State of the Climate
Global Analysis
September 2006

National Oceanic and Atmospheric Administration

National Climatic Data Center

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Global Highlights:

Based on preliminary data, globally averaged combined land and sea surface temperature was fourth warmest on record for September 2006.
September temperatures were above average in Alaska, Europe and most of Australia. Cooler-than-average conditions occurred in parts of southeastern China and much of the U.S.
Precipitation during September was above average in India, southern Brazil and most of the eastern U.S., with drier than average conditions eastern Asia, parts of eastern Europe and the U.S. Mississippi Valley.
ENSO conditions transitioned from neutral to a warm phase (El Niño), during September.

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 September 2006 are shown on the dot maps below. The dot map, 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 map, below right, is a product of a merged land surface and sea surface temperature anomaly analysis, which is based on data from the GHCN of land temperatures and the Comprehensive Ocean-Atmosphere Data Set (COADS) of Sea-Surface Temperature (SST) data. 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.

During September, there were above average temperatures across Alaska, Europe, Russia, Australia, Iceland, Mexico and South America. Cooler than average temperatures were observed in parts of eastern Asia and the majority of the U.S.

During January-September 2006, there were above average temperatures in the majority of North America, China, western Europe, South America and Africa. Cooler than average temperatures were observed in Alaska, western Australia and Siberia.

In January-September, warmer than average SSTs occurred in the South Pacific, North and South Atlantic and southern Indian Oceans, with cooler than average conditions observed in the North Pacific and off the coast of western Australia. In September, warmer than average SSTs occurred in the North Atlantic and the Niño 3 and 1+2 regions, with cooler than average conditions observed in the North Pacific and southern Indian Oceans. Please see the latest ENSO discussion for further information.

Current month's Land SurfaceTemperature Dot map

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Current month's blended Land and sea surface Temperature Dot map

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The mean position of upper level ridges of high pressure and troughs of low pressure (depicted by positive and negative 500-millibar height anomalies on the September 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 2006 at the weekly SST page.

Temperature Rankings and Graphics

Effective with the January, 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.

Current Month / Year-to-date

September	Anomaly	Rank	Warmest Year on Record
Global Land Ocean Land and Ocean	+0.73°C (+1.31°F) +0.50°C (+0.90°F) +0.56°C (+1.01°F)	2nd warmest 3rd warmest 4th warmest	2005 (+1.03°C/1.85°F) 1997 (+0.54°C/0.97°F) 2005 (+0.64°C/1.15°F)
Northern Hemisphere Land Ocean Land and Ocean	+0.73°C (+1.31°F) +0.62°C (+1.12°F) +0.66°C (+1.19°F)	3rd warmest 2nd warmest 3rd warmest	2005 (+1.18°C/2.12°F) 2003 (+0.67°C/1.21°F) 2005 (+0.83°C/1.49°F)
Southern Hemisphere Land Ocean Land and Ocean	+0.72°C (+1.30°F) +0.40°C (+0.72°F) +0.45°C (+0.81°F)	5th warmest 3rd warmest 2nd warmest	1997 (+1.08°C/1.94°F) 1997 (+0.54°C/0.97°F) 1997 (+0.62°C/1.12°F)

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January-September	Anomaly	Rank	Warmest Year on Record
Global Land Ocean Land and Ocean	+0.72°C (+1.30°F) +0.43°C (+0.77°F) +0.51°C (+0.92°F)	5th warmest 6th warmest 5th warmest	2002 (+0.96°C/1.73°F) 1998 (+0.52°C/0.94°F) 1998 (+0.63°C/1.13°F)
Northern Hemisphere Land Ocean Land and Ocean	+0.80°C (+1.44°F) +0.45°C (+0.81°F) +0.58°C (+1.04°F)	6th warmest 5th warmest 5th warmest	2002 (+1.09°C/1.96°F) 2005 (+0.55°C/0.99°F) 2005 (+0.71°C/1.28°F)
Southern Hemisphere Land Ocean Land and Ocean	+0.48°C (+0.86°F) +0.43°C (+0.77°F) +0.43°C (+0.77°F)	8th warmest 5th warmest 5th warmest	2005 (+0.86°C/1.55°F) 1998 (+0.54°C/0.97°F) 1998 (+0.58°C/1.04°F)

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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 September, above average precipitation fell over areas that include much of the eastern U.S. and northern Plains, southern Europe, India, along the Gulf of Guinea and parts of southeast Asia. Heavy rain and flooding occurred in Ethiopia and India. Below average precipitation was observed in areas including the U.S. Mississippi Valley, northern Europe, South Africa and much of eastern Asia. Additional details on flooding and drought can also be found on the September Global Hazards page.

