Monday, September 12, 2016

Homogenisation of temperature and precipitation time series with ACMANT3: method description and efficiency tests


Paper featuring John Coll of ICARUS. Post written by John Coll
International Journal of Climatology July 2016 doi: 10.1002/joc.4822
Time series homogenisation and the multiple breaks problem
During the long period of climatic observations, station location, instrumentation and several other conditions of the observation may change, resulting in non-climatic temporal variation in the observed data.  Such non-climatic changes “inhomogeneities” affect the usability of observed data to the detection of climate change and climate variability.  One important present task of climate science is to provide accurate regional and global mean temperature trend estimates (Rohde et al., 2013; Rennie et al., 2014; Venema et al., 2015), and homogenisation significantly contributes to that. The most frequent way of time series homogenisation is the use of statistical procedures.  The direct aim is to identify and correct statistically significant shifts in the section means (they are the estimated timings of technical changes, often referred as breaks or change points).  To separate the inhomogeneities from the true climatic variation (the latter never should be removed from the data), homogeneity tests are usually applied to the differences between a candidate series and other series of the same climatic area (“relative homogenisation”), rather than directly to the candidate series (“absolute homogenisation”).

We have the general experience that climatic time series contain about 5 breaks per 100 years on average (Venema et al. 2012).  Although statistical homogenisation has a century long history, the theory and development of multiple break homogenisation offering mathematically higher level solutions appeared only in the 1990s coincident with the more widespread use of personal computers.  One early representative of multiple break methods was PRODIGE (Caussinus and Mestre 2004).

During the European project COST ES0601 (known as ‘HOME’, 2007–2011)  two new multiple break methods were created based on PRODIGE: one is the fully automatic ACMANT (Adapted Caussinus–Mestre Algorithm for homogenising Networks of Temperature series, Domonkos, 2011) and the other is Homogenisation software in R (HOMER, Mestre et al., 2013), the interactive homogenisation method officially recommended by HOME.  Both HOMER and ACMANT include the optimal step function fitting with dynamic programming for break detection and the network wide minimization of residual variance  for correcting inhomogeneities (ANOVA, Caussinus and Mestre, 2004; Domonkos, 2015).  Both HOMER and ACMANT provide additional functionality relative to the parent method PRODIGE, and they are assumed to be the most efficient homogenization methods nowadays.

ACMANT3 development and discussion

This paper describes the theoretical background of ACMANT and the recent developments, which extend the capabilities, and hence, the application of the method.  The most important novelties in ACMANT3 are: the ensemble pre-homogenisation with the exclusion of one potential reference composite in each ensemble member; the use of ordinary kriging for weighting reference composites; the assessment of seasonal cycle of temperature biases in case of irregular-shaped seasonal cycles. ACMANT3 also allows for homogenisation on the daily scale including for break timing assessment, gap filling and analysis of ANOVA application on the daily time scale.

ACMANT3 is a complex software package incorporating six programmes, these are: temperature homogenisation with a sinusoid annual cycle of biases; temperature homogenisation with an irregular annual cycle of biases; precipitation homogenisation.  Each of the preceding three has monthly and daily homogenisation versions (http://www.c3.urv.cat/data.html); and in total the six programmes incorporate 174 sub-routines.  The software package also includes auxiliary files to support network construction. However, despite its complicated structure, ACMANT provides the fastest method implementation among all the available automatic homogenisation methods.

Considering the similarities of the theoretical background of HOMER and ACMANT, the choice between HOMER and ACMANT for particular homogenisation tasks should be based on the dataset characteristics.  The use of ACMANT is particularly recommended for (1) datasets with little or no metadata; (2) datasets from dense networks with large numbers of time series and where there are high spatial correlations; (3) very large datasets (>200 time series) for which the use of automatic methods is the most feasible and easily managed solution.   

Figure 1: Errors of raw data and residual errors of ACMANT homogenised data in a test dataset of simulated air surface temperatures. AC1, AC2, AC3 mean the first, second and third generation of ACMANT. Upper left: root mean squared error (RMSE) of monthly values, upper right: RMSE of annual values, bottom left: trend bias for individual series, bottom right: network mean trend bias. Smean means systematic trend bias. 

