sea level rise – Cabot Institute for the Environment blog

Arctic Ocean: why winter sea ice has stalled, and what it means for the rest of the world

Posted on October 27, 2020April 16, 2023 by janet.crompton

Ice floes in the Laptev Sea, Russia.
Olenyok/Shutterstock

Arctic sea ice plays a crucial role in the Earth’s energy balance. It is covered for most of the year by snow, which is the brightest natural surface on the planet, reflecting about 80% of the solar radiation that hits it back out to space.

Meanwhile, the ocean it floats on is the darkest natural surface on the planet, absorbing 90% of incident solar radiation. For that reason, changes in sea ice cover have a big impact on how much sunlight the planet absorbs, and how fast it warms up.

Each year a thin layer of the Arctic Ocean freezes over, forming sea ice. In spring and summer this melts back again, but some of the sea ice survives through the summer and is known as multi-year ice. It’s thicker and more resilient than the sea ice that forms and melts each year, but as the Arctic climate warms – at a rate more than twice that of the rest of the world – this multi-year ice is under threat.

In the last 40 years, multi-year ice has shrunk by about half. At some time in the next few decades, scientists expect the world will see an ice-free Arctic Ocean throughout the summer, with worrying consequences for the rest of the climate system. That prospect got much closer in 2020, due in part to the exceptional summer heatwave that roiled the Russian Arctic.

Shutting down the sea ice factory

The oceans have a large thermal capacity, which means they can store huge amounts of heat. In fact, the top metre of the oceans has about the same thermal capacity as the whole of the atmosphere. Many of us have experienced a balmy afternoon in autumn by the coast even though the air temperature inland is only a few degrees above freezing. That’s because the oceans accumulate heat slowly over the summer, releasing it equally slowly during winter.

So it is with the Laptev Sea, lying north of the Siberian coast. This part of the Arctic Ocean is usually a factory for new sea ice in autumn and winter as air temperatures dip below zero and surface water starts to freeze. That new ice is carried westward by persistent offshore winds in a kind of conveyor belt.

A map of the Laptev Sea with an inset world map.

The Laptev Sea lies off the coast of northern Siberia.
NormanEinstein/Wikipedia, CC BY-SA

This process is powered by the formation of polynyas: areas of open water surrounded by sea ice. Polynas act as engines of new sea ice production by exchanging heat with the colder atmosphere, causing the water to freeze. But if there is no sea ice to start with, the polynya cannot form and the whole process shuts down.

Sea ice in the Laptev Sea reached a record low in 2020, with no new ice through October, later than any previous year in the satellite record. The exceptional summer heatwave across Siberia will have resulted in heat accumulating in the adjacent ocean, which is now delaying the regrowth of sea ice.

Laptev Sea (#Arctic) ice watch —> 😅 pic.twitter.com/O0q6M74Xs4

— Zack Labe (@ZLabe) October 14, 2020

In the 1980s, there was as much as 600,000 square kilometres of multi-year ice covering around two thirds of the Laptev Sea. In 2020, it has been ice-free for months with no multi-year ice left at all. The whole Arctic Ocean is heading for ice-free conditions in the future, defined as less than one million square kilometres of ice cover. That’s down from about 8 million square kilometres just 40 years ago. This year’s new record delay in ice formation in the Laptev Sea takes it a step closer.

A rapidly changing Arctic is a global cause for concern. Thawing permafrost releases methane, a greenhouse gas that is about 84 times more potent than CO₂ when measured over 20 years.

Meanwhile, the Greenland Ice Sheet, the largest ice mass in the northern hemisphere, is currently contributing more to sea levels rising than any other source, and has enough ice in it to raise global sea level by 7.4 metres. And if the machinations of a warming Arctic still seem remote, evidence suggests that even the weather across much of the northern hemisphere is heavily influenced by what happens in the rapidly changing roof of the world.

————————————-

This blog is written by Cabot Institute member Jonathan Bamber, Professor of Physical Geography, University of Bristol. This article is republished from The Conversation under a Creative Commons license. Read the original article.

