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Comments 23001 to 23050:

23001. chriskoz at 09:05 AM on 16 September 2016
       The Climate Change Authority report: a dissenting view
       

       Thanks Clive for that important summary.

       I want to comment on the the implied politicization of CCA, implicitly blamed here on the actions of Abbott government. However the sentence:

       This is all the more regrettable because [the majority report is in opposition to the First Report and a special review] released in April 2015 (before the appointment of six new Members to the Authority in October 2015).

       (my emphsis)

       states that said politicization started happening under Malcolm Turnbull govenment, who assumed the offices of LNP leader & PM of Australia after defeating Tony Abbott in a leadership spill on 14 September 2015. Clearly, Turnbull with respect to climate mitigation, continues inadequate, if not outright wrong policies of his predecessor (Abbott), who as recently as 4-5years ago was saying that CO2 is nothing but "invisible and odourless trace gas", and as recently as 1y ago was saying that "coal is good to humanity". What was the point of the leadership spill of 14 September 2015, since the new PM continues the line of a  disgraced predecessor?

23002. nigelj at 08:51 AM on 16 September 2016
       The Climate Change Authority report: a dissenting view
       

       My understanding is that the Emissions Reduction Fund is essentially a tax payer funded subsidy to encourage things like cleaner electricity generation. I dont totally oppose subsidies on principle, but I agree this one will be very bureaucratic and problematic. This scheme is trying to avoid being too hard on business directly, and so shifts costs onto the public as much as possible, but in a way that subtly hides the costs by giving it a grand, benevolent sounding name. Its laughable really, like a sort of game of hide and seek.

       But conventional emissions trading schemes (Cap and trade schemes, etc) also have considerable bureaucracy and complexity of administration, and are very easy to rort. I just haven’t seen these schemes having any real success, other than growing forests, which helps but is not an adequate answer to climate change. And there will be immense pressure to cut these forests down anyway, for the resource.

       Another approach is carbon taxes, which are simpler to administer. However the problem is they push up the price of carbon, so encourage more oil exploration.

       There are only two viable answers. Firstly direct regulatory control over electricity generation and car manufacturers, although again this has some complexity of rules.

       Secondly go to the source of the problem. Force fossil fuel companies to leave carbon in the ground. This is much simpler and stronger and gets to the cause of the problem.

       But of course this will lead to big protests from the fossil fuel industry, and also the public. We dare not contemplate this option. So we play silly games instead, that have made no difference, or only a very slight difference of no consequence. We pretend to solve the problem by tinkering.

23003. gws at 08:46 AM on 16 September 2016
       An update on methane emissions from fracking (in the US)
       

       Although some of its contents is outdated, the new paper in PNAS basically confirms the above calculations. For instance, they estimated an increase in annual methane emissions from fossil fuel sources of 21 Tg (terragrams, (same as millions tons per year) over the 2000s, which is at the upper end of the 1-2 million tons of anual increase accumulated over 10 years. Other results differ from the competing isotopic study in Science, so I guess we will have post another update some time next year ...

23004. Leto at 08:14 AM on 16 September 2016
       The Climate Change Authority report: a dissenting view
       

       Thank you for releasing this minority report. The deliberate pursuit of policies destined to reach a crisis within ten years should be front-page news.

        I have a some questions.

       1) Are any of the majority report authors available for comment, or have they already released comment elsewhere?

       2) Does the inadequacy of the majority report indicate that the Climate Change authority has become a sock puppet for Abottesque political forces?

       3) Have any of the minority report authors performed similar calculations for the more ambitious target of 1.5 degrees?

23005. terrymorse at 08:06 AM on 16 September 2016
       Extreme weather isn't caused by global warming
       

       I searched for some info on USS storm trends and how they relate to temperature change. But I couldn't find anything pertinent, so I decided to put together something myself that compares storm frequency to temperatures.

       The NOAA Storm Database has records of "Thunderstorm Wind" events going back to the 1950s, so I downloaded the years 1975-2015 (380,026 events in total).

       For temperature, I chose the NASA GISTEMP annual means for the Northern Hemisphere.

       Here's the graph of storm counts and temperatures for the past 35 years, showing a strong correlation between the two (97.35%):

       

       Moderator Response:

       [RH] Adjusted image size. Please limit your images to 500px in width.

23006. Tom Curtis at 14:54 PM on 15 September 2016
       There is no consensus
       

       Hathawad @737:

       1)      "There definitely is a consensus that CO2 can increase temperature, but nobody knows by how much"

       IPCC AR5:

       "The equilibrium climate sensitivity quantifies the response of the climate system to constant radiative forcing on multicentury time scales. It is defined as the change in global mean surface temperature at equilibrium that is caused by a doubling of the atmospheric CO2 concentration. Equilibrium climate sensitivity is likely [probability of 66% or more] in the range 1.5°C to 4.5°C [0.41- 1.22 C/(W/m^2))](high confidence), extremely unlikely [probability of 5% or less] less than 1°C [0.27 C/(W/m^2))] (high confidence), and very unlikely [probability of 10% or less] greater than 6°C [1.6 C/(W/m^2))] (medium confidence)."

       That is very simple to interpret.  If your assessment of the Probability Density Function (PDF) of the Equilibrium Climate Sensitivity (ECS) shows a probability that the ECS lies between 1.5 and 4.5 C less than 66%, you are in disagreement with the IPCC, and your assessment lies outside of the consensus.  If your assessment is that the probability that the ECS is less than 1 C is greater than 5%, you are in disagreement with the IPCC, and your assessment lies outside of the consensus.  If your assessment is that the probability that the ECS lies above 6 C is greater then you are in disagreement with the IPCC, and your assessment lies outside of the consensus.  As a result it is clear that Nick Stokes estimates of the ECS, though low, are clearly within the consensus while those of deniers claiming an ECS of 1 C or less are not.

       I included in the quote from the IPCC the values interpreted as a Climate Sensitivity Factor, which allows you to simply multiply out a forcing to see the temperature response to that forcing.  Thus, at doubled CO2 the forcing is 3.7 W/m^2 +/- 10%.  From the forcing and the Climate Sensitivity Factor, the temperature impact of CO2 at equilibrium is easilly calculated.  In short, the temperature impact of CO2 is known within a significantly constrained range that excludes most denier estimates of the impact.

       2)    "According to believers the icecaps would have been long gone by now..."