The efficiency tests presented in this paper provide firm indications that ACMANT3 can considerably reduce initial regional trend biases at any spatial scale, although the efficiency achieved depends both on the spatial density and the extent of the intact record of the observational data.  Further research is needed in this important and emerging area, for both the development and testing of statistical methods (Domonkos and Guijarro, 2015) and alongside an analysis of the causes of possible systematic biases in temperature records, with parallel measurements (http://www.surface
temperatures.org/databank/parallel_measurements).

The authors also have another ongoing collaboration as part of the Irish Environmental Protection Agency funded “HOMERUN” project (e.g. Coll et al., 2015a,b) which aims to homogenise the large and dense Irish precipitation dataset with ACMANT and HOMER and explore more details about the practical application of these methods.  More details are available from

The ACMANT3 software package together with its manual is freely accessible from http://www.c3.urv.cat/ data.html.


References
Caussinus H, Mestre O. 2004. Detection and correction of artificial shifts in climate series. J. R. Stat. Soc. C 53: 405–425, doi: 10.1111/j.1467-9876.2004.05155.x.
Coll J, Curley C, Domonkos P, Aguilar, E, Walsh S, Sweeney J, 2015a.  An application of HOMER and ACMANT for homogenising monthly precipitation records in Ireland.  Geophysical Research Abstracts 17: EGU2015-15502.
Coll J,  Domonkos P, Curley, M, Aguilar E, Walsh S, Sweeney J, 2015b.  IENet: A homogenised precipitation network for Ireland – preliminary results.  10th EUMETNET Data Management Workshop. St Gallen, Switzerland.
Domonkos P. 2011. Adapted Caussinus-Mestre Algorithm for Networks of Temperature series (ACMANT). Int. J. Geosci. 2: 293–309, doi: 10.4236/ijg.2011.23032.
Domonkos P. 2015 Homogenization of precipitation time series with ACMANT. Theor. Appl. Climatol. 122: 303–314, doi: 10.1007/s00704-014-1298-5.
Domonkos P, Guijarro JA. 2015. Efficiency tests for automatic homogenization methods of monthly temperature and precipitation series. 10th EUMETNET Data Management Workshop Oct 28-30, St. Gallen, Switzerland.
Mestre O, Domonkos P,  Picard F,  Auer I, Robin S, Lebarbier E, Böhm R, Aguilar E,  Guijarro J, Vertacnik G,  Klancar M, Dubuisson B, Štepánek P. 2013. HOMER: homogenization software in R – methods and applications. Idojaras Q. J. Hung. Meteorol. Serv. 117: 47–67.
Rennie JJ, Lawrimore JH, Gleason BE, Thorne PW and others. 2014. The international surface temperature initiative global land surface databank: monthly temperature data release description and methods. Geosci. Data J. 1/2: 75–102, doi: 10.1002/gdj3.8.
Rohde R, Muller R, Jacobsen R, Perlmutter S, Rosenfeld A, Wurtele J, Curry J, Wickham C, Mosher S. 2013. Berkeley Earth temperature averaging process. Geoinform. Geostat. 1: 2, doi: 10.4172/gigs.1000103.
Venema V, Jones P, Lindau R, Osborn T. 2015. Is the global mean land surface temperature trend too low? 15th Annual Meeting of the European Meteorological Society Sofia (Bulgaria), EMS2015-557.
Venema V, Mestre, O, Aguilar E, Auer I, Guijarro JA, Domonkos P, Vertacnik G, Szentimrey T, Stepanek P, Zahradnicek P, Viarre J, Müller-Westermeier G, Lakatos M, Williams CN, Menne M, Lindau R, Rasol D, Rustemeier E, Kolokytha, K, Marinova T, Andresen L, Acquaotta F, Fratianni S, Cheval  S, Klancar M, Brunetti M, Gruber C, Duran MP, Likso T, Esteban P and Brandsma T. 2012: Benchmarking monthly homogenization algorithms. Climate of the Past, 8, 89-115, doi:10.5194/cp-8-89-2012.

