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Unforced variations: May 2020

Filed under: — group @ 1 May 2020

This month’s climate science open thread.

188 Responses to “Unforced variations: May 2020”

  1. 1
    zebra says:

    Alastair McDonald from previous UV#63,

    “Does anyone agree with me that if we have one summer where Arctic sea ice disappears, then it will also disappear during every following summers?”

    I don’t. First, you have to be clear what you mean.

    1. As I understand it, the condition “ice-free” is defined as below 1 million square kilometers.

    2. I’m never quite sure what people mean by “summer”, but let’s assume it is three consecutive months.

    This would indeed be a serious condition, but it doesn’t follow that it would necessarily persist in subsequent years. Look at the curve:

    https://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph/

    Note that the maximum has declined at a much slower rate than the minimum. So, the ice recovers even when large areas have gone uncovered over those “summer” months, as in 2012. There’s nothing magical about that million square kilometer mark; all the physical conditions that bring back the ice will still exist.

    People tend to forget that the arctic ice is strongly influenced by the movement of air and water in and out of the area; just increasing the area of insolation is not determinative.

  2. 2

    From last month’s thread:

    Alastair asked:

    Does anyone agree with me that if we have one summer where Arctic sea ice disappears, then it will also disappear during every following summers?

    This is because the sea ice will not be able to regrow during the following winters to the extent that it will produce enough ice to last the following summer. Once it is ice free during one summer it will have passed a tipping point.

    No, with all due respect I don’t agree. The primary reason is that modeling studies have found otherwise:

    https://www.nature.com/articles/471047a

    Tietsche et al., 2011–Dr. Notz, referenced in elsewhere in comment I quoted above, is a co-author–is the primary reference, but this review provides more context. In a nutshell, arbitrarily removing the ice sheet throughout most of the coming century did not lead to permanent loss of sea ice; it would typically regrow to characteristic extents.

    Secondarily, I observe that there is a *lot* of variability over the course of a single year or even season; the sea ice is perfectly capacle (so to speak) of veering from exceptionally low or even record-los extent to well above recent norms–and then back again.

    So an exceptional melt season does not seem to imply a freeze season so slow that recovery is impossible.

  3. 3
    John Pollack says:

    Alastair McDonald @63 (April) No, I don’t agree that once the Arctic summer sea ice disappears once, it will do it every year thereafter, but you made me think about it.

    Summer ice varies substantially from year to year. The oldest and thickest ice tends to get jammed up against the northern Canadian islands, and doesn’t melt out. The first year that the ice “disappears” it will probably be because an anomalous south wind persists long enough to dislodge that ice, and spread it out northward. That’s not a usual condition. In addition, the sea ice minimum is in September, when the arctic sun is getting low, and it’s already getting colder. I would expect a real tipping point as more dark ocean gets exposed earlier in the summer, when it can absorb more solar heat.

    I would also expect, assuming that there are still deniers around, that there will be a vigorous dispute on the meaning of “disappear” for the arctic sea ice. Here’s how Prof. Notz and co-authors put it: “In most simulations, the Arctic Ocean becomes practically sea‐ice free (sea‐ice area < 1 million km2) in September for the first time before the year 2050."
    Less than 1 million square kilometers of sea ice isn't zero, and it can still sink your boat. It can also allow a picture of an (increasingly rare) polar bear on an ice floe, fishing. WUWT2050 would be raving about how the ice hasn't disappeared, and the "experts" are telling another big fib to verify their failed predictions.

    I believe that it's important to understand that the critical climate issue is the increasing amount of dark ocean water in the arctic absorbing solar energy earlier in the summer, when it's most intense. The year exact year in which the arctic sea ice "disappears" in September – whether that means under 1,000,000 km2, or the last ice cube, is more a side show.

  4. 4
    jgnfld says:

    Re. AM’s question at the end of last month’s unforced entry…

    Given

    1) that “no ice” is usually defined as under a certain minimum, and
    2) that ice extent minimums are only weakly correlated with summer maximums

    I would expect some years/decades of transition rather than an abrupt collapse.

  5. 5
    MA Rodger says:

    Alastair B. McDonald @63 – April UV Thread,

    You cite the Notz et al (2020) ‘Arctic Sea Ice in CMIP6’ and its finding that even under low emissions future Arctic Sea Ice will, in the words of its lead author, “nevertheless likely disappear occasionally in summer even before 2050” and argue that a single year with an ice-free Arctic Ocean in summer will constitute a tipping point and lead to continued ice-free summers.

    The contrary view is set out by firstly Notz’s quote above that talks of it ‘disappearing occasionally,’ and secondly Tietsche et al (2011) ‘Recovery mechanisms of Arctic summer sea ice’, a paper that is co-authored by Notz, which found an absence of such a tipping point.

    But it should also be mentioned that, like the famous questioning of the ability of a gunman engaged in a gun fight to count the gun shots accurately, the accuracy of modelling of Arctic Sea Ice is often the subject of questioning, although this questiong usually concerns the rapidity of reaching the ice-free summer not the longevity of such an event once it has arrived.