Jonathan Bamber

Real world risks and extremes

Posted on April 20, 2016April 6, 2023 by janet.crompton

Few locations in London are more appropriate to discuss risk and extremes than the Shard in London. The daring skyscraper, completed in 2012, was among the first high-rise buildings to be designed in the aftermath of 9/11 – terrorism risk mitigation has been a major challenge for the structural engineers working on the project.

The Shard, London

On the 8 April 2016, the Mathematics Institute of the University of Warwick, in partnership with the London Mathematical Laboratory and the Institute of Physics, held the Real World Risks and Extremes meeting at the WBS campus at the Shard.

The invited speakers included Dr Gordon Woo (Risk Management Solutions), Professor Willy Aspinall (University of Bristol Cabot Institute and Aspinall & Associates), Professor Jean-Philippe Bouchaud (École Polytechnique and Capital Fund Management) and Professor Giulia Iori (City University London), as well as the writer Mark Buchanan (author and columnist for Nature and Bloomberg), who chaired the final panel discussion. The objective of the meeting was to foster interdisciplinary discussion on the methodology of extreme risk assessment and management, and this common theme was tackled in the talks from very different angles.

From the left: Professor Aspinall, Dr Woo, Professor Bouchaud and Professor Iori.

The day started with a thought-provoking speech by Dr Woo, who called for a new approach in the treatment of historical extreme events: rather than treating them as the only source of data, we ought to be performing some counterfactual analysis as well. Besides what we have experienced, what could have happened? Asking these type of questions, according to Dr Woo, would improve the robustness of risk assessments, after all, what happened was just one of many possible outcomes. Thinking about what could have been would help us to better prepare for the future.

Professor Aspinall followed with a talk about the use of expert judgement to quantify the uncertainty in mathematical models of natural processes. This is especially important when policy decisions are being taken based on these models, as in the case of climate change. The methodology was used to evaluate the uncertainty in the correlations between the different drivers of sea-level rise, discovering that its extreme values could be higher than previously predicted.

The talks by Professor Bouchaud and Professor Iori focused on the use of statistical mechanics-based and agent-based models to understand complex systems such as economics at a country scale or the global banking system. In particular, they both focused on the possibility of identifying the set of variables which govern crises in these systems. This is especially important for high-dimensional systems, as while there are many variables at play, generally only few of them can shift the system state from stable to unstable.

The Cabot Institute’s Dr Max Werner (Lecturer in Natural Hazards and Risks in the School of Earth Sciences, University of Bristol) was one of the organisers of the event:

“Our main objective for the meeting was to stimulate cross-disciplinary discussion about how to improve uncertainty assessments of risks to society, especially given complex interactions and correlations among the many components of a natural or socio-economic system. The speakers represented such different fields of the risk sciences and industries, and yet their common ground became very clear during the panel discussion chaired by Mark Buchanan: don’t place your trust blindly in quantitative models or in past observations – use expert judgement of what might happen, supported by insights from qualitative models of complex systems and an analysis of near-misses. For most scientists, including myself, that are engaged in quantitative modelling of past and future observations, this consensus was an important lesson in how our science should contribute to policy and decision making.”

What I found most interesting about the meeting was the diversity of the point of views of the speakers and the participants. From mathematics to philosophy, and from engineering to finance, all the way through natural and actuarial sciences, there is a lot of exciting research being done on the risk posed by extreme events and complex systems. How to assess these risks, how to communicate them in an effective way, how to manage them and how to turn them into opportunities are challenges that we as academics need to explore, if we want to help our societies to thrive and flourish.

—————————————-

This blog is written by Cabot Institute member Giulio Galvan from the School of Engineering at the University of Bristol. Giulio’s research looks at the vulnerability and resilience of infrastructure networks.

