The stated purpose of the U.S. National Assessment's Climate Change Impacts on the United States; The Potential Consequences of Climate Variability and Change (USNA) is to "assess the risks and opportunities for the United States...associated with increased climate change." But the USNA has turned out to be one of the most misleading publicly funded reports on climate change this nation has ever produced. The two climate models on which it is primarily based—one developed by the Canadian Climate Centre and the other by the Hadley Centre in the United Kingdom—cannot correctly reproduce observed climate. What's more, the two models often produce markedly different forecasts of future climate. • In addition to large-scale inaccuracies, the models' spatial resolution is too coarse to include most small-scale processes—the type of processes responsible for local weather patterns. Yet the USNA breaks the country into eight regions and within each region depicts local ecosystem changes as a result of their predicted climate trends during the next 100 years. In this continuing series, we examine in detail each of those regions, comparing the observations of the past century with the USNA's climate model prognostications for the next.
 

Is It Warming In The Northwest? I Dunno, Alaska

The BBC News website's recent report on warming in Alaska suggested that the state's climate change and related trouble is somewhat self-inflicted, in the sense that the oil industry generates 80 percent of Alaska's economy. Burning that oil for energy adds carbon dioxide to the atmosphere. What happens next appears in the USNA Regional Assessment of the effects of climate change in Alaska, a likely source for much of the information in the BBC story.

The warmup brings with it a host of problems: Thinner walruses (who must exert more energy looking for food now); smaller self-reliant seals (apparently young seals have to leave the safety of the ice sooner because it is melting), and a changing diet for killer whales (who have started eating otters as seals and fish become harder to find). As if this disruption to the wildlife isn't bad enough, a slow melting of the permafrost in some regions is causing the foundations of roadways and buildings to start to collapse.

According to the USNA, "Alaska has warmed substantially over the 20th century, particularly over the past few decades. Average warming since the 1950s has been 4°F (2°C). The largest warming, about 7°F (4°C), has occurred in the interior in winter." The BBC chose to report that "Scientists say the average winter temperature in Alaska has risen by 4°C in the last 40 years. This rate is about 10 times faster than most of the rest of the world." Note quite what the USNA said, but, good enough for liberal media work.

What you don't find out about by reading the liberal media, however, is how much fun and games you can have with the numbers. We'll give you a little demonstration using the temperature history from three Alaskan stations, spread out across the state—Anchorage in the south, Fairbanks in the interior, and Barrow in the north.

Figure 1(a) shows the winter (December–February) temperature trend for the average of the three stations for the past 40 years (1963–2002). The three-station average is +.82°C/decade, or a total increase of 3.28°C—pretty close to the BBC/USNA number. If that warming is human-caused, then trends in the more recent decades should be as large or larger than the trend over the past 40 years. Figure 1(b) shows the winter temperature trend since 1977 (the past 25 years). The three-station average is –0.50°C/decade (a decrease, though not statistically significant). What about the longer term? Figure 1(c) shows winter temperatures since good records began in each station. The three-station average during the period of overlap (1930–2002) is 0.29°C/decade, less than three times the rate of the past 40 years. In fact, the average winter temperature of the first five years of the 1940s was warmer than that of the past five winters.

Figure 1. Combined average winter temperature history for Anchorage, Fairbanks, and Barrow, 1963 to 2002 (a), 1977 to 2002 (b), and 1930 to 2002 (c).

What does all that mean? Well, despite a gradual buildup of atmospheric greenhouse gases, the temperature change in Alaska has been anything but gradual. So it's hard to argue that the temperature rise during the past 40 years is due to the effects of burning oil (and other fossil fuels), especially when there has not been a rise during the past 25 years.

What's going on? Figure 2 shows the time history of the Pacific Decadal Oscillation (PDO)—a natural multidecadal swing in temperature over the Pacific Ocean. Notice how similar the pattern of Alaskan winter temperatures is to the PDO index. The PDO switched from a warm phase to a cool phase in the mid-1940s and then back to a warm phase in the mid-1970s—a pattern mimicked by winter temperature in Alaska. Why does the PDO switch phases? That is still anybody's guess, but one thing that is nearly certain is that it has been doing so since before memory and will continue to do so into the future. As goes the PDO, so go temperatures in Alaska, the weight of walruses, and the diet of killer whales...with or without "global warming."

 

Figure 2. History of the Pacific Decadal Oscillation (PDO), 1930 to 2002. Note the similarity between this index and the 1930 to 2002 Alaskan temperature history from Figure 1(c).