183 percent of the median. The relatively lower ACE value compared to the number of storms is due to the lack of any Category 5 hurricanes during the season. According to the National Hurricane Center (NHC), the above average ACE value and number of storms were attributable to record warm Atlantic waters, combined with the favorable winds coming off Africa and weak wind shear aided by La Niña. The jet stream’s position contributed to warm and dry conditions in the eastern U.S. and acted as a barrier that kept many storms over open water. Also, because many storms formed in the extreme eastern Atlantic, they curved out to sea without threatening land due to the North Atlantic (Bermuda) High.

Although Bonnie was the only tropical storm to affect the continental U.S., other countries along the western Atlantic were not spared. Alex, Hermine, Karl, Nicole, Matthew, Paula, and Richard, all directly impacted Mexico and Central America bringing flooding rains and strong winds. Hurricane Otto brought torrential rainfall to Puerto Rico, while Tomas left over 40 dead in St. Lucia and Haiti. The remnants of Hurricane Igor made landfall in eastern Canada, and was the most costly storm to ever impact Newfoundland. Tropical storms and hurricanes killed more than 250 people in the Caribbean and Central America this season. The deadliest storms were Tropical Storm Matthew, Hurricane Tomas and Hurricane Alex. More information on individual storms can be found in the monthly Tropical Cyclone report and the Global Hazards report.

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East Pacific Basin

2010 Season Summary:

While the North Atlantic was having one of its busiest tropical cyclone seasons on record, the Eastern Pacific had a record quiet season. During the 2010 season, the Eastern Pacific experienced seven named storms, three hurricanes, and two major hurricanes. According to the NHC, this is the fewest named storms (previous record low was eight in 1977) and the fewest hurricanes (previous record low was four in 1969, 1970, 1977 and 2007) on record since the satellite era began in the mid-1960s. On average, the eastern North Pacific season produces 15 named storms, nine hurricanes and four major hurricanes.

June was the busiest month in the East Pacific basin; four tropical cyclones developed, one became a tropical storm, and two became major hurricanes. Hurricane Celia became a rare June Category 5 storm. The ACE index for the entire season was 50x10⁴ knots², marking the second lowest ACE on record for the basin, behind 1977 which had an ACE index of 22x10⁴ knots² . The extremely strong Hurricane Celia, which had maximum sustained winds ofh 160 mph (260 km/h) and an estimated central pressure of 921 mb, helped to increase the season ACE value above 1977 levels. According to the NHC, the record low activity was attributable to La Niña and the cooler sea surface temperatures and increased wind shear across the basin.

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Drought

Global Snow & Ice

Issued: 10 January 2011

Sea Ice Extent

Arctic sea ice extent, which is measured from passive microwave instruments onboard NOAA satellites, usually expands during the cold season to a March maximum, then contracts during the warm season to a September minimum. According to the NOAA supported National Snow and Ice Data Center, the maximum Arctic sea ice extent during 2010 occurred on March 31^st — the latest date for the maximum sea ice extent since records began in 1979. The previous record for latest date was set on March 29^th, 1999. On March 31^st the maximum extent was 15.25 million square km (5.9 million square miles). This was 670,000 square kilometers (260,000 square miles) above the record low maximum extent, which occurred in 2006.

According to the NSIDC, the minimum Arctic sea ice extent during 2010 occurred on September 19^th, at 1.78 million square miles (4.6 million square km) marking the third smallest extent on record. The 2010 annual minimum extent was 14,000 square miles (37,000 square km) larger than the minimum extent in 2008 and 181,000 square miles (470,000 square km) larger than the minimum extent in 2007. According to the National Ice Center, both the Northwest Passage and the Northern Sea Route were ice free during September. This is the first time in modern history that both Arctic Sea routes have been open for navigation. The monthly average Arctic ice extent during September was 1.89 million square miles (4.9 million square km). The monthly extent was 30.4 percent below the 1979–2000 average and ranked as the third smallest September Northern Hemisphere sea ice extent in the satellite record, behind 2007 (lowest) and 2008 (second lowest). An additional NOAA animation of the 2010 Arcitc sea ice minimum can be found at NOAA's Environmental Visualization Laboratory.