  6. 6
    MA Rodger says:

    The latest UAH TLT news has been posted-up on Wattsupia* with a April anomaly of +0.38ºC, the lowest anomaly of the year-to-date (which recorded +0.56ºC, +0.76ºC & +0.48ºC through its first 3 months) but this is still the 4th warmest April in the UAH TLT record.
    The warmest Aprils in UAH TLT now run 1998 (+0.74ºC), 2016 (+0.73ºC), 2019 (+0.44ºC), 2020 (+0.38ºC), 2005 (+0.33ºC), 2010 (+0.32ºC), 2017 (+0.31ºC), 2002 (+0.23ºC) & 2018 (+0.21ºC).
    March 2020 sits =46th in the UAH TLT all-month anomaly record.

    (* The reason for the posting on Wattsupia was because Woy Spencer has noted that the … make sure you’re sitting down … deep breath … wait for it … the 2-monthly drop in the UAH TLT Northern Hemisphere anomaly is the second biggest of that much-convoluted measure in the entire UAH TLT record which is now apparently a whole 497 months in length.
    Woy couldn’t wait to tell his chum Willard Watts who was eager to make a big thing of this astoundingly-trivial piece of information, and in the process within his knock-em-dead headline attributing the result to the NOAA satellite that was used to provide the measurements rather than the blunderful computations of Woy Spencer which yielded the figure presented.
    And these being a bunch of prize muppets, they fail to note that the said calculated NH April 2020 anomaly may have tumbled down from a heady February value, but at +0.43ºC it remains above the UAH long-term trend leaving the only sensible conclusion that it is not a shiver-me-timbers April we have. Rather it was a “scorchyisimo!!” February.)

    Now a third-of-the-way through the year, the start to 2020 averages +0.55ºC, 3rd warmest on record after El-Niño-boosted 2016 (+0.73ºC) and 1998 (+0.59ºC) and sitting ahead of 4th-placed El-Niño-boosted 2010 (+0.45ºC).
    The ‘warmest start-of-year table’ in UAH TLT runs as follows:-
    2016 … … … +0.73ºC
    1998 … … … +0.59ºC
    2020 … … … +0.55ºC
    2010 … … … +0.45ºC
    2019 … … … +0.39ºC
    2017 … … … +0.37ºC
    2018 … … … +0.26ºC
    2018 … … … +0.27ºC
    2007 … … … +0.26ºC
    2002 … … … +0.25ºC

  7. 7
    Mr. Know It All says:

    Why define “ice free” as 1,000,000 sq. km.? To get the Al Gore Warming believers panties in a big wad, why not define “ice free” as the ice area that it normally goes down to – whatever that number is. Then we can see headlines like: “ARCTIC OCEAN ICE FREE IN 2020 FOR FIRST TIME EVER!”
    ;)

  8. 8
    William B Jackson says:

    #7 this post is typical of the nonsense we expect from the ignorant and proud of it. SAD! Mr. Know It All proving his cognomen a falsity for definitely not the first time ever!

  9. 9
    Piotr says:

    Re: “Mr. Know It All” (7): “Why define “ice free” as 1,000,000 sq. km.? To get the Al Gore Warming believers panties in a big wad, why not define “ice free” as the ice area that it normally goes down to – whatever that number is. Then we can see headlines like: “ARCTIC OCEAN ICE FREE IN 2020 FOR FIRST TIME EVER!” ;)

    Maybe the answer is in … the text you comment? I quote: “the Arctic Ocean becomes practically sea‐ice free (sea‐ice area < 1 million km2"
    "Practically". "Practically" perhaps as in: the Arctic Ocean that has less than 7% of its area covered with ice behaves, with respect to albedo, air-sea exchanges of gasses and heat, or providing platform for seals and polar bears, "PRACTICALLY" like an "ice-free Arctic"?

    Or maybe it has something to do with the way we measure/report the "ice"/"ice-free" area today? NCIDC gives the "Arctic Sea Ice Extent" as the area "with at least 15% o ice". Which means that if you have 80% of water and 20% of ice, NCIDC lists is as "ice"

    Hmm, should we now discredit NSIDC, which apparently systematically OVER-STATES the sea-ice area, probably "to get the panties of [Mr. Know it All and other believers in Trump School of Climatology] in a big wad" ?

    Ooops, I forgot to remind everybody how humorous this was. ":)".

  10. 10

    Why define “ice free” as 1,000,000 sq. km.? To get the Al Gore Warming believers panties in a big wad, why not define “ice free” as the ice area that it normally goes down to – whatever that number is. Then we can see headlines like: “ARCTIC OCEAN ICE FREE IN 2020 FOR FIRST TIME EVER!”

    Er, because unlike KIA, the scientists who have adopted this convention are interested in physical reality, not political point-scoring?

  11. 11
    Dan says:

    re: 7.
    Once again KIA flaunts his gross scientific ignorance. Hint for you, junior: Al Gore is not a climate scientist. He is a politician.