Thursday, September 1, 2016

New paper by John Coll et al.: Projected climate change impacts on upland heaths in Ireland


Projected climate change impacts on upland heaths in Ireland
Climate Research July 2016 doi: 10.3354/cr01408


Ireland has a high proportion of the northern Atlantic wet and alpine and boreal heaths of high conservation value within Europe.  These upland habitats of and their associated oceanic species and vegetation are of high conservation value, but are also considered vulnerable to climate change.  For example, is anticipated that an amplification of the elevation-dependant warming already detected will accelerate the rate of change in mountain ecosystems, with the potential to exacerbate both the pace and the amplitude of extinctions of vulnerable upland species uniquely adapted to these habitats.

However, projections from different climate models vary markedly and local processes for upland regions are poorly captured, hence more localised modelling studies are required to inform management decisions.  Various modelling approaches have been used to convert species distributions into predictive maps, and bioclimatic envelope models (BEMs) are widely used.   However, confidence in the predictive power of BEMs is compromised by conceptual, biotic and algorithm flaws. Arising from this, the use of consensus methods is popular on the basis that they decrease the predictive uncertainty of single-models to give a probability distribution per pixel as opposed to a single value. 

The use of BEMs for habitats is novel, and only a limited number of studies have applied these methods to landforms and habitats. In this work seven bioclimatic envelope modelling techniques implemented in the BIOMOD modelling framework were used to model Wet and Alpine and Boreal heath distributions in Ireland.  An ensemble prediction from all the models was used to project changes based on a climate change scenario for 2031 to 2060 dynamically downscaled from the Hadley Centre HadCM3-Q16 global climate model. The climate change projections for the individual models change markedly from the consistent baseline predictions.  Projected climate space losses (gains) from the BIOMOD consensus model are -40.84% (limited expansion) and -10.38% (full expansion) for Wet heath (Figure 1a); and -18.31% (limited expansion) and +28.17% (full expansion) for Alpine and Boreal heath (Figure 1b).


Fig. 1. Mapped BIOMOD consensus model outputs for (a) wet heath and (b) alpine and boreal heath habitats based on median probability ensemble forecasting method values using the true skill statistic threshold. Red squares denote projected losses of climate space for the A1B 2031−2060 scenario relative to the baseline; blue squares denote stable climate space grids (areas of suitable climate under a no dispersal—no habitat expansion—scenario); green squares denote potential climate space gains relative to the baseline; blue and green squares combined indicate areas of suitable climate under a full dispersal (habitat expansion) scenario.

The projected decline and fragmentation of the climate space associated with heath habitats would
have significant implications for the ecology of these complex upland ecosystems and their associated species.  Results indicate that the distribution of wet heath habitats in Ireland is regionally sensitive to climate change, most notably for lower-lying areas in the south and west of the country. Increasing temperature and precipitation changes may reduce and fragment the area that is suitable for heath development.  Degrading heaths will also have an impact on the wider structure and function of the uplands as the overall mosaic of habitat types respond to climate change. For example, drier and warmer summers may increase the frequency, size and severity of uncontrolled fires, and drought effects may become more common later in the year. This may have severe impacts in areas already subject to pressures such as overgrazing, inappropriate burning, and loss of vegetation cover combined with erosion of the peat or soil.

Some attempt has been made to deal with uncertainty, at least in relation to differing results between the model categories, by providing the results from the individual BEMs implemented in the BIOMOD framework alongside the ensemble projection. Certainly, there is substantial variation in the results between the individual BEM types when the A1B scenario data are projected through the models.  Although only the downscaled output from 1 GCM and scenario has been used to project climate space changes, the methods lend themselves to using different GCM and RCM outputs from a range of scenarios to better encapsulate uncertainty. Thus e.g., given the importance of mean winter precipitation in all the BEM model families, if a wetter or dryer model or scenario had been used from the ENSEMBLES RCMs, the results projected via the BEMs could have varied further. 

Such an expanded framework would allow the identification of adaptation strategies that are robust (i.e. insensitive) to climate change uncertainties, and would allow more confidence in identifying and targeting vulnerable areas of heath habitat for priority conservation management measures.  These sort of refinements would also help inform best practice conservation management, whereby limited resources could be directed to areas coincident with healthy and functional heath communities and projected future climate suitability.

