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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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Climate Hustle

What does past climate change tell us about global warming?

What the science says...

Select a level... Basic Intermediate

Greenhouse gasses, principally CO2, have controlled most ancient climate changes. This time around humans are the cause, mainly by our CO2 emissions.

Climate Myth...

Climate's changed before
Climate is always changing. We have had ice ages and warmer periods when alligators were found in Spitzbergen. Ice ages have occurred in a hundred thousand year cycle for the last 700 thousand years, and there have been previous periods that appear to have been warmer than the present despite CO2 levels being lower than they are now. More recently, we have had the medieval warm period and the little ice age. (Richard Lindzen)

Greenhouse gasses – mainly CO2, but also methane – were involved in most of the climate changes in Earth’s past. When they were reduced, the global climate became colder. When they were increased, the global climate became warmer. When CO2 levels jumped rapidly, the global warming that resulted was highly disruptive and sometimes caused mass extinctions. Humans today are emitting prodigious quantities of CO2, at a rate faster than even the most destructive climate changes in earth's past.

Abrupt vs slow change.

Life flourished in the Eocene, the Cretaceous and other times of high COin the atmosphere because the greenhouse gasses were in balance with the carbon in the oceans and the weathering of rocks. Life, ocean chemistry, and atmospheric gasses had millions of years to adjust to those levels.

Lush Eocene Arctic 50 million years ago

Lush life in the Arctic during the Eocene, 50 million years ago (original art - Stephen C. Quinn, The American Museum of Natural History, N.Y.C)


But there have been several times in Earth’s past when Earth's temperature jumped abruptly, in much the same way as they are doing today. Those times were caused by large and rapid greenhouse gas emissions, just like humans are causing today.

Those abrupt global warming events were almost always highly destructive for life, causing mass extinctions such as at the end of the PermianTriassic, or even mid-Cambrian periods. The symptoms from those events (a big, rapid jump in global temperatures, rising sea levels, and ocean acidification) are all happening today with human-caused climate change.

So yes, the climate has changed before humans, and in most cases scientists know why. In all cases we see the same association between CO2 levels and global temperatures. And past examples of rapid carbon emissions (just like today) were generally highly destructive to life on Earth.

Basic rebuttal written by howardlee


Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial

Last updated on 6 August 2015 by pattimer. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

Related Arguments

Comments

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Comments 551 to 551 out of 551:

  1. too @550...  Pretty much every point you've stated here is fundamentally incorrect.

    1) Many solutions, in addition to wind and solar, are discussed to address climate change. Nuclear, CCS, efficiency, tidal, geothermal, hydro are all solutions which are being actively worked on and are being actively implemented. 

    2) Researchers provide a wide variety of temperature reconstructions for past temperature. There are numberous local and regional records, and there are a great many multiproxy reconstructions as well. Just because something is "inferred" does not mean that it is wrong. That would be a classic case of throwing the baby out with the bathwater. Just because you don't have absolute precisions doesn't mean you can't trust the information you do have.

    3) What we do know about CO2 concentrations is, they are rising. There is no question about that fact. We know how much we extract and burn in terms of fossil fuels. We know concentrations are rising due to human contributions. There is very high confidence on this fact.

    4) If you actually were to spend any time reading scientific research or listen to what scientists actually say, you would realize that uncertainties are core to the message that they present.

    I suspect that your entire comment is posted here mostly as a means to drive traffic to your personal climate denial blog.

  2. About a month ago, I took the Pages-2k graph (last 2000 years of global temperature using tree ring proxies) and roughly calculated the temperature change per century, last 20 centuries, and the standard deviation in this metric for this 2000 year period.  I then took 5-century intervals from the Marcott graph (last 11,000 years, ocean sediment data), calculated the average temperature change per century (over 5 centuries), and imposed the standard deviation I'd gotten from Pages-2k to each of these to calculate my best estimate of the temperature change per century for the 100 centuries prior to Christs birth.  I then applied this same technique to the Shakun graph (last 20,000 years).  However, in that case I  used 10-century intervals to get the average temperature change per century and imposed the Pages-2k standard deviation upon that average to get 10 data points representing the likely variance over them.  At the end of all this activity, I had 219 data points representing the likely temperature change per century for the 220 centuries (22,000 years) before the 20th century.  The average was 0.014 C/century, the standard deviation was 0.077 C/century, so the 3-sigma point is 0.24 C/century.  Warming in the 20th century was 0.78 C/century.  To me this proves, statistically, that modern warming is nothing like anything that has occurred in the previous 22,000 years.  Its about 3 times what would be considered extremely unusual from the natural record.  And warming in the last 25 years, if it continues, is about 3 times that again (2.2 C/century).  My question is: does anybody know where this kind of analysis has been performed in the Science record?  I'm sure it has, and to a much greater degree.  I just want to know where to find it so I can refer to it whenever somebody claims 'Its all natural'.

  3. Excellent article new at RealClimate: "The climate has always changed. What do you conclude?"

  4. nijelj

    In looking for something else, I just saw this reply of yours on one of the blogs:

    "Your understanding or information is wrong. Sea level rose from AD800 to around 1500 then fell until about 1900, then started rising as in the link below. This correlates reasonably well with burning of fossil fuels so all or nearly all this sea level rise can be attributed to fossil fuels."

    Just curious but does this sea level rise and drop pre 1900 correlate quite well with the theory of the MWP and the Little Ice Age?

    We now have the Chinese study which also seems to support both the MWP and Little Ice Age.  If you need I cite for the Chinese study I can get it for you.

    Again this does not prove anything about the existing warming but the denial of the MWP and the Little Ice Age is part of the "Hockeystick" theory suggesting that this present warming is anomalous over the last 2000 years.