    Who utterly failed to teach you about critical thinking and how to learn when bringing you up? All you do is spout ignorance and look for affirmation from denier websites for affirmation for your insecurity and inability to admit to being wrong. What cowardice.

  12. 12
    Mal Adapted says:

    Mr. Ironically Anosognosic Typist:

    To get the Al Gore Warming believers panties in a big wad, why not define “ice free”

    Somehow I’m not as outraged by IAT as I am by E-P, maybe because IAT’s interjections are always patent nonsense, while E-P mixes sense and nonsense together. And while IAT’s comment is predictably coarse and gratuitous, at least it’s not explicitly racist. Anyway, this is about all the outrage I’ve got right now:

    Why get anyone’s “panties in a big wad” at all? The phrase “ice free” is in the public domain. Scientists will choose the definition that means something to their peers, while Humpty Dumpty and IAT may freely redefine it for their purposes. Neither appears to get the whole scientific thing, however. You know: “First define a shared, specialized vocabulary with your peers, to enable mutual review. Huh? Who the heck is Al Gore? Is he hypothermic?” Of course IAT may redefine any word or phrase he wishes, in his quest for illusory mastery. The rest of us are free to explain, politely or otherwise, why he’s full of figurative feces. All subject to collective outrage and/or moderator intervention. Meh.

  13. 13
    Jim Galasyn says:

    Are there any early results on surface warming due to the recent abrupt decline in sulfate pollution?

  14. 14
    Ken Fabian says:

    Since there are going to be shaded places around the Arctic coast that never get sunshine I think the conditions for some summer ice will persist a long time after most of the ice in open ocean is gone. Which is good reason for treating absolute zero ice as a big warming step beyond the climatically significant “effectively zero” across the open Arctic Ocean.

  15. 15
    MA Rodger says:

    The RSS TLT web-browser tool has posted the April Global anomaly of +0.77ºC, the lowest anomaly of the year-to-date (which recorded +0.86ºC, +1.02ºC & +0.84ºC through its first 3 months) but April 2020 is still the 4th warmest April in the RSS TLT record (as per UAH).
    The warmest Aprils in RSS TLT now run 2016 (+0.99ºC), 1998 (+0.89ºC), 2019 (+0.80ºC), 2020 (+0.77ºC), 2010 (+0.63ºC), 2017 (+0.59ºC), 2005 (+0.58ºC), 2018 (+0.48ºC) & 2014 (+0.46ºC).
    April 2020 sits 19th in the UAH TLT all-month anomaly record ( =46th in UAH).

    Now a third-of-the-way through the year, the start to 2020 averages +0.87ºC, the 2nd warmest on record after El-Niño-boosted 2016 (+1.06ºC). (In UAH 2020 also sat below El-Niño-boosted 1998.)
    The ‘warmest start-of-year table’ in RSS TLT runs as follows:-
    2016 … … … +1.06ºC
    2020 … … … +0.87ºC
    2019 … … … +0.72ºC
    1998 … … … +0.71ºC
    2010 … … … +0.70ºC
    2017 … … … +0.64ºC
    2018 … … … +0.53ºC
    2007 … … … +0.53ºC
    2015 … … … +0.52ºC
    2005 … … … +0.51ºC

    Mentioned @6 above, the Northern Hemisphere anomaly 2-monthly fall which managed headline coverage on the rogue planetoid Wattsupia isn’t as spectacular within RSS as it is with the second-place UAH drop on record. In RSS TLT this convoluted measure was -0.32ºC, only managing the 20th largest drop in the RSS TLT record.
    The NH Extra Tropical value (the measure within UAH which initially attracted the denialist Woy Spencer to this crazy denialist pedantry) in RSS TLT fell by a whopping -0.85ºC over the 2-month period in RSS TLT and on the RSS web-browser tool is now back from its excurtion off the top of the chart.

    Also reporting fo April 2020 is the Copernicus ERA5 reanalysis of SAT.
    ERA5’s April Global anomaly of +0.70ºC, a small rise on March. The first three months of 2020 yielded anomalies of +0.77ºC, +0.80ºC & +0.68.ºC
    2020 was the 2nd warmest April in ERA5, just behind top-spot 2016 The warmest Aprils in EAR5 now run 2016 (+0.71ºC), 2020 (+0.70ºC), 2019 (+0.62ºC), 2017 (+0.51ºC), 2018 (+0.49ºC), 2010 (+0.44ºC) & 2007(+0.36ºC).
    April 2020 sits 9th in the ERA5 all-month anomaly record.

    The ‘warmest start-of-year table’ in RSS TLT runs as follows although a graphical year-on-year plot of the ERA5 anomalies (usually 2 clicks to ‘download your attachment’) may give a better understanding of the level of “scortchyissimo!!!” likely this year given the temerature through this early part of the year has not been boosted by a stonking-great El-Niño:-
    2016 … … … +0.79ºC
    2020 … … … +0.74ºC
    2017 … … … +0.62ºC
    2019 … … … +0.58ºC
    2018 … … … +0.46ºC
    2010 … … … +0.43ºC
    2015 … … … +0.36ºC

  16. 16
    Jim Galasyn says:

    MA Rodger at #15, thanks for the fresh data! Seems to support the idea that we’re seeing significant surface warming as air pollution declines.

