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Comments 24801 to 24850:

24801. bozzza at 04:31 AM on 30 March 2016
       New survey finds a growing climate consensus among meteorologists
       

       Also, @ 4, did you know you can dry your par boiled chips in the freezer before their second deep fry?

       NB: I might not be exactly right..!(??)

24802. bozzza at 04:18 AM on 30 March 2016
       New survey finds a growing climate consensus among meteorologists
       

       @4, I don't want to ask in the wrong forum but can you tell me: does it not snow at the poles?

        I was told it doesn't snow at the poles for the reasons you gave in the previous answer but was wondering how far away from the poles(if at all true) this takes place and how it changes,... or indeed if it is a useful indicator of climate change while we're on the subject?????????

24803. MA Rodger at 21:57 PM on 29 March 2016
       CO2 is just a trace gas
       

       Am I suffering from DPD (decimal point shift) or are we all missing a trick with this 'CO2 is just a trace gas' myth-busting? Are we missing an argument with a wow-factor-par-excellence?

       I have just been reading a screed on vaccuum, how in the most empty bits of distant space the atoms (or more correctly the bits of atoms that exist in the WHIM) are about half a metre apart. The screed contrasted this separation with the comment that out atmosphere has atoms spaced at about one million per millimetre which is getting down to the sort of distance similar to the diameter of atoms.

       So here we go:-

       There is 400ppm CO2 in the atmopshere and it requires 2.13Gt(C) to add a further 1ppm. So there is 852 Gt(C) = 8.52+e17 g(C) contained within atmposheric CO2.

       If this is divided by weight (C=12) and multiplied by Avogardo's number, we obtain a number for the molecules of CO2 within the atmosphere. 8.52e+17 x 6.022e+23 /12 = 4.28e+40 molecules CO2.

       An atom has a rough diameter of 0.3nm. Thus it has an area roughly equal to 7e-20m^2 and a sheet of carbon made from the carbon content of atmospheric CO2 would have an area of something like 6e+19m^2.

       As the area of the Earth is 510 sq km = 5.1e+14m^2, this means any point object attempting to exit the planet Earth from ground level (straight up in a straight line would be the shortest route) will have to pass through the middle of (6e+19/5e+14=) 120,000 molecules of CO2, even if they were aligned edge on and only showing an area equal to one of its atoms.

       So it appears correct to say that, while there is only a small % of CO2 in the atmosphere, the (lower) atmosphere is quite well packed with molecules and molecules are very small. So there is a very large number of molecules in the atmosohere and, even if they are only a small % of the atmosphere, there is still a very large number of CO2 molecules within the volume of the atmosphere.

       For a photon to travel the 7 miles or so to reach the stratosphere, it will pass through a very large number of atoms and a lot of them will be the atoms of CO2 molecules. To make such a journey a photon would have to negotiate its way through the middle of something like 120,000 CO2 molecules. If the wavelength of that photon is the sort that has a problem passing through CO2, any one of those 120,000 CO2 molecules could be the one that grabs it and brings its outward journey to a halt.

24804. BBHY at 21:44 PM on 29 March 2016
       New survey finds a growing climate consensus among meteorologists
       

       Has anyone else noticed that everytime it snows some people claim that we are having record cold temperatures?

       Most meteoroligists are smart enough to know that snow and cold temperatures are two separate things. In fact, very cold temperatures generally bring little snow, as colder air can't carry much moisture.

       Meteoroligists can't help but notice that they get to say the words "record high temperatures" much more often than "record low temperatures". If nothing else that should give them a pretty good idea of what's going on.

24805. mercpl at 19:24 PM on 29 March 2016
       How to inoculate people against Donald Trump's fact bending claims
       

       There are no good choices for US president.  Even Clinton represents BAU which will guarantee catastrophee.  Obama was a good president, but proved to be totally ineffectual re climate change.

       
       The election result doesn't really matter because the US president is much less powerful than people imagine.  The real power lies with Wall street and the mega-corporations.  They are finally seeing the light as fossil fuel prices tank and their profits shrink.  As always, just follow the money.  When renewables become more profitable than fossil fuels, then we will see some change.

24806. bozzza at 18:13 PM on 29 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       @8, Nice first paragraph.

       Economies are meant to be robust and pulling out of long picked winners wasn't meant to be easy.

24807. One Planet Only Forever at 14:47 PM on 29 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       Tom,
       I apologize if my persistent attempts to clarify your position (and mine) appear to be misrepresentation of your position. Let me try again.

       International Policy is only words if effective means of enforcement do not exist (that would be effective methods of dismissing sovereignty when required, something you called totalitarian which was a rather gross misrepresentation of my position, but I did not choose to claim it was).

       What Paris produced is better than without Paris, but it is still only words that can be chosen to be ignored by the current or future leadership of sovereign nations. And the US is already falling behind on the Paris pledge because the Supreme Court made an unprecedented move that barred the lower courts from proceeding with implementing enforcement of existing rules that would reduce coal burning until an appeal to the Supreme Court is heard (and the people currently hiding behind the Republican Party brand are demanding that the replacement for Justice Scalia, one of the voters in favour of the 5-to-4 split decision that implemented that unprecedented action, only be proposed after the next election, because they hope they can win the Presidency and get their preferred deciding vote into the Supreme Court, or at least benefit a little longer by delaying the advancement of humanity).

       And the apparent stranglehold on the House (the body that ultimately controls the money in the US Government), by a group of people Obama mistakenly believed could be negotiated with bodes poorly for any of the words of Paris to meaningfully change things. That group has deliberately underfunded, or made as ineffective as they could, any enforcement of the current rules of the game in America. It is very likely that a continuation of obstruction by that group like the past 30 years is to be expected (and it is not just that group in the US but also the likes of them behind similar Parties in places like England, Australia and Canada who claim to be Conservative. I know the Conservative Party lost the last Canadian election, but they are not guaranteed to lose the next one, just as the Democrats in the US are not guaranteed to win the Presidency or control of the Senate in the upcoming election, the control of the House by the Republicans is almost guaranteed).

       So your vision of effective International Policy meaningfully limiting the harm that is done by 'people who have little interest in advancing humanity to a lasting better future for all when doing so would be contrary to their personal interests in their lifetime' is only an illusion unless there is the type of international effective enforcement you declare is unacceptable.

