Archive: COP21 daily report 4: The need for innovation (but do not call it innovation)

Cabot Institute Director Professor Rich Pancost will be attending COP21 in Paris as part of the Bristol city-wide team, including the Mayor of Bristol, representatives from Bristol City Council and the Bristol Green Capital Partnership. He and other Cabot Institute members will be writing blogs during COP21, reflecting on what is happening in Paris, especially in the Paris and Bristol co-hosted Cities and Regions Pavilion, and also on the conclusion to Bristol’s year as the European Green Capital.  Follow #UoBGreen and #COP21 for live updates from the University of Bristol.  

Part 4


For the past two days, a delegation of us have been representing Bristol City Council and a group of Bristol businesses at the Sustainable Innovation Forum (SIF) at Paris.  Our group included Bristol Mayor George Ferguson, who spoke on Tuesday; Amy Robinson, of Low Carbon Southwest and the driver behind the Go Green business initiative; Bristol City Council representatives Stephen Hillton and Mhairi Ambler; and Ben Wielgus of KPMG and Chris Hayes of Skanska, both Bristol Green Capital sponsors. 

This was the COP21 ‘Business event’ and aspects of this have been rather sharply targeted by Paris activists. There is a legitimate question of whether corporate sponsors are engaging in greenwashing, but this was not my perception from inside Le Stade de France.  There were some major fossil fuel dependent or environmentally impactful companies in attendance, but they seemed genuinely committed to reducing their environmental impact.  Their actions must be transparent and assessed, and like all of us, they must be challenged to go further. This is why it was fantastic that Mindy Lubber, President of Ceres, was speaking. Ceres is a true agent of change, bringing a huge variety of businesses into the conversation and working with them to continually raise ambition.

The majority of these businesses, just like those that attended Bristol’s Business Summit in October, are clearly and objectively devoted to developing new technologies to address the world’s challenges,. Whether it be new solar tech that will underpin the PVC of 2050 or innovative new ways to deploy wind turbines cheaply and effectively in small African villages, it is no longer ‘business’ that is holding back climate action and in many cases they are leading it. 

And we need them to do so.  We need them to develop new products and we need them to be supported by government and Universities.  We need them because we need new innovation, new technology and new infrastructure to meet our environmental challenges. 

One of the major themes of the past two days has been leadership in innovation, an ambition to which the University of Bristol and the City of Bristol aspires – like any world-class university and city.  We have profound collective ambitions to be a Collaboratory for Change. These are exemplified by Bristol is Open, the Bristol Brain and the Bristol Billion, all endeavours of cooperation between the University of Bristol and Bristol City Council and all celebrated by George Ferguson in his speech to the SIF attendees yesterday.

This need for at least some fundamentally new technology is why the Cabot Institute has launched VENTURE. It is why the University has invested so much in the award-winning incubator at the Engine Shed. It is why we have devoted so much resource to building world-leading expertise in materials and composites, especially in partnership with others in the region.

We do not need these innovations for deployment now – deployment of already existing technology will yield major reductions in our carbon emissions – but we need to start developing them now, so that we can achieve more difficult emissions reductions in 20 years.  Our future leaders must have an electrical grid that can support a renewable energy network. Our homes must have been prepared for the end of gas.

And we will need new technology to fully decarbonise.

We effectively have no way to make steel without burning coal to melt iron – we either need new tech in recycling steel, need to move to a post-steel world, need to completely redesign steel plants, or some combination of all three.

We will need new forms of low-energy shipping. Localising manufacturing and recycling could create energy savings in the global supply chain.  But we will always have a global supply chain and eventually it must be decarbonised.

Similarly, we will need to decarbonise our farm equipment.  At heart, I am still an Ohio farm boy, and so I was distracted from my cities-focus to discuss this with Carlo Lambro, Brand President of New Holland.  Their company has made some impressive efficiency gains in farm equipment, especially with respect to NOx emissions, but he conceded that a carbon neutral tractor is still far away – they require too much power, operating at near 100% capacity (cars are more like 20-30%).  He described their new methane-powered tractor, which could be joined up to biogas emissions from farm waste, but also explained that it can only operate for 1.5 hours.  There have been improvements… but there is still a long way to go. I appreciated his engagement and his candor about the challenges we face (but that did not keep me from encouraging him to go faster and further!).

Finally, if we really intend to limit warming to below 2C, then we will likely need to capture and store (CCS) some of the carbon dioxide we are adding to the atmosphere. Moreover, some of the national negotiators are pushing for a laudable 1.5C limit, and this would certainly require CCS. In fact, the need for the widespread implementation of such technology by the middle of this century is explicitly embedded in the emissions scenarios of IPCC Working Group 3. That is why some of our best Earth Scientists are working on the latest CCS technology.

Unfortunately, CCS illustrates how challenging innovation can be – or more precisely, as articulated by Californian entrepreneur Tom Steyer, how challenging it can be to develop existing technology into useful products. The CCS technology exists but it is still nascent and economically unviable.  It must be developed.  Given this, the recent cancellation of UK CCS projects is disappointing and could prove devastating for the UK’s intellectual leadership in this area.  The consequences of this decision were discussed by Nicola Sturgeon in a panel on energy futures and she renewed Scotland’s firm commitment to it.

This issue exemplifies a wider topic of conversation at the SIF: social and technological innovation and development requires financing, but securing that financing requires safety.  Skittish investors do not seek innovation; they seek safe, secure and boring investment. And SIF wrapped up by talking about how to make that happen.

