Q & A: Global Warming

There was an interesting piece that appeared in the October 12 edition of the Seattle Times, “Q&A: Global warming — a world of evidence”. This follows up on a previous article by journalist Sandi Doughton in the October 9 issue of the Times, “The Truth About Global Warming”.

In the Q&A, a group of University of Washington scientists, including atmospheric scientist and climate researcher J. Mike Wallace, weigh in with answers to questions fielded from the paper’s readers. Many of the questions, such as “Isn’t it true that scientists in the 1970s said the earth was cooling?” are quite similar to those we’ve addressed here at RealClimate (see “The Global Cooling Myth”).

Wallace’s perspectives are particularly interesting because he is both a highly respected climate researcher (and National Academy of Sciences member) and, like a number of other long-time researchers in the field, was once a “skeptic” (in the best sense of the word) regarding the evidence for anthropogenic climate change. However, like many other such researchers, he has become convinced by the compelling weight of evidence indicating human influence on climate that has unfolded over the past decade, remarking that “with each passing year the evidence has gotten stronger — and is getting stronger still.

120 comments on this post.
  1. Tapasananda:

    it dont take a weatherman to see which way the wind blows

  2. David Donovan:

    Does anyone care to comment on the following Fox new opinion piece

    What Arctic Warming?
    Thursday, October 13, 2005
    By Steven Milloy

    In particular, is he being overly selective in his use of the data he has looked at > And what happend to sea ice cover say between the 20’s and 40’s ?

    Thanks Dave

    [Response: Hi Dave, we responded to an earlier, similar piece by Milloy here. -stefan]

  3. Bjorn van der Meer:

    Hello Realclimaters…can you give a brief statement on the importance or non-importance of Hurricane Vince?



    I would just be interested in an interpretation of that.

    Regards, B.

    [Response:The essential answer to this question is that one event doesn’t tell us much. This event simply adds to the statistics. So while it may provide a dramatic example of the apparent trend in hurricane intensity and/or frequency, it neither defines nor demonstrates that trend.–eric]

  4. Lynn Vincentnathan:

    RE #2, I have the faith that one day science will be able to tell us about each event, such as strange hurricanes, whether AGW played a role, and perhaps by how much. Unfortunately, by that time it will probably be too late to reverse GW, if it isn’t already too late — problem is, scientists can’t really tell us about that one way or the other, either.

    I’m sure it’s more than a 5% probability that AGW contributed to a hurricane (Vince) cropping up in a strange place. I figure since scientists don’t like to make claims unless there is less than a 5% chance they are wrong, we non-scientists can start reducing GHGs when there is a 5% or greater possibility we are causing harm.

    The way I look at it is by my reductions of GHGs, I’m helping in my tiny way to reduce that GW induced 50% extra intensity that Emmanuel found for the entire data set. Which hurricanes we will reduce in intensity by our GHG reductions, we don’t know, but since we care for all people, it doesn’t matter which ones we help reduce, as long as we keep helping to reduce them.


    I just read about another possible AGW positive feedback at:


    Seems warming may be increasing the “ozone hole,” which lets in more UV radiation, which increases the warming, increasing the hole, increasing the warming…..

  5. CharlieT:

    I assume that Fred Singer’s question is a non-question, but what is the answer ?

    [Response: Good assumption. The mixed layer of the ocean is mixed (pretty much by definition) thus the net fluxes at the surface (latent heat, sensible heat, long wave up and down, short wave down) warm or cool the whole layer. Diffusion/entrainment of the anomalous mixed layer temperature then allows the perturbation to diffuse into the deep ocean. There are some interesting details related to how the changes in the net fluxes affect the mixing, but since that is mostly done by the wind, it can be neglected in the first instance (although models do take this into account). Singer appears to think that long wave fluxes only affect the skin temperature and then somehow vanish. He is unfortunately confused. -gavin]

  6. Eli Rabett:

    Lynn, the usual answer is that while increasing greenhouse gas concentrations produce warming in the troposphere they also produce cooling in the stratosphere. Ozone hole production requires temperatures below ~197K. The rest is a very long story.