       So my answer to your question is that there is unlikely to be any meaningful progress until there is a meaningful change of the game that dramatically reduces the ability of such people to succeed. You may want to believe that 3 degrees faced by 'future generations' is OK. But I would ask you to prove that the 3 degrees will not become 5 degrees, because the resistance to giving up undeserved opportunity for personal benefit just to reduce the troubles others will face is still able to succeed into the future.

       And I return a question about your timelime. How is your timeline affected if the current cast of Republicans continue to control the House and Senate after the upcoming election? And what if the Republicans also win the Presidency? And worst of all, what if the Republican President is Ted Cruz (a known deliberate misrepresenter of information hoping to win more success for those who do not care about advancing humanity)? If you would claim such events would have little effect on your timeline then there really is nothing more to discuss, no other way for me to understand your position.

       But I would have to add another question. Why is it OK for a portion of a current generation of humanity to continue to enjoy things that are understood to be unacceptable 'just because they had developed a burning desire and the power to get away with it'? (Sadly, the quote I shared from the 1987 UN Commission Report in my comment @13 continues to explain things very well).

24808. Tom Curtis at 12:11 PM on 29 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       nigelj @19, FWIW, although I disagree on specific policy positions based on my own analysis, my political sentiment is broadly the same as that found in the Green Left Weekly that my cousin helped found.  More specifically, I am what I call a democratic, market socialist.  

       Democratic because it is the only political system compatible the moral principle that you should always only act as though people were ends in themselves, and never merely means to an end, which I consider fundamental to ethics.   On that basis I consider the US very imperfectly democratic, primarilly due to the undue influence from campaign funding, but also due to some peculiarities of the constitution.  On the same basis I would strongly support reforming the General Assembly so that each nation had a number of its seats proportional to the population to which it gives the vote (such that, for example, if they deny votes to women, they halve their number of seats), and were the representatives are directly elected, along with other democratizing reforms for the Security Council.

       Socialist because I believe radical title to all property rests with the people, and more formally with the government acting on the peoples behalf; and that the rights accruing from that radical title (including the right to regulate and tax) should be excercized on behalf of the people generally rather than on behalf of special interest groups.

       Market because I accept that to the most part, a free market is the most efficient distributor of goods where 'free market' is implicitly defined by the fundamental argument to that effect, and therefore requires:

       1. No coercion, including no coercion resulting from the pressure to make trade on disadvantaged terms due to declining economic circumstances;
       2. Perfect knowledge of the outcomes;
       3. Perfect competition, in the sense that anybody making a trade has at the time of the trade an infinite number of alternate trades with marginally different properties in respect to all aspects of the trade; and
       4. No negative externalities.

       The argument presented by capitalists that markets are the most efficient form of distribution of goods (where efficiency is defined as Pareto Optimality) assumes these conditions, and therefore they are the implicit requirements that a market be 'free' as assumed in their arguments.  It is blindingly obvious that unregulated markets are not always, indeed are not typically free in this sense.  IMO, the principle economic role of governments is to regulate with a light touch to ensure that markets are as 'free' as possible (using my special definition of 'free').  Further, it is evident that 'pareto optimality' is not the same as a maximum utility outcome, and hence not the desired policy outcome for any government working 'for the people'.  Specifically, income disparities decrease the utility function of a market outcome; so governments should also work to decrease income disparities, and to increase individual control of economic activity.

       On top of all the above, I am a conservative in the original sense that I believe that change should be implimented gradually, except where it must be made with the utmost urgency.  That is because the more rapid the change, the more harmful side effects, and also the greater probability the outcome will not be the intended outcome.

       I have, until now, avoided stating my political views on public forums lest they distract from the discussion of climate science.  However, I state them here so that you can see that I am not against radical change to the international order, to national systems of governance, or to the economic order.  On the contrary, I am strongly in favour of just those - and it is highly probable the OPOF would agree with many of my proposed changes if I detailed them.  What I am very strongly against is making any of my (or anybody elses) proposals for such changes a precondition on tackling climate change.  We do not have sufficient time for that luxury.  Regardless of whether current systems of governance or economics in the US or elsewhere are favourable for tackling climate change, we are saddled with those systems now, and our strategy to respond to climate change must be based on the fact that those current conditions are the conditions in which we must proceed.

       If we do not accept that, we shackle ourselves with an initial step in tackling climate change of 'setting up the right conditions' to tackle climate change.  That in turn requires implimenting reforms that will be even more resisted than a carbon tax; and which currently have no political momentum (in the US and Australia at least).  In other words, it is a recipe for failure.  Even if we take the initial steps against AGW we can take while preparing the ground for later more radical changes, we have greatly increased the difficulty of our political task while giving climate change deniers rhetorical ammunition for their conspiracy theories.  

       In essence, if OPOF or Naomi Klein are right, then it is already too late to tackle climate change and we are committed to >2 C world.  The first thing to realize is that, if that is the case, we still need to do our best to reduce emissions - and our most rapid way to do that in the short and medium term is through the current systems of governance, and the current economy by implementing a carbon tax/ emissions trading scheme plus some regulation and funding of renewable energy research.  The reason we need to do that is that though 2 C is already bad, 2.5 C is still much better than 3 C, which is much better than 3.5 C.  Every gigatonne of reduced emissions is a win for future generations.

       Second, as it happens there are good reasons to think Naomi Klein and (especially) OPOF are not right.  First, as I understand it, there view that the US and other first world nations need to reduce emissions at greater than 4% per annum (and hence faster than is compatible with economic growth) is premised on assumption that first world nations should make a greater effort to tackle climate change (which they largely have caused) than third world nations (who will be disproportionately the victims).  While I agree with that, that is a political view not shared widely in the West, and is not the basis of current plans to tackle global warming.  It is not a necessity for tackling climate change, but only a necessity for tackling climate change fairly.  And while tackling climate change unfairly is very undesirable, it is not a undesirable as starting world war 3, as would be necessary to force the US government to abandon capitalism against its own will, and the will of its people as OPOF proposes.

       Further, the physical reduction of emissions in the US or other western nations faster than 4% per annum is only actually required if we prevent emissions trading between first world and third world nations.  In a fair world, any nations with current per capita emissions less than India would not currently be required to reduce emissions.  Indeed, would be allowed to expand them initially for several years.  That expanded emissions allowance could be traded to first world nations with the money funding renewable energy based economic expansion.  That in turn allows the first world nations to meet their targets with ongoing physical reductions in the order of 2% per annum, ie, at levels that are consistent with continuing economic growth. 

