There were no fireworks in Alaska’s largest city this week. The fire department determined that because of the extreme danger of wildfire, fireworks were just too risky. The city and others nearby continue to be in the grip of a historic heat wave, one that’s dried out vegetation and greatly increased the risk of devastating fires. Anchorage hit a record temperature of 90 degrees on Thursday — a higher temperature than could be found in most of the Lower 48 states from within a state that overlaps with the Arctic Circle.
Not that this happening is a surprise.
Below, we’ve taken data from the National Oceanic and Atmospheric Administration on average temperatures in each state and graphed relative changes over time. The complex explanation of what this shows? In each state, we determined the average of each year’s average temperatures over the course of the 20th century. For each year since 1919 in each state, we took the average of the prior 10 years’ average temperatures (a rolling average) and compared it to the 20th century average.
The simple explanation? Lines that go above the solid black lines are states in which the recent average temperature has been warmer than the 20th century in that state.
You’ll notice that in all 50 states, the rolling average temperature has been trending up fairly consistently for about 50 years. In no state is that figure lower than the 20th century average, nor has it been for at least a decade.
Alaska sits near the top of those lines. Earlier this year, the government announced that 2018 had been the fourth-warmest year on record, with the Arctic warming faster than the rest of the planet. Anchorage isn’t within the Arctic Circle, but it’s clear that Alaska’s increased warmth stands out even among U.S. states.
As of 2018, the last year for which there are complete data (obviously), it’s Rhode Island that’s had the biggest increase in warmth relative to the 20th century over the past decade. The New England state edged out Alaska and New Jersey for that title.
But Rhode Island is generally warmer than Alaska, for obvious reasons. In other words, the 2.7 degree increase over the 20th century average that Rhode Island has seen may be higher than Alaska’s 2.5 degrees — but since Alaska is generally colder, it has seen greater warming as a percentage of its 1901 to 2000 average. (Since Alaska’s temperatures are generally cooler/lower, there’s more volatility from shifts in temperatures.)
The state that’s seen the most modest change relative to its 20th century average is the usually-warmer state of Alabama. While the trend has been similar, the increase relative to the average from last century is more modest.
But notice that circle near the black horizontal line. That’s the figure for Alabama in 2001, the last time that the 10-year rolling average for any state was at or below the state’s 20th century average.
It’s been 17 years since that happened.
This, not Alaska’s specific shifts, is the important point. The trend is for states to see higher and higher temperatures relative to what they saw in the past century. To be warmer and warmer. While no single day of heat in any state is proof of a long-term trend, models developed by scientists studying climate change have suggested that such increases are precisely what we should be expecting to see as the globe warms.
When George W. Bush took office, states in the United States were on average about 0.8 degrees warmer over the preceding decade than they had been over the past century. When Barack Obama took office, that figure was 1.2 degrees. Last year, it was 1.6 degrees.
When Trump leaves office? The safe bet is that it will be higher still.