Us temperature trends by year
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U.S. Surface Air Temperature Trends by Year
Long-Term Warming Trends in the United States
Across the contiguous United States, average annual temperatures have shown a clear warming trend over the past century. From 1895 to 2016, the average temperature increased by about 1.8°F (1.0°C), with more rapid warming observed since 1979. Recent decades are the warmest in at least the past 1,500 years, based on multiple lines of evidence . Every month from January to December has experienced a positive linear temperature trend from 1895 to 2008, with February showing the largest increase and September the smallest .
Regional and Seasonal Variations in Temperature Trends
Warming is most pronounced in the Northeast, West, and northern Midwest, while the Southeast has experienced slight cooling in some periods . In the Southwest United States, 75% of weather stations recorded increasing annual maximum temperatures, with rates ranging from 0.6 to 3.1°C per century. Minimum temperatures also increased at most stations, and the temperature range (difference between maximum and minimum) has generally decreased . The deserts of the Southwest, especially urban areas, have seen significant increases in minimum temperatures, highlighting the impact of urban heat islands .
Maximum and Minimum Temperature Changes
Both maximum and minimum temperatures have shown significant positive trends since 1895, but minimum temperatures have increased more rapidly, leading to a narrowing of the daily temperature range Gil‐Alana2018Djaman2020Brazel2019. In the last century, some states like New Jersey and Rhode Island have seen temperature increases of nearly 2.9°C .
Trends in Temperature Extremes
There have been marked changes in temperature extremes. The frequency of cold waves has decreased since the early 1900s, 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 Vose2017Degaetano2002. Warm minimum temperature extremes have increased at nearly one-third of stations, especially in urban areas, while extremely cold temperature occurrences have decreased .
Year-to-Year Volatility and Persistence
Recent research shows that the volatility of daily maximum temperatures—how much temperatures swing from day to day—has increased in much of the Central United States, with trends of about 0.2–0.3°C per decade since 1950. This increased volatility is seen as another sign of climate change . Additionally, temperature records show evidence of long-term persistence, meaning that temperature changes tend to last over time rather than being short-lived fluctuations Gil‐Alana2018Gil‐Alana2019.
Projections for Future U.S. Temperature Trends
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 under all emissions scenarios. By the end of the century, increases could range from 2.8°–7.3°F (1.6°–4.1°C) in a lower emissions scenario to 5.8°–11.9°F (3.2°–6.6°C) in a higher emissions scenario. Extreme temperatures are expected to increase even more than average temperatures, with fewer cold days and more days above 90°F .
Conclusion
In summary, U.S. temperature records show a clear and persistent warming trend over the past century, with regional and seasonal variations. Both maximum and minimum temperatures are rising, with minimums increasing faster, and temperature extremes are shifting toward more frequent heat events and fewer cold events. These trends are expected to continue and intensify in the coming decades.
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