    There is another interesting issue. HOx can destroy ozone via catalytic processes. The normal stratosphere is water free, however increased emissions of methane lead to production of more water vapor, and eventually HOx in the stratosphre. Also warming of the tropopause (see global warming) allows more water vapor to leak through.

    More than you want to know at the Stratospheric Ozone Textbook http://www.ccpo.odu.edu/SEES/ozone/oz_class.htm and in Robert Parson’s FAQ at Bob Grumbines FAQ site http://www.radix.net/~bobg/

  7. PHEaston:

    In reply to a question about how did the Vikings grow wine in Norway (during the Medieval Warm Period (MWP)), Wallace says: “It’s possible that the Vikings were making wine from Concord-like grapes, which can grow in relatively cold climates.” That explains it then, no MWP. My understanding is there is a historians’ concensus that when the Vikings were at the height of their power, the regions they inhabited were warmer than they are now – including Scandinavia, Greenland and Labrador (ie. at least part of the North American mainland). I suspect its been discussed before on this site, but what are the key arguments for and against a MWP and whether it was a ‘local’ or global phenomenon?

    [Response: The topic has already been discussed in some detail on the site. The best place to start is our glossary entry on the “Medieval Warm Period” (due to a glitch we are in the process of trying to fix, most of our glossary items are currently not showing up in the “Glossary” page link). A site search on “Medieval Warm Period” yields many other instances of discussion of the topic on the site. -mike]

  8. Stephen Berg:

    Three more news stories on Climate Change:

    “Tropics Play More Active Role Than Was Thought In Controlling Earth’s Climate”:


    “Link Between Tropical Warming And Greenhouse Gases Stronger Than Ever, Say Scientists”:


    “Warmer Seas, Wetter Air Make Harder Rains”:


  9. Tom Rees:

    Re #7: Just what evidence is there that vines for wine were grown in Norway. anyway? Every time I hear this canard it gets futher North. First it was vines in York, then vines in Scotland, and now vines in Norway. It’ll be vines in the Arctic Circle next!

    But I’ve yet to see any evidence for these claims. The strongest evidence I know of is that grapes were grown in southern england, because these vinyards are listed in the Domesday book.

    You also have to remember that the economic pressures were different from what they are today. Wine was required for liturgical reasons, and the import/export trade was not too developed in the early millenium.

  10. Harald Korneliussen:

    You can grow grapes in Norway, if you are pleasantly situated (Hardanger, or perhaps places like Valldal or Glomset to name a few places close to me). However, the growth season is short and you run a high risk of losing the crop to bad weather. So Tom is right: it’s economically unfeasible today, but sacramental wine was very important in the middle ages.
    (I seem to recall that further north, like northen norway, iceland, greenland, where grapes just won’t grow, they had a papal permission to use something else than wine. I might be wrong.)

  11. Ferdinand Engelbeen:

    Tom, re #9

    There are some reports that there were (small) medieval vineyards in Scotland, probably restricted around cloisters for liturgical purposes. But the border where commercial vineyards were grown has been some 200 km more north than until a few decades ago, both in the Roman times as during the MWP. Now the climate is somewhere back to where commercial wine making was possible during the MWP and some former vineyards are reestablished on the sites which were abandoned during the LIA. See: “Winelands of Britain” and the map of the lecture & workshop.

    The same is true for vineyards in Belgium, which were abandoned during the LIA, the border – except in shielded valleys – was some 300 km more south, but slowly coming back now… Thus it seems that we are reaching again MWP temperatures in Europe, not more than that…

    [Response: Deducing temperature from commerical vineyards is fraught with problems. Transporting wine large distances is now very easy; during the MWP/LIA/past is was hard. So the incentive to grow grapes locally was much much stronger – William]

  12. Jeffrey Davis:

    My parents in the 1950s would buy a bottle of NY wine around Christmas. (Mmmm. Sugary concord wine.) So, I presume that there had been vinyards there for years before that. New York has a much colder climate than Britain.

