April 27, 2013

The "Pause" in Global Warming: What Does it Mean?

The media mentions it frequently and global warming skeptics talk of little else:  the fact that global atmospheric temperatures have not gone up significantly during the past 10-15 years.

Does this disprove the idea that the planet will warm due to increased CO2 and other greenhouse gases?  Are the global climate models mistaken?  Who are telling the truth:   the skeptics or climate scientists?

My take on all this is that a decade of near-constant temperature does not show a fatal flaw in climate science, but it does reveal poor communication and occasional overhyping by climate scientists.  And some cynical games by skeptics.

So what is all the debate about?  Here is a plot of global temperature from the NASA Goddard web site, showing the annual mean and 5-year running mean temperatures from 1880 to now (actually it shows the difference...or anomaly...from the average for 1951 to 1980).  Error bars indicated by the green brackets.

Global temperatures fell to about 1910, rose to roughly 1940, leveled off for forty years, rose rapidly from 1980 to roughly 2000 and then have been nearly constant for the past 15 years. The level period during recent years is the "pause" that everyone is debating about.

The fact that temperatures level off for a several years...even a decade or more...is not surprising or exceptional, even if the earth is generally warming due to greenhouse gas increases.  The atmosphere/ocean/cryosphere (ice) system has a number of modes of natural variability--in other words temperatures will vary WITHOUT any "cause" or external forcing.  One example you all know about:  El Nino/La Nina, which causes variations over a period of typically about 7 years.  But there are others.   Over the Pacific basin, there is the Pacific Decadal Oscillation, with a period of about 60 years, while the Atlantic Multidecadal Oscillation (AMO) has a period of about 70 years.   And there are others.

According to most estimates, the forcing (greenhouse gas warming) by humans on the radiation coming into and out of the planet only became appreciable around 1970, and even today natural variability is as large or larger than the human-caused warming signal.   So when natural variability is pushing the atmosphere towards cooling, it can balance the global warming signal, resulting in little change. Or even temporary cooling.

There is another possible contributor to the recent leveling:   the huge increase in particles (aerosols) in the atmosphere associated with the big increase in coal burning and petroleum usage in China.    Such particles can cause cooling both directly (by reflecting solar radiation to space) and indirectly  (by changing the number of cloud droplets).

Satellite measurement of particles in the atmosphere.

Particles from China and other sources could result in cooling that can offset greenhouse-gas warming produced by CO2 from burning fossil fuels.  But quite honestly, we don't have a good handle on the amount of such particles and their impacts, both direct and indirect. We have good reason to believe that such particles result in cooling though.

Some recent articles have speculated that some of the greenhouse gas warming is going into the deep oceans and thus unavailable to heat the atmosphere.  A lot of uncertainty in that hypothesis.

Some of you might ask, quite reasonably, is it possible that some of the warming during the late 20th century was not due to anthropogenic (human-caused) greenhouse warming but was the result of natural variability?   This is surely possible.  In fact, a colleague of mine at the UW,  K. K. Tung, and his associates have written a paper suggesting that some of the recent warming was due a natural mode of variability (the Atlantic Multi-Decadal Oscillation, see graph below).  And an increasing number of studies have suggested that part of the loss of Arctic sea ice was caused by changes in atmospheric circulation, not greenhouse gas warming.   So folks, one really has to be careful here.

 Research by Tung and Zhou suggest that the AMO internal variability (red line) could explain some of the rapid warm up in the late 20th century and the climate pause of the last decade.  It also implies that warming could be delayed a few decades.

So it is quite possible that the recent pause in warming could be traced to some combination of natural variability and particles from China and elsewhere.   And that some of the warming that led to the pause may have been of natural origin.  You don't see this well covered in the popular media.

A pause in the warming is good, but there is no reason to expect it to last more than a few decades.  Cooling from natural variability will be replaced by warming as the natural cycle moves to a warming phase.  And China will eventually have to clean up its act   as it has become clear that the smoke and particles are making life miserable and unhealthy for the Chinese.   And just as important:  mankind's forcing of global warming will  increase as the levels of CO2 and other greenhouse gases increase in the atmosphere. And they will increase, particularly with all the cheap/abundant gas and oil from fracking (see graphic).  Emissions and concentrations of greenhouse gases will continue to rise during this century.

To put it another way, add a relatively constant level of natural variability to an increasing human-caused global warming signal, and eventually global warming will win. 