Wednesday, June 15, 2016

Open Session 9-10am June 20th to open the 9th ACRE conference

ICARUS and Maynooth University shall be hosting the 9th Meeting of the Atmospheric Circulation Reconstructions over the Earth project next week (20th-24th June). The opening session will be open to the public and media and be held in Renehan Hall on the South Campus from 9 to 10am.

The Session shall be chaired by Dr. Kate Willett of the UK Met Office who has created numerous datasets and edited for the past several years the annual State of the Climate Series in the Bullettin of the American Meteorological Society.

Seamus Walsh the Head of Climatology and Observations Division at Met Eireann shall welcome attendees to Ireland and provide a high level overview of the importance of data rescue and analysis to their mission.

Dr. Philip Brohan of the UK Met Office and Dr. Gil Compo of the Cooperative Institute for Environmental Sciences shall provide a talk on data rescue using citizen science and its application to historical renalayses products.

Finally, Dr. Conor Murphy of ICARUS shall provide an overview of several recent pieces of research on long-term changes in Irish climate including, droughts, floods, storminess and temperature.

All are welcome to attend and seating is on a first come first served basis. Renehan Hall is a ten minute walk from both the bus stop and the train station. For those driving onto campus the parking restrictions are lifted presently.

Details on the remainder of the program can be made available on request and a small number of seats may be available for some sessions.

Wednesday, May 25, 2016

Re-examining changes in Diurnal Temperature Ranges

This is a repost for the International Surface Temperature Initiative blog

A recently published pair of papers in JGR ($, sorry) reassessing changes in observed Diurnal Temperature Range changes has been recently highlighted in EOS and Nature Climate Change.

The analyses have been extremely long in the making. They started out back in 2010 as 'hobby' papers and never got explicit funding so trundled along very very slowly indeed. The release of the ISTI databank provided an opportunity to create a new estimate of DTR changes and compare it to several pre-existing estimates.

The first paper details the construction of the new dataset of DTR changes. This takes the version 1 release of the ISTI databank and applies the pairwise homogenisation algorithm (PHA) used by NOAA NCEI to these holdings. The paper deals with the homogenisation processing, analyses the resulting dataset estimates and discusses aspects of the underlying metrology (not a typo). Below are the gridded trends over 1951-2012 and the global timeseries. The 'raw' data is the basic data held in the databank. Directly adjusted is where the DTR series were presented to the PHA algorithm. Indirectly adjusted is where, instead, the adjustments to Tmin and Tmax are used.


We found that more breaks are returned for DTR than is the case for Tmax or Tmin, for which more breaks are returned again than Tmean. This has potential implications for future homogenisation strategies in that searching for breaks in Tmean appears sub-optimal. Potential reasons for this were detailed in a prior ISTI blogpost and are further elucidated upon in the paper itself.

The second paper takes the new analysis and compares it to several pre-existing analysis and then attempts to reformulate the findings on DTR from the IPCC Fifth Assessment Report (which assessed only medium confidence). The new analyses provide considerable confidence in a finding that DTR has decreased globally since the mid-twentieth Century, with most of that decrease occuring prior to 1980. Data are too sparse and uncertain to make meaningful conclusions about DTR changes prior to the mid-twentieth Century, at least globally. The compared datasets show very distinct coverage and somewhat divergent trends since the mid-twentieth Century:

Much of the divergence between estimates results from the disparate approaches taken to accounting for incomplete sampling by the underlying data through interolating (or not) into data sparse regions. Using the native coverage (top) or the estimates restricted to common coverage (bottom) greatly alters the perceived degree of agreement between the independently produced products from various groups:
The conclusion of the second paper was as follows:

The driving rationale behind this work was the lack of explicit progress in the literature in assessing DTR changes between the fourth and fifth assessment reports of the IPCC. Based upon the findings herein, where a new assessment to be performed by IPCC of the observational DTR record at this time the text might read as follows (use of IPCC carefully calibrated uncertainty language and italicization [Mastrandrea et al., 2010] is intended).