  13. Sashka:

    To the North of New York City, there is Brotherhood winery. Quoting from http://www.hudsonriver.com/winetour.htm

    Brotherhood is America’s oldest continuously operating winery. It even stayed in business during Prohibition by producing government-sanctioned altar and medicinal wines. The winery’s John Jaques Building, named after Brotherhood’s founder, provides entry to the winery’s network of old subterranean caves, where wines are aged in a variety of oak vessels, some dating back to the 1840s. … Brotherhood produces an array of wines, from basic table wines like Chablis, Blush Chablis and Burgundy, to fortified wines, dessert wines and premium varietal wines, like chardonnay, Riesling, Cabernet Sauvignon and Pinot Noir.

  14. Lynn Vincentnathan:

    We had neighbors that grew grapes in Wisconsin, where the weather would usually dip well below 0 F in mid-winter (at least that’s what it was like 30 years ago when we lived there – can’t vouch for now). However, they only made grape juice, being tea-totalers. I think Wisconsin is quite a bit colder than N. Europe or Northern NY. You go far enough north & you start getting that mid-night sun effect – great for grape-growing.

    So, what’s the point? Maybe grapevines would even grow in the Arctic circle, at least after we really start warming?

    The latest contrarian argument: We all grow grapes, drink wine, get drunk, and become oblivious to GW,…or at least make sacramental wine, go to Mass, & repent of our GHG sins, before we reach that really hot place.

  15. dan allan:

    Well, not to sound too catty, but I have to admit, I got a kick out of two suggestions of AGW causes in the questions in the Q & A in the Seattle times: (1) the effects of heat from cigarette smoke, and (2) the effect of human body heat!

    Do you mean to say you guys haven’t included these important “forcings” in your models? In that case, you can count me as a skeptic! ;)

    Also, what about the WV effect of increased Chai consumption?

  16. Steve Latham:


    I followed the link in your response to #2 regarding Milloy. There is an interesting statement including Greenland in one of the first sentences:

    “The study describes the ongoing climate change in the Arctic and its consequences: rising temperatures, loss of sea ice, unprecedented melting of the Greenland ice sheet, and many impacts on ecosystems, animals and people.”

    I have read several times in posts from skeptics that Greenland is actually cooling. What is the best way to check such statements? Is there more recent summary info for Greenland?

  17. Eli Rabett:

    Most of the wines in New York were grown in the Finger Lakes Region, which has a rather nicer microclimate. OTOH, they still had to be rather hearty varieties.

  18. Blair Dowden:

    Re #16, I too would like to see a comprehensive summary of Greenland climate and ice thickness data. From what I see from the Global Historical Climatology Network (GHCN) of land temperatures and the Comprehensive Ocean-Atmosphere Data Set (COADS) of SST data, temperatures there were higher around the 1930’s than now, and there is not much long term warming trend, except for the past few years. I also understand that ice is melting near the coast, but thickening in the interior. It is not clear what conclusions can be drawn from this.

  19. Stephen Berg:

    Regarding the winery industry, Ontario has a wine industry with reds, whites, and is one of the world’s largest producers of ice wines.

    One risk is that climate change will warm Southern Ontario enough to cripple this lucrative ice wine industry, since a week of -7 C and lower is required to harvest these grapes. The resulting climatic variability will make it difficult for the temperature to remain somewhat steady – and not to get too cold as to reduce grape growth.

  20. Steve Bloom:

    Re #16 (Steve Latham):

    Fresh Greenland info at http://cires.colorado.edu/science/groups/steffen/greenland/melt2005/ . Apparently the high-altitude center is still cold enough to not be actively melting, but the overall rate is going up fast (which is probably more what we’re concerned with than average temperature). In any case, http://www.agu.org/pubs/crossref/2005/2005GL023552.shtml seems to make it fairly clear that things are getting toasty in Greenland; there’s a related story at http://www.lanl.gov/news/newsletter/092605.pdf . See also http://europa.eu.int/comm/research/rtdinfo/special_pol/04/article_2600_en.html for a more direct discussion of overall temperature.

    Then we have this fascinating skeptic article from Reason magazine: http://www.reason.com/rb/rb111004.shtml . Possibly this article is Milloy’s source, and what’s especially interesting about it is how very wrong so many skeptics (including Richard Lindzen and John Christy) can turn out be in just eleven months. Among other things, the author makes a big point that a paper from March 2004 by Chylek et al showed a cooling of Greenland, and that this study had somehow been censored from the Arctic Climate Impact Assessment. Notice that the first study I linked to above is a brand-new one by the self-same Chylek team, now finding that there is indeed rapid warming. With just an eighteen month interval between the two studies, this appears to be some sort of climb-down.