First, we must invest in the research that yields innovations. We must then invest in the development of those innovations to build public and investor confidence.  Crucial to both of those is public sector support. This includes Universities, although Universities will have to operate in somewhat new ways if we wish to contribute more to the development process. We are learning, however, which is why George Ferguson singled out the Engine Shed as the world’s leading higher education based incubator.

Second, and more directly relevant to the COP21 ambitions, businesses and their investors need their governments to provide confidence that they are committed to a new energy future.  It has been clear all week that businesses will no longer accept the blame for their governments’ climate inaction.

Instead, most businesses see the opportunity and are eager to seize it. As for the few businesses that cling to the past? Like all things that fail to evolve, the past is where they shall remain.  The new generation of entrepreneurs will see to that. Whether it be the new businesses with new ideas or the old businesses that are adapting, the new economy is not coming; it is already here.

The forecast is for volatility.


The Climate Change challenge to society, industry and investors is not well represented by the concept of long-term global warming (although that will happen) but rather as system wide and unpredictable shifts to a world characterised by increasingly volatile food, water, security and weather.

Climate scientists continually emphasise the difference between the climate and weather – the former being a long-term description of the average state of our planet and the latter being the expression of that climate on highly localised and short-term timescales. Our understanding of climate is relatively robust, based on physical principles that in many cases were established hundreds of years ago.  In contrast, our ability to predict how that will impact a specific region at a specific point in the future, i.e. weather, is weaker due to how climate change is manifested through a very complex system.

Long-term climate change is typically represented by the iconic IPCC global warming figure showing the ~1C warming of the past century and the near certain warming up to the year 2100, the forecasts and uncertainty derived from an ensemble of climate models. They collectively depict a relatively monotonic warming if we continue a ‘business-as-usual’ fossil fuel/agriculture trajectory, as well as the associated uncertainty, resulting in cumulative global warming by 2100 of about 4 to 6C.  But this trend does not say anything about the year-to-year variability in any particular place.  It is not a weather forecast.

It is possible – unlikely but possible – that in the year 2100, in a world 4C warmer than that of today, the Northeast of the United States will be experiencing its coldest year on record. These deviations from the norm could be due to natural variability over-riding the larger global warming trend in that particular time and place.  It could be due to global warming having unexpected impacts on ocean and atmosphere circulation.  In any case, there are very good reasons for scientists to focus on long-term climate trends, but those trends do not reflect what it will be like to live in a warmer world.  They do not reflect how people will be affected, what they will react to or how, or the pressures under which politicians will be making decisions.

The defining features of climate change will be volatility and uncertainty.

Crucially, therefore, these future forecasts fail to inform our understanding of the socio-political landscape relevant to investors.

If climate change is gradual, then the savvy investor should adopt a wait and see attitude.  As warming continues, as damage gradually accrues and as political rhetoric (and regulations) grow sharper, investors can adopt different risk strategies, with some inevitably bailing out from high risk ventures too soon and others too late.

But this is not how climate change will be experienced. It will be experienced as extremes, the unexpected, the unusual.  In some areas, the 1-in-20 year heat wave will be 10C greater than it is today (i.e. England could experience ~40C heat waves every 20 years rather than ~30C heat waves).  A ramped up hydrological cycle on a warmer planet will cause some areas to become wetter and others drier; but in all areas, actual rainfall events are likely to become more intense. In 2050 – or even 2020 – the Midwest of the United States might experience pronounced floods or be in the middle of a devastating 5-year drought.

This volatility is being manifested today. Extremes are part of natural climate variability and we have warmed the world by 1C, the latter sufficient to amplify and complicate the former.  In particular, there is strong evidence that warming is already amplifying heat waves, droughts and floods.  And most recently, horrifying wildfires. By extension, we could be on the verge of experiencing particularly acute volatility in food prices. Investors in every sector should be deeply concerned about this increased volatility.

However, investors in the energy and fossil fuel sectors should be additionally concerned by how this volatility impacts policy. 

If nations actually do enact policies that could limit global warming to 2C (let alone 1.5 C, the ambition of the Paris Agreement), then most of the fossil fuel sector’s assets will become stranded.  In fact, even policies that limit warming below 5C will strand significant fossil fuel assets. Many are arguing that until actual policies are put in place, any disinvestment is premature.  ExxonMobil has further argued to the SEC (unsuccessfully in 2015-2016) that they do not believe nations will enact such policies and therefore they have no need to plan for them.

Such attitudes are understandable in a world of long-term, incremental change and politicians reluctant to institute policies that overly disrupt the status quo.  But incremental change is not the forecast.  Volatility is the forecast. Superstorm Sandy had a minor but real impact on the politics of the US Northeast.  What would be the consequence of three such storms happening back to back? What would have been the consequences if it had knocked out one of NY City’s central distribution centres, causing tens of millions to face food shortages?  Heat waves in the Middle East resulted in thousands of deaths last summer; what are the political consequences of a somewhat more extended heat wave that results in tens or hundreds of thousands of deaths?  What are the political consequences of two more years of California drought, especially if it begins to drive farms out of business and food prices upwards? Or if wildfires rip through more populated areas?

I do not pretend to know what tipping points could cause policy makers to switch gears from prevarication and incremental steps to the drastic policy changes that would limit global warming to 2C and be devastating for certain fossil fuel industries and their investors. But we have seen how a combination of factors has devastated the coal industry, with its value perhaps never to be recovered. We have seen how Fukishima had huge impacts not only on the nuclear industry in Japan but also in Germany – with knock-on effects across the EU.

