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Climate of 2007
August in Historical Perspective

Including Boreal Summer

National Climatic Data Center
12 September 2007

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The data presented in this report are preliminary. Ranks and anomalies may change as more complete data are received and processed. The most current data may be accessed via the Global Surface Temperature Anomalies page.

Introduction

Temperature anomalies for August 2007 are shown on the dot maps below. The dot maps, below left, provide a spatial representation of anomalies calculated from the Global Historical Climatology Network (GHCN) data set of land surface stations using a 1961-1990 base period. The dot maps, below right, are a product of a merged land surface and sea surface temperature anomaly analysis developed by Smith and Reynolds (2005). Temperature anomalies with respect to the 1961-1990 mean for land and ocean are analyzed separately and then merged to form the global analysis. Additional information on this product is available.

Anomalously warm temperatures have covered much of the globe throughout the year. The January-August 2007 map of temperature anomalies shows the presence of warmer-than-average temperatures across all land areas, with the exception of the southern countries located in South America and the south central states in the contiguous U.S. Warmer-than-average Sea Surface Temperatures (SSTs) occurred in the Atlantic, Indian, and the Northwest Pacific oceans. Cooler-than-average conditions were observed in the Niño 1+2 and 3 regions, the northeastern Pacific and some areas in the southern oceans.

During the boreal summer, there were above average temperatures across northwestern Africa, southern Australia, eastern Brazil, and most of Europe, Asia, and the U.S., including Alaska. Meanwhile, cooler-than-average conditions occurred in northern Australia, the southern parts of South America, and parts of the south central U.S.

During August, there were above average temperatures across northwestern Africa and most of Alaska, Europe, Asia, Australia, and the contiguous U.S. Cooler-than-average conditions occurred in most of the southern countries in South America. Meanwhile, SST anomalies in the Niño 3.4 region cooled in August, indicating development of an ENSO cold event (La Niña). Please see the latest ENSO discussion for additional information.

The mean position of the upper level ridges of high pressure and troughs of low pressure (depicted by positive and negative 500-millibar height anomalies on the June-August 2007 map and the August map) are generally reflected by areas of positive and negative temperature anomalies at the surface, respectively. For other Global products see the Climate Monitoring Global Products page.

Images of sea surface temperature conditions are available for all weeks during 2007 at the weekly SST page.

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Temperature Rankings and Graphics

Current Month / Seasonal / Year-to-date

Effective with the February 2006 report, NCDC transitioned from the use of the Operational Global Surface Temperature Index (Quayle et al. 1999) to the blended land and ocean dataset developed by Smith and Reynolds (2005). The differences between the two methods are discussed in Smith et al. (2005).

The 2007 January-August year-to-date period ranked as the fourth warmest January-August since records began in 1880 for combined global land and ocean surface temperatures, while the global land surface temperature ranked warmest on record. Meanwhile, the combined global land and ocean surface temperature for boreal summer (June-August 2007) was seventh warmest on record, and the land surface temperature was 5th warmest. As for the month of August, the land surface temperature ranked third warmest on record, while the ocean surface temperature tied with 1995 and 2000 as the ninth warmest in the 127-year record.

August	Anomaly	Rank	Ties	Warmest (or Next Warmest) Year on Record
Global Land Ocean Land and Ocean	+0.80°C (+1.44°F) +0.35°C (+0.63°F) +0.47°C (+0.85°F)	3rd warmest 9th warmest 8th warmest	1995,2000	1998 (+0.92°C/1.66°F) 1998 (+0.54°C/0.97°F) 1998 (+0.64°C/1.15°F)
Northern Hemisphere Land Ocean Land and Ocean	+1.00°C (+1.80°F) +0.41°C (+0.74°F) +0.64°C (+1.15°F)	warmest 10th warmest 5th warmest	2000	1998 (+0.95°C/1.71°F) 2005 (+0.65°C/1.17°F) 2003 (+0.72°C/1.30°F)
Southern Hemisphere Land Ocean Land and Ocean	+0.22°C (+0.40°F) +0.30°C (+0.54°F) +0.29°C (+0.52°F)	33rd warmest 14th warmest 18th warmest	1910 1995 1944,1983	1981 (+1.31°C/2.36°F) 1998 (+0.51°C/0.92°F) 1998 (+0.57°C/1.03°F)