Uncertain World: Understanding past and future sea level rise

Posted on September 25, 2015April 13, 2023 by janet.crompton

A recent study published in Science Advances suggests that if we burn all attainable fossil fuels (up to 12,000 gigatonnes of carbon), the Antarctic ice sheet is likely to become almost ice-free within 10,000 years. However, what does this mean in terms of sea level rise? To illustrate this we have designed an infographic which shows the likely extent of sea level rise under a range of different scenarios. We have chosen to use the Wills Memorial Building as an example and assume, for the purpose of this exercise, that it resides at sea level (Figure 1).

1) Sea level rise over the next century:

The most recent report by the Intergovernmental Panel on Climate Change (IPCC AR5) indicates that if we continue emitting greenhouse gases under business-as-usual scenarios (i.e. no reduction in emissions), it is likely that global mean sea level will rise between 0.52 and 0.98 m by the year 2100. If we are more optimistic, and we allow greenhouse gas emissions to peak in 2040 and decline thereafter, the range of likely global mean sea level rise is lower, but not insignificant (0.36 to 0.71 m). Both of these estimates are illustrated below and shown alongside the Wills Memorial Building.

Figure 1: An infographic showing the approximate height of sea level rise depending upon a range of different scenarios (Fretwell et al., 2013; IPCC AR5). This assumes the Wills Memorial Building resides at sea level

Although ~30 to 100 cm of sea level rise may seem insignificant, it is worth considering what this means for other regions. For example, “…since 80% of its 1,200 islands are no more than 1m above sea level“, sea level rise has the potential to impact up to 360,000 citizens and lead to widespread migration.

The reason that scientists provide a range of values for sea level rise is that the climate system is very complex. For example, under low emissions scenarios, there is expected to be an increase in moisture content around Antarctica, leading to increased snowfall along the ice sheet margins. However, under higher emissions scenarios, ice sheet discharge overcompensates for an increase in snowfall, leading to a net sea level rise.

2) Sea level rise over 10,000 years:

The variations between these two emission scenarios are less important when looking over longer timescales. Winklemann et al. (2015) have recently simulated changes in the Antarctic ice sheet over the next 10,000 years using a combination of climate and ice sheet models. From these experiments, it is clear that ice loss is driven by two key feedback mechanisms. The first begins with warming and subsequent retreat of the grounding line (Figure 2). The grounding line is the region where ice transitions from a grounded ice sheet to a freely-floating ice shelf. When the grounding line retreats to a point where the ice sheet falls below sea level, then ice sheets can become unstable.

Figure 2: A schematic of an ice sheet showing the position of the grounding line (bottom right). Image credit: www.AntarcticGlaciers.org.

Winklemann et al. (2015) argue that the West Antarctic Ice Sheet (WAIS) becomes unstable when cumulative carbon emissions reach 600 to 800 gigatonnes of carbon (this is equivalent to a 2 degree rise in temperature by 2100). If this part of the Antarctic Ice Sheet becomes unstable, we can expect ~4 m of global sea level rise (Figure 1).Once a specific temperature is reached, a second feedback then kicks in. This destabilises the rest of the Antarctic ice sheet via the so-called surface elevation feedback. On the timescale of 10,000 years this will eventually lead to an almost ice-free Antarctica (Winklemann et al. 2015).

Figure 3: Predicted ice-sheet loss on Antarctica under different carbon emission pathways (Winkelmann et al., 2015: Science Advances).

3) Sea level rise over millions of years:

Palaeoclimatologists can provide insights into the fate of ice sheets over longer timescales. For example, the last time Antarctica was ice-free was during the early Eocene (~56 to 48 million years ago). During this interval, carbon dioxide concentrations were much higher and allowed the development of lush, tropical rainforests along the ancient coastline (Figure 4). Gradual cooling over millions of years eventually culminated in the sudden and rapid establishment of ice-sheets on Antarctica. This occurred ~34 million years ago and was likely driven by a reduction in carbon dioxide (and perhaps some other feedback mechanisms). Although Antarctica has fluctuated in size since then, it has never been completely ice-free since the Eocene. However, under rising carbon emissions, we are rapidly returning to a world that has not been seen for at least 34 million years.

Figure 4: This may be what the East Antarctic coastline looked like during the early Eocene (Pross et al., 2012).