    Response:

    [JH] Sloganeering snipped.

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can and will be rescinded if the posting individual continues to treat adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Moderating this site is a tiresome chore, particularly when commentators repeatedly submit offensive, off-topic posts or intentionally misleading comments and graphics or simply make things up. We really appreciate people's cooperation in abiding by the Comments Policy, which is largely responsible for the quality of this site.
     
    Finally, please understand that moderation policies are not open for discussion.  If you find yourself incapable of abiding by these common set of rules that everyone else observes, then a change of venues is in the offing.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter, as no further warnings shall be given.

  5. NorrisM:

    I am not a moderator here, but I've been around a while. In my interpretation, "sloganeering" is the repeated posting of unsupported assertions, covering the same material, while ignoring comments that have pointed out information that contradicts the assertions.

    You appear to be simply ignoring a lot of comments. SkS also has a rule against "dog-piling", where one commenter is facing comments from a large number of opponents. Regulars here do try to avoid that by restricting comments, but you can help by selected a very small number of posts to comment on, and sticking to those issues until more-or-less resolved, before going on to other topics.

    Response:

    [JH] "Sloganeering" is explicitly defined in the SKS Comments Policy

  6. Moderator.  I would be happy to avoid "sloganeering" if I knew what it was.  I was not using slogans in the part snipped above.  Can you define this term?  You have my email address.  I would be happy to have the definition offline.  There are numerous contributors to this website who present political comment who are not chastised when they make reference to matters which are not factual based.  For example, the discussion of who is and who is not a "denier" and what various subsets there should be of this classification.  Have requested a definition of "sloganeering" before.  Could you provide one?  Thanks

    Response:

    [JH] "Sloganeering" is explicitly defined in the SKS Comments Policy. You have been advised more than once to read the Comments Policy and to adhere to it.

  7. NorrisM,

    For this instance, the data very clearly shows that there was not a global MWP or little ice age.  Since they never existed, they cannot be denied and your comment using the word denied appears to be deliberately offensive.  

    You have previously made statements about the MWP and LIA and have been referred to citations that show they were local events and the global temperature is shown by the Hockey Stick of Mann et.al.  Since you have been shown data to support Mann et al and have provided no data (because it does not exist) to support your claim Mann was incorrect you are sloganeering by repeating an unsupported claim.

    Many scientists have reproduced Mann's Hocky Stick using a variety of methods and data.  It is completely accepted by anyone informed about AGW.  Use the search button to find SkS references to educate yourself. If you have a question we are happy to help you understand, but claiming Mann is incorrect repeatedly makes it appear that you are not reading (or reading and ignoring) the answers people give you.

  8. Michael @557 ,

    please correct me if I have gained the wrong impression : that impression being --

    (A) There was no global MWP, as the numerous "warm patches" of approximately 1,000 years ago were Northern Hemispheric and were minor and not contemporary.  In other words, the so-called MWP is nowadays a Eurocentric "beat-up" from denialists who are using outdated ideas and who are being very economical with the truth.

    (B) The so-called Little Ice Age actually "was a thing" : as it involved some cooling of both hemispheres (IIRC, caused by two Solar Grand Minima, helped along by a number of above-average volcanic eruptions).   Also IIRC : the Little Ice Age was a rather minor affair, constituting a global temperature drop of only about 0.3 or 0.4 degrees below the natural long-term (multi-millennial) slow decline of global temperature [until the modern rapid "Hockey Stick" rise caused by AGW, of course!].

    I often see denialists claim that the temperature rise of the 1800's and 1900's was nothing more than a "rebound effect" from the LIA.  That argument seems [to me] to be a complete nonsense, since recent temperatures are higher than the extrapolated pre-LIA levels (and the Holocene temperature is on a natural down-curve).  And those denialists are supposing that any changes in global climate simply occur for no physical reason.  Perhaps they subconsciously think of global climate as being a sort of inner-spring mattress!

  9. Eclectic:

    Another weakness of the "recovery from the Little Ice Age" meme is that the Little Ice Age ended a long time ago (in weather terms). Such a "recovery" should be fast in the early stages, and proceed more slowly as it appraoches the state it is recovering to. It wil not, without some magical physics, proceed slowly at first and continue to "recover" at faster and faster rates later on. If the current warming is "recovery from the Little Ice Age", why didn't it recover two hundred years ago?

    Tha magical physics of the "Recovery" meme requires that whatever caused the Little Ice Age must proceed very quickly to create the Little Ice Age, but removing tha cause must proceed very slowly to get us back out of the Little Ice Age.

    Such physics is not impossible - c.f., adding CO2 to the atmosphere by burning fossil fuels causes a rapid rise, whereas the atmospheric CO2 will not drop rapidly if we stop burning fossil fuels. We have a good physical explanation for that behaviour, though. The "recovery from the Little Ice Age" meme has no such physcial explanation, however, as you point out.

  10. Eclectic,

    Bob Loblaw's comments are always thoughtful.

    Your understanding of the MWP and mine are much the same.  There were various warm and cold periods worldwide but they were not all at the same time.

    According to Mann's Hocky Stick from this SkS reference:

    Hockey Stick

    Where is the drop in temperature for the LIA?  I do not see any noticable drop between 1600 and 1900.  There is an overall drop over the entire graph (the Hockey handle) that is probably the descent into the next Ice Age that was stopped by CO2 emissions.  As you would expect, there is some noise.

    Since I see no special "LIA" I conclude that it never existed.

    I see that the above graph confirms Mann's original Hockey stick as very close to the best data available ten years later. 

