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The Big Picture (2010 version)

Posted on 24 September 2010 by dana1981

Note: this is the initial version of our Big Picture article published in 2010. As part of our Rebuttal Update Project, the article has been updated and republished with more current data in February 2023. You can access the current version here.

Oftentimes we get bogged down discussing one of the many pieces of evidence behind man-made global warming, and in the process we can't see the forest for the trees. It's important to every so often take a step back and see how all of those trees comprise the forest as a whole. Skeptical Science provides an invaluable resource for examining each individual piece of climate evidence, so let's make use of these individual pieces to see how they form the big picture.

The Earth is Warming

We know the planet is warming from surface temperature stations and satellites measuring the temperature of the Earth's surface and lower atmosphere. We also have various tools which have measured the warming of the Earth's oceans. Satellites have measured an energy imbalance at the top of the Earth's atmosphere. Glaciers, sea ice, and ice sheets are all receding. Sea levels are rising. Spring is arriving sooner each year.  There's simply no doubt - the planet is warming (Figure 1).

warming world

Figure 1: Indicators of a warming world

Global Warming Continues

And yes, the warming is continuing. The 2000s were hotter than the 1990s, which were hotter than the 1980s, which were hotter than the 1970s. 2010 tied for the hottest year on record.  The 12-month running average global temperature broke the record three times in 2010, according to NASA Goddard Institute for Space Studies (GISS) data.  Sea levels are still rising, ice is still receding, spring is still coming earlier, there's still a planetary energy imbalance, etc. etc.

Contrary to what some would like us to believe, the planet has not magically stopped warming.  Those who argue otherwise are confusing short-term noise with long-term global warming (Figure 2).


Figure 2: The data (green) are the average of the NASA GISS, NOAA NCDC, and HadCRUT4 monthly global surface temperature anomaly datasets from January 1970 through November 2012, with linear trends for the short time periods Jan 1970 to Oct 1977, Apr 1977 to Dec 1986, Sep 1987 to Nov 1996, Jun 1997 to Dec 2002, and Nov 2002 to Nov 2012 (blue), and also showing the far more reliable linear trend for the full time period (red).

Foster and Rahmstorf (2011) showed that when we filter out the short-term effects of the sun, volcanoes, and El Niño cycles, the underlying man-made global warming trend becomes even more clear (Figure 3).

before/after filtering

Figure 3: Temperature data (with a 12-month running average) before and after the short-term factor removal

For as much as atmospheric temperatures are rising, the amount of energy being absorbed by the planet is even more striking when one looks into the deep oceans  and the change in the global heat content (Figure 4).

global heat content

Figure 4: Total global heat content. Data from Nuccitelli et al. (2012)

Over 90% of global warming goes into heating the oceans.  When taking the heating of the entire climate system into account, the planet has warmed at a rate equivalent to 4 Hiroshima atomic bomb detonations per second over the past 15 years.

Humans are Increasing Atmospheric Greenhouse Gases

The amount of greenhouse gases in the atmosphere - particularly carbon dioxide (CO2) - has been rising steadily over the past 150 years.  There are a number of lines of evidence which clearly demonstrate that this increase is due to human activities, primarily burning fossil fuels.

The most direct of evidence involves simple accounting. Humans are currently emitting approximately 30 billion tons of CO2 per year, and the amount in the atmosphere is increasing by about 15 billion tons per year.  Our emissions have to go somewhere - half goes into the atmosphere, while the other half is absorbed by the oceans (which is causing another major problem - ocean acidification). 

We also know the atmospheric increase is from burning fossil fuels because of the isotopic signature of the carbon in the atmosphere.  Carbon comes in three different isotopes, and plants have a preference for the lighter isotopes.  So if the fraction of lighter carbon isotopes in the atmosphere is increasing, we know the increase is due to burning plants and fossil fuels, and that is what scientists observe. 

The fact that humans are responsible for the increase in atmospheric CO2 is settled science.  The evidence is clear-cut.

Human Greenhouse Gases are Causing Global Warming

There is overwhelming evidence that humans are the dominant cause of the recent global warming, mainly due to our greenhouse gas emissions. Based on fundamental physics and math, we can quantify the amount of warming human activity is causing, and verify that we're responsible for essentially all of the global warming over the past 3 decades.  The aforementioned Foster and Rahmstorf (2011) found a 0.16°C per decade warming trend since 1979 after filtering out the short-term noise. 

In fact we expect human greenhouse gas emissions to cause more warming than we've thus far seen, due to the thermal inertia of the oceans (the time it takes to heat them).  Human aerosol emissions are also offsetting a significant amount of the warming by causing global dimming.  Huber and Knutti (2011) found that human greenhouse gas emissions have caused 66% more global warming  than has been observed since the 1950s, because the cooling effect of human aerosol emissions have offset about 44% of that warming.  They found that overall, human effects are responsible for approximately 100% of the observed global warming over the past 60 years (Figure 5).

knutti breakdown

Figure 5: Contributions of individual forcing agents to the total change in the decadal average temperature for three time periods. Error bars denote the 5–95% uncertainty range. The grey shading shows the estimated 5–95% range for internal variability based on the CMIP3 climate models. Observations are shown as dashed lines.

There are also numerous 'fingerprints' which we would expect to see from an increased greenhouse effect (i.e. more warming at night, at higher latitudes, upper atmosphere cooling) that we have indeed observed (Figure 6).


Figure 6: Observed 'fingperprints' of man-made global warming

Climate models have projected the ensuing global warming to a high level of accuracy, verifying that we have a good understanding of the fundamental physics behind climate change.

Sometimes people ask "what would it take to falsify the man-made global warming theory?". Well, basically it would require that our fundamental understanding of physics be wrong, because that's what the theory is based on.  This fundamental physics has been scrutinized through scientific experiments for decades to centuries.