Why we must Bridge the Gap

Posted on January 28, 2015April 14, 2023 by janet.crompton

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. 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.

Flooding on Whiteladies Road, Bristol. Image credit Jim Freer

These climatic and environmental impacts will be felt 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. The proposed Hinkley Point nuclear power station will have an installation, operating and decommissioning lifetime of over 100 years; what added risks will it face from the combination of more severe weather, storm surges and rising sea level? Climate change affects us all – globally, nationally and locally in the 2015 European Green Capital.

That requires reductions in emissions over the next decade. And it then requires cessation of all fossil fuel emissions in the subsequent decades. The former has been the subject of most negotiations, including the recent discussions in Lima and likely those in Paris at the end of this year. The latter has yet to be addressed by any international treaty. And that is of deep concern because it is the cessation of all fossil fuel emissions that is most difficult but most necessary to achieve. 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.

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 deus ex machina of 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.

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 blog is by Prof Rich Pancost, Director of the Cabot Institute at the University of Bristol.

Prof Rich Pancost

This blog has been reproduced with permission from the Bristol 2015 news page.

The uncertain world

Posted on September 3, 2014April 14, 2023 by janet.crompton

J.G Ballard’s The Drowned World
taken from fantasticalandrewfox.com

Over the next 18 months, in collaboration with Bristol Green Capital 2015 artists, civic leaders and innovative thinkers, the Cabot Institute will be participating in a series of activities in which we examine how human actions are making our planet a much more uncertain place to live.

Fifty years ago, between 1962 and 1966, J. G. Ballard wrote a trio of seminal environmental disaster novels: The Drowned World, The Burning World and The Crystal World. These novels remain signposts to our future, the challenges we might face and the way people respond to rapid and unexpected change to their environment. In that spirit and coinciding with the Bristol Green Capital 2015, we introduce The Uncertain World, a world in which profound uncertainty becomes as much of a challenge to society as warming and rising sea levels.

For the past twenty years, the University of Bristol has been exploring how to better understand, mitigate and live with environmental uncertainty, with the Cabot Institute serving as the focus for that effort since its founding in 2010. Uncertainty is the oft-forgotten but arguably most challenging aspect of mankind’s centuries-long impact on the environment. We live our lives informed by the power of experience: our own as well as the collective experience of our families, communities and wider society. When my father started dairy farming he sought advice from my mother’s grandfather, our neighbours, and the grizzled veterans at the Middlefield auction house. Experience helps us make intelligent decisions, plan strategically and anticipate challenges.

Similarly, our weather projections, water management and hazard planning are also based on experience: tens to hundreds of years of observation inform our predictions of future floods, drought, hurricanes and heat waves. These records – this experience – can help us make sensible decisions about where to live, build and farm.

Now, however, we are changing our environment and our climate, such that the lessons of the past have less relevance to the planning of our future. In fact, many aspects of environmental change are unprecedented not only in human experience but in Earth history. As we change our climate, the great wealth of knowledge generated from human experience is losing capital every day.

The Uncertain World is not one of which we have no knowledge – we have high confidence that temperatures and sea level will rise, although there is uncertainty in the magnitude and speed of change. Nor should we view The Uncertain World with existential fear – we know that warm worlds have existed in the past. These were not inhospitable and most evidence from the past suggests that a climate ‘apocalypse’ resulting in an uninhabitable planet is unlikely.

Nonetheless, increasing uncertainty arising from human-induced changes to our global environment should cause deep concern. Crucial details of our climate remain difficult to predict, and it undermines our ability to plan for our future. We do not know whether many regions of the world will become wetter or dryer. This uncertainty propagates and multiplies through complex systems: how do we make sensible predictions of coastal flood risk when there is uncertainty in sea level rise estimates, rainfall patterns and the global warming that will impact both? We can make predictions even in such complex systems, but the predictions will inevitably come with a degree of uncertainty, a probabilistic prediction. How do we apply such predictions to decision making? Where can we build new homes, where do we build flood defences to protect existing ones, and where do we abandon land to the sea?