Many skeptics refuse to acknowledge the basic ideas outlined above and are fixated on the "pause" or the origins of past temperature variations.  That is not the real issue here.  The issue is that human-caused global warming will eventually dominate....and that will happen during the second half of the century.

But, let's face it, some of those believing in the serious nature of global warming have also been confusing the public.  How many times have you seen global warming advocates crow about a single record warm year, heat wave, or a season with less ice in the arctic as clear proof of global warming?  Quite often.  But such transient or brief events could well be mainly the result of natural variability.

Atmospheric scientists should know about natural variability and must be more careful in claiming that short-period extremes mean anything.  And you can see the gamesmanship when they keep quiet about unusual cold periods.

Climate scientists are their own worst enemies when they show the average (or ensembles) of climate models (see below).  Each climate model simulation HAS natural variability (see example below), but when you average them this variability is smoothed out, leaving a steady rise in temperature due to greenhouse gas forcing.  But such a steady rise will never occur in the real world, a real world in which lots of natural variability exists.  So it looks like climate scientists have it all wrong when a period of no warming or cooling occurs for a short period.  Talk about shooting oneself in the foot!

 A collection of climate forecasts using global climate models are not identical due to differing natural variability in each.

And there is another issue.  Most climate models have been "tuned" or calibrated to match the variations in 20th century climate.   All climate models have "knobs" or the ability to change key parameters that are not well understood (like the impacts of particles in the atmosphere), and these knobs are often adjusted to match the known variation and structures of the atmosphere during the historical period with observations.  The trouble is that one can overtune and actually degrade the model's ability to predict the future by doing this.   For example, if a particular model did not get the cooling in the mid-20th century correctly, perhaps because it did not have the phasing of natural variability correct, a "tuning" to make it do better might change the model in a way the undermines its ability to forecast correctly in the 21st century.   Such matters need to be talked about more.  Fortunately, as we learn more about the atmosphere, the need for tuning has declined, but it is still an issue.

Anyway, this climate business is complicated stuff with a lot of subtleties, and folks on both "sides" have been presenting material that could be deceiving.  But the bottom line is still clear, the human-induced warming signal will increase during this century to a point that its significance and importance will be undeniable.  But the magnitude of this change is still uncertain.


  1. Dr. Mass-

    I'm a master's student and longtime fan of your blog, and would just like to insert my two cents on your recent post.

    While your accurate description of the uncertainties of climate variability does highlight the confluence of many separate processes (i.e. ENSO, PDO, NAO) that can diminish the warming signal, but I think focusing on this recent dip is hardly helpful to the climate conversation. Model uncertainty and error and a nascent understanding of some of most powerful forcings (i.e. arctic permafrost,deep-sea methane hydrates)are certainly worth discussing, so long as it is framed by the larger picture: the conditions we've created on this planet simply have not existed in over 400k years. The carbon experiment is frightening not only because forecasts have been proven increasingly conservative, underestimating positive feedbacks, but also because in this experiment n = 1.

    The attention paid to the dips in what is an overwhelmingly dramatic increase in GHGs is worth noting but not dwelling on. And while I am and will remain a huge fan, we all look at this issue through our own lens and I think it disingenuous to purport a balanced post when I and others familiar with previous writings can quite easy see your opinion. I think skepticism is the foundation for good science, but the treatment of publishing climate scientists likens them to second-class citizens when compared to other branches of science. Unfortunately the traditional model for debate allots equal coverage for each side of an issue, even if malicious intentions and purposeful disinformation campaigns characterize one ‘side.’ Even IF CO2 doesn’t cause warming, disproving over 200 years of physics, fossil fuels are still a finite resource – we have to figure out another energy solution either way. The science of this problem is simple, it’s the politicization of it that is tragic for our children and grandchildren. The seriousness of climate destabilization is a threat to civilization itself - if we do not find a way to end our carbon addiction, the conditions that fostered the rise and dominance of mankind will cease to exist. These are inter-generational crimes being committed, and history will judge our inaction.

    I'm veering off point here and make no claims of an unbiased opinion. Your post explained the complexities of variability well, and as always we the fans love your posts. But this is a problem the likes of which has never been seen, and the public needs to take it just as seriously as those researching it. These minor deviations of slight cooling are only noise/variability and detract from a grim reality - climate scientists are increasingly nervous, and we should be too.


  2. Thanks Cliff, another a very sensible description of a complicated situation.

    Dealing with uncertainty and noise is hard, but critical while models are still developing and the noise is comparable to the signal.