The Warming will Continue

We also know that if we continue to emit large amounts of greenhouse gases, the planet will continue to warm. We know that the climate sensitivity to a doubling of atmospheric CO2 from the pre-industrial level of 280 parts per million by volume (ppmv) to 560 ppmv (we're currently at 390 ppmv) will cause 2–4.5°C of warming. And we're headed for 560 ppmv in the mid-to-late 21st century if we continue business-as-usual emissions.

The precise sensitivity of the climate to increasing CO2 is still fairly uncertain: 2–4.5°C is a fairly wide range of likely values.  However, even if we're lucky and the climate sensitivity is just 2°C for doubled atmospheric CO2, if we continue on our current emissions path, we will commit ourselves to that amount of warming (2°C above pre-industrial levels) within the next 75 years.

The Net Result will be Bad

There will be some positive results of this continued warming. For example, an open Northwest Passage, enhanced growth for some plants and improved agriculture at high latitudes (though this will require use of more fertilizers), etc. However, the negatives will almost certainly outweigh the positives, by a long shot. We're talking decreased biodiversity, water shortages, increasing heat waves (both in frequency and intensity), decreased crop yields due to these impacts, damage to infrastructure, displacement of millions of people, etc.

Arguments to the contrary are superficial

One thing I've found in reading skeptic criticisms of climate science is that they're consistently superficial. For example, the criticisms of James Hansen's 1988 global warming projections never go beyond "he was wrong," when in reality it's important to evaluate what caused the discrepancy between his projections and actual climate changes, and what we can learn from this. And those who argue that "it's the Sun" fail to comprehend that we understand the major mechanisms by which the Sun influences the global climate, and that they cannot explain the current global warming trend. And those who argue "it's just a natural cycle" can never seem to identify exactly which natural cycle can explain the current warming, nor can they explain how our understanding of the fundamental climate physics is wrong.

There are legitimate unresolved questions

Much ado is made out of the expression "the science is settled."  The science is settled in terms of knowing that the planet is warming rapidly, and that humans are the dominant cause.

There are certainly unresolved issues.  As noted above, there's a big difference between a 2°C and a 4.5°C warming for a doubling of atmospheric CO2, and it's an important question to resolve, because we need to know how fast the planet will warm in order to know how fast we need to reduce our greenhouse gas emissions. There are significant uncertainties in some feedbacks which play into this question. For example, will clouds act as a net positive feedback (by trapping more heat, causing more warming) or negative feedback (by reflecting more sunlight, causing a cooling effect) as the planet continues to warm?  And exactly how much global warming is being offset by human aerosol emissions?

These are the sorts of questions we should be debating, and the issues that many climate scientists are investigating. Unfortunately there is a very vocal contingent of people determined to continue arguing the resolved questions for which the science has already been settled. And when climate scientists are forced to respond to the constant propagation of misinformation on these settled issues, it just detracts from our investigation of the legitimate, unresolved, important questions.

Smart Risk Management Means Taking Action

People are usually very conservative when it comes to risk management.  Some of us buy fire insurance for our homes when the risk of a house fire is less than 1%, for example.  When it comes to important objects like cars and homes, we would rather be safe than sorry.

But there is arguably no more important object than the global climate.  We rely on the climate for our basic requirements, like having enough accessible food and water.  Prudent risk management in this case is clear.  The scientific evidence discussed above shows indisputably that there is a risk that we are headed towards very harmful climate change.  There are uncertainties as to how harmful the consequences will be, but uncertainty is not a valid reason for inaction.  There's very high uncertainty whether I'll ever be in a car accident, but it would be foolish of me not to prepare for that possibility by purchasing auto insurance.  Moreover, uncertainty cuts both ways, and it's just as likely that the consequences will be worse than we expect as it is that the consequences won't be very bad.

We Can Solve the Problem

The good news is that we have the tools we need to mitigate the risk posed by climate change.  A number of plans have been put forth to achieve the necessary greenhouse gas emissions cuts (i.e. here and here and here).  We already have all the technology we need.

Opponents often argue that mitigating global warming will hurt the economy, but the opposite is true.  Those who argue that reducing emissions will be too expensive ignore the costs of climate change - economic studies have consistently shown that mitigation is several times less costly than trying to adapt to climate change (Figure 7). 

Figure 7:  Approximate costs of climate action (green) and inaction (red) in 2100 and 2200. Sources: German Institute for Economic Research and Watkiss et al. 2005

This is why there is a consensus among economists with expertise in climate that we should put a price on carbon emissions (Figure 8).

should US reduce emissions


Figure 8: New York University survey results of economists with climate expertise when asked under what circumstances the USA should reduce its emissions

The Big Picture

The big picture is that we know the planet is warming, humans are causing it, there is a substantial risk to continuing on our current path, but we don't know exactly how large the risk is. However, uncertainty regarding the magnitude of the risk is not an excuse to ignore it. We also know that if we continue on a business-as-usual path, the risk of catastrophic consequences is very high.  In fact, the larger the uncertainty, the greater the potential for the exceptionally high risk scenario to become reality. We need to continue to decrease the uncertainty, but it's also critical to acknowledge what we know and what questions have been resolved, and that taking no action is not an option.  Th good news is that we know how to solve the problem, and that doing so will minimize the impact not only on the climate, but also on the economy.

The bottom line is that from every perspective - scientific, risk management, economic, etc. - there is no reason not to immeditately take serious action to mitigate climate change, and failing to do so would be exceptionally foolish.