  21. Steve Bloom:

    Re #s 16 and 18: From the prior RC post, there’s also this extensive discussion of Arctic temperature, including Greenland: http://www.nersc.no/AICSEX/rep218.pdf . Also, I notice in Milloy’s article that his “expert source” was George Taylor, a “certified consulting meteorologist” and confirmed skeptic who has little expertise on climate and none on the Arctic. Now that’s scraping the bottom of the proverbial barrel.

  22. Ferdinand Engelbeen:

    Re #18,

    I have made a graph of all weather station trends of Greenland. Indeed, the temperatures in the 1930-1940 period were higher than thereafter and only in the last decade temperatures increased to near equal of that period again. The same is true for ice melting: All glaciers of Greenland are receding, but the breakup point of the largest tidal glacier (near Illulisat) moved faster inland in the 1930-1940 period than today.

  23. Ferdinand Engelbeen:

    Re #11 comment:


    The graph made by Prof. Selley is based on historical vineyards at one side and the climatological/geological possibilities today. In Roman times, grapes were grown where possible, as economics didn’t play a role. In the Medieval period, I suppose that economics were not a big item either. While the Romans did occupy Engeland up to the Scottish border (Hadrian’s wall…), the border for grape growing remained in south England.

    According to Selley, climate today is about the same as in the Medieval period to grow grapes (no matter the commercial side), but the border may shift more north, if the projections of increased temperature become true.

  24. Tom Rees:

    Re#16 Greenland temps. The problem is that the North Atlantic Oscillation has big effect in Greenland – the current positive phase is bringing cool to Southern Greenland and warmth to Northern Europe. Apparently, after taking into account the effects of the NAO, there’s a substantial underlying warming trend. See Scientist calculates Greenland warming

  25. Stephen Berg:

    Re: #20,

    The “Reason” article’s title is very a propos, in that there are “two sides to global warming.” However, unlike what they believe, there is the side which is correct and the side which is incorrect.

  26. Jeffrey Davis:

    The tangent about vines really seems to indicate that there are a lot of people who believe “in vino veritas”.

  27. Kok, Wim (Netherlands, Europe):

    This is only a short comment regarding research on global warming using information of wine production, vineyards and grape types.

    Indeed this is fraught with problems, not in the least because there are few plant species on earth like vitis vinifera which show so many varieties. Many historic vine species are yet fully unknown or, at best, only suspected to be of the variety X. Information is sparse. Moreover, the conditions under which these ancient varieties flourished are only very partially known. It seems to me almost impossible to deduct climatic trends from the study of vines only.

    A better and more widely known method is pollen-research. Changes in the composition of pollen contents (revealing many species and ecosystems) during the ages (geological record) may show more subtle variances in climatic conditions.

  28. Tom Fiddaman:

    Re “in vino veritas”

    Grape ripening as a past climate indicator

    Nature, Vol. 432, 18 November 2004.

    French records of grape-harvest dates in Burgundy were used to reconstruct spring-summer temperatures from 1370 to 2003 using a process-based phenology model developed for the Pinot Noir grape. Our results reveal that temperatures as high as those reached in the 1990s have occurred several times in Burgundy since 1370. However, the summer of 2003 appears to have been extraordinary, with temperatures that were probably higher than in any other year since 1370.

    Lots of other proxies at the WDC paleo mirror site.

  29. Gerald Machnee:

    The following is part of an article that was printed last year —
    {Vintage Wine Records Trace Climate Change to 1300s
    John Roach
    for National Geographic News
    November 17, 2004

    Connoisseurs may pore over grape-harvest records in search of the perfect vintage of wine. But a team of French scientists and historians is toasting the same records for the insights they yield on past climate.

    In Burgundy, France, as in other parts of Europe, the first officially decreed day of grape harvesting has been carefully noted in parish and municipal archives for at least 600 years.