It is virtually certain that globally averaged DTR has significantly decreased since 1950. This reduction in DTR is robust to both choice of data set and to reasonable variations in station selection and gridding methodology. However, differences between available estimates mean that there is only medium confidence in the magnitude of the DTR reductions. It is likely that most of the global-mean decrease occurred between 1960 and 1980 and that since then globally averaged DTR has exhibited little change. Because of current data sparsity in the digitized records, there is low confidence in trends and multidecadal variability in DTR prior to the middle twentieth century. It is likely that considerable pre-1950 data exist that could be shared and/or rescued and used in future analyses. All assessed estimates of global DTR changes are substantially smaller than the concurrently observed increases in mean and maximum and minimum temperatures (high confidence, virtually certain).

The datasets and code used are available via https://www.maynoothuniversity.ie/icarus/icarus-data

Monday, April 11, 2016

ICARUS researchers give public lecture last month in Customs House , Dublin.

Recent Flooding in Ireland: Hydro-Climatic aspects and associated impacts



Darren Clarke and myself Simon Noone gave a recent talk to the Irish Meteorological Society (IMS) in the Customs House, Dublin. The public lecture gave some insights into the causes and effects of the recent widespread flooding by looking through the lens of each of their areas of expertise. There was a good attendance of about 40 people from Met Éireann staff, engineers and even pilots to climate enthusiasts. After the talk we both responded to some interesting comments and received very positive feedback. We would like to thank Paul Halton and his colleagues at the IMS for inviting us and for their hospitality. For the lecture Darren focused on the social impacts of flooding and asked whether the current national approach to managing flood risks is fit for purpose. Darren is examining how societies adapt to climate change, specifically focusing on community adaptation to flood risk management strategies in Ireland.  I discussed the flooding in the context of the long-term hydrological cycle, how recent events fit into the historical record and what, if any, trends are emerging.  The recent rainfall extremes of late 2013/14 and 2015 were put into context over the longer term, using the recently updated Island of Ireland Precipitation (IIP) series 1850-2015.



 Key hydro-climatic results presented:
     
      Results indicate statistically significant increasing trends in winter and decreasing trends in summer precipitation.
      Across 13 IIP stations (mainly in west) so far 2014 was the wettest winter (Dec 2014, Jan/ Feb 2015) in Ireland over the past 165 years (see table 1).
      2015 has seen the wettest December at 16 IIP stations over the past 165 years and 2015 ranked either 2nd or 3rd for the other 9 IIP stations (see table 2).
      However, December 1978 was the wettest across eastern IIP stations (see table 2).


Table 1. Presents the wettest and driest seasons from 1850-2015 using the IIP series.





Table 2.  Presents the wettest December from 1850-2015 and corresponding standardized monthly anomaly for each of the IIP stations.






Key results on social impacts presented:
·         The economic impacts of flooding currently dominate policy, political and media debates at the expense of social costs such as physical and mental well-being. However, understanding the social impacts of flooding is crucial as the effects last long after a flood has receded
·         Greater attention to non-engineered flood defences will be needed in the coming decades if flood risks are to be managed sustainably and fairly.
·         The provision of flood insurance is likely to remain a contentious issue for those unable to avail of flood insurance nationally. The implementation of a flood re-insurance scheme as exists in the UK and France may be difficult to implement in Ireland for social, political and economic reasons.
·         Understanding of the local context in which new flood defences are to be located and the value of community input will be crucial if flood authorities are to be considered as legitimate both now and in the future.




Friday, March 25, 2016

On Hansen et al

By Peter Thorne

As I am getting dribs and drabs of queries from several angles on the Hansen et al paper that appeared this week in final form I thought I'd write a post (possibly against my better judgement). I was an invited reviewer and my initial and second reviews are available online. I stand by those. The whole paper has been a highly unusual experience to be part of the review process of, and not because its in the EGU Open Access journals. I have reviewed many times for EGU journals articles that have proceeded by a more traditional route. In this blog post I shall try to reflect upon the process, the potential issues that remain, and its reception. Much more can be found in my reviews which will likely help if you have issues with falling to sleep at night.

Before getting into the nitty gritty let me be clear on several points:
  • There is value in exploring possibilities of future behaviour of the climate system. We have not observed it long enough or well enough, and we do not (yet) have powerful enough and complete enough models, to absolutely rule out 'nasty surprises'. 

