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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.
Temperature anomalies for September 2007 are shown on the dot maps below. The dot map, below left, provides 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 map, below right, is 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-September 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 September, there were above average temperatures across southeastern Brazil, Paraguay, Uruguay, the contiguous U.S., Australia, northwestern and southeastern Africa, and most of Alaska and Asia. Cooler-than-average conditions occurred in Peru and central Europe. Meanwhile, SST anomalies in the Niño 3.4 region became increasingly negative during September, 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 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 2007 at the weekly SST page.
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).
September 2007 ranked as the fifth warmest September since records began in 1880 for combined global land and ocean surface temperatures. The September land surface temperature ranked second warmest on record, while the ocean surface temperature ranked ninth warmest in the 127-year record. The global surface temperature for the combined January-September year-to-date period was the fourth warmest January-September on record, while the global land surface temperature ranked warmest on record for January-September 2007.
| September | Anomaly | Rank | Ties | Warmest (or Next Warmest) Year on Record |
|---|---|---|---|---|
GlobalLandOcean Land and Ocean |
+0.85°C (+1.53°F) +0.38°C (+0.68°F) +0.51°C (+0.92°F) |
2nd warmest 9th warmest 5th warmest |
2000 2002 |
2005 (+1.04°C/1.87°F) 1997 (+0.54°C/0.97°F) 2005 (+0.64°C/1.15°F) |
Northern HemisphereLandOcean Land and Ocean |
+0.84°C (+1.51°F) +0.45°C (+0.81°F) +0.60°C (+1.08°F) |
2nd warmest 6th warmest 4th warmest |
2002 |
2005 (+1.20°C/2.16°F) 2003 (+0.67°C/1.21°F) 2005 (+0.83°C/1.49°F) |
Southern HemisphereLandOcean Land and Ocean |
+0.89°C (+1.60°F) +0.32°C (+0.58°F) +0.41°C (+0.74°F) |
5th warmest 11th warmest 7th warmest |
2001 |
1997 (+1.08°C/1.94°F) 1997 (+0.54°C/0.97°F) 1997 (+0.62°C/1.12°F) |
| January- September |
Anomaly | Rank | Ties | Warmest (or Next Warmest) Year on Record |
|---|---|---|---|---|
GlobalLandOcean Land and Ocean |
+1.04°C (+1.87°F) +0.41°C (+0.74°F) +0.58°C (+1.04°F) |
warmest 7th warmest 4th warmest |
2002 (+0.97°C/1.75°F) 1998 (+0.52°C/0.94°F) 1998 (+0.63°C/1.13°F) |
|
Northern HemisphereLandOcean Land and Ocean |
+1.23°C (+2.21°F) +0.44°C (+0.79°F) +0.74°C (+1.33°F) |
warmest 6th warmest warmest |
2002 (+1.10°C/1.98°F) 2005 (+0.55°C/0.99°F) 2005 (+0.71°C/1.28°F) |
|
Southern HemisphereLandOcean Land and Ocean |
+0.51°C (+0.92°F) +0.39°C (+0.70°F) +0.41°C (+0.74°F) |
5th warmest 8th warmest 8th warmest |
1988 1997 |
2005 (+0.85°C/1.53°F) 1998 (+0.54°C/0.97°F) 1998 (+0.58°C/1.04°F) |
The most current data may be accessed via the Global Surface Temperature Anomalies page.
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 2007, above average precipitation fell over areas that include Japan, North and South Korea, the Philippines, southwestern Alaska, and parts of India, Bangladesh, Africa, and central Europe. Drier-than-average conditions were observed in the northern and southern eastern region of the contiguous U.S., southeastern Australia, and parts of South America and southeastern China. Additional details on flooding and drought can also be found on the September Global Hazards page.
Sea Surface Temperature anomalies were cooler-than-normal across the eastern and central equatorial Pacific during September while warmer-than-normal 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 September 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.
