Us temperature averages
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U.S. Temperature Averages: Historical Trends and Future Projections
Historical Temperature Trends in the U.S. (1895-2010)
The analysis of U.S. temperature data reveals significant trends and variations over the past century. From 1895 to 2008, every month exhibited a positive linear trend in mean surface air temperature (SAT), with February showing the largest increase and September the smallest. This period also saw notable fluctuations, with the early 20th century experiencing marked warming, particularly from 1918 to 1947, while the late 19th and early 20th centuries were cooler.
NOAA's Climate Normals and Temperature Homogenization
The National Oceanic and Atmospheric Administration (NOAA) provides comprehensive climate normals, which are 30-year baseline averages of climatological variables. The latest installment, covering 1981-2010, includes state-of-the-art temperature homogenization and extensive use of quality-controlled daily climate data. These normals indicate that U.S. temperatures were approximately 0.5°F warmer on average from 1981 to 2010 compared to the previous period of 1971-2000.
Temperature Extremes and Record Highs
Temperature extremes in the U.S. have shown a significant shift, with the ratio of daily record high maximum temperatures to daily record low minimum temperatures increasing to about 2 to 1 in the first decade of the 21st century. This trend is projected to continue, with future projections indicating a ratio of approximately 15 to 1 for a 3°C warming in U.S. temperatures. Model simulations suggest even higher ratios, potentially reaching 50 to 1 by the end of the century under certain emission scenarios.
Spatial and Temporal Variability
Temperature changes in the U.S. exhibit spatial variability, with the eastern U.S. generally experiencing smaller sampling error variances due to higher station density, while mountainous and coastal areas show larger variances. Over the past 25 years, the average temperature of the U.S. has decreased by about 1°F, primarily in the eastern regions, while the western regions have seen warmer mean temperatures.
Methodological Enhancements in Temperature Averaging
Traditional methods of calculating daily average temperatures, which use the mean of maximum and minimum temperatures, have been compared to methods using hourly temperature data. The latter provides a more precise and representative estimate of daily temperatures, highlighting the importance of methodological advancements in climate data analysis.
Conclusion
The study of U.S. temperature averages reveals a clear trend of increasing temperatures over the past century, with significant spatial and temporal variability. The shift towards higher temperature extremes and the methodological improvements in climate data analysis underscore the importance of continuous monitoring and updating of climate normals to better understand and respond to ongoing climatic changes.
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