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Global Temperatures

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Brittany
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« on: August 24, 2008, 02:44:21 am »

Global Temperatures

The 2005 global temperature was statistically indistinguishable from the standing record set in 1998. One data set, in use at NCDC since the late 1990s, produced a global annual temperature for 2005 that was slightly below 1998 (below left). An improved data set, which incorporates innovative algorithms that better account for factors such as changes in spatial coverage and evolving observing methods, results in 2005 being slightly warmer than 1998.

The time series on the left shows that the global annual temperature for combined land and ocean surfaces in 2005 was 0.58°C (1.04°F) above average, ranking 2nd. The time series from the improved Smith & Reynolds data set on the right provides a global temperature of 0.62°C (1.12°F) above the 1880-2004 mean, while 1998 was 0.59°C (1.06°F) above average. This data set also provides for the calculation of uncertainties in global temperature attributable to factors such as changes in spatial coverage and evolving observing methods. The range of uncertainty is shown for each year with the uncertainty bounds smaller in more recent years as sampling and random errors decrease with time due to improved coverage and better instruments and measurement techniques.


When calculating global temperatures, NCDC scientists, as well as those at NASA and in the United Kingdom, use methods that address areas of the globe with sparse observations or measurement biases. The various methodologies result in very small differences (on the order of a few hundredths of a degree Celsius) between the global temperature estimates, and these differences can affect individual yearly rankings. Although the ranking of individual years may differ slightly from data set to data set, all records indicate that during the past century, global surface temperatures have increased at a rate near 0.6°C/century (1.1°F/century), but the trend has been three times larger since 1976, with some of the largest temperature increases occurring in the high latitudes.






The widespread anomalous warmth in 2005 is evident in the map to the lower left. Temperature anomalies in 1998 are shown in the map to the right.

The 1880-2004 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).

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Temperature Trends

During the past century, global surface temperatures have increased at a rate near 0.6°C/century (1.1°F/century) but this trend has increased to a rate of 1.8°C/century (3.2°F/century) during the past 25 to 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 50 to 60 years using balloon-borne instruments (radiosondes) and for the past 27 years using satellites. These measurements support the analysis 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 5000 to 30,000 feet above the surface) indicate that 1958-2005 global temperature trends in the middle troposphere are similar to trends in surface temperature; 0.12°C/decade for surface and 0.15°C/decade for mid-troposphere. 2005 global mid-troposphere temperatures were 0.71°C above the 1961-1990 mean, 2nd warmest.
Since 1979, NOAA's polar orbiting satellite measurements have also been used to study temperature trends above the surface. 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 in the mid-troposphere at an altitude of 2 to 6 miles, but which includes the lower stratosphere) has increased, but differing analysis techniques have yielded similar but different trends. In all cases these trends are positive. The increase in the UAH time series is 0.12°C/decade (0.22°F/decade), 0.14°C/decade (0.24°F/decade) for the RSS analysis and 0.10°C/decade (0.17°F/decade) for the University of Washington. Trends in UAH, RSS and UW data are less than the trend in global surface temperatures, which increased at a rate near 0.18°C/decade (0.32°F/decade) during the same 27 year period.

While middle tropospheric temperatures as measured by the MSU indicate an increasing trend over the last two-and-a-half decades, stratospheric (14 to 22 km / 9 to 14 miles) temperatures have been below average. This is consistent with the depletion of ozone in the lower stratosphere. The large temperature increase in 1982 was caused by the volcanic eruption of El Chichon, and the increase in 1991 was caused by the eruption of Mt. Pinatubo in the Philippines.
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Regional Temperatures

larger image Warmer than average conditions occurred throughout most land areas of the world in 2005. The largest anomalies were widespread throughout high latitude regions of the Northern Hemisphere that include much of Russia, Scandinavia, Canada and Alaska. Temperatures in these regions were 3-5°C (5.4-9.0°F) above the 1961-1990 average. There were no widespread areas of negative anomalies.




The map to the left was created using data from the Global Historical Climatology Network (GHCN), a network of more than 7,000 land surface observing stations.

Notable temperature extremes in 2005 include a severe heat wave that gripped the southwestern United States during early to mid-July. Maximum temperatures above 40°C (104°F) affected parts of Nevada, California, Arizona and southern Utah. Numerous temperature records were set around the region. Las Vegas, NV tied their all-time record high temperature of 47.2°C (117°F) on the 19th. Death Valley had 7 consecutive days (July 14-20) with high temperatures equal to or above 51.7°C (125°F). Across Australia, exceptionally warm and dry weather prevailed during March-May 2005. The Australian mean temperature during March-May was 1.62°C (2.92°F) above the long-term average, which is the warmest on record.

In February, extremely cold temperatures affected much of the Balkan region for the first half of the month. In Sevlievo, Bulgaria, a 50-year temperature record was broken when temperatures reached as low as -34°C (-29°F). For more information on temperature extremes during 2005 see the annual report of Significant Events

Additional information on other notable weather events can be found in the Significant Events section of this report, or through the monthly Climate Perspectives reports.