  • We are undertaking an unintended geoengineering project that is pushing the climate system away from what has been a remarkably (in geological terms) stable climate that has allowed agricultural, then industrial revolutions and modern society to develop. Married to other ongoing large perturbations to aspects of the Earth System such as ecosystem disturbance on an unprecedented scale we truly are entering uncharted territory. From a purely scientific perspective, the precautionary principle of reducing our environmental footprint should be pursued strongly.

  • It is the absolute right of the journal and its editors to publish any piece using their best judgement upon completion of a proper peer review process. I would strongly support any editor and any journal in the right to publish what they view as fit so long as the paper has undergone rigorous peer-review.

Peer-review process observations

The whole process was as if we had fallen through Alice's looking glass. The paper was trumpeted at a major news conference several days before the discussion paper was even published online and available for review. Many media outlets, completely incorrectly, reported this as a new paper. Discussion papers on EGU journal sites are not peer reviewed articles and do not therefore constitute scientific papers. Coincidentally, since then EGU now no longer typeset the discussion papers so that it is now more obvious whether the paper is a submitted manuscript or the final real deal. I have no idea whether these issues are linked.

This deliberate publicity surrounding a discussion paper (which to my knowledge is unique) led to unprecedented interest in the paper. By the time the comment period was closed there were over three times as many reviews as to the next most commented discussion paper in the journal's history. This included many off-topic comments including a long thread on the existence of the greenhouse effect. Ironically, this was one of the better responded to comments by the authors (more later ...).

Amongst the greenhouse effect deniers and other off-topic comments were unsolicited reviews from a large number of very well respected scientists expert in many fields pertinent to the paper including several colleagues who were (Coordinating) Lead Authors in the Fifth Assessment Report of IPCC or who have contributed to major works such as the annual state of the climate series. These reviews highlighted very many salient issues that the official reviewers failed to spot, and hence added substantial value.

In my view the responses from the paper author team to very many of the comments they received were inappropriate. Scientific peer review has a set of norms that you respond to the issues raised in a calm and measured manner including point-by-point responses that detail whether changes were made, what these were, and why. Instead, the authors chose to respond in many cases by writing discursive policy pieces that were too often non-responsive and often verged on playing the man and not the ball.

The reviewers (invited or otherwise) all donated the precious gifts of their time and their expertise to the peer review process. Their contributions both required and deserved scientifically substantive responses. Sadly, in many cases this is not what they received. The most egrerious example is the Drijfhout et al comment and its response. The reader should consider whether the response is polite and addresses the substantive points raised by the reviewers in a measured manner. In my judgement it does not. This is but the most obvious example of a systemic issue in how the reviews were dealt with by the authors during the public review segment of the process.

It is beholden upon senior members of the community to set an exemplar of expected behaviour. They are role models and they rightly or wrongly set or modify expectations of cultural norms, be that in climate science or elsewhere. My view is that the authors treated many of the reviews as a nuisance and did not provide the response that was justified to them that allowed the reviewers to fully understand how each of their review comments was dealt with. This included the public version response to my own invited review. It was not the behviour I would expect from such senior colleagues.

Science and content

Peer-review is a necessary but grossly insufficient condition for eventual acceptance of a new hypothesis as a scientific theory. Its a very weak and imperfect filter. So, publication is the first step on a long road to eventual either acceptance or rejection of the hypothesis. I'll briefly highlight here some of the open issues as I see it that lead me personally to put a very low prior on the work being correct. There are many more open issues detailed in mine and others' reviews at http://www.atmos-chem-phys.net/16/3761/2016/acp-16-3761-2016-discussion.html

The sea-level rise is prescribed and not predicted

The authors prescribe an extreme freshwater hosing (pumping of fresh water) into the sub-polar oceans. Hence the extreme short-term sea-level rise is not a prediction arising from the model at all, and assertions to the contrary are patently false. The authors basically give up on ice-sheet processes in climate models or even ice sheet models and decide to play what-if with some, in my view, poorly physically justified assumptions.

