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More on the Arctic

Filed under: — mike @ 22 May 2006

By Michael Mann & Phil Jones (guest)

Svalbard, an Arctic island in the Northern North Atlantic, is predicted to warm considerably more than most of the rest of the earth in many model-based scenarios. See for example the figure to the right, which represents a relatively high-end IPCC Third Assessment Report scenario for the projected surface temperature difference between the period 2071 -2100 and 1961-1990. Svalbard is the island north of Norway at about 80N between 15-30E.

The enhanced warming in this region is related to the issue of polar amplification that we have discussed previously on RC. It also happens that the Svalbard meteorological station is the 2nd station in the World Meteorological Organization (WMO) meteorological station list. This means that it tends to get noticed. The Climatic Research Unit (CRU) of the University of East Anglia maintains one prominent version of the global surface temperature data set and as part of its routine quality control, CRU flags any unusual (anomalous warm or cold) new measurements that come in. Svalbard has now been flagged consistently over the past several months, but the values have been confirmed as accurate by the Norwegian Met Service, which operates the Svalbard station.

Here are the recent Svalbard monthly surface temperature measurements, the long-term (1961-1990) means (“ybar”) and standard deviations (“sd”), and associated anomalies i.e., departure from average (“delta”) for Dec 2005 through April 2006 (all in degrees C):

        Month       Value         ybar       sd      Delta     
        Dec 05      -3.8         -13.3      4.4       +9.5      
        Jan 06      -2.7         -15.3      4.7      +12.6                   
        Feb 06      -9.8         -16.3      3.7       +6.5     
        Mar 06     -13.1         -15.8      3.7       +2.7    
        Apr 06       0.0         -12.4      2.7      +12.4    

The numbers are fairly remarkable. April’06 was warmer than any previously recorded May, and January ’06 was warmer than any previously recorded April. The previously warmest April was -7.0C (1996) -4.3C (2004). There is currently an absence of sea ice off much of the coast of Svalbard, which is also unprecedented for so early in the year.

The April mean temperature is almost 5 standard deviations above the mean, a “5 sigma event” in statistical parlance. Under the assumption of stationary ‘normal’ statistics, such an event is considered astronomically improbable (< 1 in 106), and, like the summer heat wave in Europe in 2003 (which was a 5 sigma event in Switzerland, 3 sigma over Europe as a whole), deserves special attention. As we have nonetheless remarked before on RC, particular events, even seasonally-persistent anomalies as unusual as these, do not “prove” anthropogenic warming. But in a statistical sense, large outliers like this make it more probable that the underlying distributions are shifting and give us a glimpse into the types of anomalies we might expect to become more common in the decades ahead.

Correction and update: (1 June) Micheal Shouler points out that we misread the previous April record (corrected above). And now that the May 06 data has come in at a record-breaking +0.9 C, our statement that April 06 was warmer than all previously recorded Mays is still true – but only just! Things move fast in this field…


88 Responses to “More on the Arctic”

  1. 51
    Steve Bloom says:

    Re #45 response: But Gavin, note this Martin Wild quote from the BBC story: “If this additional carbon feedback is proven to be realistic, than that would raise the climate sensitivity up by a certain amount.” If you meant that this feedback hasn’t been part of past discussions about sensitivity, I think I understand, but otherwise I’m confused.

    Re #49: Note that these studies track the past behavior of this feedback and extrapolate it to the present climate, so whatever diminishment or saturation may have taken place in the past is “built in” to the calculation of future sensitivity.

  2. 52
    Steve Bloom says:

    Also re #49: I should add that as far as I understand it this would be true up until the point where the current climate warms up beyond what it has been in the last 400,000 years. We have a ways to go on that. Once out of the historic range, I assume you’re right that the factors you mention would need to be taken into account, and the new studies would have needed to do so in order to come up with sensitivity estimates comparable to prior ones. But I’m way beyond my expertise in speculating about this, especially since I haven’t even seen the papers yet.