    Using a scientific method known as phenology�in which the onset of various stages of plant growth are correlated with climate�the team was able to reconstruct spring and summer temperatures in Burgundy from 1370 to 2003. The findings are based on the harvest dates of pinot noir grapes. }

  30. wayne davidson:

    #16 #20 #24, Ask a Greenlander like I did, and get this as an answer: From Qanaq, situated North of Thule Air Force Base, with a sizable population of people still making tradionnal Kayaks, Boating season
    use to be Augsust-September, now it is June-December, shore sea ice after the long night is 50% thinner,
    temperatures have been unusually warmer for the last 5 to 10 years. There is no debate up here, it is substantially warmer. Basic Meteorology, Climatology must include data from populated areas.
    Imagine Northerners debating summer of 2005 cooling of NY city , without even talking to one single New Yorker, or taking data from a reliable New Yorker, how silly that sounds….

  31. Ferdinand Engelbeen:

    Re #20 (and others):

    All the graphs of Greenland ice melting start in 1979, in a notable cooler period than 1930-1940. If we may assume that the moving speed of a breaking up point of a glacier is a good indication for past temperatures, then have a look at the retreat of the largest Greenland glacier at Illulisat, West Greenland. If you look at it in detail, you can see that the retreat in the period 1929-1953 (24 years) was faster than in 1953-2003 (50 years).
    Thus all together, the retreat is the result of global warming at least since 1850, and the retreat was faster around 1930-1940 than today, when GHGs were not playing any important role.

    Chylek found a good correlation between one (1) Greenland station (Danmarkshavn) and global warming, according to him, without an influence of the NAO. But this is the only (!) station which starts measuring temperatures after 1950, again in a cooler period. The other station at the same latitude (~77N), Thule at the west coast, started measuring in 1947, with a higher temperature and a sudden cooling thereafter, comparable to the temperature drop of most other Greenland stations. And Thule parallels the Danmarkshaven temperature data until 1972, when it ceased operation. This indicates that the Danmarkshavn temperatures were not unique in trend, but that the data collection started after the warm period.

    There is a small sudden shift in NAO index around 1946 to positive, which may be the cause of the Greenland cooling, but in general temperatures were as high (or higher) than today in the 1930-1940 period, be it with an average neutral NAO. In recent years the average NAO index seems to go down to neutral too (which – in part – can explain the recent warming). But my impression is that there is not much correlation between the NAO and temperature in Greenland (the coldest temperatures are in a strong negative NAO period).

    Thus I am still waiting for a good explanation where the Greenland melting is linked to greenhouse gases…

  32. Gerald Machnee:

    We may note from history that central North America, especially Canada, was covered by a glacier. Eventually Lake Agassiz formed in Manitoba extending into USA, then the lake mostly disappeared.
    Likely there were not too many alarmed over the glacier’s retreat.

  33. Stephen Berg:

    Re: #32, “We may note from history that central North America, especially Canada, was covered by a glacier. Eventually Lake Agassiz formed in Manitoba extending into USA, then the lake mostly disappeared.
    Likely there were not too many alarmed over the glacier’s retreat.”

    Well, of course! There were very few people in the region at that time, and those few who were there were glad to be able to hunt and gather food in the region they once called home prior to the onset of the ice age.

    What were you trying to say here, Gerald?

  34. Gerald Machnee:

    RE #32 – What I was noting was that glaciers have come and gone. We are getting alarmed over retreating glaciers ( and some may be increasing). I feel we should be concerned with decreasing pollution emmission as well as being prepared for changes in climate(which would include extreme weather), both financially and with supplies, both of which were missing in Katrina.

  35. Lynn Vincentnathan:

    What this regional cooling data in more current times indicates to me is that it must be getting really hot in other places (& not all places are warming in lock-step), or we wouldn’t be having this increase in the AVERAGE of global temps.

    What the regional hotspots in the distant past indicate to me, is that there are other factors, aside from AGW, that can warm up places, which means we have to really get on with reducing GHGs. We wouldn’t want situations where AGW AND these other warming processes piggy-back or coincide, & really cause a lot of harm.

    Any other arguments? — I have answers.