       In short, OPOF and Naomi Klein's approach is only necessitated by treating 2 C as a hard barrier, which it is not, by an optional (if ethical) decision about reduction targets, and a further decision about administrative methods that is also optional, and not based on ethical considerations.

       I hope this explains things better.

24809. barry1487 at 12:04 PM on 29 March 2016
       New survey finds a growing climate consensus among meteorologists
       

       I'd be interested to see the results broken down according to who thought/didn't think they were a climate expert.

24810. barry1487 at 11:36 AM on 29 March 2016
       New survey finds a growing climate consensus among meteorologists
       

       gws, a bit of googling helps.

24811. barry1487 at 10:29 AM on 29 March 2016
       Global Warming Basics: What Has Changed?
       

       Good question. If this were all the data we had we might be misled. But because it's not all the data we have, we don't interpet just from this subset, we use more to test it.

       Having limited stats skill, I'd test with incrementally more annual data to see if the trend changed much and the statistical significance wavered. If so, I'd say that the period selected had spurious statistical significance.

       I'd also make sure that I only used complete years, in case there's a residual annual cycle that, despite anomalising, could skew the results for such a short time period. As it happens, Jan 2011 - Dec 2015 also produces a stat sig trend for that data set. (You also get one for 2008 to present, but not to Dec 2015)

       I'd also regress that period (and a longer period), detrend and look for outliers, which I'd see in the last months of the analysis. Then I'd explore the possibility of a physical explanation (internal variability) to explain the jump at the end.

       I'm not sure that answers your question, though. I'd guess there is a different, perhaps more sophisticated statistical analysis that could demonstrate that the statistical significance for that period was probably spurious.

24812. nigelj at 08:49 AM on 29 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       Tom Curtis.

       You write some good posts on other topics. However on this one I'm trying to get some understanding of what you are saying, because its far from clear, in any respect.

       For the record I'm an economic and political moderate who would rather modify capitalism than try some completely new system. However Naomi Klein does make some good criticisms of how capitalism is making reducing emissions difficult. I assume you are aware of her views, so I would appreciate your brief comments, so I cant get a handle on what you really believe.

       It is also not clear what emissions reduction strategy your are promoting. I seem to recall you saying trading in carbon credits? But these emissions trading schemes are working too well.

       However perhaps you see these schemes as likely to be the most palatable to the public and business community?

       In my view the best scheme in functional terms would seem to be carbon taxes, although this might be politically harder to sell?

       I think we also need direct government regulation of what energy mixes power companies follow.

       However I would like to know exactly what you are promoting.

24813. Kevin C at 06:12 AM on 29 March 2016
       Global Warming Basics: What Has Changed?
       

       I'm very happy to see that the classical mistake of assuming that a non-significant trend is evidence of there being no trend (i.e. the null hypothesis fallacy) has been avoided. Barry explained that quite clearly.

       To recap, null hypothesis tests are assymetric. We can prove the presence of a trend (that is significantly different from zero), but not the absence. The test can only say "yes" or "I don't know".
       
       So here's the next step. If we look at the trend since 2011 (in this case in GISTEMP, some other datasets and periods also work), we see a 5 year trend which statistically significantly different from zero.

       

       As the period gets shorter, it gets harder and harder for the significance test to give a 'yes' - it almost always says 'I don't know'. But in this case it says 'yes'.

       In this case our intuition would probably tell us that this is not compelling evidence of a global warming trend. For a start, it is more than 4 times the expected global warming signal. So how do we interpret this result?

24814. gws at 03:19 AM on 29 March 2016
       New survey finds a growing climate consensus among meteorologists
       

       John, what about the rest? 29%+38%+14%+5% = 86% < 100%

       Could you also provide a link to the results when available?

24815. Tom Curtis at 01:02 AM on 29 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       OPOF, @17, has grotesquely and serially misrepresented my claims.  Most grotesquely, he purports my defence of incremental changes under the current international system with current national forms of government as being sufficient to tackle global warming somehow commits me to un elected international organizations taking over control of recalcitrant governments.  Nor does he seem to recognize that that commits him to a totalitarian system.  Consequently I no longer consider him a protagonist for rational discuscion.

       For those who might by in the slightest persuaded by OPOF, may a recommend that he detail his timetable.  How long to establish the international orgianizations with the power to overtake sovereign governments.  How long to provide income to arm the forces of that organization.  How long to recruit, equip and train its armed forces.  How long to take over the operation of recalcitrant sovereign governments.  How long, in fact, before we can take step one to actually tackling AGW.

       If he thinks that is not what it will take, he is welcome to specify the measures required to develop international cooperation sufficient to field a force capable of taking on the US armed forces with a reasonable prospect of success (which would require, at a minimum, the full cooperations of the EU, Russia and China, and result in a pyrrhic victory at best).  He can also specify how discussion of these options will not reinforce the opposition to action on AGW in the US, which is significantly fueled by conspiracy theories of just such courses of action.

24816. barry1487 at 00:31 AM on 29 March 2016
       Global Warming Basics: What Has Changed?
       

       billev,

       I have a difficult time believing that carbon dioxide at one part in 2500 parts of atmosphere has any role that influences the global temperature. There is just not enough there there.

       1 in 2500 parts arsenic to body weight would kill you. Pretty much instantly. Small changes can produce large effects. The 'hole' in the ozone layer was brought about by CFCs and other halocarbons that in sum increased by a few parts per billion.

       Most of the gases in the atmosphere are not greenhouse gases. So take out all the gases that do not contribute to the greenhouse effect. This is the effect we're concerned with. Now the amount of CO2 compared to the other GHGs is a much larger fraction. Not to mention that CO2, molecule for molecule, is a strong greenhouse gas. Different gases have a different 'power' as greenhouse gases. Takes quite a bit of work to lay all that out and figure CO2's relative contribution to the greenhouse effect - about 9% to 26%.

       Here's a figure worth incorporating. The concentration of CO2 in the atmosphere has increased by more than 40% from the time human industry began pumping it out since the industrial revolution. And there is no doubt that that increase is entirely anthropogenic.

24817. One Planet Only Forever at 00:25 AM on 29 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       Tom,

       I most passionately disagree with your attitude that you would rather see humanity perish than have callous unscrupulous misleading people have their freedom of actions effectively limited. Anarchy and Chaos are not my vision of a better future. That would mean accepting the past 30 years of successful denial of climate science and 'defending it into the future and admiring any continued success the denial industry can develop'.

