The core of the climate debate: how much of the past warming did we cause?

Summary:  Today we have a post by Judith Curry, a leading climate scientist, going to the very heart of the debate: how much of the warming since 1950 results from us? Before making predictions, how confidently can we see our past?

Climate change presents one of the greatest challenges in humanity’s history. To accurately assess long slow changes in Earth’s biosphere, discerning the effects of our effects from natural cycles. Equally difficult, our political machinery must accurately see the conclusions of climate scientists, and take appropriate steps. These are largely sociological processes, called upon to work on a level seldom seen in our past.

Voltaire: Doubt & Certainty

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Contents

  1. The 50-50 argument
  2. About Judith Curry
  3. Vital info about climate change
  4. For More Information
  5. Advice from Bertrand Russell

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The 50-50 argument

by Judith Curry, at her website Climate Etc
24 August 2014
Posted here under her Creative Commons license

(a)  Choose which hypothesis you prefer

Pick one:

  1. Warming since 1950 is predominantly (more than 50%)  caused by humans.
  2. Warming since 1950 is predominantly caused by natural processes.

When faced with a choice between 1 and 2,  I respond:  ‘I can’t choose, since i think the most likely split between natural and anthropogenic causes to recent global warming is about 50-50′.  Gavin thinks I’m ‘making things up’ {see the discussion in comments here}, so I promised yet another post on this topic.

For background and context, see my previous 4 part series Overconfidence in the IPCC’s detection and attribution.

(b)  Framing

The IPCC’s AR5 (2014) attribution statement:

It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together. The best estimate of the human induced contribution to warming is similar to the observed warming over this period.

I’ve remarked on the ‘most’ (previous incarnation of ‘more than half’, equivalent in meaning) in my Uncertainty Monster paper: “Further, the attribution statement itself is at best imprecise and at worst ambiguous: what does “most” mean – 51% or 99%?” Whether it is 51% or 99% would seem to make a rather big difference regarding the policy response.  It’s time for climate scientists to refine this range.

I am arguing here that the ‘choice’ regarding attribution shouldn’t be binary, and there should not be a break at 50%; rather we should consider the following terciles for the net anthropogenic contribution to warming since 1950: >66%, 33% – 66%, <33%.  Hence 50-50 refers to the tercile 33-66% (as the midpoint)

Note:   I am referring only to a period of overall warming, so by definition the cooling argument is eliminated.  Further, I am referring to the NET anthropogenic effect (greenhouse gases + aerosols + etc).   I am looking to compare the relative magnitudes of net anthropogenic contribution with net natural contributions.

Further, by global warming I refer explicitly to the historical record of global average surface temperatures.  Other data sets such as ocean heat content, sea ice extent, whatever, are not sufficiently mature or long-range (see Climate data records: maturity matrix).   Further, the surface temperature is most relevant to climate change impacts, since humans and land ecosystems live on the surface.  I acknowledge that temperature variations can vary over the earth’s surface, and that heat can be stored/released by vertical processes in the atmosphere and ocean.  But the key issue of societal relevance (not to mention the focus of IPCC detection and attribution arguments) is the realization of this heat on the Earth’s surface.

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I Love Certainty

(c)  What the IPCC says

Before getting into my 50-50 argument, a brief review of the IPCC perspective on detection and attribution.  For detection, see my post Overconfidence in IPCC’s detection and attribution. Part I.

Let me clarify the distinction between detection and attribution, as used by the IPCC. Detection refers to change above and beyond natural internal variability. Once a change is detected, attribution attempts to identify external drivers of the change.

The reasoning process used by the IPCC in assessing confidence in its attribution statement is described by this statement from the AR4 (2007):

“The approaches used in detection and attribution research described above cannot fully account for all uncertainties, and thus ultimately expert judgement is required to give a calibrated assessment of whether a specific cause is responsible for a given climate change. The assessment approach used in this chapter is to consider results from multiple studies using a variety of observational data sets, models, forcings and analysis techniques. The assessment based on these results typically takes into account the number of studies, the extent to which there is consensus among studies on the significance of detection results, the extent to which there is consensus on the consistency between the observed change and the change expected from forcing, the degree of consistency with other types of evidence, the extent to which known uncertainties are accounted for in and between studies, and whether there might be other physically plausible explanations for the given climate change.

