Climate Change

		Departure of temperature from average for last month (updated by the 17th of each month) from the National Climatic Data Center.
		Average June arctic sea ice coverage as observed by satellites between 1979 and 2010. Image credit: National Snow and Ice Data Center.

June 2010 was the warmest June since record keeping began in 1880, according to the National Oceanic and Atmospheric Administration's (NOAA's) National Climatic Data Center (NCDC), and was the fourth consecutive warmest month on record. NASA's Goddard Institute for Space Studies rated June 2010 the third warmest June on record, behind June 1998 and June 2009. Both NOAA and NASA rated the year-to-date period, January - June, as the warmest such period on record. June 2010 global ocean temperatures were the fourth warmest on record, while land temperatures were the warmest on record. Global satellite-measured temperatures for the lowest 8 km of the atmosphere were the 2nd warmest on record in June, according to both the University of Alabama Huntsville (UAH) and Remote Sensing Systems (RSS) groups. The record warmest temperatures in the lower atmosphere were recorded in 1998.

For those interested, NCDC has a page of notable weather highlights from June 2010.

June 2010 features an unprecedented heat wave in Asia and North Africa

A withering heat wave of unprecedented intensity brought the hottest temperatures in recorded history to six nations in Asia and Africa, plus the Asian portion of Russia, in June 2010. At least two other Middle East nations came within a degree of their hottest temperatures ever in June. The heat was the most intense in Kuwait, which recorded its hottest temperature in history on June 15 in Abdaly, according to the Kuwait Met office. The mercury hit 52.6°C (126.7°F). Kuwait's previous all-time hottest temperature was 51.9°C (125.4°F), on July 27,2007, at Abdaly. Temperatures reached 51°C (123.8°F) in the capital of Kuwait City on June 15, 2010. Iraq had its hottest day in history on June 14, 2010, when the mercury hit 52.0°C (125.6°F) in Basra. Iraq's previous record was 51.7°C (125.1°F) set August 8, 1937, in Ash Shu'aybah. Saudi Arabia had its hottest temperature ever on June 22, 2010, with a reading of 52.0°C (125.6°F) in Jeddah, the second largest city in Saudi Arabia. The previous record was 51.7°C (125.1°F), at Abqaiq, date unknown. The record heat was accompanied by a sandstorm, which caused eight power plants to go offline, resulting in blackouts to several Saudi cities. In Africa, Chad had its hottest day in history on June 22, 2010, when the temperature reached 47.6°C (117.7°F) at Faya. The previous record was 47.4°C (117.3°F) at Faya on June 3 and June 9, 1961. Niger tied its record for hottest day in history on June 22, 2010, when the temperature reached 47.1°C (116.8°F) at Bilma. That record stood for just one day, as Bilma broke the record again on June 23, when the mercury topped out at 48.2°C (118.8°F). The previous record was 47.1°C on May 24, 1998, also at Bilma. Sudan recorded its hottest temperature in its history on June 25 when the mercury rose to 49.6°C (121.3°F) at Dongola. The previous record was 49.5°C (121.1°F) set in July 1987 in Aba Hamed. The Asian portion of Russia recorded its highest temperature in history on June 25, when the mercury hit 42.3°C (108.1°F) at Belogorsk, near the Amur River border with China. The previous record was 41.7°C (107.1°F) at nearby Aksha on July 21, 2004. (The record for European Russia is 43.8°C--110.8°F--set on August 6, 1940, at Alexandrov Gaj near the border with Kazakhstan. Two other countries came within a degree of their all time hottest temperature on record during the heat wave. Bahrain had its hottest June temperature ever, 46.9°C, on June 20, missing the all-time record of 47.5°C (117.5°F), set July 14, 2000. Temperatures in Quatar reached 48.8°C (119.8°F) on June 20. Quatar's all-time record hottest temperature was 49.6°C (121.3°F) set on July 9, 2000. All of these records are unofficial, and will need to be verified by the World Meteorological Organization (WMO.) The source for the previous all-time records listed here is the book Extreme Weather by Chris Burt.

Eighth warmest June on record for the U.S.