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Precipitation Dot map in Percent for September

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ENSO SST Analysis

Last week of the month's ENSO condtions Map

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Sea Surface Temperatures continued to increased across the equatorial Pacific Ocean during September, transitioning ENSO from a neutral state to a warm phase, El Niño (shown in the adjacent animation of weekly sea surface temperature anomalies). A comprehensive summary of September 2006 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 during 2006 at the weekly SST page

Northern Hemisphere Sea Ice Extent

According to the National Snow and Ice Data Center, the Northern Hemisphere sea ice extent, which is measured from passive microwave instruments onboard NOAA satellites, was 5.9 million square kilometers as of September 14, 2006, the second lowest on record (image to the right). The September rate of sea ice decline is now almost 9 percent per decade (60,421 square kilometers per year). From January to mid-July 2006, the sea ice extent was well below the record set just last year. However, in August, temperatures near the pole were 1° to 2°C cooler than average, inhibiting further melting. For further information on Northern Hemisphere snow and ice conditions, please see the NSIDC News page, provided by the NOAA's National Snow and Ice Data Center (NSIDC).

September sea ice extent for the Northern Hemisphere

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Troposphere

Current Month / Year-to-date
Temperatures above the Earth's surface are measured using in-situ balloon-borne instruments (radiosondes) and polar-orbiting satellites (NOAA's TIROS-N). The radiosonde and the 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).

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 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.

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Radiosonde measurements indicate that for the January-September year-to-date period, temperatures in the mid-troposphere (approximately 2 to 6 miles above the Earth's surface) were 0.56°C above average, the 3rd warmest January-September since global measurements began in 1958. In a pattern similar to that at the surface, radiosonde measurements indicate that temperatures have risen at a rate of 0.15°C/decade since the late 1950's and 0.17°C/decade since 1979.

Satellite measurements provide similar results. Since 1979, the RSS analysis indicates that January-September temperatures have risen at a rate of 0.13°C/decade, while the UW-RSS analysis shows a faster rate of 0.19°C/decade. (The UAH analysis is unavailable this month.)

Mid-troposphere rankings and anomalies from the satellite analyses for the year-to-date and September periods are available below. These temperatures are for the atmospheric layer centered in the mid-troposphere (approximately 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 6 miles). For additional information on MSU data used in this report, please see the Microwave Sounding Unit page.

All datasets indicate September temperatures were above average.

September	Anomaly	Rank	Warmest Year on Record	Trend
*RSS mid-trop	+0.22°C/0.40°F	7th warmest	1998 (+0.52°C/0.94°F)	+0.17°C/decade
*UW-RSS mid-trop	+0.34°C/0.61°F	6th warmest	1998 (+0.66°C/1.19°F)	+0.24°C/decade

*Version 02_1

January- September	Anomaly	Rank	Warmest Year on Record	Trend
*RSS mid-trop	+0.17°C/0.31°F	7th warmest	1998 (+0.60°C/1.08°F)	+0.13°C/decade
*UW-RSS mid-trop	+0.27°C/0.49°F	6th warmest	1998 (+0.73°C/1.31°F)	+0.19°C/decade
RATPAC	+0.56°C/1.01°F	3rd warmest	1998 (+0.79°C/1.42°F)	+0.17°C/decade

*Version 02_1

Stratosphere

Current Month
The table below summarizes stratospheric conditions for September 2006. On average, the stratosphere is located approximately between 10-14 miles above the Earth's surface. Over the last decade, stratospheric temperatures have been below average in large 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. Temperatures returned to pre-eruption levels within two years.

September	Anomaly	Rank	Coolest Year on Record
UAH stratosphere	-0.70°C (-1.26°F)	3rd coolest	2005 (-0.78°C/-1.40°F)
*RSS stratosphere	-0.47°C (-0.85°F)	5th coolest	1996 (-0.74°C/-1.33°F)

*Version 02_1

For additional details on precipitation and temperatures in September, 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.