Perhaps most worrying, the consequences of these rapid changes on biological and chemical systems, and the people dependent upon them, are very poorly understood. For example, the synergistic impact of warmer temperatures, more acidic waters, and more silt-choked coastal waters on coral reefs and other marine ecosystems is very difficult to predict. This is particularly concerning given that more than 2.6 billion people depend on the oceans as their primary source of protein. Similarly, warming of Arctic permafrost could promote the growth of CO2-sequestering plants or the release of warming-accelerating methane – or both. Warm worlds with very high levels of carbon dioxide did exist in the past and these do provide some insight into the response of the Earth system, but we are accelerating into this new world at a rate that is unprecedented in Earth history, creating additional layers of uncertainty.

During late 2014 and 2015, the Cabot Institute will host a variety of events and collaborate with a variety of partners across Bristol and beyond to explore this Uncertain World and how we can live in it. How do we better explain uncertainty and what are the ‘logical’ decisions to make when faced with uncertainty? One of our first events will explore how uncertainty in climate change predictions should motivate us to action: the more uncertain our predictions the more we should employ mitigation rather than adaptation strategies. Future events will explore how past lessons from Earth history help us better understand potential future scenarios; how future scenario planning can inform the decisions we make today; and most importantly, how we build the necessary flexibility into social structures to thrive in this Uncertain World.

This blog is by Prof Rich Pancost, Director of the Cabot Institute at the University of Bristol.

Prof Rich Pancost

Do not make policy during the middle of a flood crisis

Posted on March 14, 2014April 19, 2023 by janet.crompton

Across the country, we have seen our neighbours’ homes and farms devastated by the floods. We understand their anger and frustration. We understand their demands for swift action.

What they have been given is political gamesmanship. Blame shifting from party to party, minister to minister, late responses, dramatic reversals of opinion. It reached its well-publicised nadir this past weekend, with Eric Pickles’ appearance on the Andrew Marr show:

‘I apologise unreservedly and I’m really sorry that we took the advice; we thought we were dealing with experts.’

Throwing your own government experts to the wolves is not an apology.

This political vitriol, at least with respect to the Somerset Levels, all appears to come down to a relatively simple question – should we have been dredging?

This is not a simple question.

It is an incredibly complex question, in the Somerset Levels and elsewhere, and this simplistic discussion does the people of those communities a great disservice.

Image by Juni

But more fundamentally, this is not the time to be deciding long-term flood mitigation strategy. In times of disaster, you do disaster management. Later, you learn the lessons from that disaster. And finally, informed by evidence and motivated by what has happened, you set policy. And that, to me, is the most frustrating aspect of the current political debate. In an effort to out-manoeuvre one another, our leaders are making promises to enact policy for which the benefits appear dubious.

So, what are some of the issues, both for Somerset and in general?

First, the reason the rivers are flooding is primarily the exceptional rainfall – January was the wettest winter month in almost 250 years. This rain occurred after a fairly damp period, so that the soil moisture content was already high. However, these issues are exacerbated by how we have changed our floodplains, with both agricultural and urban development reducing water storage capacity.

Second, as the 2013-2014 flooding crisis has illustrated, much of our nation is flood-prone; however, those floods come in a variety of forms and have a range of exacerbating causes – some have been due to coastal storm surges, some due to flash floods caused by rapid flow from poorly managed lands and some due to sustained rain and soil saturation. We have a wet and volatile climate, 11,073 miles of coastline and little geographical room to manoeuvre on our small island. Our solutions have to consider all of these issues, and they must recognise that any change in a river catchment will affect our neighbours downstream.

Flooding on West Moor, Somerset Levels
Image by Nigel Mykura

Third, returning to the specific challenge of the Somerset Levels, it is unclear what benefit dredging will have. The Somerset Levels sit near sea level, such that the river to sea gradient is very shallow. Thus, rivers will only drain during low tide even if they are dredged. And widening the channels will actually allow more of the tide to enter. Some have argued that in the past, dredging was more common and flooding apparently less so. However, this winter has seen far more rain and our land is being used in very different ways: the memories of three decades ago are not entirely relevant.