       No climate scientist of any repute has claimed that the ice caps (ie, kilometers deep layers of ice covering Antarctica and Greenland, and some thinner ones on islands in the Canadian Archipelago) would have melted by now, or even by the end of the century.    Wieslaw Maslowski and Peter Wadhams has predicted an early loss of Arctic sea ice (ie, the very thin ice floating on the sea surface) around this decade.  The low bracket of their estimate has come and gone.  The central value of his estimate falls in the remaining four years of this decade, and are widely considered by sea ice experts to be utterly implausible.  The actual consensus position, as given in the IPCC AR5 is:

       "Based on the CMIP5 multi-model ensemble, projections of average reductions in Arctic sea ice extent for 2081–2100 compared to 1986–2005 range from 8% for RCP2.6 to 34% for RCP8.5 in February and from 43% for RCP2.6 to 94% for RCP8.5 in September (medium confidence).  A nearly ice-free Arctic Ocean (sea ice extent less than 1 × 106 km² for at least 5 consecutive years) in September before mid-century is likely under RCP8.5 (medium confidence), based on an assessment of a subset of models that most closely reproduce the climatological mean state and 1979–2012 trend of the Arctic sea ice cover. Some climate projections exhibit 5- to 10-year periods of sharp summer Arctic sea ice decline—even steeper than observed over the last decade—and it is likely that such instances of rapid ice loss will occur in the future. There is little evidence in global climate models of a tipping point (or critical threshold) in the transition from a perennially ice-covered to a seasonally ice-free Arctic Ocean beyond which further sea ice loss is unstoppable and irreversible."

       (My emphasis)

       

       (See the upper right panel in particular.)

       So, the consensus position is for a sea ice free Arctic around mid century, approximately 30 years from now, and that being avoidable if we mitigate climate change.

       3)   "...and we would be in knee deep water in Florida".

       The IPCC AR5 predicts a likely range for sea level rice in 2081-2100 of 0.52 to 0.98 meters (ie, enough to make you shin to knee deep if you stand at the current water level) assuming RCP 8.5 (essentially business as usual.  Predictions of knee deep sea level now except as a result of storm surge are figments of your own imagination.

       4)   "Over the past 11,000 years..."

       GISP 2 represents a temperature proxy for only one location on the earths surface, and consequently does not represent Global Mean Surface Temperature (GMST).  You should at the minimum use a mean of several long term temperature proxies, such as this one from Global Warming Art:

       

       The recent decadal average is up around 1 C on this scale, and well above the 2004 value indicated in the graph, and hence above the mean across all decades.  These proxies do not have a annual time scale so some decades in the past 10,000 years may have been warmer than our current decade - but we do not know that any were and it is likely that very few were.  Further, the temperature rise since 1850 is almost certainly unprecedented since the end of the last glacial.

       5)  "During evolution, the CO2 was many thousands of ppm and man was definitely not around then and yet life was possible during this "catastrophic" CO2 level"

       Durring those periods with very high CO2 levels, solar activity was significantly less than it is today.  This is known because solar activity increases overtime in a very predictable pattern.  The result is that combined forcing of CO2 plus solar was not much greater than preindustrial levels, and less than likely levels of forcing with Business As Usual:

       

       It is interesting to note that up to 65 million years ago, land life was dominated by ectotherms and endotherms, ie, creatures much less vulnerable to heat stress than is the case for humans.  Periods of elevated temperatures in the last 65 million years have also see a dominance of smaller animals, with a higher surface to volume ratio and higher basal temperatures (both contributing to more efficient cooling).  Neither of these facts is comforting to large, homeothermic animals such as humans when facing similarly elevated temperatures.  Rodents, snakes and cockroaches, on the other hand, will do just fine.

       In summary, your "points" rely mostly on misrepresenting the claims of climate scientists, or misrepresenting what is actually known.  An argument that can only be pressed by such means (as is the case with nearly all denier arguments) are not worth pursuing, or indeed, giving any credence to. 

       If you surprise me by actually responding, please do so on the appropriate threads as indicated by the moderator.

       Moderator Response:

       [JH] To make it easier for readers to disgest your posts, I suggest that you use italics font for the material you are quoting from the commenter you are responding to.  In this particular case, you may also want to put the quotes in bold-face because they essential serve as subject headers. 

23007. nigelj at 10:49 AM on 15 September 2016
       BBC climate coverage is evolving, but too slowly
       

       Tom Curtis@13

       Yes those seem like sensible media guidelines. I believe freedom of speech is very important, but is only the right to have an opinion without being censored (especially by government), or being assaulted. It is not a right to swear in public, tell lies without consequences, or to promote violence. For example we have defamation suits, and laws against inciting violence.

       The media have a special responsibility for what they say as they have such a wide readership and thus influence. They should of course be free to write whatever opinion they want in general principle, but the media should adhere to some basic standards and face censure if they don’t. Many media have codes of practice, but some are only voluntary in my country.

       For example the media should take all practical steps to ensure articles are honest, and not misleading, and that claims about research are backed up with sources stated. If the media claim they dont have the expertise to discern whether an opinion article by a guest writer is misleading or not, they should at least publish a contrary point of view for balance, and on the same page on the same day.

       However regarding climate change, I think opinion articles by so called sceptics have little value unless its an area of some remaining genuine debate like climate sensitivity. Sceptical opinions should mostly be covered in wider documentary style articles on climate change, that include both the IPCC position and sceptical views (robust points of view rather than the flakey stuff), and in a way that hides nothing and puts all claims in proper context. All the climate sceptical claims I have ever seen fall over once you look at the full context.

23008. Bob Loblaw at 09:54 AM on 15 September 2016
       There is no consensus
       

       Hathawad:

       If you want to learn about these things, go to the "View All Arguments" at the bottom of the thermometer image on the upper left of each page (below "Most Used Cliamte Myths"). You wll find nearly 200 links to various myths, of which your brief posts have covered a surprisingly large number for so few words.

       Your assertions are completely unsupported, and that counts for nothing at this site.

       ...and read the comments policy (link just above the box you type your comment in)

23009. Bob Loblaw at 09:46 AM on 15 September 2016
       Ice age predicted in the 70s
       

       No, Kabothpa, it is not an accurate statement. You seem to have neglected "science" in your comment: the '70s predictions were almost entirely media, with little science, while today there is a very strong science foundation reagarding future warming.

       You have played "bait and switch" (perhaps not intentionally) by first discussing a general statement about the 1970s ice age predictions, and finishing with a statement about media shaping public opinion. How public opion is shaped is not a discussion about the scientific position, and the 1970s scientific position on cooling (extremely limited support) is not at all like the current scientific position on CO2-caused warming (very strongly supported).