  17. 17
    Russell says:

    14

    Please look at a globe, and recall that as at high latitudes the midnight sun circles the horizon, so since Arctic sea ice floats in the Arctic ocean, there’s not much if any topography shade it from the sun.

    The angular limit of sea surface reflection is what counts.

  18. 18
    Chuck says:

    Killed In Action says: “Why define “ice free” as 1,000,000 sq. km.? To get the Al Gore Warming believers panties in a big wad, why not define “ice free” as the ice area that it normally goes down to – whatever that number is. Then we can see headlines like: “ARCTIC OCEAN ICE FREE IN 2020 FOR FIRST TIME EVER!”

    Chuck – I’ve never seen you post anything even remotely intelligent or scientific. Do you get paid to be a ‘professional dumbass’ or is it an inherited condition?

  19. 19
    Piotr says:

    Re: 14 Huh? Area of the sea-ice shaded by the coast is MANY ORDERS OF MAGNITUDE smaller than the area of unshaded seaice. Melting of the Arctic sea-ice has GLOBALLY relevant implications (positive albedo feedback to global warming, air-sea exchanges in gases and heat, ecology of high seas -sea-ice algae and animals), your shaded ice has practically ZERO global impact. So why would you even bring it up?

    It’s like saying: Yes, we have cut 99.999% of the forest, but a few trees survived in a difficult to access ravine. “Which is good reason for treating absolute zero of [surviving trees] as a big deforestation step beyond the ecologically significant “effective deforestation” (99.999%) ?

    Saw a tree and missed the forest?

  20. 20
    John Pollack says:

    I think that in the interest of clear and accurate communication, “ice free” needs a modifier, such as “essentially”, “virtually”, or “nearly”, or at least an asterisk with a footnote. The intent is that people become aware that they need to consult the definition of “ice free” being used because there are potentially important exceptions. An ocean that is essentially ice free for climate purposes or satellite detection may not be for marine organisms or navigation purposes.

    This may not have been a significant issue when there was a reliable minimum of several million km2 of arctic sea ice at the end of the summer. However, we are now entering an era when this soon won’t be the case. The distinctions between 900,000 km2 of summer ice, a few lingering floes in sheltered locations, or nothing but a few melting icebergs, will become important.

    For me personally, there is also a truth-in-advertising issue. If I buy a bunch of “seedless” grapes and crunch down on a few hard seeds, I would not be happy. The same goes for an “ice-free” arctic that could sink my boat.

  21. 21
    MA Rodger says:

    Jim Galasyn @15,
    My view of the number I present @14 is somewhat different to yours.
    As far as the economic slowdown resulting from Covid-19 reducing polution levels and thus impacting today’s climate numbers, I have previously run through a back-of-fag-packet calculation addressing the potential early impact although I note I didn’t complete the calculation which suggested a 0.4% monthly appearance of a full -0.6ºC global temperature response would be the rough size of impact from the disappearance of aerosol forcing.
    (I think the 0.74Wm^-2 reduction used was simply something of the correct order of magnitude. IPCC AR5 AII Table 1.2 gives a 2011 ‘Aerosol (Total)’ value of -0.9Wm^-2.)
    So after 3 months of Covid-19, the temperature response would be something like -0.6ºC x 0.004 x 3 = -0.0072ºC, an effect far too small to be apparent within global temperature measurements.

  22. 22
    Ray Ladbury says:

    Chuck: “I’ve never seen you post anything even remotely intelligent or scientific. Do you get paid to be a ‘professional dumbass’ or is it an inherited condition?”

    Or a third possibility–did his dumbassery result from a prolonged and unremitting exposure to Faux News and Breitfart.

  23. 23
    mike says:

    from Carbon Brief. This paper suggests that the covid pandemic will cause the 2020 CO2 increase to be smaller by 0.32 ppm. It’s not a huge reduction, but it’s there and is not insignificant.

    here’s the link: https://www.carbonbrief.org/analysis-what-impact-will-the-coronavirus-pandemic-have-on-atmospheric-co2?utm_campaign=RevueCBWeeklyBriefing&utm_medium=email&utm_source=Revue%20newsletter

    and a quote:

    “A team of leading climate scientists at the Met Office and the Scripps Institution of Oceanography have calculated (see chart above) that, even though global emissions are currently plummeting, this year’s annual average level of CO2 concentrations will still increase. As they explain:
    “Across the whole year, we estimate CO2 levels will rise by 2.48 parts per million (ppm). This increase is 0.32ppm smaller than if there had been no lockdown – equivalent to 11% of the expected rise.”
    To put that into perspective, the famous “Keeling curve” reveals that atmospheric CO2 has steadily risen every year on record – from an annual average of 316ppm in 1959 to 411ppm in 2019.

