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Communicating Key Figures from IPCC Reports to a Wider Public

If you were to think about ranking the most important Figures from the IPCC Fifth Assessment Report, I would not be surprised if the following one (SPM.10) did not emerge as a strong candidate for the number one slot:

IPCC AR5 Figure SPM.10

This is how the Figure appears in the main report, on page 28 (in the Summary for Policymakers) of The Physical Basis Report (see References: IPCC, 2013). The Synthesis Report includes a similar figure with additional annotations.

Many have used it in talks because of its fundamental importance (for example, Sir David King in his Walker Institute Annual Lecture (10th June 2015), ahead of COP21 in Paris). I have followed this lead, and am sure that I am not alone.

This Figure shows an approximately linear1 relationship between the cumulative carbon dioxide we emit2, and the rise in global average surface temperature3 up to 2100. It was crucial to discussions on carbon budgets held in Paris and the goal of stabilising the climate.

I am not proposing animating this Figure in the way discussed in my previous essay, but I do think its importance warrants additional attention to get it out there to a wider audience (beyond the usual climate geeks!).

So my question is:

“Does it warrant some kind of pedagogic treatment for a general audience (and dare I say, for policy-makers who may themselves struggle with the density of information conveyed)?”

My answer is yes, and I believe that the IPCC, as guardians of the integrity of the report findings, are best placed to lead such an effort, albeit supported by skills to support the science communications.

The IPCC should not leave it to bloggers and other commentators to furnish such content, as key Figures such as this are fundamental to the report’s findings, and need to be as widely understood as possible.

While I am conscious of Tufte’s wariness regarding Powerpoint, I think that the ‘build’ technique – when used well – can be extremely useful in unfolding the information, in biteable chunks. This is what I have tried to do with the above Figure in a recent talk. I thought I would share my draft attempt.

It can obviously do with more work, and the annotations represent my emphasis and use of  language4. Nevertheless, I believe I was able to truthfully convey the key information from the original IPCC Figure more successfully than I have before; taking the audience with me, rather than scaring them off.

So here goes, taken from a segment of my talk … my narrative, to accompany the ‘builds’, is in italics …

Where are we now?

“There is a key question: what is the relationship between the peak atmospheric concentration and the level of warming, compared to a late 19th century baseline, that will result, by the end of the 21st century?”

“Let’s start with seeing where we are now, which is marked by a X in the Figure below.” 

Unpacking SYR2.3 - Build 1

“Our cumulative man-made emissions of carbon dioxide (CO2) have to date been nearly 2000 billion tonnes (top scale above)”

“After noting that 50% of this remains in the atmosphere, this has given rise to an increase in the atmospheric concentration from its long-standing pre-industrial value of 280 parts per million to it current value which is now about 400 parts per million (bottom scale above).”

“This in turn has led to an increase in averaged global surface temperature of  1oC above the baseline of 1861 to 1880 (vertical scale above).”

Where might we be in 2100?

“As we add additional carbon dioxide, the temperature will rise broadly in proportion to the increased concentration in the atmosphere. There is some uncertainty between “best case” and “worst case” margins of error (shown by the dashed lines).” 

Unpacking SYR2.3 - Build 2

“By the end of the century, depending on how much we emit and allowing for uncertainties, we can end up anywhere within the grey area shown here. The question marks (“?”) illustrate where we might be by 2100.”

Can we stay below 2C?

“The most optimistic scenario included in the IPCC’s Fifth Assessment Report (AR5) was based on the assumption of a rapid reduction in emissions, and a growing role for the artificial capture of carbon dioxide from the atmosphere (using a technology called BECCS).” 

Unpacking SYR2.3 - Build 3

“This optimistic scenario would meet the target agreed by the nations in Paris, which is to limit the temperature rise to 2oC.”

“We effectively have a ‘carbon budget’; an amount of fossil fuels that can be burned and for us to stay below 2oC”. 

“The longer we delay dramatically reducing emissions, the faster the drop would need to be in our emissions later, as we approach the end of the ‘carbon budget’.” 

“Some argue that we are already beyond the point where we can realistically move fast enough to make this transition.” 

“Generally, experts agree it is extremely challenging, but still not impossible.”