  3. 53
    Ken Rushton says:

    May I draw your attention to an interesting page, which shows the Sea-surface temperatures as compiled by the US navy: https://www.fnmoc.navy.mil/products/NCODA/US058VMET-GIFwxg.NCODA.glbl_sstanomaly.gif . The interesting bit here is that it apparently shows a deeper cross-section than say NOAA’s: http://iridl.ldeo.columbia.edu/SOURCES/.NOAA/.NCEP/.EMC/.CMB/.GLOBAL/.Reyn_SmithOIv2/.weekly/
    The display (I’ve checked it occasionally for years) has been boring, because it shows very little temperature variation in most of the ocean, but recently, in the past couple of years, the temperature around the very northern part of the Atlantic, north of Iceland (and this year west of Greenland) has gone up. It’s now up +4 or 5 degrees. What does it mean? I’ll leave that to you experts, but my armchair guess is that the THC sinking spot has moved over 500 km poleward, and the diagram is showing the warmer waters drawn up form the south, which were formerly a seawater/ice mixture @ -4 degrees or so.

  4. 54
    Hank Roberts says:

    Ken, very interesting! I wonder if that change is in the thesis I cited in #37, 38, I’ll look. The navy always has better info!

  5. 55
    Nigel Williams says:

    All this stuff is happening about as fast as you guys can type!

    Is it the intention that govenments will only be allerted by the final edition of IPCC2006 (circa mid 2007), or are there some other mechanisms available that can produce a reasonably cohesive report to the UN et al that will ring some bells sooner?

    How is this new rate-of-change information being assimilated into the ICPP peer review process?

  6. 56
    Bill Sneed says:

    Re: #44 While it is true that both Midre Lovenbreen and Austre Broggerbreen are well studied it should be mentioned that both are located in one of the warmer parts of the archipelago. The western edge of Svalbard is heavily influenced by relatively warm oceanic and atmospheric currents. Both glaciers are also quite small — about 6 sq. km and 12 sq km respectively and, thus, more likely to influenced by climate variations. Of the approximately 2,200 glacier on Svalvbard, those less than 100 sq. km account for about 47% of the number but only about 34% of the snow and ice covered area. It would seem prudent to exercise some care if one is to use these 2 small glaciers are “mine canaries”.

    Regarding sea ice in the Nordic Seas, Torgny Vinje’s 1 February 2001 paper in the Journal of Climate makes fascinating reading. No doubt things have changed — perhaps significantly — since its publication but it is a valuable perspective nonetheless.

  7. 57
    pat neuman says:

    re 55.

    No bells rung on TV network news this evening (I watched ABC). There was coverage on the hurricane outlook for 2006 which was issued yesterday by the National Weather Service but there was no mention of global warming in their press release. Public broadcasts by meteorologists occasionally talk about a cool flow of air from the Arctic without acknowledging that climate change in the Arctic is being amplified as expected by global climate modelers.

  8. 58
    Dano says:

    RE 50 (Roberts):

    “Emergent properties” is the term used in adaptive management and scenario analysis (as in IPCC) to describe roughly what you propose (fancy term for ‘surprise’).

    But I like your term!

    Best,

    D

  9. 59
    Hank Roberts says:

    Chuckle.
    Reactivity (chemistry): … susceptibility to undergoing a … change that may result in dangerous side effects, such as … toxic emissions. The conditions that cause the reaction, such as heat, … will usually be specified as “Conditions to Avoid” when a chemical’s reactivity is discussed on a MSDS. http://www.weizmann.ac.il/safety/chgl.html

    Reactivity (fission): … a change in power caused a change in reactivity and this in turn had an effect on power. If the change in reactivity is such that the processes caused are against the originating ones, we talk about negative feedback….. In terms of reactor safety it is an obvious intention that all feedbacks should be negative…. As a counter-example … we may mention the RBMK type reactors, because in these positive feedbacks … contributed to the accident of the Chernobyl power plant.

    I’ll skip the psychological uses (grin).

    Aside — on the naval grad school study, at the back — they used monthly averages but could do daily points, the submarine and satellite data is that detailed. And the author makes a clear plea for further declassification and organizing of available data, saying he used almost everything that’s publicly available to model the current situation.

  10. 60

    #57, Pat… The networks will get around to report what is going on……. One day…. Mean time
    there is always newsprint which seems to be way ahead on this issue, the polar regions are for writers
    what the tropics are for TV…

  11. 61
    Paul Biggs says:

    Re;49

    Thanks. If I’m reading this right, the world could warm by 7.7C or more by the year 3000 – a 994 year extrapolation assuming no other factors working in the opposite direction.

  12. 62
    C. W. Magee says:

    Re: 61: I think we might run out of some, if not all fossil fuels sometime in the next 994 years. At the very least, the current rate of emission increases is likely to slow before then.

