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Comments 19501 to 19550:

19501. Tom Curtis at 09:20 AM on 26 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       nigelj @33, if you mean one of the graphs from this page by Tamino, then the Church and White data is actually from 1800-2009 (ie, the original data from the paper without updating), or from 1930 for the last three graphs.  Of the graphs there, this one seems to best fit your description:

       

       You will notice that though the data is noisy, the slope of the smoothed curve over the initial decades is less than that over the final decades, a fact that indicates acceleration.

       Better yet is this graph, which determines acceleration on the assumption of a parabolic fit from each date up to 1990, showing uncertainty intervals:

       

       The initial and 1900 values plus uncertainty intervals are close to those stated by Church and White, suggesting that is the technique they used.  Tamino goes on to use better techniques to understand the structure of the acceleration, but only with the data from 1930.

       For what it is worth, using a linear fit on the annual differences in sea level, the OLS trend is 0.006 +/- 0.019 mm/yr².  That is, it shows acceleration, but it is not statistically significant.  For comparison, using the same technique on the data to 2009 shows an OLS trend of 0.018 +/- 0.016 mm/yr²; while from 1900 to 2014 shows an OLS trend of 0.019 +/- 0.015 mm/yr².  All errors are for 1 standard error only, so none of the accelerations shown are statistically significant, though all are greater than that reported by Church and White.  Because of the accelerations shown, it is more likely than not that using the better techniques used by Church and White, and by Tamino in his last figure, would also show acceleration over that interval.  Because of the larger relative errors, that is not certain, and it is certainly not clear that the data to 1990 would show a statistically significant acceleration, even using those better techniques.

19502. nigelj at 08:37 AM on 26 May 2017
       NCSE's counter-Heartland flyers
       

       If this sort of climate nonsense and deceit is allowed into schools, where does it stop? Next anti vaccination and anti flouride rubbish will be allowed in. Children will become missinformed, and at the very least totally confused.

       I'm a strong believer in freedom of speech and rights of lobby groups, as far as the adult world goes, but I feel children have to be protected from rubbish from lobby groups, as they are not in a position to discern good from bad, or misleading information. Free speech is a right, but comes with a few responsibilities, and limits in some cases.

19503. nigelj at 08:18 AM on 26 May 2017
       Global climate projections help civil engineers plan
       

       "While people in the halls of Congress or in homes at holiday time may still argue about whether climate change is happening, scientists and engineers now have enough information to make informed decisions."

       Yes exactly right. But one point, buildings and other civil works are mostly designed to building codes, which are ultimately political decisions! And many politicians are climate sceptics or are captive to lobby groups who are sceptics. In fact where I live politicians have not changed building codes, and have basically said it's up to the buyer and builders to do as they wish in terms of climate change. I think this is a totally inadequate political response.

       It's possible of course to design above code, but this is just not always going to happen. This is human nature. As a result many people will go on building in vulnerable areas, and in silly ways, and this will ultimately become a burden on society as a whole.

       You have to improve building codes and civil engineering codes, and make it mandatory. You may have to put some land off limits for development as well, if it's very vulnerable.

19504. nigelj at 07:23 AM on 26 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Tom Curtis @31, thanks for making sense of this mystery. It appears to me Joe had the right method, but the wrong assumption on data previous to 1990, which is maybe understandable, as it wasn't so clear.

       This graph is based on Church and White with the satellite data stiched on, from 1880 to 2016.  

       I can't see any increase in the "rate of the rate" from 1900 - 1990. It looks flat overall, but has a convex hump. There's an obvious increase in the rate of the rate from 1990 onwards. 

19505. MA Rodger at 23:59 PM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Tom Curtis @31,

       I agree that the interpretation of the Smithsonian quote I present @30 is ludicrous and should be interpreted as you set out. Yet the interpretation @30 does after a fashion yield the values presented by joe@12. Despite being shown the need for a proper explanation, joe says no more than "I am going to refer you back to the the citation from the smithstonian. The rate of growth was straight from the data provided which is also from NOAA."Of course there is nothing preventing joe properly explaining how he derived his values if my explanation of it is wrong.

19506. Tom Curtis at 19:29 PM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       MA Rodger @30, comparison of the Smithsonian's claims to both Church and White (2011) and Jevrejeva et al (2014) data suggests the Smithsonian is basing its claims on Church and White for the interval preceding the satellite data, and the satellite data thereafter.  That conclusion is given circumstantial support by the fact that one of the author's, Joshua Willis, works for NASA, whose vital signs page uses just that combination of data.

       In any event, I interpret the Smithsonian quote as saying, not that sea level rose at a rate of 1.2 millimeters per year in 1900 and 1.7 millimeters per year in 1990, but that the linear trend from 1900-1990, given uncertaintly, lies between 1.2 and 1.7 millimeters a year.  In support of that, using the linest function on the Church and White data from 1900-1990 yields a linear trend of 1.5 +/- 0.3 mm/year.  I would conclude that no estimate of acceleration from 1900-1990 can be made from the Smithsonian statement, and certainly not one in contradiction of Church and White itself. 

       Nor can the difference between the 1.7 mm/year upper bound on the uncertainty interval fo the 1900-1990 trend be used to calculate a rate of acceleration from 1990-2000.  That is especially the case given that the second part of the Smithsonian statement appears to be based on the satellite data, and therefore is not directly comparable.

       For what it is worth, the linest estimated OLS trend for 1991-2000 is 2.16 +/- 0.4 mm/year.  From 2000-2014 it is 4.0 +/-0.2 mm/year.  Again, that shows a noticable acceleration.

       Of course, Joe may have been relying on a different data source, in which case this analysis is irrelevant to his claims.

       (Note: all calculated error margins given for 1 standard error.)

19507. MA Rodger at 17:03 PM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Tom Curtis @28,

       Concerning your first question posed, I suspect that the values presented thus by joe@12 :-

       "Based on the data in the aforementioned article, the rate of increase in the rate of sea level rise was appox .0036 per annum (0.36% ) from 1900 to 1990. The rate of the increase in the sea level rise from 1990 to 2000 was approx .061 per annum (6.1%). The rate from 2000 to 2016 reverted back to .0040 (0.4%). which is much closer to the historical norm."

       - were calculated from the rates of SLR described in the second pragraph of the Smithsonian Ocean ortal SLR page linked @12:-

       "Between 1900 and 1990 studies show that sea level rose between 1.2 millimeters and 1.7 millimeters per year on average. By 2000, that rate had increased to about 3.2 millimeters per year and the rate in 2016 is estimated at 3.4 millimeters per year. Sea level is expected to rise even more quickly by the end of the century."