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Comments 151 to 200 out of 221:

  1. #147: you think that a global temperature change of a scale that will give us a glacial-interglacial transition in short order is a "minimal" change. Wow. Based on... looking out of your window? Eyeballing a graph and thinking that the numbers look kinda small? What is the context of the numbers? You have a lot of reading to do, and clearly a fair way to go before you comprehend the observed reality of the enhanced greenhouse effect and just how significant and rapid out current global warming is (much faster than the PETM). Start with the links above - and especially this Richard Alley AGU presentation
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  2. Excellent summary of the issue! I found a typo you may want to fix: "there is a there is a" (under 'There are legitimate unsolved questions").
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  3. In mainstream climate news, The Weather Channel has, remarkably, placed a GW article on its front page. I haven't yet looked at the comment stream, and I'm not sure I have the patience for it today. The article itself is a general report on the IPCC extreme events statement.
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  4. Can anyone explain why the first chart on the page shows the global warming to have about 2X greater slope than the second chart? Thanks.
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  5. @tksoft I suspect because the second plot is the change left after accounting for the effects of ENSO and solar and volcanic forcing. Also the 12 month running mean filtering used will damp down the variability of the signal somewhat. Oh and BEST is land only, whereas I suspect the second plot is probably global temperature, which includes the oceans.
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  6. To clarify: Here is a plot of both BEST and GISSTemp for the same sort of period, and you can see that the land has been warming more quickly than the global temperatures, which is I suspect due to the high heat capacity of the oceans. So the difference is likely to be just the difference between land only and global temperature datasets.
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  7. I think you nailed it. Thanks!
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  8. There are a couple points in the section "The Warming will Continue" that I would consider. "...if we continue to emit large amounts of greenhouse gases, the planet will continue to warm." Yes, but if we totally stopped emitting any greenhouse gases today, the plant would continue to warm. When there is an imbalance between the greenhouse gases in the atmosphere and the planet temperature, the temperature will change until equilibrium is reached. If we emitted no more greenhouse gases, then the atmospheric concentrations might decrease, which would result in the final equilibrium temperature being lower. On the other hand, if the rising temperature resulted in massive releases of methane from the permafrost and from the ocean bottom, then the greenhouse gases might increase. I am not aware of much work on the carbon dioxide-temperature equilbrium curve. The first-order approximation that I use is T=0.098c-27.1, where T is the equilibrium temperature in degrees Celsius and c is the atmospheric carbon dioxide concentration in ppm. This gives 0.34 degrees C for 280 ppm CO2 and 11.12 degrees for 390 ppm CO2. This means a 10.78 degree C increase over the preindustrial equilibrium. A relevant question is how long to reach equilibrium? I am using an estimate of about 700 years, which leads to rate of increase of a bit more than a degree per century if we assume a linear approach (very crude assumption). "The precise sensitivity of the climate to increasing CO2 is still fairly uncertain: 2–4.5°C is a fairly wide range of likely values. However, even if we're lucky and the climate sensitivity is just 2°C for doubled atmospheric CO2, if we continue on our current emissions path, we will commit ourselves to that amount of warming (2°C above pre-industrial levels) within the next 75 years." The equibrium approximation gives a temperature of 27.78 degrees Celsius for 560 ppm CO2, an increase of 27.44 degrees. I am not sure what the approach-to-equilibrium curve should look like. Naively, I would expect an initially slow response because it would be necessary to "overcome" some hysteresis in the planetary system. Then the rate of increase should become proportional to the difference between the equilibrium and the current temperatures. In other words, I would expect a slow increase gradually passing into a rapid increase that ultimately slows down to an asymptotic approach to equilibrium. I really have no idea just where 75 years from now would fall on such a curve covering about 700 years. Do you (or anyone) know of more detailed work on the equilibrium between atmospheric carbon dioxide and the planet temperature and on estimating the approach-to-equilibrium curve?
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  9. Bill, for curves showing what would happen in different scenarios of emission reduction, see the RealClimate post Climate Change Commitment II.
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  10. Also see Chap. 9 section 3 of the third iteration of the world's largest literature review on climate science, AKA IPCC AR3: Projections of Climate Change Getting on 12 years old but many of the fundamentals there have not changed.
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  11. Tom Dayton: Thanks. Hare & Meinshausen 2006 use the equivalent radiative forcing and "conventional IPCC uncertainty range for climate sensitivity" in their projected scenarios. I am interested in learning about work on the equilibrium between atmospheric carbon dioxide and the planet temperature and on estimating the approach-to-equilibrium curve. I adopted the formula T=0.098c-27.1 from Byalko 2012, cited at Can We Predict the Global Future? Part 2.
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  12. I’m new here, and have not had the resolve to read all 161 previous postings, so I apologize if I am going over old territory. I have a problem with the assertion that to be skeptical of the arguments adduced for anthropogenic global warming you must be asserting that the principles of physics are wrong. This is simply an appeal to authority and so is inappropriate.

    For example, it is possible that a given AOGCM might be incomplete or of too course resolution to give the best answer. Everyone knows that our understanding of aerosols and cloud dynamics is incomplete and therefore represents a large source of unreliability in the models.

    Another example is the serious lack of detailed understanding of the origins of glaciation and warming over the last 500K years, including the CO2 concentration lag. If we don’t fully understand the (apparently minor) roll of CO2 over that time period can we be sure we fully understand its roll now? There is much we still don’t understand. Does this mean that we don’t understand the fundamentals of physics?

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  13. @tcflood #162:

    You have stated, Everyone knows that our understanding of aerosols and cloud dynamics is incomplete and therefore represents a large source of unreliability in the models.

    Is this global assertion your personal opinion, or can you cite the sources from which it came?

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  14. tcflood@162

    "Everyone knows ... If we don’t fully understand the (apparently minor)..."

    Curious that you start off with an accusation of argument fallacy, yet you yourself deem it fit to use both argumentum ad populum as well as Inflation Of Conflict (or is it just a personal argumentum ad ignorantiam) to shore up your claims.

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  15. Can you respond to the point and then we can debate your assertions?

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    Moderator Response:

    [DB] For the issues surrounding the resolved temperature/CO2 lag, take that portion of the discussion to this post here. For a discussion on cloud feedbacks, see here. For aerosols, see this thread here and also this thread here.

    It is advised to also temper the tone of one's own remarks before casting stones at others. Please review this site's Comments Policy.

  16. (-Moderation complaints snipped-)

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    Moderator Response: [DB] You were given the guidance you both requested and needed. Choosing to ignore it is not a wise course of action. FYI.
  17. To John Hartz: Thanks for your response.

