Regular readers may recall some of the posts here, here, here, and here, where the sea ice data presented by NSIDC and by Cryosphere today were brought into question. We finally have an end to this year’s arctic melt season, and our regular contributor on sea-ice, Steven Goddard, was able to ask Dr. Walt Meier, who operates the National Snow and Ice Data Center 10 questions, and they are presented here for you. I have had correspondence with Dr. Meier and found him straightforward and amiable. If only other scientists were so gracious with questions from the public. – Anthony
Questions from Steven Goddard:
Dr. Walt Meier from The US National Snow and Ice Data Center (NSIDC) has graciously agreed to answer 10 of my favorite Arctic questions. His much appreciated responses below are complete and unedited.
1. Many GISS stations north of 60 latitude show temperatures 70 years ago being nearly as warm as today. This pattern is seen from Coppermine, Canada (115W) all the way east to Dzardzan, Siberia (124E.) The 30 year satellite record seems to correspond to a period of warming, quite similar to a GISS reported period in the 1920s and 1930s. Is it possible that Arctic temperatures are cyclical rather than on a linear upwards trend?
No. Analysis of the temperatures does not support a cyclic explanation for the recent warming. The warming during the 1920s and 1930s was more regional in nature and focused on the Atlantic side of the Arctic (though there was warming in some other regions as well) and was most pronounced during winter. In contrast, the current warming is observed over almost the entire Arctic and is seen in all seasons. Another thing that is clear is that, the warming during the 1920s and 1930s was limited to the Arctic and lower latitude temperatures were not unusually warm. The recent warming in the Arctic, though amplified there, is part of a global trend where temperatures are rising in most regions of the earth. There are always natural variations in climate but the current warming in the Arctic is not explained by such variations.
2. The US Weather Bureau wrote a 1922 article describing drastic Arctic warming and ice loss. In that article, the author wrote that waters around Spitzbergen warmed 12C over just a few years and that ships were able to sail in open waters north of 81N. This agrees with the GISS record, which would seem to imply that the Arctic can and does experience significant warming unrelated to CO2. Do you believe that what we are seeing now is different from that event, and why?
Yes. The current warming is different from the conditions described in the article. The Weather Bureau article is specifically discussing the North Atlantic region around Spitsbergen, not the Arctic as a whole. The Arctic has historically shown regional variations in climate, with one region warmer than normal while another region was cooler, and then after a while flipping to the opposite conditions. As discussed above, the current warming is different in nature; it is pan-Arctic and is part of widespread warming over most of the earth.
3. A number of prominent papers, including one from Dr. James Hansen in 2003, describe the important role of man-made soot in Arctic melt and warming. Some have hypothesized that the majority of melt and warming is due to soot. How is this issue addressed by NSIDC?
NSIDC does not have any scientists who currently study the effect of soot on melt and warming. Soot, dust and other pollution can enhance melting by lower the albedo (reflectance of solar energy). However, it is not clear that soot has increased significantly in the Arctic. Russia is a major source of soot in the Arctic and Russian soot declined dramatically after the break-up of the former Soviet Union – just as sea ice decline was starting to accelerate. Furthermore, while soot on the snow/ice surface will enhance melt, soot and other aerosols in the atmosphere have a cooling effect that would slow melt. Thus, the effect of soot, while it may contribute in some way, cannot explain the dramatic rate of warming and melt seen in the Arctic seen over the past 30 years.
4. The NSIDC Sea Ice News and Analysis May 2008 report seems to have forecast more ice loss than has actually occurred, including forecasts of a possible “ice-free North Pole.” Please comment on this?
What NSIDC provided in its May report was “a simple estimate of the likelihood of breaking last year’s September record.” This gave an average estimate that was below 2007, but included a range that included a possibility of being above 2007. With the melt season in the Arctic ending for the year, the actual 2008 minimum is near the high end of this range. In its June report, NSIDC further commented on its minimum estimate by stating that much of the thin ice that usually melts in summer was much farther north than normal and thus would be less likely to melt.
In the May report, NSIDC also quoted a colleague, Sheldon Drobot at the University of Colorado, who used a more sophisticated forecast model to estimate a 59% chance of setting a new record low – far from a sure-thing. NSIDC also quoted colleague Ron Lindsey at the University of Washington, who used a physical model to estimate “a very low, but not extreme [i.e., not record-breaking], sea ice minimum.” He also made an important point, cautioning that “that sea ice conditions are now changing so rapidly that predictions based on relationships developed from the past 50 years of data may no longer apply.” Thus NSIDC’s report was a balanced assessment of the possibility of setting a new record, taking account of different methods and recognizing the uncertainty inherent any seasonal forecast, especially under conditions that had not been seen before.