       (Note the 3.4mm/yr 2016 figure is also given as 3.7mm/yr further down the Smithsonian article.) If this Smithsonian quote is interpreted as stating that the SLR 1900 was 1.2mm/yr, 1990 1.7mm/yr, 2000 3.2mm/yr and 2016 3.4mm/yr and an average percentage for the acceleration of SLR then calculated, you obtain 1900-1990 - 0.35%/yr (assuming a full century and not 90 years), 1900-2000 - 0.71% over 10  years, 2000-16 - 0.4% over 15 years. This is a bit of a stretch but is not a million miles from the values presented @12.

       The "NOAA" data mentioned @21 (and also "smithstonian/NOAA data" @23) I suspect is the Church & White data you suggest @28. A plot of the exponential increase using the 'joe' values will slice through the wobbles of the Church & White data up to the 1990s. However, it is evident that the 'up' wobbles are larger than the 'down' wobbles which is why the 20th Century SLR is greatly underestimated by the assumed exponential growth.

19508. bozzza at 12:45 PM on 25 May 2017
       Trump's Fox News deputy national security adviser fooled him with climate fake news
       

       I love the graphic illustrating denier staganation: the world is turning and the rest is just all pause-button-politics as Jevons Paradox pays the taxes.

        

       The people lead: Governments follow! (Can you believe Arnold Schwarzenegger said that? That's how basic this conundrum is!!)

19509. John Hartz at 12:36 PM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       We all need to keep in mind that Sea Level Rise does not occur uniformily throughout the global ocean system. Cases in point...

       A 2016 Rutgers study found that seas near New Jersey could rise between 1 and 1.8 feet by the middle of this century under a scenario of low carbon emissions. But under a high emissions scenario, seas could swell as high as 4.5 feet by 2100. Recently, a National Oceanic and Atmospheric Administration study estimated mean global sea levels could rise as high as 8 feet by the end of the century.  

       Another study by researchers at the real estate firm Zillow found that nearly two million U.S.homes worth almost $900 billion could be underwater by 2100. The researchers weren’t referring to a situation where the market value of a home dips below the value of the mortgage; they literally meant underwater, swamped by rising sea levels.

       Zillow researchers looked at coastal states where sea levels would rise by six feet by 2100. In Florida, the most vulnerable and heavily developed, they found nearly 1 million homes – one of every eight in the state – would be underwater. The next most vulnerable state was New Jersey, where 190,429 houses would be inundated.

       How Rising Seas and Coastal Storms Drowned the U.S. Flood Insurance Program by Gibert M Gaul, Yale Environment 360, May 23, 2017

19510. Tom Curtis at 11:07 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Joe, using Church and White (2011) (data downloadable here) as a basis of discussion, they claim that:

       "The linear trend from 1900 to 2009 is 1.7 ± 0.2 mm year−1 and since 1961 is 1.9 ± 0.4 mm year−1. There is considerable variability in the rate of rise during the twentieth century but there has been a statistically significant acceleration since 1880 and 1900 of 0.009 ± 0.003 mm year−2 and 0.009 ± 0.004 mm year−2, respectively."

       0.009/1.7 =0.0053, or 0.53% increase per annum in the rate of sea level rise (2nd derivative) over the course of the 20th century.  More importantly, that rate of increase extended over the period 1900-2009 would result in a rate of increase of sea level (first derivative)  2.27 mm/year in 2009.  The actual rate of increase of sea level for the decade terminating in 2009 was 3.41 mm per annum.  What is more, by 2014, the rate of increase for the preceding decade had risen to 4.53 mm/yr.  There is a relatively smooth rise in rate of sea level rise over a decade from 2000 to 2014 of 0.17 mm/yr^2, which is approximately a rate of increase in the rate of increase of sea level of 5% per annum.

       This raises two questions:

       Given that your estimates of the rate of increase of the rate of increase of sea level are under estimates whether we take the 20th century values, or the more recent much more rapid rate of increase, where did you get those estimates from (or how did you make them)?

       Given that the rapid rate of increase in sea level rise coincides with the onset of rapid loss of ice from the Greenland and West Antarctic Ice Sheets, is there any reason we should not expect it to continue, and therefore project a 14 year doubling time of the rate of sea level rise over at least the first half of the 21st century?

19511. Bob Loblaw at 10:49 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Oh, and Michael's link in #22 is the same Tamino post I linked to in #5....

19512. Bob Loblaw at 10:48 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Michael, Joe, et al:

       I think there has been some cross-talk. Joe's use of the phrase "rate of increase" can be hard to follow.

       • the value has increased by 1% over a period of time

       and

       • the rate at which the value is rising has increased by 1% over time

       ...do have rather different meanings, as "the rate" already talks about an increase. So "the rate has increased" means that the new rate is higher than the old rate.

       To delve into what a former student of mine once called "all that math $#!^":

       • the rate of increase would be the slope (known as the first derivative with respect to time, to the math geeks), and  linear thinking.
       • the rate at which the increase is increasing would be the acceleration (known as the second derivative to the math geeks), and is a non-linear relationship.

       I think Joe has used the second meaning, and Michael admits to having been thinking the first.

       ...unless Joe really means "change in acceleration" as Michael says above, which is the rate at which the change in rate has been changing...  or the third derivative. (Yes, I am being obtuse on purpose.)

       So, can people try to be a bit clearer with the terms they use, please? I suggest:

       1. "rate of sea level rise" is the slope over a period, e.g., in mm per year.
       2. "acceleration in sea level rise" is a change in the rate of sea level rise, and could be a % of the current rate, or in absolute terms (e.g., mm/yr/yr).
       3. If we really want to talk about acceleration changing, then come up with some easier way to express it than "the third derivative",

       ...Boy, its hard to work a simple analogy without getting into the weeds, isn't it?

19513. michael sweet at 08:48 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Joe,

       I did not realize that you were estimating the change in acceleration.  Tamino's graph may be leveling out but the error bars are wide.  The smooth used is more error prone at the ends.  We will know more in 5 years.

       I would like to withdraw from this conversation to prevent dog piling.

19514. MA Rodger at 08:41 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Hey joe @21.

       I find it strange you do not see the problem. I say 0.35%/yr doubles in 200 years. You say 0.36% doubles in 192 years, essentially the same finding. And you insist "The historical norm has been a rate of 0.36% to 0.4% increase for the SLR."

       Yet the SLR data over the last century or so (a significantly shorter period) shows far more than a doubling in the rate of SLR.

