From NOAA’s Global Climate Report – Annual 2021:
The year 2021 began with an episode of cold phase El Niño Southern Oscillation (ENSO) episode, also known as La Niña, across the central and eastern tropical Pacific Ocean, which had developed in August 2020. As seen in the graph below, ENSO can have an effect on global temperatures. La Niña episodes tend to cool global temperatures slightly, while the warm phase ENSO (also known as El Niño) tends to boost global temperatures. Although the monthly global temperatures were above average throughout the year, February 2021 was the coldest month of 2021 for the globe. The global temperature departure for February 2021 was +0.64°C (+1.15°F) — the coolest February since 2014. However, after the month of February, temperatures were at 0.80°C (1.44°F) or higher for the remaining months of 2021.
The net result:
The year culminated as the sixth warmest year on record for the globe with a temperature that was 0.84°C (1.51°F) above the 20th century average. The years 2013–2021 all rank among the ten warmest years on record.
Time series data available at the top. ENSO status data must be somewhere but there doesn’t appear to be a link; just the graph.