June-August	Anomaly	Rank	Ties	Warmest (or Next Warmest) Year on Record
Global Land Ocean Land and Ocean	+0.74°C (+1.33°F) +0.39°C (+0.70°F) +0.49°C (+0.88°F)	5th warmest 9th warmest 7th warmest		1998 (+0.90°C/1.62°F) 1998 (+0.54°C/0.97°F) 1998 (+0.64°C/1.15°F)
Northern Hemisphere Land Ocean Land and Ocean	+0.92°C (+1.66°F) +0.43°C (+0.77°F) +0.62°C (+1.12°F)	warmest 9th warmest 4th warmest	1998	2006 (+0.90°C/1.62°F) 2005 (+0.64°C/1.15°F) 2005 (+0.72°C/1.30°F)
Southern Hemisphere Land Ocean Land and Ocean	+0.22°C (+0.40°F) +0.36°C (+0.65°F) +0.34°C (+0.61°F)	30th warmest 9th warmest 12th warmest	1970 1981	2005 (+0.88°C/1.58°F) 1998 (+0.53°C/0.95°F) 1998 (+0.58°C/1.04°F)

January-August	Anomaly	Rank	Ties	Warmest (or Next Warmest) Year on Record
Global Land Ocean Land and Ocean	+1.07°C (+1.93°F) +0.41°C (+0.74°F) +0.59°C (+1.06°F)	warmest 7th warmest 4th warmest		2002 (+1.00°C/1.80°F) 1998 (+0.53°C/0.95°F) 1998 (+0.65°C/1.17°F)
Northern Hemisphere Land Ocean Land and Ocean	+1.27°C (+2.29°F) +0.44°C (+0.79°F) +0.75°C (+1.35°F)	warmest 5th warmest warmest		2002 (+1.15°C/2.07°F) 2005 (+0.54°C/0.97°F) 2002 (+0.70°C/1.26°F)
Southern Hemisphere Land Ocean Land and Ocean	+0.48°C (+0.86°F) +0.40°C (+0.72°F) +0.41°C (+0.74°F)	6th warmest 8th warmest 8th warmest	2001,2004	2005 (+0.88°C/1.58°F) 1998 (+0.55°C/0.99°F) 1998 (+0.60°C/1.08°F)

The most current data may be accessed via the Global Surface Temperature Anomalies page.

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Precipitation

The maps below represent anomaly values based on the GHCN data set of land surface stations using a base period of 1961-1990. During boreal summer, above average precipitation fell over areas that include the central U.S, western and southern India, and parts of eastern Australia, eastern China, and Russia. Drier-than-average conditions were observed in southern Australia, southeastern U.S. and parts of South America and South Asia.

During August 2007, above average precipitation fell over areas that include parts of the midwestern U.S., India, and eastern China. Drier-than-average conditions were observed in southeastern and western U.S., southern Australia, and parts of South America, Japan, and South Asia. Additional details on flooding and drought can also be found on the August Global Hazards page.

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ENSO SST Analysis

Sea Surface Temperature anomalies were below average across the eastern and central equatorial Pacific during August while above average anomalies were observed across the western equatorial Pacific. These conditions are indicative of a developing ENSO cold event (shown in the adjacent animation of weekly sea surface temperature anomalies). A comprehensive summary of August 2007 ENSO conditions can be found on the ENSO monitoring page. For the latest advisory on ENSO conditions go to NOAA's Climate Prediction center (CPC) and the CPC ENSO Diagnostic Discussion.

Images of sea surface temperature conditions are available for all weeks since 2003 at the weekly SST page.