  13. 63
    PHEaston says:

    Re 57 Pat
    Perhaps you should move to the UK. Here, the media never misses an opportunity to link a weather event to global warming. And the BBC is starting a season on Climate Chaos from tonight (with the great David Attenborough): http://www.bbc.co.uk/sn/hottopics/climatechange/climatechaos.shtml
    It strange, however, that with northern Europe going through one of the coldest, most miserable springs for many years (and a friend of mine in Chicago says they are experiencing the same), there’s no mention of how this fits into global warming theory. (Paradixically, parts of southern England also have hose-pipe bans due to a dry winter – wasy to link to global warming). I would be the first to agree that one event or one unusual year does not make a trend, but we regularly see the media assume just that with hot weather or floods.

  14. 64
    Almuth Ernsting says:

    Re 63:
    The UK and northern Europe going through a cold and miserable spring? You must exclude Scandinavia, which has been very warm. For the UK, March was the first below average month since October 2004. April has been above average, and the Central England Temperature for May is so far above average. It’s indeed a sign of global warming that what would have been warm temperatures in the past are now experienced as ‘cold’!

  15. 65
    teacher ocean says:

    Re 62: I thought we had about 70-100 years of oil and about 250 years of coal left, if we continue with the current rate of consumption.

  16. 66

    well, PH, the zeal of some media outlets to link everything from coastal erosion to dry spells with global warming doesn’t mean it ain’t happening! ;-) and it sure beats the insipid sort of “CO2 – we call it life” from the right-wing think tanks, n’est-ce pas?

  17. 67
    James Davey says:

    Current oil reserves and future use are two very different things. With oil companies already looking at oil sands, oil shales and methane hydrates as potential fuel (and money) sources, and the UK coal industry lobbying government to re-open UK coal seams (which may now, it seems, be competitive, there is a big future in fossil fuels.

    IEA World Energy Outlook data suggests global fossil fuel burning will increase by about 50% by 2030, with no signs of slowdown.

    My guess is that we reach 700ppm CO2 long before we start worrying about fossil fuels running out.

  18. 68
    Leonard Evens says:

    Re #63: Spring in Chicago

    While we have had a lot of cool weather recently, my estimate is that spring arrived about a month earlier than usual. I’ve lived in the Chicago area since 1964. Our typical pattern is that it goes from winter to summer without much of a spring in between. Usually, it hopeless to start planting until late May, but things started growing in April this year. The flowering trees and shrubs have already lost their blooms. While it has been a cool spring, it started much earlier than usual and has lasted quite a while. Temperatures, with a few exceptions have been in the 50s and 60s but the latest forecast is for near 90s by the weekend.

    Our winter was also relatively mild. I’ve been able to cycle outside except for about three weeks in December, which is also unuusal. Usually, I don’t start cycling outside until March or April. I don’t like to cycle when it is much below freezing, so that means our low temperatures this year have been relatively high.

    The problem with Chicago weather is that we are on the boundary between Gulf air and Canadian air, and so we are prone to rapid changes in conditions and we sometimes have long periods of either high or low temperatures. But my general impression is that the trend in recent years has been towards earlier springs.

  19. 69
    Steve Sadlov says:

    RE: #25. Also, salinity.

  20. 70
    Steve Sadlov says:

    RE: #56. Many people fail to realize that ever since people have sailed into the Arctic, the effects you mentioned have tended to keep the broad swath between Iceland, the British Isles, the Greenland – Svalbard ice edge and the Eastern ice edge ice free even in winter, most years. The “Arctic Ice Cap” (a misnomer, for sea ice) has never been round in shape. Never.

  21. 71
    Steve Sadlov says:

    RE: #68 (Lack of) spring in Northern California. Up until now, the most “Springless” year had to be either 2004 or 2005. But this year we are gunning for some new superlatives. We’ve been tricked twice this year into thinking Spring had sprung – once by a REX block back in early Feb then again the more recent one late April into Early May. Both broke down and were replaced by a Siberia Express set up (Ridge out by the date line and persistent trough nearer the W. Coast). We’ll likely have a Bering Sea storm this weekend – the only question will be, is it going to hit above or below 37N. But even anything below 40N is fairly well remarkable this late in the season.

  22. 72
    Dan Kamen says:

    Hello everyone,

    I’m a 20 year old college student who stumbled across RC several months ago. I’m extremely interested in the current research on climate change and its ramifications for our planet but understandably I have very weak footing in the field.

    Please forgive me if my questions betray a misunderstanding of climate science. I’ve been attempting to understand the articles and debates on climate change with very little formal background. It’s a difficult excercise in interpreting technical jargon, so please excuse me if I’ve missed any important points.