Having determined a particular likelihood assessment, this was then further downweighted to take into account any remaining uncertainties, such as, for example, structural uncertainties or a limited exploration of possible forcing histories of uncertain forcings. The overall assessment also considers whether several independent lines of evidence strengthen a result.” (IPCC AR4)

I won’t make a judgment here as to how  ‘expert judgment’ and subjective ‘down weighting’ is different from ‘making things up’

AR5 Chapter 10 has a more extensive discussion on the philosophy and methodology of detection and attribution, but the general idea has not really changed from AR4. In my previous post (related to the AR4), I asked the question: what was the original likelihood assessment from which this apparently minimal downweighting occurred?   The AR5 provides an answer:

The best estimate of the human induced contribution to warming is similar to the observed warming over this period.

So, I interpret this as scything that the IPCC’s best estimate is that 100% of the warming since 1950 is attributable to humans, and they then down weight this to ‘more than half’ to account for various uncertainties.  And then assign an ‘extremely likely’ confidence level to all this.

Making things up, anyone?

I’ve just reread Overconfidence in IPCC’s detection and attribution. Part IV, I recommend that anyone who seriously wants to understand this should read this previous post.  It explains why I think the AR5 detection and attribution reasoning is flawed.

Of particular relevance to the 50-50 argument, the IPCC has failed to convincingly demonstrate ‘detection.’  Because historical records aren’t long enough and paleo reconstructions are not reliable, the climate models ‘detect’ AGW by comparing natural forcing simulations with anthropogenically forced simulations.  When the spectra of the variability of the unforced simulations is compared with the observed spectra of variability, the AR4 simulations show insufficient variability at 40-100 yrs, whereas AR5 simulations show reasonable variability.  The IPCC then regards the divergence between unforced and anthropogenically forced simulations after ~1980 as the heart of the their detection and attribution argument.  See Figure 10.1 from AR5 WGI: (a) is with natural and anthropogenic forcing; (b) is without anthropogenic forcing:

IPCC AR5: Figure10-1a

IPCC AR5: Figure10-1b
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Note in particular that the models fail to simulate the observed warming between 1910 and 1940.

The glaring flaw in their logic is this.  If you are trying to attribute warming over a short period, e.g. since 1980, detection requires that you explicitly consider the phasing of multidecadal natural internal variability during that period (e.g. AMO, PDO), not just the spectra over a long time period.  Attribution arguments of late 20th century warming have failed to pass the detection threshold which requires accounting for the phasing of the AMO and PDO.  It is typically argued that these oscillations go up and down, in net they are a wash.  Maybe, but they are NOT a wash when you are considering a period of the order, or shorter than, the multidecadal time scales associated with these oscillations.

Further, in the presence of multidecadal oscillations with a nominal 60-80 yr time scale, convincing attribution requires that you can attribute the variability for more than one 60-80 yr period, preferably back to the mid 19th century.  Not being able to address the attribution of change in the early 20th century to my mind precludes any highly confident attribution of change in the late 20th century.

(d)  The 50-50 argument

There are multiple lines of evidence supporting the 50-50 (middle tercile) attribution argument.  Here are the major ones, to my mind.

(d1) Sensitivity

The 100% anthropogenic attribution from climate models is derived from climate models that have an average equilibrium climate sensitivity (ECS) around 3C.  One of the major findings from AR5 WG1 was the divergence in ECS determined via climate models versus observations.  This divergence led the AR5 to lower the likely bound on ECS to 1.5C (with ECS very unlikely to be below 1C).   Nic Lewis at Climate Dialogue summarizes the observational evidence for ECS between 1.5 and 2C, with transient climate response (TCR) around 1.3C.

Nic Lewis has a comment at Bishop Hill on this:

The press release for the new study (Science, 22 August 2014) states: “Rapid warming in the last two and a half decades of the 20th century, they proposed in an earlier study, was roughly half due to global warming and half to the natural Atlantic Ocean cycle that kept more heat near the surface.” If only half the warming over 1976-2000 (linear trend 0.18°C/decade) was indeed anthropogenic, and the IPCC AR5 best estimate of the change in anthropogenic forcing over that period (linear trend 0.33Wm-2/decade) is accurate, then the transient climate response (TCR) would be little over 1°C. That is probably going too far, but the 1.3-1.4°C estimate in my and Marcel Crok’s report “A Sensitive Matter” is certainly supported by Chen and Tung’s findings.