       The point you object to is the measures that "International Policy" required to address this issue will require in the current socio-economic-political system of 'individual pursuit of personal interest governing what goes on through regional temporary developed impressions of popularity and profitability'.

       It is rather curious that you would claim faith in it being developed then declare opposition to it.

       It has not developed through the past 30 years because of the successes of wealth, power and misleading marketing in the fatally flawed system that clearly fails to be interested in advancing humanity.

       I want a future for humanity. That requires systems that will effectively limit the damaging consequences of those among humanity who choose to only care about maximizing their enjoyment of their life any way they can get away with. Defending such people and labelling powers that would limit their ability to do damage "totalitarian" is rather inappropriate.

       I defend everyone's right to say what they want. However, I do not defend their right to get away with making stuff up that they prefer to believe or the resulting promotion of activity that impedes the advancement of all of humanity to a lasting better future.

       And I would support measures that effectively remove such people from positions of power and influence (and remove undeserved wealth from them), no matter how regionally popular they are able to become (temporarily) or any how sneaky they were about getting away with something unacceptable.

       That is nothing more than having rules and enforcement in socio-economic-political systems to ensure the games are won by deserving people, just as every sport ever developed had to develop ways to keep cheaters from 'winning through unacceptable actions', and just as every city has by-laws and every nation has criminal laws.

       Humanity needs global 'laws and enforcement' that would be imposed contrary to temporary popular and profitable nation interests. And it is becoming clearer that that will require being able to remove people from power who can be shown to have knowingly tried to impede the advancement of global humanity. If the US would impeach the likes of Ted Cruz or any other harmful misleaders that get away with being elected (and they have not done so yet so they appear unlikely to) there would be no need for 'totalitarian (your application of the term not mine)' international intervention (that you refer to as International Policy, which is just empty words if it isn't enforceable).

24818. barry1487 at 23:46 PM on 28 March 2016
       Global Warming Basics: What Has Changed?
       

       Maybe, MA. There are upsides to giving someone the benefit of the doubt. They may deserve it and you were too quick to judge. You get better at explaining things with practise, and at judging the level at which to pitch the explanation. Other people who bother to read the comments may learn something new or useful.

       Perhaps the most telling of his comment is @6 where he says "I am not talking trends I am talking temperature history."

       That told me that he doesn't know much about trends and how important it is to analyse them properly. Seems to me (right or wrong) he's read a few items on temp history, isn't too familiar with the general debate or the details, and might learn something useful through discussion. If not, no matter. Someone else may get some use out of the chat.

       Unless the only people reading down this far are belliv and the locals... but it's a big world and SkS is a fairly prominent cli-sci blog.

24819. MA Rodger at 19:00 PM on 28 March 2016
       Global Warming Basics: What Has Changed?
       

       barry,

       I don't think you should take the words of belliv too literally. Rather you need to take his entire set of comments as a whole.

       Perhaps the most telling of his comment is @6 where he says "I am not talking trends I am talking temperature history." His comments are redolent with talk of "pauses" and these he contrasts with the "spikes" which he sees correctly as being of no long-term relevance. But he also talks of "pattern" and it is this "pattern" of "pauses" (a 30 year pause which is inevitably followed by 30+years of warming and then another pause) which he sees as compelling, as the main feature of the entire temperature record (which he restricts to the years since 1880). Thus he is armed with the insight to predict that the period 2002-2032 will deliver the world another "pause," that any warming since 2002 is but a "spike," that any trend calculated over less than 60+ years is fradulent and that any physical basis for the way the universe works is but hokus pokus.

       It is safe to say that there is no arguing with that.

24820. Tom Curtis at 17:47 PM on 28 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       OPOF @13:

       "Essentially, the International Community would have to be able to 'remove from power' any elected representatives in a nation like the USA (or leaders of businesses) who would claim that already fortunate people should still be allowed to benefit as much as they can from actvity that produces CO2 from the burning of fossil fuels (or be able to convince a bunch of voters who are easily tempted to be greedy or intolerant to change their minds and choose not to try to get away with getting what they want even though they probably could collectively get away with it, for a little while, perhaps long enough that they enjoy the undeserved benefits in 'their lifetime'.)."

       It is this, totalitarian instinct that means I will never agree with you on this issue.  I would rather the world perish striving for greater democracy than that it retreat to totalitarianism to preserve a mere, grubbing survival.  Fortunately, however, that is a choice we need not make.

       That is leaving aside that as a matter of practical politics, no external power would be able to removed the government of the US (or China, or Russia) without bringing us to nuclear war.

24821. Tom Curtis at 17:36 PM on 28 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       dklyer @14, The Economist's article on the IEA announcement states:

       "The IEA’s provisional findings will fan a debate about whether global emissions have peaked. China, after all, is trying to rebalance its economy away from heavily polluting industries towards services. But analysts say two years is too short a period to be considered a lasting trend. What is more, the IEA is relying on data that many economists question. If China’s official growth figures are exaggerated, then it would not be becoming less carbon intensive as fast as it seems."

       It is evident from context that what is doubted is the growth rate in China, not the net emissions.  Ergo your skepticism about the result is not warranted.

       For what it is worth, a seperate research group was predicting in December of 2015 that CO2 emissions would in fact decline slightly on 2014 levels, as also reported in The Economist.  So, if anything the IEA's report on emissions is conservative relative to the appropriate experts.  I would not read too much into that both because the Global Carbon Project team were partly projecting, and because the IEA by its nature has the best data available on actual emissions from fossil fuels.

       With regard to the CO2 concentration, in the very short term, CO2 levels are largely driven by temperature.  A very large increase in Global Mean Surface Temperature (GMST) as occured between 2014 and 2015 will result in a large rise CO2 concentration, while a large fall in GMST will result in a small rise in CO2 concentrations (indeed a fall if there is not net emissions).  The flat CO2 emissions means, absent variations in GMST, we would have expected a 2 ppmv rise in CO2 concentration in each of 2013, 2014 and 2015.  The very sharp rise in temperature between 2014 and 2015 results in a significantly higher rise in CO2 concentration.  With flat emissions, the rise in 2016 will be slightly higher again if 2016 is hotter (as seems likely).  However, later cooler years will have a much smaller rise in CO2 concentration, even with flat emissions.

24822. dklyer at 15:03 PM on 28 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       Tom@12, I read about the IEA release in the online version of the Economist and as much as I’d welcome some good news I’m not sure I agree. As the article stated, “the IEA is relying on data that many economists question.” Meantime actual measurements show a different story.