  3. A mean, even a running mean, comes with some assumptions. The governing one is that the mean describes the central behavior of the system. In chaotic systems this isn't true. Consider the Lorenz system of equations: in general a windowed mean can be a useful predictor of behavior but in particular it is totally useless because it doesn't tell you about gross systemic transitions - it falls down harder there.

    I am refreshed and delighted by your technical honesty here. A business manager might like the mean trend, but as a scientist those sorts of cartoons are both non-informative, disigenuine and counterproductive. I would prefer best estimates to account for central and variational tendency to inform the intuition of the billions of non-scientists whose support is needed in order to inform effective remedial action.

  4. An excellent summary of the situation! The record you show has other "pauses" in it, so the current one should not be fixated upon by the deniers as a way to repudiate the trend. And I agree fully that a few climate scientists have been all too eager to seize upon "weather" events as evidence for climate change. It's hypocritical to do something for which deniers have been criticized (correctly).

  5. I think the most interesting 'anomaly' with respect to climate change is the fact that springtime temps in the Pacific Northwest have seen little to no change over the past century. In recent years most of the La Niña springs have been very chilly, but the El Niño springs not particularly warm. It could just be a string of bad luck (or good luck, if you consider the effect of earlier snowmelt?). But I have a feeling it won't be long before we experience a historically warm spring again, like we saw in 1992.

  6. Great post! I don't understand why you (Dr. Mass) and commenter Chuck Doswell can't simply come out and say it verbatim, which is that Al Gore is one of the worst offenders when it comes to showcasing recent significant weather events in connection with GHG warming. If you don't believe me simply spend a few minutes scrolling through Gore's blog. This is such an atrocity yet we let him get away with often subverting the science (simply because the Norwegians annointed him with a Nobel prize shared with the IPCC). This is disgusting!

  7. A very good rundown. Though I do think even though you have bolded every reference to the inevitability of global warming you still seem to diminish the imperative, likely unintentionally.

    After all, it really doesn't matter how little we see evidence of it now, the fact is if we don't make major changes within the next decade, we will be locked in to dramatic and potentially catastrophic changes when it all catches up to us.

    I still believe the Arctic is the canary in the coal mine. The changes there have occurred so rapidly and so dramatically, there is simply no way they can be down to natural variation.

    This just released animation is very well done.


  8. Cliff, I'm a mere mortal, with no specialized education or training, but I do my best to raise local awareness about the many implications of a large "energy diet." I join many others in thanking you for providing your readers with a continuing education on the topic, and especially for your critical commentary on extremists at both ends of the argument. It's a sad fact of our culture that we seem to require a crisis to overcome or a perceived enemy to vanquish before we can collectively agree to simply do the right thing. In my own small way, I speak of climate CHANGE in lieu of global warming and continue to stress that changes, whether for ill or for good, are likely to be experienced (or suffered) by our descendents, for whom we should have some concern. Thanks, many times over, for continuing to share your sensible and objective voice in the maelstrom of this divisive topic. ~ Greg

  9. Nice post. Absent warming from anthropogenic CO2, when do climatologists think the next glaciation will start?

  10. Cliff Mass says:

    "...folks on both 'sides' have been presenting material that could be deceiving."

    The deception begins with the first graph posted. The only way to understand what is happening is by looking at very long term global temperature graphs.

    The first graph is a zero baseline graph, which is used because it creates an alarming rise in global temperature. But in reality, the rise has been along the long term trend line since the Little Ice Age [LIA]. The alarming rise is an artifact of a zero baseline chart. A trend chart shows what is actually happening.

    Observe that there has been NO acceleration of global warming since the LIA, despite a ≈40% rise in CO2: http://tiny.cc/oyt9vw

    Note also the long term trend line [the green line], shows no acceleration in warming. In fact, the long term trend is gradually declining.

    This is solid scientific evidence that the large rise in CO2 does not cause global warming. If it did, then the long term trend line would have accelerated upward. But it did not. Current temperatures remain along the long term trend line, and have recently plunged down through it.

    The planet is recovering from the LIA. We do not know the original cause of the LIA — one of the coldest episodes of the entire Holocene. But clearly, the planet is naturally reverting to it's mean temperature, and CO2 has had no measurable effect.

    Let me add that I think CO2 does have a small warming effect. But it mostly occurred in the first 20 ppmv. Currently, adding CO2 at nearly 400 ppmv has no measurable effect.

    As uncomfortable as it may be, honest scientists must accept the fact that their CO2 = AGW conjecture is being falsified by Planet Earth. Trying to argue around that fact reeks of confirmation bias.