Since the CMIP5 models used by the IPCC on average adequately reproduce observed global warming in the last two and a half decades of the 20th century without any contribution from multidecadal ocean variability, it follows that those models (whose mean TCR is slightly over 1.8°C) must be substantially too sensitive.

BTW, the longer term anthropogenic warming trends (50, 75 and 100 year) to 2011, after removing the solar, ENSO, volcanic and AMO signals given in Fig. 5 B of Tung’s earlier study (freely accessible here), of respectively 0.083, 0.078 and 0.068°C/decade also support low TCR values (varying from 0.91°C to 1.37°C), upon dividing by the linear trends exhibited by the IPCC AR5 best estimate time series for anthropogenic forcing. My own work gives TCR estimates towards the upper end of that range, still far below the average for CMIP5 models.

If true climate sensitivity is only 50-65% of the magnitude that is being simulated by climate models, then it is not unreasonable to infer that attribution of late 20th century warming is not 100% caused by anthropogenic factors, and attribution to  anthropogenic forcing is in the middle tercile (50-50).

The IPCC’s attribution statement does not seem logically consistent with the uncertainty in climate sensitivity.

(d2) Climate variability since 1900

From HadCRUT4:

HadCRUT4

The IPCC does not have a convincing explanation for:

  1. warming from 1910-1940
  2. cooling from 1940-1975
  3. hiatus from 1998 to present

The IPCC purports to have a highly confident explanation for the warming since 1950, but it was only during the period 1976-2000 when the global surface temperatures actually increased.

The absence of convincing attribution of periods  other than 1976-present to anthropogenic forcing leaves natural climate variability as the cause – some combination of solar (including solar indirect effects), uncertain volcanic forcing, natural internal (intrinsic variability) and possible unknown unknowns.

A key issue in attribution studies is to provide an answer to the question:  When did anthropogenic global warming begin?  As per the IPCC’s own analyses, significant warming didn’t begin until 1950.  Just the Facts has a good post on this When did anthropogenic global warming begin? {also see this post, with links to authoritative sources}

The temperature record since 1900 is often characterized as a staircase, with periods of warming sequentially followed by periods of stasis/cooling.  The stadium wave and Chen and Tung papers, among others, are consistent with the idea that the multidecadal oscillations, when superimposed on an overall warming trend, can account for the overall staircase pattern.

Lets consider the 21st century hiatus.  The continued forcing from CO2 over this period is substantial, not to mention ‘warming in the pipeline’ from late 20th century increase in CO2.  To counter the expected warming from current forcing and the pipeline requires natural variability to effectively be of the same magnitude as the anthropogenic forcing.  This is the rationale that Tung used to justify his 50-50 attribution (see also Tung and Zhou).  The natural variability contribution may not be solely due to internal/intrinsic variability, and there is much speculation related to solar activity.  There are also arguments related to aerosol forcing, which I personally find unconvincing (the topic of a future post).

The IPCC notes overall warming since 1880.  In particular, the period 1910-1940 is a period of warming that is comparable in duration and magnitude to the warming 1976-2000.  Any anthropogenic forcing of that warming is very small (see Figure 10.1 above).  The timing of the early 20th century warming is consistent with the AMO/PDO (e.g. the stadium wave; also noted by Tung and Zhou).  The big unanswered question is:  Why is the period 1940-1970 significantly warmer than say 1880-1910?   Is it the sun?  Is it a longer period ocean oscillation?  Could the same processes causing the early 20th century warming be contributing to the late 20th century warming?

Not only don’t we know the answer to these questions, but no one even seems to be asking them!

(e)  Attribution

I am arguing that climate models are not fit for the purpose of detection and attribution of climate change on decadal to multidecadal timescales.  Figure 10.1 speaks for itself in this regard (see figure 11.25 for a zoom in on the recent hiatus).  By ‘fit for purpose’, I am prepared to settle for getting an answer that falls in the right tercile.

The main relevant deficiencies of climate models are:

  1. climate sensitivity that appears to be too high, probably associated with problems in the fast thermodynamic feedbacks (water vapor, lapse rate, clouds)
  2. failure to simulate the correct network of multidecadal oscillations and their correct phasing
  3. substantial uncertainties in aerosol indirect effects
  4. unknown and uncertain solar indirect effects

So, how to sort this out and do a more realistic job of detecting climate change and and attributing it to natural variability versus anthropogenic forcing?  Observationally based methods and simple models have been underutilized in this regard.  Of great importance is to consider uncertainties in external forcing in context of attribution uncertainties.