23010. kabothpa at 09:25 AM on 15 September 2016
       Ice age predicted in the 70s
       

       What happens when we take this article's opening statement, "1970s ice age predictions were predominantly media based", and apply it to today's climate debate? Let's see:

       "Climate change fears (ice age predictions) of the early 21st century (1970s) were predominantly media based." 

       Is that not an accurate statement? The public's perception of climate change in the modern era has been shaped by the media, not science. Of the millions of people who think they're saving the planet by driving a Prius, only a tiny fraction, far less than 1%, have actually taken the time to review actual scientific data on the topic. They don't know what the term 'greenhouse gas' actually means, nor do they care to. (They also don't know that the Nickel in their beloved Prius's batteries was extracted though mining operations that are more polluting than almost any other human activity).

       The media shaped public opinion on climate in the 1970s just like it does today. 

23011. nigelj at 08:50 AM on 15 September 2016
       Trump and the Republican Party are doing Big Oil's bidding
       

       Is big oil influencing the Republicans? Donald Trump does indeed appear to listen closely and surround himself with the fossil fuel lobby, and climate denialism people. Big oil is influential, and is implicated in attempts to discredit science, and this is all so reminiscent of the tobacco wars. The suggestion of an alternative “scientific method” shows how addicted people are to oil, and how desperate they will become.

       We have lobby groups and corporations funding election campaigns, so obviously they have huge influence over politicians, and the Republicans in particular seem extremely eager to please. The limits in the past on campaign funding in America have been weakened over the last 20 years, due to constant business lobbying, to give the lobby groups absolute power as below. This is the context that empowers climate change denialism.

       www.infoplease.com/us/history/campaign-finance-reform-timeline.html

       I came across this recently. Currently Trump claims climate change is just a hoax by the Chinese to damage American industry, which is of course totally ludicrous. However 7 years ago Trump called for urgent action to stop climate change, as below

       www.theatlantic.com/science/archive/2016/06/trump-climate-change-new-york-times-letter-ad/486335/

       Trump is constantly changing his mind on too many things, and this does not seem like good leadership to me. Trump is possibly making climate change science a sort of expendable tool, to be manipulated or discarded to further his other agendas. This is really dangerous for humanity, and shows his contempt for science.

23012. Tom Curtis at 08:36 AM on 15 September 2016
       BBC climate coverage is evolving, but too slowly
       

       nigelj @12, I would certainly suggest the media treat the public climate science debate like that, whilst also making it very clear what passes as the public debate bears no ressemblance to the actual scientific debates in climate science.  Of course, I would also allow simple reporting of the science without bringing in what are clearly minority (in the scientific community) and poorly supported views.  I think we should expect nothing less than that standard from public broadcasters including the BBC (and the ABC in Australia).

       I also think that reasonably we can go further without risk of violating freedom of speech.  As a first step, it should be incumbent on media, by law, to indicate the primary funding source of their sources.  So, if they use Joe Bast as a source on the climate change debate, they should introduce him as, "Joe Bast from the fossil fuel funded lobbying organization, the Heritage Foundation".  Second, I think any media report claiming to be news or current affairs should meet minimal standards of balance and integrity of the views expressed to be able to make that claim (with a disclaimer that they do not purport to meet those standards if they are unwilling to do so) as a matter of truth in advertising.  Further, the special protections journalists recieve in some countries (and ought to recieve) such as the right to protect sources, and a higher standard of proof in defamation proceedings against them should be conditional on their conspicuously attempting to meet those standards of balance and integrity.

23013. nigelj at 07:33 AM on 15 September 2016
       BBC climate coverage is evolving, but too slowly
       

       Tom Curtis @ 8

       All true enough. Many sceptical claims are simply outrageous, yet the media let them go uncontested. This is wrong, wrong and wrong.

       I gather you are suggesting the media treat climate science somewhat like a Richard Attenborough documentary, and that both sides of the debate are presented, before reaching a conclusion on the more convincing side of the debate (The IPCC position). Climate sceptics would have a chance to explain exactly why they believe climate sensitivity is low, given that most science suggests climate sensitivity is medium to high. Their response would in turn be examined.

       This is my kind of television or writing. It absolutely takes things apart in a rational way. In fact a chap named Gareth Morgan has written a book on climate change called "Poles Apart" where he devotes several chapters to the mainstream IPCC position, and then a couple of good chapters on the sceptical position, - and treats this fairly. Gareth then evaluates everything and explains why he thinks the sceptical position is weak.

       Gareth is actually an economist in New Zealand, but also an environmentalist, multi millionaire and he employed teams of scientists from both sides of the debate for his book and gave them ample input. I have no connection with the guy, I just mention it as a very balanced account of the whole issue, and a very good read as an introduction to climate change for the general reader.

       The trouble is books or media documentaries like this are sophisticated and "nuanced" and may not get the huge crowds, so private sector media aren’t interested. The media have descended into sound bites and desperate attempts to be "noticed" and inflammatory. However I believe the BBC certainly has a duty to treat climate science is this doucumentary way, and it can be made really interesting with some effort. 

23014. hathawad at 05:39 AM on 15 September 2016
       There is no consensus
       

       Why do we analyze only a few hundred years back.

       We need to look back 11,000 years and you will see that the temperature has been much higher in the past and increased at a much faster rate in many occasions in the past. We focus to much on the recent past and its wron to base conclusions on this tiime period alone.

       Moderator Response:

       [TD] This comment is redundant with your previous one. Don't do that.

23015. Nate12674 at 04:25 AM on 15 September 2016
       BBC climate coverage is evolving, but too slowly
       

       Tom #7,

       Agreed, theory often needs to be adjusted or thrown out. But often observations or analysis are wrong or incomplete-throwing out theory that has other supporting evidence can be premature. Example: a recent observation of faster than light particles (neutrinos). Most sensible people took a wait and see attitude rather than throw out relativity, and were proven wise-the experimenters made a mistake.

23016. hathawad at 03:08 AM on 15 September 2016
       There is no consensus
       

       There definitely is a consensus that CO2 can increase temerature,

       BUT NOBODY KNOWS BY HOW MUCH, that part is NOT consensus. According to believers the icecaps would have been long gone by now and we would be in knee deep water in Florida.

       There is no consensus on CATASTROPHIC climate change.

       Over the past 11,000 years the Earth has had temperatures above today's average temperature about 9 times. We are now at average temp according to this data: GISP2 below

       LINK

       During evolution, the CO2 was many thousands of ppm and man was definitely not around then and yet life was possible during this "catastrophic" CO2 level

       Moderator Response:

       [RH] Shortened link. Please note that use of all caps is against our commenting policy.