  11. Moderator

    Thanks, I have now read your Policy Statement.  I would have thought that my references to nigelj's comments re ocean temperatures (on another stream) somewhat corresponding to the periods "alleged" to be the MWP and the Little Ice Age would be considered  "additional information" and not just repetition of earlier positions.  Surely a matching of ocean temperatures tells you something about atmospheric temperatures at the same time.

    Furthermore, my reference to the recent Chinese Academy of Science recent paper analyzing temperatures over the last 1,000 years in China was also something which shows that this was not just a period isolated to parts of the Northern Hemisphere.  Does anyone have any comment on this?  I have read somewhere else (and I do not have a citation) that during the MWP the tree line of the Rocky Mountains was much higher than at other times.  This would just about "connect the dots" for all of the Northern Hemisphere since we have Northern Europe, Greenland, Newfoundland and China already.

    The above graph has posted the Michael Mann 1998 hockey stick.  My understanding is that sometime around 2007 he revised his graph.  Could someone post his most recent one?  For some reason, I thought it was not so "flat".  Perhaps because it does reach back further than 1400 to cover the period from 800 AD.  If this is totally "out of the blue" with reference to the Rocky Mountain treeline,  I will find my source for this statement or acknowledge that I cannot find it.  However, my guess is that you have heard this before.

    I will again reiterate that even if there was an MWP, it does not prove anything about today's temperatures but only goes to show that this has occurred before when it was not caused by man.

    Response:

    [JH] Please provide a link to the Chinese Academy of Science paper that you have cited.

  12. Norrism,

    This is the graph for the Northern Hemisphere from Mann et al 2008 :

    There might be a more recent paper that I did not find.  Mann has done the analysis with no tree ring data and it is the same as with the tree ring data.

    It is usually possible to get free copies of papers if you Google them (I found this paper using Google). Apparently it is only for the Northern Hemisphere (as was the other graph I posted). More data is available for the Northern Hemisphere so Mann only did the Northern Hemisphere in 1998.

    Here is a global analysis by Marcott et al  (SkS article about Marcott)

    marcott in red

    Marcott is the red line.  The small bump up is around 1000 years ago and is too early for the MWP.  Current temperature is about 1.0 on this graph.

    Keep in mind that we expect the temperature to decline after the Holocine maximum to a new ice age.  This is the decline from 5000 bp to 150 bp.  AGW then kicks in in earnest.  AGW might have slowed the decline in temperature from 5000bp on from early farming releasing CO2.

    I see no indication of a MWP in any of this data.

  13. NorrisM @554,

    You sepcifically ask about the reference made in a comment on another thread which concerned data from Kemp et al (2011) and a Sea Level reconstruction used to make a comparison with the good-old hockey stick. The actual graphic shown was::-

    Kemp et al reconstruction

    The fit with the hockey stick only works back to AD1000. Simplistically, the SLR found by Kemp et al is saying that (if the SLR is the result of global temperature changes) the temperature was in balance with sea level up to AD1000 after which average global temperatures rose by about 0.15ºC, a level maintained for a period of 400 years, then dropped back for a period of 500 years, after which we have the instrument record showing a global rise of 0.5ºC to 1950 and a similar rise since. So any MWP & LIA are globally very tiny features relative to post-AD1900 warming.

    An alternative is that globally temperature was much flatter with the SLR resulting from regional temperature variation in places that SLR would be sensitive to; places like Greenland perhaps.

  14. NorrisM & Michael Sweet:

    Please take any further discussion of the Medieval Warm Period to the thread of the SkS Rebuttal aricle, How does the Medieval Warm Period compare to current global temperatures?

  15. If I may beg JH's indulgence for a moment, to make a general point about both the Little Ice Age and the MWP issue :-

    I hope that readers [including NorrisM] can see, in total Holocene perspective, that the LIA & MWP (if discernible at all) are very tiny ripples in global temperature compared with the huge rise which is AGW.    And that neither MWP and/or LIA supply any valid argument against the size/severity & anthropogenic causation of the recent global warming. 

  16. Moderator

    Here is the cite requested:

    Advances in Atmospheric Sciences, August 2017, Volume 34, Issue 8, pp 941–951
    Quansheng Ge et al., Chinese Academy of Sciences


    Abstract
    This paper presents new high-resolution proxies and paleoclimatic reconstructions for studying climate changes in China for the past 2000 years. Multi-proxy synthesized reconstructions show that temperature variation in China has exhibited significant 50–70-yr, 100–120-yr, and 200–250-yr cycles. Results also show that the amplitudes of decadal and centennial temperature variation were 1.3°C and 0.7°C, respectively, with the latter significantly correlated with long-term changes in solar radiation, especially cold periods, which correspond approximately to sunspot minima. The most rapid warming in China occurred over AD 1870–2000, at a rate of 0.56° ± 0.42°C (100 yr)−1; however, temperatures recorded in the 20th century may not be unprecedented for the last 2000 years, as data show records for the periods AD 981–1100 and AD 1201–70 are comparable to the present. The ensemble means of dryness/wetness spatial patterns in eastern China across all centennial warm periods illustrate a tripole pattern: dry south of 25°N, wet from 25°–30°N, and dry to the north of 30°N. However, for all centennial cold periods, this spatial pattern also exhibits a meridional distribution. The increase in precipitation over the monsoonal regions of China associated with the 20th century warming can primarily be attributed to a mega El Ni˜no–Southern Oscillation and the Atlantic Multidecadal Oscillation. In addition, a significant association between increasing numbers of locusts and dry/cold conditions is found in eastern China. Plague intensity also generally increases in concert with wetness in northern China, while more precipitation is likely to have a negative effect in southern China.