    How about “in the past the GHG increase FOLLOWED the GW.” Well, that’s scary. It means we may be headed for some really nasty runaway GW, if we don’t drastically reduce our GHGs ASAP….because, of course, the fact that warming causes GHG emissions does not in any way at all disprove the well accepted fact that GHGs cause warming.

  36. Randolph Fritz:

    Since this seems to have turned into an open Q&A thread, I’d like to ask if there’s any opinions on the effects of global climate change on winter storms in the North American Pacific Northwest?

  37. James Annan:


    Ah, that’s the famous “Reason” article which says:

    Richard Lindzen says he’s willing to take bets that global average temperatures in 20 years will in fact be lower than they are now.

    Of course, it later became clear that he really meant he would accept such a bet if offered 50:1 odds in his favour, which doesn’t sound quite so dramatic :-) I predict that very little of that article will stand the test of time. But it is only fair to acknowledge that Ronald Bailey now openly accepts that warming is real and ongoing (“We’re all global warmers now”)

  38. wayne davidson:

    The point of many detractor contrairians fail to make, is reality in the field, from Iceland to Alaska, they always fail to bring out science field experts with accurate information, including the greatest ones, the hunters, we have them still, and they are extremely keen on the weather. Icelanders to Alaskans will state that there is unusual warming beyond the memories of their ancient cultures, but they are very seldom mentioned. Strange that some contrarians allege the Arctic Climate Impact Assessment was witheld some vital cooling information, just once, when they fail all the time to quote the real action from the ground or ice all the time.

    That is what is needed though, some break from the silence, for Northerners to write down what is going on, or for doubtful Southerners to contact them just as long as their doubts exists, climatologists mentioned above sum up very well what is going on, unfortunately they are often disavowed by the media, paralysed by formented confusion illusions, from the North it looks like the truth competing in a game of musical chairs.

    The whole contrarian stance is quite ridiculous though, defending the Carbon based pollution industry is ironically flawed, there is a lot more hysterical economy collapse fear mongering claims than environmentalists decrying the end of the world. But oil barons should not be afraid of an hydrogen based energy industry…….. There is a lot of H’s in one molecule of Crude Oil.

  39. Ferdinand Engelbeen:

    Re #38,

    As an interested outsider, I have looked at the temperature trends of all circumpolar stations. Alaska and East Siberia (30% of all stations) today have higher temperatures than in the 1930-1940 period. The rest of the stations (70%) don’t or just reach the temperatures of the previous warm period. But that was done a few years ago, may need some update.

    So you are right that current temperatures in Alaska are higher than in the past hundreds of years, be it that the warming started with a sudden shift of the PDO in 1976. But that is not true for Greenland and other places around the North Pole. Thus if one should ask the Inuit near Thule if there was less ice and longer summers in 1930-1940, the answer should be yes (as far as the human memory is reliable)…

    This brings us to the point that climate programs predict a two times faster warming at the poles than in the rest of the world. This is clearly not true, if you look at the Arctic as a whole over the past century, because the previous warming towards the ’30s was faster and higher than the recent one, while CO2 still was low. In my opinion, what Chylek has done is cherry picking one station of Greenland with a (too) short data series, to prove that the GCM’s are right. This is not scientific and together with the horror stories about Greenland ice melting, this will backlash on the credibility of climate science.

    That doesn’t mean that we shouldn’t reduce our dependence on fossil fuels as soon as possible, be it more for geopolitical reasons and pollution reduction than for fear for a runaway warming…

  40. Max Haberrecker:

    In a discussion about global warming, someone made the following statement:

    1.) There has never been a global warming model that has taken into account the leading contributor to global warming. The sun.

    2.) Fact: Just one volcano can emit more greenhouse gases than all of humanity in its entire existance. It has happened before, four or five times in human history alone. Yet, mother nature takes care of it. To think that mother nature cannot take care of that amount of gas, spread out over decades of time, is ridiculous.

    Can I have some comments or clarifications on this? Some links would be great too.

    Thanks in advance!