Given this, I can see no logical reason for investors to not demand as much information as they can from their investments, especially those vulnerable to policies that would limit climate change. I can understand if investors want to bet against politicians making difficult choices!  But to also bet against technological innovation (fusion, microgrids, batteries)? To bet against economics (decreasing price of renewables)?  Ultimately, to bet against people who will be on the front lines of this volatility? Regardless, if fund managers want to make the best possible bets – and they are legally compelled to do so – they need the best possible knowledge. And this begs the question: why would a responsible fund manager not ask all of their major investments – not only but especially the fossil fuel industry – to conduct 1.5 C stress tests.

Different investors – with different risk tolerances – will read the above through different lenses and reach different conclusions.  Nonetheless, given the complexity and unpredictability inherent in the climate change challenge, it is astonishingly naïve for any company to argue that politicians will never act on the commitments made in Paris and thereafter. Investors should demand a clear message from those companies that they understand both systemic climate change risks as well as the associated policy and economic risks to their assets. And investors should have confidence that those in whom they have invested have planned for both.


Some final thoughts that did not quite get it into the blog but bear re-emphasis. The key point is that climate change will create volatility and that is not good for anyone.  It is especially bad for investors, who rely on stability and predictability. And most of all, investors rely on confidence.  The crash of 2008 was not due simply to an accumulation of subprime mortgage funds but rather a loss of market confidence in them arising from increasing awareness of those fund’s quality; the bubble burst. If (when) climate change causes investors to lose confidence in a property market, the re-insurance sector, the construction industry, a government bond market, it is almost certain to create widespread financial shocks.  The Bank of England Governor Mark Carney quite correctly views this as systemic risk.

But it is a bit less clear what might cause that loss of confidence.  Will it be a particularly severe event in terms of financial or humanitarian terms or will it be a shocking and unprecedented event.  Or an accumulation of events. My suspicion is that it will be the cumulative exhaustion associated with volatility and unpredictability. Markets will adapt to long-term gradual change, but adapting to a volatile and uncertain world is far harder.

And unfortunately, volatility is exactly what is happening now and almost certain to be one of the defining features of our future.

Adapted from Blue & Green Tomorrow  (see page 29 of the Guide to Sustainable Investing for original).

Adaptation or Mitigation? Both. Obviously.

Ever since the historic Paris Agreement on climate change, policy makers, business leaders, scientists, and investors have been debating its near- and long-term implications. It was and remains an ambitious agreement, with a goal to limit warming to well below 2°C. But it is also an agreement with a weak enforcement and reporting framework and the current “intended nationally determined contributions” limit warming to only about 3 to 3.5°C—and more after this century.

This creates a rather politically and potentially legally fraught terrain for decision makers. The list of critical questions is getting longer:

  • When will imminent climate impacts drive policy change?
  • How will governments change:
    • energy-subsidy programs.
    • incentives for innovation and infrastructure investments by companies and long-horizon investors.
    • carbon taxes.
    • accountability standards relating to investors’ role as stewards.
  • How quickly will new energy sources come on line and how messy and volatile will the transition be?
  • And crucially, will businesses and institutional investors lead these initiatives or be victims to them?

At the heart of these discussions is one of the oldest debates in the climate change communication and policy arena—should we focus on mitigation or adaptation? Up until a few years ago, scientists were reluctant to discuss adaptation because of the recognized negative impact it had on individual and social behaviour change. Even if very costly, high risk and disruptive adaptation strategies provided an ‘escape clause’ and a justification to procrastinate on unpopular or challenging near-term decisions. More recently, however, the debate has taken on new dimensions. Given the facts that global warming has already reached or exceeded 1°C, that even more warming is already locked in, and that even the most ambitious national pledges would likely fail to keep warming below 3°C, let alone 2°C, many are privately arguing that mitigation is no longer viable and the focus should be on adaptation.

Now, as then, the sole focus on adaptation is deeply flawed.

Let’s start with those arguing that either the mitigation opportunity has passed by or that nations will be unwilling to enact the perceived painful policies necessary to limit warming. Aside from the ethical flaws of this argument, it would be naive for investors to assume that an agreement among nearly 200 nations will have no legal or policy consequences; even the INDCs, though they are incomplete measures, will require vast social, economic, and political change.

However, the central argument that mitigation remains vital and necessary is scientific. Those suggesting that mitigation has failed or will fail tend to fixate on the 2°C global warming limit at the centre of policy discussions for the past decade and the acute challenge we face in achieving it. There are good reasons to have a 2°C (or lower) limit, as that is the representative temperature when a number of system changes begin to occur, very high sea level rise becomes locked in, and changes in weather, including extreme events, becomes very difficult to predict, all of which will have dramatic economic and social impacts.

Climate change, however, is not a binary. We are already experiencing the consequences of anthropogenic climate disruption. These will become more pronounced as the planet approaches 2°C of warming. And they will become even worse at higher CO2 levels and higher global temperatures. The Earth system does have some bimodal features but the tipping points between them occur at a range of temperatures, with great uncertainty, and in complex ways.

