How Climate Change Showed Up in 2021
2021 was tied for the sixth-hottest year since modern record keeping began. We work together with the National Oceanic and Atmospheric Administration to track temperatures around the world and study how they change from year to year.
For decades, the overall global temperature has been increasing because of human activities. The last decade has been the warmest on record. Each individual year’s average temperature, however, can be affected by things like ocean circulation, volcanic eruptions, and specific weather events.
For instance, last year we saw the beginning of La Niña – a pattern of cooler waters in the Pacific – that was responsible for slightly cooling 2021’s average temperature. Still, last year continued a long-term trend of global warming.
Globally, Earth’s temperature in 2021 was nearly 2°F warmer than the late 19th Century, for the seventh year in a row.
Since 1880, we can put together a consistent record of temperatures around the planet and see that it was much colder in the late-19th century. Before 1880, uncertainties in tracking global temperatures are larger. Temperatures have increased even faster since the 1970s, the result of increasing greenhouse gases in the atmosphere.
Tracking Millions of Individual Observations
Our scientists use millions of individual observations of data from more than 20,000 weather stations and Antarctic research stations, together with ship- and buoy-based observations of sea surface temperatures, to track global temperatures.
Reviewing Multiple Independent Records
Our global temperature record – GISTEMP – is one of a number of independent global temperature records, all of which show the same pattern of warming.
Everywhere Experiences Climate Change Differently
As Earth warms, temperature changes occur unevenly around the globe. The Arctic is currently warming about four times faster than the rest of the planet – a process called Arctic amplification. Similarly, urban areas tend to warm faster than rural areas, partly because building materials like asphalt, steel and concrete retain heat.
Droughts and Floods in Warmer Weather
More than 88% of the Western US experienced drought conditions in 2021. At the same time, communities in Western Europe saw two months’ worth of rain in 24 hours, breaking records and triggering flash floods. Because a hotter climate means more water can be carried in the atmosphere, areas like the Western US suffer drought from the increased 'thirstiness' of the atmosphere, while precipitation events can become more extreme as the amount of moisture in the atmosphere rises.
Sea Levels Continue to Rise
Melting ice raises sea levels around the world, as meltwater drains into the ocean. In addition, heat causes the ocean water to expand. From 1993 to today, global mean sea level has been rising around 3.4 millimeters per year. In 2021, sea level data from the recently launched NASA/ESA Sentinel-6 Michael Freilich mission became available to the public.
“This is not good news, but the fact that we are able to track this in real time and understand why it’s changing, and get people to notice why it’s changing and how we can change things to change the next trajectory, that gives me hope. Because we’re not in the dark here. We’re not the dinosaurs who are unaware the comet is coming. We can see the comet coming, and we can act.” – Dr. Gavin Schmidt, director of NASA GISS, where the global temperature record is calculated
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