Where will we be in 2100?  – Paris Commitments

“The nationally determined contributions (or NDCs) – the amounts by which carbon dioxide emissions will fall – that the parties to the Paris Agreement put forward have been totted up and they would, if implemented fully, bring us to a temperature rise of between 2.5 and 3.5 oC (and an atmospheric concentration about twice that of pre-industrial levels).”

Unpacking SYR2.3 - Build 4

 “Now, the nations are committed to increase their ‘ambition’, so we expect that NDCs should get better, but it is deeply concerning that at present, the nations’ current targets are (1) not keeping us unambiguously clear of catastrophe, and (2) struggling to be met. More ambition, and crucially more achievement, is urgent.”

“I have indicated the orange scenarios as “globally severe”, but for many regions “catastrophic” (but some, for example, Xu and Ramanathan5, would use the term “Catastrophic” for any warming over 3oC, and “Unknown” for warming above 5oC). The IPCC are much more conservative in the language they use.”

Where will we be in 2100? – Business As Usual Scenario

“The so-called ‘business as usual’ scenario represents on-going use of fossil fuels, continuing to meet the majority of our energy needs, in a world with an increasing population and increasing GDP per capita, and consequently a continuing growth in CO2 emissions.”

Unpacking SYR2.3 - Build 5

”This takes global warming to an exceptionally bad place, with a (globally averaged) temperature rise of between 4 and 6 oC; where atmospheric concentrations will have risen to between 2.5 and 3 times the pre-industrial levels.”

“The red indicates that this is globally catastrophic.”

“If we go above 5oC warming we move, according to Xu and Ramanathan,  from a “catastrophic” regime to an “unknown” one. I have not tried to indicate this extended vocabulary on the diagram, but what is clear is that the ‘business as usual’ scenario is really not an option, if we are paying attention to what the science is telling us.”

That’s it. My draft attempt to convey the substance and importance of Figure SPM.10, which I have tried to do faithfully; albeit adding the adjectives “optimistic” etc. to characterise the scenarios.

I am sure the IPCC could do a much better job than me at providing a more accessible presentation of Figure SPM.10 and indeed, a number of high ranking Figures from their reports, that deserve and need a broader audience.

© Richard W. Erskine


  1. The linearity of this relationship was originally discussed in Myles Allen et al (2009), and this and other work has been incorporated in the IPCC reports. Also see Technical Note A below.
  1. About half of which remains in the atmosphere, for a very long time
  1. Eventually, after the planet reaches a new equilibrium, a long time in the future. Also see Technical Note B below.
  1. There are different opinions are what language to use – ‘dangerous’, ‘catastrophic’, etc. – and at what levels of warming to apply this language. The IPCC is conservative in its use of language, as is customary in the scientific literature. Some would argue that in wanting to avoid the charge of being alarmist, it is in danger of obscuring the seriousness of the risks faced. In my graphics I have tried to remain reasonably conservative in the use of language, because I believe things are serious enough; even when a conservative approach is taken.
  1. Now, Elizabeth Kolbert has written in the New Yorker:

In a recent paper in the Proceedings of the National Academy of Sciences, two climate scientists—Yangyang Xu, of Texas A. & M., and Veerabhadran Ramanathan, of the Scripps Institution of Oceanography—proposed that warming greater than three degrees Celsius be designated as “catastrophic” and warming greater than five degrees as “unknown??” The “unknown??” designation, they wrote, comes “with the understanding that changes of this magnitude, not experienced in the last 20+ million years, pose existential threats to a majority of the population.”


  • IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovern- mental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pp.
  • IPCC, 2001: Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change [Houghton, J.T., Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K. Maskell, and C.A. Johnson (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 881pp.
  • Myles Allen at al (2009), “Warming caused by cumulative carbon emissions towards the trillionth tonne”,Nature 458, 1163-1166
  • Kirsten Zickfeld et al (2016), “On the proportionality between global temperature change and cumulative CO2 emissions during periods of net negative CO2 emissions”, Environ. Res. Lett. 11 055006

Technical Notes

A. Logarithmic relationship?

For those who know about the logarithmic relationship between added CO2 concentration and the ‘radiative forcing’ (giving rise to warming) – and many well meaning contrarians seem to take succour from this fact – the linear relationship in this figure may at first sight seem surprising.

The reason for the linearity is nicely explained by Marcin Popkiewicz in his piece “If growth of COconcentration causes only logarithmic temperature increase – why worry?”