       From the Scripps Institute, Keeling Curve page, “The annual growth of atmospheric carbon dioxide (CO2) during 2015, above three parts per million (ppm) per year, was the largest ever recorded at the Mauna Loa Observatory in Hawaii, said climate researchers Wednesday. Independent observations by NOAA’s Earth System Research Laboratory and by Scripps Institution of Oceanography at UC San Diego show that not only did 2015 have the largest increase, but also that the annual increase was larger than two ppm for each of the last four years, another first.”

       Maybe you know how the IEA estimate is put together or whether other factors, such as decreasing natural sinks, might affect the CO2 measurements? I’d listen to reasonable arguments but, for now, I’m skeptical.

24823. barry1487 at 14:50 PM on 28 March 2016
       Global Warming Basics: What Has Changed?
       

       belliv,

       Here are a couple of references examining mid-century flat/cool trend.

       https://www.skepticalscience.com/global-cooling-mid-20th-century-advanced.htm

       http://web.archive.org/web/20080501064616/tamino.wordpress.com/2007/08/17/hemispheres/

        

       And a more technical commentary on one paper, adding background detail:

       http://www.realclimate.org/index.php/archives/2009/04/yet-more-aerosols-comment-on-shindell-and-faluvegi/

       There are many factors affecting climate on various time scales. The questions you pose about fluctuating climate over the last 150 years or so have been long investigated. I hope you're not close minded as some here have suggested, and that you're curious enough to learn more about that aspect.

       (Excuse the lengthy response/s. Answers to your questions may be given in a paragraph, but probably not to the satisfaction of a truly skeptical mind. Each of us has to estimate how much detail is helpful)

24824. One Planet Only Forever at 13:51 PM on 28 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       Tom,

       Faith in a system governed by 'temporary regional or tribal popularity and profitability among a current generation of humanity' effectively limiting the challenges it creates is not justified. The popularity of 'a better personal life in a person's lifetime' is a very powerful tool for people who would choose to abuse misleading marketing to prolong their ability to get away with actions they can understand are unacceptable.

       Your final point “International policy settings are not at a stage where that is yet likely, but they are not far off.” is unjustified wishful thinking. In the late 1980s the global community was also very close to acting responsibly to limit the challenges created for less fortunate people and for future generations ... but we all know how the last 30 years have gone ... bigger problems created with more wealthy and powerful troublemakers developed (not all wealthy powerful people are undeserving trouble makers, but many of them clearly are).

       The challenge today did not need to be as big as it is. All that was required was for the undeserving more fortunate, wealthier and more powerful people on the planet, people who gambled on getting away with less acceptable ways of living and profiting, to admit they deserved to lose their bets, to admit they did not deserve their perceptions of prosperity.

       The 'system of competition for maximum reward in an individual's lifetime is the real problem, creating mainly problems and few real sustainable solutions (if it creates any that can win in the popularity and profitability game made up by those who gamble on getting away with less acceptable ways of doing things it is almost completely by accident)'. The system has a clear track record of developing and prolonging activity that is understood to cause troubles that are faced by 'others', particularly those in future generations.

       I have previously shared this quote from “Our Common Future”, a UN Commission Report published in 1987, but it can never be repeated often enough.
       “25. Many present efforts to guard and maintain human progress, to meet human needs, and to realize human ambitions are simply unsustainable - in both the rich and poor nations. They draw too heavily, too quickly, on already overdrawn environmental resource accounts to be affordable far into the future without bankrupting those accounts. They may show profit on the balance sheets of our generation, but our children will inherit the losses. We borrow environmental capital from future generations with no intention or prospect of repaying. They may damn us for our spendthrift ways, but they can never collect on our debt to them. We act as we do because we can get away with it: future generations do not vote; they have no political or financial power; they cannot challenge our decisions.
       26. But the results of the present profligacy are rapidly closing the options for future generations. Most of today's decision makers will be dead before the planet feels; the heavier effects of acid precipitation, global warming, ozone depletion, or widespread desertification and species loss. Most of the young voters of today will still be alive. In the Commission's hearings it was the young, those who have the most to lose, who were the harshest critics of the planet's present management.”

       The only way the required International Policy Settings will happen is the demise of the system that is driven madly by temporary regional and tribal popularity and competition to maximize personal reward. Unlike action for Ozone reduction (something that was actually less effective than it needed to be), there is a massive amount of personal desire in powerful pockets around the planet that can be mobilized to prolong the ability for undeserving people to 'enjoy creating a bigger problem by getting away with things they do not deserve to be able to get away with'.

       The belief that individuals being free to do as they please in pursuit of a better present for themselves will advance humanity to a better future, or even allow humanity to have a future, deserves to be shattered. And it will be shattered if the required effectively enforced International Policies can be imposed on all nations, including the nations that elect leaders who would be regionally popular because they refuse to behave responsibly.

       Essentially, the International Community would have to be able to 'remove from power' any elected representatives in a nation like the USA (or leaders of businesses) who would claim that already fortunate people should still be allowed to benefit as much as they can from actvity that produces CO2 from the burning of fossil fuels (or be able to convince a bunch of voters who are easily tempted to be greedy or intolerant to change their minds and choose not to try to get away with getting what they want even though they probably could collectively get away with it, for a little while, perhaps long enough that they enjoy the undeserved benefits in 'their lifetime'.).

24825. barry1487 at 13:27 PM on 28 March 2016
       Global Warming Basics: What Has Changed?
       

       belliv, you can do a test for whether there has been a pause in warming by comparing the uncertainty estimates for various periods (ie, prior to and after 2002). If you understand me so far regarding the uncertainty estimates, I'll lay out a fairly easy test you can do with apps available on the web, such as the one I used to generate these graphs.

       Here's the link to the graph generator if you want to have a look at that.

       http://www.ysbl.york.ac.uk/~cowtan/applets/trend/trend.html

       You can access the same app near the top of the left hand side side bar on this page, labeled 'Trend Calculator'.

24826. barry1487 at 13:13 PM on 28 March 2016
       Global Warming Basics: What Has Changed?
       

       To compare, here is what a trend estimate that shows warming looks like. Note that the trend is positive (warming), and the uncertainty is smaller than the trend. In other words the uncertainty is only to do with the degree of warming - it doesn't include a zero (or negative) trend estimate.

       Full time period for Remote Sensing System - Jan 1979 to Dec 2015:

       

       Now the trend is anywhere between 0.06 and 0.19 C/decade. The uncertainty does not include zero or negative values, only positive. We call this a 'statistically significant' trend.