The logic of reasoning about climate uncertainty, is not at all straightforward, as discussed in my paper Reasoning about climate uncertainty.

So, am I ‘making things up’?  Seems to me that I am applying straightforward logic.  Which IMO has been disturbingly absent in attribution arguments, that use  climate models that aren’t fit for purpose, use circular reasoning in detection,  fail to assess the impact of forcing uncertainties on the attribution, and are heavily spiced by expert judgment and subjective downweighting.

—————————–  End of Professor Curry’s article  —————————–

The demand for certainty is one which is natural to man, but is nevertheless an intellectual vice. … To endure uncertainty is difficult, but so are most of the other virtues.

— Bertrand Russell, Philosophy for Laymen (1946)

Judith Curry

(2) About Judith Curry

Judith Curry is Professor and Chair of the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology. She is also President and co-owner of Climate Forecast Applications Network (CFAN). Prior to joining the faculty at Georgia Tech, she served on the faculty of the University of Colorado, Penn State University and Purdue University.

She serves on the NASA Advisory Council Earth Science Subcommittee and the DOE Biological and Environmental Science Advisory Committee. She recently served on the National Academies Climate Research Committee and the Space Studies Board, and the NOAA Climate Working Group.

She is a Fellow of the American Meteorological Society, the American Association for the Advancement of Science, and the American Geophysical Union.

Her views on climate change are best summarized by her recent Congressional Testimony:

  1. Policy Relevant Climate Issues in Context, April 2013
  2. Rational Discussion of Climate Change: the Science, the Evidence, the Response, November 2010

(3) A few important things to remember about global warming

Please read this before commenting about my views about global warming and climate change. It also has links to the key posts on the FM website on this topic, which in turn link to a wide range of authoritative sources (mostly the IPCC, the major climate agencies, and the peer-reviewed literature).

Truth Will Make You Free

(4) For More Information

(a)  Reference Pages about climate on the FM sites:

  1. The important things to know about global warming
  2. My posts
  3. Studies & reports, by subject
  4. The history of climate fears

(b)  Key posts about the climate change debate:

  1. When did we start global warming? See the surprising answer., 18 October 2012
  2. Still good news: global temperatures remain stable, at least for now., 14 October 2012
  3. Scientists explore causes of the pause in warming, perhaps the most important research of the decade, 17 January 2014
  4. One of the most important questions we face: when will the pause in global warming end?, 25 August 2013

(c)  Speaking about the past, are we prepared for past weather?

  1. Have we prepared for normal climate change and non-extreme weather?, 11 February 2014
  2. Droughts are coming. Are we ready for the past to repeat?, 12 March 2014

(d)  Posts about extreme weather:

  1. Ignorance and propaganda about extreme climate change, 10 July 2012
  2. A look behind the curtain at the news of extreme climate events in the US, 22 August 2012
  3. Hurricane Sandy asks when did weather become exceptional? (plus important info about US hurricanes), 28 October 2012
  4. Has global warming increased the frequency & virulence of extreme weather events?, 10 February 2013
  5. The Oklahoma tornadoes can teach us about our climate, and ourselves, 22 May 2013
  6. The IPCC gives us straight talk about Extreme Weather, 4 October 2013
  7. The IPCC rebukes the climate doomsters. Will we listen?, 15 October 2013
  8. A summary of the state of climate change and extreme weather, 12 December 2013
  9. Worst case scenarios versus fat tails: a discussion about climate change, 23 April 2014

(5)  Advice from the past, from the philosopher Bertrand Russell

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Bertand Russell: Certainty & Doubt

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29 thoughts on “The core of the climate debate: how much of the past warming did we cause?

  1. I guess this was interesting, except I don’t think this question is important. Who cares if climate change is caused by human activity or natural phenomena? Who cares if it is only 10% our fault? The important question is whether we will do anything that will cause short term discomfort and economic hardship to help mitigate the effects. It is whether we will do nothing but argue about whether it is occurring, or whether we caused it, not who or what is to blame, that matters.

    1. Gbutera,

      I do not understand your comment. We can only mitigate CO2 emissions, practically speaking. If they are, perchance, a minor part of the two century long warming — then we have to focus our efforts on adaptation.

      That is a large and important policy decision. Resources are limited, and either course will be expensive.

