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Comments 501 to 550:

  1. 2018 SkS Weekly Climate Change & Global Warming Digest #15


    The header for the first section of Dr Sheperd's article is Global warming is just one part of climate change. All of the ensuing narrative in this section explains this statement in more detail. I see no daylight between your and Dr Sheperd's respective understandings of global warming and climate change.  

  2. Climate Science Denial Explained: Tactics of Denial

    Nights warming faster than days. This is related to greenhouse warming, because of the way the atmospheres layers change at night according to here.

  3. michael sweet at 10:15 AM on 19 April 2018
    Climate Science Denial Explained: Tactics of Denial


    Yes it is true.  The minimum temperature at night has increased more than the hottest temperature during the day.  It has also increased more in winter than in summer (both predicted by Arhennius in 1896).  If the sun increased in heat the summer would warm faster than the winter.

  4. Glacier loss is accelerating because of global warming

    It's projected that 70% of glaciers will be gone from British Columbia by 2100, with about 50% loss in the coast ranges which are wetter and 90% loss in the drier Rockies. Most of the remaining glaciers by that time will be in the North West corner of BC.

     Western Canada to lose 70 per cent of glaciers by 2100

    In 2015 "The Blob" of warmer water in the Pacific off the west coast of Canada helped create condition that saw a significant increase in the rate of melting of some glaciers.

    Glacier melt in B.C. mountains reaches 'shocking' levels

  5. Climate Science Denial Explained: Tactics of Denial

    "if the ocean surface warmed up because less cold deep water were being exchanged with it), then sea surfaces should warm as fast as the land. And if global warming were caused by the sun, days would warm faster than nights; in fact the opposite is true." 

    Is this actually correct? 

    It's easy to test the effect of the sun on diurnal temperature range, becuse we can easily compare summer and winter data, and globally it appeaars that diurnal range decreases in summer - presumably due to increased water vapor from evaporation. In other words, any mechanism that increases earth's surface temperature will result in increased humidity and a reduced diurnal temperature range.       

  6. michael sweet at 08:55 AM on 19 April 2018
    American conservatives are still clueless about the 97% expert climate consensus


    I have posted a new reply to you here where it is on topic.  You should post all your posts on sea level rise on that thread becasue anything here will be permanently lost.  It is site policy to always post on a relevant thread, I am surprised the moderators have not started deleting your off topic posts.

    You should read the comments thread to keep up on all threads like everyone else does.  The comments button is at the top of every page in the middle of the blue line.

    I suggest that everyone try to post sea level rise debate on the relevant thread that Bob Loblaw originally linked and is linked again above.  Both Bob Loblaw's and MA Rodger's posts above are interesting and will be impossible to find in two weeks.

  7. michael sweet at 08:50 AM on 19 April 2018
    Sea level rise predictions are exaggerated


    I mam replying to you from here where you are posting on sea level rise but that is off topic.  I followed Bob Loblaw's link here and found your post on projections of sea level rise.

    It appears that I rembered your post incorrectly.  If you posted here on topic I would have been able to find your old post and would not have wasted my time.  The moderators have warned you multiple times about posting off topic but you cannot be bothered to follow the site rules.  Is that allowed in court?

    Apparently you estimated sea level rise for the rest of the century at 3.2 mm/yr from the IPCC report and not 1.7 mm/yr as I thought.  As the data linked above proves, the rate of sea level has increased substantially since the IPCC report was written so it is no longer relevant.  You must use the current rate which is estimated at between 3.8 mm/yr here by MA Rodger (a 12.5 year average so it is less than the current rate) or 4.1 mm/yr in the linked post from Tamino using Nerem's method.

     Nerem et al. give a minimum amount of sea level rise from 2005 as 65 cm, more than double your guess.  You must provide a reason why you believe that the rate of sea level rise will no longer accelerate when it has been accelerating for the past 130 years.  You should also justify your selection of a rate at least 20% lower than current measurements show.  Remember that expert scientists predict that the acceleration will increase.

    Please post your replies here where they are on topic so that posts are not lost. 

  8. 2018 SkS Weekly Climate Change & Global Warming Digest #15


    My understanding of “part of” is: as an arm is just one part of the human body, inseparable from or integral to it, as opposed to something quite separate and distinct as have tried to explain in my comment – a distinction not clearly made by Dr. Sheperd. Is the term is understood differently in the USA?

  9. The courts are deciding who's to blame for climate change

    william, setting aside 'the whole human race is responsible for climate change', there are clearly some subsets of the human race which are more responsible than others... with those who have profited off it, and used those profits to deceive the public about it, being at the top of the list.

  10. American conservatives are still clueless about the 97% expert climate consensus

    Bob Loblaw @32,

    Of course, the graph you show (linked from another SkS post) is a bit out-of-date now and even the source for the image (which has been provided data to mid-Feb 2018) doesn't use the re-calibrated TOPEX data as in the CU graph below. That graph demonstrates visually an acceleration in global SLR. (And simplistically, if you put a linear regression through the first half of the 25 years of the calibrated SLR data and the second half fo the data, the difference is 3.8-2.8=1mm/yr SLR, this obtained on two halves of the record. These halves being 12½ years apart, it suggests a global SLR acceleration of 0.08mm/yr/yr, or alternatively 2½%/year. Sustained until 2100,  2½%/year would equate to about one metre SLR for the century, a little above the 0.8m 'black dot' on the Rohling graphic @24.)