Sea ice conditions in the Antarctic were significantly different than conditions across the Arctic during 2010. The Antarctic sea ice extent usually expands during the cold season to a September maximum, then contracts during the warm season to a March minimum. Unlike the two previous years which were above average, the March 2010 Southern Hemisphere sea ice extent was 6.9 percent below the 1979–2000 average. This was the eighth smallest sea ice extent in March. By September, the Antarctic sea ice had grown significantly compared to the minimum extent in March. The September extent was 7.4 million square miles (19.16 square km) and was the third largest September extent on record behind 2006 and 2007.

For further information on the Northern and Southern Hemisphere snow and ice conditions, please visit the NSIDC News page, provided by NOAA's National Snow and Ice Data Center (NSIDC).

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NH Snow Cover Extent

Analyses of NOAA data were provided by the Global Snow Laboratory, Rutgers University. Period of record is 1967-2010 (44 years).

The time series to the right shows the mean Northern Hemisphere snow cover extent for winter 2009-2010 (Dec–Feb) was much above average, and the second largest extent in the 44–year period of record. The seasonal average extent of 47.5 million square km (18.3 million square miles) was 2.4 million square km (0.9 million square miles) above the long term average. The largest Northern Hemisphere winter snow cover extent occurred during the 1977–1978 winter season. More information on individual Northern Hemisphere snow storms can be found in the Global Hazards report.

Across North America during the 2009–2010 winter, snowfall was widespread. Snow fell in all 48 states of the contiguous United States. This contributed to the North American snow cover extent for the 2009-2010 winter season being the largest in the 44–year satellite record. The seasonally–averaged snow extent of 18.3 million square km (7.1 million square miles) was 1.3 million square km (500,000 square miles) above the long term average — nearly twice the size of the state of Texas. Please see the U.S. Cold Season Special Report for more information on the winter season across the United States.

In Eurasia, snow cover extent during the 2009–2010 winter was 29.2 million square km (11.3 million square miles), which is also above average. The snow cover extent was 1.1 million square km (425,000 square miles) above the long–term average, ranking as the fourth largest winter extent on record.

The spring of 2010 brought very different conditions to the Northern Hemisphere than did the winter and that is represented by the changes in the snow cover extent, which was much below average — fourth smallest spring snow cover extent on record. The spring snow cover extent was 2.1 million square km (810,000 square miles) below average. This was the 7^th consecutive spring with below average snow cover extent for the hemisphere, and only three springs since 1990 have had above average snow cover extent.

Across North America, spring was also significantly different than the winter. The spring snow cover extent was 11.2 million square km (4.3 million square miles) — 1.5 million square km (580,000 square miles) below the long term average. This value ranked as the smallest spring snow cover extent in the 44–year period of record. This is in contrast to the largest winter snow cover extent on record just months prior.

The spring Eurasian snow cover extent was also smaller than normal during 2010 at 0.6 million square km below average (230,000 square miles). Spring 2010 ranked as the 14^th smallest (31^st largest) Eurasian snow cover extent in the 44–year period of record.

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Upper Air

Upper Air Highlights

• For the period January–December 2010, radiosonde measurements indicate that global mid-troposphere temperatures were 0.78°C (1.40°F) above the 1971–2000 mean—the warmest since records began in 1958.
• Remote Sensing Systems satellite analyses report mid-troposphere warming at a rate of 0.09°C (0.17°F) per decade. When these analyses are adjusted to remove stratospheric influence, the trend increases to 0.16°C (0.28°F) per decade.
• University of Alabama Huntsville satellite analyses report mid-troposphere warming at a rate of 0.05°C (0.09°F) per decade. When these analyses are adjusted to remove stratospheric influence, the trend increases to 0.12°C (0.21°F) per decade.
• For the lower stratosphere, the period January–November 2010 was the 18^th consecutive such period with a below-average temperature anomaly (-0.41°C; -0.74°F)—the 19^th coolest since satellite records began in 1979.