    If 40% more CO2 has not caused the long term naturally rising temperature trend to accelerate, then CO2 does not have the claimed effect.

    It is as simple as that.

  11. From the article: the human-induced warming signal will increase during this century to a point that its significance and importance will be undeniable. But the magnitude of this change is still uncertain.

    Sounds like a statement of faith to me. "A" is "A" a philosopher once said... "uncertainty" is "uncertain"

  12. A good example of why this blog is the best! Balanced, conservative (in the non-political sense of the word) scientific reporting.

  13. Per my view, all that we can all hope for, set beside the ongoing controversy, with its many different elements and facets whether more or less substantive, is an increasingly better general paradigm through which to work to gage what's actually occurring climatologically.

    My best sense of the current "pause", is that it's part of a more cyclical element's being involved somehow.

  14. Without having read all the comments here, I don't want to miss making one point: Why in the world would global warming doubters use global temperature statistics to make their case when they would ignore those same stats when they clearly indicated warming?? . . .

  15. Dr. Mass,

    You are a puzzle to me. Your weather blog entries are wonderful--well structured, abundantly supported and illustrated, and extremely informative. By contrast, your climate posts are all over the map, and always end up with the same statement, which doesn't follow from the rest of your entry. Your latest post "The 'Pause' in Global Warming" is a good example.

    To start with I must quibble with your distinction between “skeptics” and “climate scientists." Do you mean that these two categories are mutually exclusive? In which "box" do you put R. Lindzen, R. Carter, C. Landsea, R. Spencer, J. Curry, et al.?

    But now to the meat of your post. You are right to point out that
    - many factors are involved in any temperature variation and that even today natural variability is as large or larger than the human-caused warming signal;
    - "we don't have a good handle on the amount of ... particles and their impacts." (so what supports your statement that we "have good reason to believe that such particles result in cooling"?);
    - it is quite possible that some of the warming during the late 20th century was not due to anthropogenic greenhouse warming but was the result of natural variability;
    - "an increasing number of studies have suggested that part of the loss of Arctic sea ice was caused by changes in atmospheric circulation, not greenhouse gas warming ... one really has to be careful here."
    - "some of the warming that led to the pause may have been of natural origin" 
    - "this climate business is complicated stuff with a lot of subtleties."

    Your mention of sources of uncertainty, natural cycles and variability as well as possible explanations for warming other than human-produced CO2 (all of which are a good summary of the state of current climate science) leads logically to you cautionary statement: "So folks, one really has to be careful here."

    On the other hand, your "bottom line is clear" conclusion shows no caution at all. Your claim that "the human-induced warming signal will increase during this century to a point that its significance and importance will be undeniable" is in contradiction with the body of your post; it is unwarranted and gratuitous.

  16. Lindsey,

    What a strange comment. You refer to "global warming doubters". But who doubts global warming??

    The long term temperature record shows unequivocally that the planet has warmed since the LIA. There is no controversy over that fact.

    The problem is that a minority of scientists believe that global warming is caused by human activity. But that notion is easy to refute:

    The long term rising temperature trend has not accelerated, even following the ≈40% rise in CO2. In fact, global warming has stopped for at least the past 16 years.

    Therefore, the mistaken belief that CO2 is the central cause of global warming is completely deconstructed by scientific measurements. If global warming has not accelerated after that very large rise in CO2, then obviously CO2 cannot be the primary cause of global warming.

    I do not think a case can be credibly made that CO2 causes ANY measurable warming, since there are no scientific measurements directly attributing global warming to CO2. And if something cannot be measured, it is hardly science.

    The AGW conjecture is merely an assertion, with no empirical measurements to support it. If AGW could be measured, then the question of the climate sensitivity number to 2xCO2 would have been decisively settled by now.

    But the sensitivity number guessestimates range from a negative sensitivity, to zero warming per 2xCO2, to the wild-eyed IPCC's preposterous claim of 3º – 6ºC per 2xCO2.

    If the warming due to human-emitted CO2 could be quantified and tested per the Scientific Method, there would be no dispute over the climate sensitivity number. But the fact that the number is so vague is due to AGW never having been reliably measured. AGW is based on guesses and assertions, not on measurements.

    And if it were not for the immense amounts of grant money flowing into climate scientists' pockets, then climate 'science' would be on a par with psychology, sociology, and wymyn's studies.

    Only federal grant money keeps the AGW scare alive — at the direct expense of hard-bitten taxpayers, many of whom see AGW as a self-serving scam.