The relative warming (between one level of emissions and another) is related to the ratio of this logarithmic function, and that is approximately linear over the concentration range of interest.

In any case, it is worth noting that CO2 concentrations have been increasing exponentially, and a logarithm of an exponential function is a linear function.

There is on-going work on wider questions. For example, to what extent ‘negative emissions technology’ can counteract warming that is in the pipeline?

Kirsten Zickfield et al (2016), is one such paper, “…[suggests that] positive CO2 emissions are more effective at warming than negative emissions are at subsequently cooling”. So we need to be very careful in assuming we can reverse warming that is in the pipeline.

B. Transient Climate Response and Additional Warming Commitment

The ‘Transient Climate Response’ (TCR) reflects the warming that results when CO2 is added at 1% per year, which for a doubling of the concentration takes 70 years. This is illustrated quite well in a figure from a previous report (Reference: IPCC, 2001):

TAR Figure 9.1

The warming that results from this additional concentration of CO2 occurs over the same time frame. However, this does not include all the the warming that will eventually result because the earth system (principally the oceans and atmosphere) will take a long time to reach a new equilibrium where all the flows of energy are brought back into a (new) balance. This will take at least 200 years (for lower emission scenarios) or much longer for higher emission levels.  This additional warming commitment must be added to the TCR. However, the TCR nevertheless does represent perhaps 70% of the overall warming, and remains a useful measure when discussing policy options over the 21st Century.

This discussion excludes more uncertain and much longer term feedbacks involving, for example, changes to the polar ice sheets (and consequentially, the Earth’s albedo), release of methane from northern latitudes or methane clathrates from the oceans. These are not part of the ‘additional warming commitment’, even in the IPCC 2013 report, as they are considered too speculative and uncertain to be quantified.

. . o O o . .

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Animating IPCC Climate Data

The IPCC (Intergovernmental Panel on Climate Change) is exploring ways to improve the communication of its findings, particularly to a more general  audience. They are not alone in having identified a need to think again about clear ‘science communications’. For example, the EU’s HELIX project (High-End Climate Impacts and Extremes), produced some guidelines a while ago on better use of language and diagrams.

Coming out of the HELIX project, and through a series of workshops, a collaboration with the Tyndall Centre and Climate Outreach, has produced a comprehensive guide (Guide With Practical Exercises to Train Researchers In the Science of  Climate Change Communication)

The idea is not to say ‘communicate like THIS’ but more to share good practice amongst scientists and to ensure all scientists are aware of the communication issues, and then to address them.

Much of this guidance concerns the ‘soft’ aspects of communication: how the communicator views themself; understanding the audience; building trust; coping with uncertainty; etc.

Some of this reflects ideas that are useful not just to scientific communication, but almost any technical presentation in any sector, but that does not diminish its importance.

This has now been distilled into a Communications Handbook for IPCC Scientists; not an official publication of the IPCC but a contribution to the conversation on how to improve communications.

I want to take a slightly different tack, which is not a response to the handbook per se, but covers a complementary issue.

In many years of being involved in presenting complex material (in my case, in enterprise information management) to audiences unfamiliar with the subject at hand, I have often been aware of the communication potential but also risks of diagrams. They say that a picture is worth a thousand words, but this is not true if you need a thousand words to explain the picture!

The unwritten rules related to the visual syntax and semantics of diagrams is a fascinating topic, and one which many – and most notably Edward Tufte –  have explored. In chapter 2 of his insightful and beautiful book Visual Explanations, Tufte argues:

“When we reason about quantityative evidence, certain methods for displaying and analysing data are better than others. Superior methods are more likely to produce truthful, credible, and precise findings. The difference between an excellent analysis and a faulty one can sometimes have momentous consequences”

He then describes how data can be used and abused. He illustrates this with two examples: the 1854 Cholera epidemic in London and the 1986 Challenger space shuttle disaster.

Tufte has been highly critical of the over reliance on Powerpoint for technical reporting (not just presentations) in NASA, because the form of the content degrades the narrative that should have been an essential part of any report (with or without pictures). Bulletized data can destroy context, clarity and meaning.

There could be no more ‘momentous consequences’ than those that arise from man-made global warming, and therefore, there could hardly be a more important case where a Tuftian eye, if I may call it that, needs to be brought to bear on how the information is described and visualised.