    Recently I watched a film “Earth Changes, the Ripple Effect” the fourth documentary in a series entitled “Earth Rising” by Dr. Nick Begeich. Dr. Begeich mentions increased thermal venting in the artic oceans as a possible explanation for the currently inexplicable acceleration of warming in the region. (He cites a 5-15 degree increase in ocean temperature off the coast of Alaska during the late 90’s as evidence)

    Has RC ever discussed the impact of geothermic changes on the energy balance of our planet? Do we have any empirical data on ocean venting? Could natural increases in geothermic activity, perhaps due to the shift of the magnetic poles or other tectonic phenomena, coupled by anthropogenic warming explain the unexpectedly rapid disapearance of the polar ice sheets? And finally, if we lack the empirical data on geothermal activity in the oceans, isn’t it possible that our climate modles fail to include a huge contribution to the energy balance of our planet?

    I would like to thank all the people involved with RC and all the people contributing to the debates on each one of these articles! You set a standard of legitimate scientific debate that is tragically missing from public discussion, this website has been a great resource for me, thanks again!

  23. 73
    pete best says:

    Reply #67

    Coal we have in abundance unfortunately, likely to last as long as 200 years. Oil comes in two generic flavours, light and heavy, by light we mean easy to extract and lots of energy return Oil, 1 trillion barrels used and 1 to 2 trillion barrels left or around 50 years worth, by heavy we mean less energy returned and hearder to refine etc, who knows how much of this we have, possibly some trillions of barrels. Gas at present rates of use will last around 70 more years if no more is found.

    All this fossil fuels provides 85% of our energy needs with a infrastructure to match. Fossil fuels will dominate for decades to come even if we could get the required 65% reduction in present levels by 2050 the climate will still be around 450 ppm and climbing.

  24. 74
    pat neuman says:

    re 63.

    PHEaston,

    Your friend in Chicago should be happier now with warmer temps (and severe weather). I’ve been tracking monthly average temps at climate stations (those with more than 100 years of record). Jan-Apr temperature averages show positive 100 year trends at climate stations in ND and MN. Increasing trends for May and June precipitation are indicated for northeast ND (Devils Lake basin).

    The In-Forum (Fargo, ND) published my letter today called Climate change affects Devils Lake:
    http://www.in-forum.com/articles/index.cfm?id=127753§ion=Opinion

    Plots, 100 year temperature monthly and annual averages and precipitation at climate stations:
    http://pg.photos.yahoo.com/ph/patneuman2000/my_photos

  25. 75
    Hank Roberts says:

    Dan (72): I found pages by Begeich searching on that movie title.
    He has a lot for sale. Caveat emptor.
    http://www.earthpulse.com/src/category.asp?catid=3
    http://www.earthpulse.com/src/productindex.asp#
    He doesn’t show up in Google Scholar, a good place to start checking science claims.

  26. 76
    Hank Roberts says:

    Dan (72): midocean ridge spreading volcanic activity is discussed here:
    http://www.realclimate.org/index.php?p=306#comment-13591
    and following in the general thread on vulcanism. Short answer, it both produces (from fresh erupting lava) and absorbs (due to weathering of newly exposed lava) CO2 and these seem to balance; the rate doesn’t seem to have changed.

    While the midocean ridges are among the least accessible places on Earth, so far there’s no evidence they’ve made big changes in the atmosphere on balance, as compared to say the big basalt flows (“Deccan Traps” etc) occurring in the atmosphere.

    I found that by typing “spreading” into the Search box at the top of the home page here (remembering it was here, so I could sort it out from the fairly long list of posts that mention the word “spreading” retrieved.

  27. 77

    Re Dan #72. The heat from the sun works out at around 400 watts per square meter. The geophysical heat from the core of the earth works out at about 40 mWatts per square meter. Thus the effect from geophysical heat is 0.01% of the heat from the sun, and it has no real effect even when concentrated at the mid ocean ridges because they are several thousand feet below the surface of the ocean. OTOH, the greenhouse effect of carbon dioxide is of the order of 4 watts per sq. meter, and its effect is amplified by water vapour to around 40 watts in round numbers.

  28. 78
    Willis Eschenbach says:

    Gentlemen:

    This is quite frustrating. I attempted to post the following:

    According to GISS, the Svalbard station only started reporting temperatures in mid 1977. How did you determine the long-term (1961-1990) means (ybar) and standard deviations (sd)?

