UPDATED 8 DECEMBER 2019 TO CORRECT AN AVERAGING ERROR

1. The original post below computes an warming rate for the “Rest of the World” (ROTW), not including the Arctic, as a simple arithmetic average. Here we show that if the average warming rate for the ROTW is computed as an area weighted average instead of a simple arithmetic average, the result is very different in that it validates the claim that the Arctic is warming twice as fast as the rest of the world.
2. In the charts displayed in Figure 1, Figure 2, and Figure 3 below, the ordinate identifies the twelve calendar months as numerals 1 to 12. The 13th value is the average of the first twelve and represents a mean annualized estimate. Warming rates are studied for five latitudinal regions as the North Polar Region (ARCT), Northern extent (NEXT), Tropics (TROP), Southern Extent (SEXT), and the South Polar Region (ANTA). The left frame displays the warming rates for each latitudinal region and the right frame graphically displays the ratio of the ARCT warming rate over the mean for the other regions.
3. In Figure 1 all four reference regions are used in the ROTW average. In Figure 2, the ROTW is redefined by excluding the South Polar Region (ANTA) as an outlier; and in Figure 3, the ROTW is further restricted by also excluding the Southern Hemisphere.
4. The results are summarized in Figure 4 where we find that the Arctic is indeed “warming twice as fast as the rest of the world” as claimed by climate science, by the media, and by Catherine McKenna. The original analysis that appears below the update came to the wrong conclusion that the removal of the South Polar region (ANTA) reduced the ratio to well below the “twice as fast” claim. The error in that analysis is that the ROTW average was not area weighted but a simple arithmetic average of warming rates. Since the ANTA region represents a relatively small region of the globe, the area weighted average for ROTW does not show a significant difference between including or not including the ANTA region (that does not show a statistically significant warming rate). With apologies to Catherine McKenna and others who had correctly claimed that the Arctic is warming twice as fast as the rest of the world.

UPDATE FIGURE 1: NO REGION EXCLUDED IN ROTW AVERAGE

UPDATE FIGURE 2: SOUTH POLAR REGION REMOVED FROM ROTW

UPDATE FIGURE 3: SOUTHERN HEMISPHERE REMOVED FROM ROTW

UPDATE FIGURE 4: SUMMARY TABLE

IS THE ARCTIC WARMING TWICE AS FAST AS THE REST OF THE WORLD? 

FIGURE 1: ARCTIC VS ROTW (INCLUDE ANTARCTIC)

FIGURE 2: ARCTIC VS ROTW (LEAVE OUT ANTARCTIC)

