Average temperature in the United States
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Average Annual Temperature Trends in the United States
The average annual temperature across the contiguous United States has increased by about 1.2°F (0.7°C) from 1986–2016 compared to 1901–1960, and by 1.8°F (1.0°C) when looking at the period from 1895–2016. This warming trend is confirmed by both surface and satellite data, and recent decades are the warmest in the past 1,500 years. The frequency of cold waves has decreased, while heat waves have become more common since the mid-1960s. The number of high temperature records set in recent decades far exceeds the number of low temperature records, showing a clear warming pattern Vose2017Gerrard2018Meehl2016+2 MORE.
Regional and Seasonal Temperature Variations
Temperature changes are not uniform across the country. For example, from the 1920s to the mid-1950s, the average temperature in the United States decreased by about 1°F (0.6°C), with most of this cooling in the eastern states. In winter, the southeastern U.S. cooled by about 3°F (1.7°C), while the Far West saw warmer mean temperatures. Over the last century, the diurnal temperature range (the difference between daily maximum and minimum temperatures) has generally decreased, especially in fall and summer, with smaller decreases in spring and winter. This is due to minimum temperatures rising faster than maximum temperatures Diaz1980Qu2014Gil‐Alana2018+1 MORE.
Projections for Future U.S. Temperatures
Looking ahead, average annual temperatures in the U.S. are projected to rise by about 2.5°F (1.4°C) in the next few decades, regardless of greenhouse gas emission scenarios. By the end of the century, the increase could be between 2.8°F (1.6°C) and 7.3°F (4.1°C) under a lower emissions scenario, and between 5.8°F (3.2°C) and 11.9°F (6.6°C) under a higher emissions scenario. Extreme temperatures are expected to increase even more than average temperatures, with fewer days below freezing and more days above 90°F. The average summer high temperature could rise from a historical average of 74°F to 81°F by 2100, or even 91°F under high emissions Vose2017Gerrard2018.
Temperature Extremes and Record Highs
The ratio of daily record high temperatures to record low minimum temperatures has increased to about 2 to 1 in the early 21st century, indicating more frequent record highs. Climate models project this ratio will continue to rise as average temperatures increase, with a projected ratio of about 15 to 1 for a 3°C warming in U.S. temperatures Meehl2016Vose2017.
Economic and Environmental Impacts
Rising temperatures, especially in summer, have significant effects on the U.S. economy. A 1°F increase in average summer temperature is linked to a reduction in annual state-level economic growth by 0.15 to 0.25 percentage points. If current trends continue, U.S. economic growth could be reduced by up to one third over the next century due to higher temperatures .
Conclusion
The average temperature in the United States has risen significantly over the past century, with the most rapid warming occurring in recent decades. This trend is expected to continue, with even greater increases projected by the end of the century, especially if greenhouse gas emissions remain high. These changes are already affecting temperature extremes, regional climate patterns, and the economy, and will likely have even greater impacts in the future Vose2017Diaz1980Meehl2016+5 MORE.
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