Sea level rise showcases this well. In the Pliocene era, about 3 million years ago, CO2 levels were 400 to 500 ppm; temperatures were 2°C higher; and the sea level was 5 to 20 metres higher than today. Such changes would be devastating in modern times, with huge infrastructure costs, long-term economic consequences, and unprecedented social displacement. The last time Earth experienced 500 to 1000 ppm CO2, however, temperatures were about 4-5°C higher, and sea level was 70-100 metres higher than today. These represent a long-term Earth system equilibrium so neither scenario is expected for the next several hundred years or more; but they are illustrative of the profound differences between a 2°C and 5°C global warming scenario.

Crucially, unabated biomass loss and fossil fuel burning—especially with new technologies allowing unconventional shale gas and tar sands to be exploited—could result in warming of 5 to 6°C, maybe even more depending on how effective we are at tapping new reservoirs, whether climate sensitivity is at the high or low end of our estimates, and whether positive feedbacks in the Earth system will exacerbate our fossil fuel impacts.

To the best of our understanding, 5 to 6°C global warming will have vast and devastating impacts on our climate and ecosystems, probably with similarly devastating impacts on society. In short, even if we fail to sufficiently curtail fossil fuel usage to limit global warming to 2°C, we must certainly do so to prevent far more extreme warming. As long as fossil fuel resources exist to tempt us, mitigation will always be a priority.

And yet.

Even under our most ambitious mitigation strategies, climate change will happen and we must adapt to it. Already, with the Earth having experienced only about 1°C warming, droughts, floods and heat waves—many of which have been directly attributed to global warming—are occurring. When that warming has combined with natural climate variability, which happened with the strong El Niño of this past year, local affects are even more pronounced, whether it be global coral bleaching or crippling heat waves in the tropics. These events, in turn, have affected food security, productivity and global security. They could destroy marine ecosystems and in turn one of our most important food sources and one of nature’s most beautiful features.

And yet, we are committed to further emissions, further warming, and further climate disruption. It is hoped that if we limit warming to 1.5°C, the most severe aspects of sea level rise, extreme weather and ecosystem disruption will be avoided—but we do not know that and some have argued that we have already locked in up to 4 metres of sea level rise. If we limit warming to 2°C, we will almost certainly have to adapt to sea level rise, human displacement, infrastructure devastation; it will also expose us to feedback risks that could add additional warming beyond our direct influence.  And there are many reasons to think that these impacts will be inequitable, with the poorest suffering the most.

There is no choice between avoiding severe climate disruption or adapting to it. We will do both. We will leave fossil fuel assets in the ground and we will adapt to some environmental disruption. The only choices we have are how we balance those two needs, how we do so fairly and equitably, and how rapidly we make the inevitable transition.

Adapted from a blog originally published for Preventable Surprises.

An ancient rapid climate change event – still much slower than what we are doing today.

In 2015, I was interviewed by Susan Kucera when she visited Bristol to show her beautiful film on climate change – Breath of Life.  Working with Jeff Bridges, she has created a powerful new film – Living in the Future’s Past – that features those interviews with me and many other scientists, psychologists, politicians and philosophers. My own contributions on climate change reflect on the history of our planet and how that provides perspective for our current unprecedented rate of climate change. To elaborate on that, I am posting some recent press releases on the research that informed my reflections (and yet to be published at the time of interview). In particular, in the movie I discuss our research a carbon dioxide increase (and associated global warming event) that occurred over 100 million years ago. It is an event that we consider fast geologically but happened 100s of times more slowly than the carbon dioxide we are adding today.

Image result for living in the futures past


The research was led by Dr David Naafs, a Research Fellow with me in the Organic Geochemistry Unit; it was based on Dutch Rubicon Grant he was awarded in 2012.  But we need to acknowledge three others.  First, our colleague Dani Schmidt has been grappling with the topic of rapid geological carbon release events for years; it was her work with Andy Ridgwell that began to reveal that these geologically rapid events were not at all rapid by modern standards.  Second, the work would not have been possible without a fantastic geological section; the Cau section in Spain had been studied for years prior to this by several colleagues at the University of Jaen, including Jose Manuel Castro and Maria Luisa Quijano.  All of these brilliant scientists – and many others – have helped shape our understanding of the geological past.  And almost all come to the same conclusion: although geology is a vast and powerful force, rarely does it act with the terrible speed and efficiency with which we are extracting fossil fuels from the Earth and transforming our carbon cycle.

From our press release at the time:

University of Bristol Cabot Institute researchers and their colleagues today published research that further documents the unprecedented rate of environmental change occurring today, compared to that which occurred during natural events in Earth’s history.

The research, published online on the 4th of January (2016) in Nature Geosciences (‘Gradual and sustained carbon dioxide release during Aptian Oceanic Anoxic Event 1a’), reconstructs the changes in atmospheric carbon dioxide (pCO2) during a global environmental change event that occurred about 120 Million years ago. New geochemical data provide evidence that pCO2 increased in response to volcanic outgassing and remained high for around 1.5-2 million years, until enhanced organic matter burial in an oxygen-poor ocean caused a return to original levels.

Lead author Dr David Naafs explained: ‘Past records of climate change must be well characterised if we want to understand how it affected or will affect ecosystems. It has been suggested that the event we studied is a suitable analogue to what is happening today due to human activity and that a rapid increase in pCO2 caused ocean acidification and a biological crisis amongst a group of calcifying marine algae. Our work confirms that there was a large increase in pCO2. The change, however, appears to have been far slower than that of today, taking place over hundreds of thousands of years, rather than the centuries over which human activity is increasing atmospheric carbon dioxide levels. So despite earlier claims, our research indicates that it is extremely unlikely that widespread surface ocean acidification occurred during this event.’