Fourth, where dredging is done, it is being made more costly and challenging by land use practices elsewhere in the catchment. The rivers are filling with sediment that has eroded from intensively farmed land in the headwaters of the catchments and from the levels themselves. Practices that have greatly accelerated erosion include: heavy machinery operations in wet fields; placement of gates at the bottom of hillslopes so that sediment eroded from the field is very efficiently transported to impermeable road surfaces, and thence to streams downslope; cultivation of arable crops on overly steep slopes (increasing the efficiency of sediment transport from land to stream); overwintering of livestock on steep slopes; and excessive stocking densities on land vulnerable to erosion.

Image by Nicholas Howden

Nutrient enrichment from livestock waste and artificial fertilisers (when used in excess of crop requirements) also contribute to the dredging problem. The nutrient loading often exceeds the system’s recycling capacity, such that nutrients flow into ditches and waterways, stimulating growth of aquatic plants that can readily clog up the minor ditches and waterways. With less space to dissipate water within the network, it is forced into the main channel. In other words, some of these floods are a subsidised cost of agriculture – and by extension the low costs we demand of our UK-produced food.

And finally, if we are going to consider long-term planning, we must consider climate change impacts. Flooding will become worse due to sea level rise, which has already risen by about 12cm in the last 100 years, with a further 11-16cm of sea level rise projected by 2030. It is less clear how climate change will affect the intensity and frequency of these particularly intense rainfall events. Although almost all projections indicate that dry areas will become dryer and wet areas will become wetter, predictions for specific geographical regions are highly uncertain. And our historical records are not long enough to unravel long-term trends in the frequency of uncommon but high impact weather events. This should not be reassuring – it is another major element of uncertainty in an already complex problem.

As challenging as these issues are, they are not intractable. The solutions will involve stronger planning control and scientifically informed planning decisions (including allowing some areas to flood), a reconsideration of some intensive farming practices, some dredging in key areas, some controlled flooding in others, and better disaster management strategy for when the inevitable flooding does occur. But now is not the time to resolve such a complicated knot of complex issues. It is certainly not the time to offer false promises or miracle cures.

Now is the time to help our neighbours in distress, listen to their stories, and remember them when the floodwaters recede. And then we should let our experts get on with their jobs.
—
This blog is co-written by Professor Paul Bates, Professor Penny Johnes (Geographical Sciences), Professor Rich Pancost (Chemistry) and Professor Thorsten Wagener (Engineering), all of whom are senior members of the Cabot Institute at the University of Bristol.

This blog post was first published in the Guardian on 12/02/2014, titled Flood crisis: Dredging is a simplistic response to a complex problem.

If you have any media queries relating to this blog, please contact Paul Bates or Rich Pancost (contact details in links above).

Prof Paul Bates, Head of
Geographical Sciences

Prof Rich Pancost, Director of the
Cabot Institute

Climate lessons from the past: Are we already committed to a warmer and wetter planet?

Posted on February 17, 2014April 19, 2023 by janet.crompton

Last September, the Cabot Institute and the University of Bristol hosted the 2nd International Workshop on Pliocene Climate. Following on from that, we have just released a short video describing what the Pliocene is and its relevance for understanding climate change.

The Pliocene is a geological time interval that occurred from 5.3 to 2.6 million years ago. This interval of Earth history is interesting for many reasons, but one of the most profound is that the Earth’s atmosphere apparently contained elevated concentrations of carbon dioxide – in fact, our best estimates suggest concentrations were about 300 to 400 ppm, which is much higher than concentrations of 100 years ago but lower than those of today after a century of intensive fossil fuel combustion.