    It is stated in the paragraph "There are legitimate unresolved questions" in the article at the top. Also, the IPCC's FAR classifies the state of knowledge of areosols and clouds as "low".  Every textbook that I have consulted states the same thing. In a talk in LA a couple of weeks ago a climatologist at UCLA made the same comment. I just assumed that that would not be a controversial statement on this website.


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    Moderator Response: [DB] The FAR is dated. Please review the relevant chapters in the AR4 (here and here).
  18. (More moderation complaints snipped-).

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    Moderator Response: [DB] If you had bothered to read the Comments Policy you were directed to read, you would have noted that moderation complaints are frowned upon in this establishment. FYI.
  19. I defense of the main assertion in 162 regarding appeal to authority, I mentioned our lack if detailled understanding of the drivers of glacial/interglacial dynamics. I made the same comment in a personal exchange with a paleoclimatologist (so I won't give his name) at a major university and his response was "With regard to timing of glacial cycles, my view is that these cycles are nonlinearly phase locked to the Milankovitch forcing but that either the cryosphere, carbon cycle, or both give the longer timescale [than the resultant frequency of the Milankovich cycles]." That doens't sound like settled science to me.

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  20. Moderator,

    Is there an address where I can speak freely with you without anything appearing on this site even transiently? You have my email address so you can answer there.

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    Moderator Response: [DB] Check your email.
  21. tcflood - IPCC FAR was published in 1990. You have been pointed to more up to date data. Also please dont mistake "there is uncertainty" with "we dont know anything". Uncertainty constrains the confidence with which we can predict things. While there is no "authority", science starts with peer reviewed research. This inevitably has more value than unreviewed comments stuck on a blog somewhere. For that reason, this site refers back constantly to the peer-reviewed literature.

    While there is no final certainty in any part of science, policy must be guided by the best state of knowledge that we do have. If new data changes the model, then it changes, but it would be madness for policy makers to ignore the consensus of climate science.

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  22. @tcflood #16:

    Thanks for you reponse to my initital question.

    OK. I will concede that the scientific understanding of how clouds and aerosols impact the Earth's climate system is incomplete. I am, however, more interested in the second part of your sentence, i.e., "...and therefore represents a large source of unreliability in the models."  How do you this to be true? How much is a large source of unreliability in the models."  Does this amount of unreliability appear equally in  all climate models?

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  23. Moderator and scaddenp:

    Sorry, I was using FAR to mean the Fourth assessment Report published in 2007. The chart on page 4 lists the level of confidence of understanding of various forcings.

    Also, with regard to how science is done, I am a retired emeritus chemist who did research for 40 years (48 if you include my education). This is not an appeal to authority, just an attempt to point out that I know something about how it's done. I am not a denialist and I lean more toward accepting IPCC predictions than against. It's just that in my many years as a scientist I have seen many publications in refereed journals that were absolutely wrong. Lots of perople who made more far-reaching claims what were poorly or falsely based. I have refereed many papers where the authors were extremely authoritative but wrong. So please permit me to be a little cautious about accepting everything that either side says.  


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  24. @tcflood:

    Recommend that you peruse the SkS article, New tool clears the air on cloud simulations . Please not that it was posted in Nov, 2011.

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  25. John Hartz

    You have put your finger on the biggest issue I have with the modeling. How do we assess the uncertainty?  I have Figure SPM.4 on page 11 of the Fourth Assessment of calculations of temperatures using natural and anthropogenic forcings. It is very impressive. In fact, it is the single biggest reason that I am not on the skeptics side. It's just that in such complex systems it's hard to know how reliable they are without more extensive testing, which of course we don't have the luxury of here until it's too late.It is also extremely easy for group think to overwhelm an (intellectually) isolated group of people.

    I might say in passing that the second reason that I'm not with the skeptics is that I believe the Precautionary Principle is philosophically defensible and of great practical importance.  (Not just an emotional reaction as I have seen claimed in contrarian publications.)  

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  26. 174

    Thanks, John, I'll check it out.

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  27. tcflood - "It's just that in such complex systems it's hard to know how reliable they are without more extensive testing..."

    If you have read the Fourth Assessment report (commonly referred to as AR4), you will note the rather huge number of relevant references (here for aerosols, and here for attribution)

    I hate to say this, but you appear to be demanding perfection - we have sufficient data to constrain uncertainty within various bounds (depending on the specific topic), and using the Precautionary Principle, anything within those bounds is worth worrying about, worth acting upon. What for you would be sufficient evidence, sufficient testing? Must we 'wait and see' while ignoring what knowledge we have?

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  28. Pers. comm. comments from unnamed paleoclimatogist arent easy to pursue because cant see papers on which he bases opinions, but unless this Bob Carter, I would say he is somewhat uninformed on current literature. However, as a general point, paleoclimatology suffers from unconstrained problems. The discipline is important because obviously any theory of climate must work for past climate as well as present and so it is a "testing" ground for theory. However, paleoclimate abounds with problems where there is insufficient data to constrain one possibility against another. In particular you have uncertainty in forcings as well as uncertainty in observed cliamte. While interesting and areas for active research, they arent that relevant to climate for the next 100 years.

    That said, the broad picture for glacials with known (eg see fig 3 here from Hansen and Sato 2012) but disentangling the relative sources and influences of CH4,CO2 etc is work in progress.

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  29. tcflood,

    As John Hartz pointed out, the issue is really the assertion "and therefore represents a large source of unreliability in the models", which is begging the question and needs support.

    Back to your original complaint, which was that the statement

    to be skeptical of the arguments adduced for anthropogenic global warming you must be asserting that the principles of physics are wrong

    was an appeal to authority.

    You are attempting to suggest that the models may not necessarily accurately reflect the principles of physics and so therefore this claim is unwarranted.

    However, there is more than one way to skin a cat, and so it is with physical models. It turns out that while complicated GCMs are very important tools for assessing regional impacts and interactions within the climate system, you can actually go a very long way with a very simple energy balance model that clearly and obviously does implement basic physical principles and yet gives much the same result as full-blown GCMs do, at least on a global scale (and therefore for measures like global temperature anomaly). Hence the statement you objected to.

