TCS Daily

What Defines the Arctic? A Discussion of the Arctic Climate Impact Assessment

By Willie Soon - December 20, 2004 12:00 AM

The Arctic and what is happening to it was a central concern at last week's United Nations' 10th annual Conference of the Parties (COP-10) on climate change in Buenos Aires.

An overview of an intergovernmental report by the Arctic Council -- the Arctic Climate Impact Assessment (ACIA) -- issued last month announced[1] that "The Arctic is warming much more rapidly than previously known".

Already, environmentalists are making the case for legal action by Arctic peoples and others affected by the Arctic's changing temperature to punish producers of carbon dioxide and other greenhouse gases they blame for creating the problem.

All of this is going on before the Arctic Council has released the scientific basis for its overview. Doubts have already been raised about the temperature record ACIA showed.

The ACIA Overview report included a curve representing the variability in "Arctic" surface air temperatures from 1900 to 2002 (Figure 1). In looking at the graph, a fundamental question arises: What, in this context, does "Arctic" mean?

There is the astronomical definition of the Arctic, which is defined by the Arctic Circle at 66.5ºN, where there is at least one 24-hour day and one 24-hour night each year. There is the ancient Greek definition, which divided the world into three zones -- the Torrid, the Temperate and the Frigid -- which would make the Arctic Frigid third start at 60ºN. And then there are definitions used to create the temperature record. It is an important matter because the temperature record differs with each Arctic definition. Where one looks often determines what one measures. Which brings us to Figure 1.

Figure 1: The "Arctic" temperature anomaly record from 1900-2002 as shown in the ACIA Overview report (2004) based on land temperature stations poleward of 60ºN from the Global Historical Climatology Network (GHCN) database.

In the context of the ACIA report, the Arctic, according to its lead author for Chapter 9, Harald Loeng, is two-thirds ocean. Yet, the ACIA study used only land-based temperature records poleward of 60ºN from the Global Historical Climatology Network (GHCN).

A study produced last year by Igor Polyakov of the International Arctic Research Center and his colleagues weighed poleward data above 62ºN including coastal land stations, Russia's drifting stations around the North Pole and the buoys of the International Buoy Programme, considering them to provide a more representative surface air temperature for the mostly oceanic Arctic region.

Figure 2: The Arctic-wide composite surface air temperature (SAT) anomaly from 1875-2001 based on the work of Igor Polyakov and colleagues which considered data poleward of 62ºN from coastal land stations, Russian drifting stations around North Pole and drifting buoys from International Buoy Programme.

Both Figures 1 and 2 show warming trends in the Arctic starting about 1980. But the ACIA (Figure 1) curve suggests a stronger warming[2] occurred during the period from 1980 to 2002 than an earlier warming that occurred in the 1920s-1930s. The Polyakov curve of Figure 2, meanwhile, shows the recent warming trend, but it is weaker than that seen in Figure 1. Furthermore, the warming in the 1920s and 1930s is more pronounced than that in the 1980s. Indeed, authors of Figure 2 had interpreted Arctic-wide warming and cooling trends as natural, undercutting the impression left from ACIA's Figure 1 of a rapid, continuous, unnatural warming trend.

Yet another Arctic temperature curve, though, needs to be added to those two.

This third curve comes from a paper presented by the authors of Chapter 2 of the ACIA Overview report that contained the curve in Figure 1. The third curve (shown in Figure 3) was presented at the ACIA International Symposium held in Reykjavik, Iceland from November 9-12 this year. It appears to be more recent than Figure 1 as published in the ACIA Overview Report, and more alarming in its temperature trend.

Figure 3: The Arctic temperature anomaly record from 1880-2002 shown by the authors of chapter 2 of the ACIA Overview report (2004) for the November 9-12's ACIA International Symposium held at Reykjavik, Iceland. Note that ACIA's portrayal of a high value for 2002 and a large recent warming trend (smoothed solid curve) are undeniable.

Indeed, Figure 3 shows an Arctic temperature anomaly (the difference of the temperature of a given year from the mean for the period of years used as a reference base) for 2002 now higher than 1.5ºC (2.7ºF) on the chart's scale, significantly larger than the value for 2002 in Figure 1. In addition, the smoothed trend curve for Arctic warming is much stronger than that implied by Figure 1.

In their extended abstract for the ACIA symposium, the authors wrote:

"for the period 1966-2002, the average [warming] over the [Arctic] region was 0.38ºC/decade, approximately 4 times greater than the average for the century."

A closer inspection reveals that 1966 and 2002 correspond exactly to the lowest and highest smoothed annual temperature values for the Arctic temperature in that interval. By simply choosing a different starting point on the curve within that time frame, the warming trend diminishes, a fact demonstrated by the authors themselves, as the increase in the pitch of their curve in Figure 1 for 1993-2002 is less steep than it is in Figure 3 for the same period. Which is correct?

That brings us to Figure 4. It reviews the important cautions noted in an earlier TCS discussion of the Arctic temperature record by George Taylor, who is a co-author of this article, on how linear trends need to be carefully estimated and weighted according to the time period considered.