       [TD] Your comments are most appropriate on several other threads. Please read the following, and if you want to comment further on those topics do so on those threads, not this one:

       "...the icecaps would have been long gone by now." You need to provide a reference for your claim. I'm unaware of anyone who has claimed that. For actual peer reviewed scientific projections of ice loss, type into the Search field at the top left of any page relevant terms such as ice, sea ice, land ice, and glacier, and choose from among the resulting hits. Here is one of those: Read the Intermediate tabbed pane of "How the IPCC is more likely to underestimate the climate response," scrolling down to the section on Arctic sea ice.

       "...we would be in knee deep water in Florida." You need to provide a reference for your claim. I'm unaware of anyone who has claimed that. For actual peer reviewed scientific projections of sea level rise, type "sea level" into the Search field at the top left of any page, and choose from among the resulting hits. Here is one of those: "How much will sea levels rise in the 21st Century?" After you read the Basic tabbed pane there, read the Intermediate one.

       "There is no consensus on catastrophic global warming." "Catastrophic" is too ambiguous a term; scientists' projections are much more specific. Read "Positives and negatives of global warming." After you read the Basic tabbed pane, read the Intermediate and then the Advanced.

       "Over the past 11,000 years the Earth has had temperatures above today's average temperature about 9 times. We are now at average temp according to this data: GISP2 below." The GISP2 graph you linked has as its most recent data the year 1855. Not even 1955, but 1855. So it does not show anything like "today." Also, it reflects the temperature only from a single spot in Greenland, which is not at all representative of the entire Earth. Read "Most of the last 10,000 years were warmer." To learn about temperature indices that are representative of the entire Earth, and that go up to much closer to today, read "Real skepticism about the Marcott hockey stick." Then use the Search field to look for more posts  about Marcott, and posts about PAGES 2K.

23017. Tom Curtis at 02:22 AM on 15 September 2016
       2016 SkS Weekly Digest #37
       

       Zoli @24, I don't know how big an issue you thought it to be, but AGW is one of the biggest, indeed probably the biggest policy issue facing humans today.  That is because, while there is a reasonable chance of a soft landing* (climate sensitivity in the lower half of the probability range, damages at a given temperature in the lower half of expected range, rapid reduction in net global emisisons), there is a significant risk of absolutely catastrophic outcomes (climate sensitivity in the upper half of the PDF, damages in the upper half, and very limited reductions in net emissions).  Thinking that the former makes AGW a non-issue is like thinking that Russian Roullette is safe because there is a five in six chance that you will not blow your brains out.

       Second, the IPCC is fully aware of all the factors discussed here.  The image you provide an URL for shows the outcomes of specified scenarios with prescribed emissions history, and concentrations calculated from those emissions history using carbon cycle models that take into account all the factors we discuss.  Most of those scenarios do not achieve net zero emissions in this century, and hence show ongoing temperature increases. Remember, for CO2 concentrations to be drawn down naturally, CO2 emisions have to fall to less than 10% of their peak values - something that does not even occur in RCP 2.6 until late in the century, and not at all in the other scenarios this century.  So, no.  The IPCC are not "alarmists".  Rather they are realistic and well informed.

       

       (* Note:  Even a soft landing will involve many individual climate caused catastrophes - just not a global catastrophe. 

23018. ubrew12 at 01:53 AM on 15 September 2016
       BBC climate coverage is evolving, but too slowly
       

       denisaf@9 said: "policies to reduce emissions can only slightly slow down this damaging process".  If we managed to hold CO2 at today's 400ppm, by end of century the rise would be 2 C.  If instead we get to 560ppm (BAU out to 2050), the rise will be 3 C.  But that's the expected mean: there's a one-in-six chance the rise (after 560ppm) will be 4.5 C or higher.  A 'roll of the dice' of a global extinction event, if we let CO2 get to 560ppm.  So, depending on your tolerance for risk, 'policies to reduce emissions' seem prudent, to me.

23019. Zoli at 00:51 AM on 15 September 2016
       2016 SkS Weekly Digest #37
       

       @chriskoz

       @Tom Curtis

       Thank you. So climate change isn't that big issue as I thought.

       And IPCC authors are alarmists because they didn't count the quick CO2 drop.

       [img]http://i67.tinypic.com/vddces.jpg[/img]

       Long term changes, page 1104

23020. chriskoz at 18:50 PM on 14 September 2016
       2016 SkS Weekly Digest #37
       

       scaddenp@21,

       A typo crept into my comment@19.

       I ment to show, that if you could have PVs that collect 200W peak power per m² in AL, and jam-pack that site with such PVs, then your peak power output from that site would be (647ha = 6,470,000m²) * 200W = 1.3GW.

       Obviously I see now, that 200W peak power is incorrect and not correct metric. With the more reasonable metric you pointed out (5kWh/m2/day) we and up with average insolation of just 200W over 24h. With 10% PV efficiency, the energy yield would then be 0.13GW averaged over 24h - 10 times less than planned nuke yield. Needless to say the yield would be intermittent, unlike nuke. With the best available commercial PVs  approaching now 20%, the yield would still be five times less than nuke.

       However I did not underestimate the cost of jam-packing that site with PVs. The latest estimate of PV cost is at $0.3 per 1W capacity.

       

       So I the total cost of such project is $0.13Giga*0.30 = $39m

23021. chriskoz at 16:15 PM on 14 September 2016
       2016 SkS Weekly Digest #37
       

       Tom@20,

       Thanks for your clarifications to what I agree.

       Your posts always have very precise meaning, allowing easy and clear discussion, a benchmark of quality blog commenting.

23022. denisaf at 16:12 PM on 14 September 2016
       BBC climate coverage is evolving, but too slowly
       

       I am an Australian physical scientist who has followed the debate about climate change due to emissions of industrial operations for decades. There is very little uncertainty about the hypothesis that irreversible atmospheric climate disruption and ocean acidification and warming is occurring. Comprehensive  atmospheric and ocean measurements have backed the arguments of climatologists. The emerging global policies to reduce emissions can only slightly slow down this damaging process even if it these policies can be implemted as rapidly as physically possible. More emphasis should be placed on measures to adapt to the consequences, such as sea level rise, more severe storms, more droughts and more floods.

