Environment & Climate

In 1980, the average US county had good air quality 59% of days. In 2018, the average county had good air quality 81% of days.

Adjusting for population change, Hawaii had the largest decrease in air quality per square mile between 1980 and 2018, partially due to volcanic air pollution, while Missouri had the largest improvement.

Sources & Footnotes

“Good air quality” is defined by the EPA as having an air quality index (AQI) value between 0 and 50. The AQI is based on the concentration of five criteria pollutants including carbon monoxide and particulate matter.

Environment & Climate

The annual rate of precipitation for the contiguous US was 5% higher on average at the beginning of the 21th century (2005-2019) than it was at the beginning of the 20th century (1895-1909) .

Sources & Footnotes

Environment & Climate

California had a greater drop in average annual precipitation over the past century compared to any other state.

Sources & Footnotes

Environment & Climate

2019 was the second-warmest year globally in the 140-year record, with temperatures 1.71°F (0.95°C) warmer than the 20th century average. 2016 was the warmest year on record.

Global temperatures have been warmer than the 20th century average ever since 1977.

Sources & Footnotes

Environment & Climate

Between 1895 and 2019, the average temperature in 50% of US counties rose more than 2.7°F (1.5°C), a key threshold of climate warming identified by NASA.

In six states —North Carolina, South Carolina, Alabama, Delaware, and New Jersey— the average temperature in all counties rose more than 2.7°F.

Sources & Footnotes

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