    CU SLR to early 2018

  11. American conservatives are still clueless about the 97% expert climate consensus

    The GRACE measurements of mass change over the 2010-11 period show very clearly why sea level dropped.

    Article here. keithpickering reported on the sums from the GRACE grids and confirmed most of the change in sealevel accounted for by change in hydrological storage.

  12. American conservatives are still clueless about the 97% expert climate consensus


    You seem to be wanting to continue sea level discussions here, rather than on the Sea level rise predictions are exaggerated thread, where you have not responded to this comment from me.

    The moderators have been snipping from your recent post in this thread. One of the snipped phases was:

    We saw this happen with sea level rise during the "hiatus" and we could see it if temperatures were to level off for the next 10 years. apparent justification for you claiming that a flattening of sea level rise could be caused by a flattening of temperature rise.

    Leaving aside the argument that the "hiatus" in surface temperature rise represented a slowing of global warming (not seen in the ocean temperatures, which are the ones that affect sea level), you are simply wrong that any temporary slowdowns of sea level rise were the result of temperature changes. The primary driver of short-term fluctuations in sea level over the past decade or two is El Nino/La Nina - it shifts water between oceans and land, due to precipitation changes.

    Read this post to see the explanation. Here is the first graph from that post:

    Sea Level

    You are making the wrong conclusions becuase you are looking at the wrong physical mechanisms. Without an understanding of the physical principles that affect sea level, you are doomed to continue these fundamental misunderstandings. I have tried to point this out to you on the other thread, but you are persisting in drawing your own conclusions from a position of ignorance.

  13. The courts are deciding who's to blame for climate change

    Citizenchallenge, yeah the evidence is in the documents. I just didn't want my comment deleted for claiming law breaking before its proven in court, as happened to me on another website recently . No other motive.  

  14. citizenschallenge at 08:15 AM on 18 April 2018
    The courts are deciding who's to blame for climate change

    "Allegedly" is such a worthless word in this context.

    It's all right there in the documents, no "alleged" about it.

    Criminal fraud and denial, and nothing less, is what they did and now we all get to feel the heat for a lazy public drinking their Kool-Aid.

    Although in fairness, we're all co-conspirators, we've know since the 80s, if not 70s (when I learned about it) and even 60s, exactly what we were doing, denial be damned.

    It was easier to look away and enjoy the party, than to listen to fundamental math lessons - look up 'Albert Bartlett.'  Or to care about Earth's interwoven systems beyond the quick profits that could get sucked out of them. So sad.

  15. Climate Science Denial Explained: Tactics of Denial

    Techniques like cherrypicking, red herring arguments and fake experts are obviously trickery to me, however the denialists seem to embrace all this. They must know at some level that its all trickery, or perhaps they come to believe only the cherrypicked element is real, and everything else is fake. They seem to believe agw is some sort of political conspiracy so only sceptical research can be trusted, from commentary I have hear from our local climate denialist media personalities.

    The denialists have created a totally false, but internally self justifying little world detached from reality or having to apply the normal tools of logical analysis.

    The climate science denialists clearly feel strongly about the issue so perhaps logical fallacies are simply treated as tools or a means to an end.
    The denialists are mostly conservative people from various polls, and you clearly see these identities in comments in the media. However not all conservatives are denialists, and not all conservative views are wrong obviously.

    If you listen to media commentary, climate denialists are people who often hate environmentalists. They describe environmentalists as being hippies, academic elitists and communists who want to take away peoples "freedoms" which is of course a very paranoid and distorted picture. You see this in media commentary all the time. Conservatives dont like change and individualism, so this all freaks them out.

    Winning, highest possible profitability, and image is very important to them, and anything that threatens this is seen as the enemy. This is not unique to conservatives, but its very evident that conservatives are most reluctant to embrace any change that could even slightly threaten this. You see it in organisations like The Heartland Institute, The Koch Brothers, and talk back radio.

    So denialism of the science is mostly all about political ideology. Occams Razor.

  16. The courts are deciding who's to blame for climate change

    Exonn and Shell are responsible to the extent they allegedly hid information from the public, and supported deliberate campaigns of denial. The tobacco companies were sued on the same basis. 

  17. The courts are deciding who's to blame for climate change

    Exon is not responsible for climate change, nor is Shell or any of the coal miners.  It is like saying that the drug crisis in the USA and other western countries is due to the drug manufacturers.  The fault is with the consumers; with us.  We could be financing our politicians instead of thinking we are getting away with something clever by letting vested interests pay for them.  We are so wrong.  Who pays the piper calls the tune.

  18. 2018 SkS Weekly Climate Change & Global Warming Digest #15

    Riduuna: Recommend that you carefully reread the entire article . Dr Sheperd is definitely not confused about the terms Global Warming and Climate Change. He adresses the distinction head-on in the first section of his article, Global warming is just one part of climate change.  

