The timing couldn’t be worse.
On 23-26 September, scores of representatives of the world’s Environment Ministries are scheduled to meet in Stockholm to wordsmith the final draft of the Summary for Policymakers (SPM) of the key WG1 (physical science) portion of the Fifth Assessment Report (AR5) of the UN’s Intergovernmental Panel on Climate Change (IPPC).
The draft SPM, sent to governments on 2 August, is a 22-page condensation of 14 chapters comprising 1,914 pages of material discussing scientific papers that were published between 2006 and 15 March 2013.
This SPM is (or could be) a document of world-shaking importance. As Bloomberg points out – “it is designed to be used by ministers working to devise by 2015 a global treaty to curb climate change”.
The timetable for the global treaty was deferred at the Durban COP because developing countries (particularly China and India) felt that the 2013 SPM was an indispensable input to the negotiations. Governments need an authoritative up-to-date assessment of both the extent and the causes of the climate change threat, present and future.
But the SPM has been sidelined by momentous climate change events that occurred after its March cut-off date – and even after the date the draft was circulated.
The “extent of warming” issue turns on how sensitive the planet is to increasing CO2 concentrations. Equilibrium climate sensitivity (ECS) was crudely estimated by Charney in 1979 at 3.0 ±1.5°C and that range remained more-or-less constant through all four previous IPCC reports.
During 2012, several groups of researchers noted that recent data and modern diagnostics now showed that the 30-year old 3°C mid-point had been grossly over-stated. Peer-reviewed journal papers included:
• Ring et al: estimates of climate sensitivity ranged from 1.5 to 2.0°C.
• Van Hateren: millennium-scale sensitivity found to be 2.0 ±0.3°C.
• Aldrin et al: the 90% credible interval ranges from 1.2°C to 3.5°C, with a mean of 2°C
This, of course, led to great dissension and became the major challenge faced by the lead authors of WG1. Although we don’t yet know how they finally reacted, a leaked copy of the SPM draft suggests that they mainly held to the longstanding orthodoxy.
In January 2013, the British media reported that the UK Met Office was projecting a 20-year standstill in global warming by 2017. This ‘pause’ had not been predicted by climate models. In February, IPCC chairman Pachauri admitted that the temperature data had already been flat for 17 years, while opining that a standstill of 30 years would be required to rebut the previous consensus.
Both “cause” and “extent” issues are heavily dependent on the validity of climate simulations by the contemporary Coupled Model Intercomparison Project (CMIP5), as are all IPCC projections of future planetary temperatures and their impacts. Serious scientific doubts about either ECS-related inputs or the accuracy of temperature outputs would be fatal to the credibility of the AR5.
After the March cut-off date for WG1 papers, the following 2013 papers have strongly reinforced concerns regarding the exaggeration of climate sensitivity:
• Otto et al: the best estimate of sensitivity is 30% below the CMIP5 multimodel mean.
• Forster et al: analysis of CMIP5 shows that 2/3 are above the Otto ‘likely’ range.
• Masters: median estimate of ECS is 1.98°C.
• Lewis: improved methodology shows the mode and median to be 1.6K
In congressional testimony, Judith Curry cited the Hawkins graph depicting observed trends below 90% of CMIP5 projections, and notes that warming may not resume until mid-century. James Hansen attributes the ‘hiatus’ to a combination of natural variability and lower sensitivity but predicts “temperature will rise significantly in the next few years with the nex El Nino phase.”
The temperature standstill has been apparent in the data for many years, but the tribalism of climate science rendered it unmentionable until the public disclosures of early 2013. Once spoken, it demanded an explanation – and it then became clear there was a great dearth of research on the subject. By the time researchers were ready to fill this gap, the draft SPM had already been dispatched.
During August 2013, a flood of highly influential papers have appeared:
• von Storch & Zorita found that observed temperatures 1998-2012 were not consistent with 23 tested CMIP3 and CMIP5 models, even at the 2% confidence level. The inconsistency increases rapidly with trend length and a 20-year trend (ie to 2017) would lie outside the ensemble of all model-simulated trends.
• von Storch & Zorita (the same paper) concludes that ‘natural’ internal variability and/or external forcing has probably offset the anthropogenic warming during the standstill. Overestimated sensitivity may also have contributed.
• Tung & Zhou reported that the “underlying net anthropogenic warming rate has been steady since 1910 at 0.07-0.08°C/decade, with superimposed AMO-related ups and downs ..”. The sharply increased CO2 concentrations of recent decades has not caused warming to accelerate, as was predicted by the models.