    In addition, we have empirical observations supporting the theory, and SkS has a page dedicated to the reliability of climate models. Note, however, that climate models form just one small part of the evidence for AGW. Nevertheless, courtesy of Barton Paul Levenson, here is a list of successful climate model predictions, each supported by links to the literature (as far back as 1896):

    That the globe would warm, and about how fast, and about how much.
    That the troposphere would warm and the stratosphere would cool.
    That nighttime temperatures would increase more than daytime temperatures.
    That winter temperatures would increase more than summer temperatures.

    Polar amplification (greater temperature increase as you move toward the poles).
    That the Arctic would warm faster than the Antarctic.
    The magnitude (0.3 K) and duration (two years) of the cooling from the Mt. Pinatubo eruption.
    They made a retrodiction for Last Glacial Maximum sea surface temperatures which was inconsistent with the paleo evidence, and better paleo evidence showed the models were right.

    They predicted a trend significantly different and differently signed from UAH satellite temperatures, and then a bug was found in the satellite data.
    The amount of water vapor feedback due to ENSO.
    The response of southern ocean winds to the ozone hole.
    The expansion of the Hadley cells.

    The poleward movement of storm tracks.
    The rising of the tropopause and the effective radiating altitude.
    The clear sky super greenhouse effect from increased water vapor in the tropics.
    The near constancy of relative humidity on global average.
    That coastal upwelling of ocean water would increase.

    Nobody would expect you to read all 161 previous postings, but it wouldn't hurt to check if the comments you want to make have already been addressed by any of them.

    Regarding peer-reviewed research: I, too, have seen some absolute rubbish published, and I have refereed papers as well. Everyone knows that simply appearing in the peer-reviewed literature is not a guarantee of quality (as evidenced by the rebuttals to certain papers on this very site). However, "the other side" either doesn't even manage to pass that hurdle, or when they do, what they publish doesn't say what they claim it does, or it ends up being one of those aforementioned rebutted papers. There is an enormous volume of research on the one side that all points to a consistent picture, and there is a tiny amount of work on the other side that is invariably inconsistent with each other and, almost invariably, fundamentally flawed, often even to a casual observer.

    (SkS even goes so far as to help people find the publications of the "other side", by person as well as by date, so they can see for themselves! Is there a better repository of anti-AGW research on the Internet?)

    It would be perverse indeed therefore to put the "two sides" on equal footing, regardless of how many bad papers you've seen published.

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  30. tcflood, you are in danger of finding yourself in the company of "skeptics" you claim to not belong with, because many of them exaggerate uncertainty.  There is a wide range of possible responses to the knowledge of current and coming climate change. Some are more disruptive and expensive than others.  The normal approach to decision making in any arena is to estimate the costs and benefits of each candidate course of action--with doing nothing being in fact one of those courses of action.  Then leaven that "value" (or more appropriately its (subjective) "utility") of each course of action with its probability (often more appropriately the "subjective probability"). 

    In the case of climate change, you should at least start by looking at the most probable climate change consequences (not 1 degree by 2100, not 6 degrees by 2100):  see "It's Not Bad".  Then evaluate which courses of action have expected values/utilities at least equal to the values/utilities of those most probable climate changes.

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  31. 174-180

    I am astounded by the quality of your responses. You have given me a lot to pursue and think about. Thank you all for taking the time to respond so thoughtfully.

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  32. tcflood,

    This is actually a better resource for finding peer-reviewed "skeptical" papers than those I gave before, sorted by subject matter. Click on the subject and SkS will list all the peer-reviewed papers known on that topic, categorised as pro-AGW, neutral, and "skeptical". If you know of any that haven't been included, you can just click on the buttons provided to add them to the database.

    Regarding clouds, I think an important point to make about the uncertainty surrounding them is that the uncertainty is likely because they don't seem to be a strongly positive or a strongly negative feedback. Clouds certainly do have a big impact, but it's the change in that impact in response to AGW that's uncertain, and the change so far has been minimal (very slightly positive feedback, if anything).

    In terms of physical principles, we have the direct warming caused by the increase in CO2 concentrations and the amplification of that warming by the increase in water vapour, which roughly doubles the CO2 impact. I have seen "skeptics" try to conflate water vapour feedback (which is both theoretically and empirically demonstrated) with the uncertainty surrounding cloud feedbacks (which is very hard to predict from first principles and must therefore be determined empirically) as a way of dismissing the water vapour feedback, but that is wrong.

    Beyond that we have a range of feedbacks with different levels of certainty. Just off the top of my head:

    1. Reduction in snow and ice is obviously a positive feedback due to lower albedo, and to make things worse, to date the rate of reduction seems to be grossly underestimated by models.

    2. Increased desertification is presumately a negative feedback (since deserts have higher albedo than vegetation), but I don't think it's enough to counter the loss of snow and ice (and doesn't seem like something to hope for anyway).

    3. Release of methane from continental shelfs and permafrost is a positive feedback.

    4. Reduction in the ability of the ocean to absorb CO2 with increasing temperature (and, eventually, outgassing of CO2 from the oceans when the temperature gets high enough) is a positive feedback.

    5. Changes in clouds, both in coverage and mix of types, is an unknown feedback but due to the lack of any real change to date should probably be assumed to be pretty much a wash (i.e. neither strongly positive or negative).

    One thing you'll find is that people who have an a-priori belief that the climate cannot possibly change too much (for religious reasons, in the case of one prominent "skeptical" scientist) go searching for possible negative feedbacks that might counteract all of those positive feedbacks, and clouds often feature high on their list. (Deserts, not so much.) Not because the evidence tells them that clouds must be a net negative feedback, but because the uncertainty surrounding clouds allows them to believe that they might be — wishful thinking, in other words.

    Presumably these same people don't take out insurance for much the same reason. Personally I prefer the Arab proverb, "Trust in God but tie up your horse".