Temperature Trends

During the past century, global surface temperatures have increased at a rate near 0.07°C/decade (0.13°F/decade), but this trend has increased to a rate of approximately 0.17°C/decade (0.31°F/decade) during the past 30 years. There have been two sustained periods of warming, one beginning around 1910 and ending around 1945, and the most recent beginning about 1976. Temperatures during the latter period of warming have increased at a rate comparable to the rates of warming projected to occur during the next century with continued increases of anthropogenic greenhouse gases.

Temperature measurements have also been made above the Earth's surface over the past 53 years using balloon-borne instruments (radiosondes) and for the past 32 years using satellites. These measurements support the analyses of trends and variability in the troposphere (surface to 10-16 km) and stratosphere (10-50 km above the earth's surface).

The best source of upper air in-situ measurements for studying global temperature trends above the surface is the Radiosonde Atmospheric Temperature Products for Assessing Climate (RATPAC) dataset.

Data collected and averaged between the 850–300 mb levels (approximately 5,000 to 30,000 feet above the surface) indicate that 1958–2010 global temperature trends in the middle troposphere are similar to trends in surface temperature; 0.13°C/decade (0.23°F/decade) for surface and 0.16°C/decade (0.29°F/decade) for mid-troposphere. Since 1976, mid-troposphere temperatures have increased at a rate of 0.18°C/decade (0.32°F/decade). For 2010, global mid-troposphere temperatures were 0.78°C (1.40°F) above the 1971–2000 mean—the warmest on record.

Since 1979, NOAA's polar orbiting satellite measurements have also been used to measure temperatures in the troposphere and stratosphere. Microwave Sounding Unit (MSU) data are analyzed for NOAA by the University of Alabama in Huntsville (UAH), Remote Sensing Systems (RSS, Santa Rosa, California) and the University of Washington (UW). These observations show that the global average temperature in the middle troposphere (the layer which is centered at an altitude of 2 to 6 miles, but which includes the lower stratosphere) has increased, though differing analysis techniques have yielded similar but different trends (see below).

In all cases these trends are positive. The analysis performed by RSS reveals a trend of 0.09°C/decade (0.17°F/decade) while the UAH analysis reveals a lower trend of 0.05°C/decade (0.09°F/decade). When adjusted by University of Washington scientists to remove the stratospheric influences from the RSS and UAH mid-troposphere average, the trends increase to 0.16°C/decade (0.28°F/decade) and 0.12°C/decade (0.21°F/decade), respectively. (A journal article is available that describes the University of Washington adjustments to remove the stratospheric influence from mid-troposphere averages.) Trends in these MSU time series are similar to the trend in global surface temperatures, which increased at a rate near 0.16°C/decade (0.29°F/decade) during the same 32-year period.

While middle tropospheric temperatures reveal an increasing trend over the last three decades, stratospheric temperatures (14 to 22 km / 9 to 14 miles above the surface) have been below average since the warming effects from the 1991 Mt. Pinatubo eruption dissipated in 1993. January-November 2010 was the 18^th consecutive year with below-average temperatures (an anomaly of -0.41°C/-0.74°F), the 19^th coolest year on record. The below-average stratospheric temperatures are consistent with the depletion of ozone in the lower stratosphere and the effects of increasing greenhouse gas concentrations. The large temperature increase in 1982 is attributed to the volcanic eruption of El Chichon, and the increase in 1991 was associated with the eruption of Mt. Pinatubo in the Philippines.

References

Christy, John R., R.W. Spencer, and W.D. Braswell, 2000: MSU tropospheric Temperatures: Dataset Construction and Radiosonde Comparisons. J. of Atmos. and Oceanic Technology, 17, 1153-1170.

Free, M., D.J. Seidel, J.K. Angell, J. Lanzante, I. Durre and T.C. Peterson (2005) Radiosonde Atmospheric Temperature Products for Assessing Climate (RATPAC): A new dataset of large-area anomaly time series, J. Geophys. Res., 10.1029/2005JD006169.

Free, M., J.K. Angell, I. Durre, J. Lanzante, T.C. Peterson and D.J. Seidel(2004), Using first differences to reduce inhomogeneity in radiosonde temperature datasets, J. Climate, 21, 4171-4179.