Image by NASA

Consequently, the Pliocene could provide valuable insight into the type of planet we are creating via global warming. Our video release happens to coincide with pronounced flooding across the UK and focussed attention on our weather and climate. There is little doubt that increased carbon dioxide concentrations will cause global warming; instead, the key questions are: how much warming will there be and what are the consequences of that warming? One way to study that is to examine previous intervals of Earth history also characterised by high carbon dioxide concentrations. The comparisons are not perfect, of course; for example, during the Pliocene the continents were in roughly but not exactly the same positions that they are in today. But it can serve as another piece of the puzzle in predicting future climate.

One of the key lessons from Earth history is climate sensitivity. Climate sensitivity can be expressed in various ways, but in its simplest sense it is a measure of how much warmer the Earth becomes for a given doubling of atmospheric carbon dioxide concentrations. This is well known for the Pleistocene, and especially the past 800,000 years of Earth history, an interval with detailed temperature reconstructions and carbon dioxide records from ice core gas bubbles. During that time, and through multiple ice ages, climate sensitivity was about 2.5 to 3°C warming for a doubling of carbon dioxide, which is in the middle of the model-based range of predictions.

Ice core sampling.
Image by NASA ICE (Ice Core Vitals) [CC-BY-2.0]
Wikimedia Commons

Ice core records, however, extend back no more than a million years, and this time period is generally characterised by colder climates than those of today. If we want to explore climate sensitivity on a warmer planet, we must look further back into Earth history, to times such as the Pliocene. Reconstructing atmospheric carbon dioxide concentrations in the absence of ice cores is admittedly more challenging. Instead of directly measuring the concentration of carbon dioxide in gas bubbles, we must rely on indirect records – proxies. For example, carbon dioxide concentration influences the number of stomata on plant leaves, and this can be measured on ancient leaf fossils. Alternatively, there are a number of geochemical tools based on how carbon dioxide impacts the pH of seawater or how algae assimilate carbon dioxide during photosynthesis; these are recorded by the chemical composition of ancient fossils.

These estimates come with larger error bars, but they provide key insights into climate sensitivity on a warmer Earth. Recent research indicates a convergence of Pliocene carbon dioxide estimates from these various proxies and gives us more confidence in deriving climate sensitivity estimates. In particular, it appears that an increase of carbon dioxide from about 280 parts per million (the modern value before the industrial revolution) to about 400 parts per million in the Pliocene results in a 2°C warmer Earth. Accounting for other controls, this suggests a climate sensitivity of about 3°C, which confirms both the Pleistocene and model-based estimates.

It also suggests that we have yet to experience the full consequences of the greenhouse gases already added to the atmosphere.

So then, what was this much warmer world like? First of all, it was not an inhospitable planet – plants and animals thrived. This should not be a surprise; in fact, the Earth was much warmer even deeper into the past. The climate change we are inducing is a problem for humans and society, not our planet.

However, the Pliocene was a rather different world. For example – and importantly, given current events in the UK – these higher global temperatures were associated with a climate that was also wetter* than present. That provides important corroborating evidence for models that predict a warmer and wetter future.

Image by w:en:User:Ivan and licensed as GFDL

Perhaps most striking, sea level appears to have been between 10 to 40 metres higher than today, indicating that both the Greenland Ice Sheet and Antarctic Ice Sheet were markedly smaller. To put that into context, the Met Office has already commented on how flooding in the UK has been and will be exacerbated by sea level rise of 12 centimetres over the last 100 years and a further 5 to 7 centimetres by 2030.

We must be careful in how we extract climate lessons from the geological record, and that is particularly true when we consider ice sheet behaviour. One widely discussed concept is ice sheet hysteresis. This is a fancy way of saying that due to feedback mechanisms, it could be easier to build an ice sheet on Greenland or Antarctica than it is to melt one. If such hysteresis does stabilise our current ice sheets, then we should not assume a planet with 400 ppm of carbon dioxide will necessarily have sea level 20 metres higher than that of today. But if hysteresis is rather weak, then the question is not whether we will see massive sea level change but rather how long it will take (Note: It is likely to take centuries or millennia!).

