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Climate Law Institute
Science Daily, July 19, 2010

June Was the Fourth Consecutive Month That Was Warmest on Record

Each month NOAA's National Climatic Data Center (NCDC) releases two assessments, one national and one global, of the previous month's climate. These reports include information on the temperature and precipitation levels experienced nationally and globally, providing useful information about these important climate variables in historical perspective. The reports also chronicle any significant weather and climate-related events that occurred during the month. This trusted source of information is used globally by industry and business, government agencies, academia, and members of the public to help inform decision making.

Summary Figures from the Global Report

The global report is a monthly snapshot of the climate system around the globe that informs the public of the current state of the global climate and helps planners, academics and sector users factor the climate's current state and recent trends into their decision making. The report details the average global land temperature, the average global ocean temperature, and the combined average of the two. Instead of using raw temperatures, the report presents temperature anomalies, which means the difference from average temperatures for any given area over a period of time. Using anomalies allows for a more accurate understanding of temperature trends over space and time, even with some fluctuations in data availability.

June 2010 Global Temperature Anomalies

Highlights:

  • June was the fourth consecutive month that was the warmest on record for the combined global land and surface temperatures (March, April, and May were also the warmest). This was the 304th consecutive month with a combined global land and surface temperature above the 20th century average. The last month with below average temperatures was February 1985.
  • It was the warmest June on record for the land surfaces of the globe. Previous record was set in 2005. The land surface temperature exceeded the previous record by 0.11˚C (0.20˚F). This large difference over land contributed strongly to the overall global land and ocean temperature anomaly.
  • The worldwide oceans experienced the fourth warmest June on record. Sea surface temperatures across the eastern and central equatorial Pacific Ocean continued to decrease, damping ocean surface temperatures.
  • According to Beijing Climate Center, Inner Mongolia, Heilongjiang, and Jilin experienced their warmest June since records began in 1951. Meanwhile, Guizhou had its coolest June on record.
  • Spain experienced its coolest June temperature anomaly since 1997, according to Spain's meteorological office.

Year -to-Date January -- June 2010 Global Temperature Anomalies

Highlights:

  • The year-to-date (January-June) combined global land and ocean temperature was the warmest on record.
  • The worldwide land surface temperature had its second warmest year-to-date (January-June), behind 2007.
  • The worldwide ocean temperature was the second warmest year-to-date (January-June), behind 1998.
  • 2010 surpassed 1998 (Feb, Jul, Aug) for the most "warmest months" in any calendar year.

Comparing 20 years of Global Temperature Trends

Each of the 10 warmest average global temperatures recorded since 1880 have occurred in the last fifteen years. The warmest year-to-date on record, through June, was 1998, and 2010 is warmer so far (note: although 1998 was the warmest year through June, a late-year warm surge in 2005 made that year the warmest total year). Analysis by the National Climatic Data Center reveals that June of 2010 was the warmest global average for that month on record, and is also the warmest year-to-date from January to June. This graph plots the year-to-date average global land and ocean temperature. The 2010 value, complete only through June, is shown in red at the end of the animation.

Background Information Why Track Temperature Anomalies, Not Absolute Temperatures?

Temperature anomaly refers to the difference from average. The global temperature is calculated using anomalies because they give a more accurate picture of temperature change. If calculating an average temperature for a region, factors like station location or elevation affect the data, but when looking at the difference from the average for that same location, those factors are less critical. For example, while the actual temperature on a hilltop will be different than in a nearby valley on a given day or month, stations in both places will show a similar trend in temperature when you calculate the change in temperature compared to average for that station.

Using anomalies also helps minimize problems when stations are added to or removed from the monitoring network. The above diagram helps show how even if one station were removed from the record or did not report data for some period of time, the average anomaly would not change significantly, whereas the overall average temperature could change significantly depending on which station dropped out of the record.

Where does NOAA get its Global Data?

NOAA's NCDC is the world's largest active archive of weather data. It houses data archives dating back to 1880 from all over the world. Each month, countries from all over the world send their land-based meteorological surface observations, meaning temperature and precipitation measurements, to NCDC to be added to the global record.

This information is sent through the World Meteorological Organization's (WMO) Global Telecommunication System (GTS) -- a coordinated system for the rapid collection, exchange and distribution of observation data from more than 200 countries around the world. The data are sent in a format called "CLIMAT messages" (pronounced "cleem-mat"), which are a summary of monthly weather data for a specific station. The CLIMAT message contains information of average pressure at station level, average air temperature, maximum air temperature, minimum air temperature, average vapor pressure, total precipitation, and total sunshine for a particular month.

These messages are typically sent to NCDC by the 8th of every month. NCDC uses the data to produce numerous climate publications, such as the monthly global state of the climate report.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by National Oceanic and Atmospheric Administration.

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Photo © Paul S. Hamilton