According to the National Snow and Ice Data Center, the September 2007 Northern Hemisphere sea ice extent, which is measured from passive microwave instruments onboard NOAA satellites, was the least sea ice extent on record for the month of September at 4.28 million square kilometers (39% below the 1979-2000 mean). Sea ice extent for September has decreased at a rate of 10.2%/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. The lowest sea ice extent occurs in September each year, so the record low that occured during September 2007 is also the all-time low sea ice extent in the historical record, surpassing the previous record set in 2005 by 23%. 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).
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).
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.
| September | Anomaly | Rank | Warmest (or Next Warmest) Year on Record | Trend |
|---|---|---|---|---|
| UAH low-trop | +0.24°C/0.43°F | 8th warmest | 1998 (+0.47°C/0.85°F) | +0.16°C/decade |
| *RSS low-trop | +0.12°C/0.22°F | 14th warmest | 1998 (+0.53°C/0.95°F) | +0.19°C/decade |
*Version 03_0
| January- September |
Anomaly | Rank | Warmest (or Next Warmest) Year on Record | Trend |
|---|---|---|---|---|
| UAH low-trop | +0.31°C/0.56°F | 4th warmest | 1998 (+0.59°C/1.06°F) | +0.14°C/decade |
| *RSS low-trop | +0.21°C/0.39°F | 8th warmest | 1998 (+0.66°C/1.18°F) | +0.18°C/decade |
*Version 03_0
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-September year-to-date period, temperatures in the mid-troposphere were 0.58°C (1.04°F) above average, resulting in the third warmest January-September since global measurements began in 1958. However, as shown in the table below, satellite measurement of the January-September year-to-date period for the middle troposphere varied from third to fifth warmest on record.
September 2007 experienced warmer than average mid-troposphere temperatures, as shown in the table below. Satellite measurement for the month ranked from seventh to eleventh warmest on record depending on the analysis.
| September | Anomaly | Rank | Warmest (or Next Warmest) Year on Record | Trend |
|---|---|---|---|---|
| UAH mid-trop | +0.14°C/0.25°F | 11th warmest | 1998 (+0.44°C/0.79°F) | +0.09°C/decade |
| *RSS mid-trop | +0.20°C/0.35°F | 8th warmest | 1998 (+0.49°C/0.88°F) | +0.15°C/decade |
| **UW-UAH mid-trop | +0.25°C/0.45°F | 8th warmest | 1998 (+0.61°C/1.09°F) | +0.16°C/decade |
| **UW-*RSS mid-trop | +0.29°C/0.52°F | 7th warmest | 1998 (+0.64°C/1.16°F) | +0.21°C/decade |
*Version 03_0
| January- September |
Anomaly | Rank | Warmest (or Next Warmest) Year on Record | Trend |
|---|---|---|---|---|
| UAH mid-trop | +0.18°C/+0.33°F | 4th warmest | 1998 (+0.53°C/0.95°F) | +0.06°C/decade |
| *RSS mid-trop | +0.24°C/0.44°F | 5th warmest | 1998 (+0.59°C/1.06°F) | +0.12°C/decade |
| **UW-UAH mid-trop | +0.29°C/+0.53°F | 3rd warmest | 1998 (+0.67°C/1.20°F) | +0.13°C/decade |
| **UW-*RSS mid-trop | +0.34°C/+0.61°F | 5th warmest | 1998 (+0.71°C/1.28°F) | +0.18°C/decade |
| RATPAC | +0.58°C/1.04°F | 3rd warmest | 1998 (+0.80°C/1.44°F) | +0.15°C/decade |
*Version 03_0
The table below summarizes stratospheric conditions for September 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.
| September | Anomaly | Rank | Coolest Year on Record |
|---|---|---|---|
| UAH stratosphere | -0.64°C (-1.15°F) | 3rd coolest | 1996 (-0.74°C/-1.33°F) |
| *RSS stratosphere | -0.64°C (-1.15°F) | 2nd coolest | 1996 (-0.74°C/-1.33°F) |
*Version 03_0
For additional details on precipitation and temperatures in September, see the Global Hazards page.
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.
For questions on technical or scientific content of this report, please contact:
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