  24. 24
    mike says:

    at MAR:
    April CO2

    Apr. 2020: 416.18 ppm
    Apr. 2019: 413.52 ppm

    co2.earth

    I think your CO2 experiment from last summer is not particularly close anymore. As I recall, you had numbers for spring 202 at under 2.0 ppm monthly average in yoy increase. Can you update please? Am I remembering this incorrectly?

    I expect 2020 to be hottest year on record, but it might come in second and only be the hottest non-EN year. Time will tell on that.

    Cheers and warm regards to all,

    Mike

  25. 25
    Jim Galasyn says:

    Thank you, MA Rodger @21, that’s very helpful!

  26. 26
    zebra says:

    A Graph Is Worth A Thousand Words,

    People, please, look at the numbers on Arctic Sea Ice, and think about the physics:

    https://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph/

    Step 1: Click off the plots shown.
    Step 2: Click on the 4 decadal averages given.
    Step 3: Set “start month” to August.

    This gives a nice visualization for some basic quantitative reasoning. Whether it is 1 million or zero, we are a very long way from achieving it for a 3-month ‘summer’, given the already observed decline, and the physics.

    Would anyone like to offer a scenario that would change the dynamic, resulting in a serious acceleration and inhibited yearly recovery? Hasn’t happened over 40 years, so it better be good.

  27. 27
    Truax says:

    Can anyone offer any insight into the study “The lightness of water vapor helps to stabilize tropical climate” Science Advances (2020). The finding seems to be that water vapor’s effect on atmospheric uplift is very large, and that it will increase exponentially with a warmer climate causing a negative feedback. The claim is that vapor buoyancy increases the amount of energy returned to space over the tropics by 1-3 W/m2. That seems small to me (and it would already be measured by satellite for any warming that has already occured), but will this have a significant effect on models or predictions?

    [Response: This is already included in models (and would be part of the lapse rate feedback in most analyses). It’s just a different way of breaking down the different effects. – gavin]

  28. 28
    Russell says:

    22.

    just so, but disturbing paper in The Journal of Science Communication warns that a lamentably parallel syndrome may arise from prolonged and unremitting exposure to The Guardian, The Nation, Teen Vogue, and Vanity Fair.

    https://vvattsupwiththat.blogspot.com/2020/05/there-are-two-sides-to-every-echo.html

  29. 29
    Piotr says:

    John Pollack (20): “I think that in the interest of clear and accurate communication, “ice free” needs a modifier, such as “essentially”, “virtually”, or “nearly”, or at least an asterisk with a footnote.”

    And putting a modifier AND an explanation, and not in some footnote, but right there, immediately in the text, WAS NOT enough? see your post (3):

    “Here’s how Prof. Notz and co-authors put it: “In most simulations, the Arctic Ocean becomes practically [sic] sea‐ice free (sea‐ice area < 1 million km2) [sic] in September for the first time before the year 2050.""
    John Pollack (3)

    ===
    John Pollack (20): "For me personally, there is also a truth-in-advertising issue. I would not be happy […] for an “ice-free” arctic that could sink my boat."

    Then don't wait for 2050 – complain NOW to NSIDC about their false advertising on a much larger scale – they count as ice-free water anything that has … less than 15% of ice. Can certainly sink your boat. For a comparison <1 mln km2 ice – that's less than … 7% of the Arctic Ocean.

    But hurry up – others have much stronger case against NSIDC, say: "I relied on NSIDC data for planning my ski trek to the North Pole, and imagine my surprise when what they claimed to be "ice" turned to be … 85% open water. Thank you NSIDC!"

  30. 30
    Andrew Jaremko says:

    A question for the professionals about an article just published in AAAS Science Advances 06 May 2020: Vol. 6, no. 19, eaba1951 DOI: 10.1126/sciadv.aba1951
    URL: https://advances.sciencemag.org/content/6/19/eaba1951

    Title: The lightness of water vapor helps to stabilize tropical climate

    Abstract: Moist air is lighter than dry air at the same temperature, pressure, and volume because the molecular weight of water is less than that of dry air. We call this the vapor buoyancy effect. Although this effect is well documented, its impact on Earth’s climate has been overlooked. Here, we show that the lightness of water vapor helps to stabilize tropical climate by increasing the outgoing longwave radiation (OLR). In the tropical atmosphere, buoyancy is horizontally uniform. Then, the vapor buoyancy in the moist regions must be balanced by warmer temperatures in the dry regions of the tropical atmosphere. These higher temperatures increase tropical OLR. This radiative effect increases with warming, leading to a negative climate feedback. At a near present-day surface temperature, vapor buoyancy is responsible for a radiative effect of 1 W/m2 and a negative climate feedback of about 0.15 W/m2 per kelvin.
    (end abstract)

    The paper seems to be proposing that they have a new analysis and modeling for the mechanism that isn’t included yet in climate models. I’d love to hear from the professionals about this. How new , valid, and/or significant is this likely to be?

    [Response: See above – gavin]

  31. 31
    MA Rodger says:

    Truax @27 and Andrew Jaremko @30,
    Further to the comment Response @27, the referred paper Seidel & Yang (2020) ‘The lightness of water vapor helps to stabilize tropical climate’ does itself actually say that its analysis does not involve anything extra to present climate models and that it does no more than examine the particular phenomenon of water vapour buoyancy to understand its effect.