Fu, Q., C.M. Johanson, S.G. Warren, and D.J. Seidel, 2004: Contribution of stratospheric cooling to satellite-inferred tropospheric temperature trends. Nature, 429, 55-58.

Lanzante, J.R., S.A. Klein, and D.J. Seidel (2003a), Temporal homogenization of monthly radiosonde temperature data. Part I: Methodology, J. Climate, 16, 224-240.

Lanzante, J.R., S.A. Klein, and D.J. Seidel (2003b), Temporal homogenization of monthly radiosonde temperature data. Part II: trends, sensitivities, and MSU comparison, J. Climate, 16, 241 262.

Mears, CA, FJ Wentz, 2009, Construction of the RSS V3.2 lower tropospheric dataset from the MSU and AMSU microwave sounders. Journal of Atmospheric and Oceanic Technology, 26, 1493-1509.

Mears, CA, FJ Wentz, 2009, Construction of the Remote Sensing Systems V3.2 atmopsheric temperature records from the MSU and AMSU microwave sounders. Journal of Atmospheric and Oceanic Technology, 26, 1040-1056.

Mears, Carl A., M.C. Schabel, F.J. Wentz, 2003: A Reanalysis of the MSU Channel 2 tropospheric Temperature Record. J. Clim, 16, 3650-3664.

Wildfires

Issued: 10 January 2011

During 2010, the western climate regions as well as the northern tier of the country had above average precipitation, while temperatures tended to be near–normal to above–normal for all climate regions except for the Southeast. The wet and cool conditions across the West, particularly during spring and summer limited the number of large wildfires during the typical wildfire season. Wet conditions during summer and early autumn throughout the Plains also limited the number of large fires there. The exceptionally wet conditions also helped eradicate drought for almost the entire contiguous United States.

Through December 30^th, the nationwide number of fires year–to–date was 71,839 which burned 3.42 million acres (1.4 million hectares), with an average of 47.6 acres (19.3 hectares) per fire. Every month during 2010 experienced below average acreage burned. The wet conditions contributed to 2010 having the least acreage burned annually since 1998, and the 9^th least (18^th greatest) acres burned annually since reliable records began in 1985. The number of fires during 2010 was also below average across the country. Although the amount of land burned and the number of new fires was limited, there were several high profile wildfires which caused considerable damage.

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Significant Events during 2010

The Long Butte Fire near Hagerman, Idaho burned approximately 306,113 acres (123,880 hectares) over the course of a week. The fire began on August 21^st due to a lightning strike and spread rapidly across the grasslands — an estimated 215,000 acres (87,000 hectares) burned on August 23^rd alone. A cold front moving across the region brought dry conditions and strong winds, which fueled the rapid growth. A wind gust of 70 mph (113 km/hr) was measured nearby in Boise. The fire was fully contained by August 29^th. The burn area included the home range of a wild horse herd and about 75 percent of the Hagerman Fossil Beds National Monument. The Long Butte Fire was the largest fire observed in the U.S. during 2010. The second largest fire to–date was the Tolkat 2 Fire in Alaska, which burned 188,807 acres (76,407 hectares) in May and June.

The Fourmile Canyon Fire in Boulder, Colorado was the costliest fire in Colorado’s history. The fire was ignited on September 6^th when a home fire pit was not properly extinguished. Very windy conditions spread the fire rapidly, and it burned 6,181 acres by the time it was fully contained on the 13^th. The blaze destroyed 166 homes and three other structures. Over 2,000 people in Boulder were forced to evacuate their homes. Nearly 1,000 firefighters were called to the scene to help get the fire under control. In seven days, the fire caused over $217 million in damages and cost another $9.5 million to contain.

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Additional Wildfires Links

• NOAA Fire Products
• NOAA Fire Imagery
• NOAA Economics
• U.S. Drought Monitor
• National Interagency Fire Center
• U.S. Forest Service Fire Maps
• Wildland Fire Assessment System
• InciWeb
• Alaska Interagency Coordination Center
• Canadian Interagency Forest Fire Center