  17. NorrisM @566 , thank you for pointing out the Chinese multi-proxy historical data study, published only 5 weeks ago (and receiving a mention last month in WattsUpWithThat & other websites too).

    I haven't accessed the full paper, but the Abstract & Conclusion & a temperature chart (per the Chinese Academy of Sciences).

    There were two noteworthy temperature rises shown in the China region, peaking at around year 1100 CE and the second at around 1250 CE.  The peaks were (respectively) 0.4 degrees and 0.5 degrees above the 1851-1950 mean.  In other words they were quite low relative to current world temperatures.   And judging per my eyecrometer, those and the other minor peaks/troughs show only small excursion (from the mean) and showed rather poor temporal correlation with the Mann et al (2008) peaks/troughs — but of course I would be happy to bow to a more rigorous mathematical analysis of that point.

    All in all, there seems to be nothing very startling (or upsetting to mainstream climate science) in the new Chinese study.  Even the "quick to trumpet incompatibilities" WUWT has had little to say about it; and nor was there anything insightful/intelligent/relevant to be found in the attached WUWT comments column [ but no surprise there  ;-)  ].

    As I mentioned in post #565, neither the LIA or MWP "ripples" can detract from the AGW tsunami.

  18. NorrisM, Electric & Michael Sweet:

    Please take any further discussion of the Medieval Warm Period to the thread of the SkS Rebuttal aricle, How does the Medieval Warm Period compare to current global temperatures?

  19. Please answer this hypothetical for me.   If we stop all human CO2 emmisions tomorrow would the temp at some point warm the earth to the critical stages it has done in the past?  Am I right to understand that the polar caps have for the most part melted in the past?

  20. Scott, the first important thing to understand is that climate is a reflection of the energy balance. If that changes for any reason, climate changes. Climate does not change by itself. CO2 was much much higher in the past, but the sun was fainter. We only got polar caps when CO2 dropped below a level for it to get cold enough. In the Pleistocene, CO2 dropped to point where the slow orbital cycles (Milankovich cycles) could drive an ice-age cycle due to variations in insolation happening at around 65N. Before that (the last time we had CO2 above 400ppm), you had icecaps but not ice ages.

    Could they melt again? They will. The sun as a mainline star, is very slowly increasing its output and has been doing so since formation. At some point, a billion or so years into future, it will be too hot for liquid water. Eventually, as its fuel is exhausted, the sun will expand and probably consume all the inner planets - 5 billion years into future from memory.

    A volcanic eruption on the scale of the Deccan traps could also push so much CO2 out that it warms the climate though that might be the least of our worries.

  21. Scaddenp, so what you are saying is if we completely eliminate human CO2 emissions we could send ourselves into another ice age? Or am I oversimplifying the issue?  If there is one immutable truth it would be that human intervention on mother nature is usually dangerous.

  22. Scott0119 @571 , clearly you need to do a lot more reading to educate yourself on climate matters.  Undertake some "science 101" basic education.   Examples : read the climate science summaries on the websites of the U.S. National Academy of Sciences; of the U.K. Royal Society; of NASA; of NOAA; of the American Geophysical Union; of the Pontifical Academy of Sciences; or of other Societies of eminent scientists.  If you prefer a more piecemeal approach, then select a few of the Climate Myths (see via the top/left corner of the SkepticalScience home page) — and read a number of them that interest you particularly [like with delving into a dictionary, you will soon find "nearby items" which will also interest you].

    The "truth" which you quote may be less "immutable" than you think : but you are certainly correct that "human intervention on mother nature" [by injecting 100's of Gigatons of fossil-origin CO2 into our atmosphere] is definitely proving to be dangerous.  It is high time that we all woke up to that !

  23. If we completely eliminate CO2 emissions, CO2 concentrations and temperature will continue to rise for some time, because once temperature starts to rise by any cause, all the natural feedbacks that amplify the ice-age cycle still cut in. Detail on our commitments here though carbon-cycle feedbacks are still major research topic. Because they are slow (hundreds of years), they dont affect our immediate future.

    CO2 that we have already emitted stays there. There are very slow processes (millions of years) that gradually pull CO2 from the atmosphere. If we every needed to warm the planet, then very easy to make extremely powerful GHGs that would warm the planet again far more efficiently than CO2, but on those long time scales, you have to remember the changes in the sun too. Too many generations away for me to be much concerned.

    Couldnt agree more about danger of humans interfering with mother nature. Our unplanned change in atmosphere concentration is biting us.

  24. @ eclectic@572.  "clearly" that is why I am here.  I know these questions may seem uneducated but if memory serves from my School years if you don't know something ask.  

    @ scaddenp @573 thank you for your answer.  You seem to have a grasp on teaching.  

  25. Scott0119 @574 etcetera : Quite so.  There's no such thing as a stupid question per se, yet a poorly-worded question may give the impression that the questioner is being disingenuous or subpontine in intent.  Especially so, in the context of making contemporary statements in other threads, giving a similar impression.

    Cast your mind back to your School days, Scott, and you will recall that you were expected to do your basic homework.  And picture what your Science teacher's opinion of you would have been, if you had skipped doing your homework, and you had then declared that you "were not yet convinced that the globe is round".  Or if you had expressed similar baseless doubts about similar well-established facts.

    Do your basic homework first, and then you will be able to ask intelligent questions.  That makes for the most efficient use of your time.  SkepticalScience is an excellent (indeed, award-winning) repository of scientific information.  Read.  Think.  And you will find there are very few questions that you need to ask.  Any clarifications needed — and excellent teachers such as Scaddenp are happy to help answer a genuine question arising from your "homework".

  26. Scott0119,

     You asked, "if we completely eliminate human CO2 emissions we could send ourselves into another ice age? Or am I oversimplifying the issue?"