It is important to stress that there is therefore no rigourosly physically justified mecanism or basis underlying the posited multi-metre sea-level rise. They basically assume you start off adding one olympic swimming pool today, two tomorrow, four the next day etc. then when they determine they have added enough swimming pools of water they switch it off.


This is meant to approximate large-scale ice-sheet disintegration of Antarctic and Greenland ice sheets that are posited to add a huge volume of water on a short multi-decadal period. Such pulses have occured in the past, but primarily to my knowledge when transitioning from glacial to interglacial and presumably associated with the disintegration of the much more unstable Laurentide and Eurasian ice sheets. Antarctica and Greenland have remained ice caps whilst these other giant ice sheets have come and gone. There is therefore evidence the present ice sheets are much more stable. You'd have to look to colleagues who provided comments for further clarification though.

That said, West Antarctic is unstable, and we almost certainly have passed a tipping point that will see eventual c.8m rise but the scientific literature generally suggests this shall be a multi-century process. East Antarcic and Greenland have a few retrograde bedding outlet glaciers that with water intrusion could surge in the short term. But they are a bit like funnels draining huge areas and therefore the potential rate of addition will quickly become constricted as a result. A short term acceleration would not likely be a precursor to continued acceleration posited by the authors based upon current understanding of ice sheet dynamics. Reviewers more expert than I pointed these issues (and the lack of perceived realism) out but to my judgement were never adequately addressed.

I therefore see the claimed multi-metre sea-level rise as not a prediction and their characterisation as such is at best unfortunate. The fresh water injection is simply a prescribed forcing of the model system. The authors have no robust basis and ample comments on the record associated with the review calling into considerable doubt the verity of the underlying assumptions. So, the central headline of multi-metre sea-level is probably best considered an assumption instead of a prediction.

The hosing experiments also have an issue that the water is injected into the Oceans at -15C, which you can do in a model. I could inject water at absolute zero if I wished (although the model might, admittedly, crash). But in the real-world the water will be added at or close to -1.8C or higher. It is an open question whether this step is valid to approximate ice calving effect, and how it impacts the model predictions (more, again, on that later).

The Boulder deposit is at least as plausibly tsunami-mediated

One of the most eye-catching aspects of the paper was the apparently storm tossed relic boulders atop a current day cliff that was used to support an assertion of increased storminess in the Eemian. There is little doubting the boulder deposit was wave mediated and whilst there is some uncertainty inherent in dating it was at or around the late Eemian maximum. What is highly uncertain is that the waves were storm driven. These boulders were likely well in excess of 1,000 tonnes and i) dislodged from the sea-floor then ii) raised 20 metres. The amount of energy required to do this is tremendous. There are likely only a few places in the world where meteorologically driven waves get large enough to do this and in the modern climate the location is definitively not one of these. Wave power is a function of windspeed, fetch and duration. It is only really in mid-latitude locations, such as the west coast of Ireland, where such waves can plausibly occur. In the tropical locations although wind speed can be considerably higher fetch and duration are both limited. A local point tsunami which may have also led to local uplift (hence reducing the work required) as mentioned by expert reviewers is at least as likely.

The largest impacts go almost unmentioned


From an impacts perspective the biggest impact is not the sea-level rise at all. The model runs show very large perturbations to, in particular, northern hemisphere climate in the mid-21st Century. Basically many areas in Europe in particular enter a period at least as cold if not colder than the little ice age. The associated rainfall changes are equally as impressive. This would lead to large-scale challenges around provision of food, services etc. for global society and large-scale disruption of ecosystems. It is also entirely opposite to the direction of climate change that policy makers are currently planning for on this timescale. If (and in case you haven't twigged this yet that is an extremely big if in my expert judgement) the paper hypothesis were to eventuate, we'd have made massively incorrect adaptation decisions and investments and it would have large-scale implications for society.