For the first time in our records, the North Pole was covered by seasonal ice (i.e., ice that grew since the end of the previous summer). Since seasonal ice is thinner than multiyear ice (i.e., ice that has survived at least one melt season) and vulnerable to melting completely, there was a possibility that the ice edge could recede beyond the pole and leaving the pole completely ice-free. This would be fundamentally different from events in the past where a crack in the ice might temporarily expose some open water at the pole in the midst of surrounding ice. It would mean completely ice-free conditions at the geographic North Pole (just the pole, not the entire Arctic Ocean). The remarkable thing was not whether the North Pole would be ice-free or not; it was that this year, for the first time in a long time it was possible. This does not bode well for the long-term health of the sea ice
The fact that the initial analysis of potential minimum ice extent and an ice-free pole did not come to pass reflects a cooler and cloudier summer that wasn’t as conducive to ice loss as it might have been. There will always be natural variations, with cooler than normal conditions possible for a time. However, despite the lack of extreme conditions, the minimum extent in 2008 is the second lowest ever and very close to last year. Most importantly, the 2008 minimum reinforces the long-term declining trend that is not due to natural climate fluctuations.
5. The June 2008 NSIDC web site entry mentioned that it is difficult to melt first year ice at very high latitudes. Is it possible that there is a lower practical bound to ice extent, based on the very short melt season and low angle of the sun near the North Pole?
It is unlikely that there is a lower bound to sea ice extent. One of the things that helped save this year from setting a record was that the seasonal ice was so far north and did not melt as much as seasonal ice at lower latitudes would. The North Pole, being the location that last sees the sun rise and first sees the sun set, has the longest “polar night” and shortest “polar day.” Thus, it receives the least amount of solar radiation in the Arctic. So there is less energy and less time to melt ice at the pole. However there is a feedback where the more ice that is melted, the easier it is to melt still more ice. This is because the exposed ocean absorbs more heat than the ice and that heat can further melt the ice. Eventually, we will get to a state where there is enough heat absorbed during the summer, even at the shorter summer near the pole, to completely melt the sea ice. Climate models have also shown that under warmer conditions, the Arctic sea ice will completely melt during summer.
6. GISS records show most of Greenland cooler today than 70 years ago. Why should we be concerned?
We should be concerned because the warming in Greenland of 70 years ago was part of the regional warming in the North Atlantic region discussed in questions 1 and 2 above. Seventy years ago one might expect temperatures to eventually cool as the regional climate fluctuated from a warmer state to a cooler state. The current Greenland warming, while not yet quite matching the temperatures of 70 years ago, is part of a global warming signal that for the foreseeable future will continue to increase temperatures (with of course occasional short-term fluctuations), in Greenland and around the world. This will eventually, over the coming centuries, lead to significant melting of the Greenland ice sheet and sea level rise with accompanying impacts on coastal regions.
7. Antarctica seems to be gaining sea ice, and eastern Antarctica is apparently cooling. Ocean temperatures in most of the Southern Hemisphere don’t seem to be changing much. How does this fit in to models which predicted symmetric NH/SH warming (i.e. Hansen 1980)? Shouldn’t we expect to see broad warming of southern hemisphere waters?
No. Hansen’s model of 1980 is no longer relevant as climate models have improved considerably in the past 28 years. Current models show a delayed warming in the Antarctic region in agreement with observations. A delayed warming is expected from our understanding of the climate processes. Antarctic is a continent surrounded on all sides by an ocean. Strong ocean currents and winds swirl around the continent. These act as a barrier to heat coming down from lower latitudes. The winds and currents have strengthened in recent years, partly in response to the ozone hole. But while most of the Antarctic has cooled, the one part of Antarctica that does interact with the lower latitudes, the Antarctic Peninsula – the “thumb” of the continent that sticks up toward South America – is a region that has undergone some of the most dramatic warming over the past decades.
Likewise, Antarctic sea ice is also insulated from the warming because of the isolated nature of Antarctica and the strong circumpolar winds and currents. There are increasing trends in Antarctic sea ice extent, but they are fairly small and there is so much variability in the Antarctic sea ice from year to year that is difficult to ascribe any significance to the trends – they could simply be an artifact of natural variability. Even if the increasing trend is real, this is not unexpected in response to slightly cooler temperatures.
This is in stark contrast with the Arctic where there are strong decreasing trends that cannot be explained by natural variability. These decreasing Arctic trends are seen throughout every region in every season. Because much of the Arctic has been covered by multiyear ice that doesn’t melt during the summer, the downward trend in the summer and the loss of the multiyear ice has a particularly big impact on climate. In contrast, the Antarctic has very little multiyear sea ice and most of the ice cover melts away completely each summer. So the impact of any Antarctic sea ice trends on climate is less than in the Arctic. There is currently one clearly significant sea ice trend in the Antarctic; it is in the region bordering the Antarctic Peninsula, and it is a declining trend.
