Temperature

Temperature

Recent years have brought many temperature extremes to Alaska, including the warmest year (2016), the warmest month (July 2019), and in places like Anchorage, the warmest day (July 4, 2019). Air temperatures in Alaska are rising twice as fast as in other parts of the United States and, apart from sea ice, are the most obvious sign of change.

Factors contributing to this warming include decreases in sea ice and snow cover, warming ocean, and increasing greenhouse gases. Of course, there is considerable day-to-day and even year-to-year variability, depending on average storm tracks, but these trends are unmistakable.

Warmer temperatures

Annual average temperatures are widely used as a measure for long term changes, and modern techniques allow reasonable estimates of temperatures over large areas back to the 1800s. Temperatures in and around Alaska have been rising since the 1970s, with typical annual average statewide temperatures now 3 to 4ºF warmer than during the early and mid-20th century. Recent years have all been exceptionally warm. In fact, four of the past five years (2014–16, 2018) were warmer than any year prior to 2014.

Fewer very cold days

One of the most dramatic changes in interior and northern Alaska has been the decrease in the number of very cold days in winter. This graphic shows that the typical number of days in Northway, Alaska with low temperatures of -30ºF or lower has fallen from more than 40 days prior to 1960 to less than 30 days in the past decade. This trend is representative of most interior Alaska locations, including Fairbanks.

Record highs outnumber lows

Daily high and low temperature records are a widely reported measure of extreme weather. Given a stable climate (i.e., no warming or cooling trend) we would expect fewer than 10 percent of both high and low daily temperature records, for the period 1953–2018, to have been set during the past five years. However, since 2014, there have been five to 30 times more record highs set than record lows.

Fall and winter warmer than average

2014–2018 average temperatures in most regions and seasons have been dramatically warmer than the average for 1981–2010. The exception is summer, when the past five years have been close to normal over much of the state.

Greatest warming in west and north

Temperatures are rising all across the state, but not uniformly. The changes are largest over northern and western Alaska, where snow and especially sea ice losses are impacting the regional climate. Temperatures have risen least dramatically in southeast Alaska and the Aleutians, where seasonal snowpack changes and sea ice are more indirect factors.

Utqiaġvik high temperatures

The abrupt change in air temperatures due to the loss of sea ice is nowhere more obvious than in Utqiaġvik (formerly Barrow) during the month of October. Direct heating from the sun is weak during October, so the autumn air temperatures are controlled by the amount of open water offshore of Utqiaġvik.

Prior to 2002, many Octobers had extensive ice through the entire month or at least by late October, allowing for much lower temperatures. In recent years, open water remained late into fall, and air temperatures were consistently warmer relative to the past.