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The Critical Decade - Part 1: The Science

Posted on 28 May 2011 by dana1981

The Australian government established a Climate Commission which recently released a three chapter report entitled The Critical Decade.  The first chapter of the report, which we will examine in this post, summarizes the current state of climate science observational data.  But first, a statement in the introduction is worth quoting: 

"Over the past two or three years, the science of climate change has become a more widely contested issue in the public and political spheres. Climate science is now being debated outside of the normal discussion and debate that occurs within the peer-reviewed scientific literature in the normal course of research. It is being attacked in the media by many with no credentials in the field. The questioning of the Intergovernmental Panel on Climate Change (IPCC), the “climategate” incident based on hacked emails in the UK, and attempts to intimidate climate scientists have added to the confusion in the public about the veracity of climate science."

We at Skeptical Science have documented many such attacks on climate science by individuals with no climate credentials, who misrepresent scientific research, and attempt to sow doubt in the minds of the general public through non-scientific issues like Climategate.  But while these introductory comments are worth highlighting, let's move on to the scientific content.

The report is based on the IPCC Fourth Assessment Report (2007) as well as several other more recent studies.  Skeptical Science readers will already be familiar with much of the information in the first chapter, but it nevertheless provides a useful summary of recent climate research.  The main conclusions of Chapter 1 are as follows:

  • The average air temperature at the Earth’s surface continues on an upward trajectory at a rate of 0.17°C per decade over the past three decades.
  • The temperature of the upper 700 meters of the ocean continues to increase, with most of the excess heat generated by the growing energy imbalance at the Earth’s surface stored in this compartment of the system.
  • The alkalinity of the ocean is decreasing steadily as a result of acidification by anthropogenic CO2 emissions.
  • Recent observations confirm net loss of ice from the Greenland and West Antarctic ice sheets; the extent of Arctic sea ice cover continues on a long-term downward trend.  Most land-based glaciers and ice caps are in retreat.
  • Sea-level has risen at a higher rate over the past two decades, consistent with ocean warming and an increasing contribution from the large polar ice sheets.
  • The biosphere is responding in a consistent way to a warming Earth, with observed changes in gene pools, species ranges, timing of biological patterns and ecosystem dynamics.

The report notes that the past decade (2001-2010) was the hottest on record, 0.46°C above the 1961-1990 average.  It also contains many illuminating figures, including this one showing that Arctic sea ice is declining far faster than IPCC models projected, currently approximately 40 years ahead of schedule.

sea ice obs vs. IPCC models

The report also discusses that sea level rise is progressing at the very high end of the IPCC estimates, despite the efforts of certain "skeptics" to downplay the  sea level rise acceleration based on one exceptionally flawed paper

Chapter 1 proceeds to discuss the various signals of a changing Australian climate in the biosphere, including mammalian migrations to higher elevations, earlier arrival and later departure times of migratory birds, and the increase in bleaching events on the Great Barrier Reef (GBR).  There have been eight mass bleaching events on the GBR since 1979 with no known such events prior to that date.  The report goes on to discuss the potential causes of the observed climate change:

  • There is no credible evidence that changes in incoming solar radiation can be the cause of the current warming trend.
  • Neither multi-decadal or century-scale patterns of natural variability, such as the Medieval Warm Period, nor shorter term patterns of variability, such as ENSO (El Niño-Southern Oscillation) or the North Atlantic Oscillation, can explain the globally coherent warming trend observed since the middle of the 20th century.
  • There is a very large body of internally consistent observations, experiments, analyses, and physical theory that points to the increasing atmospheric concentration of greenhouse gases, with carbon dioxide (CO2) the most important, as the ultimate cause for the observed warming.
  • Improved understanding of the sensitivity of the climate system to the increasing atmospheric CO2 concentration has provided further evidence of its role in the current warming trend, and provided more confidence in projections of the level of future warming.

Again, this is not news to Skeptical Science readers, nor are the anthropogenic warming fingerprints the report discusses.  The ensuing discussion of climate sensitivity is fairly interesting, and harkens back to our examination of the cloud feedback:

"An analysis of the transition of the Earth from the last ice age to the Holocene, which infers climate sensitivity from the observed change in temperature and the corresponding changes in the factors that influence radiative forcing, also estimates a value of about 3°C (Hansen et al. 2008). Much of the uncertainty on the magnitude of climate sensitivity is associated with the direction and strength of cloud feedbacks. Recent observational evidence from short-term variations in clouds suggests that short-term cloud feedbacks are positive, reinforcing the warming, consistent with the current model-based estimates of cloud feedbacks (Clement et al. 2009; Dessler 2010).

A recent model study comparing the relative importance of various greenhouse gases for the climate estimates a sensitivity of approximately 4°C for a doubling of CO2 (Lacis et al. 2010). In addition, the study points to the importance of CO2 as the principal “control knob” governing Earth’s surface temperature."