Because the changes in Antarctic sea ice are not yet significant in terms of climate change, they do not receive the same attention as the changes in the Arctic. It doesn’t mean that Antarctic sea ice is uninteresting, unimportant, or unworthy of scientific study. In fact, there is a lot of research being conducted on Antarctic sea ice and several scientific papers have been recently published on the topic.
8. In January, 2008 the Northern Hemisphere broke the record for the greatest snow extent ever recorded. What caused this?
The large amount of snow was due to weather and short-term climate fluctuations. Extreme weather events, even extreme cold and snow, will still happen in a warmer world. There is always natural variability. Weather extremes are always a part of climate and always will be. In fact, the latest IPCC report predicts more extreme weather due to global warming. It is important to remember that weather is not climate. The extreme January 2008 snowfall is not a significant factor in long-term climate change. One cold, snowy month does not make a climate trend and a cold January last year does not negate a decades-long pattern of warming. This is true of unusually warm events – one heat wave or one low sea ice year does not “prove” global warming. It is the 30-year significant downward trend in Arctic sea ice extent, which has accelerated in recent years, that is the important indicator of climate change.
9. Sea Surface Temperatures are running low near southern Alaska, and portions of Alaska are coming off one of their coldest summers on record. Will this affect ice during the coming winter?
It is possible that this year there could be an earlier freeze-up and more ice off of southern Alaska in the Bering Sea due to the colder temperatures. But again, this represents short-term variability and says nothing about long-term climate change. I would also note that in the Bering Sea winds often control the location of the ice edge more than temperature. Winds blowing from the north will push the ice edge southward and result in more ice cover. Winds blowing from the south will push the edge northward and result in less total ice.
10. As a result of being bombarded by disaster stories from the press and politicians, it often becomes difficult to filter out the serious science from organisations like NSIDC. In your own words, what does the public need to know about the Arctic and its future?
I agree that the media and politicians sometimes sensationalize stories on global warming. At NSIDC we stick to the science and report our near-real-time analyses as accurately as possible. Scientists at NSIDC, like the rest of the scientific community, publish our research results in peer-reviewed science journals.
There is no doubt that the Arctic is undergoing dramatic change. Sea ice is declining rapidly, Greenland is experience greater melt, snow is melting earlier, glaciers are receding, permafrost is thawing, flora and fauna are migrating northward. The traditional knowledge of native peoples, passed down through generations, is no longer valid. Coastal regions once protected by the sea ice cover are now being eroded by pounding surf from storms whipped up over the ice-free ocean. These dramatic changes are Arctic-wide and are a harbinger of what is to come in the rest of the world. Such wide-ranging change cannot be explained through natural processes. There is a clear human fingerprint, through greenhouse gas emissions, on the changing climate of the Arctic.
Changes in the Arctic will impact the rest of the world. Because the Arctic is largely ice-covered year-round, it acts as a “refrigerator” for the earth, keeping the Arctic and the rest of the earth cooler than it would be without ice. The contrast between the cold Arctic and the warmer lower latitudes plays an important role in the direction and strength of winds and currents. These in turn affect weather patterns. Removing summer sea ice in the Arctic will alter these patterns. How exactly they will change is still an unresolved question, but the impacts will be felt well beyond the Arctic.
The significant changes in the Arctic are key pieces of evidence for global warming, but the observations from Arctic are complemented by evidence from around the world. That evidence is reported in the Intergovernmental Panel on Climate Change and thousands of peer-reviewed scientific journal articles.
Let me close by putting Arctic change and climate science within the broader scientific framework. Skepticism is the hallmark of science. A good scientist is skeptical. A good scientist understands that no theory can be “proven”. Most theories develop slowly and all scientific theories are subject to rejection or modification in light of new evidence, including the theory of anthropogenic climate change. Since the first thoughts of a possible human influence on climate over a hundred years ago, more and more evidence has accumulated and the idea gradually gained credibility. So much evidence has now been gathered from multiple disciplines that there is a clear consensus among scientists that humans are significantly altering the climate. That consensus is based on hard evidence. And some of the most important pieces of evidence are coming from the Arctic.
Mr. Goddard, through his demonstrated skeptical and curious nature, clearly has the soul of a scientist. I thank him for his invitation to share my knowledge of sea ice and Arctic climate. I also thank Anthony Watts for publishing my responses. It is through such dialogue that the public will hopefully better understand the unequivocal evidence for anthropogenic global warming so that informed decisions can be made to address the impacts that are already being seen in the Arctic and that will soon be felt around the world. And thanks to Stephanie Renfrow and Ted Scambos at NSIDC, and Jim Overland at the NOAA Pacific Marine Environmental Laboratory for their helpful comments.
Thanks once again to Dr. Walt Meier from NSIDC. He has spent a lot of time answering these questions and many others, and has been extremely responsive and courteous throughout the process.