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This paper describes an improved edition of the climate division dataset for the conterminous United States (i.e., version 2). The first improvement is to the input data, which now include additional station networks, quality assurance reviews, and temperature bias adjustments. The second improvement is to the suite of climatic elements, which now includes both maximum and minimum temperatures. The third improvement is to the computational approach, which now employs climatologically aided interpolation to address topographic and network variability. Version 2 exhibits substantial differences from version 1 over the period 1895–2012. For example, divisional averages in version 2 tend to be cooler and wetter, particularly in mountainous areas of the western United States. Division-level trends in temperature and precipitation display greater spatial consistency in version 2. National-scale temperature trends in version 2 are comparable to those in the U.S. Historical Climatology Network whereas version 1 exhibits less warming as a result of historical changes in observing practices. Divisional errors in version 2 are likely less than 0.5°C for temperature and 20 mm for precipitation at the start of the record, falling rapidly thereafter. Overall, these results indicate that version 2 can supersede version 1 in both operational climate monitoring and applied climatic research.

Global temperatures in 2001 were 0.51°C (0.92°F) above the long-term (1880-2000) average, which places 2001 as the second warmest year in the 122-year instrumental record. Land temperatures were 0.75°C (1.35°F) above average and oceantemperatures were 0.40°C (0.72°F) above the 1880-2000 mean. This ranks them as the second and third warmest on record, respectively. The Northern Hemisphere temperature continued to average near record levels in 2001 at 0.60°C(1.08°F) above the long-term average. The Southern Hemisphere also reflects the globally warmer conditions, with a positive anomaly of 0.43°C (0.77°F). Annual anomalies in excess of 1.0°C (1.8°F) were widespread across North America and much of Europe and the Middle East, while significantly cooler than average conditions were confined to western Australia, the northeast and northwestPacific Ocean, and the far southeastern region of the Pacific, near coastal Chile. Although no hurricanes made landfall in the United States for the second consecut...