It will likely come as no surprise that 2020 held another record that we wish it didn’t: hottest year on record. While technically tied with 2016, 2020 now holds the record of 1.84 degrees Fahrenheit warmer than the baseline 1951-1980 mean. That’s equivalent to 1.02 degrees Celsius.
Scientists from NASA’s Goddard Institute for Space Studies (GISS) say that more than looking at the peaks in climate patterns, which are alarming in themselves, we need to be concerned by the overall upward slope of temperature that has been increasing at unprecedented rates.
"The last seven years have been the warmest seven years on record, typifying the ongoing and dramatic warming trend," said GISS Director Gavin Schmidt. "Whether one year is a record or not is not really that important -- the important things are long-term trends. With these trends, and as the human impact on the climate increases, we have to expect that records will continue to be broken."
This trend has been present since the end of the 1800s due to anthropogenic activities related to greenhouse gas emissions. In the last century and a half, Earth's average temperature has risen over 2 degrees Fahrenheit, or 1.2 degrees Celsius.
NASA's raw data comes from a wide range of sources: satellites, airborne and ground-based observations, as well as surface temperature measurements from over 26,000 weather stations and thousands of ship- and buoy-based observations of sea surface temperatures. You can access NASA's full surface temperature data set as well as information on the methodology used in calculations here.
While every year has distinct factors that influence yearly temperatures, such as the Australian bush fires and the reduction in air pollution due to the coronavirus pandemic, the most significant source of year-to-year variability in global temperatures is the El Niño-Southern Oscillation (ENSO). ENSO is a naturally occurring cycle of heat exchange between the ocean and atmosphere. Watch the video below to learn more about how ENSO influences climate patterns.
As Schmidt explains, ENSO 2020 began in a warm phase and ended in a cool phase. “The previous record warm year, 2016, received a significant boost from a strong El Niño. The lack of a similar assist from El Niño this year is evidence that the background climate continues to warm due to greenhouse gases." That means that despite the reduction in greenhouse gas emissions due to pandemic shutdowns, overall cumulative CO2 concentrations continued to increase, ultimately making the amount of avoided warming nominal.