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Northern Hemisphere sea ice extent

larger image Northern Hemisphere sea ice extent, as measured from passive microwave instruments onboard NOAA satellites, was lowest on record for the month of September 2005 at 5.32 million square kilometers, as shown in the image to the left. This is the fourth consecutive year September sea ice extent has been below the long-term (1978-2000) mean. The lowest sea ice extent occurs in September each year, and 2005 is the new all-time low sea ice extent in the historical record. Data courtesy of NOAA's National Snow and Ice Data Center.
Arctic sea ice conditions are inherently variable from year to year in response to wind, temperature and oceanic forcings. Quite often, a "low" ice year is followed by recovery the next year. But increasing surface temperatures in high latitudes have contributed to progressively more summer melt and less ice growth in the fall and winter. While natural variability is responsible for year-to-year variations in sea ice extent, three extreme minimum extent years along with evidence of thinning of the ice pack suggest that the sea ice system is experiencing changes not solely related to natural variability.

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Northern Hemisphere Snow Cover Extent
As shown in the time series to the right, mean Northern Hemisphere snow cover extent during winter (December-February) was slightly above average. Much of this was due to anomalously cold and snowy conditions across Asia and Europe. Mean Northern Hemisphere winter snow cover extent for the 1967-2005 period of record is 45.4 million square kilometers. (Data were provided by David Robinson, Global Snow Lab, Rutgers University).
larger image

larger image Snow cover for the winter season across North America was below average. Mean North American winter snow cover extent is 14.8 million square kilometers for the 1967-2005 period of record.
Northern Hemisphere snow cover extent was significantly below average during the March-May spring season. As shown in the time series graph to the right, spring snow cover extent in the Northern Hemisphere has been below average in 15 of the past 18 years. This is in part due to a trend to warmer spring temperatures that has led to more rapid loss of snow cover during the transition season between winter and summer. Mean Northern Hemisphere spring snow cover extent is 30.9 million square kilometers for the 1967-2005 period of record.
larger image

larger image Spring snow cover extent has also been below average across North America in much of the past two decades. Snow cover extent was significantly below average for the spring 2005 season, the 16th below average year since 1985, and the least seasonal snow cover extent since 1968. Mean North America spring snow cover extent is 10.8 million square kilometers for the 1967-2005 period of record.

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Global Precipitation

larger image Global precipitation in 2005 was near the 1961-1990 average. Regionally drier than average conditions were widespread across eastern Australia, parts of Western Europe, and the U.S. Mississippi Valley and southern Great Plains region. In Australia, Victoria and South Australia experienced the second-driest May on record. In the U.S., Chicago's O'Hare International Airport had the driest spring, summer and fall on record with a total of 420 mm (16.54 inches).

Little to no rain has fallen in Brazil since December 2004. Rainfall was much below average in the Amazon Basin in 2005, producing the worst drought in 60 years in some parts of the region and resulting in the lowest water levels in at least 30 years along the world's second longest river. Across southeastern Africa, long-term drought affected parts of Mozambique, southern Malawi and Zimbabwe. For further information on precipitation events during 2005, see the annual report of Significant Events.

In contrast, several regions of the globe experienced heavy precipitation during 2005. India monsoon rainfall was near normal (98 percent). In July, a new 24-hour rainfall event record was established on the 26th in the city of Mumbai, when over 944 mm (37 inches) of rain fell. A winter storm brought heavy snowfall to much of the northeastern U.S. Boston recorded it's snowiest month on record in January with 1095 mm (43.1 inches) of snow. In Colombia, heavy rains in October and November triggered floods and landslides. In Saudi Arabia, heavy rains during January, produced some of the worst flooding in 20 years in the city of Medina. In August, heavy rainfall affected areas of central and eastern Europe with flooding reported in sections of Romania, Hungary and Macedonia. Farther to the west, flooding also affected areas of Germany, Austria and Switzerland. For more information about precipitation extremes during 2005, see the annual report of Significant Events.

Additional information on other notable weather events can be found in the Significant Events section of this report, or through the monthly Climate Perspectives reports.


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.
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.

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.

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.

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.



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For all climate questions other than questions concerning this report, please contact the National Climatic Data Center's Climate Services Division:

Climate Services Division
NOAA/National Climatic Data Center
151 Patton Avenue, Room 010
Asheville, NC 28801-5001
fax: 828-271-4876
phone: 828-271-4800
email: ncdc.orders@noaa.gov

For questions about this report, please contact:

Jay Lawrimore
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4328
email: Jay.Lawrimore@noaa.gov

-or-
David Easterling
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4328
email: David.Easterling@noaa.gov



http://www.ncdc.noaa.gov/oa/climate/research/2005/ann/global.html#Gtemp
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Brittany
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« Reply #1 on: August 24, 2008, 02:45:04 am »

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« Reply #2 on: August 24, 2008, 02:45:32 am »

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« Reply #3 on: August 24, 2008, 02:46:17 am »

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« Reply #4 on: August 24, 2008, 02:47:04 am »

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« Reply #5 on: August 24, 2008, 02:47:31 am »

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« Reply #6 on: August 24, 2008, 02:47:48 am »

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« Reply #7 on: August 24, 2008, 02:48:06 am »

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« Reply #8 on: August 24, 2008, 02:48:27 am »

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