  19. The courts are deciding who's to blame for climate change

    Suggested supplemental reading:

    Kids are suing Gov. Rick Scott to force Florida to take action on climate change by Alex Harris, Miami Herald, Apr 16, 2018

    Boulder County expected to join city in climate change lawsuit against fossil fuel producers by Alex Burness, Times-Call, Apr 16, 2018

  20. michael sweet at 22:03 PM on 17 April 2018
    American conservatives are still clueless about the 97% expert climate consensus


    Re-reading the Rohling graph it appears to me that you are using Rohlings numbers from AD 2000 to compare to your numbers from 1700.  Use the scale on the left hand side of the graph and not the right hand side to compare to your 0.4 estimate.

  21. michael sweet at 21:47 PM on 17 April 2018
    American conservatives are still clueless about the 97% expert climate consensus


    Somewhere (I cannot find your old posts because you are posting on sea level rise on mutiple threads) you estimated sea level rise to 2100 would be 10 inches.  You used the long term linear rate from 1900 to 2010 of about 1.7 mm/yr.  The 30 year rate is currently about 3.4 mm/yr or double the rate you used.  The 5 year rate is about 5 mm/year or triple the rate you used. 

    For your projection of 10 inches to realize the rate of sea level rise must immediately decrease by a factor of three and then stay low for 80 years.  If you will not back your estimates you should not make them.  I imagine you got this estimate from some denier like Curry.  Tamino has characterized this method of estimating sea level rise as "complete bullshit".  What web site did you get this estimate from?  Why do you waste your time reading there?

    As for the graph, the point is that 0.4 meters is not the "midpoint" of Rohlings estimates as you claimed.  0.4 meters is the very bottom of the 90% range and is far below the 68% range.  I find graph C easier to read.  Obviously you could not read graph D correctly since you claimed it supported your claim of 0.4 meters as the midpoint.   Examine the larger scale copy of the graph that I linked.  The range of .2-.9m you claimed here is extraordinarily far below the actual range.  The 95% range is actually 0.3-2.2 meters, the 68% range is 0.5-1.2 m.  Arguing about which graph to read is just a distraction from the fact that your claim was false.

    Hansen's point is that the danger of extreme sea level rise is made to counter the low balling by the IPCC on sea level rise.  As time has passed the IPCC has had to substantially raise their estimates while Hansen has remained the same. 

    Hansen's estimates are no longer extreme outliers as they were.  Note his many coauthors and their great experience.  Many scientists who study the great ice sheets talk of meters of sea level rise now.  10 years ago they thought the great ice sheets were stable for thousands of years.  Hansen is very well respected by other scientists (this should be obvious by the number of his coauthors).  You are listening to deniers talking about him.

    2 meters for world sea level rise is a pretty common estimate for the high end (not the extreme possibility) of sea level rise.  Recent data showing the unexpected slowing of the thermohaline circulation in the North Atlantic mean that sea level rise on the East Coast of the USA will be substantially higher than the global rise.  That could be an additional 1.5 feet on top of the 8 feet that the US Climate Change report could not rule out. Even a meter of sea level rise would be trillions of dollars of damage in the US alone.

    You may feel comfortable with no insurance but I think we should take action to prevent such a disasterous possibility. Since action to control climate change will result in tens of thousands of less pollution deaths/yr and save over $50 billion/yr in hospital costs in the US alone, it would be worth it even if sea level rise is "only" a meter.

  22. It's not bad

             First, my interest in agriculture is that, Increased warming may also have a greater effect on countries whose climate is already near or at a temperature limit over which yields reduce or crops fail. Second, Health, warmer climes will encourage migration of disease-bearing insects like mosquitoes. Third, Polar melting, the warming waters increase glacier and Greenland ice cap melt, as well as raising the temperature of Arctic tundra, which then releases methane, a very potent greenhouse gas (methane is also released from the sea-bed, where it is trapped in ice-crystals called clathrates). Next, positive effects of climate change may include greener rainforests and enhanced plant growth in the Amazon, increased vegetation in northern latitudes and possible increases in plankton biomass in some parts of the ocean. Negative responses may include further growth of oxygen poor ocean zones, contamination or exhaustion of fresh water, increased incidence of natural fires, extensive vegetation die-off due to droughts, increased risk of coral extinction, decline in global phytoplankton, changes in migration patterns of birds and animals, changes in seasonal periodicity, disruption to food chains and species loss.

  23. American conservatives are still clueless about the 97% expert climate consensus

    NorrisM, I admit I also thought d was a blow up of c, however take a step back.

    I think the important point is the last IPCC report estimated 0.8 - 1.0 M is the most likely number for sea level rise by 2100,  by calculation, based on business as usual emissions.

    Rohling's research finds 0.8M the most likely number for sea level rise by 2100, by projecting historical data forwards.

    So both are not too far apart, and both rule out 0.4M as low end and unlikely.

    The question is the probability of something like 1.5M or 2M. Neither the Rohling historical research or recent sea level rise modelling rule this out. Rohling explictly states theres evidence of short periods of rapid sea level rise in the past. It may all be less likely, but we just don't know for sure.