    Prove me wrong, with empirical measurements. If you can.

  17. For those interested in scientists discussing all the pros, cons, warts & all -- including technical issues -- I recommend realclimate.org. Cliff is right about hype in the media re: this or that latest data point, but *all* the issues of complexity that he raises here, including variability, are *already being very seriously considered by climate scientists.

    The hype is understandable. Our world's climate is changing, temps upward, as Cliff says. But we humans pretty much NEVER do anything hard collectively except when emotions run high. The balanced, logical scientific approach is fine for advancing understanding & suggestions for technical advances, but those almost NEVER lead to rationale collective responses. Too bad, but true, leading some wags to rename our species as Bozo sapiens, a tag that seems quite reasonable to me. Until human nature is changed, hype and repetition -- even of extremes & variability -- are part of how humans collectively (and often individually) finally notice ... hey, something's going on that needs doing something about.

  18. An interesting discussion, but why no mention of the potential effects of the state of the solar cycles during the little ice age cooling and also during the twentieth century warming? Currently weak cycle 24 is proving very similar to cycle 5 which occurred during the Dalton minimum - when the climate was colder. Cycle 25 is expected to be weaker than cycle 24 with more cooling predicted.
    It also would have been interesting to hear your take on the Svensmark cosmic ray theory as that may play a very large role in the sun-climate relationship and its impact on natural variability.

  19. This post is wrong on many levels, but mostly for those who really believe in AGW.

    Because 1) the science is far from settled to any degree of certainty. For example this new study that implicates long term solar cycles. http://english.ruvr.ru/2013_04_22/Cooling-in-the-Arctic-what-to-expect/ And there are many others regarding Pacific Ocean cold water upwellings, Cosmic rays and cloud formation and so on. We simply do not know enough to make any long term predictions about climate much less policy that is damaging to our fragile economies.

    And 2) Because there is no crisis. Anyone can look out the window and see that in terms of impact to their own lives there has been zero noticeable change. We hear scary predictions of 2 foot sea level rise, but at best it has been on the order of millimeters. 2 feet would be a crisis, millimeters are a non event because humans are the most adaptive species on the planet. If and when sea level ever does rise two feet, humans will simply move up two feet and it will be over such a long gradual time (multiple generations) that it will be almost imperceptible. Crisis implies immediacy and there is none. Zilch.

    And so Cliff, when you make a post like this, you attempt to bring urgency where there is none. And ultimately when people hear so much crying wolf they tune it out.

    So thanks, because as humans we have much more important and real problems to solve like cancer, AIDS, obesity, economic, hunger, transportation, etc. Climate Change is a joke that no one cares about.

  20. Cliff- I have been reading and enjoying your blog for several years. I really enjoy the posts you make on PNW weather phenomena. Your posts on climate change always leave me scratching my head and trying to figure out what you believe and why you say what you say.

    To me, it's if we are in a boat teetering on the edge of Niagara Falls. The front of the boat is just tipping over the edge and people are arguing about the significance of the slight angle of the boat. Some say it's not enough of a tip yet to be sure we are going over. I and others are looking at 500 feet of roiling falls below us and saying "Stop arguing and paddle faster". I think the physics of the effect of CO2 and other greenhouse gasses is well-established and scientifically sound. Just as it's clear that gravity will pull you down the falls, not up. By the time we are in free fall and everybody agrees that we are heading over the falls it will be way to late to paddle. What is the benefit of waiting to take action? Well, there is an awful lot of profit to be made from oil, natural gas and coal. The benefit of waiting is that the energy companies will have 30 more years to do what they do. In 30 years the environment will be more polluted, the earth will be more crowded. Anybody who has kids and wants them have a middle and old age free from hunger and war would do well to start cutting fossil fuel use.

  21. Good post, your bias is self evident but good post anyway. You did not mention solar forcing at all in your post. I believe one comment mentioned this. Is the sun so constant that it is not to be considered? Astrophysics would say otherwise. I believe there are credible solar researchers that say the strength of the magnetic field in sunspots is reducing at a rate that by the next solar cycle sunspots will be few to non existant. Will this affect the earths global temperature? Again there are some researchers that say yes, big time effect, cooling effect. But yet, no talk in your blog about solar forcing.

    To those that say CO2 is warming the planet and we must act now. What should we do? drastically reduce burning fossil fuels of course. And what are the implications of such a policy? If we drastically reduce our consumption of fossil fuels the result will quite likely be billions of people dying from starvation. We use a tremendous amount of fossil fuel to grow and transport food. Who do you propose not get the food? Are you lining up to only eat food that grows within a days walk of your house?

