U.S. Temperatures are rising dramatically

Map of July US Temperature, 1981-2010 prepared by NOAA

Pro: It’s Clear the US is Heating Up

U.S. and Global Temperature. Average temperatures have risen across the contiguous 48 states since 1901, with an increased rate of warming over the past 30 years. Eight of the top 10 warmest years on record have occurred since 1998. Average global temperatures show a similar trend, and all of the top 10 warmest years on record worldwide have occurred since 1998. Within the United States, temperatures in parts of the North, the West, and Alaska have increased the most. 

High and Low Temperatures. Many extreme temperature conditions are becoming more common. Since the 1970s, unusually hot summer days (highs) have become more common over the last few decades in the United States. Unusually hot summer nights (lows) have become more common at an even faster rate. This trend indicates less “cooling off” at night. Although the United States has experienced many winters with unusually low temperatures, unusually cold winter temperatures have become less common—particularly very cold nights (lows). Record-setting daily high temperatures have become more common than record lows. The decade from 2000 to 2009 had twice as many record highs as record lows.


In recent years, scientists have noted a rapid increase in average temperatures throughout the country. According to a report from the National Resources Defense Council (NRDC) titled ‘Killer Summer Heat,’ the average temperature of the United States could rise by as many as 11 degrees Fahrenheit by the end of the 21st century. “The risks to public health are greatest when high temperatures mix with other weather conditions to cause what’s known as an ‘Excessive Heat Event,’ or EHE,” the report states. EHE days occur when the temperature, dew point temperature, cloud cover, wind speed and surface atmospheric pressure create conditions dangerous enough to cause heat-related deaths.


Con: There are No Real Warming Trends in the US

There has been no significant warming in the United States since at least 2005.  Any claimed recent warming and impacts at specific places in the United States are isolated and indicate random variation rather than long-term warming.

Claims of long-term U.S. warming are controversial. Thermometer readings in the United States report current temperatures are similar to the temperatures recorded 80 years ago.

The United States has experienced no significant warming since at least 2005. The lack of warming is documented by the National Oceanic and Atmospheric Administration’s U.S. Climate Reference Network, an extremely accurate network of temperature stations throughout the United States that requires no corrective adjustments. (It began reporting temperature data in 2005.) When climate activists claim specific impacts of global warming in the United States, those impacts could not have been caused by any recent warming because no significant recent U.S. warming has occurred.

Figure 1: U.S. Temperature Trend Since 2005

Source: Data provided by U.S. Climate Reference Network, National Oceanic and Atmospheric Administration, accessed January 2020: https://www.ncdc.noaa.gov/crn. Chart provided by meteorologist Anthony Watts.

Longer-term warming in the United States has been modest, at most. Thermometer readings report current temperatures are no higher than they were 80 years ago. This has been masked in large part by government gatekeepers who have inexplicably adjusted temperatures from past decades downward, making it appear as though recent temperatures have risen more than they have. Raw data show current temperatures are approximately the same as they were in the 1930s.

Figure 2: Long-Term U.S. Temperature Measurements vs. Adjusted Temperature Reports

Figure 2: The blue line represents unadjusted thermometer readings, which show temperatures are no higher now than they were 80 years ago. Source: Tony Heller, “61% Of NOAA USHCN Adjusted Temperature Data Is Now Fake,” realclimatescience.com, February 11, 2019: https://realclimatescience.com/2019/02/61-of-noaa-ushcn-adjusted-temperature-data-is-now-fake

Additional Information: Anthony Watts, “Is the U.S. Surface Temperature Record Reliable?,” March 1, 2009: https://www.heartland.org/publications-resources/publications/is-the-us-surface-temperature-record-reliable

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