For the contiguous U.S., it was the 8th warmest June in the 116-year record, according to the National Climatic Data Center. Three states had their warmest June on record: Delaware, New Jersey, and North Carolina. Seventeen states had a top-ten warmest June, with five of these recording their second warmest June ever (Maryland, Virginia, South Carolina, Florida, and Louisiana.) No state recorded a top-ten coldest June.

U.S. precipitation

For the contiguous U.S., June 2010 ranked as the 17th wettest June in the 116-year record. June precipitation was the wettest on record for Michigan. Several other states were also anomalously wet, including: Iowa (2nd wettest), Nebraska and Illinois (3rd wettest), Indiana (4th wettest), Wisconsin (5th wettest), Oregon (6th wettest), and Ohio (10th wettest). Maryland (6th driest) was the only state that experienced a top-ten driest June.

U.S. Climate Extremes Index

NCDC's Climate Extremes Index (CEI) for January - June was about 6 percent higher than average. The CEI measures the prevalence of several types of climate extremes (like record or near-record warmth, dry spells, or rainy periods). Factors contributing to the elevated 2010 value were large footprints of: extreme wetness (more than three times the average footprint), warm minimum temperatures ("warm overnight lows"), and areas experiencing heavy 1-day precipitation events.

U.S. tornadoes

According to NOAA's Storm Prediction Center, there were 387 preliminary tornado reports during June. If confirmed, this will be the second most active June on record, behind 1992. Minnesota had a particularly busy month with 67 preliminary tornado reports, besting the previous record of 35 tornadoes during June 2005.

La Niña is here

The equatorial Eastern Pacific Ocean continues to cool, and we have now crossed the threshold into La Niña conditions. Sea surface temperatures (SSTs) over the tropical Eastern Pacific in the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region", fell to 0.8°C below average by July 12, according to NOAA.. The Australian Bureau of Meteorology put this number at 0.7°C below average (as of July 11.) Since La Niña conditions are defined as occurring when this number reaches 0.5°C below average, we are well into the territory of a weak La Niña event. La Niña conditions must be present for several months before this will be officially classified as a La Niña event, but it is highly likely that a full-fledged La Niña event lasting at least eight months has arrived. We started out the year with a strong El Niño, so it may seem surprising that we have transitioned La Niña so quickly, However, historically, about 35 - 40% of El Niño events are followed by a La Niña within the same year. Given current trends, I expect the current La Niña to cross the threshold needed to be defined as "moderate" strength--temperatures at least 1.0°C below average in the equatorial Eastern Pacific--by September. It is well-known that both the number and intensity of hurricanes in the Atlantic tend to increase during La Niña events. However, as I discussed in a post last month, since 1995, neutral years (when neither an El Niño or La Niña are present) have had Atlantic hurricane activity equal to La Niña years. The last time we had a strong El Niño event followed by a La Niña event in the same year, in 1998, we had a Atlantic hurricane season 40% above average in activity, with 14 named storms, 10 hurricanes, and 3 intense hurricanes. The season was relatively late-starting, with only one named storm occurring before August 20. I'm thinking this year's season may be similar, though four or more intense hurricanes are a good bet due to the record warm SSTs. Both El Niño and La Niña events have major impacts on regional and global weather patterns. For the remainder of July and August, we can expect La Niña to bring cloudier and wetter than average conditions to the Caribbean, but weather patterns over North America should not see much impact. Globally, La Niña conditions tend to cause a net cooling of surface temperatures. Thus, while the past twelve month period has been the warmest globally since record keeping began in 1880, it is unlikely that the calendar year of 2010 will set the record for warmest year ever.

June 2010 Arctic sea ice extent lowest on record

Northern Hemisphere sea ice extent in June 2010 was the lowest in the 31-year satellite record, according to the National Snow and Ice Data Center. The rate of ice loss during June was the fastest on record, approximately 50% faster than average. Ice volume was also at a record low through the first half of June, according to University of Washington Polar Ice Center. The record ice loss in June was due in large part to the presence of strong high pressure north of Alaska, combined with strong low pressure over Siberia, which drove warm air from Asia over the pole. This pressure pattern, called the Arctic Dipole, was unknown until the 2000s, and may be the result of climate change.

Jeff Masters