    2. At the top of your post you write this post is “going to the very heart of the debate: how much of the warming since 1950 results from us?” Does it really matter whether climate change is caused by human activity or is a natural phenomena? Not if the result is the same, and the damage and weather changes that we have to deal with are the same. The “debate” in political circles, if they even bother to bring up the issue, so often seems to be whether its happening at all because politicians don’t get elected by encouraging self-sacrifice or advocating for reducing anyone’s standard of living.

      Mitigating CO2 emissions is only one tool available. And regardless, we are going to have to both mitigate and adapt.

    3. Gbutera,

      If the warming is largely natural and will continue, reducing CO2 emissions will have little effect. Hence the ficus must be on adaptation.

      If the warming is largely natural and cyclical, little or no action is needed.

      Note that some trends, such as rising sea levels, are clearly long-term in nature (albeit might be accelerated by CO2-induced warming), and must be adapted to.

  2. Yup. I’m sure that burning over 90 million barrels of oil every single day, 3.3 trillion cubic meters of natural gas, and 8.4 billion tons of coal every year (as of 2013 – these figures increase by growing margins every year) has very little to do with it… And I’m pretty sure that cutting down 50% global forest cover since 1950 has a pretty negligible impact as well…

    1. Thothinexile,

      I feel sorry for people who write such rants. Hysteria? Irrationality?what are you attempting to say? To what is this a rebuttal? Perhaps to the voices in your head. Certainly to nothing in this post.

      Re: land use changes — irony alert

      Distinguished climate scientists, such as Roger Pielke Sr, said that anthropogenic land use change was an important but unappreciated driver of climate change (he also pointed to the ocean’s role as a heat sink, now considered one of the major factors causing the pause). For this cutting edge science the “climate activists” (ideologically driven, ignorant) branded him a “denier” (e.g., at Skeptical Science).

      Now, as research proves him right, no apologies. Ideologues never say they’re sorry.

  3. I did read it. It contains claims that are simply untrue, ie: “the surface temperature is most relevant to climate change impacts” – not so. Ocean heat content is extremely significant because it hastens the melting of arctic sea ice – an important feedback tipping point trigger due to the flipping of albedo and destabilization of methane hydrate on the arctic ocean floor, not to mention the jet stream which is driven by temperature gradient between the poles and lower latitudes, also ocean heat content is weakening thermohaline currents which may result in short-term regional cooling in some areas.
    ” The IPCC then regards the divergence between unforced and anthropogenically forced simulations after ~1980 as the heart of the their detection and attribution argument.” For good reason: http://www.sciencedirect.com/science/article/pii/S0921818113000908

    “climate sensitivity that appears to be too high, probably associated with problems in the fast thermodynamic feedbacks (water vapor, lapse rate, clouds)” How about ice for a thermodynamic feedback? https://www.youtube.com/watch?v=20pjigmWwiw

    I do not doubt that Dr. Curry is well educated and informed but she dissents with the overwhelming majority of expert scientists. A paper co-authored by Dr. James Hansen in 2013 showed long term natural cooling trend over the past 50 million years: “A climate forcing due to a CO2 change from 1000 to 170 ppm is more than 10 W m−2, which compares with forcings of the order of 1 W m−2 for competing climate forcings during the Cenozoic era [5], specifically long-term change of solar irradiance and change of planetary albedo (reflectance) owing to the overall minor displacement of continents in that era.” http://rsta.royalsocietypublishing.org/content/371/2001/20120294.full

    Just what are the chances that all of a sudden this 50+ million year natural long term cooling trend dramatically reversed and just happens to coincide with human industrial, petro-energy driven economic growth goes exponential?

    I am not a scientist. I have a Masters’s degree in philosphy but I have read extensive scientific literature with an open mind and the evidence of AGW is crystal clear.

    1. thotinexile-“Just what are the chances that all of a sudden this 50+ million year natural long term cooling trend dramatically reversed and just happens to coincide with human industrial, petro-energy driven economic growth goes exponential? ”

      And just what conclusions can you draw, comparing 50million years with 20? None whatsoever. Given the uncertainty in the data and the lack of research into how the climate actually works- thanks to the IPCC focus only on the human-caused basis for climate change. If they had first bothered to focus on research that aimed to understand how the climate works we might know where we stand. As it is, that research is only now really taking off since all the numeric climate models have essentially gone off the rails.

    2. Logical chemist,

      I appreciate your attempt go reason with this person, but my experience (from answering thousands of comments) is that it is a waste of time.

