Record-Breaking Temperatures: Seasonal and Monthly Trends Over the Conterminous U.S

In a stationary climate, the number of record-breaking temperatures would be expected to decrease over time, as established records become increasingly more difficult to break. This inherent trend in the number of record-breaking events confounds the interpretation of actual trends in the presence of any underlying climate change. Using a simple technique developed by Rowe and Derry (2012) to remove this inherent trend, any remaining trend can be examined separately for evidence of a climate change. Results from that study indicate that the annual number of record low daily minimum temperatures is steadily decreasing nearly everywhere across the United States while the annual number of record high daily minimum temperatures is predominantly increasing. Trends in annual record low and record high daily maximum temperatures are generally smaller and more spatially mixed in sign. These general results agree well with the changes expected with a warming climate.

Here, trends in the number of record*-breaking temperatures are investigated for seasonal and monthly periods, rather than for the entire year, to explore further their utility in climate change detection.