The observation that yet another putative ‘rapid’ geological event is occurring perhaps a thousand times slower than today and not associated with widespread surface ocean acidification has been the focus of much recent research at the University of Bristol. Co-author Professor Daniela Schmidt, who was also a Lead Author on the IPCC WGII report on Ocean systems, emphasised that today’s finding builds on one of the IPCC’s key conclusions: that the rate of environmental change occurring today is largely unprecedented in Earth history.  She said, ‘This is another example that the current rate of environmental change has few if any precedents in Earth history, and this has big implications for thinking about both past and future change.’

The research was possible due to the exceptional Spanish section that the team analysed. Co-author Professor José Manuel Castro of the University of Jaen adds, ‘The sediments at Cau accumulated very rapidly resulting in an expanded section. This allowed the high resolution multidisciplinary analysis that are the basis for this important study.’

Senior Author and Director of the University’s Cabot Institute, Professor Rich Pancost, added,  ‘We often use the geological record to help us test or expand our understanding of climate change, for example, determining the sensitivity of Earth’s temperature to higher CO2 levels. But testing the risks associated with the pace of modern environmental change is proving problematic, due to a lack of similar rapid changes in the geological past. Consequently, these risks, in this case to the marine ecosystems on which so many of us depend, remain associated with profound uncertainty. Decreasing CO2 emissions, as recently agreed in Paris, will be necessary to avoid these risks.’

This research was published in Nature Geosciences.

See also the News and Views perspective.

The research was funded by a NWO (Netherlands Funding Council) Rubicon Grant to David Naafs and NERC funding to Rich Pancost.


It has been about 3 million years since the Earth’s atmosphere last had 400 ppm of carbon dioxide

In 2015, I was interviewed by Susan Kucera when she visited Bristol to show her beautiful film on climate change – Breath of Life.  Working with Jeff Bridges, she has created a powerful new film – Living in the Future’s Past – that features those interviews with me and many other scientists, psychologists, politicians and philosophers. My own contributions on climate change reflect on the history of our planet and how that provides perspective for our current unprecedented rate of climate change. To elaborate on that, I am posting some recent press releases on the research that informed my reflections (and yet to be published at the time of interview).

Image result for living in the futures past


In particular, I discuss work in collaboration with colleagues at Southampton, showing that the Earth’s current pCO2 level of 400 ppm is higher than it has been for nearly 3 million years (this work also refers to our research on the Pliocene, which I have also written about here). 

A multinational research team, led by scientists at the University of Southampton and the University of Bristol Cabot Institute, has developed new records of past CO2 levels.  These reveal that the CO2 content of the Earth’s atmosphere between 2.8 to 3.3 million years ago, were higher than that of the pre-industrial Earth and likely higher than at any other point over the past two million years – but similar to values reached in the past decade.

The new records are based on geochemical analyses of marine sediments. These have been measured using techniques developed at Bristol and Southampton over the past decade. The Bristol team includes Professor Richard Pancost from the University of Bristol, Director of the Cabot Institute and the Primary Investigator of the wider grant under which this research was conducted, as well as Dr Marcus Badger, Professor Dan Lunt and Professor Daniela Schmidt.  Professor Pancost explains: “We cannot directly measure the CO2 levels on Earth prior to about 1 million years ago, and so we instead use proxies.  In the case of our project, funded by the NERC, we used a combination of approaches based on the chemical signatures of organisms preserved in sediments at the bottom of the sea.”

By studying the relationship between CO2 levels and climate change during a warmer period in Earth’s history, the team have been able to estimate how the climate will respond to increasing levels of carbon dioxide, a parameter known as ‘climate sensitivity’.  The findings, which have been published in Nature, fall in line with estimates in the most recent IPCC report.  “Today the Earth is still adjusting to the recent rapid rise of CO2 caused by human activities, whereas the longer-term Pliocene records document the full response of CO2-related warming,” says Southampton’s Dr Gavin Foster, co-lead author of the study.  “Our estimates of climate sensitivity lie well within the range of 1.5 to 4.5°C warming per CO2 doubling summarised in the latest IPCC report. ”

Professor Dan Lunt, also of the University of Bristol and the Cabot Institute adds: “We compared the temperature response to CO2 change in the warm Pliocene to that during colder times, like the glacial cycles of the last 800 thousand years.  The temperature response was around half that of the colder period, but that difference can be largely resolved by considering the growth and retreat of large continental ice sheets during more recent glacial cycles. These ice sheets reflect a lot of sunlight and their growth consequently amplifies the impact of CO2 changes, but they were smaller and less variable during the warm Pliocene.”

“Our new records also reveal an important change at around 2.8 million years ago, when levels dropped to values of about 280 ppm, similar to those seen before the industrial revolution,” says lead author of the study Dr Miguel Martinez-Boti, also from Southampton. “This appears to have caused a dramatic global cooling that initiated the ice-age cycles that have dominated Earth’s climate ever since.”

Professor Pancost added: “When we account for the influence of the ice sheets, we can confirm that the Earth’s climate changed with a similar sensitivity to overall forcing during both warmer and colder climates. During the Pliocene the Earth was warmer by around 2°C than it is today and atmospheric CO2 levels were around 350-400 parts per million (ppm), similar to the levels reached in recent years.  This suggests that in the long term, we have already committed to 2 °C warming, and future CO2 increases will only add to that.”

NOTE: Subsequent to this work, we pushed this methodology further back into Earth history, into the Eocene (30 to 50 million years ago).  This was probably the last time the Earth had pCO2 levels similar to what we might reach by the end of the century (>800 ppm).  