• Yu Kosaka & Shang-Ping Zie plausibly found that climate models have vastly under-estimated natural variation. La-Nina-like cooling in the Eastern Pacific throughout the 21st century (since the PDO turned negative) has conquered the projected greenhouse warming. The 0.68°C warming trend during 1975-98 (when the PDO was positive) would have been 0.4°C natural and only 0.28°C anthropogenic.
• Katz et al says the critical uncertainty measures used by the IPCC are “out of date by well over a decade”. Modern statistical techniques could improve assessments “dramatically”.
• Fyfe Gillett & Zwiers focused on the extraordinary gap between the temperature simulations of 37 CIMP5 models and the observed outcomes. Due to a ‘combination of errors’, the models have overestimated warming by 100% over the past 20 years and by 400% over the past 15 years.
Come the revolution…
These new papers devastate the IPCC orthodoxy that current and future global temperatures are mostly driven by greenhouse gas emissions, and will reach dangerous levels later this century. On the other hand, all older papers are blindsided by their apparent failure to take account of the recent data (standstill).
The IPCC’s 2001 report cautioned: In climate research and modelling, we should recognise that we are dealing with a coupled non-linear chaotic system, and therefore that the long-term prediction of future climate states is not possible. The most we can expect to achieve is the prediction of the probability distribution of the system’s future possible states by the generation of ensembles of model solutions. This reduces climate change to the discernment of significant differences in the statistics of such ensembles.
The “dangerous anthropogenic global warming” (DAGW) hypothesis is based on a clear difference between CMIP5 runs with natural plus anthropogenic forcing, versus natural variability only. That difference now disappears when ensembles are adjusted to reflect current empirical data. It is quite conceivable that natural variabilty (including natural forcing) has historically dwarfed anthropogenic effects and will persistently do so in future.
In his seminal 1962 work, The Structure of Scientific Revolutions, Thomas Kuhn persuasively argued that science does not progress through the linear accumulation of knowledge but undergoes periodic revolutions or ‘paradigm shifts’.
In Kuhn’s view, no evidence that is incompatible with the current paradigm will be entertained during long periods of normal science. However, as anomalous results build up, science eventually reaches a crisis which drives the necessary acceptance of a new paradigm, which subsumes both the old and new results into a new framework. Kuhn calls this transformative point, revolutionary science.
2013 is ushering in a long-delayed revolution in climate science. A new paradigm is demanded which recognizes that AGW is but one non-determinative component in a ‘non-linear chaotic system’.
Dealing to the paradigm shift
All of this leaves the IPCC in a terrible bind regarding its September meeting. Should it:
• rubber-stamp a SPM that has been overtaken by events?
• add a major caveat to the state of play in March 2013, promising an addendum will be issued to cover post-cut-off papers? or
• adjourn the meeting to accomodate a crash program to re-write both the WG1 Technical Report and the consequent SPM?
The business as usual course is the worst option. With tense international negotiations riding on this document, it is far better that it be delayed than wrong – or indefensible. No government can make far-reaching policy decisions on the basis of a report which is widely believed to be obsolete before it is released.
An interim report suffers from a similar credibility deficit. Already, Environment departments from the USA and the European Union have formally sought more clarity on the “warming hiatus” and have asked the IPCC to include full information in the SPM.
“The recent slowing of the temperature trend is currently a key issue, yet it has not been adequately addressed in the SPM,” said the EU.
Although the draft says the trend has tapered off, the implications are unclear – causing the US to comment “a bunch of numbers are [left] up in the air without a concrete conclusion.”
Several countries, including China, seek information on the heat uptake of the oceans or other natural variances which might have depressed climate change data.
The draft SPM apparently fails to mention that 30-year warming trends have declined each year since peaking in 2003. Or that the latest 10-year period (2003-12) is the coolest decade since satellite records began in 1979.
WG1 has a track record of ignoring inconvenient research on grounds that it is ‘isolated’ or published in obscure journals. That can hardly be the fate of the August papers. All but one have been accepted by Nature Climate Change. Several of the authors are active contributors to IPCC reports, with Zwiers a current vice-chairman of WG1 and Fyfe a review editor.
Revolutionary climate science is under way. The question now is whether the IPCC is up to the challenge.
 18.104.22.168 WG1 TAR IPCC