    “Contemporary cloud-resolving and general circulation models have the physics necessary to simulate the vapor buoyancy feedback. Therefore, the feedback should be reflected in past model-based assessments of climate sensitivity. However, simulation does not entail understanding. This study explains how the vapor buoyancy feedback occurs and presents evidence that it helps to shape Earth’s tropical climate.”

    Given the way things climatic can be misused by denialists and readily misunderstood by other commentators so it would have been better if the context of the study were set out more prominently and clearly.
    I note this coverage entitled ‘Cold Air Rises – How Wrong Are Our Global Climate Models?’ (the item also reposted elsewhere but with alternative titles) talking of an “an overlooked effect.” Mind it does also quote the lead author explaining their next bit of work which implies their paper does not have any profound impact on climate moodels; “Now that we understand how the lightness of water regulates tropical climate, we plan to study whether global climate models accurately represent this effect.”

  32. 32
    jgnfld says:

    piotr @29 “Then don’t wait for 2050 – complain NOW to NSIDC about their false advertising on a much larger scale – they count as ice-free water anything that has … less than 15% of ice. Can certainly sink your boat.”

    Sarcasm noted. That said, on the somewhat rare occasions when I have my boat in an area with ice, I NEVER consult climate maps. For some odd reason, I use ice maps from the Canadian Ice Service which provide maps tailored to navigation rather than climate science.

    Deniers will use ANY factoid–like piotr’s previously mentioned tree in a remote ravine–to deny the reality of the rest of any fact base. It’s what deniers do.

  33. 33
    nigelj says:

    Zebra @26 says “This gives a nice visualization for some basic quantitative reasoning. Whether it is 1 million or zero, we are a very long way from achieving it for a 3-month ‘summer’, given the already observed decline, and the physics.”

    Looking at the graph posted by zebra, and extrapolating just the recent trends has the arctic nearly ice free (1 m sq kms ) for the three months of summer by approx. 2060. Not sure if any this qualifies as a very long time, which is a very subjective statement. It certainly suggests substantial change possibly in my lifetime.

  34. 34
    Andrew Jaremko says:

    #27 response by gavin #31 MA Rodger
    Thank you for the response saying that this was included in the models “by another name”. It was my expectation that such a physically fundamental process wouldn’t have been included.

  35. 35
    James McDonald says:

    Could someone provide a good reference that explains the different relaxation times for radiative vs. collisional energy transfer from CO2 to other atmospheric molecules at sea level?

    I recall reading somewhere that at one atmosphere collisions dominate over radiation in removing the IR energy absorbed by CO2 molecules, but can’t remember where.

    I tried using Google Scholar and then a more general search, but the misinformation sites so dominate in the results that I couldn’t find useful actual numbers.

    (I’m asking because I want to include such a reference in a reply in a Quora discussion.)

    Thanks in advance…

  36. 36
    Killian says:

    Re #26 zebra said A Graph Is Worth A Thousand Words,

    …This gives a nice visualization for some basic quantitative reasoning. Whether it is 1 million or zero, we are a very long way from achieving it for a 3-month ‘summer’, given the already observed decline, and the physics.

    Would anyone like to offer a scenario that would change the dynamic, resulting in a serious acceleration and inhibited yearly recovery? Hasn’t happened over 40 years, so it better be good.

    A fair enough point, but the problem is this type of thinking – Can’t happen! – is dangerously naive in some regards because it sets people up to ignore the long-tail risks. Fact is, the planet has never, ever been under these conditions and we are pushing every negative button there is to push. The point is, talk science as you wil, but don’t confuse science and policy. The latter cannot and should not focus on what is likely, but on what is the worst that can happen because the ultimate risks are existential – to society and many species, and maybe even humans.

    I’m not saying you are confusing the two, just a reminder to Dear Readers.

  37. 37
    Killian says:

    As to the science, zebra, the issue is not a 3-month Blue Ocean event, but when any Blue Ocean event takes place. Talking about a 3-month even it like talking about climate change in 2500. And, if we get to a 3-month Blue Ocean events, I’m betting no current ecosystems will survive in anything like the structure they currenly have, so it’s a moot point; purely academic in any germane sense.

  38. 38
    zebra says:

    Piotr and jgnfld,

    Nothing wrong with what you say, but even with multiple comments I still haven’t seen a clear statement… even from Alastair, who originated the discussion… of what we are talking about duration-wise.

    Is “summer” 3 months, or 3 weeks, or 3 days?

    Likewise, when Notz says “in September”… what does that mean? 30 days “ice free”?

    The nominal value, one million or zero, is a trivial question compared to that. Again, look at quantities as I suggest at #26.

    It’s true that Denialist are going to distort stuff no matter what, but vague language offers them too much opportunity.