It's worth noting that while Hansen et al. find paleoclimate evidence for a short-term climate sensitivity of 3°C for doubled atmospheric CO2, they also find that when including slow-acting feedbacks, the long-term sensitivity is closer to 6°C.  Next up is a discussion of how the carbon cycle is changing:

  • Despite the dip in human emissions of greenhouse gases in 2009 due to the Global Financial Crisis, emissions continue on a strong upward trend, on average tracking near the top of the family of IPCC emission scenarios.
  • Ocean and land carbon sinks, which together take up more than half of the human emissions of CO2, appear to be holding their proportional strengths compared to emissions, although some recent evidence questions this conclusion and suggests a loss of efficiency in these natural sinks over the past 60 years.
  • If global average temperature rises significantly above 2°C (relative to pre-industrial), there is an increasing risk of large emissions from the terrestrial biosphere, the most likely source being methane stored in permafrost in the northern high latitudes.

There is evidence that the efficiency of natural carbon sinks is declining, particularly in the Southern Ocean, but this possibility remains highly uncertain and controversial.  Thus far natural carbon sinks have kept pace with us, absorbing approximately 57% of human emissions since 1958, but there is of course a limit to their storage capacity.

carbon budget

As the planet continues to warm, approaching the 2°C danger limit, not only is there an increasing risk that these natural carbon sinks will become saturated, but potentially significant releases from other carbon sources (methane beneath permafrost, methane hydrates stored under the sea floor, organic material stored in tropical peat bogs, etc.) becomes increasingly likely.

The final section in Chapter 1 discusses the certainty of our knowledge of climate change:

  • The IPCC’s Fourth Assessment Report has been intensively and exhaustively scrutinised and is virtually error-free.
  • The Earth is warming on a multi-decadal to century timescale, and at a very fast rate by geological standards. There is no doubt about this statement.
  • Human emissions of greenhouse gases – and CO2 is the most important of these gases – is the primary factor triggering observed climate change since at least the mid 20th century. The IPCC AR4 (2007a) report attached 90% certainty to that statement; research over the past few years has strengthened our confidence in this statement even more.
  • Many uncertainties surround projections of the particular risks that climate change poses for human societies and natural and managed ecosystems, especially at smaller spatial scales.  However, our current level of understanding provides some useful insights: (i) some social, economic and environmental impacts are already observable from the current level of climate change; (ii) the number and magnitude of climate risks will rise as the climate warms further.

The report notes that some significant uncertainties remain, such as the exact responses of the Greenland and Antarctic ice sheets, and the hydrological cycle, to the continuing warming of the planet.  But the report also hammers home a key point that we wish "skeptics" would take to heart:

"These uncertainties, however, in no way diminish our confidence in the observation that the Earth is warming and in our assessment that human emissions of greenhouse gases are the primary reason for this warming."

"Despite these seemingly daunting uncertainties, a number of social, economic and environmental impacts can be observed that are consistent with what is anticipated from the current level of climate change. The number and magnitude of climate-related risks will rise considerably as the climate warms towards 2°C above the preindustrial level; and above the 2°C guardrail, the risks may rise dramatically"

In short, despite the uncertainties, the scientific evidence is clear on the main points that humans are causing dangerous global warming.  It's also important to note that uncertainties can go either way, and the consequences of climate change are just as likely to be more damaging than we expect as less.   Uncertainty is not our friend.

In Parts 2 and 3 we will examine the report's chapters on risks associated with climate change and implications of the science for emissions reductions.

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Comments 101 to 116 out of 116:

  1. Ken @99, So you too endorse quote mining, cherry-picking and misrepresenting scientists' findings and position on certain issues then? As I and others have demonstrated that is what a certain poster has been doing. And now you seem to be endorsing that behavior... Tamino perfectly described what Camburn, and now you it seems, are up to. Camburn states that according to ARGO data global SSTs are "presently static". Presently? Framing the argument that way is disingenuous, we all know that cherry-picking short-term, statistically insignificant windows is meaningless. You seem to be claiming that to do so is a valid and reasonable point? Camburn ignoring the data presented to him here by me and others is reasonable? Him uncritically accepting Houston and Dean's troubled paper is reasonable? You guys are desperately trying to advance a very weak counter argument here, and it is showing. Now good night.
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  2. Albatross: When I am discussing an issue I prefer not to ruffle feathers, so I shall not post to this thread in the future. I have pointed out that sea level rise has slowed. Why does that upset you so much? I have pointed out that according to ARGO data, 0-700M OHC is static since 2003. When you go to and plot hadcrut ocean anomlies from 2005 thru 2011, the trend is also flat. These are observations that are recent. To me they indicate a change in trend as three very large metrics concerning heat show a flat trajectory. You also seem to have a problem with Houston and Dean's paper. Tell me what the problem is with it please. It is actually a quit wide ranging paper, talks, with references, about the current problems in determining the rate of SLR. I wish you well. The counter arguement, if you think it is an arguement, is not weak, as it is supported by empirical data and the link you so graciously provided that I quoted, in ref to the data that is currently present.
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    [DB] "I have pointed out that sea level rise has slowed.  Why does that upset you so much?