      The specific quote you respond to is daft, him (or her) just making stuff up. The temperature record of the past 50 million years is nothing like a “a long cooling trend.” It shows many warming periods, ones larger and longer than that of the past 2 centuries.

  4. You know perfectly well the original comment is a rebuttal to the notion that climatic changes are not predominantly human caused. Come on. As the editor of this blog you ought not to simply insult people who post comments critical of your articles.

    1. No, I don’t care to rely on Youtube videos. I rely on the IPCC, the major climate agencies, and the peer-reviewed literature.

      People who get their info from alarmists say things like rate of decrease in arctic sea ice has “gone parabolic” (no, it’s quite linear) and that the the rate of climate change has “accelerated” (not it hasn’t) are in my experience both wrong and hopeless. Ditto for laypeople who think they know so much more than professional climate scientists (they just don’t understand the discussion).

      I have had hundreds of these conversations. I go thru the drill of citing the IPCC, agencies, and literature — their faith-based views remain unshaken.

      My guess is that the current debate among scientists (about things which you don’t understand and don’t see, such as climate sensitivity to rising CO2) will continue until the pause ends — years or decades from now. It’s length and the following rate of warming will answer the current debates.

      Your initial point was about oil subsidies. Which is a point I’ve long raised — that we’d be better off in multiple dimensions if we invested in R&D for non-carbon-based energy sources. But the energy and climate debates have been seized by ideologues on Left and Right, immune to data and logic. We’re doing little to prepare for the future, and they’re almost guaranteeing that nothing will be done for the foreseeable future.

      Such is life.

    1. I have lost interest in your fantasy of being a climate scientist. Please provide a cite for your claim of “parabolic” decrease in arctic sea ice — and from a major climate agency or peer-reviewed research. Not you fellow alarmists.

      Meanwhile the National Snow and Ice Data Center publishes monthly graphs of arctic sea ice, with a linear trend line. It fits quite well. Certainly not an ascending curve.
      http://nsidc.org/arcticseaicenews/files/2014/08/Figure3.png

  5. Also, the IPCC is quite conservative by its own admission. Its projections include human emissions only and exclude the risks of natural feedbacks, as shown in Fig 12.28b, observations have significantly exceeded their projections.

    In 2007, the IPCC noted “the risk of climate feedbacks is generally not included in the above analysis. Therefore, the emissions reductions to meet a particular stabilization level reported in the mitigation studies assessed here might be underestimated” (IPCC 2007, 173)” https://www.ipcc.ch/pdf/assessment-report/ar4/wg3/ar4_wg3_full_report.pdf

    Yet they still projected warming to exceed 2C by 2100 even on these conservative estimates.

    In my opinion, that’s pretty legitimate cause for “alarm”.

    1. So you’re alarmed. You’re just another one in the club. One of the major themes of the FM website has been that Americans (its focus) these days tend to range from alarmed (by an astonishingly wide range of things) to pants-wetting fear. It’s some form of disorder we’ve fallen into. It makes us easily manipulated.

      “as shown in Fig 12.28b, observations have significantly exceeded their projections.”

      Congratulations. Out of the scores of variables AR5 measures, you found one for which their projections have been conservative: northern hemisphere sea ice. On the other hand, they underestimated southern hemisphere sea ice (which since AR5’s publications has set new record maximums). For neither is warming the only, perhaps not the major factor. As important are winds, long cycles (AMO, PDO), and for the arctic — soot (pollution). It’s not an example supporting your fears (or rather, it shows that your thinking is just seeking confirmation for your fears).

      “Arctic sea ice is declining rapidly. The rate of decline has gone parabolic.”

      It’s declining; rapidly is not a precise term (especially as we have good records only since 1979, so no historical comparisons). No, the rate of decline has not gone “parabolic” (that’s a term of math, no matter if it’s used in the cartoons you rely on). It is somewhat linear.

      For details see the links to research in section 8 here, or the posts about arctic sea ice.

      About the IPCC being “conservative”

      I don’t know how to measure or evaluate measure such a claim. For the IPCC’s most important projections — surface atmosphere temperature — actuals have come in at the lower end of their broad range of projections. The opposite of conservative.