    We are loading the dice towards that 2M direction with rapid emissions growth and rates of warming, and evidence that antarctic ice sheets are destabilising, and research recently points towards 2M as a distinct possibility (eg Hanson or Pfeffer). It's like sceptics are taking a gamble that it wouldn't happen, but the results would be truly catastrophic if we are unlucky.

    "Future sea level rise" on wikipedia is a little bit old, but worth a read particularly the key research papers discussed.

  24. Sea level rise predictions are exaggerated

    And funnily enough science does put the error bars on its predictions, However, as has been pointed out, you seem to advocate only on the low bar. Furthermore, action proposed is usually based on middle ground because the upper end of the uncertainty is rather unpleasant. Treating the middle ground as if it was the upper bound is not valid. Since you also tend of over-estimate the consequences of proposed action (shall we count the times since you started posting?), I dont find your position credible.

  25. Sea level rise predictions are exaggerated

    scaddenp @ 74

    I have no idea whether they will err on the low or high side.  Science I think has to acknowledge what it knows and what it does not know and policymakers have to make their decisions based upon the information at hand.

    I appreciate that uncertainty tends to discourage significant action but that does not mean that we cannot ignore the uncertainty as to just what will happen.   It is always easier to take the "high ground" and not take a chance but if the costs and consequences of drastic action were not themselves so uncertain then these changes would have been done long ago.  There is uncertainly every step of the way.  It is easy to say yes AGW is for real but how serious and what do you do about it?

    Sorry, I probably should have stopped after the first paragraph.  

    Moderator Response:

    [DB] Off-topic snipped

  26. American conservatives are still clueless about the 97% expert climate consensus

    michael sweet @ 27

    After looking at this carefully, there is no question that Figure 3 (d) is simply a blown up portion of Figure 3(c).  Just look at where the heavy black dot is on both c and d (the Pfeffer "most likely projection"), in both cases it is .8m.  The heavy black line on both c and d represents Rohling's "probability maximum (peak of probability distribution) which comes out at .4m for 2100.

    I acknowledge that this is simply one "peer-reviewed" paper.  Your criticism before was that I never made reference to "peer-reviewed" literature and should therefore be banned from this website.

    As for the Hansen paper, I have not read it but I will do so.  My understanding of the Hansen paper is that Hansen's 17 foot figure is not a "projection" as you say but merely a "possibility" based upon assumptions for which Hansen himself acknowledges in the paper that he has no evidence.    This last comment was pulled from my recollection of a direct quote from Hansen's paper from some other blogger.  I will see if I can find the quote and if I cannot I will also acknowledge same. 

    Interesting that the US Climate Report, although clearly relying on the De Conto and Pollard 2016 paper on WAIS does not seem to put much reliance on this Hansen paper.   My understanding is that Hansen has had a number of projections which have not come to pass along with a few that have.  I understand that his figure of 17 feet relies on an exponential (not quadratic) curve.  What I do agree with Hansen is his promotion of nuclear power (I have even contributed to his charity because of this).

    I have not suggested that sea level will slow down but if you want an answer to your question as to what physical mechanism could there be for a decrease in the sea level rise rate (not actual decrease), the simple answer is a flattening of the temperature rise.  We saw this happen with sea level rise during the "hiatus" and we could see it if temperatures were to level off for the next 10 years.

    I certainly see that the impact of the WAIS is critical to all of this discussion of sea level.  If anyone could suggest some further reading on what is actually happening to the grounding lines on the WAIS and whether this is creating the seaward flux suggested I would be very keen to read it.  My understanding is that the theory of MISI and his added MICI are still in the "theory" category, not supported by observational evidence.  And it is for that reason that the chances of material change in sea levels by 2100 are rated below 1% for anything more than 2m in the US Climate Report.

    Moderator Response:

    [DB] Sloganeering and off-topic snipped

  27. 2018 SkS Weekly Climate Change & Global Warming Digest #15

    Climate Change or Global Warming?

    Dr Sheperd appears to be confused by the terms Global Warming and Climate Change – which are quite different. One term does not describe the other and should not be used in an attempt to do so.

    Global Warming is a term which describes the causes of and extent to which the planet is warming. The effects of that warming include depletion of land based ice, sea level rise, ocean acidification, thermal expansion, and climate change.

    Climate Change is a term which describes the way in which climate changes. They manifest themselves as measurements of the incidence, duration and intensity of climate events involving precipitation, drought, temperature and wind.

  28. michael sweet at 12:12 PM on 17 April 2018
    Sea level rise predictions are exaggerated

    From Tamino's post:

    [the data shows the sea level rate goes up and down] "Climate deniers hate that. They want you to believe that global sea level has risen at a constant rate for the last 80 years or so at least, so they can deny the danger from even faster sea level rise in the near future. Also, the rate over the last 80 years or so has been less than the rate recently, so by claiming that there’s no “real” change they can make the claim that it isn’t even rising now as fast as it really is rising now. Perhaps the most scientifically accurate description of their approach would be: “total bullshit.”

    I think that is what Tamino thinks of Curries analysis of sea level rise.

    Tamino is an expert statistician who has done a lot of work on sea level rise analysis.  He is especially good at time series analysis (like sea level rise data).