    Thanks,

    w.

    However, it seems to have been caught by the spam filter or something, as it has not appeared. Could you please fix this?

    Many thanks,

    w.

    [Response: The comment was most likely deleted because it was already indicated above that the record is available back to 1911, and the source of the data (Climatic Research Unit, not GISS) was already indicated. –mike]

  29. 79
    Hans Erren says:

    re 78:
    Fair enough, but Svalbard Luft started in october 1977 and Isfjord Radio stopped with continuous recording in june 1976. How was the homogenisation obtained between the two stations. Moreover the nearest other station Bjornoya has the 50’s hotter than the 00’s, Which suggests an inhomogeneity in Svalbard in 1977.

    here is the giss list:
    0 km (*) Svalbard Luft 78.2 N 15.5 E 634010080002 rural area 1977 – 2006
    47 km (*) Isfjord Radio 78.1 N 13.6 E 634010050010 rural area 1912 – 1980
    425 km (*) Bjornoya 74.5 N 19.0 E 634010280003 rural area 1949 – 2006

    [Response: For any further details, you and any other interested readers should refer to the linked CRU website for information and references leading to an extensive body of literature that describes how CRU forms representative composite 5 degree latitude x longitude gridbox estimates (which is what is referred to here) that account for time-dependent sampling variations and potential inhomogeneities associated with the individual recording stations that fall within the same grid cell. –mike]

    [Response:(update) I was a bit careless in my wording. The long-term series from 1911 to date currently maintained by the Norwegian Met Service (and to which we are referring to here) is based on the combined record for the Svalbard airport and Isfjord Radio sites. The latter started in 1911. The Norwegian Met Service combined the two records in one of the recent nordic projects, and any inhomogeneities were taken into account in the process. There is little doubt that the anomalies observed so far this year are unprecedented as far back as the measurements go (early 20th century). – mike]

  30. 80
    Piers Corbyn says:

    YOU SAY: “There is currently an absence of sea ice off much of the coast of Svalbard, which is also unprecedented for so early in the year.”

    This claim is FALSE. I refer you to (HMSO 1964) Met Office ‘Weather in Home Fleet Waters, Volume 1: Northern Seas, Part 1

    A clear map on page 256 of Ice limits for APRIL shows ‘open years’ and ‘heavy years’ which flip-flop to exclude and include Svalbard – West& South coasts – from pack ice. What you claim is ‘unprecedented’ is in fact completely normal. Indeed page 247 states: “…Within this triangular sea (West of Spisbergen) ice is unusual even in April.”

    Thank you – piers@weatheraction.com

    [Response: We should have been more precise in our wording. It is true that April is sometimes ice free. It is very unusual that January is ice free, which was the case this year. The only way to get the type of anomalies seen this year is to either get rid of the sea ice or to have continual southerly advection. –mike]

    [Response:To add to Mike’s comment, it’s also usually the late winter and early spring when the sea ice-cover is greatest in the Arctic, and my colleagues can inform me that the ice-extent this winter, also April has been unusual (winds blow the ice around, and sometimes open waters in the Arctic may arise from that reason – the wind directions also play a role for the temperatures as well). It is also important to look at the larger region, not just in selected locations, but rather the entire Arctic to get the picture. High quality sea-ice data do not go back in time very far, so I’d only trust the measurements since 1979 (after satellite observations start). If you look at the HadISST1.1 data (1979-1999; which I happened to have at hand), then the mean ice-cover edge tends to be located around Svalbard. Looking at the ice-cover for April 1990, which is an April with the minimum ice cover in the area for the 1979-1990 interval, you still don’t see completely ice-free waters east off Svalbard for the entire month. For those of you who understand Scandinavian, there is an article about this on met.no (posted as early as 27.01.2006) -rasmus]

  31. 81

    There seems to be some correlation between sea ice extent around Svalbard and the temperature record of Jan Mayen (some 1100 km SW of Svalbard). From E. Isaksson e.a.:

    The Austfonna record correlates well with the temperature record from the more distant and southwesterly located Jan Mayen. A comparison of the ice-core and sea-ice records from this period suggests that sea-ice extent and Austfonna 18O are related over the past 400 years. This may reflect the position of the storm tracks and their direct influence on the relatively low-altitude Austfonna.