FIGURE 3: COMPARISON OF ZONAL WARMING RATES 

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1. THIS POST IS A CRITICAL EVALUATION OF THE CLAIM THAT THE ARCTIC IS WARMING TWICE AS FAST AS ANY OTHER PLACE ON EARTH AND THE CORRESPONDING CLAIM BY THE CANADIAN GOVERNMENT THAT CANADA IS LIKEWISE WARMING TWICE AS FAST ANY OTHER PLACE ON EARTH. BOTH OF THESE CLAIMS ARE OFTEN WORDED AS “WARMING TWICE AS FAST AS THE REST OF THE WORLD although the implication of the two claims are very different. Both of these claims are evaluated against zonal mean temperature data in this study.
2. The data used in the analysis are UAH satellite data for zonal mean temperatures for each calendar month for the South Polar, Southern Extent, Tropical, Northern Extent, and North Polar zones. The study period is constrained by data availability to 1979 to 2018, a span of 40 years. The full span warming rates computed with simple OLS linear regression are presented in Figure 1 and Figure 2 above in units of Celsius units per century.
3. Figure 1 is a comparison of all five zonal warming rates. The computed OLS full span warming rates for each of the twelve calendar month are shown in the top 6 rows labeled SPOL (South Polar Region), SEXT (Southern Extent),  TROP (Tropical zone), NEXT (Northern Extent), and NPOL (North Polar Region). The sixth row, marked ROTW (rest of the world) is the average warming rate for the four zones south of the North Polar Zone.
4. The NPOL zone is taken as a proxy for the Arctic and for Canada and it is compared with the ROTW as well as to the other four zones one at a time. Very high rates of warming are seen for the NPOL zone from 1.67C/century in November to 3.36C/century in April with an average of 2.27C/century. Low rates of warming but but with large differences among the calendar months are found in the SPOL (south polar region) where the warming rates for the calendar months range from cooling (-2.65C/century) in July to warming at 4.44C/century in November with an average warming rate of 0.81C/century. The ROTW (rest of the world outside of the NPOL) average ranges from 0.395C/century in July to 2.462C/century in November with an average of 1.43C/century. The month of November contains a number of extreme values.
5. A comparison of the warming rates in the top six rows of Figure 1 shows that the NPOL contains the highest average warming rate for all calendar months of 2.27C/century followed closely by NEXT at 2C/century, and well above ROTW at 1.64C/century. The next five rows of Figure 1 contain the ratio of the NPOL warming rate divided by the warming rate for the other four zones individually as well as the other four zones combined into the ROTW figures. Some negative values are seen in these ratios for the SPOL due to cooling in the South Polar region. Almost all of these ratios are greater than unity except for some low values of for the NEXT and SEXT zones.
6. The average ratio is seen in terms of the ROTW figures shown in bold in the bottom row of Figure 1. Here most ratios are greater than unity but with some low values in October and November that are more than offset by very high ratios April to July. The average of all calendar months is seen here as NPOL/ROTW = 1.96, a value very close to the claim that NPOL is warming twice as fast as the rest of the world. However the same analysis when carried out without SPOL (Figure 2), shows an averate ratio of NPOL/ROTW = 1.42. This result implies that the claim that NPOL is warming twice as fast as the rest of the world is an artifact of cooling in Antarctica. If Antarctica is removed from the comparison, we find that NPOL is warming about 42% faster than the rest of the world and not twice as fast.
7. The further claim often heard that NPOL is warming twice as fast as any other place on earth, is clearly not supported by the data presented above. The column of averages on the far right of Figure 1 shows the NPOL warming rate of 2.27C/century implies ratios of 1.1 to 1.6 when the SPOL is not included.
8. CONCLUSION: Comparison of zonal warming rates shows that the North Polar Region is warming faster than the rest of the world but the usual claim that it is warming twice as fast as the rest of the world is an artifact of cooling in the South Polar Region and is not found when that region is removed from the comparison. The further claim that the North Polar Region is warming twice as fast as any other place on earth is not supported by the data although the data do show that the North Polar Region is warming faster than the other four zonal regions studied in this analysis. A bibliography for this issue is presented below. Geological sources of heat in the Arctic that may have a role in this phenomenon are discussed in a related post on this site [LINK] .

