NASA and the European European Copernicus Climate Change Service have ranked 2020 as tied for the hottest year on record (with 2016). NOAA ranks 2020 as the second warmest year on record while the Japanese Meteorological Agency has ranked 2020 as the warmest year on record. Differences between agencies are the result of slightly different ways in which each group handles data-sparse regions such as the Arctic. Regardless, 2020 has continued the long-term global warming trend.
Total global ocean heat content was higher in 2020 than in at any point in recorded human history. Approximately 90% of the increase in heat from global warming is accumulated in the world’s oceans, making the oceans one of the most important parts of the global climate system.
The warmth of 2020 was perhaps more remarkable than previous warm record years, as it occurred during a deep solar minimum (i.e. a period when sunspot and solar activity is minimal, usually resulting in a slight cooling of Earth) and a period where no strong El Niño was present. The fact that these naturally cooling events were in place during a record-breaking warm year further highlights the impact of human-caused warming.
For an excellent recap of the global climate and some of the records that were set in 2020, see Dr. Jeff Masters “Eye on the Storm” post on the Yale Climate Connections website.