       Now we can add to these contradictory positions that you occupy because you tell us that when you "plugged the numbers into the spreadsheet for each year since 1870, virtually each year agrees with the data from NOAA." Yet when I set your values for SLR increase (1880-1990 0.35%/yr, 1991-2000 0.61%/yr, 2001-2013 0.4%/yr) into a spreadsheet alongside Church & White data (1880 to 2013), the inter-annual SLR variations prevent any checks on an annual basis and the longer-term accelerations in SLR do not match your values, virtually or otherwise.

19515. joe - at 08:16 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Michael Sweet - "Today, global sea level is 5-8 inches (13-20 cm) higher on average than it was in 1900. Between 1900 and 2000, global sea level rose between 0.05 inches (1.2 millimeters) and 0.07 inches (1.7 millimeters) per year on average. In the 1990s, that rate jumped to around 3.2 millimeters per year. In 2016 the rate was estimated to be 3.7 millimeters per year, and it is expected to jump higher by the end of the century."

       That quote is consistent with my statement and the math.  The Smithstonian artcle, the Church white chart is likewise consistent.  

       This graph clearly shows that sea level rise has not decelerated since 2000. Tamino claims that the rise is accelerating. His graph shows a rate of approximately 3.0 mm/yr in 2000 increasing to 3.5 mm/yr in 2015. There is a wide error bar but the rate cannot be claimed to be decreasing.

       A change from 3.0 in 2000 to 3.5 in 2015 is 1.03% (based on the Tamino) vs the 6.1% rate from 1990 to 2000. This difference of 1.03% from Tamino's data and the 0.4% based on the smithstonian/NOAA data is well within the error bar.  

       It should be noted that everal comments later and only one person has crossed checked the math.

       After adjusting from 

19516. michael sweet at 07:45 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Joe:

       In your citation in the Smithsonian it says:

       "Today, global sea level is 5-8 inches (13-20 cm) higher on average than it was in 1900. Between 1900 and 2000, global sea level rose between 0.05 inches (1.2 millimeters) and 0.07 inches (1.7 millimeters) per year on average. In the 1990s, that rate jumped to around 3.2 millimeters per year. In 2016 the rate was estimated to be 3.7 millimeters per year, and it is expected to jump higher by the end of the century."

       I think this quotation contradicts your claims.  Please quote from the paper to support your claims.  It appears to me that you have misread your source of data.

       This blog from Tamino analyzes the recent sea level rise.  Here is a key graph:

       

       This graph clearly shows that sea level rise has not decelerated since 2000.  Tamino claims that the rise is accelerating.  His graph shows a rate of approximately 3.0 mm/yr in 2000 increasing to 3.5 mm/yr in 2015.  There is a wide error bar but the rate cannot be claimed to be decreasing.

19517. joe - at 07:33 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       MA Rodgers - Following up on your comment - It appears from the follow up comments that you were the only one who attempted to check the math which I appreciate.  (simple excel calculation) and yes, 0.36% is a doubling in approx 200 years.  (or approx 192 years) Again I appreciate someone actually reviewing the math.

       The historical norm has been a rate of 0.36% to 0.4% increase for the SLR.  When I plugged the numbers into the spreadsheet for each year since 1870, virtually each year agrees with the data from NOAA.  With the exception of the years 1990-2000 when the rate of increase jumped for those ten years to 6.1%. Which then reverted back to 0.4% annual increase.  

       With regard to J Hartz comment, The data is through 2015.  The study John cites is from data through early 2016 (published 2017).  I doubt the rate of increase jumped that significantly in 18 months.  Further The actual study is behind a paywall, though based on the data from NOAA, the headline from the WP is more than a little misleading.  The largest increase in the rate of sea level rise occurred during the change in the method of measurement.  (I will add that I have not had the time to confirm if the large increase was due to the change in the methodology of measurement, only that all other years were well within the historical norm.  

19518. joe - at 07:08 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       MA Rodger - Hey joe @12.

       I think your calculations of SLR acceleration need some explanation here. An annual 0.35% increase in the rate of SLR would result in a doubling in the rate every 200 years. With 1900 SLR not much greater than 1mm/yr, how is it we see already SLR well above 3mm/yr, a trebling after a single century (and that before adjustment for terrestrial storeage and aquifer depletion which is calculated to have reduced SLR)? While you do also calculate higher values in recent decades (the 0.61% increase for the 1990s and the 0.4% since 2000), these do not even start to explain all the SLR being measured today.

       I am going to refer you back to the the citation from the smithstonian.  The rate of growth was straight from the data provided which is also from NOAA.  The anomoly in the data was from 1990 to 2000 which had the 6.1% growth in the rate of increase.  Using the NOAA data and the data from the citation, the rate of increase after 2000 reverts back to the norm of 0.4%.  

19519. MA Rodger at 06:54 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Hey joe @12.

       I think your calculations of SLR acceleration need some explanation here. An annual 0.35% increase in the rate of SLR would result in a doubling in the rate every 200 years. With 1900 SLR not much greater than 1mm/yr, how is it we see already SLR well above 3mm/yr, a trebling after a single century (and that before adjustment for terrestrial storeage and aquifer depletion which is calculated to have reduced SLR)? While you do also calculate higher values in recent decades (the 0.61% increase for the 1990s and the 0.4% since 2000), these do not even start to explain all the SLR being measured today.

19520. nigelj at 06:50 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Joe @14, "That rate of increase in the rate of sea level rise has been in the 0.3-0.4% range which is a far cry from the IPCC estimate of 2.3%"

       Yes but so what? Some past rate of change does not have to continue forever. The IPCC look at physical processes going forwards. For one example, they are confident positive feedbacks etc will increase the rate of ice melt especially around mid century so they think things will accelerate.

       The following is a  graph of sea level rise for NZ, over the past century and combined with standard IPCC predictions going forwards. The transition from past trends to the predicted larger acceleration is reasonably smooth, so entirely plausible. 

19521. Evan at 06:47 AM on 25 May 2017
       SkS Analogy 4 - Ocean Time Lag
       

       Thanks for the input Tom.

       I would argue that the difference between 2.85 and 3.0 is minor. You and I are fairly well educated on these matters so I can follow you arguments (I model particle formation in chemical reactors), but the analogies are mostly written for people who have never thought about the effect of the oceans. The time lag of 20, 30, or more years includes many more complex physics, as you point out, but the salient point is that there is a decadal-scale time lag between what we do and when when see the effect, and for my intented audience, that is already news.

       But thank you very much for the additional information you provided.

19522. KR at 06:01 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       William - CO2 forcing goes up with the log of the concentration,  but since CO2 are actually increasing faster than exponentially the forcing is rising faster than linearly. 