    [Response: Whoever made those comments has very little knowledge about the topic. I suggest you check out the “Climate Modeling” RC category link. There you will find numerous past postings dealing with the topic. The article on “Planetary Energy Balance” would in paticular be a good place to start. With regard to the source of modern increases in Co2 and other greenhouse gaes, few if any credible scientists would question that this is anthropogenic in origin. See this previous RC article on the topic. Volcanic outgassing is an important source of greenhouse gas concentrations on geological timescales, where the atmospheric concentrations are determined by a balance between outgassing from the solid earth and uptake of co2 from the atmospheric due to natural processes such as chemical and physical weathering, which are important on timescales of millions of years. Changes in this balance over time lead to the changes in greenhouse gas concentrations that have been observed to occur on geological (millions of year) timescales. These factors are important in understanding past warm geological periods (such as the early Cretaceous) when co2 levels are believed to have been several times greater than today. These processes are not believed to play any significant role on the timescales (centuries to millennia) of interest in discussions of anthropogenic climate forcing and climate change. -mike]

  41. Robert Simmon:

    re: #31

    The extent of tidal glaciers (like the Ilulissat Glacier) is not determined solely, or even primarily, by temperature. Interaction between the glacial terminus and the ocean (such as wave action and sea level), as well as the bathymetery of the sea floor govern the calving rate of the glacier, which determine the extent along with snow accumulation rate, flow rate, and melt rate (temperature). In general, tidal glaciers are cyclical, advancing over 1,000 years or so and then rapidly retreating for one or two centuries. To use the Ilulissat Glacier as evidence of a temperature trend (warming, cooling, or neither) is unwarranted

    Alpine Glaciers, on the other hand, can be good indicators of climate change, including temperature. Read: At the Edge: Monitoring Glaciers to Watch Global Change.

  42. Tom Fiddaman:

    Re #40

    I haven’t seen any recent estimates of volcanic emissions, but:

    Present-day carbon dioxide (CO2) emissions from subaerial and submarine volcanoes are uncertain at the present time. Gerlach (1991) estimated a total global release of 3-4 x 10E12 mol/yr from volcanoes. This is a conservative estimate. Man-made (anthropogenic) CO2 emissions overwhelm this estimate by at least 150 times.

    Even if Gerlach is wrong by two orders of magnitude, point 2) is baloney.

  43. wayne davidson:

    #39, We stand by what we are saying, it is warmer UP here in the High Arctic. That warming record of the
    40’s, had very little memorable impact compared to now. Resolute Bay was suppose to be built on Melville Island, but in 1947 there was so much old multi-year ice it was impossible to move ships a further 400 miles West or so. Today, there is nothing but open water over Barrow Strait with only new fast ice sheets in the Bay’s, there is no debate over which period was warmer. The weather is changing so much that elder hunters throughout Northern Canada can’t recognize some (warm) clouds, and the dominant winds have become unfamiliar, ice hunting seasons have shortened, in the old days that would have meant starvation, not only for Polar Bears. The fact that one study singled out one weather station pales in comparison to what is really happening. Any fixation about climate change should start first with a thorough synopsis of what is going on a wider geographical scale, it seems that this is not done, rather hand picked specific locations are too much analyzed instead of studying the whole picture. This leads to endless debates about how good one location is to study over another, it is after all Global Warming we are debating. Climatologists do just that, they include everything and they should be heard more often.

  44. Lynn Vincentnathan:

    Since we’re on Q&As, an engineer brought up a point about ice melting in a glass of water (in an attempt to shed light on glacier melt, etc). He said the glass of water stayed cold as long as there was ice, but heated to room temp pretty rapidly after the ice melted. Would this have any implications for Earth & GW?

    He also mentioned (I think) that the process of melting required a lot of energy (or gave off energy)?? – would this have any significance….

  45. Steve Bloom:

    Re #39 (FE): And here’s the aforementioned Greenland melting horror story: http://cires.colorado.edu/science/groups/steffen/greenland/melt2005/ . Yep, pretty horrible. Now Ferdinand can explain how this data is fraudulent (a little tough to do since the author is the leading scientist in the field) or how the record melting is really beside the point since we can be confident that Greenland isn’t warming anyway.