23023. scaddenp at 14:21 PM on 14 September 2016
       2016 SkS Weekly Digest #37
       

       I hectare is 10,000 m2, so I think your area is off by factor 10. Since solar incoming is 1367W/m2, I dont your solar panel is going to give you 200W/m2. NREL puts Alabama available solar input at 5kWh/m2/d

23024. Tom Curtis at 14:12 PM on 14 September 2016
       BBC climate coverage is evolving, but too slowly
       

       nigelj @6, a lot that passes for climate denial consists of straighforward, and often ludicrous pseudo-science and/or conspiracy theories.  If we had a news media that actually took seriously their duty to inform, these would not be presented in news and current affairs shows, and only presented in documentaries that fisk them.  This is not different to who we would expect new media to treat numerology, astrology, 911 Trutherism and other various nonsenses given air by credulous people on the internet.   Scientifically, thes include opinions that:

       Humans are not the cause of the current rapid rise in CO2 levels;

       CO2 forcing is not in the order of 3 - 4 W/m^2 per doubling;

       The climate sensitivity per doubling is not greater than 1 C per doubling of CO2.

       Of more interest are theories that the climate sensitivity is in the range of 1-3 C, which are not excluded by the IPCC.  Likewise, for theories that increased global temperatures will be net beneficial up to about 2 C.  Neither of these possibilities are excluded by the IPCC, given that they represent the lower half of the uncertainty range of IPCC estimates.  The question that should be raised is why the proponents of these views are so much more certain about their conclusions; particularly given that they typically exclude large parts of the relevant evidence.  In short, if those opinions are to be reasonably discussed, the framing should be an attempt to allow them to defend themselves against a charge of convenient dogmatism.

23025. Tom Curtis at 13:59 PM on 14 September 2016
       BBC climate coverage is evolving, but too slowly
       

       Nate @5, in science, a consensus is commanded by observations.  There are significant social aspects involved in how that comes about but science is a self correcting enterprise in which what drives the corrections are a determination to ensure theory matches obvservations by altering the theory where the two differ.

23026. Tom Curtis at 13:54 PM on 14 September 2016
       2016 SkS Weekly Digest #37
       

       chriskoz @17, CDIAC (or TJBlassing, at least) gives an exponential time constant for CH4 of 12.4 years, meaning it will take about sixty years for CH4 to drop to natural concentrations, following the cessation of all anthropogenic emissions (and ignoring changes in 'natural' emissions as a result of feedbacks on changes in temperature and/or precipitation).  Just saying that it has a lifetime of 12.4 years (or 10 years) may mislead some into believing essentially all CH4 will be gone in about a decade, which is false.

       Further, when you use CO2eq, particularly when using all anthropogenic forcings, aerosols also have a low exponential time constant so that the rapid fall in CO2eq concentration will be, at least roughly, balanced by a rise in CO2eq concentration due to the reduction in aerosol concentrations.  That is not relevant in discussing Zoli's figure which is based on greenhouse gases only, but it is relevant when discussing the more appopriate European Environment Agency figure I discuss above.  The initial relatively rapid fall in CO2 concentration, given zero net anthropogenic emissions still quickly reduces the CO2eq concentration in that scenario, and sustains your very important point.

       As a side note, "long lived greenhouse gases" by convention are any greenhouse gas which does not condense out of the atmosphere, ie, any greenhouse gas other than H2O, which has an exponential time constant measured in hours.

       r @19, peak generation capacity is probably not the best measure given that mean generation capacity of solar is significantly less than nuclear, and that even peak generation capacity requires cloud and haze free skies on only a few days in the year, and then only around noon.  More typically, daily peaks will be 10% or more less than that, and will represent a minority of the days output.  Fossil fuel and nuclear power unquestionably require less space than renewables for a given generation capacity.  Your example, however, certainly provides andecdotal evidence that economically solar trumps nuclear. 

23027. chriskoz at 13:09 PM on 14 September 2016
       2016 SkS Weekly Digest #37
       

       Interesting what's going on with nuclear in Alabama:

       For sale: Multibillion-dollar, non-working nuclear power plant

       I'm posting it here because there were discussions about advantages of nuke over renewables. Now the renewable ulitily company is placing a bid on this nuke site were $6b have been completely wasted.

       I'm not going to argue about advantages of renewables over nuke, but I note that this 647ha site was meant to be generating 1.2GW of nuke power. If you covered such are with PV panels (this is what the prospective renewables buyer is likely to do) in the range of 10% efficiency, which is ~200W/m², you will get 647,000,000*200W = 1.3GW of peak power. The same capacity as the ill-fated nuke, surely at the small fraction of the investment cost ($50m) and essentially free running to some 20y.

23028. Tom Curtis at 10:19 AM on 14 September 2016
       2016 SkS Weekly Digest #37
       

       Zoli @16, I will add a few points to Chriskoz's excellent response.

       First, the estimate of CO2eq concentration you use is for greenhouse gas concentrations only.  It does not incorporate all anthropogenic impacts on Global Mean Surface Temperature.  Once you include the impact of other factors, in particular that of aersols, the CO2 eq emissions as of 2014 (ie, the most recent year for which data is available) was 440.6 ppmv CO2eq.  For comparison, the 2014 value from your linked source was 481 ppmv CO2eq, with a most recent value (2015) of 485 ppmv CO2eq.  I take it your 487 ppmv CO2eq represents an estimate of the additional increase in the half year since the end of 2015.  Similarly estimating the approximate trend increase of for all anthropogenic factors gives 446 ppmv CO2eq, or 1.6 times the preindustrial average (compared to the GHG only estimate of 1.74 times the preindustrial average.  Therefore the GHG only estimate is a substantial overestimate for estimating future climate impacts.

       Second, the IPCC AR5 does not give median or mean estimates of the Equilibrium Climate Sensitivity (ECS).  From the estimates they do give, and a reasonable assumption about the shape of the Probability Density Function (PDF) of the ECS, it is possible to estimate that while the mean value is in the order of 3- 3.4 C, the median value (ie, the value such that we have a 50% chance of an ECS less than that) is in the order of 2.4-2.7 C.  Therefore, based in the IPCC AR5, even at a CO2eq concentration of 600 ppmv, there is a 50/50 chance that we will not exceed a GMST of 2 C.  (Based on mean values of the ECS, we need to keep CO2eq concentrations below 525 ppmv.)

       I consider a 50/50 chance to be a "realistic chance", and also consider it a very realistic possibility that we will limit total CO2 emissions to double the 2014 increase over preindustrial values or less, ie, about 600 ppmv CO2eq.  That by itself is sufficient to justify my claim.