    I have pointed out that according to ARGO data, 0-700M OHC is static since 2003.

    When you go to and plot hadcrut ocean anomlies from 2005 thru 2011, the trend is also flat."

    Several problems here, chief of which is the focus on statistically insignificant timescales (which is also called cherry-picking).  This issue has been pointed out to you in the past.  For a recent discussion of the issues with that practice, see here and here.  Also, 0-700m is not the whole ocean.  Various other studies show heat being transported deeper than that.

    Sea Level Rise:




    "You also seem to have a problem with Houston and Dean's paper."

    Many others do as well.  Commentary by Church and White begins here.  Longer analysis found here (which you were given previously).

  3. Moderators, Please snip all text written by on this thread me that has violated the house rules. I do not want any claims of favoritism being made, nor do I expect any favoritism. The body of science stands on its own anyways. The cherry-picking of statistically meaningless and insignificant windows continues @102..... Please also delete this message if you wish.
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    [DB] The issues in play have been discussed and dealt with.

  4. DB at #99. KL: "Camburn has made several valid and reasonable points" DB: Which fail to stand up to scientific rigor and scrutiny. Well DB how about answering my #96, which goes back to your chart post at #58 and the issue of the validity or not of UCAR SLR chart. I see no scientific rigor in your posting conflicting chart evidence and then not explaining which is correct.
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  5. Ken First, you do not deny that Camburn misrepresented Hansen. Good, but then you go and say this: "It Camburn and I are cherry picking on short timescales - then we seem to be in the company of Jim Hansen." Not true-- and your accusation of cherry picking against Hansen is ridiculous and unfounded, or are you simply musing about scientific misconduct by one of the world's leading climate scientists? Hansen, as always, looks at the big picture and context, even when he might be looking at shorter periods of time to solve a problem (i.e., it is not cherry picking to look at ENSO, but don't try and use ENSO to claim that the the long-term warming in global SATs is because of ENSO like contrarians McLean et al. infamously tried to do). Also, as I explained above to your friend @97 above, and which fell on deaf ears, "Tamino has shown otherwise, but regardless Hansen and Sato are wisely most definitely are not using noise in the data record as a reason to claim that we are not facing a whole lot of trouble down the road if we continue along those path. So you have misrepresented Hansen's position." To do so, focus on the noise and then make grandiose claims about the big picture, would be foolhardy. This game of focussing on the noise in the climate system to claim that 'warming has stopped or slowed so there is nothing to worry about', or that the 'theory of AGW has been overturned' etc, is very old, and I for one am sick of "skeptics" playing that game. We can be playing that game circa 2100-- "Ooh global SATs slowed somewhat the last 5 years", meanwhile the planet will have warmed significantly between now and then. "The UCAR SLR chart which you seem loathe to discuss and is often quoted in these threads, covers the period 1993-2010 - all of 18 years inclusively." A strawman, and not true. I posted an image of the satellite altimeter data above @52. Now I do not know if advancing strawmen and demonstrably false statements is a valid form of debating...oh wait it is, it is called baiting and gish gallop, and techniques which are used liberally by self proclaimed 'skeptics' and deniers of AGW. The Australian Climate Commission's report was right on the mark. How inconvenient for the 'skeptics', yet more evidence that runs counter their ideas. No wonder they are scrambling to obfuscate and fabricate debate.
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  6. Albatross: Show me ONE statement that I made that is false. I had said that I wouldn't comment. On this one, I will. Once again, show me ONE statement that I made that is false.....and I want you to BACK up why it is false. As someone who proclaims to understand scientific queries, you must also stay within the parameters of my statements. Thank you.
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  7. I know I'm not Albatross, but I can see at least ONE statement that is clearly, false, Camburn... Camburn #102: " ... I shall not post to this thread in the future." Surely you don't need me to back up why it's false :)
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  8. Skywatcher: I was accused of false statements. I do not take that accusation lightly and felt a response was in order.
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  9. Moderator, I did not accuse Camburn of making a false the thread, so he is arguing a strawman. In my message to Ken I noted that it was demonstrably false of Ken Lambert to accuse Hansen of cherry picking, and also for him to say that we are avoiding discussion of the satellite altimeter data. Read my post @105.
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  10. Albatross #105 Readers can judge for themselves when the my post being answered by Albatross at #105 has been deleted by Moderators without even a (snip). Hansen's latest synopsis explicitly draws conclusions about the reduction in warming imbalance from the OHC record for the period 2005-10 - 6 years. Yet I am criticised as a 'cherry picker' by drawing conclusions from the UCAR chart for the Jason 1 & 2 records over a 9 year period. This is then turned by Albatross into; "Not true-- and your accusation of cherry picking against Hansen is ridiculous and unfounded, or are you simply musing about scientific misconduct by one of the world's leading climate scientists?" I did not accuse Hansen of cherry picking. I said explicitly that if the likes of Albatross and DB want to label analysis and conclusions of short term records (in Hansen's case, 6 years) as 'cherry picking' then we are in the good company of Jim Hansen.
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  11. DB #102 Could you explain the origin of the charts you posted in the 'green box' at #102.
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  12. Ken Lambert - The charts DB posted came from one of the links he provided, to Tamino's "5 Years" post. These are (to minimize arguments about data manipulation, and to remove high frequency noise) simple 5-year non-overlapping box averages, with <5 year periods being represented by the remaining data available (hence less smoothed). It's a nice illustration of what the long term trends are, with the short term noise averaged out. And it's an especially good antidote to some of the cherry-picking that goes on, for example, at WUWT, where they tend to select tiny periods to find short term down-slopes, and from that claim SLR is negative.
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  13. KR: The problem, of course, is that Tamino is a professional statistician who specialized in time series analysis, which proves he's a commie-pinko dictatorship-minded freak, because everyone knows that casinos lose tons of money at the slots despite these do-gooder commie stats types trying to educate the public that the house is rigged ... The trolls here, of course, know better ...
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  14. dhogaza - I'll refer you to an illustration that I've pointed out to folks claiming the radiative greenhouse effect violates thermodynamics. Cartoon - warning, mature language
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  15. DB & Camburn #102 I referred to this UCAR Chart of GMSL (Global Mean Sea Level) in this thread: DB has posted Tamino's Charts at #102, and cast doubt on the UCAR Charts as somehow uncorrected for GIA and other effects; viz: Response: "[DB] SLR plots from UCAR/NCAR need to have the corrections applied to them to account for regional isostatic rebound effects and seasonal effects to be properly filtered out. If using the unadjusted/improperly adjusted data, one risks writing posts on CO2 snow..." This is what UCAR say on their website: "Prior to release 2011_rel1, we did not account for GIA in estimates of the global mean sea level rate, but this correction is now scientifically well-understood and is applied to GMSL estimates by nearly all research groups around the world. Including the GIA correction has the effect of increasing previous estimates of the global mean sea level rate by 0.3 mm/yr." AND "The GMSL rate corrected for GIA represents changes in water mass and density in the oceans. These changes are thought to be predominantly driven by thermal expansion of the oceans and land ice melt (Greenland and Antarctic ice sheets and glaciers)." Now go back and look at the UCAR Chart. It captions 'Inverse Barometer applied and GIA corrected" AND "seasonal signals removed". DB - what further corrections would be needed to the UCAR Charts to make them acceptable to you, and why would Tamino's charts be superior measures of global mean sea level?
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    [DB] "DB has posted Tamino's Charts at #102, and cast doubt on the UCAR Charts as somehow uncorrected for GIA and other effects"