  29. Sea level rise predictions are exaggerated

    Tamino has a new post out on recent sea level changes. It focuses on the US, but has a discussion of why rates vary locally and over time. He is less than charitable on the idea that sea level has been changing at a constant rate - and that extrapolating a linear fit is appropriate.

  30. Climate's changed before

    Bearling, where do you get the idea that mass extinctions are caused by cooling not warming? That doesnt match the published science. The critical thing affecting extinctions is rate of change (because organisms need time to adapt/migrate) not the direction of the swing. Also the Pliestocene ice age cycle is rather slow and not notably associated with extinctions (except where low sea level allowed humans to migrate into new areas where they wiped out the local megafauna), unlike the current rate of change caused largely by our emissions.

    If humans werent around then next peak age would be about 80,000 years. There is more info on this here.

  31. michael sweet at 07:39 AM on 17 April 2018
    American conservatives are still clueless about the 97% expert climate consensus


    The scale is largest around 2100 on graph C so it is the easiest to read.  I note that your estimate of 0.4 m of sea level rise is well below the 68% range, nowhere near a midpoint value.  This paper is used a lot by deniers because it is at the very lowest range of peer reviewed papers.  The IPCC has relied on low papers a lot in the past and increases its projections every report because the low estimates are incorrect.

    This paper by Hansen, Rignot and 17 other top scientists in 2016 (already cited by 196 others!!!) give projections of up to 17 feet of sea level rise by 2100.  They discuss ice sheet disintegration.  I could not immediately find again the paper by Rignot that describes the mechanism of ice sheet disintegration.  He may not be the lead author.  It is cited in the Hansen paper or you could go to his website and look at his list of publications for the years 2014-2016.  The 19 authors of the Hansen paper have much more experience and past successes than Rohling and his coauthors.

    Rignot had a youtube video previously linked for you that described the process.  Search youtube.

    I use GOOGLE or GOOGLE SCHOLAR to find free papers.

    The central, consensus estimate of the IPCC is that humans were responsible for 110% of the warming since 1950.  Your lawerly review of the terms does not appear  to recognise that this is the central, consensus number.  I cannot understand how you discount the central, consensus number.  Gavin Schmitt at RealClimate calculated that there was only a 0.5% chance of humans causing less than 66% of the warming (Curry was unable to do the calculation and said scientists did not know how to either.  She was wrong.)

    The average sea level rise since 1900 is about 1.7 mm/yr according to you (I cannot find your post since it is not on the sea level rise thread).  For the past 30 years sea level rise has been 3.4 mm/yr according to satalite measurements.  Sea level rise must be accelerating since the most recent 30 year rise is double the average over the past century, no analysis is needed. 

    You think sea level rise will immediately slow down to 1.7 mm/yr again??  What is the physical mechanism for the decrease in sea level rise?  Your suggestion of a decline in sea level rise appears unphysical (a very strong term in science) to me.

    Scientists have predicted for over 100 years that sea level rise would accelerate due to AGW and that prediction has come true.  Why could we possibly think that sea level rise will slow down to half of the current rate when peer reviewed papers measure more acceleration?  As temperature increases the forcing for sea level rise increases and we would expect acceleration.

  32. American conservatives are still clueless about the 97% expert climate consensus

    michael sweet @ 24

    Are you saying that graph d is incorrect?  Graph c is hard to read the measurements for 2100.  I understood that Rohling in graph d was simply expanding the size so that you could better read the measurements.

    I have no recollection of any reference by you to a Ringot paper but in any event, could you provide me with some access to the paper? I appreciate that I could search it out but you seem to have url's that can get past paywalls.

  33. 2018 SkS Weekly Climate Change & Global Warming Digest #15

    The IPCC was created in the 80s and it stands for Intergovernmental Panel on Climate Change. That's the name that was already used back then. They pick on any argument they can make up.

  34. Climate's changed before

              Before humans have existed, the big climate changed has happened before and it leads to cause major extinctions naturally. Scientists believe that, over time, changes in the amount of CO2 in the atmosphere have altered the climate of the planet. The proportion of CO2 that is dissolved in the ocean, as opposed to the CO2 that is present in the atmosphere, also varies over time. When more CO2 is trapped in the oceans, the planet cools. By contrast, when atmospheric levels are high, the planet warms. Carbon dioxide is considered to be the most important greenhouse gas involved in global warming. (from
              So after humans have existed, people are putting CO2 more and more into the atmosphere. But cause minor extinctions because climate changes cause major extinctions from cooling not warming.
              If humans are not the factor that causes big climate changes and let the world run naturally, will the next major climate changes be like ice age?

  35. 2018 SkS Weekly Climate Change & Global Warming News Roundup #15

    bozzza @3,

    The two studies that kicked-off this AMOC discussion are Caesar et al (2018) and Thornalley et al (2018). Neither are directly measuring the flow but use either SST data & modelling (there is an illustrative animation of their modelling in this RC post) or proxy paleo-data to infer the past strength of the AMOC. Caeser et al (2018) conclude the AMOC has weakened by around 3 Sv (Sv=milllion cu m/sec). The AMOC is measured today at 17 Sv, so that's a drop of 15%  since the mid-20th century. Thornalley et al also put it as approximately 15% but relative to the preceeding 1,500 years, with their proxy data showing a transition occuring by 1900, that is a big big wobble down that has remained down and not wobbled back up.