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  33. tcflood, as an augmentation to the list of successful predictions that JasonB gave you, you might watch Ray Pierrehumbert's 2012 AGU lecture on successful (and unsuccesful) predictions; the Cliff Notes of that lecture have been typed up by Steve Easterbrook. For more details, read science historian Spencer Weart's "Discovery of Global Warming."

    I suspect your uncertainty about the uncertainty of climate models comes partly from your suspicion that the innards of those models are so complicated that nobody really knows how they work. So you should note that the list of successful predictions includes the most important ones having been made before those fancy computer models existed--all the way back to the 1800s. The early and successful projections were made decades before it was technically even possible to measure global temperature, so most definitely climatologists have not been merely modeling to match existing global temperature observations.  Instead, they model with fundamental, empirically supported, physics; they set up the Earth, then turn on the Sun and let the system evolve. 

    The fanciness in the models merely fine tunes the simple and robust projections.  Sufficiently scary projections can be made by hand calculating--as they were done before computers existed--and even many of the refinements can be done quickly with merely a spreadsheet to prevent hand cramps from penciling it all out.  Just two examples are Tamino's "Not Computer Models" and its followup "Once is Not Enough". For more examples, borrow or buy the short textbook by David Archer, "Global Warming: Understanding the Forecast". To accompany or replace that book, you can watch David's U. of Chicago class lectures for free. An explanation of models is summarized in a small set of short videos by the National Academy of Science.

    In case you've been reading blog gossip about climate models' computer code being of poor quality, you should read Steve Easterbook's excellent posts.

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  34. @Everyone:

    We have collectively given tcflood enough homeowork to sink a battleship. Please resist the urge to give him more. He/she is very polite and is open to learning more about climate science and related matters.   

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  35. tcflood,

    As John H has said, you've been given a lot to pursue, but if you are a trained chemist, then you should have the capacity and the interest to do the following, and I would highly recommend it:

    1) Completely restrain from making any judgment

    2) At least peruse Spencer Weart's The Discovery of Global Warming to understand how deep climate science is (it is not young or immature).

    2) Study the physics at the molecular level (vibrational modes of CO2, CH4, H2O, chemical and radiative interactions, etc.)

    3) Study the physics at the atmospheric level (concentrations, chemical reactions, energy and content transport mechanisms, etc.)

    4) Study the observational science, including: (a) paleoclimate methods such as O18, ice cores, ocean sediments, (b) how satellite and radiosonde measurements are done, and introduce error, (c) how ground observations are done

    5) With that foundation in the physics and chemistry, study the impact of the oceans,  including currents, heat transfer and chemistry (acidity), and physically constrained, large scale "oscillations" (like ENSO, PDO, etc.).

    6) With that foundation in the complete climate system physics and chemistry, study the feedback mechanisms (methane release, ecosystem changes, ice/albedo changes, Hadley Cell expansion, H2O and clouds, etc.)

    7) With that foundation in the physics and feedbacks, study the ice ages, what we know, and what we guess and why.  Be sure to search for and look at actual scientific papers, not just summaries and encyclopdic articles.

    8) With that foundation in the climate system physics, study the climate models themselves (there is a wealth of information available) in detail, to see how they incorporate the physics, how the allow for "unknowns", how they compensate for uncertainty, etc. to accurately model the earth climate over various time scales.

    9) With that foundation in the full body of knowledge about climate science -- while recognizing that you have only touched the surface of these many branches, while there are thousands of expert scientists, like yourself, trained in far, far, far more detail in each of them -- go back and look at your own questions, and decide for yourself if they are (a) naive, (b) ill-phrased, and (c) easily answered, once you know what we actually know about the physics, and how each aspect of the physics and other knowledge builds upon the foundations.

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  36. Oh, and somewhere in there, find time to study the carbon cycle, although at this point, anyone who disputes the anthropogenic origins of increased CO2 is really in total and complete denial.  It's the most glaring and inarguable fact there is.

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  37. Thanks John Hartz for your compassion – I am feeling a little overwhelmed. (And I am a “he”.) Rest assured, though, I am working on my homework. In the meantime maybe I can inquire about some issues that are bothering me.

    Tom Dayton hit it on the head when he said “your uncertainty … comes partly from your suspicion that the innards of those models are so complicated that nobody really knows how they work.” I would add “or if they really are working.” Please note, this is just thought gnawing at my gut - it is not an assertion. I have read large parts of “An introduction to Three-Dimensional Climate Modeling (2nd Ed) by W. M. Washington and C. L. Parkinson to try to get a more intuitive feel for how the models work. I got a good review (in truth, lost on me) of how to move differential equations from Cartesian to polar coordinates, but not much else.

    I have not worked hard enough at it yet, but have not yet been able to find what the input and output of these models are, so I have no idea of what is empirically parameterized and what is calculated from the initial conditions by basic principles. Thus, I have no response to skeptics when they claim the desired output is predetermined by the input. Correct me if I am wrong, (now there’s a thought ;-) but I got the impression that the computational mechanisms coupling the different spheres (atmosphere, hydrosphere, cryosphere, …) are crude (probably a consequence of computational limitations) . If so, might this be a place where the results could become distorted?

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    Moderator Response: [TD] For continued discussion of the narrower topic of model reliability, let's please move this discussion to the post "Models are Unreliable." (I will obey my own request.)
  38. tcflood,

    I have downloaded the GISS Model-E source code (it's freely available).  As a computer programmer with a background in both modeling and chemistry, I was readily able to read much of the code (although not many people could, and it's so much code and so complex that the most I could do is to browse).

    But it's like anything. If you understand how the models work (really understand, not just "have an intuitive feel" -- one which is probably very wrong) and what methods are used to overcome what problems, then you understand better that these models are far, far more reliable than you give them credit for.