       I should note that this is little comfort to AGW deniers and those wanting a slow reduction in CO2 emissions.  That is because, assuming a linear increase in damages with increase in temperure the relevant value of ECS is not the median, but the mean; and damages are likely to increase more than linearly with increased temperatures.  That is why estimates of the emissions reduction task are based on values which are likely (66.6% probability) to keep GMST below 2 C, where the value minimum value which is likely to achieve that is just slightly higher than the mean estimate.

       Third, based on a current CO2eq concentration of 446 ppmv, and a requirement to stabilize it at no higher than 525 ppmv by 2050, we can increase it by no more than 79 ppmv over 34 years, or in other words to limit the average increase over that period to 2.33 ppmv per annum, and with a current average increase 3.5 ppmv per year (approximately).  If we reduce the increase on a linear basis, by 0.1 ppmv per annum, the average emissions over the 34 years will be about 1.8 ppmv, well below the threshold.  That is clearly a physically, and technically feasible reduction program, although other reduction programs will probably be better.  The reasons for pessimism, and they are reasons for grave pessimism, are entirely political.  Will the leaders of the nations of the Earth have the collective will to pursue an emissions reduction program of that magnitude.

       Finally, these are not my only reasons for my statement.  I think it is more important that the ECS will not be achieved for many years after a stable CO2eq concentration is reached, and that with zero net emissions, the CO2eq concentration will be drawn down by the ocean fairly rapidly up to a limit.  That limit is about 25% of the current CO2 concentration, which will be drawn down much more stably.  That means if net emissions can be reduced to zero (and certainly not more than 5% of current values), CO2eq concentrations will fall rapidly such that by the time ECS is reached, the CO2eq concentration will result in a temperature rise approximately equal to the Transient Climat Response to the peak CO2eq concentration.  That gives us significantly more leeway than calculations based on the ECS allow, as indicated by Chriskoz.  

       Note, again, the decision to drop down to zero net emissions is a political one, and it is far from clear that the politics will result in that decision.  The approach favoured by many economists of putting a social price on CO2eq emissions and then allowing emissions to stabilize where they will will certainly result in ongoing emisisons.  Indeed, it will likely result in ongoing emissions greater than 10% of peak emissions which would mean the eventual stable temperature will be in excess of that estimated from ECS, and would continue slowly rising into the future for as long as net emissions were greater than zero.  However, if sensible policies are pursued, ie, any policy that secures measured reductions in global emissions, achieving net zero emissions by 2050, or net negative emissions at a slightly later date has a good chance of keeping GMST below 2 C (except in El Nino years), and a reasonable chance of keeping it below 1.5 C above preindustrial levels.

23029. nigelj at 08:06 AM on 14 September 2016
       BBC climate coverage is evolving, but too slowly
       

       Many media including the BBC do indeed have this fake balance issue. I see a similar thing in media in my country of New Zealand, where there is broadly a 50 / 50 split in certain specific media between warmist articles (for want of a better word) and sceptical articles. This may create an impression with some people that climate scientists are equally divided in their views, which is not the case. Over 90% of climate scientists agree we are warming the climate, according to several different carefully conducted polls.

       There seems little point having sceptical articles contesting generally well established elements of the science like "the greenhouse effect".

       For other sceptical articles that discuss something that is in genuine doubt, perhaps the BBC should have an advisory at the top or bottom of the article that reads basically something like this : “Advisory to readers : The BBC advises that the IPCC has determined we are warming the climate, and over 90% of climate scientists agree we are warming the climate, according to published polls (then a list of the polls).

23030. chriskoz at 07:55 AM on 14 September 2016
       2016 SkS Weekly Digest #37
       

       Zoli@16,

       You are wrong in thinking that the "GHGs equivalent of 487 ppm CO2" must stay in the atmosphere while Earth is warming in equilibrium (next 40+ years). The GHGs breakdown:

       

       indicate that some 30% of the GHG forcing is from CH4, which increased since 1750 by about 1ppm. But CH4 has the lifetime of only 10y (the image is wrong in labeling CH4 as "long-lived") after which it oxidises to CO2. The forcing of the resulting 1ppm increase in CO2 is negligible compared to the existing CO2 forcing from 400/280 ppm. All we need to do is stop emitting CH4 and that part of forcing quickly goes to essntially zero.

       Secondly, if CO2 emissions ceased today, it would not stay at 400 ppm forever but would slowly equilibrate with ocean reservoir over the next few decades or so, while the temperature is, hopefully still reaching the equillibrium. Read e.g. Archer 2005 for details. The bottom line is: current CO2 amount of 400ppm is not "locked". Only about 15-25% of the 400/280 in crease (i.e. 30-40ppm) will stay in the atmosphere for 100s thousand y (essentially forever).

       So currently, the amount of "locked CO2" is 310-320 ppm only. Of course realistically, it will be more because of continued emissions and science denial by FF interest groups, but cetainly not yet as high as you claim (487ppm).

23031. Nate12674 at 07:42 AM on 14 September 2016
       BBC climate coverage is evolving, but too slowly
       

       I think part of what Abloke said is worth discussing. He is putting down science consensus about a theory as being inferior to science facts. In my viw all science, whether observations, or theory, become accepted and established by consensus. 

23032. Nick Palmer at 23:02 PM on 13 September 2016
       BBC climate coverage is evolving, but too slowly
       

       ABloke. You haven't got a clue about the reality of the situation as you clearly don't know what you are talking about.

23033. Tom Curtis at 22:48 PM on 13 September 2016
       BBC climate coverage is evolving, but too slowly
       

       To the moderators, I was surprised to see ABloke's comment get any positive thumbs on a reasonably educated forum.  I was especially surprised to see that he got it so quickly.  Consequently I ran a test and found I could give my own comment a thumbs up.  I ask that the moderators remove that thumbs up, which was only done as a test, and remove also ABloke's if it was similarly underserved.

23034. Tom Curtis at 22:43 PM on 13 September 2016
       BBC climate coverage is evolving, but too slowly
       

       I can only assume that ABloke writes frequently to the BBC complaining about the lack of coverage of phrenology, geocentrism, and hollow Earth theory, given his peculiar definition of "balance".  Or is it perhaps only the pseudoscience he adheres to that he thinks deserves to have its public plausibility boosted by inaccurate reporting by the BBC. 