    Of course, such findings don't of themselves say a lot but require comparing firstly with what is expected of the AMOC under AGW (IPCC AR5 put it as 1-24% drop by 2100 under RCP2.6 and 12-54% under RCP8.6, all with the 'low confidence' sticker) and secondly what would be the resulting impact on global climate which is a bit of a big ask as it would all be wrapped up with other AGW impacts. As an example, while Hansen et al (2016) present a dramatic scenario with the AMOC switching off, this is the result of other major climatologial change.

  36. 2018 SkS Weekly Climate Change & Global Warming News Roundup #15

    Is there a rate of change measurement at hand?

  37. Sea Level Rise: Some Reason for Hope?

    In this video Dr Grinsted expresses the view that a rise of 1.6°C will be a tipping point for eventual loss of the Greenland Ice Sheet.
    We are already less than 0.2°C below that point and will likely exceed it in less than a decade.

    Dr Ramstorf says that we risk SLR of as much as 2 metres by 2100 but suggests that discharge of cold water from ice sheets may be a mitigating factor, slowing mass loss.
    Rignot, Hansen and others argue that discharge of fresh water on the ocean surface will result in formation of warm bottom water hastening, not slowing polar ice mass loss, particularly in West Antarctica where the ice sheet rests on the seabed.

    Dr Hansen has predicted multi-metre median SLR by 2100 as the likely outcome, driven primarily by the rate of mass loss from the polar ice sheets. If decadal doubling of that rate continues to occur – at present it is accelerating – SLR in excess of 3 metres by 2100 seems a more likely outcome.

  38. Climate Science Denial Explained

    Unfortunately greenhouses (or hot cars) aren't ideal examples of the greenhouse effect, because a greenhouse works in part by trapping air so that it can't rise (and be replaced by cooler air that used to be higher in the atmosphere). The glass of a greenhouses also, incidentally, traps infrared radiation the same way greenhouse gases do, but it's easy for a pseudo-skeptic to point to the lack of convection and say "that's how a greenhouse really works - so the planetary greenhouse effect is a hoax."

    If I catch someone denying the greenhouse effect, I just point out that most contrarian climate scientists (e.g. Roy Spencer, John Christy, Judith Curry) agree that the greenhouse effect exists. More learned pseudo-skeptics have all kinds of other arguments.

  39. Sea level rise predictions are exaggerated

    NorrisM, if you believe that climate models are faulty, then why do you believe they will err low rather than err high?  Surely you dont think government policy should be guided by such biases?

  40. michael sweet at 10:24 AM on 16 April 2018
    Sea level rise predictions are exaggerated

    Free copy of "Testing the robustness of semi-empirical sea level projections",

  41. Sea level rise predictions are exaggerated

    Returning to NorrisM's arguments about the unreliability of sea level rise predictions, in comment #58 and follow-ups. NorrisM has argued that there is uncertainty in the predictions, and closes comment #58 with a justification of using a linear extrapolation with the following sentence:

    "For me, I would go back to the observations and look at where the sea level has moved since 1900 and assume that it will follow along the same largely linear path that it has pretty well followed since we have kept records in tide gauges.

    NorrisM also makes the statement:

    "We cannot base our rational responses to AGW based upon theories which have not been supported with observational evidence.

    Let us examine the uncertainty issue, with particular reference to observations, and whether a linear extrapolation is justified.

    In comment 63, I linked to a RealClimate graph (linked again below) that shows historic sea level estimates from several sources. It is obvious that the different sources provide different curves, which indicates uncertainty even in the historical record. Why is there this uncertainty? Well, observing global sea level isn't as easy or obvious as one might think. We need to do a bit of digging to understand why.

    The RealClimate post linked to earlier about the IPCC Fifth Assessment results  includes a link to another RealClimate post. Both posts include a reference to the following paper (which unfortunately is paywalled):

    S. Rahmstorf, M. Perrette, and M. Vermeer, "Testing the robustness of semi-empirical sea level projections", Climate Dynamics, vol. 39, pp. 861-875, 2011.

    That paper incudes a good summary paragraph (p862) about some of the adjustments that need to be made:

    "The various tide-gauge based global sea-level reconstructions differ with respect to the selection of gauges, the correction for glacial isotatic adjustment (GIA), the correction for changes in atmospheric pressure ("inverse barometer") and. most importantly, the method for aggregating worldwide tide-gauges into a synthetic global mean sea-level curve.

    The Rahmstorf et al paper also gives additional details on methodology. The second RealClimate post linked above talks specifically about the odd Jevrejeva method of weighting the tide-gauge data. I mentioned this in comment 63, quoting from the first RealClimate post. In the second RealClimate link, you can see more about why this method is odd. Note that RealClimate does not just say it's odd, they make the effort to understand the method and do some calculations to understand the impact of the methodology. In that post, they also challenge the readers to find the problem (and they do).

    This is what scientists do when faced with uncertainty: they look in detail at the different sources of information and try to determine why they are different. They don't just throw up their hands and say "I don't know". Uncertainty due to different assumptions and availability of data helps us know what we need to do better, but it does not justify ignoring everything that we do know.