       Taking the Keeling CO2 data yearly averages and running the log of them gives the forcing curve (easy to do in Excel). A linear forcing would show as a straight line,  but the log data shows a rising curve,  demonstrating that CO2 is increasing more than exponentially. 

19523. John Hartz at 05:30 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Joe: The research described in this article suggests that your computations and conclusions are dated...

       A new scientific analysis finds that the Earth’s oceans are rising nearly three times as rapidly as they were throughout most of the 20th century, one of the strongest indications yet that a much feared trend of not just sea level rise, but its acceleration, is now underway.

       “We have a much stronger acceleration in sea level rise than formerly thought,” said Sönke Dangendorf, a researcher with the University of Siegen in Germany who led the study along with scientists at institutions in Spain, France, Norway and the Netherlands.

       Their paper, just out in the Proceedings of the National Academy of Sciences, isn’t the first to find that the rate of rising seas is itself increasing — but it finds a bigger rate of increase than in past studies. The new paper concludes that before 1990, oceans were rising at about 1.1 millimeters per year, or just 0.43 inches per decade. From 1993 through 2012, though, it finds that they rose at 3.1 millimeters per year, or 1.22 inches per decade.

       Scientists say the pace of sea level rise has nearly tripled since 1990 by Chris Mooney, Energy & Environment, Washington Post, May 22, 2017  

19524. william5331 at 05:21 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       It is worth pointing out that the curve for warming vs Atmospheric Carbon dioxide is  downward curving.  The climate sensitivity theory says that for each doubling of CO2 we have a temperature increase of, say, 3.5 degrees C.  So if we go from 200 to 400ppm this increases the temperature by 3.5 degrees but we have to go from 400 to 800 to get the next 3.5 degree rise.  Of course, this ignores tipping points such as what happens when the Arctic is mostly ice free for a significant part of the summer.

19525. joe - at 04:56 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       The only real question is how fast the rate of sea-level rise will increase (i.e., what will be the doubling time).

       Based on the math, the rate of increase has been fairly constant. (other than the anomoly during the 1990-2000 time frame which is pointed out in the article - though you have to actually run the math to notice).  That rate of increase in the rate of sea level rise has been in the 0.3-0.4% range which is a far cry from the IPCC estimate of 2.3% 

19526. Evan at 03:18 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Thanks for the reference Joe and for your comments.

       It is likely dangerous to rely too much on historical trends. We know that we are warming the planet faster than at any time in the known paleo record, and we also know that ice melts as it warms. We also know from measurements that the melt from Greenland and Antarctica are speeding up, and this is why doubling times for galcier melt is used to estimate future sea level rise. Even if there was an anomaly in the 1990's or even if there was a change in measurement method, it does not change the basic math that there is over 200' of sea-level rise in ice worldwide, and that the rate of ice melt increases as Earth warms. The only real question is how fast the rate of sea-level rise will increase (i.e., what will be the doubling time). There is likely nothing in the records for the last 100 years that can be used to make good projections into the future, because up to now the big glaciers have contributed little: sea-level rise has so far been controlled mostly by thermal expansion.

19527. sauerj at 02:49 AM on 25 May 2017
       Citizens’ Climate Lobby - Pushing for a price on carbon globally
       

       Larry E: Thanks for your kind reply. You write well & have thought thru your points; and are definitely passionate on reducing carbon emissions (we are on the same side on that front). We just differ on what we think are effective & politically obtainable/durable ways to get there.

       CCL & others have worked the numbers on the demographic "bins" (I like your word here). I purposely simplified this so to be brief. Yes, per CCL reported studies, 70% of the population consumes avg FF per capita or less. And, 85% of the poorest bin would come out net positive on div-fee. Yes, my avg cost fee & dividend #'s were simplified, but on purpose so to be brief & only give the ballpark norm, for general talking purposes, on the near-avg (close enough) increase in fees & dividend. Certainly the % increase in power & nat-gas costs, that I gave, are right on (in terms of $/kwh or $/dth, those are easy to calculate, which I have done & verified); and I think these are substantial to the avg pocketbook so to influence market choices (they would be for me, and so, I don't see why not for many others).

       Would buying choices & habits change? I strongly think so. Would I put that $7200 to use to reduce the $7200 increase in costs? Yes, and I think that would be the norm. Actually 50-70% of that increase would be in home/car utilities; the other 30-50% would be increases in costs packed into everything else. Would people forego this or that product or service because now its cost was more than other lower cost options (due to lower C footprint); I think so. After all, that is how we make our choices now. But, for industry, I know that the impact will be immense because I am intimately immersed in what drives its inner workings. And, these changes would cause significant C reductions (this would be real), and increased price signals would trickle-down to impact market choices to the public.

       I like your choice of words for the 'soft landing'. Yes, the policy does ramp-up the artificial price (to include the external cost of CC) so to give the economy time to adjust (i.e. a 'soft landing'), but too sharp (too fast a ramp-up) or too regressive (little or no dividend) and it won't politically survive (the Brookings podcast says this is partly to blame for the reversal of the recent Australia policy). As I said, there is nothing to stop going higher than $100/ton (don't discount this conceptual strategy simply based on a tactically hard set #), and, as you wisely uncovered, it would be smart if the ramp-up rate also included additional cost to account for inflation. That makes total sense!

       Political obtainability: I live in a state (IN) where getting any sort of macro policy (even one that would be amiable to the GOP; i.e. the revenue-neutral variety) enacted has, at most, only about a 5-10% chance of any gaining political support, which only happens by building enough "political will" so to sway government policies (I judge this by how few people actually "walk the talk"; out of the few genuinely concerned "talkers" there are very few policically engaged "walkers"). And, I even live in a progressive town in this state. AGW simply is not toxic enough nor is its 'causal & effect' connection obvious enough on its own (at least, in the next 10-20 years) to cause the required self-regulating forces in society to bring about the large scale changes that are required (unlike other forms of pollution). So, political durability has been and still continues to be real issue to contend with that can not be dismissed if we hope to achieve real carbon reductions. ... If the political support for RNCFD (rev-neu CFD) is already weak, then its going to almost non-existent for a cap-only policy, especially after the follow-up substantial regressive impacts come to bear (I think case histories demonstrate).

