Globally, temperature has been rising as the CO2 from burning of fossil fuels insulates the earth. The most pronounced warming has occurred in the last several decades, especially in the arctic.
But that’s a global average. I also really want to know what’s happening right here. So, I had some fun staring at the more-local temperature graphs. Looking at Alaska specifically, temperature records only go back to 1949, and basically consist of a cold half (1949-1976) and a warm half (1977-today). So even Hig, who grew up here, never experienced that cold. During the cold half, the Pacific Decadal Oscillation (a natural cycle of ocean temperatures with a time frame of 20-30 years) brought cold waters to the eastern North Pacific, and warm waters to the western North Pacific – making Alaska cooler. In the late 1970s, the Pacific Decadal Oscillation switched, and Alaska got warm.
What next? Well, the Pacific Decadal Oscillation appears to be dropping back into a persistently cold phase, and if that was the only big factor here, I’d expect to see Alaska dipping back down into those 1949-1976 temperatures along with it. Actually, I’d expect that to have happened already, given the PDO in the last few years has been as low as it was in the early 70s. But human-caused climate change introduces a consistent and increasing warming trend, which coexists with natural variation.
So, cool periods get less cool, and warm periods get even warmer. Average temperatures will continue to climb, more rapidly during natural warm cycles, and more rapidly as the carbon dioxide levels in the atmosphere continue to increase. We might never see temperatures as cold as the 1949-1979 average again – certainly not over any extended time frame. And next time the Pacific Decadal Oscillation shifts into a warm phase, we’ll probably see temperatures shoot well above the exceptionally warm years seen in the early 2000s. The latest report by the USGS shows predicted temperature increases across the state for the 21st century, against a reference frame of 1971 to 2000 temperatures (a period already dominated by warm). The degree of future change is predicted to be greatest in the northwestern regions of the state, and greatest during winter months, as has been true of the warming Alaska has already experienced.
From this USGS report: left shows a higher emissions (A2) and right a lower emissions (B2) scenario for the years 2070-2099.
The narrow time frame of recorded temperatures and the high natural variability of Alaska climate makes local temperature trends difficult to pick out from measurements alone. Global data is much more robust, and shows warming trends more clearly. But temperature measurements aren’t our only signal. Alaska’s overall warming trend is clearly visible in its natural systems, including melting permafrost, shrinking glaciers, advancing trees and shrubs, disappearing sea ice, dramatic coastal erosion, and changing species distributions.