Global temperatures for January 2021 and long-term trends

January 2021 ended up as the 6th warmest January on record globally for land/ocean surface combined, according to NASA GISS.

The global average temperature for last month was 0.86 of a degree Celsius above the 1951-1980 mean. The warmest January on record occurred in 2020, with a temperature departure of +1.18 C. I suspect the strengthening La Nina (can have a cooling influence on global average temperature) in the equatorial Pacific during the second half of 2020 and into early 2021 likely played a role in keeping January 2021 out of the top five.

As you can see by the above image, a vast majority of northern North America and the Arctic was well above normal in terms of average temperature. However, that clearly changed in February as an extreme cold air mass settled in across the western two-thirds of Canada and deep into the U.S. Plains.

Long-term trends and projections

NASA GISS has put together two striking images that tell a big story about the longer-term changes in global temperature.

The above image shows the global temperature anomalies (measured against the 1951-1980 mean) by decade, going back to the start of the 20th century.

The second image below shows the global average temperature anomalies by month since 1901. The warming trend is clear and very pronounced, especially since the early 1990s.

Not surprisingly, the greatest warming relative to normal has been over the Arctic region, where the steady loss in sea ice has exposed more open water. The darker colored waters are able to absorb more of the sun's energy compared to the lighter colored ice, which results in more pronounced warming compared to the rest of the planet.

The Arctic region is warming at about twice the rate as the rest of the planet (light blue line on the top left graph).

The graph below shows the long-term global temperature trend versus the three greenhouse gas emission scenarios, with scenario A showing the temperature projections under the highest emissions, B under moderate emissions and C lower or reduced emissions.

What we see from the graph is that the world was running very close to scenario B and C through about 2005 then trended closer to scenario C between 2005 and 2014. Since 2015, the world is running closest to the temperature projections from scenario B.

Clearly, global climate models have so far done a pretty good job with long-term warming projections.