    According to this paper published in Nature: Evolution of global temperature over the past two million years , judging by the fossil record it appears as if we are locked into continued warming for a while at least even if we stopped all fossil fuel use tomorrow. Earth 'Locked Into' Temperatures Not Seen in 2 Million Years (all else equal of course).

    However, all else need not be equal. Humans being a tool using species have the ability to do great works of ecosystem healing just as easily as we can do great works of destruction. In this case it means we have the knowledge tools and capability to sequester rapidly in the agricultural soils of the world more than enough carbon to "unlock" that "locked in" scenario.

    Simply eliminating fossil fuels completely won't stop AGW. We waited too late for that. Sequestering carbon in our agricultural soils world wide by itself is probably too late for that too. But doing both ? That actually can finally reverse AGW, and such draconian measures need not be necessary. We could still burn a little fossil fuels and still have some ag that isn't carbon farming. In other words if we approach this from all angles we can drop it in as a replacement to all our unsustainable systems where economically feasable and the problem would vanish...and at a net economic profit!

    I have written a rough outline essay how that might work here: Can we reverse global warming?

    Here is a description of both the challenges and solutions we are facing in US: Can American soil be brought back to life?

    Here is the same basic concept as developed in Australia: FARMING A
    CLIMATE CHANGE SOLUTION

    and

    Why pasture cropping is such a Big Deal

     

    And here is the Chinese efforts and early results for the same concept:

    “Grain for Green” driven land use change and carbon sequestration on the Loess Plateau, China

     

    Executive summary:

    Yes we can reverse Global Warming.

    It does not require huge tax increases or expensive untested risky technologies.

    It will require a three pronged approach worldwide.

    1. Reduce fossil fuel use by replacing energy needs with as many feasible renewables as current technology allows.
    2. Change Agricultural methods to high yielding regenerative models of production made possible by recent biological & agricultural science advancements.
    3. Large scale ecosystem recovery projects similar to the Loess Plateau project, National Parks like Yellowstone etc. where appropriate and applicable.

    Either way though, a glaciation event is not in any forseeable future. Quite the opposite problem.

  27. First, please note that I'm a skeptic of AGW theories. I believe that at best, Mankind may have the capacity induce a relatively minor impact relative to the sources of natural variation.

    Holocene is considered an Ice Age with the last Glaciation endingn ~11K to 12k years ago. I don't know the catalyst that shifts from an 'Ice Age' to a 'Warm House'. (Need to research that) We do know it has happened many times before our arrival. 

    Looking at temprature records of the 12 Periods in the current Era, 84.7% of the time the Globe was several degrees warmer. It seems logical to assume the planet tends to gravitate to that level with ouside events triggering major cooling events. 
    Consider:
    84.7% of the Phanerozoic Eon was on average ~3+ degrees warmer than current. 
    Holocene is considered an Ice Age. (Something cooled things off, but the planet is trying to return to its 'normal' balance which is closer to that 84.7% of the time level.)
     
    Is it possible the current Ice Age has ended due to some factor we have not yet considered? 
    What I am really asking is; How many global climate factors are there that we have we do not yet fully understand? How big could their impacts be? What is the likelyhood that there are significant factors that we do not yet understand and or have not discovered. 

    I'm an AGW skeptic because I find it difficult to accecpt that only 0.03% of the atmosphere is responsible for controlling changes in Global Climate.
    Statistically speaking: 0.0003 could be viewed as a rounding error. (This point is for dramatic effect only) 

    The planet is warming. On this we all agree.

    Response:

    [TD] The percent of the total atmosphere that is CO2 is irrelevant. The only gases that are relevant are greenhouse gases, of which CO2 is one. With regard to forcings, there are even fewer relevant gases; water vapor condenses so it is a feedback, not a forcing. So a relevant percentage is the percent of all non-condensing greenhouse gases that is CO2.

    There is overwhelming, concrete, empirical evidence for an increase in CO2 causing warming.

    Human activities' contributions of CO2 to the atmosphere are not balanced by human activities' removals of CO2 from the atmosphere. In contrast, the natural contributions and removals closely balance. CO2 is removed from the atmosphere by natural processes very slowly, so human contributions accumulate.

    [PS] Please note that Sks organizes arguments into different topics. Please do not make offtopic comments. Use the search button on the top left to find relevant topics and comment there after you have read the article. Repetition of long-debunked arguments is boring.

  28. jop3v2 @577,

    Concerning your self-description "I'm an AGW skeptic because I find it difficult to accecpt that only 0.03% of the atmosphere is responsible for controlling changes in Global Climate." Consider the following analogy:-

    I live in a house that I estimate contains about 60 tons of material in the walls (333mm x 3m x 10m x 4walls with sg =1.5). The atmosphere contains today 400ppm by volume and 610ppm by weight of CO2, or 0.06%. Studies suggest that if CO2 were entirely removed from the atmosphere, the greenhouse effect would effectively disappear and global average temperatures would fall 33ºC. There are a lot of things that result from the removal of atmospheric CO2 (as described in the linked SkS article) so the analogy with my house is not exact. Also note the planet's troposphere contains a 75ºC temperature drop while the inside/outside temperature difference across the walls of my house is no more than 20ºC, even in winter. So consider if I take the front door off my house in mid-winter. There will be a dramatic change in the room temperature, very likely reducing the average inside/outside temperature difference by more than 50%. If the front door weighs 36kg, it would constitute 600ppm by weight of the house. (It probably weighs a lot less.)

  29. jop3v2 says "The planet is warming. On this we all agree."