Figure 4: The Arctic temperature anomaly record from 1880-2003 based on land temperature stations poleward of 70ºN from the Global Historical Climatology Network database constructed by George Taylor. Although there is significantly higher range in the interannual variability of this rendition of Arctic temperature, a cooling tendency in the 1934-2003 interval seems real.

These charts in Figure 4 show that if you measure temperatures from the 1970s, they appear to be rising; from 1934, they look to be falling; from 1880, when the world was beginning to come out of the Little Ice Age, they were again rising.

Note that the temperature charts in Figure 4 use only the land stations of the GHCN, as did the ACIA authors of Figure 1. But Taylor derived his data from that above 70ºN, rather than the more southerly 60ºN of Figure 1. Why? Because, as Taylor explained, "[u]sing 60ºN introduced a lot of ... questionable Siberian stations." The 1880-2003 curve in Figure 4 for this particular definition of Arctic shows a less dramatic recent warming trend when compared with those illustrated in Figure 1 or Figure 3 of ACIA suggesting the importance of geographical boundary.

Could some of the differences between the temperature trends found in the most recent decades arise because of different definitions of the Arctic?

To provide an answer, we go to one last visual aid, Figure 5. It summarizes the different views discussed here on geographical coverage for defining the Arctic, as well as the broader definition adopted by the Arctic Monitoring and Assessment Programme (AMAP) of the Arctic Council.

Note that by whatever definition nearly two-thirds of the Arctic is covered by the Arctic Ocean. It thus seems unreasonable to use only land-based stations, as the ACIA did, and not to include coastal stations, Russian drifting stations in the Arctic Ocean, and drifting buoys from the International Buoy Programme, as Polyakov and his colleagues did.

Figure 5: Different renditions of "Arctic" zones by different authors and institutions. However, It is clear that the Arctic temperature according to ACIA's chapter 2 probably included those "questionable Siberian stations" pointed out by George Taylor in Figure 4 while failing to include the important marine-based stations considered by Polyakov and colleagues in Figure 2.

The Arctic, as can be seen here, can be all over the map. Depending on one's definition and where one looks for data, the markedly different definitions can yield significant differences in Arctic warming trends. For example, the 70-90ºN definition illustrated by Arctic temperature in Figure 4 excluded a lot of the in-land stations in GHCN database that ACIA's definition of 60-90ºN included.

These different definitions need to be argued on their scientific merits.

Quoting from the minutes of the 8th ACIA steering committee meeting held in Ottawa, Canada on December 3-5, 2001: "[The authors of chapters 2 and 3] found the definition of the Arctic - currently the AMAP definition - is critical." [emphasis added].

Yet, the definition of Arctic in ACIA Overview Report's temperature curve in Figure 1 was not that of their intended AMAP definition around December 2001. If it had been, Figure 1 might have been closer to that based on the mostly marine-and-coastal-based stations selected by Polyakov and colleagues and are seen in the map in Figure 2.

Instead, the authors for ACIA's Chapter 2 explained in their paper for the November 2004's ACIA symposium that, "For this study, the focus has been on land surface stations for the Arctic, defined arbitrary as north of 60ºN." [emphasis added]

Perhaps a fuller explanation for ACIA's using this arbitrary definition for drawing its temperature curve in Figure 1, instead of AMAP definition in Figure 5, will appear in the scientific report due out in some months. For now, it is puzzling because ACIA is under the joint responsibility of AMAP and the Arctic Council's Conservation of Arctic Flora and Fauna.

The recent warming of the Arctic and its cause remains a matter of scientific speculation. The temperature trend found in the ACIA Overview Report (Figure 1) is high compared to other estimates. The warming trend over the 1980-2002 interval by ACIA's Chapter 2 authors shown in Figure 3, especially when compared to the warming occurred during 1920s and 1930s, is higher still. But these results hinge on scientific questions -- how is the Arctic defined, and which land- and marine-based temperature records should be included. There are large and dramatic changes observed[3] in the complex and highly variable Arctic atmosphere-ice-ocean system, but exaggerated presentations distract from the serious need for comprehensive scientific studies on what is really happening in the Arctic.

George H. Taylor is a faculty member at Oregon State University's College of Oceanic and Atmospheric Sciences. David Legates is Associate Professor in Climatology in the Center for Climatic Research at the University of Delaware. Sallie Baliunas recently served as part Deputy Director of Mount Wilson Observatory. Willie Soon is co-author of "The Maunder Minimum and the Variable Sun-Earth Connection".


[1] From ACIA's November 8's press release in the U.S.

[2] This difference was raised ( by Professor S. Fred Singer of The Science & Environmental Policy Project during the November 8's press briefing by ACIA in the National Press Club at Washington D.C. Researchers at the World Climate Alert also raised similar questions ( on ACIA's "Arctic" temperature curve.

[3] I. Polyakov et al., 2004, "Variability of the intermediate Atlantic water of the Arctic Ocean over the last 100 years", Journal of Climate, vol. 17 (December 1 issue), 4485-4497.


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