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1. Johannessen, Ola M., et al. “Arctic climate change: observed and modelled temperature and sea-ice variability.” Tellus A: Dynamic meteorology and oceanography 56.4 (2004): 328-341.  Changes apparent in the arctic climate system in recent years require evaluation in a century-scale perspective in order to assess the Arctic’s response to increasing anthropogenic greenhouse-gas forcing. Here, a new set of centuryand multidecadal-scale observational data of surface air temperature (SAT) and sea ice is used in combination with ECHAM4 and HadCM3 coupled atmosphere’ice’ocean global model simulations in order to better determine and understand arctic climate variability. We show that two pronounced twentieth-century warming events, both amplified in the Arctic, were linked to sea-ice variability. SAT observations and model simulations indicate that the nature of the arctic warming in the last two decades is distinct from the early twentieth-century warm period. It is suggested strongly that the earlier warming was natural internal climate-system variability, whereas the recent SAT changes are a response to anthropogenic forcing. The area of arctic sea ice is furthermore observed to have decreased~8 · 10⁵ km² (7.4%) in the past quarter century, with record-low summer ice coverage in September 2002. A set of model predictions is used to quantify changes in the ice cover through the twenty-first century, with greater reductions expected in summer than winter. In summer, a predominantly sea-ice-free Arctic is predicted for the end of this century.
2. Otto-Bliesner, Bette L., et al. “Simulating Arctic climate warmth and icefield retreat in the last interglaciation.” science311.5768 (2006): 1751-1753.  In the future, Arctic warming and the melting of polar glaciers will be considerable, but the magnitude of both is uncertain. We used a global climate model, a dynamic ice sheet model, and paleoclimatic data to evaluate Northern Hemisphere high-latitude warming and its impact on Arctic icefields during the Last Interglaciation. Our simulated climate matches paleoclimatic observations of past warming, and the combination of physically based climate and ice-sheet modeling with ice-core constraints indicate that the Greenland Ice Sheet and other circum-Arctic ice fields likely contributed 2.2 to 3.4 meters of sea-level rise during the Last Interglaciation.
3. Serreze, Mark C., and Jennifer A. Francis. “The Arctic amplification debate.” Climatic change 76.3-4 (2006): 241-264.  Rises in surface air temperature (SAT) in response to increasing concentrations of greenhouse gases (GHGs) are expected to be amplified in northern high latitudes, with warming most pronounced over the Arctic Ocean owing to the loss of sea ice. Observations document recent warming, but an enhanced Arctic Ocean signal is not readily evident. This disparity, combined with varying model projections of SAT change, and large variability in observed SAT over the 20th century, may lead one to question the concept of Arctic amplification. Disparity is greatly reduced, however, if one compares observed trajectories to near-future simulations (2010–2029), rather than to the doubled-CO₂ or late 21st century conditions that are typically cited. These near-future simulations document a preconditioning phase of Arctic amplification, characterized by the initial retreat and thinning of sea ice, with imprints of low-frequency variability. Observations show these same basic features, but with SATs over the Arctic Ocean still largely constrained by the insulating effects of the ice cover and thermal inertia of the upper ocean. Given the general consistency with model projections, we are likely near the threshold when absorption of solar radiation during summer limits ice growth the following autumn and winter, initiating a feedback leading to a substantial increase in Arctic Ocean SATs.
4. Kaufman, Darrell S., et al. “Recent warming reverses long-term Arctic cooling.” Science 325.5945 (2009): 1236-1239.  The temperature history of the first millennium C.E. is sparsely documented, especially in the Arctic. We present a synthesis of decadally resolved proxy temperature records from poleward of 60°N covering the past 2000 years, which indicates that a pervasive cooling in progress 2000 years ago continued through the Middle Ages and into the Little Ice Age. A 2000-year transient climate simulation with the Community Climate System Model shows the same temperature sensitivity to changes in insolation as does our proxy reconstruction, supporting the inference that this long-term trend was caused by the steady orbitally driven reduction in summer insolation. The cooling trend was reversed during the 20th century, with four of the five warmest decades of our 2000-year-long reconstruction occurring between 1950 and 2000