    Actually, no. I have been around the mind manipulation wars on climate for a good number of years. There are countless fake skeptics who in fact disagree with that and have made a living of attempting to spread doubt about that very point. Most famously, Anthony Watts, who was proven wrong in his assumptions very early on by an amateur going by the handle of John V. He was proven wrong again later by NOAA and finally by his own publication. It was a fairly inconsequential paper, that still took him years to produce; it did not lead him to disavow his years of accusations of fraud against others, encouraging his readers to harass scientists by putting their personal addresses on his site, or putting up posts so grotesque that only the scientificaly illiterate could take him seriously (Antarctica carbonic snow comes to mind). And he is only one of many; some are in the highest positions of power. Your concluding statement is verifiably wrong. Perhaps you should have said: "we, people amenable to reason, all agree with that." I would concur if phrased that way.

    Another part of your argument to which I object is the "humans too small to affect anything." It is common and sometimes comes from people who are religious minded. However, it is not valid either. Imagine all the carbon dioxide released from volcanic activity happening naturally on Earth over a year. Now, multiply that by approximately 100 (give or take); that's how much we have been and are still releasing, year after year. Any argument that this does not constitute a geological scale event is wrong, purely from simple quantitative considerations. Geological scale events have geological scale ramifications.

    The per volume fraction of CO2 is seemingly small, but that does not change the physics. If CO2 was not transparent to visible light and we could actually see its increase just by looking at photos of now vs 35 years ago, we certainly would be more enclined to take the threat seriously, because that's the kind of animal we humans are. We also are very bad at anything truly long term, although this has become far worse in the recent past, under the pressure of an extreme ideology of maximizing short term gains at any cost, present or future.

    There is more to discuss about the fact that we weren't around as a global civilization in the time periods you mentioned and that we developped as such in a certain range of conditions; we then built some pretty heavy infrastructure that is already compromised by rapid seal level increase. We established industrial agricultural practices that, for all their machinery and chemical underpinnings, are nonetheless most dependent on rainfall, seasonal cycles, and low probability of extreme events. The rapidity of the change we are witnessing now is far more relevant to us than the actual position of equilibrium in a past when we were just tagging along with all the other critters.

    Response:

    [PS] can I ask all responders to jopv32 to reply on an appropriate thread? You can place a pointer to your reply here.

  30. In a relatively recent study by Kemp, Eichenseer and Kiessling, the authors argue that the change in climate may have been faster (maybe as fast as now) before, but this can't be seen in the data, since most data only refers to long time intervals.
    (https://www.nature.com/articles/ncomms9890)

    Is there a response to that? What is your opinion on that study?

  31. Abrupt global warming in the Permian and Triassic periods were associated with higher CO2 levels. Climatologists speculate on the reasons for the sudden increase in CO2 levels, but obviously during those time periods the increase was not human induced.  This fact is a crucial and painful one for the "consensus" who argue that our current (slight global warming) trend is man made.  To assume an unknown (the imprint of human activity on our climate) over a known (Historical data proving our climate has changed with increases and decreases in CO2) is a lazy stance for scientists to take.   

    Response:

    [PS] Please provide a citation to support your statement "To assume an unknown (the imprint of human activity on our climate) over a known (Historical data proving our climate has changed with increases and decreases in CO2) ".

    ie show us where science has made that assumption rather than deducing it from known and testable physics.

  32. Cero,

    I read the article you cite.  I noticed that they first claim that it is not possible to measure the rate of climate change in the distant past because of inherent problems with the samples.  Then they claim to adjust measured data to correct for these random changes.  That is a contradiction to their first claim.

    They have only been cited 4 times by other scientists.  It appears that other scientists think the paper is not very valuable.  It appears that deniers cite this article.

  33. Rodhole,

    Since people died before guns were invented, according to your logic guns cannot kill people.  If the CO2 concentration increase is not caused by humans, where is all the CO2 we release into the atmosphere going?  A simple measurement shows that the increase in CO2 concentratio only accounts for half the CO2 we have emitted.  The rest dissolved into the ocean.  In order for your claim that the increase is natural to be true you must show where the CO2 we emitted went and where the CO2 icrease in the atmosphere sent.

    In addition, there are chemical means to show the increase in CO2 is human caused and not natural.

    Deniers are so lazy they cannot even be bothered to do addition and subtraction.

  34. Sweet,

    No, guns actually CANNOT kill people.  Guns are man made and need a conscious handler in order for them to activateBut I would assume then that you would argue that because people have used guns to kill others, the real problem lies with the gun manufacturersI guess it would depend on the amount of emissions released during the making of a gun to guide your opinion.   

    My point is not that emissions caused by humans is irrelevant.  I think it is something that we should be responsible with (without losing our minds and/or implementing stupid laws that hurt our economy)My point is that it is arrogant to believe that after millions of years of climate change, certain scientists insist that "this one" is bc of humans

    Whether these scientists truly believe the human race was not meant to live on this earth (bottom line of debate), they fear being an outcast in the science community (reality), or they are  getting incentivized to postulate an agenda (my assertion), the latter 2 of the 3 is wrong.  

    Response:

    [DB] Welcome to Skeptical Science.  First, the ground rules for this venue are found in this site's Comments Policy.  Read them.  Learn them.  Construct future comments to comport with them.  Attempting to score meaningless rhetorical tricks employing logical fallacies that also show a large ignorance of the science in question in specific and the scientific method in general, as you do here, reflect poorly upon you and damage your credibility in this venue.

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.

    Multiple inflammatory, sloganeering and ideological talking points and logical fallacies snipped.

  35. Skeptical Science,

    Being new, I was not aware of the rigorous monitoring of the rules.  Regardless, that was a perfectly fine rhetort to the post "attacking" my assertions.  Am I not allowed to defend my comments?  Why didn't you strike her initial comment on guns?  Do you just outlaw things (especially if it makes your cohorts look bad) that you don't agree with? 