23035. ABloke at 22:33 PM on 13 September 2016
       BBC climate coverage is evolving, but too slowly
       

       If anything, the BBC have been rabid AGW alarmists with a 'the debate is over' slant on most if not all is 'climate/weather' related coverage.' If anything, they are becomimg slightly more balanced than in the past and certainly in the piece you refer to. The BBC is supposed to be balanced in all things and if anything, this report represents that balance. CO2 driven climate change is 'Theory' not a fact, and theory with very little to back it up, so they cant say C02 'does' cause climate change, no matter how much youy scream 'unequivocal scientific consensus' and '97%' because there is none and for the sake of balance, the BBC have to report as such. They cannot present things as scientific fact, when there is 'no' scientific fact to back it up. 'Consensus' just doesnt cut it.

       Moderator Response:

       [JH] Pure undadulterated poppycock, i.e, sloganeering.

       Sloganeering is prohibited by the SkS Comments Policy.

       Please read the policy and adhere to it. If you do not, you will relinquish your privilege of posting comments on this site.

23036. Zoli at 19:26 PM on 13 September 2016
       2016 SkS Weekly Digest #37
       

       @Tom Curtis

       "First, it is not clear that we are past the point where a realistic global emissions policy will prevent an average rise of temperatures above 2o C."

       Why? As I understand we have accumulated GHGs equivalent of 487 ppm CO2 so far. http://www.esrl.noaa.gov/gmd/aggi/aggi.html

       487/280 (pre industrial) =1,74

       So we almost doubled the GHG amount.

       Climate sensitivity estimates are about 2,5-3 Celsius.

       0,74×3 = 2,22

       0,74×2,5 = 1,85

       So we achieved the requirements for 2 Celsius rise. The only question is the time the world needs to accumulate enough heat, melting ice etc.

       There is a chance the climate sensitivity estimates or my simple calculations are wrong of course.

23037. Eclectic at 15:11 PM on 13 September 2016
       The Madhouse Effect, a review
       

       Martin, I agree with Gws @5.

       There is a vast number of things you can make a joke about.  Even "gallows humour" jokes about Death/Taxes.

       But jokingly denying Global Warming is uncomfortably close to denying wife-beating or denying genocide.  It's poor taste.  Just don't go there, unless you're a very very very clever humorist !

23038. chriskoz at 11:17 AM on 13 September 2016
       2016 SkS Weekly Digest #37
       

       It's worth noting that even though habitability of Earth by homo sapiens (as defined by Sherwood and Huber (2010) and promoted by Tom Curtis here) does not change much with even very pessimistic AGW scenarios, the life expectancy of all homo sapiens individuals will be curtailed severely, as Tom himself asserts:

       Such temperatures will result in significant death tolls among the elderly

       I would love to see the life expectancy metric quantified for various RPC scenarios & various regions, because this is far better metric of AGW direct impact on homo sapiens species, rather than Sherwood and Huber (2010) metric. However, I don't know if anyone tries such quantification; I guess there is not enough historical data for the very moderate warming so far and any data is hidden behind the influence of technology and improved hygiene which prolongs life expectancy.

23039. One Planet Only Forever at 09:24 AM on 13 September 2016
       2016 SkS Weekly Digest #37
       

       Tom Curtis@11,

       The main point of my comment remains.

       It is unacceptable for a current generation to impose any challenges on future generations. And it is even less than unacceptable for a portion of a current generation to be benefitiing at the expense of others in the current generation as well as at the expense of future genrations. This is a combination of depletion of non-renewable resources and acumulated impacts of human activity.

       Also, the full understanding of the robustness of other life required to sustain human life will likely only become well understood when it is too late to reasonably mitigate the impacts and created challenges. The current generation is already faced with a many bigger challenges to mitigate because of the "lack of restraint and lack of concern for the future" of previous generations.

       Moderator Response:

       [JH] You could do us a great service by rolling-up your comments into an article for posting on SkS.  

23040. Bob Loblaw at 09:07 AM on 13 September 2016
       2016 SkS Weekly Digest #37
       

       For some reason, in Tom's comment 11, the link to the XKCD cartoon has extra junk at the start. This one should work. The cartoon is definitely worth it - thanks, Tom.

23041. Tom Curtis at 08:34 AM on 13 September 2016
       2016 SkS Weekly Digest #37
       

       Moderator inline @4, the only contact information for Coral Davenport that I can find is her twitter account.  As I do not, and will forseeably, have a twitter account that does not help me.  I would be quite happy, however, for somebody else with a twitter account (or other contact details) to advise her of this dicussion.

       Moderator Response:

       [JH] Try: coral.davenport@nytimes.com

23042. Tom Curtis at 08:20 AM on 13 September 2016
       2016 SkS Weekly Digest #37
       

       XKCD has an interesting cartoon on global warming, which is unfortunately too large to place here.  Quote:

       "[After setting your car on fire.]  Listen, you car's temperature has changes before."

23043. Tom Curtis at 08:09 AM on 13 September 2016
       2016 SkS Weekly Digest #37
       

       OPOF @7, you need to draw a distinction between conditions under which humans can continue to live as a biological species; and those underwhich we can sustain our current population and civilization.  If, biologically, only a million humans are able to continue ekeing out an existence near the polar caps, reduced to the state of hunter gatherers than Earth is still inhabitable by humans.  Under those conditions, we know it is inhabitable because humans continue to inhabit it.  

       The level of ecological complexity needed to sustain such a life is minimal compared to that which exists today.  All that is required is the existence of some prey animals, and some (perhaps wild) fruits for sustenance.

       You also need to understand the type of robustness found in ecological systems.  It is relatively easy to knock an ecological system out of kilter - to remove a key species so that a large number of other dependent species will also be lost with the result that the surviving system can sustain only a far more limited total number of species, and total biomass.  But the ecosystem as a whole will survive (will predictably survive) the loss of 90% or more of species.  We know that because it has happened at the Permian mass extinction.  More importantly, we know that because the most difficult factor any living thing has to deal with in its environment is other living things.  The range of nearly all plants could be greatly extended were it not for the competition of other plants more suited to particular conditions.  Likewise with animals.  The effect of a mass extinction, consequently, is to remove the most fearsome impediments to survival of the surviving species.  That loss of competition itself allows the survival of species not specifically dependent on particular other species for survival.

       That last condition is most easilly met by generalists - those species not adapted to any particular condition but found across a wide range of conditions across the planet.  Among these, preeminent among large animals are humans.

       So, except for two caveats, humans will survive the coming ecological collapse.  I say the coming collapse because if global warming does not do it (and temperature increases of 4 C may well bring it about), species transfer by trade will; and if not that over fishing will.  The two caveats are that global mean surface temperatures do not rise by more than 10 C, and that we do not spark intense enough wars as a result of the collapse so as to exterminate ourselves.  Even if we do that later, after a few years the Earth will be uninhabited by humans, but still habitable.