  39. 39
    MartinJB says:

    Pretty extensive survey of estimates of SLR by 2100 and 2300 under RCPs 2.6 and 8.5. These are both improbable book ends, IMHO, so this mainly serves to constrain the likely range. The medians for 2100 under 2.6 and 8.5 are 0.45m and 0.93m, respectively. To get a likely range, 17th percentile for RCP 2.6 is 0.3m, and the 83rd percentile for RCP 8.5 is 1.32m. (So, the Obamas’ Marthas Vineyard house should be safe for their lifetimes.)

    It also compares estimates made in 2009-2013 to those from 2014-2018. The largest difference in the estimates for 2100 is a decrease in the variance with the newer studies, while there is a marked increase in the values of estimates for 2300 in the newer studies.

    https://www.nature.com/articles/s41612-020-0121-5

  40. 40

    #33, nigel–

    There’s every reason to think that the function here isn’t linear. Note, for example, that while the decline in ice *volume* can also reasonably be treated as a linear trend, the following is also true:

    1) It’s declining faster than extent, and
    2) Peak-to-peak amplitude is increasing as well, since
    3) The fastest observed decline is for the annual minimum.

    Here’s a plot of selected volumes over the annual cycle, per the PIOMAS reconstruction product:

    http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/ice_volume/BPIOMASIceVolumeAnomalyCurrentV2.1_CY.png

    Note that the lowest years, such as 2012 and last year, show volumes at annual minimum less than ~40% of the 1979-2018 mean. (And probably 80%+ lower than 1979–haven’t checked those numbers recently.)

    The great majority of ice these days is under 2 meters thick, and often less, IIRC. Extent can stay relatively elevated, but at some point the thickness starts to hit zero across wide swathes, and you can lose a whole lot of ice really fast. And with variability increasing, the odds of a ‘perfect storm’ year start to increase as well. Perhaps that’s why model simulations and statistical analyses increasingly project earlier ice-free minima.

    Here’s a couple of papers from 2019 & 2020 as semi-random examples:

    https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL081393

    …trajectories to an ice‐free Arctic are modulated by concomitant shifts in the Interdecadal Pacific Oscillation (IPO). Trajectories starting in the negative IPO phase become ice‐free 7 years sooner than those starting in the positive IPO phase… The observed IPO began to transition away from its negative phase in the past few years. If this shift continues, our results suggest increased likelihood of accelerated sea‐ice loss over the coming decades, and an increased risk of an ice‐free Arctic within the next 20–30 years.

    https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3513025

    Based on several decades of satellite data, we provide statistical forecasts of Arctic sea ice extent during the rest of this century. The best fitting statistical model indicates that sea ice is diminishing at an increasing rate. By contrast, average projections from the CMIP5 global climate models foresee a gradual slowing of sea ice loss even in high carbon emissions scenarios. Our long-range statistical projections also deliver probability assessments of the timing of an ice-free Arctic. This analysis indicates almost a 60 percent chance of an effectively ice-free Arctic Ocean in the 2030s – much earlier than the average projection from global climate models.

    So, yeah, there’s very definitely support in the literature for possible ice-free minima before mid-century, and maybe well before mid-century.

  41. 41
    nigelj says:

    KM @40, thanks for the links. Looks convincing to me.

    The graph posted by Zebra has data for sea ice area for just the last four decades progressing 6.9, 6.5, 5.5, 4.4. This shows a slight acceleration, but I didn’t think this was quite enough data to say clearly that its accelerated, and the last two decades have been about 1km m2 so pretty linear, so just extrapolating this linear trend gets to ice free by 2060. But the experts say its enough to say its accelerated, and that we are entering a warm phase of the pdo, so I accept we could be ice free by 2030!

    It exposes the fact that Zebras use of data trends and ‘underlying physics’ is again not enough to draw a simple conclusion, because it misses out the historical pdo cycle.

    “By contrast, average projections from the CMIP5 global climate models foresee a gradual slowing of sea ice loss even in high carbon emissions scenarios.”

    Can one of the physics guys explain why modelling has ice loss slowing even in high emissions scenarios? That’s sort of counter intuitive.

  42. 42
    Piotr says:

    zebra (38): “when Notz says “in September”… what does that mean? 30 days “ice free”?

    My guess would be: “anytime in September” (the month when the ice extent is typically at its minimum). More importantly – I don’t think it really MATTERS whether it is “3 months, or 3 weeks, or 3 days” – since most of the impact will be there long before there has been ANY ice-free Arctic – albedo feedback, increased air-sea exchanges, loss of sea ice for ecosystems depending on its presence would realize most of its impact LONG before the ice range shrinks even close to 1mln km2.

    Hence “practically ice-free Arctic” is an arbitrary milestone, primarily for this part of the public and the politicians who cannot wrap their heads around the concept that melting of the Arctic ice can have impact on the global climate and polar ecosystems, and be a proof of climate change, EVEN WITHOUT shrinking all the way to zero.