       Let's do the same for NASA, same period.

       

       Trend is anywhere between 0.12 and 0.20 C/decade. The uncertainy doesn't include zero or negative values. The trend is statistically significant, unlike the trend estimates in the previous post.

24827. barry1487 at 12:51 PM on 28 March 2016
       Global Warming Basics: What Has Changed?
       

       Here are the other trend estimates for the various data sets.

       NASA: anywhere between -0.03 to 0.27 C/decade

       
       
       

       UK Meteorological Office: -0.07 to 0.23 C/decade

       

       Here are the global satellite data sets:

       Remote Sensing Systems: -0.25 to 0.21 C/decade

       

       University of Alabama, Huntsville: -0.14 to 0.31 C/decade

       

       The uncertainty estimates are larger for the satellite data sets because their data have more variability. You can't determine a trend or 'pause' from data sets as short as these. You need longer time frames.

       (For all of the data sets, including more data backwards from 2002 reduces the uncertainty until it is eventually smaller than the trend, and every one of them shows statistically significant warming once that threshhold is reached)

24828. barry1487 at 12:13 PM on 28 March 2016
       Global Warming Basics: What Has Changed?
       

       Yet in the several responses to my original comment I have seen no acknowledgement of the pauses.

       Say what? I wrote in the first line of my first response to you, comment number 8 in the thread:

       You are quite right that the long-term record has intermittent temp rises over multidecadal time scales, with a mid-century period relatively flat.

       Current understanding is that the warming caused by CO2 in the 3 decades post WWII - at that time not rising as fast as now - was offset by aerosols from industrial emissions and volcanism, which cool the surface. During the 70s and 80s various Clean Air acts and environamental policies around the developed world reduced aerosol emisions (smog etc), and the underlying warming continued. Also, this mid-century flatline or slight cooling is prominent in the northern Hemisphere, but not noticeable in the Southern Hemisphere, lending credence to the notion that aerosol emissions from heavily industrialized countries that are mostly located in the NH were in part responsible for the flattish global trend.

       Everyone dismises the notion of a 'pause' from 2002, including me, for the reasons given. The uncertainty in such a short data stream preclude any confirmation of whether the surface has been warming, cooling or flat. But I certainly acknowledged the mid-century flat period in my first comment to you.

       Here's the trend + uncertainty estimate from Jan 2002 to Dec 2015.

       

       The mean estimate is an upward trend, but, the uncertainty of +/- 0.145 means the trend could be slightly cooling, flat, or strong warming. To put it in numerical terms, the trend is anywhere between -0.012C to 0.278C per decade (95% confidence intervals).

       That's a proper reading of the trend estimate. No one can claim a 'pause,' warming or otherwise from such a short data set.

       NASA and the other data sets produce different trend estimates but they all have a larger uncertainty than the trend.

24829. Glenn Tamblyn at 12:09 PM on 28 March 2016
       Global Warming Basics: What Has Changed?
       

       billev
       
       "There is just not enough there there."
       
       Quoting the percentge of  CO2 isn't the relevant point. It is how many CO2 molecules are present, not the proportion.
       
       A cubic  meter of air, at sea level, contains around 8.5 thousand million, million, million CO2 molecules.
       
       Still sound insufficient.

24830. Tom Curtis at 10:01 AM on 28 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       OPOF @11, first, I am not advocating not pursuing other sustainability issues.  In fact, I think it is almost as urgent as tackling climate change, possibly more urgent, that we tackle global over fishing.  However, coupling the two issues such that we insist on systemic change to deal with both rather than piecemeal change to deal with each individually will only raise the bar so that we end up dealing with neither.  In contrast, a piecemeal approach has a substantial possibility of dealing with both simultaneiously.

       Second, that piecemeal approaches without systemic change are able to substantially tackle environmental issues is a matter of fact, established by the success of such programs as the Montreal Convention of CFCs, and the wind back of the use of DDT.  Given that, the case that we need to completely alter our economic model to tackle climate change is theoretical at best, and flies in the face of past evidence.  Further, it is advise that can point to no precedent to justify adopting it.  What we do know, however, is that resistance to fundamental changes to our economic system are far greater to resistance to tackling climate change.  Indeed, most resistance to tackling climate change stems from a false belief that it requires changing fundamentally our economic system.  Leaving that aside, however, that resistance to fundamental changes to our economic system is greater than resistance to tackling climate change means tying the two together politically makes the later much harder, and hence much less likely to happen on an urgent basis.

       Third, as it happens, net anthropogenic emissions (excluding LUC emissions) have plateaued over the last three years:

       

       That is probably primarilly due to the significant economic downturn in China, despite world GDP growing strongly.  Despite that, because of China's strong commitment to decarbonization, it is likely that an upturn in China will draw its energy primarilly from renewable resources.  And as is reported in the article above, it is at least partly due to a very strong growth in renewable energy production.

       In any event, that plateau currently means we are tracking on the RCP 2.6 scenario.  Indeed, better than RCP 2.6 in that RCP 2.6 has CO2 emissions continuing to rise until 2020.

       

       Of course, what is required is not just a plateauing of CO2 emissions, but a steady decline at approximately 2% per annum.  For that, however, we need renewables to not just supply new energy requirements (as is almost the case currently), but that it also replace older generation as it goes offline.  International policy settings are not at a stage where that is yet likely, but they are not far off.

24831. KR at 03:41 AM on 28 March 2016
       Global Warming Basics: What Has Changed?
       

       billev - "... No acknowledgement of the pauses..." Nonsense.

       You have been _repeatedly_ pointed to the thread on 'CO2 is not the only driver of climate', where it is clearly shown that the nonlinearity of climate change follows the ensemble of forcings, short term variations, and their summed nonlinearity. There is no reason whatsoever to expect monotonic warming. Your (repeated) claim otherwise is really quite disingenuous.

24832. billev at 03:05 AM on 28 March 2016
       Global Warming Basics: What Has Changed?
       

       What I  see when I observe the available temperature history charts is an upward trend in global temperature but  not continuous warming.  There appear to be significant periods of pause in temperature rise.  I think the pesence of these pauses is an obvious feature in these graphs.  Yet in the several responses to my original comment I have seen no acknowledgement of the pauses.  What I have seen, in fact, is a determined effort to make the pauses disappear.  I have also been cautioned not to focus on too short a period of years while watching some of the responses use the higher temperatures of the most recent couple of years to support their point. 