    One thing I learned in college is to have an open mind and allow others to voice their opinion.  Unfortunately these days opinions that don't comform with the "consensus" are dismissed.  I hope this cite does not only allow things it agrees with.  If it does, than this not a place for thoughtful discussion, rather it is a place of pretend fantasyland. 

    BTW, I didn't know what it meant so I had to look up "sloganeering".  I laughed bc this entire comment section is "sloganeering".  

      

    Response:

    [DB]  FYI, the Comments Policy applies equally, to all.

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can and will be rescinded if the posting individual continues to treat adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Moderating this site is a tiresome chore, particularly when commentators repeatedly submit offensive, off-topic posts or intentionally misleading comments and graphics or simply make things up. We really appreciate people's cooperation in abiding by the Comments Policy, which is largely responsible for the quality of this site.
     
    Finally, please understand that moderation policies are not open for discussion.  If you find yourself incapable of abiding by these common set of rules that everyone else observes, then a change of venues is in the offing.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter, as no further warnings shall be given.

  36. Funny that you didn't publicly post the rest of what I said?  I get it, you are scared of intellectual confrontation.  This will be my last post on this fake cite.  

    When you go to sleep tonight, think about how dishonest this cite is.  You are so frightened by differing opinions (which happen to be based on science and data) that may make you wrong, you choose to cut those people off rather than let them speak.  It is a common liberal playcall, so I am not surprised

    I'll let you continue your shameful dominance over the realm of scared dorks who dont want to break a rule, while I continue to have open and honest conversations with people.  From my experience in talking with people over the last 20 years, the farse of "man made global warming" is declining by the day.  Al Gore's bank account is not happy I'm sure.          

    Response:

    [DB] I'm sorry, that your position is so weak that you are unable to bring any actual evidence for your position to this, an evidence-based site.  I'm further sorry, that you feel compelled (like a moth to a flame) to repeatedly violate a code of conduct that well over 99% of participants here routinely adhere to with no difficulties whatsoever.

    As for your remaining comment, even Exxon affirms the unassailable evidence, consensus, facts and the alarmist "farse" of AGW:

    "The risk of climate change is clear and the risk warrants action. Increasing carbon emissions in the atmosphere are having a warming effect. There is a broad scientific and policy consensus that action must be taken to further quantify and assess the risks."

    Exxon's Position Statement on Climate Change

  37. Rodhole @586 , I am sure that genuine intellectual "confrontation" (from you?) would be welcomed, if you care to accompany it with some well-reasoned factual basis.   But this site [please note correct spelling] is very uninterested in receiving moronic confrontation even without multiple spelling errors and factual errors, which you exhibit.   Nevertheless, I acknowledge and bow to your immense superiority.

    Moderators — as always, please feel free to delete my post, if you feel the pruning shears are called for, in this thread!

    Response:

    [DB] Inflammatory snipped.  As you note, all who bring credible evidence for their position and comport themselves with the Comments Policy are welcome here.

    Rodhole has recused himself from further participation in this venue.

  38. @michael sweet:

    I don't think, they claim, that it is not possible at all to measure the rate of climate change in the distant past, but they claim that the conclusions from the data are much less accurate than is commonly believed. Therefore it makes sense to correct for that.

    They only have been cited 4 times, however the article is only two years old. And maybe they just didn't get that much attention. Still, the article was published in a well-known peer-reviewed journal.

    That climate change deniers cite this paper can't be an argument against its validity.

  39. cero @580,

    I can see Kemp et al (2015) being drooled over by denialists. This would be because they misinterpret the paper which sadly misses out on saying explicitly things that are obvious in any genuine reading of the paper.

    The idea that ancient warming episodes may have contained more rapid events within the actual warming, that the average rate of warming will inevitably be exceeded over shorter sections of that warming: this is logical. And when you are concerned how quickly, say, an oak forest habitat can shift polewards, those speedier intervals are relevant.

    As Michael Sweet points out, we cannot (yet) measure such short accelerations from the available data so Kemp et al set out a new method to infer those increased levels. This is interesting stuff, and very early days, so it cannot be seen as entirely reliable. Consider the PETM which we know took millennia to occur. It was a gentle warming over a long period and would have had periods of increased and decreased rates of warming. Thus Kemp et al take central estimates for this event (5ºC to 9ºC = 7ºC, ~5ky to 20ky = 12.5 ky, this a rate of warming of 0.0006ºC/yr compared with recent rates of 0.015ºC/yr ) and adjust these to suggests a potential millennial rate of 0.0032ºC/yr or about half the PETM warming occurring in a single millennuim.

    Other measured temperature rises are likewise adjusted. A 15ºC measured ocean warming over 800,000 years during the P-T (250My bp) is inferred to include a millennial period of at least 4.5ºC warming. (Potentially we could deduce a 9ºC warming over 2,000 years.) Or the Bølling-Allerød during the warming from the LGM (13,000yr bp) measured at 3ºC over 100 years is adjusted to equate to 2.2ºC over a millennia.

    So I am on safe ground when I suggest that Kemp et al have not begin to capture the scale of that adjustment. They have set out a method that begins consideration of it.

    But there is a missing aspect within the paper if it to be used to argue about the rate of AGW relative to previous non-anthropogenic warming. We are facing a temperature rise of 4ºC in a little over 100 years from  unmitigated AGW. Such a rise would rival the magnitude of the largest millennial warming set out by Kemp et al. The caution Kemp et al say "must be exercised when describing recent temperature changes as unprecedented in the context of geological rates" does not apply to expected future unmitigated temperature changes.

