DefinitionTemperature measurements over time have been the primary method of assessing the occurrence of climate change, with higher temperatures indicating warmth and lower temperatures indicating coolness.
Why Is This Important?Over the past century, global surface temperatures have increased, yet the warming is not consistent across the globe. Areas such as the southeast United States have actually seen cooler temperatures. Yet, when looking at the eight hottest years on record, seven of those years have occurred since 2001 (1). When looking at temperature change in the atmosphere, the troposphere (the level of atmosphere five to eight miles from the Earth's surface) has shown an increase in temperature since the 1970s. Yet the stratosphere (the level of atmosphere 9 to 14 miles from the Earth's surface) has cooled over this period of time (2).
Climate experts have also studied whether temperature extremes are affected by climate change. The National Oceanic and Atmospheric Administration stated that differences between maximum temperatures and minimum temperatures, known as the diurnal temperature range, have been diminishing for most of the planet since the mid-20th century. Minimum temperatures have increased more quickly than maximum temperatures, resulting in fewer extreme cold days and nights and a higher occurrence of extreme warm days and nights (1).