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Climate of 2004 - August in Historical Perspective Including Boreal Summer National
Climatic Data Center
15 September 2004
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Global Analysis / Global Hazards / United States / U.S. Drought / Extremes
Use these links to
access detailed analyses of Global and U.S. data.
Global Highlights:
- Based on preliminary data, global average combined land and sea surface temperature was sixth warmest on record for both August and June-August 2004
- June-August temperatures were above average throughout Europe, Alaska and the western U.S., with below average temperatures in the central U.S. and southwestern Australia
- Precipitation during June-August was above average across the eastern U.S., western Europe and parts of Scandinavia, with drier than average conditions in India, eastern Australia and parts of Alaska
- Sea Surface Temperatures (SSTs) continued to increase in the western and central tropical Pacific
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Contents of this Section:
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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.
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 Introduction
The two maps below utilize different base periods and may reflect different anomaly values of land surface temperatures. The dot map on the left uses anomalies that were calculated from the Global Historical Climatology Network (GHCN) data set of land surface stations using a 1961-1990 base period. The map on the right is a blended product which uses satellite and surface anomaly values of measured land and ocean temperatures as well as SSTs with the base period of 1988-2004. Both maps reflect conditions during summer 2004, indicating above average temperatures in Alaska, Mongolia, Argentina and Iceland, with cooler than average temperatures over most of the U.S., parts of far eastern Russia and portions of Brazil. During the month of August 2004, above average temperatures occurred in Europe, the pacific northwest of the U.S. and Alaska while cooler than average conditions occurred in the central portion of the U.S., parts of Brazil and western Australia.
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 June-August 2004 and August 2004 maps) 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.
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Temperature Rankings and Graphics
Current Month / Seasonal / Year-to-date
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August |
Anomaly |
Rank |
Warmest Year on Record |
Global
Land
Ocean
Land and Ocean
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+0.47°C (+0.85°F)
+0.42°C (+0.76°F)
+0.44°C (+0.80°F)
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12th warmest
4th warmest
6th warmest
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1998 (+0.97°C/1.75°F)
1998 (+0.50°C/0.90°F)
1998 (+0.64°C/1.15°F)
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Northern Hemisphere
Land
Ocean
Land and Ocean
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+0.62°C (+1.12°F)
+0.58°C (+1.04°F)
+0.59°C (+1.06°F)
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8th warmest
3rd warmest
4th warmest
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2003 (+1.08°C/1.94°F)
2003 (+0.61°C/1.10°F)
2003 (+0.80°C/1.44°F)
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Southern Hemisphere
Land
Ocean
Land and Ocean
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+0.05°C (+0.09°F)
+0.31°C (+0.56°F)
+0.26°C (+0.47°F)
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49th warmest
7th warmest
12th warmest |
1884 (+1.42°C/2.56°F)
1998 (+0.42°C/0.76°F)
1998 (+0.47°C/0.85°F)
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June-August |
Anomaly |
Rank |
Warmest Year on Record |
Global
Land
Ocean
Land and Ocean |
+0.56°C (+1.01°F)
+0.37°C (+0.67°F)
+0.42°C (+0.76°F)
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9th warmest
5th warmest
6th warmest |
1998 (+0.97°C/1.75°F)
1998 (+0.50°C/1.00°F)
1998 (+0.64°C/1.15°F)
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Northern Hemisphere
Land
Ocean
Land and Ocean
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+0.60°C (+1.08°F)
+0.50°C (+0.90°F)
+0.54°C (+0.97°F)
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10th warmest
2nd warmest
5th warmest
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1998 (+1.00°C/1.80°F)
1998 (+0.56°C/1.01°F)
1998 (+0.73°C/1.31°F)
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Southern Hemisphere
Land
Ocean
Land and Ocean
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+0.34°C (+0.61°F)
+0.28°C (+0.50°F)
+0.29°C (+0.52°F)
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16th warmest
10th warmest
11th warmest
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1998 (+0.81°C/1.46°F)
1998 (+0.46°C/0.83°F)
1998 (+0.53°C/0.95°F)
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January-August |
Anomaly |
Rank |
Warmest Year on Record |
Global
Land
Ocean
Land and Ocean |
+0.80°C (+1.44°F)
+0.38°C (+0.68°F)
+0.51°C (+0.92°F)
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5th warmest
4th warmest
4th warmest |
2002 (+1.09°C/1.96°F)
1998 (+0.51°C/0.92°F)
1998 (+0.68°C/1.22°F)
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Northern Hemisphere
Land
Ocean
Land and Ocean
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+0.89°C (+1.60°F)
+0.46°C (+0.83°F)
+0.63°C (+1.13°F)
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5th warmest
2nd warmest
3rd warmest
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2002 (+1.21°C/2.18°F)
1998 (+0.53°C/0.95°F)
1998 (+0.77°C/1.39°F)
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Southern Hemisphere
Land
Ocean
Land and Ocean
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+0.43°C (+0.77°F)
+0.34°C (+0.61°F)
+0.36°C (+0.65°F)
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9th warmest
6th warmest
7th warmest
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1998 (+0.87°C/1.57°F)
1998 (+0.51°C/0.92°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.
Precipitation
The maps below represent anomaly values based on the GHCN data set of land surface stations using a base period of 1961-1990. The map to the left is precipitation anomalies measured in millimeters, the map to the right is the percentage of average (1961-1990) precipitation. During June-August 2004, much above average precipitation fell across the eastern half of the U.S., Scandinavia and western Europe. Below average precipitation was observed in Alaska, India and eastern Australia. During the month of August 2004, above average precipitation occurred in the southeastern U.S., Chile and coastal Alaska while drier than average conditions were observed in the southern Brazil, Malaysia and Norway.
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The satellite images below were acquired from SSM/I satellite data using a base period of 1988-2004. The map on the left reflects surface liquid wetness conditions, while the map on the right reflects snow cover conditions for the month. Snow covered areas that are normally snow-free during this month will appear drier than average on the wetness image since a wetness value cannot be determined for regions that are snow covered. Data in these areas that are normally snow covered are displayed as missing. This is due to the snow crystalline structure which produces a considerable amount of scatter and makes it difficult for the SSM/I to accurately detect the surface conditions. The SSM/I products are experimental and are under continuing review and development. Additional data and information can be found on the SSM/I Browser.
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Troposphere
Current Month / Seasonal
The tables below summarize mid-tropospheric conditions for August and June-August 2004. 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.) Analysis of the satellite record that began in 1979 indicates that global temperatures are increasing in the mid-troposphere, but the magnitude of the trend differs based on the analysis methods used in adjusting for factors such as orbital decay and inter-satellite differences. The 1979-2004 trend for August and June-August is 0.05°C/decade based on data from the University of Alabama at Huntsville (UAH). Based on data provided by Remote Sensing Systems (RSS) the trend for August and June-August is 0.13°C/decade. The base period used in both data sets is 1979-1998.
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August |
Anomaly |
Rank |
Warmest Year on Record |
| UAH mid-troposphere
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-0.06°C (-0.11°F)
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11th coolest
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1998 (+0.44°C/0.80°F)
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| RSS mid-troposphere
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+0.10°C (+0.18°F)
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9th warmest |
1998 (+0.51°C/0.92°F)
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