      By the way — the IPCC has reported their conclusions in many forms as their work as evolved. But they’ve been clear on one thing from the start, repeated in each generation of reports…

      “Scenarios are not predictions of the future and should not be used as such.”
      — IPCC’s “Climate Change 1992”

      “Scenarios are images of the future or alternative futures. They are neither predictions nor forecasts.”
      — “Report on Emissions Scenarios (2000)

  6. 1)The points in your NSIDC graph are pulling pretty far below the ‘linear’ line recently..

    2) Northern Hemisphere sea ice is of much greater concern than southern hemisphere sea ice because there is a huge and very dangerous quantity of methane hydrate under the arctic ocean (at least 5000 GT according to The Copenhagen Diagnosis 2009).

    3) Ocean temperatures are at least as important as surface temperatures – sea ice floats on ocean water and thus warmer waters will increase the rate of melt. Secondly, ocean temperatures drive thermohaline currents and jet streams that we rely on for consistent precipitation patterns to produce food. I ought not need to say more on this point.

    I anticipate you’ll respond by noting sea ice extent has recovered a bit in the north and is growing around antarctica. Growth of sea ice extent is very misleading, a much better measure is sea ice volume – the thickness and age of ice, which data abundantly shows, sea ice is thinning and the oldest ice is disappearing. Sea ice extent is a precarious, it is not a good indication of how long polar ice is likely to remain. Another factor to be considered is the rate of melt of land ice – in Greenland and West Antarctica, land based glaciers are retreating and thinning faster every year.

    4) You, Mr. Editor of the Fabius Maximus Website, use alarmist rhetoric to describe the collapse of democracy and the corrosion of the rule of law and the Constitution in the United States.
    “The Republic slides another step into Darkness” – Aug 28 on the growth of the police state…

    I could cite dozens of examples of your own ‘alarmist’ and fearful rhetoric. I’m not criticizing your discourse because I agree with your assessments on those matters. I’m trying to point out that there is some hypocrisy in your dismissive and somewhat condescending criticism of climate “alarmists” when you yourself use language that some would consider quite alarmist.

    There are good reasons to be alarmed about these things, the things we agree on as well as climate change. Alarm doesn’t mean succumbing to apathy and demagoguery, it can and should be a call to action.

    1. We’re now into the usual “alarmists making stuff up” phase. Before the rebuttals, you still have not supported your “parabolic” statement about arctic sea ice. You could at least tell us what cartoonish alarmist website you got it from.

      (1) “The points in your NSIDC graph are pulling pretty far below the ‘linear’ line recently”

      Sea ice is a noisy data series, which is why they draw a trend line. Also, your timing is lousy. See August:
      .
      [caption id="attachment_71471" align="aligncenter" width="350"]NSIDC: August 2014 arctic sea ice NSIDC[/caption]

      (2) “Northern Hemisphere sea ice is of much greater concern than southern hemisphere sea ice”

      I’ve said that many times. Your point is what?

      (3) “Ocean temperatures are at least as important as surface temperatures…”

      Pretending to be a climate scientist again!

      (4) “I anticipate you’ll respond”

      Since you appear to understand nothing from the authorities I’ve cited, I’ll skip this.

      (5) “use alarmist rhetoric to describe the collapse of democracy”

      I cite a large and body of evidence, from which readers can make up their own minds. That’s different from you just making stuff up.

  7. Well, here’s a few ‘cartoons’ for you: How about the US Navy (one of my saturday morning favorites as a kid ;)? http://www.researchgate.net/publication/234145875_The_Future_of_Arctic_Sea_Ice/file/9c96051fabe025feb4.pdf

    Or The Guardian? http://www.theguardian.com/environment/2014/aug/24/incredible-polar-ice-loss-cryosat-antarctica-greenland

    Or Dr. Jennings
    http://sustainablepalouse.org/docs/M_Jennings_Worst_Case_Scenario.pdf

    Or Dr. Jason Box, who recently warned that if only a fraction of the arctic methane hydrate is destabilized “we’re fucked” – http://www.dailymail.co.uk/sciencetech/article-2719727/Were-f-ked-Climate-change-catastrophe-mankind-study-shows-methane-leaking-Arctic-Ocean-scientist-warns.html

    This guy was the LEAD author of the Greenland chapters of the NOAA annual State of the Climate report for 5 consecutive years, published over 60 peer reviewed papers, and is a lot more prestigious and authoritative than Judith Curry! Oh but I’m sure you’ll either ignore this point or find some angle from which to frame Dr. Box as a clownish fearmonger..