    And if the ice-free Arctic is not any special tipping point (=0 effect before reaching it, 100% effect after crossing it) – the discussion how exactly we define this point is at best a distraction (along the lines of how many angels can dance on a tip of a needle) and at worst – denial, or supplying ammunition for the denial:
    given that some of the public thinks in term all or nothing, treating the ice-free Arctic as a tipping point between these two – then the more extreme requirements we put to reach this status, the further in time we push the “proof of that global warming is real”. In other words if to be considered “practically ice-free” we demand:
    – zebra: long period (3 months?)
    – Mr KIA, John Pollack: melting sea-ice to ~ 0 (i.e., melting anything that could still sink their boat)
    – Ken Fabian: melting must include the miniscule strip of land-fast ice in the shadow of the coastal topography
    then we DELAY when will reach these conditions for “big warming step” [(c) Ken Fabian].
    Piotr
    PS. The only special thing I can think of as an implication of crossing the point of “ice-free” – is that Arctic won’t have multi-year ice the next year. But even for that you don’t need “3 months, 3 weeks or 3 days” – 3 seconds should be enough … ;-)

  43. 43
    zebra says:

    #42 Piotr,

    Completely agree.

    To me, this is an example of how Tamino characterizes mathturbation, but by supposed anti-Denialists. I’ve tried many times to get them to get past the breathless vague rhetoric and think about what it all means physically… but what fun would that be.

    And, if we do eventually get to my three-month mark, there will be a lot more to worry about globally than the polar bears.

  44. 44

    Hi all,
    Sorry not getting back sooner to those who have replied to my post regarding an Arctic sea ice tipping point. My excuse is I was busy preparing my “display” for the EGU 2020 virtual conference.
    My abstract is here,
    My presentation is here.
    If anyone wants to comment on it or ask a question it can be done here.

    It has nothing to do with sea ice, and I will respond on that topic separately.

  45. 45
    Alastair B. McDonald says:

    The penultimate line of my previous post should have read: If anyone wants to post a comment on it or ask a question that can be done here.

  46. 46
    Alastair B. McDonald says:

    Re #1,

    Zebra,
    Thanks for reposting my question here.

    My definition of an ice-free Arctic is not about when the ice area is less than 1 million square kilometres. It is when there is not enough ice for the ice-albedo effect to take place.

    I have read, but I am not sure where, that for sea ice to form, the air temperature has to drop to -10 C, not -2 C as might be expected. The reason is that if there is any wind when the surface water temperature drops to -2 C it becomes mixed by the wind with the warmer water below.

    Sea ice will form at 2 C in calm conditions, but how often do they occur in the Arctic.

    Sea ice will also grow out from the land which where the surface and wind temperature will be able to drop below -10 C, but the coastal climate will have been changed from continental to maritime by the loss of the ice so how often will that happen?

  47. 47
    Alastair B. McDonald says:

    Re #2,

    Kevin, you provided a link to Serreze (2011) who wrote: “Simulations of twenty-first-century climate suggest that the ice can recover from artificially imposed ice-free summer conditions within a couple of years.” The simulations were carried out by Steffen Tietsche, Dirk Notz, et al. (2011) available here: https://www.researchgate.net/publication/50411329_Recovery_mechanisms_of_Arctic_summer_sea_ice

    They write “The excess oceanic heat that had built up during the ice-free summer is rapidly returned to the atmosphere during the following autumn and winter, and then leaves the Arctic partly through increased longwave emission at the top of the atmosphere and partly through reduced atmospheric heat advection from lower latitudes.” [my emphasis]

    Their reference to the loss of heat at the TOA implies to me that they are using a model based on the Fourier-Arrhenius scheme where heat travels through the atmosphere, rather than the Saussure-Tyndall scheme where greenhouse gases act a blanket keeping the surface warm.

    It is the increase in CO2 which is melting the ice and when it overcomes the ice-albedo effect then we will see the end of Arctic ice.

  48. 48
    Alastair B. McDonald says:

    RE #3,

    John, I agree with you that whether an ice-free arctic is when there is no ice or 1,000,000 square km, is a bit of a slide show. But when it does happen much of the arctic will have been free of ice for much of the summer. So the ocean will be warmer and less likely to refreeze.

  49. 49
    Snape says:

    OT, but last summer I got into a heated argument (pun intended) with the regulars at ATTP regarding the effective radiating level (ERL). They argued that only at that general altitude – the layer of atmosphere centered around 5.5 Km – will an increase in greenhouse gases result in global warming.

    I disagreed, believing that the increase in GHG’s nearer the surface also plays a critical role.

    Consider this hypothetical: what if water vapor and CO2 concentrations at the layer, surface to 2 Km, had remained at pre-industrial levels? Would the warming trend we see today be unchanged?

    Thoughts?

  50. 50
    Alastair B. McDonald says:

    RE #3,

    John, I agree with you that whether an ice-free arctic is when there is no ice or 1,000,000 square km, is a bit of a sideshow. But when it does happen much of the arctic will have been free of ice for much of the summer. So the ocean will be warmer and less likely to refreeze. You seem to be thinking that the lack of ice is only during September. There is also less ice during July and August when there is more solar radiation.

    I had thought that the tipping point would happen when the ice extent fell below a certain level at mid-summer. But which level? Say an extent of 50% of the winter maximum?