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Northern Hemisphere Sea Ice Extent

According to the National Snow and Ice Data Center, the August 2007 Northern Hemisphere sea ice extent, which is measured from passive microwave instruments onboard NOAA satellites, was below the 1979-2000 mean. This was the least sea ice extent in August since records began in 1979. Sea ice extent for August has decreased at a rate of 8.4%/decade (since satellite records began in 1979) as temperatures in the high latitude Northern Hemisphere have risen at a rate of approximately 0.37°C/decade over the same period. For further information on the Northern Hemisphere snow and ice conditions, please visit the NSIDC News page, provided by the NOAA's National Snow and Ice Data center (NSIDC).

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Troposphere

Temperatures above the Earth's surface are measured within the lower troposphere, middle troposphere, and stratosphere using in-situ balloon-borne instruments (radiosondes) and polar-orbiting satellites (NOAA's TIROS-N). The radiosonde and satellite records have been adjusted to remove time-dependent biases (artificialities caused by changes in radiosonde instruments and measurement practices as well as changes in satellite instruments and orbital features through time).

Lower Troposphere

Current Month / Seasonal / Year-to-date

These temperatures are for the lowest 8 km (5 miles) of the atmosphere. Information on the UAH and RSS sources of troposphere data is available.

August	Anomaly	Rank	Warmest (or Next Warmest) Year on Record	Trend
UAH low-trop	+0.32°C/0.58°F	2nd warmest	1998 (+0.52°C/0.94°F)	+0.13°C/decade
*RSS low-trop	+0.22°C/0.40°F	8th warmest	1998 (+0.61°C/1.10°F)	+0.18°C/decade

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June- August	Anomaly	Rank	Warmest (or Next Warmest) Year on Record	Trend
UAH low-trop	+0.27°C/0.48°F	3rd warmest	1998 (+0.55°C/0.99°F)	+0.13°C/decade
*RSS low-trop	+0.19°C/0.35°F	9th warmest	1998 (+0.61°C/1.10°F)	+0.17°C/decade

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January- August	Anomaly	Rank	Warmest (or Next Warmest) Year on Record	Trend
UAH low-trop	+0.32°C/0.57°F	3rd warmest	1998 (+0.60°C/1.08°F)	+0.14°C/decade
*RSS low-trop	+0.23°C/0.41°F	7th warmest	1998 (+0.67°C/1.21°F)	+0.18°C/decade

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Mid-troposphere

Current Month / Seasonal / Year-to-date

These temperatures are for the atmospheric layer centered in the mid-troposphere (approximately 3-10 km (2-6 miles) above the Earth's surface), which also includes a portion of the lower stratosphere. (The MSU channel used to measure mid-tropospheric temperatures receives about 25 percent of its signal above 10 km (6 miles)). Because the stratosphere has cooled due to increasing greenhouse gases in the troposphere and losses of ozone in the stratosphere, the stratospheric contribution to the tropospheric average, as measured from satellites, may create an artificial component of cooling to the mid-troposphere temperatures. The University of Washington (UW) versions of the UAH and RSS analyses attempt to remove the stratospheric influence from the mid-troposphere measurements, and as a result the UW versions tend to have a larger warming trend than either the UAH or RSS versions. For additional information, please see NCDC's Microwave Sounding Unit page.

The radiosonde data used in this global analysis were developed using the Lanzante, Klein, Seidel (2003) ("LKS") bias-adjusted dataset and the First Difference Method (Free et al. 2004). Additional details are available. Satellite data have been adjusted by the Global Hydrology and Climate center at the University of Alabama in Huntsville (UAH). An independent analysis is also performed by Remote Sensing Systems (RSS) and a third analysis has been performed by Dr. Qiang Fu of the University of Washington (UW) (Fu et al. 2004)** to remove the influence of the stratosphere on the mid-troposphere value. Global averages from radiosonde data are available from 1958 to present, while satellite measurements began in 1979.

Radiosonde measurements indicate that for the January-August year-to-date period, temperatures in the mid-troposphere were 0.58°C (1.04°F) above average, resulting in the third warmest January-August since global measurements began in 1958. However, as shown in the table below, satellite measurement of the January-August year-to-date period for the middle troposphere varied from third to fifth warmest on record.