    Ferdinand, any large-scale climate trend is going to be uneven in the sense that there will always be local indicators that don’t follow the trend exactly or are even contrary to it (for a while, anyway). Just stand back and look at the big picture. The point here isn’t that anybody can prove that there has never been this extent of Greenland melting at some prior time in the Holocene, but that all of these indicators taken together (Arctic temperatures, low sea ice extent in summer *and* winter, permafrost melting, decreased snow cover, Greenland melting) indicate that the Arctic as a whole really is warming in an exceptional way. Absent some natural factor that could explain all of this happening at once, and none has been postulated, we are left with warming as a consequence of increased GHGs (and secondarily from soot deposition, although as I understand it this has yet to be well-quantified and is in any case a co-factor with GHGs).

  46. Steve Bloom:

    Below is the abstract of a fresh paper that adds to the already-strong argument for Arctic warming. The text is unfortunately available only to subscribers (of which I am not one).

    GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L19602, doi:10.1029/2005GL024216, 2005

    Warming of the arctic ice-ocean system is faster than the global average since the 1960s

    Jinlun Zhang

    Polar Science Center, Applied Physics Laboratory, College of Ocean and Fishery Sciences, University of Washington, Seattle, Washington, USA


    Model results and observations both indicate warming of the world ocean from 1955 to 2003. Forced by reanalysis data, the model also shows that the warming of the arctic iceâ??ocean system is faster than the global average since the 1960s; there is a small but widespread increase in heat content of the Arctic Oceanâ??s waters and a larger increase of latent heat embodied in the oceanâ??s decreasing ice cover. From 1966 to 2003 the modeled mean world ocean temperature in the upper 700 m increased 0.097°C and by 0.137°C according to observations (Levitus et al., 2005); the modeled mean temperature adjusted for sea ice in the corresponding layer of the Arctic Ocean increased 0.203°C. The warming of the world ocean is associated with an increase in global surface air temperature, downward longwave radiation, and therefore net heat flux. The faster warming of the arctic iceâ??ocean system is associated with an amplified increase in arctic surface air temperature, downward longwave radiation, and net heat flux.

    Received 27 July 2005; accepted 1 September 2005; published 5 October 2005.

  47. Steve Bloom:

    See also this recent overview article on Arctic warming, which nicely summarizes the state of the science as of a few months ago: http://paos.colorado.edu/~dcn/reprints/Overpeck_etal_EOS2005.pdf .

  48. Ferdinand Engelbeen:

    Re #41,

    It may be that tidal glaciers in general are not good indicators of temperature. In the case of the very large (7 km wide, 100 m high above water front) Illulisat (Jacobshavn) glacier, the retreat started at or before 1850. But it is interesting that the rate of retreat of the breakup point parallels the local measured temperature (since 1880)…

  49. Ferdinand Engelbeen:

    Re #43,

    You are completely right for Alaska and East Siberia (Barrow is now an average 1°C warmer than around 1940 and 2°C warmer than around 1970), but the rest of the arctic was as warm or warmer than today in the 1930-1940 period. That is based on all circumpolar (over 67N) stations, not one or a few…

  50. Ferdinand Engelbeen:

    Re #45,
    The problem with ice extent/melting of Greenland is that reliable measurements are only available since the satellite era, which is 26 years young. The only indication of probable ice melting in the past is the temperature readings of nearby stations. If one looks at the trend e.g. for Illulisat/Jacobshaven (West Greenland), where ice melting is increasing with app. 0.5 million km2 per decade in the last decades, the yearly average temperature trend was flat 1880-1920, +3.5°C 1920-1930, variable (around a flat trend) 1930-1948, -3°C 1949-1994, +3°C 1995-2004
    Even more interesting: the summer (June, July, August) temperatures dropped from average +7°C in 1900-1980 to +3.1°C in 1983, and slowly went up again to +6°C in 2003-2004. Based on these figures, I suppose that the West Greenland ice melting was larger in the 1930-1950 period than in the 1985-2005 period…
    Alternative explanations may be that the Greenland ice melting has nothing to do with temperature, but with more insolation (less clouds), less precipitation, more soot deposit,…

    The horror story is not what the scientists present as data, but what the media make of a (too) short trend, including the complete melting of the Greenland ice sheet. As long as there is no good explanation why the Arctic was warm(er) in the 1930-1940 period, one can’t know what the trend will be in the next decade(s), let it be in a century or two.