Plio-Pleistocene climate sensitivities evaluated using high-resolution CO2 records by M.A. Martínez-Botí, G.L. Foster, T. B. Chalk, E.J. Rohling, P.F. Sexton, D.J. Lunt, R.D. Pancost, M.P.S. Badger & D.N. Schmidt DOI: 10.1038/nature14145

This work was funded by an NERC grant to Pancost (PI), G Foster, D Schmidt and D Lunt.

Back to the Future ‘Hothouse’

Our current global warming target and the trajectory it places us on, towards a future ‘Hothouse Earth’, has been the subject of much recent discussion, stimulated by a paper by Will Steffen and colleagues.  In many respects, the key contribution of this paper and similar work is to extend the temporal framing of our climate discussions, beyond 2100 for several centuries or more.  Analogously, it is useful to extend our perspective backwards to similar time periods, to reflect on the last time Earth experienced such a Hothouse state and what it means.

The Steffen et al paper allows for a variety of framings, all related to the range of natural physical, biological and chemical feedbacks that will amplify or mitigate the human intervention in climate.  [Note: the authors frame their paper around the concept of a limited number of steady state scenarios/temperatures for the Earth.  They then argue that aiming for 2C, potentially an unstable state, could trigger feedbacks tipping the world towards the 4C warmer Hothouse.  I find that to be somewhat simplistic given the diversity of climate states that have existed, if even transiently, over the past 15 million years, but that is a discussion for another day.] From my perspective, the most useful framing – and one that remains true to the spirit of the paper is this: We have set a global warming limit of 2C by 2100, with an associated carbon budget. What feedback processes will that carbon budget and warming actually unleash over the coming century,  how much additional warming will they add, and when?

That is a challenging set of questions that comes with a host of caveats, most related to the profound uncertainty in the interlinked biogeochemical processes that underpin climate feedbacks. For example, as global warming thaws the permafrost, will it release methane (with a high global warming potential than carbon dioxide)? Will the thawed organic matter oxidise to carbon dioxide or will it be washed and buried in the ocean? And will the increased growth of plants under warmer conditions lead instead to the sequestration of carbon dioxide? The authors refer to previous studies that suggest a permafrost feedback yielding an additional 0.1C warming by the end of the century; but there is great uncertainty in both the magnitude of that impact and its timing.

And timing is the great question at the heart of this perspective piece.  I welcome it, because too often our perspective is fixed on the arbitrary date of 2100, knowing full well that the Earth will continue to warm and ice continue to melt long after that date.  In this sense, Steffen et al is not a contradiction to what has been reported from the IPCC but an expansion on it.

Classically, we discuss these issues in terms of fast and slow feedbacks, but in fact there is a continuum between near instantaneous feedbacks and those that act over hundreds, thousands or even millions of years.  A warmer atmosphere will almost immediately hold more water vapour, providing a rapid positive feedback on warming – and one that is included in all of those IPCC projections.  More slowly, soil carbon, including permafrost, will begin to oxidise, with microbial activity stimulated and accelerated under warmer conditions – a feedback that is only just now being included in Earth system models.  And longer term, all manner of processes will come into play – and eventually, they will include the negative feedbacks that have helped regulate Earth’s climate for the past 4 billion years.

There is enough uncertainty in these processes to express caution in some of the press’s more exuberant reporting of this topic.  But lessons from the past certainly underscore the concerns articulated by Steffen et al.  We think that the last time Earth had 410 ppm CO2, a level similar to what you are breathing right now, was the Pliocene about 3 million years ago.  This was a world that was 1 to 2C warmer than today (i.e. 2 to 3C warmer than the pre-industrial Earth) and with sea levels about 10 m higher.  This suggests that we are already locked into a world that far exceeds the ambitions and targets of the Paris Agreement.  This is not certain as we live on a different planet and one where the great ice sheets of Greenland and Antarctica might not only be victims of climate change but climate stabilisers through ice-sheet hysteresis. And even if a Pliocene future is fixed, it might take centuries for that warming and sea level change to be realised.

But that analogue does suggest caution, as advocated by the Hothouse Earth authors.

It also prompts us to ask what the Earth was like the last time its atmosphere held about 500 ppm CO2, similar to the level needed to achieve the Paris Agreement to limit end-of-century warming below 2C.  A useful analogue for those greenhouse gas levels is the Middle Miocene Climate Optimum, which occurred from 17 to 14.7 million years ago.


Figure showing changes in ocean temperature (based on oxygen isotopic compositions of benthic foraminifera) and pCO2 over the past 60 million years (from Palaeo-CO2).  Solid symbols are from the d11B isotope proxy and muted symbols are from the alkenone-based algal carbon isotope fractional proxy. Note the spike in pCO2 associated with the MMCO at about 15 million years ago.

As one would expect for a world with markedly higher carbon dioxide levels, the Miocene was hotter than the climate of today.  And consistent with many of Steffen et al.’s arguments, it was about 4C hotter rather than a mere 2C, likely due to the range of carbon cycle and ice-albedo feedbacks they describe.  But such warmth was not uniform – globally warmer temperatures of 4C manifest as far hotter temperatures in some parts of the world and only slightly warmer temperatures elsewhere. Pollen and microbial molecular fossils from the North Sea, for example, indicate that Northern Europe experienced sub-tropical climates.