23044. nigelj at 08:07 AM on 13 September 2016
       2016 SkS Weekly Digest #37
       

       One Planet Only @7

       You seem to make the point that too many people are putting their selfish short term concerns and personal benefit above the concerns and rights of future generations. I agree with this, and it’s not a viable long term plan for the planet.

       Part of the reason is just selfishness. However part of the reason may be how we process information. Humans are evolved to be good at processing information on short term risks, but struggle to get to grips with long term risks, especially complicated ones. There is some psychological research on this, and I can't remember where, but probably easily googled. There is thus a temptation to just ignore the long term future as being too hard to contemplate.

       Of course experts and long term thinkers have tried to do the job for us. The Stern report looks at long term issues and costs of climate change and costs of mitigation, and shows that reducing emissions can be done at an affordable cost to society. However the media have suspiciously avoided much discussion of this research, and it is dismissed by climate sceptics with a wave of their imperious hands.  What a surprise.

23045. nigelj at 07:49 AM on 13 September 2016
       2016 SkS Weekly Digest #37
       

       Tom Curtis @ 2 and 4.

       All your points are well made, and seem technically correct to me, and are informative for a non climate scientist like me. I agree it's important people are accurate in descriptions, and avoid hyperbole.

       However you might be falling into your own trap in one regard. You make the valid point that too much concentration on the 2 degree limit and unproven claims that its been breached, gives climate sceptics an excuse to claim its too late to do anything.

       However you then give a description of research that heat stress only becomes a problem at 35 degrees or more at 100% humidity and this requires 7 - 10 degrees of warming. This in turn gives the climate sceptics breathing space, as they would argue we will never hit such large temperature increases!

       I also recall India has just had a massive, record setting, extended and dangerous heatwave with temperatures of 35 - 50 degrees. This may not be at 100% humidity, and as concerning as the definition in the Sherwood research, but its still very stressful. The last IPCC report stated that theres already evidence of increasing heatwaves, so this is already a problem in some regions.

23046. gws at 03:41 AM on 13 September 2016
       The Madhouse Effect, a review
       

       Martin @4: That is an interesting anecdote. Were you onboard with the joke you made, or were you actually just uninformed at the time, trying to make conversation?

       If this had happened to me (atmospheric scientist) back then, I would have tried to "convince" you as well; if it happened to me today, in the US, I would shut up and maybe try to move away from this (joking) person.

23047. One Planet Only Forever at 01:00 AM on 13 September 2016
       2016 SkS Weekly Digest #37
       

       Tom,

       A scientific assessment of the regional temperature change that "human beings" could live with is, like all such science, just the evaluation of a bit of the whole.

       Human survivability is actually only able to be properly assessed on the whole, not by a bit. That means that the survivability of the robust diversity of life which human beings are only a part of needs to be understood.

       That is a much more complex matter to figure out. It would seem likely to only be well understood when it becomes apparant that the warming was too much too fast, when it is too late to practically mitigate the created and unavoidably obvious damage done.

       It would seem that the practical sustainability of human life as a sustainable part of the robust diversity of all life far into the future on this amazing planet could be challenged by a significantly lower amount of temperature change than the change that 'Human Beings evaluated in isolation of other life' could tolerate. And any created challenge for future generations deserves to be acknowedged as a fundamentally unacceptable thing for a previous generation to do to a future generation (it is fundamantally unjust to consider the opportunity perceived to be lost by a portion of a current generation to be able to be balanced against the challenges created for future generations - as percieved by those in the current generation who would be giving up their opportunity for more personal benefit).

23048. John Hartz at 23:38 PM on 12 September 2016
       2016 SkS Weekly Digest #37
       

       Manmade climate change is already directly impacting humans in ways we are just now beginning to understand...

       Blame Global Warming for Your Bad Attixtude by Eric Roston, Bloomberg News, Sep 8, 2016

23049. chriskoz at 18:50 PM on 12 September 2016
       2016 SkS Weekly Digest #37
       

       Tom@4,

       Now I undesrtand that you really mean homo sapiens uninhabitability threshold be 7-12^oC based on Sherwood and Huber (2010). It's higher than I imagined previously & I thought it (erroneously) be a typo. Thanks for your explanation.

23050. Tom Curtis at 17:56 PM on 12 September 2016
       2016 SkS Weekly Digest #37
       

       chriskoz @3, Sherwood and Huber (2010) (SkS discussion here) state:

       "Peak heat stress, quantified by the wetbulb temperature T_W , is surprisingly similar across diverse climates today. T_W never exceeds 31 °C. Any exceedence of 35 °C for extended periods should induce hyperthermia in humans and other mammals, as dissipation of metabolic heat becomes impossible. While this never happens now, it would begin to occur with global-mean warming of about 7 °C, calling the habitability of some regions into question. With 11–12 °C warming, such regions would spread to encompass the majority of the human population as currently distributed. Eventual warmings of 12 °C are possible from fossil fuel burning."

       Their estimates of regions effected are based on areas that have at least one five hour period with T_w (wet bulb temperature) equal to or greater than 35 C in a year.  They are slightly pessamistic about the survivability of such temperatures, given that mine workers routinely work 10 hour or longer shifts with T_w up to 32.5 C.  Wet bulb temperatures of 35 C are survivable with no work, no sunlight, plenty of hydration, and cooler conditions after the five hours.  That is, provided you are healthy and acclimatized.  Such temperatures will result in significant death tolls among the elderly, but do not necessarilly render the areas uninhabitable.

       As the extent of such 35plus T_w areas increases, however, the prospect of Tw significantly greater than 35 C, or extending through most of any given 24 hour period increased, and that will render the areas uninhabitable for practical purposes, and certainly by 12 C, large portions of the Earth's surface will be uninhabitable in the summer (or for the tropics, spring and autumn) seasons.  10 C represents a convenient intermediate benchmark to express this idea more simply.  If you want to insist on the 7 C value, however, I will not object - but there is no basis for a claim of uninhabitability at 4 C.

       Note, even at 12 C, a significant part of the Earth will remain inhabitable, and much more of it on a seasonal basis; which by it self is sufficient to refute Coral Davenport's claim. 

       Moderator Response:

       [JH] Coral Davenport is a journalist for one of the world's most influential newspapers. Therefore, it would be extremely beneficial if you could communicate your concerns to her. The more journalists know about the science of climate change, the better off we will all be. 

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