During the boreal summer, radiosonde measurements indicate that temperatures were 0.48°C (0.86°F) above average, giving June-August a rank of fifth warmest on record. The table below shows that satellite measurements for the boreal summer varied from third to fifth warmest on record.

The global mid-troposphere temperatures were warmer than average in August 2007, as shown in the table below. Satellite measurement for August 2007 ranked from third to fifth warmest on record depending on the analysis.

August	Anomaly	Rank	Warmest (or Next Warmest) Year on Record	Trend
UAH mid-trop	+0.21°C/0.38°F	5th warmest	1998 (+0.45°C/0.81°F)	+0.07°C/decade
*RSS mid-trop	+0.26°C/0.47°F	4th warmest	1998 (+0.51°C/0.91°F)	+0.12°C/decade
**UW-UAH mid-trop	+0.32°C/0.58°F	3rd warmest	1998 (+0.60°C/1.08°F)	+0.13°C/decade
**UW-*RSS mid-trop	+0.35°C/0.64°F	3rd warmest	1998 (+0.65°C/1.17°F)	+0.17°C/decade

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June- August	Anomaly	Rank	Warmest (or Next Warmest) Year on Record	Trend
UAH mid-trop	+0.18°C/0.32°F	4th warmest	1998 (+0.48°C/0.86°F)	+0.06°C/decade
*RSS mid-trop	+0.23°C/0.41°F	5th warmest	1998 (+0.53°C/0.96°F)	+0.12°C/decade
**UW-UAH mid-trop	+0.29°C/0.52°F	3rd warmest	1998 (+0.61°C/1.10°F)	+0.12°C/decade
**UW-*RSS mid-trop	+0.31°C/0.56°F	4th warmest	1998 (+0.65°C/1.17°F)	+0.17°C/decade
RATPAC	+0.48°C/0.86°F	5th warmest	1998 (+0.88°C/1.58°F)	+0.16°C/decade

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January- August	Anomaly	Rank	Warmest (or Next Warmest) Year on Record	Trend
UAH mid-trop	+0.19°C/+0.34°F	4th warmest	1998 (+0.54°C/0.97°F)	+0.06°C/decade
*RSS mid-trop	+0.25°C/0.45°F	5th warmest	1998 (+0.60°C/1.08°F)	+0.12°C/decade
**UW-UAH mid-trop	+0.30°C/+0.53°F	3rd warmest	1998 (+0.67°C/1.20°F)	+0.12°C/decade
**UW-*RSS mid-trop	+0.34°C/+0.61°F	4th warmest	1998 (+0.72°C/1.29°F)	+0.18°C/decade
RATPAC	+0.58°C/1.04°F	3rd warmest	1998 (+0.83°C/1.49°F)	+0.15°C/decade

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Stratosphere

Current Month / Seasonal

The table below summarizes stratospheric conditions for August 2007. On average, the stratosphere is located approximately between 16-23 km (10-14 miles) above the Earth's surface. Over the last decade, stratospheric temperatures have been below average in part due to the depletion of ozone. The large positive anomaly in 1982 was caused by the volcanic eruption of El Chichon in Mexico, and the sharp jump in temperature in 1991 was a result of the eruption of Mt. Pinatubo in the Philippines. In both cases the temperatures returned to pre-eruption levels within two years.

August	Anomaly	Rank	Coolest Year on Record
UAH stratosphere	-0.66°C (-1.19°F)	2nd coolest	1996 (-0.70°C/-1.26°F)
*RSS stratosphere	-0.55°C (-0.99°F)	3rd coolest	1996 (-0.67°C/-1.20°F)

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June- August	Anomaly	Rank	Coolest Year on Record
UAH stratosphere	-0.64°C (-1.15°F)	4th coolest	1996 (-0.73°C/-1.32°F)
*RSS stratosphere	-0.50°C (-0.88°F)	4th coolest	1996 (-0.64°C/-1.16°F)

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For additional details on precipitation and temperatures in August, see the Global Hazards page.

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

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.

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For questions about this report, please contact:

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email: David.Easterling@noaa.gov

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