    The only doubt implied here is by you in order to manufacture controversy.  The graphic I used clearly shows GIA already applied, like I said that they needed to have incorporated into them.

    "DB - what further corrections would be needed to the UCAR Charts to make them acceptable to you, and why would Tamino's charts be superior measures of global mean sea level?"

    Again the attempt to manufacture controversy and sow the seeds of doubt.  Tamino's charts and graphics succinctly illustrate a different analysis of the data which is mutually complementary to that provided by UCAR.  To say that they are not, which you are doing here, is dissembling.

    My recommendation would be to simply ask, without invective or snark, for clarification about things you don;t understand.  For you either don't understand them or you are actively choosing to misunderstand or to misrepresent what was said.  If the latter is the case, than the course of action you are prosecuting can be aptly called "moderator trolling".

    If the former, then ask.  Politely.

    If the latter, then desist.  Or you will have to find a different venue to ply your case.

  16. DB Then I will ask you politely. What is the meaning of this statement which you captioned above an already 'corrected' chart? "[DB] SLR plots from UCAR/NCAR need to have the corrections applied to them to account for regional isostatic rebound effects and seasonal effects to be properly filtered out. If using the unadjusted/improperly adjusted data, one risks writing posts on CO2 snow..."
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    [DB] I was attempting to answer a question about GIA and why, as a local and regional effect rather than a global effect, it needs to be accounted for and incorporated into the UCAR graphics.  Like the one shown/linked to.  Thank you for relaying the UCAR methodology on that for further clarity.

    If my verbiage was less-than-clear on that point, I apologize.  The goal is to be clear, but [I] occasionally fall short in that endeavor.

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