    So far you have dismissed the notion that anything other than surface temperatures matter, ignored my points about ice volume and age and refused to acknowledge your brazen hypocrisy on vitriolic, alarming rhetoric. Your posts are just condescending and insulting and you simply ignore points you don’t wish to engage!

    Not to mention, you accuse me of ‘making stuff up’ which is outrageously false as anyone who may be reading this thread can see, every one of my posts contains either links to authoritative sources or cites authoritative sources, and I’m more than happy to provide links to any claims I’ve made that I haven’t cited.

    1. “So far you have dismissed the notion that anything other than surface temperatures matter, ”

      Quite nuts. I’ve cited repeatedly over the years the work of Roger Pielke Sr — accused of being a “denier” by the kind of alarmists you follow — who a decade ago said that global heat content (largely from the oceans) was the superior metric for understanding climate dynamics.

      Which is why it’s pointless to discuss matters with you. You just make stuff up and reply to it.

      As for the methane dangers, I suggest you see the IPCC’s most recent work: WGI of AR5, section 2.2.1.1.2 on Methane. It rates the risk as quite low. That’s the consensus opinion. As always in climate science, there are those that disagree with the consensus. Sometimes they’re right; usually they’re wrong.

    2. Tho,

      (1) “you accuse me of ‘making stuff up’ which is outrageously false as anyone who may be reading this thread can see, every one of my posts contains either links to authoritative sources or cites authoritative sources”

      Another reading FAIL (your comments are a series of FAILS). I was quite precise: as I have repeated pointed out, you make up things and attribute them to me — then give rebuttals.

      (2) As for methane, like most alarmists you don’t understand science. There are a wide range of opinions on many of the key questions about climate change. Such as methane. That’s why we have the IPCC to put them in context, so that people like yourselves don’t focus on a minority — and wet your pants in fear. See More good news about climate change: no sign yet of the methane apocalypse, and follow the links back to the IPCC. You’ll learn something.

      (3) “So far you have dismissed the notion that anything other than surface temperatures matter, ignored my points about…”

      Life is too short to debunk all your misinformation, especially since you ignore the evidence I provide — and respond with still more misinformation. You appear immune to science.

      These things are all SOP for climate activists. Ignoring rebuttals, misstating others’ views, each round responding with more misinformation, and ignoring the IPCC. In brief, discussions with you are a waste of time — like talking with a block of wood.

  8. Jesus Christ man, you are full of such venomous contempt. Can you at least give me one specific example of something you think I “made up”?

  9. Its a legitimate thing to be alarmed about. I don’t make stuff up. Prove it. Give me one specific example of something I “made up” and I’ll link you where I read it from, but if you can’t then you’re the one talking nonsense and ranting like a maniac. In the meantime you should read this and learn something yourself, son.
    http://www.theguardian.com/environment/earth-insight/2013/jul/31/artic-methane-catastrophe-empirical-evidence

  10. One more thing, Fabius. Your citation of Dr. Curry and the exclusion on this blog of any scientific research representative of so called “alarmist” perspectives really does speak volumes to your bias toward skeptics on the issue of climate change.

    Numerous surveys of expert opinion have affirmed near unanimous consensus (97%) that climate change is predominantly driven by human activity (Oreskes 2004; Doran and Zimmerman 2009; Anderegg 2010; cited by NASA here: http://climate.nasa.gov/scientific-consensus/ ). One content analysis of ALL published, peer reviewed scientific literature from November 2012 to December 31, 2013 found only 1 single author out of 9136 rejected the anthropogenic thesis: http://www.jamespowell.org/Second%20study/secondstudy.html

    Dr. Curry falls within a very, very small minority of professional scientists who doubt human causation. Dr. Curry also has affiliations with right-wing political think tanks and fossil fuel corporate interests: http://www.theguardian.com/environment/climate-consensus-97-per-cent/2014/sep/15/97-vs-3-how-much-global-warming-are-humans-causing

    If you were genuinely objective and open-minded about climate change, your posts on the issue would reflect a more accurate representation of views within the scientific community – including those who make the “alarmist” case such as Dr. James Hansen, Dr. Kevin Trenberth, Michael Mann, Jason Box, Michael Oppenheimer and many, many others. You are highly selective in the scientific literature you chose to discuss in your posts. Such selectivity – exclusive and unrepresentative of the range of expert views – is called “cherry picking”. People who cherry pick are ideologically driven to favour a certain perspective over competing, equally (if not more) valid views.

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