From NOAA’s Global Climate Report – December 2021:
The December 2021 global surface temperature tied with 2016 as the fifth highest in the 142-year record at 0.83°C (1.49°F) above the 20th century average. Eight of the 10 warmest Decembers have occurred since 2014. December 2021 also marked the 37th consecutive December and the 444th consecutive month with temperatures, at least nominally, above the 20th century average.
During the month of December, the most notable warm temperature departures were present across much of the contiguous U.S. and across parts of eastern Canada, northern Mexico, and southern Asia, where temperatures were at least 2.5°C (4.5°F) above average. Record-warm December temperatures were present across a large area of the southwestern Pacific Ocean and small areas across North America, South America, Africa, Asia, and the Atlantic Ocean. Meanwhile, the most notable cool temperatures were observed across the western half of Canada and across parts of Scandinavia and northern Russia. However, no land or ocean areas had a record-cold December temperature.
Time series data is available at the top of the page.