       Lastly, if I wanted to help support a cap-only policy, where would I go to help build support? Is there any organized groups that are advocating such a policy so to rally behind? Are there any active lobby groups, or grass-root or grass-top groups that are building coalition for this? Are there any studies to describe its follow-up economic & political impact? ... What gives you a personal sense of confidence that a cap-only policy would practically have any political "legs" both in the now & after implementation? ... If the answers to these questions are mostly in the realm of ideals and has little to no developed organized coalition, then I can't get past the lack of its tangible political practicality to commit myself to advocate 24/7 for it. ... For me the logic of RNCFD (rev-neu CFD) is straight foward. It "thinks" & "works" like an engineer; it has a logical power to it. Therefore, I believe it will be effective (if $100/ton isn't enough, then increase it; think of it in terms of its conceptual strategy). And, most importantly, I believe it is politically tangible and durable, which is a point to absolutely contend with in the US.

       I know none of this will change your mind. But, I do enjoy the kind dialogue we have had. We both must fight on (there are driven by no other choice), working toward the same goal, but just on two different fronts. Have a good day!

19528. joe - at 02:48 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       http://ocean.si.edu/sea-level-rise

       Based on the data in the aforementioned article, the rate of increase in the rate of sea level rise was appox .0036 per annum (0.36% ) from 1900 to 1990.  The rate of the increase in the sea level rise from 1990 to 2000 was approx .061 per annum (6.1%).  The rate from 2000 to 2016 reverted back to .0040 (0.4%). which is much closer to the historical norm.

       The large rate of increase from 1990 to 2000 would seem to be connected to the change in method of measurement.  Other than the anamoly for the short ten year period, it would seem very unlikely  that the rate of increase will suddenly shift upward from less than 1% per year upwards of 6-10% as speculated in the  article or even the 2.3% projected by the IPCC in their 5th assessment.

19529. MA Rodger at 00:57 AM on 25 May 2017
       2017 SkS Weekly Climate Change & Global Warming News Roundup #20
       

       In the discourse above, the paper Haile et al (2017) is discussed but the work it is being compared with, that of Paul Ehrlich has not been described.

       I note @8 I managed to provide a broken link to the Paul Ehrlich Wiki page.  His work was entirely unknown to me but the idea that the world is heading for an overpopulated and miserable future is not something that hasn't been projected by many others at various times. Yet I was surprised to find that Ehrlich's most famous work "The Population Bomb" (1968) is less a proper study and more an opinion piece with little substance running through its two-hundred pages of chat. (This PDF of its Chapter 1 describes his 'Population Bomb' in twenty-five tiresome pages.) His prediction of "massive famine" within a decade or two didn't fail due to him overestimating population growth (a growth he fails to set out clearly but which can be surmised from his discussion of the various growth rates). Rather, his decadal prediction failed due to increases in agricultural output. However, over a longer timespan, Ehrlich failed to spot the dramatic drop in the global population growth rate. The growth he describes would have yielded a world population of ~10bn for 2017, 25% greater than actually now exists.

       

       As of 2009 Ehrlich doesn't see any problem in predicting in 1968 that the wheels would fall off and humanity would be facing "massive famines" in (pessimistically) a decade or (optimistically) two. He just doubles down and asserts that his "basic message is even more important today than it was forty years ago."

19530. Xulonn at 00:25 AM on 25 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       My favorite meme on this subject, based on the words of the late Professor Al Bartlett: 

       

19531. Larry E at 20:34 PM on 24 May 2017
       Citizens’ Climate Lobby - Pushing for a price on carbon globally
       

       SauerJ, first I didn't propose a tax, but declining cap (with no trade).

       But to address some of what you wrote: The CCL proposal starts out at $10/ton and won't reach the $100/ton in your calculation until a decade out. Due to inflation (e.g. at current rates) and the economy's adjustments to inflation over that period, the situation will be much different then than portrayed in your calculations.

       Also, I believe your calculation for cost to an "average" household of your $100/ton tax doesn't mean much. Because the direct and indirect carbon emissions of the wealthy and moderately wealthy are extraordinarily high, using the average for all households is a distortion. You need to look at the tax impact by "bins" that are determined by household income and the typical carbon emissions for each bin. I think that will give a much different result for households in the bins of average income and lower. (And of course the result will vary by region for various reasons, so the analysis gets complicated.)

       Concerning industries, the time for a soft landing for many of them is rapidly evaporating because global society has delayed so long in effectively addressing climate changing emissions. We need to ratchet down emissions sharply, year-on-year for a prolonged period — much more so than the CCL proposal could accomplish. For many industries the kind or quantity of production will have to change. Some won't survive (and who makes typewriters anymore). That is the pickle we are in, due to past inaction. Other industries will grow or arise.

       You ask how would cap with no trade work. The cap would be on fuel (solid, liquid, gas) production and imports, so indirectly on emissions. The allowed fuel-carbon production/imports would decline year-on-year, moderately for a short period and then sharply. Increases in renewable energy would make up some of the difference, but demand for energy use (for electricity, transport, etc.) will also need to decline (as it must for any real climate solution). The marketplace may play some role in how fuel-carbon is allocated among uses, but regulation will be key in managing that in managing allocation for an orderly ramp-down of FF use. Some taxation on carbon would be used to relieve price impact on low-income households, but the cap would be the instrument for reducing FF use and not particularly the tax.  As Digby suggests, ceasing the search for more fossil fuel should be part of this.

       It is a bitter pill, but is what the climate emergency demands. Perhaps a decade and a half ago the CCL proposal would have been worth a go, but it is not up to the present task and will distract from a real solution. Despite wishful thinking, including by some experts. Do we have the will to survive?

19532. Tom Curtis at 18:18 PM on 24 May 2017
       SkS Analogy 4 - Ocean Time Lag
       

       Evan, I have several problems with your graph, and your explanation of it.  Starting with the most trivial, when you call 3^oC "...the average IPCC estimate..." for the equilibrium temperature response to x2CO₂, it is unclear which 'average' you are talking about.  To be precise, it is closest to the mean climate sensitivity estimate from the IPCC AR5, which there is good reason to think lies somewhere between 3 and 3.1^oC.  It is, of course, never explicitly identified by the IPCC.  It is significantly higher than the modal (approx 1.8^oC) or median (approx 2.55^oC) estimates.

       That is probably for the good in that if the technique of determining the Equilibrium Climate Sensitivity at x2CO₂ illustrated by your graph was valid, then it is essential that your estimate be that which generates the same trend as the observed temperature trend over the period.  Your graph does not show that.  Indeed, the best fit to the current observed temperature trend since 1970 is for a climate sensitivity of 2.85^oC per doubling of CO2.

       More troubling is that that value generates a 'lag' of 21 years, although the precise value is sensitive to how you baseline the "preindustrial" temperature.  I used the mean of the first 30 years of the temperature record.  Had I added the best estimate 0.2^oC for the difference between the 1736-1765 mean and the 1880-1909 mean, the lag would have reduced to 10 years.