Change of title

The original title was:
"Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 ◦C global warming is highly dangerous"

and became:
"Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 ◦C global warming could be dangerous"

This change has been variously discussed e.g. here amongst many others. I see no way that the original title could remain given:
  • The speculative nature of the freshwater injection (amount, rate and method)
  • Open questions over interpretation of the supporting observational and in particular palaeo-evidence and its interpretation
  • The non-deterministic nature of the climate system
  • The fact that the findings contravene accepted science based upon many decades of research and publications by many respected and established groups and individuals
The title was (and has to be) a reflection upon the paper contents and not on whether 2C does or does not reflect dangerous interference with the climate system. Those who willingly or unwittingly conflate these two issues are falling into a very obvious and dangerous (no pun intended) logic trap. The title should reflect the paper and not be a position statement upon whether some nominal departure from pre-industrial is safe or not. The two are completely seperate issues. To answer the second requires a holistic assessment of the totality of evidence for impacts of various thresholds on subcomponents of the Earth System. For that you want to wade through IPCC WG2 (book a few days out to do so) and not a single paper! The editor was entirely correct in that context to follow reviewer advice and insist on the change. To not do so would have been to discount the points raised above and have been extremely foolhardy.

Reception 

Here I shall just concentrate, briefly, upon the reception to the revised paper published this week. There is an interesting twitter thread here (see also here) on how two journalists came to polar opposite views. Obviously, I agree with Seth Borenstein's position here. Indeed, possibly the worst piece of journalism on the paper that dispensed with even any pretence of scientific balance was the piece at Slate. If you have got this far firstly congratulations and secondly you should be well sensitized to the fact that peer review is an imperfect filter. Being published does not make it part of a scientific 'canon' and nor should science be conflated with religion in such a manner (actually, at all).

Elsewhere I've seen pieces in the Washington Post and several other places that provide a degree of balance. Climatehome ran a nice piece after a phone interview. The Guardian has also decided to dispense pretty much entirely with balance. Twitter has been somewhat 'fun'.

Some of the articles, discussions and discourse have shown up a small number of the people supporting the paper to be no better in terms of behaviour, conspiracy theorising or reasoned logic than those on the opposite side of the aisle. Science works by a slow, deliberative methodical process. Single papers do not overturn received wisdom. Nor do blog articles (this one included) or comments below the line in various fora. A lot more light and a lot less heat is needed.

And people wonder why many of my colleagues are in general reticent to wade into the wider public debate ...

Tuesday, March 1, 2016

The Road from Paris: Low Carbon World or Dangerous Climate Change?

On Thursday 10 March we are hosting a seminar by Prof Kevin Anderson, one of the world's leading authorities on climate change.

The Road from Paris: Low Carbon World or Dangerous Climate Change?

Professor Kevin Anderson

11am Thursday, 10th March, Hamilton Institute Seminar Room (Room 317),
3rd Floor Eolas Building,

In this presentation, Kevin Anderson will revisit the scale of the climate challenge, arguing that whilst the science of climate change has progressed, there has been no corresponding acknowledgement of the rate at which our emissions from energy need to be reduced. He will suggest that the Paris Agreement exemplifies this duality. Similarly, he will argue that the focus on green growth continues to eclipse scientific analysis which demonstrates the need for radical social as well as technical change. Prof. Anderson will develop a quantitative framing of mitigation, based on IPCC carbon budgets, before finishing with more qualitative examples of what a genuine low-carbon future may contain.

Kevin Anderson is Professor of Energy and Climate Change in the School of Mechanical, Aerospace and Civil Engineering at the University of Manchester. He is Deputy Director of the Tyndall Centre for Climate Change Research and is research active with recent publications in Royal Society journals and Nature. He engages widely across all tiers of government; from reporting on aviation-related emissions to the EU Parliament, advising the Prime Minister's office on Carbon Trading and having contributed to the development of the UK's Climate Change Act.

Professor Anderson's work on carbon budgets has been pivotal in revealing the widening gulf between political rhetoric on climate change and the reality of rapidly escalating emissions. His work makes clear that there is now little chance of maintaining the rise in global temperature at below 2C, despite repeated high-level statements to the contrary. Moreover, Kevin's research demonstrates how avoiding even a 4C rise demands a radical reframing of both the climate change agenda and the economic characterisation of contemporary society.

Professor Anderson has a decade of industrial experience, principally in the petrochemical industry. He sits as commissioner on the Welsh Government's Climate Change Commission and is a Director of Greenstone Carbon Management.