    Example: Cartisian to polar coordinates.  That's kindergarten work for a climate model.  A model needs to divide the surface of the earth into cells, but it's not possible to divide the surface of a sphere into equal sized "squares".  It's non-Euclidean geometry.  There's an entire area of research focused on the various ways of trying to approximate the equal division of the surface of a sphere.  You don't have to, but if you don't, your cell-programming is vastly complicated because the dimensions, sides, angles and area of every cell will be different from its neighbors. All of this must be taken into account by a climate model.

    Note that very little is "parameterized," and what is parameterized makes sense.  It's done either because the input data just isn't available, or because the computational power required to work from the physics is overwhelming and yet does not improve the quality of the solution.

    I will correct you... The computational mechanisms are very, very, very far from crude.  DIfferent groups work on different models which are interconnected because no one group has the power to work with the complexity of the whole thing, but even so, each module has the complexity that decades of effort by teams of very, very bright people could put into such a thing.  Do you really think some guy thought it up over a weekend, and then just stopped there and started plugging in parameters?  Does that make any sense with how you know the rest of the world works?

    Climate modeling is very, very advanced, very intricate... and very fun.

    Links to pursue more about models:

    There are millions of more links, but... I would advise understanding the climate science (as per my earlier post) first, as well as perhaps beginning to learn more about programming.

    [FYI, I have very little time, but I have been working on and am eager to finish a series of posts on the models.  Push me and get me to do it!]

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  39. Sphaerica; (185)

    To greater or lesser extents, I have done some of several of the tasks on your list. As a calibration point for your second item 2), let me present here the content of an email I sent to a Swedish mathematician whose post on the greenhouse effect I ran across on the web.

    (Beginning)  Your analysis of the earth's blackbody (bb) radiation (bbr) and its interaction with the atmosphere makes no sense to me. Let's take the average temperature of the entire surface of the earth as a steady state value with insolation (shortwave, sw) as the energy input and thermal radiation (long wave, lw) from the earth plus the atmosphere and everything in it as the energy output to space. For simplicity, let’s ignore reflection. Clearly, the sw power in must equal the lw power out for a temperature steady state.

    Everyone seems to agree that it is a reasonable approximation to think of the earth as a bb radiator with a frequency distribution as a function of temperature as given by Planck. No one believes the atmosphere is a bb radiator. Greenhouse gases (ghg) absorb the earth's bbr at their respective specific vibrational frequencies and this energy is equilibrated among the usual statistical degrees of freedom of the molecule and its immediate environment, each event infinitesimally increasing the local temperature of the air. At that given temperature, the ghgs and only the ghgs re-emit at the same specific vibrational frequencies (not bbr) at a rate that depends on the local temperature of the air and at frequencies characteristic of the specific molecule. However, this radiation is emitted in all directions so almost half of it works its way back to the surface.

    Now, since the earth is a bb, it is a "perfect" absorber of any wavelength independent of the temperature of the bb. The emission wavelength profile is temperature dependent but the absorption is not. This is because absorption is almost exclusively from the vibrational ground state (large majority of molecules) to the excited state, while emission must originate form an excited state that must be thermally populated. The absorption and emission probabilities are identical; that is, if there were equal populations of ground states and excited states, the emission and absorption rates would be identical. So there is no problem with the earth reabsorbing the lwr coming from the ghg molecules in the air, since it emitted those frequencies in the first place.

    I can't figure out what all this stuff is about back radiation being non-physical because of some cut-off, but it doesn't seem to have any place in the real physical picture.

    Also, the climate sensitivity is the amount that the earth's average surface temperature goes up for a doubling of the concentration of ghgs (in CO2 equivalents). It is the shift in the earth's steady state temperature which is the outcome of all physical phenomena in the total atmospheric air column as a result of that one change. It cannot be estimated by one simple calculation of a fractional change in power transmitted by one CO2 molecule.

    In fact if you look at the spectrum of light passing into space at the top of the atmosphere (which has been done by satellite) there is very little radiation that makes it into space at the vibrational frequencies of the ghgs. This means that the earth's surface must become warmer in order to increase the power transmission of the remaining frequencies in order to re-establish the thermal steady state. (End)

    Does anyone have a good physical explanation (like I have presented above, not mathematical) of why the stratosphere must cool for the troposphere to heat during the greenhouse effect?

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  40. tcflood,

    What do you mean by "this stuff is about back radiation being non-physical because of some cut-off?"  To what does that refer?

    There are some flaws (deficiencies?) in your discussion of the behavior of the atmosphere.  The "all directions" thing shows (sorry) a very low level understanding of a complex system.  In particular, there are many types of molecules, and collisions happen many times faster (in the lower atmosphere) than re-radiation.  The first effect of CO2 is that CO2 absorbs IR, then passes that energy on to an O2 or N2 molecule (which has limited ability to emit energy as radiation), thus heating the surrounding atmosphere rather than simply re-emitting the radiation in all directions.

    Too, the density of the air changes, so you need to profile the atmosphere as an infinite series of layers.  Because of the difference in density and composition (to a very small extent), the behavior of each layer is different.

    You say:

    ...climate sensitivity ... cannot be estimated by one simple calculation of a fractional change in power transmitted by one CO2 molecule.

    Yes, and no.  You are right, estimating equilibrium climate sensitivity requires a far more complex model (or clever paleo studies).  But at the same time, you know that an understanding of just a few chemical equation gives you a good starting point to predicting the behavior of a solution of chemicals.  There are things you can do with that and things you can't.  Who is claiming otherwise?

    This is just a quick comment on your post... let me write another answering your question.  It's related to where I started in this comment.

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  41. tcflood,

    Does anyone have a good physical explanation (like I have presented above, not mathematical) of why the stratosphere must cool for the troposphere to heat during the greenhouse effect?

    Good question.  The moderators are going to yell at us for being off topic, and ask us to take it to another thread... which I'll do.  Please look here for your response.

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  42. I think model discussion should be moved to "are model reliable" thread.

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    Moderator Response: [DB] Yes; please move the individual components of this discussion to the most appropriate threads. This has gone beyond the topline scope of this thread for multiple topics.
  43. tcflood - You've raised many questions: I would direct you first to The Discovery of Greenhouse Warming, and in particular The Carbon Dioxide Greenhouse Effect; which proved clear explanations of many of these issues with links to primary references. 