5. Screen, James A., and Ian Simmonds. “Increasing fall‐winter energy loss from the Arctic Ocean and its role in Arctic temperature amplification.” Geophysical Research Letters37.16 (2010).  Arctic surface temperatures have risen faster than the global average in recent decades, in part due to positive feedbacks associated with the rapidly diminishing sea ice cover. Counter‐intuitively, the Arctic warming has been strongest in late fall and early winter whilst sea ice reductions and the direct ice‐albedo feedback have been greatest in summer and early fall. To reconcile this, previous studies have hypothesized that fall/winter Arctic warming has been enhanced by increased oceanic heat loss but have not presented quantitative evidence. Here we show increases in heat transfer from the Arctic Ocean to the overlying atmosphere during October–January, 1989–2009. The trends in surface air temperature, sea ice concentration and the surface heat fluxes display remarkable spatial correspondence. The increased oceanic heat loss is likely a combination of the direct response to fall/winter sea ice loss, and the indirect response to summer sea ice loss and increased summer ocean heating.
6. Semenov, Vladimir A. “Meteorology: Arctic warming favours extremes.” Nature Climate Change 2.5 (2012): 315.  The twenty-first century was marked by a number of extreme weather events over northern continents. Amplified warming in the Arctic region and associated changes in atmospheric dynamics may provide a clue for understanding the origin of these recent extremes.
7. Pithan, Felix, and Thorsten Mauritsen. “Arctic amplification dominated by temperature feedbacks in contemporary climate models.” Nature Geoscience 7.3 (2014): 181.  Climate change is amplified in the Arctic region. Arctic amplification has been found in past warm¹ and glacial² periods, as well as in historical observations^3,4 and climate model experiments^5,6. Feedback effects associated with temperature, water vapour and clouds have been suggested to contribute to amplified warming in the Arctic, but the surface albedo feedback—the increase in surface absorption of solar radiation when snow and ice retreat—is often cited as the main contributor^7,8,9,10. However, Arctic amplification is also found in models without changes in snow and ice cover^11,12. Here we analyse climate model simulations from the Coupled Model Intercomparison Project Phase 5 archive to quantify the contributions of the various feedbacks. We find that in the simulations, the largest contribution to Arctic amplification comes from a temperature feedbacks: as the surface warms, more energy is radiated back to space in low latitudes, compared with the Arctic. This effect can be attributed to both the different vertical structure of the warming in high and low latitudes, and a smaller increase in emitted blackbody radiation per unit warming at colder temperatures. We find that the surface albedo feedback is the second main contributor to Arctic amplification and that other contributions are substantially smaller or even opposeArctic amplification.
8. Cohen, Judah, et al. “Recent Arctic amplification and extreme mid-latitude weather.” Nature geoscience 7.9 (2014): 627.  The Arctic region has warmed more than twice as fast as the global average — a phenomenon known as Arctic amplification. The rapid Arctic warming has contributed to dramatic melting of Arctic sea ice and spring snow cover, at a pace greater than that simulated by climate models. These profound changes to the Arctic system have coincided with a period of ostensibly more frequent extreme weather events across the Northern Hemisphere mid-latitudes, including severe winters. The possibility of a link between Arctic change and mid-latitude weather has spurred research activities that reveal three potential dynamical pathways linking Arctic amplification to mid-latitude weather: changes in storm tracks, the jet stream, and planetary waves and their associated energy propagation. Through changes in these key atmospheric features, it is possible, in principle, for sea ice and snow cover to jointly influence mid-latitude weather. However, because of incomplete knowledge of how high-latitude climate change influences these phenomena, combined with sparse and short data records, and imperfect models, large uncertainties regarding the magnitude of such an influence remain. We conclude that improved process understanding, sustained and additional Arctic observations, and better coordinated modelling studies will be needed to advance our understanding of the influences on mid-latitude weather and extreme events.
9. Gramling, Carolyn. “Arctic impact.” (2015): 818-821.  Against the backdrop of “Snowmageddon” and other powerful winter storms that have blasted the United States, Europe, and Asia in the past few years, a different kind of tempest has been swirling within the Arctic science community. Its core is a flurry of recent research proposing that such extreme weather events in the midlatitudes are linked through the atmosphere with the effects of rapid climate change in the Arctic, such as dwindling sea ice. The idea has galvanized the public and even caught the attention of the White House. But some Arctic researchers say the data don’t support it—or that the jury is at least still out. Now, scientists are tackling the issue in earnest, and an increasing number of conferences and workshops are bringing together scientists with a range of viewpoints on this issue, in hopes that a coordinated effort will measure the reach of the north.