       Further, the lag can only properly be interpreted for a climate sensitivity that exactly generates the observed temperature trend.  For other climate sensitivities, because of the difference in trends the lag will differ at different time intervals.  Taken at 1970, the IPCC likeley (ie, 67% confidence interval) range of climate sensitivities generates lags from 6 to more than 39 years using the 1880-1909 baseline.  The lower bound of a hypothetical 90% confidence interval (1^oC) generates a lag of -3 years using your method of determination.  (Note, it is a hypothetical 90% confidence interval because the IPCC do not give the upper bound, instead giving the upper bound of a hypothetical 80% confidence interval, ie, 6^oC.)

       These problems arise because the temperature response is not just a response to the forcing a given number of years ago, no matter what the interval.  If the forcing changed in a single pulse, and remained constant after that change, then indeed the temperature would change over time as a response to that pulse.  It would increase rapidly at first, with the temperature increase slowing over time until equilibrium was reached.  With the actual, gradual increase in forcing, the temperature change in a given year being a consequence of the change in forcing in all preceding years out to a time horizon of potentially several centuries.  This is well illustrated by Kevin Cowtan's two box model (see also And Then There's Physics.)

       This means that the implicit physics of your graph is wrong.  It does not indicate (ie, demonstrate) either the time lag or the equilibrium climate sensitivity.  And taken as an analogy, it confuses rather than illuminates.

19533. chriskoz at 18:17 PM on 24 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Geometric series model applied to the real world always has the flaw that it does not consider the limitted amount of resources to draw the series. E.g.: consider repetitively folding a 0.1mm thick piece of paper as many times as you can. How "thick" does your piece becomes when you fold it, say 50 times (in theory of course)? Answer: from the Earth to the Moon. An obviously absurd outcome, because a simple model of geometric time series representing the process of parer folding did not consider the very limitted physical resources (a piece of paper).

       In case of melting ice sheets, the resources are large but limitted to 70m of SLR-equiv. And when we're talking about an SLR of "many meters" we already are within said limit. We can approximate the current icesheet melting rate with geometric series doubling every 10 or so years (as we do here and as Jim does in Hansen 2016) when dSLR is few mm/y. But our model cannot be accurate at dSLR much higher. Not Jim nor any other researchers, estimated at what dSLR the inflexion point is when such model becomes inaccurate (overestimating) and SLR must slow down, then definitely stop at ca70m.

19534. chriskoz at 16:30 PM on 24 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       The last sentence is is a winner in this article, Evan. It encompasses the punishment for those greedy developers, who would like to cash out of waterfront property values and who deny AGW precisely for that reason.

       In that respect, I only regret that SLR does not progress fast enough (or in a big burst similar to a biblical Yahweh punishment) but unfortunately, SLR is a problem developping in more than one generation timeframe, so our children are about to receive most of the ensuing mess.

19535. Digby Scorgie at 15:06 PM on 24 May 2017
       Citizens’ Climate Lobby - Pushing for a price on carbon globally
       

       Never mind methods of pricing carbon, should a first step not be global agreement to abandon all searches for new sources of fossil fuel?

19536. Evan at 14:28 PM on 24 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Thanks for finding and pointing out this typo. Fixed.

19537. sauerj at 14:27 PM on 24 May 2017
       Citizens’ Climate Lobby - Pushing for a price on carbon globally
       

       Larry E: A few more points to consider:

       1) %Increase of Power & Nat-Gas will much higher than Petro increase: A $100/ton fee would raise 95%coal/5%gas mix generated power (typical US midwest power) by $0.10/kwh (1.9x above current residental rates $0.112/kwh, and 2.45x above current industrial rates $0.07/kwh). Nat-Gas heat would increase from $9.00/dth to $16.0/dth (1.8x increase). These are not minor increases. I agree that the petroleum increase is not significantly substantial (this lower %increase is because its cost/btu is already much higher than that for power & nat-gas), but even a $1/gal will have a noticeable impact on shipping (& its technologies). This higher cost will trickle-down to impact those markets w/ higher % dependency on shipping, resulting in definite impacts on their future market growth. But, for the power & gas energies, as pointed out above, their significant higher increases in cost (almost double for residential power, 2.45x for industrial power), will have significant impact on the future market share for these FF laden products, services & processes.

       2) Summary of Household Costs: Avg US per capita annum CO2 emission is 18tonsCO2/yr; so $100/ton translates to $1800/person, or x 4 = $7200/yr increase for avg household of 4. This injects sizeable incentive to shift market choices to those products & services that will be competitively more attractive (toward lower C footprint choices) while providing the dividend to finance these transitions. As some people start to transition, then the financial incentive on the others, who delay, will increase as their household costs will stay high while their dividend will start to drop as total net FF consumption drops. Investors will definitely shift to RE technologies, R/D will grow because of these new investments, production & installation cost for RE will drop as market share & volume increases & more efficient stds are developed, further reducing transitional costs & giving more incentive to transition to lower C footprint products & services.

       3) Impact on the High Footprint Industries: Industries, who do life & breathe on rational financial terms, and would get no dividend, will be forced to make huge changes or else fail.

       Let me give a real-life transitional scenario for our plant: The impact to the industrial plant where I work would be significant: A) Product Mix: Those products that have a higher FF energy input would have a higher % of cost impact. Customers for these product would likely shift to alternate/lower cost ingredients (lower in cost due to a lower FF footprint), or else shift to more efficient suppliers. Final result: lower net C footprint. B) Process/Technology Changes: Our purchased power cost is currently $15m/yr. W/ $100/ton, power cost will rise 2.45x or rise to $37m w/tax. To reduce costs, we would immediately install CCGT (combined cycle gas turbines), w/ HRSG for 100% cogeneration, so to transition away from the new very high cost of purchasing power. The cogeneration means that the 2.5x of wasted energy from the power plant rankine cycle would seize. Counting this power wasted energy in our total energy usage (i.e. our primary energy), this CCGT project would cut our total C footprint by 27% (yes, this isn't what is ultimately required, but it is a huge first step). ... Today, we don't do this because the $10m/yr payback (based on $20/mmbtu coal+gas purchased power vs gas at $5/mmbtu and 80% ineff) would take ~8-10 years (DCF) to pay off the $65m investment. Change that power cost to $37m, and now the payback is $32m/yr for a 2-3 year (DCF) payoff. Huge increase in financial incentive! Many other cost reduction measure would then be financially justifiable, reaping further reductions in C emissions. ... To think that a $100/ton tax would yield no net reduction in carbon emission does not hold up to standard engineering & economic incentive principles.