    So, in spite of NorrisM's argument that we should use "observational evidence", he is basing his simple linear extrapolation on data values that represent a significant amount of theoretical understanding, analysis, and interpretation of raw tide-gauge data. So much for his rejection of the danger of sea level rise because it is "theoretical".

    Now, using those global sea level reconstructions is not necessarily bad - indeed, it is a useful exercise. But is it appropriate to use a linear extrapolation? In a word, no. I will repeat the figure that I included in comment 63:

    Real Climate Sea Level Rise graph

    A linear extrapolation would be appropriate if the slope of these curves were approximately linear. They are not. Another RealClimate post  talks about acceleration in sea level rise, and points out that even fitting a quadratic is problematic. Tamino has also posted on this  and includes the following graph that shows how the slope of sea level varies with time:

    Sea Level rise rates

    If sea level rise were linear, the slope would be constant. It is not. If it were quadratic (constant acceleration), the slope versus time would be linear. It is not.

    When deciding to use a particular statistic fit, the first step is to graph the data and see if the preferred equation actually resembles the data. For linear fits, I have always like the illustration given by Anscombe's Quartet. It presents four small data sets that have nearly identical simple descriptive statistics (mean X and Y, standard deviations, linear regression results), but only one of the four is suitable for linearization:

    Anscombes Quartet

    Naive statistical extrapolation of the different global sea level reconstructions is not appropriate. The reconstructions already have "theoretical" knowledge in them, deriving a global value from scattered tide-gauge data. Extrapolating those curves into the future also requires strong theoretical understanding of how the factors that have affected historical sea level will play out in a warming world.

    The scientific literature that provides the basis for the IPCC projections has done this analysis. NorrisM has not.

  42. 2018 SkS Weekly Climate Change & Global Warming News Roundup #15

    This is a telling event and cool story, which seems to have drawn little attention in the media or community given all the competing events.  Anybody that has followed this story for the past decade will have an idea of the potential consequences of a slowdown in the AMOC, and they are significant. The prospects for world seems dismal at this point. I think we're at a low point with lots of competing events drawning our attention.

  43. New research, April 2-8, 2018

    Bilb, I inadvertently deleted a second comment from you this morning while trying to add to a moderation comment in a rush before leaving. The reason your first comment was deleted was because you were posting a gish-gallop of nonsense and long debunked myths, which simply violates the comments policy here.

    However, this obviously impressed you. If you came here to investigate the truth, then pick the argument that you found convincing, use the Search function on the top left to find a suitable topic; read the article; and then tell us why you found your video more compelling than the science. I also suggest you spend some time making your yourself aware of the comments policy at this site. It is designed to encourage meaningful debate about the science rather than flame wars. If you just want to vent at warmists, this is not the site for you.

    Moderator Response:

    [JH] You actually deleted Bilb's third comment. I deleted his second one because it was a moderation complaint. DB deleted his first.

  44. Climate Science Denial Explained

    When someone you know comments that it is hot in his car after it has been sitting in the sun, point out that this is the greenhouse effect and that global warming is happening for a similar reason.  Showing the mathematics behind a gallon of gasoline producing 19.5 pounds of CO2 can get people intrigued.

    People who are not into science do not know the basics,  They have no real reason to.

  45. michael sweet at 08:54 AM on 15 April 2018
    American conservatives are still clueless about the 97% expert climate consensus

    I am sorry, the range of 0.4-1.8 meters is the 90% interval.  The 68% interval is 0.5-1.2 meters.

  46. michael sweet at 08:45 AM on 15 April 2018
    American conservatives are still clueless about the 97% expert climate consensus


    According to the graph in Rohling you must look at graph C and not graph D (the scale is incorrect for the purpose in graph D) source:

    Rohling graph


    I see that in graph C that the 95% range in 2100 is 0.3 m to 2.3 meters.  Your claim that 0.4 meters is midrange appears to be deliberately incorrect.  The 68% range is 0.4 to 1.8 meters, 0.4 meters is the absolute bottom of the range.  Everyone knows that there is much more chance of sea level rise being higher than expected than it being lower.

    Since Rohling was published Ringot has published data showing that Rohlings assumption that the maximum rate of sea level rise would be 2.0 meters/century is incorrect and the actual maximum rate is much higher.  I have given you the reference previously but you ignored it.

    Rohling points out that the current rate is at the very top of the 68% curve or 1.8 meters of sea level rise.   You must provide justification why you think the rate will decrease to less than half the current rate for the rest of the century.   Data shows that the rate is accelerating, not slowing down.

    You are either incapable of reading a graph or deliberately being deceptive.    When you are incapable of reading a simple graph it makes me wonder if you are really capable of calculating expected sea level rise yourself (the answer is no).  People on this website check your references and know when you are misleading them. 

    It is sloganeering to repeatedly give incorrect information.  You are very well informed about the low end of the data but seem completely ignorant of the upper end. You are misdefining the IPCC information.

  47. 2018 SkS Weekly Climate Change & Global Warming News Roundup #15

    The weakening of the Gulf stream / AMOC is a very concerning development. However some people probably won't be worried, because they simply can't seem to compute that small global temperature changes over time can have severe impacts like this that could reshape climate systems. You see evidence of this in blog commentary.