    For another overview, RealClimate's post on The CO2 problem in 6 easy steps is also worth reading. 

    For tropospheric/stratospheric questions I will echo Sphaerica's suggestion.


    However, I'm a bit concerned.

    You state "Your analysis of the earth's blackbody (bb) radiation (bbr) and its interaction with the atmosphere makes no sense to me."  (emphasis added) - but after several paragraphs describing these interactions, you have raised no issues whatsoever in that regard. I would hesitate to go further in that regard until you actually pose some kind of question or concern, rather than roughly restating the obvious. 

    [ Note: The Earth is not a black-body (emissivity of 1.0), but in the IR wavelengths associated with thermal radiation at surface temperatures, it has an emissivity of 95-99% depending on local surface; and that calculation matches measurements. ]

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  44. The problems with your understanding of the presentation of the greenhouse effect presented above is that you missed the context. I stated that this is a direct quotation of an email to a contrarian and my comments about something not making sense are directed to him. I had hoped that you would read carefully enough to discern the context and figure out the gist of his ideas that I was rebutting.

    Also, KR (193)

    95-99: emissivity is not a black body for purposes of a discussion where we are ignoring reflection?

    Also, Sphaerica (188, 190)

    If you take the time to actually read what I have written, you will see that all of your criticisms are baseless because all of what you are contending is missing is actually there.

    Oh, and also, I didn’t say that computational mechanisms might be crude, I said that the computational mechanisms of coupling spheres might be crude. Do you really think that I think that “some guy thought it up over a weekend, and then just stopped there and started plugging in parameters?” But then you have actually read some of the code so I would clearly be foolish not to accept your assertions about the validity of models.

    I was hoping to have found a place where I could ask honest questions and have honest discussions. All I am getting are corrections of errors that are from faulty reading of what I have written and insufferable condescension.

    Like Arnold didn’t say, “I won’t be back.”

    Moderator: please remove me from your site.

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  45. tcflood - Regarding reflection (albedo), in the SW frequencies it's about 30% reflection. Again, a number that is easy to find if any effort is put forth, and one of the components leading to the 240 W/m2 average insolation. Why have you not looked this up???

    I hate to say this, but since you have not actually posed any questions or concerns regarding the greenhouse effect, but rather talked a lot about uncertainties without either quantifying said uncertainties, or conveying much of substance, I would at this time regard you as a concern troll


    I would be more than willing to be proven wrong, mind you - but that's going to take some actual questions or assertions on your part, rather than vague 'concerns' and run-on postings. 

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  46. tcflood,

    I was hoping to have found a place where I could ask honest questions and have honest discussions.

    That's not how it looks to me, based entirely on your own posts.  You listed 5 common, low-level denial arguments that are very easily rebutted just by using the Search box and following the links.  None of them required interaction with or interjection by people who have a deep understanding of the climate science.

    Yet people engaged you anyway, and gave you a wealth of information that a trained chemist should be able to easily absorb.

    All you did in response was to change the subject and list more and more denial arguments.  I put a lot of time into creating this response for you, directly answering your question, in the fashion you requested (no math), using a frame of reference (chemistry) that should be right up your alley.

    You apparently did not even read it, let alone respond.  Instead, you decided to take your ball and go home in a huff.

    Your behavior suggests another agenda, that you were never really here to ask questions or to learn.  All you did was to clutter up this thread with off-topic denial sloganeering (all of which, if strictly subject to the site's Comments Policy, should be deleted).

    People responded, and you never once provided a counter-argument or delved more deeply into any subject.  You simply got angry, complained, or more often than that rushed to change the subject to yet another silly denial argument.

    Sorry, but based on your own behavior, visible to all, you'll get no sympathy here.  Your understanding of climate science is abysmal.  I know high school students with a deeper grasp of the science than you have demonstrated.  If you wish to be respected for your knowledge and understanding, then it needs to be adequately developed.

    Your decision to stop posting is probably the correct one.  However your decision to leave, without taking the time to learn exactly how much you fail to properly understand, is ill-advised.

    More people need to spend more time reading and learning instead of gettting angry because their ignorance is not given "due respect."

    Asking honest questions is always welcome.

    Asking questions with no intention of listening to the answers is not.

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  47. We are told the data for Figure 4 (total global heat content) are from Church et al 2011, but could you spell out how the graph is constructed, please.  Is it from Figure 3a in Church 2011 - ocean warming (blue + red), and warming of the atmosphere and land plus melting ice (green)?  There is approximately a ten-fold difference in the Y axes (0-250 versus 0-2000 x10^21 J).

    Ii seems to me that Figure 4 is THE graph - because it shows total global warming.  If not, why not?  If yes, why is it not given more prominence (like on your home page and in summaries of climate change)?  Has it been published in a peer-reviewed journal (other than hidden within Fig 3a in Church 2011)?  If not, why not?

    Emphasing change in global surface temperature (as in The Escalator) helps denialists because of the large variation in surface temperature (see The Escalator).  Change in total global heat content has much less variability.  Global surface temperature has a more immediate effect on humans than total global heat content and is less difficult to measure - but these reasons do not justify using the wrong measure (if total global heat content really is the best single measure).

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  48. Interesting !

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  49. Have updated the Norwegian translation!

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  50. "Arguments to the contrary are superficial"

    The actual temperature record shown in the HadCRU4 measurements for the last ten years are not an argument.  They are actuals.  The end of the series in 2013-2014 is turning down.  Global Warming from ANY cause is not happening.  The next two years and beyond will show that arguments are not necessary.

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    Moderator Response:

    [PS] You are continuing to spam threads. Any more will be deleted. You also clearly havent actually read the article or you would realize that you are making a superficial argument. Please take some time to understand the science (we provide the resource here) if you want to have a constructive discussion. If your intent is to bomb threads with uninformed comment and not engage with discussion, then you will be banned.

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