       4) Think thru your approach of "Cap w/ No Trade": How exactly would this approach logistically work? Would Duke Energy be given a max quota coal or gas they can burn? One option: they would start using spot brown-outs here & there to curtail consumption to meet these max quotas. Contracts for continuous supply, at a higher cost, would be the immediate business reaction. These increased costs would have to continue to increase until some business could not afford reaching an equilibrium where demand shrank enough to equal the curtailed supply. These higher costs would be passed onto the products. Markets would shift toward lower C footprint products, but the lack of dividend would result in recession. True, such an approach, would cause sharp reductions in FF consumption, but the poor would suffer the most (even though their per capita footprint is the lowest, their energy costs as a percentage of total income is higher than avg). The backlash to the recessionary impact would not be political durable (listen to the @11 Brookings podcast above, which is extremely informative) and thus this approach would not survive into the long-term & thus would not fulfill its ultimate goal of a durable approach to achieve lasting carbon emission reductions.

       Expert Endorsements: It is unlikely that my points will change your mind, but consider the list of endorsements from James Hansen, Katharine Hayhoe, Jerry Taylor (Niskanen Center, read its Case for Carbon Tax), George Shultz & James Baker (Climate Leadership Council, see @14 above for informational link), the Carbon Tax Center, read Shi-Ling Hsu book (the Case for a Carbon Tax). I invite other readers to submit their known list of other expert endorsers. ... These experts recognize the efficacy of a carbon tax & especially the non-regressive revenue-neutral variety. These endorsements should carry some weight in your deliberations. ... Lastly, if $100/ton is too slow, and the economy is holding together OK, then there is nothing to say to stop at $100/ton. But, per the Brookings podcast, a well forecasted rise in the tax is vital so that business can prepare so to avoid recessionary collapse. So, any change in the rate-of-rise of the tax needs to be laid out w/ advance notice and not too-quickly tinkered with, o/w business will be caught off-guard and political durability may collapse. The Brookings podcase explains all of this. ... Take care!

19538. Digby Scorgie at 14:05 PM on 24 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Um, it's "icicle".  Please fix.  No spell-checker will fault "ice-cycle" unfortunately.

19539. Digby Scorgie at 13:50 PM on 24 May 2017
       Trump's Fox News deputy national security adviser fooled him with climate fake news
       

       What I find amusing is that penguins hold their wings like that when they're hot and trying to cool off!

19540. nigelj at 12:43 PM on 24 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Evan @4, I understand your point. Your article was basically just explaining linear versus accelerating / exponenential/ curvilinear using various analogies. It made some good points.

       Here's a very simple analogy. The car washing analogy. Turn the tap on and leave it and you have a linear water flow. My car was really dirty last week, and I found myself turing the tap up, and up over time, which is an accelerating water flow over time. Sea level will be a smoother acceleration than this, but maybe also a bit jerky at times.

       I just recall that this website had a graph of sea level rise over the last 150 years which had a curve fitted that looked like a quadratic or was described as a quadratic, and sea level forward projections until 2100 for my country are a quadratic.  We have been arguing about this projection recently, as to how valid it would be. I'm not even really a maths person, but when reading the article those things were on my mind. But yes, it's a bit beside the point of the article.

19541. Bob Loblaw at 11:22 AM on 24 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       "I thought we were looking at a quadratic sort of curve as opposed to exponential..."

       With a noisy data set like sea level, which shows short term (a few years) ups and downs due to various factors, it can even be hard to tell whether the change is linear or not. Telling the difference between exponential or quadratic would be even more difficult!
       

       We could go all mathy and talk about first and second derivatives, etc., but that would detract from Evan's simple analogy. If the reader really wants to get into this more seriously, then I suggest they wander over to Tamino's where he has some good posts on sea level rise, including this one on acceleration.
       

19542. Evan at 08:19 AM on 24 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Thank you Nigel for your observations and writing about your own experiences.

       I thought we were looking at a quadratic sort of curve as opposed to exponential...

       The original point of this analogy was to educate people about the difference between linear and non-linear trends. For many readers of SkS this is obvious, but is likely a new concept to non-technical readers. I simply chose sea-level rise to illustrate this, so that when they read/hear/see the concept of non-linear being used elsewhere, they have some familiarity with how it differs from linear. The analogy morphed into what it is, but I was not intentending to to write an authoritative essay on expected sea-level rise.

19543. nigelj at 07:49 AM on 24 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Humanity is used to stable and slow rates of sea level rise, and I think we undersetimate the problems of accelerating sea level rise, and humanity is in for a rude multi generational shock.

       Consider for the past couple of centuries, sea level rise has been pretty slow around 100 - 200 mm century, until later last century anyway. In my city buildings have been designed with this slow trend in mind, and its been assumed it would be a roughly linear trend, and also on the basis of general storm flooding in mind, with certain floor levels above ground level, and a building life of somewhere from 50-80 years. By the time sea level has risen significantly by 180 mm over a century or so, buildings have been protected by their floor levels, and reached the end of their natural lives, in the vast majority of cases.

       Flood frequencies have also been predicatable and constant over time.The slow rate of change in sea level and flood events has made planning predictable, and problems have been generally limited. Floods are of course terrible, but have generally been one big one per 100 years and now this is all changing.

       This has all now changed with the understanding sea level rise is going to accelerate. It is of course already changing in places like Florida which are low lying and experiencing significant accelerating sea level rise combined with flood events etc. With 500mm sea level rise by end of this century plenty of buildings will need to be replaced before they reach the end of their natural lives. With 1000 mm the problem increases.

       Increasing numbers of floods due to other facets of climate change adds to this problem and also interacts with sea level rise itself making things worse. Florida and Miami in particular are good examples.

       But that is just the first stage of sea level rise, affecting existing buildings this century. New buildings will then presumably be planned with some sort of accelerating sea level rise trend in mind. I thought we were looking at a quadratic sort of curve as opposed to exponential, by the way, but the analogy of compound interest is still a good.

       But nobody is sure exactly what the longer term rate of sea level change will be, so how high do you design buildings above ground level? This is not so easy to say, and will have to be based on a guess at the most likely trend over the life of the building probably the middle IPCC estimates. It will lead to complex planning zones with certain requirements.

       But its not just buildings as you have to plan roads and drains and drains generally have longer lives than buildings and stop functioning when water levels rise. So it gets hard to work out how to plan.

       And how far inland do communities retreat to in an uncertain changing sea level rise scenario? My government has already ruled out governments building barriers, so it's a question of organised retreat, apparently. Again it will require an assessment of building life, and infrastructure life against a guesstimate at the most likely rate of sea level rise (probably taking the middle scenario). And who is going to want to calculate and enforce all this? It will be politically contentions, and full of mistaken judgements. The process could go on for centuries, in some sort of staged retreat one part of a city at a time gradually hopping inland, or alternatively building barriers that themselves will not last forever.