    Al Gore is such a great proponent of reduced fossil fuel usage (as are most in the western hemisphere who advocate drastic action). He goes around the country saying we must act now! A few commentaries on this blog are likewise inclined. So Al Gore then climbs in his private jet and flies to Bali to warn the world about burning fossil fuel. His usage of fossil fuel is so far above the norm as to be grotesque. But it is fine for him to live a lifestyle of excess (as perhaps some on this blog also feel?) but everyone else in the world has to cut back and have a reduced standard of living? Sure.

    It is not enough to say that science is on my side and we need to act. You must act or your words are hollow. What will a world with drastically reduced fossil fuel usage look like? Are you prepared to live that life today?

  22. Paul Flatt -

    Good comment. It's one of the reasons I'm a fatalist. Yes, I believe in AGW. I also just as firmly believe that we are going to do nothing about it, despite all the hand-wringing in certain quarters. It would be tremendously hard and would require active support by a tremendous number of people on every continent, and in many countries (most of all in the developed ones).

    We'll never do it.

    We can't even reach agreement that it's worth doing anything about....just look at some of the comments in this section, even though Cliff's reporting/writing is the most unbiased I've seen.

    Even if one does not believe in AGW, the effects of pollution on the air, land, and water from all the fossil fuel use that occurs today should at least yield a collective concern and desire to change. But it doesn't - and it isn't exclusive to the U.S.

    I don't remember which Native American tribe (or perhaps it was more than one) that used to make decisions based upon the impact the decision would have on "the 7th generation", but I know one thing for sure - we (speaking in the most general sense) really don't want to change our lifestyle to help any generation that comes after us - and the more distant they are, the less willing we are to change.

    Which is a pretty sad commentary, really.

    And for the record - I grow all our own vegetables, I drive a Prius, I do all I can do to make a change. But I do it for sake of personal integrity, not because I think it's really going to make a difference.

    It would make for an interesting post, though...exactly what would have to change and by how much in order to make a noticeable difference in emissions?

  23. Great to see Mogumbo Gono and a few others who can read and comprehend both sides of the story and are not buying into anthropogenic global warming! As pointed out CO2 levels continue to rise and are at historic levels but the earths temperature has been steady since the late 1990's. Go to http://www.c3headlines.com/modern-temperatures-chartsgraphs.html for many temperature and CO2 charts and you will clearly see there is NO link! Climate change is real and the earth will continue to warm and yes COOL in the future due to many different things including solar activity.

  24. Janet D said...

    "Yes, I believe in AGW."

    "Believe" is the correct word. Because there are no empirical, testable measurements of AGW. Thus, AGW is a conjecture; a belief. An opinion.

    There are verifiable, testable measurements showing that changes in CO2 levels are caused by temperature changes.

    But there are NO empirical, testable measurements or observations showing that ∆T causes ∆CO2. Really, no such measurements exist. So believing in AGW is an act of faith.

    You would think that after decades of furious scientific investigation by thousands of well compensated scientists, that measurements of AGW would be commonplace. Plenty of grant money would follow verifiable measurements of AGW.

    Doesn't the lack of any such verifiable measurements of AGW incline you to believe that perhaps AGW is either too small to measure [and thus is no threat], or that AGW simply does not exist?

    Science is about measurements. If something cannot be accurately quantified, it is hardly science, is it? No, belief in AGW is more like religion at this point.

    Finally, a straightforward question: what would it take for you to reconsider your belief in AGW? How many more years of no global warming would it take to make you question your belief in AGW?

  25. Thanks Dr.
    Though I am nearly three years late to the table, I hope you will accept my humble input.

    A rather complete look at the issue ...though, it seems to me, there are one or two possibilities that lack consideration in your blog entry.

    1) Has one considered the possibility; the calculations that suggest a recent past warming and the current pause are an artifact of the existence of false assumption(s) inherent in 'CO^2 driven climate models'?

    2) A second explanation or perhaps an ancillary one to the above... The (a)adjusted data and it's associated (b)level of confidence may be too (a)imprecise and (b)unrealistic when employed to reach legitimate conclusions of variability to a claimed level of precision (that of being) within a few thousandths of one degree.

    Thanks for the opportunity to respond on your site.

  26. More recent research into possible connection of cloud cover and cosmic rays is mentioned about halfway down at: spaceweather.com/archive.php?view=1&day=28&month=08&year=2016


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