24833. One Planet Only Forever at 03:01 AM on 28 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       Tom and Glenn,

       I would like to agree with your faith in the likely results if the current socioeconomic political systems governed by 'popularity and profitability' are allowed to continue unchallenged/unchanged.

       However, I would need to see a comprehensive presentation of evidence that subtantively refutes the already developed and established evidence that shows that the current system can be expected to succeed to a very damaging extent in fighting against achieving what is needed to be achieved (fairly obvious when you investigate and think about what is actually going on.

       I understand that you hope that the inherent greedy temptations partnering with the intolerant for support can somehow be kept from wanting to fight against the changes required to address the unacceptability of already fiortunate people continue to get more rewards from the burning of fossil fuels. But I consider such hopes to be unjustified. There is plenty of evidence that there are many wealthy and powerful people who are 'personally not interested in supporting the required changes of what is going on'. Hoping for them to simply give up their attempts to prolong their underserved wealth and power is unsubstantiated wishful thinking. They clearly continue to succeed in trying to prolong their undeserved influence to get away with actions that impede the advancement of humanity, including their successful efforts to drum up divisive in-fighting in a society by trying to make people more passionate in their greed and intolerance, rather than trying to make people more passionate about collectively advancing humanity.

       There is a substantial amount of evidence in many fields of evaluation of the sustainability of developed 'popular' political and economic activity (in far more issues than global warming), indicating that the current socio-economic political systems of 'pursuit of popularity, profitability, and personal reward any way that can be gotten away with' are a damaging unsustainable system that impedes the advancement of humanity (while it promotes self-interested pursuits of personal desires that are contrary to the development of a lasting better future for all).

       Unsustainable impressions can be created and be very popular for a long time, creating more damage the longer they can be prolonged. Faith in the current systems governed by the belief that pursuits of self-interest will advance humanity are clearly misguided. That unjustified faith results in promotion, prolonging and defense of attitudes and actions that can clearly be understood to be contrary to the advancement of humanity to a lasting better future for all.

       The only viable future for humanity is a future where humans are not fighting over limited opportunities for personal reward, a future where all human activity is sustainable parts of the robust diversity of life on this or any other amazing planet.

24834. mark bofill at 01:14 AM on 28 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       Tom Curtis, Glenn Tamblyn,

       I agreed with Tom strongly enough that I registered a login solely to write this / voice my agreement.  You'd call me a contrarian at best, and I've got no intention of engaging over here / hanging around, but seeing this rare case where I agreed with what Tom was saying I thought it was worth the trouble to say so.

       Thanks.

24835. barry1487 at 18:23 PM on 27 March 2016
       Global Warming Basics: What Has Changed?
       

       Getting a handle on the various points you've brought up, billev, would require a reasonable (layman's) grounding in the science. I'm not sure if your views allow room for that kind of patience, or if you are entrenched in them. If the former, there is an excellent site that gives a historical overview of developments in climate science, and gives a good grounding in the fundamental concepts (barring statistical analysis, which you'd need to get info on elsewhere).

       https://www.aip.org/history/climate/index.htm

       This site isn't polemic, just the course of science over the last couple hundred years, condensed and made understandable by a science historian.

       Some of the questions you pose can't be answered in a sentence or two without having a handle on some fundamentals. But if those questions are led by genuine curioisity, there are few better sites to get a grounding on climate science and the history behind the discovery of modern global warming (and past climate changes).

24836. Glenn Tamblyn at 17:39 PM on 27 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       I tend to agree with Tom. While I think our social and economic systems are terminal in their current form, that failure/need for transformation is decades away.

       In the short term, using methods within our current system are the better way to achieve a lot wrt AGW on the short term and in the process prepare the ground for bigger changes. Real Energy Efficiency improvements, complete electriciity from renewables/nuclear and renewable based transport would go along way to breaking the back of the AGW problem.
       
       The current propaganda is trying to paint that as disastrous when actually it is a huge economic opportunity, a net positive, and achievable in the time frame needed if we drive hard at it.
       
       It isn't our economies that are under threat from this, it is the neo-con far right perspective of our economies that is threatened. Keynesian Economics could accommodate this easily.

24837. Crask at 14:47 PM on 27 March 2016
       Ivar Giaever - Nobel Winning Physicist and Climate Pseudoscientist
       

       Kind of like a Biologist who spends all his life studying biology and then decides that he knows whether or not God exists and why people believe in God around the world.

24838. Tom Curtis at 08:52 AM on 27 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       paulswann @7, I am personally very distrustful of proposed solutions to AGW that require us to "radically transform our political and economic systems".  That is not because I am averse to a radical transformation of our political systems (to make them more democratic, while improving education and news media to support that transition), or radically transforming our economic systems (to make them fairer and more sustainable).  But what I am averse to is tying those transformations to the solution to AGW.  IMO that needlessly raises the political bar to action to, in effect, unacheivable levels.

       As it happens, very little actually needs to be done to tackle global warming.  That is despite the requirement to eliminate net anthropogenic emissions within 50 years.  That is because a large part of the transition will be driven by pure economics as (particularly) wind and solar, and energy storage technologies improve.  What is desperately needed now is a clear and persistent price or regulatory framework to drive the transition more rapidly; and to focus the research on improving carbon free energy rather than more innovative ways of extracting and using fossil fuels.  That in turn needs either bipartisan support (in the US and Westminster system countries) or the equivalent in political systems that allow more diverse representation so that reforms under one government are not swept away when the opposition get into office.

       What is needed, and to a large extent, all that is needed, is a global, per capita, tradable, international limits on emissions properly policed; but as I will not make the perfect the enemy of the good, globally implemented carbon taxes, or even accelerated implimentation of Paris style multinational agreements will also do the trick.  Just not as efficiently.  And if we can transform our politics and economics in the right directions at the same time, all well and good.  But that is not a precondition on tackling climate change, and making it so merely delays effective action on climate change.

24839. Hank11198 at 02:05 AM on 27 March 2016
       Welcome to Skeptical Science
       

       Thanks Tom, that helps a lot. 

24840. paulswann at 00:50 AM on 27 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       Tom Curtis & nijelj: in my view (fwiw) the most vital and urgent emissions reducing measure is to ditch the free trade agreements & negotiations (e.g. TTIP/TPP). And there's approximately a snowball in hell's chance of that happening.  