       And do cities plan for sea level rise a century ahead leading to a multiple staged retreat, or do they look at several centuries and put larger areas of land off limits?

       It will dislocate and cost communities physically, economically, and will have all sorts of socio- economic implications as land prices collapse, and people loose major assets. Nobody is going to want to buy low lying properties, or insure against sea level rise, and governments (tax payers) will as usual end up bailing people out. I think they will have to. It will however become politically contentious, and a drain on government resources for many centuries.

19544. Evan at 02:07 AM on 24 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       Thank you for the comments JWR. Your points are well taken. These analogies will be evolving as we get feedback, so when I rework this I will consider your input. I also understand that the sea-level analysis is overly simplistic.

       That said, I still maintain that salaries exhibit the effect I was looking for: the increase is proportional to the thing itself, whether the driving force is inflation, promotion, or something else. By contrast, aging is a constant for everytone. This basic differentiation is likely new to many people. You are obviously very well educated on these matters, but the main goal of the analogies is to introduce scientific concepts to the lay person.

       Thanks for your input and suggestions.

19545. JWRebel at 01:32 AM on 24 May 2017
       SkS Analogy 5 - Linear, Non-linear, and Coastal Flooding
       

       A better example of exponential growth would have been body weight from conception to puberty, set off against age. Salaries rise mostly with inflation, and are not a real example of growth. There are lots of good explanations of exponential growth floating around. Defining 0% growth as 3mm/annum does not seem to me very good practice. Discussions around GDP growth also exhibit tendency, to talk about 0% GDP when they mean %0 growth, or even worse, decreasing GDP when they mean the second order derivative is decreasing down from 2.5% to 1.7%.

       Note also that thermal water expansion is (almost) linear for the relevant temperature ranges.

       Omitted from the complicating sea-level effects: stronger (c.q. weaker) currents; stronger tidal action (more water); gravity (less ice mass pulls water elsewhere); crustal rebounding (displacing water).

       By the way, in the ancient world (Babylonia, Sumer) they also expressed interest and exponential growth in terms of doubling time. Most agricultural debts were annulled after the first doubling, regardless of how much principle remained. Doubling time is actually a more natural way to think, because it also gives an intuitive grasp of the limits to infinite doubling, the magic of compound interest, etc.

19546. Evan at 00:56 AM on 24 May 2017
       SkS Analogy 4 - Ocean Time Lag
       

       Thanks HK for the info and the education. I have a lot of studying to do.

19547. John Hartz at 23:07 PM on 23 May 2017
       2017 SkS Weekly Climate Change & Global Warming News Roundup #20
       

       Chriskoz:

       More "hot-off-the-press" news about SLR...

       Scientists say the pace of sea level rise has nearly tripled since 1990 by Chris Mooney, Energy & Environment, Washington Post, May 22, 2017

       PS - If you have not already done so, you may want to communicate your concerns about Peter Hannam's article directly to him.

19548. chriskoz at 22:42 PM on 23 May 2017
       2017 SkS Weekly Climate Change & Global Warming News Roundup #20
       

       NOAA SEA LEVEL RISE SCENARIOS recently published is a nice easy-to-read yet very comprehensive SLR summary and prediction until y2200.

       Jump staraight to page 22 - Figure 8 & Table 4 - to learn the precis of their projections. Only a bit higher than IPCC for RCP2.5 but more than twice higher for higher emission scenarios, esp. RCP8.5.

       But their 6 scenarios in table 4 have very sharply defined upper bounds. E.g.: middle range Intermediate scenario (1.0 m SLR by 2100) hasd only 17% hance of excceeding in RCP8.5 emissions. Extreme scenario (2.5 m) is very unlikely - only 0.1% chance of at least such SLR in RCP8.5. I feel like they underestimated the uncertainties in icesheet stability in that scenarion.

       Nonetheless higher SLR than IOPCC, even though somewhat conservative IMO. So, I don't understand the alarming and somewhat exaggerated news about it, like this one by Peter Hannam in smh. Peter quotes the SLR values 2.7 metres as "plausible". I don't even understand where that number came from as I cannot find it in the study in question. But I see the number 2.8m as the central estimate of Intermediate scenario by y2200 (table 5) which is the first such estimate AFAIK.

19549. HK at 22:32 PM on 23 May 2017
       SkS Analogy 4 - Ocean Time Lag
       

       Evan:
       The behaviour of other greenhouse gases doesn’t matter if you know their forcings beforehand and want to convert them to CO₂eq. If the net forcing increases by, say, 1 watt/m², that can be translated to a ~20% increase of CO₂eq regardless of which GHG or combination of GHGs that actually causes this forcing. Therefore, calculating the CO₂eq should be relatively straight forward if you know what forcings to include.
       Translating a certain forcing to another GHGeq is harder because it requires data about the behaviour of that particular GHG, and they are all different.

       BTW, the forcing data I used are available via links on James Hansens site. There you can find both graphs and tables of the forcings as well as concentration data for CO₂, CH₄, N₂O and much more.

19550. Tom Curtis at 13:33 PM on 23 May 2017
       2017 SkS Weekly Climate Change & Global Warming News Roundup #20
       

       PS inline@11, Joe's argument is worse than that.  Haile et al make specific predictions about the impact of climate change in three crops.  They allow that "...some farming changes—such as improved irrigation or genetically modified crops, or more sustainable practices like increased organic production or tilling less—could help offset some climate-induced losses" (from article linked above).  Without specific quantification, it is consistent with Haile et al that those offsets could more than compensate for the climate related losses.  As such, Haile et al represents a prediction about a specific difficulty, without a claim that we will be ruined by it - let alone that it will lead to a catastrophe.  Consequently, when Joe says that Haile et al's conclusions "... have a striking similarity to the Paul Ehrlich et al conclusions", he is guilty of massive exaggeration. 

       Taking that into account, his argument form is really, "x predicted negative consequences in the future, that did not arise, therefore, any predictions of negative consequences in the future of any nature, and no matter how well supported are false".  It is likely, although we have no specific evidence of that, that he makes a specific exception for economic predictions of ruination premised on action to mitigate climate change.  That is, like many climate change deniers he may subscribe to the principle that a free market economy is so robust that it can generate growth regardless of adverse circumstances except for the adverse circumstances of any spefic policy they happen to disagree with. 

       Moderator Response:

       [PS] Give him chance please.

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