    Perhaps they see large swings of temperature seasonally or diurnally that don't cause problems, and reason form there. Remember Senator Inhofe dumping a snowball on the floor, and proclaiming "theres no global warming" in either an astonishing display of ignorance, or cynical and deliberate avoidance of the issue.

    One thing blocking awareness of the severity climate problem is therefore possibly psychological perception of this sort, as well as political ideologies, and vested interests. They probably mutually reinforce each other. I can't think of many other issues in society with so many things blocking understanding and action.

    Perhaps if humanity could just focus on a sustainable future and set of related values this would help.

    The gulf stream and AMOC is really part of the global thermohaline circulation system as follows.

  48. American conservatives are still clueless about the 97% expert climate consensus

    nigelj @ 20

    "I don't see how you can get from high confidence in 100% human attribution of warming, to a medium consensus." 

    Nigel, how I get from "high confidence" to "medium consensus" is that this is exactly what the term "High Confidence" means when used by the IPCC and the US Climate Report.  I think this term is rather misleading but here is the definition of "High Confidence" right out of the US Climate Report (see my long sea level rise post where I listed these definitions):

    "High Confidence means moderate evidence (some sources, some consistency) medium consensus."

    As for Rohling's midpoint estimate for 2100 of a .4M rise since 1700, please refer to Figure 3(d) in the paper which shows a range for 2100 of .2M to .9M with .4M as the mid range value.   I think Rohling's reference to .8M is stating that it is near the upper bound of his 68% probability interval of natural change.  

    Rohling makes it clear that his projections following LIg values (previous interglacial) are based upon extrapolation of "well-constrained processes for Greenland" and that "proportionally greater contributions might be possible for Antarctica".

    You asked me why I am always at the low estimates.  My underlying reason for looking at the lower end is my underlying distrust of whether the GCMs are accurately predicting the amount of temperature rise we will actually have from now until 2100 and therefore the impact it will have on sea level rise both from a thermal steric standpoint as well as a mass increase from melting ice sheets.  It comes from a general philosophical view that Hume is right that as soon as we move from empirical analysis we get into dangerous waters. 

    I know this is not the place to get into a discussion of GCMs but you asked me why I am always on the low end.  I have a general distrust of the ability of the GCMs to replicate our complicated climate system especially with the admitted problems with properly inputting the impacts of clouds owing  to a combination of not fully understanding their impact and not having the computing power to build them into the models.   You then add to this serious questions as to whether RCP 8.5 is a realistic scenario given the move to alternative sources of energy in the world.  I think China has realized that it cannot continue to use coal in an unlimited manner.  

    PS Presently reading a book which somewhat explains the "Age of Trump" by Kurt Andersen titled "Fantasyland - How America Went Haywire".  It is a 400 year history of "delusion and make-believe in the US" since the first settlement of Jamestown, Virginia. 

    Moderator Response:

    [DB] Off-topic snipped.  I'd warn you about the repercussions for such continued violations of this venue's Comments Policy, but I know you'd just continue to ignore such.

  49. They changed the name from 'global warming' to 'climate change'

    Recommended supplental reading:

    Climate Change Or Global Warming? Three Reasons Not To Be Distracted By The Name Game by Marshall Sheperd, Science, Forbes, Apr 13, 2018

  50. American conservatives are still clueless about the 97% expert climate consensus

    NorrisM @19 , allow me to unruffle your feathers.  Yes, I was making a cheap shot in suggesting your posting activity outweighed your breadth of non-partisan reading.   I am half-ashamed of my rudeness in attempting a witticism, there.

    Still, you yourself know how strenuous is your advocacy for minimizing the appreciation of the adverse effects of AGW (and especially, regarding sea level rise).   You appear to lean towards the cherrypicking of any studies/opinions hovering at the extreme-low end of the likely range of MSL rise for the next 80 years.

    I won't insult you by quoting others who pointed out the need for prudent risk-management wrt AGW and MSL rise.

    Yes, reading the [2013] 5th IPCC's Summary For Policymakers . . . is educational, but we must recognize that the whole IPCC output is toned down towards the "Lowest Common Denominator" (both in politically-acceptable terms and in terms of defending a smaller scientific position).   And it is footling to attempt to "reverse engineer" a realistic scientific risk-assessment by shuffling phrases such a ">66%" , "highly likely" , "moderate confidence" , and so on.

    Hence the unwisdom of viewing the real world entirely through a prism which (a) is 5 years out of date, and (b) is inherently tilted towards undue emphasis on The Least.   (Of course, the IPCC reports are still a goldmine of information & references.)

    Already (since 2013) we have seen the spectacular end of the "Hiatus" in surface temperatures, and we have seen evidence that ice-melt is occurring faster than previously thought.   And we are only at the beginning of that 80-year period to Century's end !     Nor should we turn a blind eye to the much larger effects to come, in the centuries beyond 2100.

    NorrisM, you are being irresponsible in wasting your time pointing at the "[merely midpoint] 0.4 by 2100" scenario (one of many scenarios based on information prior to 2013).    Less partisanship and more prudence, please !

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