The IPCC, and the underlying science on which it relies, is arguably the greatest scientific collaboration ever undertaken, and rightly recognised with a Nobel Prize. It includes a level of interdisciplinary cooperation that is frankly awe-inspiring; unique in its scope and depth.

It is not surprising therefore that it has led to very large and dense reports, covering the many areas that are unavoidably involved: the cryosphere, sea-level rise, crops, extreme weather, species migration, etc.. It might seem difficult to condense this material without loss of important information. For example, Volume 1 of the IPCC Fifth Assessment Report, which covered the Physical Basis of Climate Change, was over 1500 pages long.

Nevertheless, the IPCC endeavours to help policy-makers by providing them with summaries and also a synthesis report, to provide the essential underlying knowledge that policy-makers need to inform their discussions on actions in response to the science.

However, in its summary reports the IPCC will often reuse key diagrams, taken from the full reports. There are good reasons for this, because the IPCC is trying to maintain mutual consistency between different products covering the same findings at different levels of detail.

This exercise is fraught with risks of over-simplification or misrepresentation of the main report’s findings, and this might limit the degree to which the IPCC can become ‘creative’ with compelling visuals that ‘simplify’ the original diagrams. Remember too that these reports need to be agreed by reviewers from national representatives, and the language will often seem to combine the cautiousness of a scientist with the dryness of a lawyer.

So yes, it can be problematic to use artistic flair to improve the comprehensibility of the findings, but risk losing the nuance and caution that is a hallmark of science. The countervailing risk is that people do not really ‘get it’; and do not appreciate what they are seeing.

We have seen with the Challenger reports, that people did not appreciate the issue with the O rings, especially when key facts were buried in 5 levels of indented bullet points in a tiny font, for example or, hidden in plain sight, in a figure so complex that the key findings are lost in a fog of complexity.

That is why any attempt to improve the summaries for policy makers and the general public must continue to involve those who are responsible for the overall integrity and consistency of the different products, not simply hived off to a separate group of ‘creatives’ who would lack knowledge and insight of the nuance that needs to be respected.  But those complementary skills – data visualizers, graphics artists, and others – need to be included in this effort to improve science communications. There is also a need for those able to critically evaluate the pedagogic value of the output (along the lines of Tufte), to ensure they really inform, and do not confuse.

Some individuals have taken to social media to present their own examples of how to present information, which often employs animation (something that is clearly not possible for the printed page, or its digital analogue, a PDF document). Perhaps the most well known example to date was Professor Ed Hawkin’s spiral picture showing the increase in global mean surface temperature:


This animation went viral, and was even featured as part of the Rio Olympics Opening Ceremony. This and other spiral animations can be found at the Climate Lab Book site.

There are now a number of other great producers of animations. Here follows a few examples.

Here, Kevin Pluck (@kevpluck) illustrates the link between the rising carbon dioxide levels and the rising mean surface temperature, since 1958 (the year when direct and continuous measurements of carbon dioxide were pioneered by Keeling)

Kevin Pluck has many other animations which are informative, particularly in relation to sea ice.

Another example, from Antti Lipponen (@anttilip), visualises the increase in surface warming from 1900 to 2017, by country, grouped according to continent. We see the increasing length/redness of the radial bars, showing an overall warming trend, but at different rates according to region and country.

A final example along the same lines is from John Kennedy (@micefearboggis), which is slightly more elaborate but rich in interesting information. It shows temperature changes over the years, at different latitudes, for both ocean (left side) and land (right side). The longer/redder the bar the higher the increase in temperature at that location, relative to the temperature baseline at that location (which scientists call the ‘anomaly’). This is why we see the greatest warming in the Arctic, as it is warming proportionally faster than the rest of the planet; this is one of the big takeaways from this animation.

These examples of animation are clearly not dumbing down the data, far from it. They  improve the chances of the general public engaging with the data. This kind of animation of the data provides an entry point for those wanting to learn more. They can then move onto a narrative treatment, placing the animation in context, confident that they have grasped the essential information.

If the IPCC restricts itself to static media (i.e. PDF files), it will miss many opportunities to enliven the data in the ways illustrated above that reveal the essential knowledge that needs to be communicated.

(c) Richard W. Erskine, 2018


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