But what were the impacts of this warmth?  What is a 4C warmer world like?  To understand that, we also need to understand the other ways in which the Miocene world differed from ours, not just due to carbon dioxide concentrations but also the ongoing movement of the continents and the continuing evolution of life.  In both respects, the Miocene was broadly similar to today.  The continents were in similar positions, and the geography of the Miocene is one we would recognise. But there were subtle differences, including the ongoing uplift of the Himalayas and the yet-to-be-closed gateway between North and South America, and these subtle differences could have had major impacts on Asian climate and the North Atlantic circulation, respectively.

Similarly, the major animal groups had evolved by this point, and mammals had firmly established their dominance in a world separated by 50 million years from the dinosaurs.  Remnant groups from earlier times (hell pigs!) still terrorised the landscape, but many of the groups were the same or closely related to those we would recognise today.  And although hominins would not appear until the end of the Miocene, the apes had become well established, represented by as many as a 100 species. In the oceans, the differences were perhaps more apparent, the seas thriving with the greatest diversity of cetaceans in the history of our planet and associated with them the gigantic macro-predators such as Charcharadon megalodon (The MegTM).

Image result for Miocene fauna and flora

Smithsonian mural showing Miocene Fauna and landscape.

But it is the plants that exhibit the most pronounced differences between modern and Miocene life. Grasses had only recent proliferated across the planet at the time of the MMCO, and the C4 plants had yet to expand to their current dominance. And in this regard, the long-term evolution of Earth’s climate likely played a crucial role.  There are about 8100 species of C4 plants (although this comprises only 3% of the plant species known to us) and most of these are grasses with other notable species being maize and sugar cane. They are distinguished from the dominant C3 plants, which comprise almost all other species, by virtue of their carbon dioxide assimilation biochemistry (the Hatch-Slack mechanism) and their leaf cellular physiology (the Kranz leaf anatomy).  It is a collective package that is exceptionally well adapted to low carbon dioxide conditions, and their global expansion about 7 million years ago was almost certainly related to the long-term decline in carbon dioxide from the high levels of the Middle Miocene. Although C4 plants only represent a small proportion of modern plant species, the Miocene world, bereft of them, would have looked far different than today – lacking nearly half of our modern grass species and by extension clear analogues to the vast African savannahs.

Aside from these, the most profound differences between the Miocene world and that of today would have been the direct impacts of higher global temperatures.  There is strong evidence that the Greenland ice sheet was far reduced in size compared to that of today, and its extent and even whether or not it was a persistent ice sheet or an ephemeral one remains the subject of debate. Similarly, West Antarctica was likely devoid of permanent ice, and the East Antarctic Ice Sheet was probably smaller – perhaps far smaller – than it is today.  And collectively, these smaller ice sheets were associated with a sea level that was about 40 m higher than that of today.

The hot Miocene world would have been different in other ways, including the hydrological cycle.  Although less studied than for other ancient intervals, it is almost certain that elevated warmth – and markedly smaller equator-to-pole temperature differences – would have impacted the global distribution of water.  More water was evidently exported to the high latitudes, resulting in a warmer and vegetated Antarctica where the ice had retreated. It was also likely associated with far more extreme rainfall events, with the hot air able to hold greater quantities of water.  More work is needed, but it is tempting to imagine the impact of these hot temperatures and extreme rainfall events.  They would have eroded the soil and flushed nutrients to the sea, perhaps bringing about the spread of anoxic dead zones, similar to the Oceanic Anoxic Events of the Mesozoic or the dead zones of modern oceans caused by agricultural run-off. Indeed, the Miocene is characterised by the deposition of some very organic-rich rocks, including the North Pacific Monterey Formation, speaking to the occurrence of reduced oxygen levels in parts of these ancient oceans.


It is unclear if our ambitions to limit global warming to 2C by the end of this century really have put us on a trajectory for 4C. It is unclear if we are destined to return to the Miocene.

But if so, the Miocene world is one both similar to but markedly distinct from our own – a world of hotter temperatures, extremes of climate, fewer grasslands, Antarctic vegetation, Arctic forests and far higher sea levels. Crucially, it is not the world for which our current society, its roads, cities, power plants, dams, borders, farmlands and treaties, has been designed.

Moreover, the MMCO Earth is a world that slowly evolved from an even warmer one over millions of years*; and that then evolved over further millions of years to the one in which we now inhabit. It is not a world that formed in a hundred or even a thousand years.  And that leaves us three final lessons from the past.  First, we do not know how the life of this planet, from coral reefs to the great savannahs, will respond to such geologically rapid change.  Second, we do not know how we will respond to such rapid change; if we must adapt, we must learn how to do so creatively, flexibly and equitably.  And third, it is probably not too late to prevent such a future from materialising, but even if it is, we still must act to slow down that rate of change to which we must adapt.

And we still must act to ensure that our future world is only 4C hotter and analogous to the Miocene; if we fail to act, the world will be even hotter, and we will have to extend our geological search 10s of millions of years further into the past, back to the Eocene, to find an even hotter and extreme analogue for our future Hothouse World.


*The final jump into the MMCO appears to have been somewhat more sudden, but still spanned around two-hundred thousand years.  A fast event geologically but not on the timescales of human history.

Why we must Bridge the Gap

In 2015, Bristol was the European Green Capital.  Bristol had and still has bold ambitions to be an environmentally thriving city, rich in wildlife and green spaces and committed to net zero carbon emissions by 2050.  But this is a journey that requires the commitment of all, and as such, I was asked to help kick off the Green Capital year and frame its ambitions.  This is what I wrote in January 2015; I’d write something similar today, but no less ambitious and no less determined.