    According to the GISS database, the temperature record of
    Jan Mayen shows near as high temperatures in the period 1930-1960 as in the past years…

  32. 82
    Steve Bloom says:

    This seems as if it would have major implication from the poles to the tropics: http://www.mercurynews.com/mld/mercurynews/living/health/14666521.htm . Sounds to me like a post topic.

  33. 83
    John C Wilson says:

    5 standard deviations is huge. You are reporting an anomaly that is ongoing January to April. Has someone yet looked to find a proximate cause or are we purely at observation? One thing that occurred to me was that we could be seeing the result of a local methane release but that one does not square well with high Jan. temps when there would be no sun at Svalbard. Any other hypotheses?
    Also, as a 54-year resident of Chicago: the first 3 weeks of December were frightful, esp. since a mild Oct & Nov meant no acclimatization. After that, no winter. It could be St. Louis or Louisville. April was the mildest and most consistent in my memory or in my bicycle diaries by a long shot. May has been uneven but warm. And set to finish in the 90’s.

  34. 84
    Hank Roberts says:

    The problem is that comment tools have no standard for “character encoding” — and web pages may have any of a dozen different character encodings. See your browser’s “view” menu in Firefox for example. What we see is a picture (font) but what’s behind that — and what’s actually cut there and pasted here — is a computer code (hexadecimal, octal, binary, HTML). So when you paste something in, it brings with it its encoding — then the comment software managles that, and your browser’s set to whatever View option you chose so it interprets the mangle as a garble and displays that on the screen.

    Someone technically competent can probably clarify that. I don’t think there’s a solution except to post a link to the actual page instead of cutting and pasting — using hypertext as it should be used, eh?

  35. 85
    Hugh says:

    Sorry, I appreciate this is an inappropriate use of this thread but I’m hoping someone can point me in the right direction toward a graph.
    A couple of months ago I recall seeing a very useful plot of CO2 emissions over the last 650,000a, and now I can’t find it again.
    Before you jump to conclusions about my stupidity…it’s *not* the one attached to the 650,000 RC thread, but one that more clearly showed current and, I think, projected concentrations as well.
    Any help gratefully received

    Hugh

  36. 86
  37. 87
    joel Hammer says:

    “By giving the appearance of symmetric feedback, people have an excuse to say, ‘Maybe we don’t have to worry so much,'” Harte said. “But while there are uncertainties in the feedbacks, all the major feedbacks are positive, meaning they would increase warming, and we know of no significant negative feedbacks that would slow warming.”

    Comment by Hugh – 23 May 2006 @ 11:38 am

    This is one reason why skeptics like me exist. Nobody on this scientific message board has challenged this statement, so I guess you all believe this or just keep your doubts to yourselves. No significant negative feedbacks exist in nature on global temperature? How do you explain the Ice Age? How do you explain why runaway global warming hasn’t occurred before now?

    [Response:On the ice age, you have it backwards. If there were significant negative feedbacks we didn’t know about, then in fact it would be very difficult to get an ice age with the relatively small forcings Nature provides. With regard to lack of spontaneous runaway global warming in the past, it would be fair to say that the increase of infrared emission to space as temperature increases constitutes THE fundamental “negative ” feedback allowing climate to equilibrate. Harte’s comment was addressing the uncertainties in the climate sensitivity, and I didn’t see anything in his remark that implied exclusion of a process like increase of emission with temperature. With regard to climate sensitivity in the next few centuries, the issue is how steeply emission increases with temperature, and there, on the whole I think Harte had it right. We know of a great many positive feedbacks that could increase the sensitivity well beyond the mid-range of the IPCC sensitivity, but we know of essentially no plausible feedbacks that could reduce the sensitivity substantially below the lower end. Now, between the low end and the mid range of IPCC sensitivity, there are indeed some cloud feedbacks operating that could be considered “negative” feedbacks, and in that range it would be justified to qualify Harte’s remark somewhat. Still, it takes a rather special set of circumstances for clouds to significantly damp climate sensitivity and I think it’s fair to say that we know of a lot more mechanisms that could potentially increase climate sensitivity. –raypierre]

  38. 88
    Karen Street says:

    For #87, positive feedback doesn’t mean increasing temperature and carbon and negative feedback doesn’t mean reducing the same. There is positive feedback if you are headed in a direction — temperature and carbon up or down — and changes on Earth positively reinforce this shift. As the Earth warms, there is less ice so reflectivity goes down so the Earth warms more. As the Earth cools, there is more ice, so reflectivity increases and the Earth cools more. Both are examples of positive feedback.


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