  40. Answer is: whether it's going too fast or not!

    (Did I win?)

  41. Thanks @MA Rodger. That was the kind of explanation I was searching for. :-)

  42. Recommneded supplemental reading:

    The climate has changed before. But this is different – look at the archeological record by Peter B Campbell, Guardian, Nov 9, 2017

  43. The Campbell article John Hartz mentioned is well-written but doesn't present a lot of historical or archaeological evidence, and the conclusions to me seem understated.

  44. According to SkS's database this, 'Climate's changed before' is by a slight margin the most popular 'argument' used to protect against 'alarmism' (or action, whichever way you see it).

    In the taxonomy, it's listed as a subead of 'It's not us', and this is the usual implication of 'no one denies the climate changes' by committed contrarians - they may go on to assert there's some (unknown) mechanism causing the current rapid warming instead of the predicted enhanced greenhouse effect.

    However I would like to suggest that the conclusion reached from 'climate always changes' by most people fits more under the 'It's not bad' top-level heading.  howardlee's 'rebuttals' address to an extent by talking about rate of change and past impacts, which are factual points. 'It's not bad' is not purely factual, because 'bad' is a value.

    What I mean is that people will use weather, weather ranges, historical climate variations, glacial cycles over human development, or geological records back to the Precambrian to assure themselves, in combination with the self-evident fact that 'we are here', that civilisation, human life or life itself is more 'resilient' than fragile to substantial temperature or CO₂ changes.  If it's happened before then it can't be too bad and is not worth regretting. Again, this stance is as much based on values as facts, as described in Mike Hulme's Why We Disagree About Climate Change. Possibly individualists think nature is less unstable than do egalitarians, although that link wasn't immediately obvious to me.

    You can also see a ethical evaluation being superimposed in data when discussing 'dangerous' thresholds, for example J. Hansen et al.: Ice melt, sea level rise and superstorms.  What are the dangers? Although these are detailed in the IPCC WG2 reports, in some ways it's sketchy precisely because these are unprecendented changes or rates of changes.  Very few think a runaway effect that destroys all life on Earth is likely, so anything less is a kind of survival, and it's possible to 'concertina' geological time with possible changes in frequency recent extreme weather events without fully appreciating what a mass extinction means.  A few metres of sea-level rise has happened before, and if it happens over 200 years then it isn't the end of the world.

    Largely I think these are still tacit positions when people seem to be discussing topical issues, but they are things on which scientific research and reason can be brought to bear.  We can make partial projections based on past evidence of harms and benefits, such as at the Royal Society meeting on hyperthermals.  But the possibility of unexpected dangers are harder to evaluate, and most people may assume the existence or otherwise of precedents is the only way to decide whether climate change is a bigger environmental problem than habitat fragmentation or plastic pollution, or how the amount of human endeavour to mitigate it necessary for long-term survival compares to that put into education or defence.  Integrated Assessment Models are not the only way one can form an opinion on what the carbon price should be. 'Lukewarmers' presumably hold these kinds of thoughts along with a historical knowledge of previous millennialism and mass hysteria to evaluate the current situation, while others passively dismiss climate concern using similar reasoning.

    So there may be several related deeper objections or questions where SkS can summarise evidence. These may often underlie the search for, or adherence to, pseudo-scientific arguments used by contrarians.  I may post again on what these are specifically.

  45. Cedders @ 594

    As one who is clearly a "lukewarmer", at least, I will look forward to any further posts you have while I personally try to get a handle on issues relating to the measurement of sea levels and actual measurements of global temperature rise. 

    My underlying concern remains that that the climate system is so complex that the models cannot adequately predict what is going to happen (yes I know this is the topic of another thread)It does not mean it is not going to happen but to ask the world to shift its FF use over a very short time frame is a hard sell.  Perhaps you can deal with this in your suggestions to SKSAnother suggestion I have made to SKS (which seems to have fallen on deaf ears) is to address the alternatives and their cost to assure the Republicans in the US (which is surely what has to be done) that there is a reasonable alternative.  I understand that this website is not dedicated to those issues but, in my view, those are so critical to convincing the public that they have to be addressed in one or more formal threads dedicated to same.  

    Response:

    [DB] Off-topic snipped.

     

  46. "First, to infer that humans can't be behind today's climate change because climate changed before humans is bad reasoning (a non-sequitur)."

    Nobody suggested this, not even in your quote. We're just saying that the whole concept of climate change being a problem is ridiculous. Because the climate always changes, by definition. Too fast climate change might be a problem. Humans breath out CO2 and breath in Oxygen, of course we affect our environment. Nobody disputes that. Please stop with the straw-men arguments. We're just saying that there's no reason to assume change is necessarily bad. We have to do actual science instead of fear mongering.

    "Second, to imply we have nothing to fear from today's climate change is not borne out by the lessons from rapid climate changes in Earth's past."

    When archeologists say 'rapid', they mean thousands to hundreds of thousands of years. When the collection of species in an ecosystem changes it sounds really bad. Suggesting that all the animals normally just live their happy lives, but with such a change they all suddenly die. This is not how reality works. Animals struggle to live their most of their life. An environmental change that causes the species to change just means some species become a little less successful at that every year and some a little more. So an individual animal probably won't notice the difference.

    Response:

    [PS] "We're just saying that there's no reason to assume change is necessarily bad. We have to do actual science instead of fear mongering." Yes, lets indeed to the science. You can find that science summarized nicely in WG2. You will also find the scientific answers to of many of the myths about rapid change here under the section "Its not bad". Your concluding statement is sloganeering, because you are making assertions without providing supporting evidence in the face of established science.

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