       As this article makes clear, there's no time left for tinkering; either we radically transform our political and economic systems in the very near future, or it could be game over. 

24841. Tom Curtis at 15:40 PM on 26 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       bozza @5, perhaps, but what Hansen and other say, at least in their new paper, should be taken with a large grain of salt.

24842. Tom Curtis at 15:19 PM on 26 March 2016
       Welcome to Skeptical Science
       

       Correction to my @10, the graphs I posted from real climate are specified as forcing adjusted, so they will have used historical forcings for the entire period, but the research was post the IPCC AR5 process, and so I do not know which models were used.  The paper from which the graph originated does not specify in the body of the text, only referring to the CMIP5 ensemble.  That should mean they have used one run only from each of the models used in the CMIP5 project, or almost all of them.  If you want to confirm that, however, you will need to send an email to the lead author, Gavin Schmidt.

       The graph from Zeke Hausfather is definitely stated to use the RCP4.5 extension on the historical forcings.

24843. Tom Curtis at 14:55 PM on 26 March 2016
       Welcome to Skeptical Science
       

       Hank @9, one of the model experiments is the historical forcings up to about 2002.  If you look at the KNMI data, you will see several models have a "historical" run.  However, when running any of the RCP experiments, the model will be run with the historical forcings first before switching over to the RCP forcings about 2002.  Because the RCP forcings do not vary significantly from each other for the first decade, and because of the thermal inertia of the models, the temperature response for all scenarios is approximately the same to about 2020-2030.  Consequently what you are seeing is the ensemble mean for one run per model for the historical forcings to the end of that data, and one of the rcp scenarios (often rcp 4.5) thereafter.  Which precise rcp scenario was used in Tracking the 2 C limit, I could not say.

24844. bozzza at 14:16 PM on 26 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       Hysteresis is the word: what will happen in 40 years, for example, according to Hansen and others?

24845. bozzza at 14:15 PM on 26 March 2016
       Water vapor is the most powerful greenhouse gas
       

       Water Vapour melts ice... it's time to talk hysteresis as some say it takes 40 years for carbon emissions to reveal themelves as the true problem they are hypothesised to potentially be!

24846. Hank11198 at 12:41 PM on 26 March 2016
       Welcome to Skeptical Science
       

       Thank you Tom. What I’m trying to understand is what I’m looking at in your reply to me in comment #3 in the “ Tracking the 2 C limit – February 2016” post. It shows the CMIP5 Ensemble mean along with the actual temperature data from several originations. What was used to make that CMIP5 graph?

24847. nigelj at 08:31 AM on 26 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       I agree with Tom Curtis that we could spend forever debating perfect, globalised solutions. This is like negotiating global free trade agreements, which is very difficult. I think its better to concentrate on practicalities on what can be done to reduce emissions, and countries should do what they think best.

       However first here a few comments on the "idealised solutions."

       A carbon tax does have certain merits as it relies on pretty clear price signals and the tax collected can be used to subsidise lower income people hurt by the tax, or to subsidise electric cars. However the price signal is slow to produce actual results. However a carbon tax is certainly one of the better options.

       Carbon emissions trading schemes are so complex, convoluted, full of loopholes, and subject to very questionable carbon credits that they don't seem workable to me. None have produced good results that I'm aware of. And they take time to see if they are working and the world doesnt have that time.

       I think it makes more sense to simply regulate power companies and oil companies directly and for governments to subsidise electric cars. This covers the big emitters and biggest solutions.

24848. Tom Curtis at 08:06 AM on 26 March 2016
       Dangerous global warming will happen sooner than thought – study
       

       Ronsch @2, while a global carbon tax would be very desirable, it would be difficult to impliment economically, and even more so politically at the moment.  If we are to make progress on climate change, we must not make the perfect the enemy of the good.  That is, we should take all practical steps we can take now, rather than holding out for the ideal solution, but realize that those steps are not a fully adequate solution - and so press for more.

       We ought also to realize that the 2 C target bandied about is not a hard line.  If we fail to achieve it, but keep warming under 2.5 C, we will still greatly reduce the harm done by global warming.  Alternatively, if we in fact keep the Global Mean Surface Temperature (GMST) under 2 C, that will not prevent all harm.  For instance, the Great Barrier Reef is currently undergoing a major bleaching event (as it did in 1998).  This is despite temperatures only having risen to 1 C above the preindustrial (annual average), or 1.6 C on a monthly basis (for February 2016).  That strongly suggest 2 C GMST will be associated with major bleaching events in more than 50% of years, which would effectively mean the destruction of the Great Barrier Reef as a system of reefs.  Other major harms, in some case greater harms, will also occur by 2 C.

       That does not mean politics, especially international politics, is no longer "the art of the possible"; but it does mean we cannot allow that mantra to cloak turning politics into merely the art of the convenient.

24849. Tom Curtis at 07:52 AM on 26 March 2016
       Welcome to Skeptical Science
       

       Hank @7, the CMIP5 ensemble mean, in IPCC usage, is the mean of the values of one run from each model that performed a given experiment in the Coupled Model Intercomparison Project 5 (CMIP5).  The runs for each Representative Concentration Pathway (RCP) each represents a seperate experiment, so there is a CMIP5 ensemble mean for RCP 2.6, and a distinct one for RCP 4.5, for RCP 6, and for RCP 8.5.  The RCPs are not the only experiments that have been done with CMIP5 models, but they are the main ones.

       It is important to realize that not all CMIP5 models have performed model runs for all experiments (not even all RCP experiments), while some models have performed multiple runs in some experiments.  The IPCC restricts the ensemble mean to one representative per model so that those models are not given undue weight, but in some usages that restriction is not applied.  Typically, in those usages the paper reporting the results will specify the models runing the experiment, and how many runs were performed with each experiment.

       Finally, the outcomes of the CMIP5 RCP experiments can be found at the KNMI climate exporer, with all runs performed for each CMIP5 model performing a run.  If you make use of the data, just remember that to obtain the same results as the IPCC you need to select the data for "one member per model" in any category.  Otherwise you will obtain multiple runs for some models.

24850. Hank11198 at 06:57 AM on 26 March 2016
       Welcome to Skeptical Science
       

       Ok I don’t know where to post these questions so I’m trying here.

       
       I have made a few posts and have gotten very good answers that explain a lot. But I am still having difficulty finding the answers to these because the IPCC website is difficult for me to navigate.

       
       Is the CMIP5 Ensemble mean the average of all the different RCP models or an average of something different?

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