Why we must Bridge the Gap

Environmental experts describe the gap between our green intentions and our green actions as “the green gap”. We asked Bristol-based climate scientist, Professor Richard Pancost, to explain the scale of the problem, and why we need to take action now to tackle climate change.

Photo: Martina Ebel

Much of the climate change of the past century has been caused by our burning of fossil fuels. And without a change in that fossil fuel use, continued climate change in the next century could have devastating impacts on our society.

It is likely to bring increased risk and hazards associated with extreme weather events. Refugee crises could be caused by rising sea levels or droughts that make some nations uninhabitable. And climate change will also make our world a more uncertain place to live, whether that be uncertainty in future rainfall patterns, the magnitude of sea level rise or the response of global fisheries to ocean acidification.

This uncertainty is particularly problematic because it makes it so much harder for industry or nations to plan and thrive.

Or to grapple with the other great challenge facing humanity – securing food, water and energy for 7 billion people (and growing).

Because of this, most nations have agreed that global warming should be held below 2°C. [Note: And of course, this was agreed at COP21 in the Paris Climate Change Agreement.]

Interconnected world

These climatic and environmental impacts will be felt at home in the South West of England.

We live in an interconnected world, such that drought in North America will raise the price of our food. The effects of ocean acidification on marine ecosystems and UK fisheries remain worryingly uncertain. The floods of last winter could have been a warning of life in a hotter and wetter world; moreover, it will only become harder to protect our lowlands from not only flooding but also salt water incursions as sea level rises.

JAN 7, 2014: An unknown jogger running along the sea wall between in Dawlish, South West England
Photo: Paul J Martin /

Climate change affects us all – globally, nationally and locally in Bristol, the 2015 European Green Capital. Preventing it requires reductions in emissions over the next decade. And it then requires putting an end to all fossil fuel emissions in the decades to come.

Recent discussions in Lima and likely those in Paris at the end of this year, focused on how we reduce emissions globally. But in order to end all fossil fuel emissions in future, we need to put in place an international treaty. And this is the most difficult but necessary action to achieve.

Carbon lifecycle

Carbon dioxide has a lifetime in the atmosphere of 1000s of years, such that slower emissions will only delay climate change.

That can be useful – if we must adapt to a changing world, having more time to do so will be beneficial. However, it is absolutely clear that emissions must stop if we are to meet our target of 2°C.  In fact, according to most climate models as well as the geological history of climate, emissions must stop if we are to keep total warming below 5°C.

[Or we must spend a lot of money removing that CO2 from the atmosphere later.]

In short, we cannot use the majority of our coal, gas and petroleum assets for energy. They must stay buried.

Can we ‘geoengineer’ our way to alternative solution?  Not according to recent research. Last November, a Royal Society Meeting showcased the results of three UK Research Council Funded investigations of geoengineering feasibility and consequences.  They collectively illustrated that geoengineering a response to climate change was at best complicated and at worst a recipe for disaster and widespread global conflict.

The most prominent geoengineering solution is to offset the greenhouse gas induced rise in global temperatures via the injection of stratospheric particles that reflect some of the solar energy arriving at Earth.  However, on the most basic level, a world with elevated CO2 levels and reflective particles in the atmosphere is not the same as a world with 280 ppm of CO2 and a pristine atmosphere.

To achieve the same average global temperature, some regions will be cooler and others warmer.  Rainfall patterns will differ: regional patterns of flood and drought will differ. Even if it could be done, who are the arbitrators of a geoengineered world?  The potential for conflict is profound.

In short, the geoengineering our climate is neither a feasible nor a just option.

And again, the conclusion is that we cannot use most of our fossil fuels.

Ratcliffe-on-Soar is one of the most efficient coal fired power stations in the UK, and removes 92% of sulphur dioxide from flue gas before it is released into the atmosphere.  But it does not remove the CO2
Photo: Mark Burrows/ Shutterstock

Future generations

One might argue that we can adapt to climate change: why risk our economy now when we can adapt to the consequences of climate change later?

Many assessments suggest that this is not the best economic approach, but I understand the gamble: be cautious with a fragile economy now and deal with consequences later.   This argument, however, ignores the vast inequity associated with climate change.

It is the future generations that will bear the cost of our inaction.  Moreover, it appears that the most vulnerable to climate change are the poorest – and those who consume the least fossil fuels.

Those of us who burn are not those who will pay.

Arguably then, we in the UK have a particular obligation to the poor of the world and of our own country, as well as to our children and grandchildren, to soon cease the use of our fossil fuels.

Energy is at the foundation of modern society and it has been the basis for magnificent human achievement over the past 150 years, but it is clear that obtaining energy by burning fossil fuels is warming our planet and acidifying our oceans.   The consequences for our climate, from extreme weather events to rising sea levels, is profound; even more worrying are the catastrophic risks that climate change poses for the food and water resources on which society depends. It is now time for us to mature beyond the 19th and 20th century fossil-fuel derived energy to a renewable energy system of the 21st century that is sustainable for us and our planet.

We must bridge the gap.

[This was written in Jan 2015, before the Paris Agreement was signed, before Brexit, before Trump, before plummeting costs of offshore wind, before reconsideration of nuclear energy as financially viable, before so much… But one thing is very clear – we have made a lot of progress but not enough and CO2 emissions have not only not fallen but they continue to rise.]