It’s easy to assume that the pattern since 2010 has been one of a steady, universal increase in heat across the planet. But, although that is the long-term track, there has been wide variance in temperatures across the planet over the past 10 years.
The National Oceanic and Atmospheric Administration offers data on land and ocean temperatures for discrete areas on the planet’s surface. We pulled the year-to-date (that is, January through November) values for every 5-degree square of latitude and longitude for each year from 2010 through 2019 and plotted the results. What’s shown below is not temperatures, as such, but the variation for the first 11 months of each year from the average temperature over those months during the 20th century.
This is the result. Blue lines indicate a 2019 value under the 20th century average. Light red lines, a 2019 value above the average. Dark red? A value at least 2 degrees above the average.
You’ll need to zoom in on the image to see individual locations. We’ve pulled out North America below to show the variation that can be seen in the data.
Much of the middle of the country, you’ll notice, has seen lower-than-average temperatures so far this year (the lines in blue). That almost always follows variance in the values over the decade, with years where the temperature was much higher than average trailing years in which the temperature was lower.
Most remarkable here is Alaska, where temperatures relative to the average have risen more steadily and now easily outpace the 20th-century average. The consequences can be dire, with thawing permafrost destabilizing structures and threatening to release more greenhouse gases from decomposing vegetation into the atmosphere.
Across the globe, the most recent year-to-date values (from 2018 or 2019, depending on the location) are generally warmer than the 20th-century average. In places like Alaska and northern Russia, temperatures are much warmer.
Again, though, the middle of the contiguous United States has seen relatively low temperatures.
That wasn’t the case in the hottest year on record, 2016. Then, the United States was almost entirely warmer than average. There were still spots around the globe where temperatures from January to November were lower than the average from last century, but not many.
Given the volatility of the changes in temperature by location, a comparison between year-to-date temperatures in 2010 and 2019 shows a relatively diverse result. Most of North America (except Alaska) was cooler during the first 11 months of 2019 than in 2010, as was much of Saharan Africa and Southeast Asia.
Looking at the data since 2010 another way, though, shows the real problem. If we calculate the number of years from 2010 to 2019 in which the year-to-date temperatures were above the 20th-century average, we can get a better sense for how the decade went. More blue locations had fewer years that were above average; more red locations saw more years with January-to-November temperatures above the average.
That’s what the hottest decade in recorded history looks like.