Most importantly, the collective research into Earth history, including the Pliocene, reveals that Earth’s climate can change. It also reveals that climate does not just change randomly: it changes when forced in relatively well understood ways. One of these is the concentration of carbon dioxide in our atmosphere. And consequently, there is little doubt from Earth history that transforming fossil carbon into carbon dioxide – as we are doing today – will significantly impact the Earth’s climate system.

* See Brigham-Grette, J., Melles, M., Minyuk, P., Andreev, A., Tarasov, P., DeConto, R., Koenig, S., et al., 2013. Pliocene Warmth, Polar Amplification, and Stepped Pleistocene Cooling Recorded in NE Arctic Russia. Science 340 (6139), 1421-1427. doi: 10.1126/science.1233137 and Salzmann, U., Haywood, A.M., Lunt, D.J., 2009. The past is a guide to the future? Comparing Middle Pliocene vegetation with predicted biome distributions for the twenty-first century. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367 (1886), 189-204.

This blog is by Prof Rich Pancost, Director of the Cabot Institute. Rich will be giving a public lecture on how biogeochemical cycles have regulated the global climate system throughout Earth’s history on 25 February in Bristol. The event is free and open to all, do come along to learn more.

To learn more about the Pliocene – and palaeoclimate research, in general – you can watch Professor Gerald Haug’s public lecture, Climate and Societies, recorded at the Cabot Institute as part of the 2nd International Workshop on Pliocene Climate.

Prof Rich Pancost

The sinking Pacific – climate change and international aid in Tuvalu

Posted on March 25, 2013April 20, 2023 by janet.crompton

Sarah Hemstock (University of the South Pacific) came to visit the Cabot Institute on 20 March 2013 and presented the case study “Impacts of international aid on climate change adaptation in Tuvalu”. Here I sum up the main points raised by Sarah during her lecture. Please note all figures mentioned below are from Sarah’s talk.

Tuvalu

Climate change

Tuvalu is a microcosm for what is going on with climate change globally. There are issues with waste management, sea level rise, politics, energy, food production and others.

Tuvalu grows taro, a staple carbohydrate which is sensitive to saltwater. Due to rising sea levels, Tuvalu is affected by high tides called king tides. These tides can contaminate agricultural land with saltwater and thus the staple crop will not grow.

Flood defences have been built by aid agencies to try to stop sea level rise. Unfortunately they do not work as seawater bubbles up through the island at king tide, flooding the airport and villages. There is now no fresh water and villages are completely dependent on collecting rainwater.

International aid and the economy

Sarah began to explain why Tuvalu needs to move away from aid to become more self empowering. She started to list the facts. Globally, $140bn has been given to international aid between 1970 and 2010, it certainly is a lucrative business. There are four agencies who accept international aid in the Pacific. Three of these agencies have mandates for climate change, fisheries, GIS and mapping etc which prevents any market driven approach to getting aid. Another problem with these agencies is their size. For example, Secretariat of the Pacific Community (SPC) has grown from 300 employees at its inception to 3000 today. Large numbers of employees can see international aid going towards feeding these agencies rather than having a smaller administrative group and diverting the main bulk of funds to helping save the islands of the Pacific. It could be argued that these large companies provide jobs for people in the Pacific, but in reality, these jobs are not very likely to go to people from the small island states such as Tuvalu (for which the aid is supposed to be for), which are isolated and poor.

Tuvalu has a weak economy. There is a lack of exports but a lot of imports to people who are not native to the island and want a little something from home. 83 % of Tuvalu’s energy comes from oil and a shocking 50% of Tuvalu’s annual GDP comes from aid. People in Tuvalu are subsisting on less than $2 a day. However, because Tuvalu receives a substantial amount of ‘aid’ they are recognised as a middle income country, but this aid does not filter down to the people and in fact Tuvalu should be considered as a low income country.

Tuvalu spends $6m on policy development, although these policies rarely do anything and could be considered a waste of money which could be better used in the community. The amount of diesel used for electricity consumption has increased. However, petrol usage has decreased, mainly due to people going back to using traditional canoes as they are cheaper to run.

A desperate situation – a sinking community

Between 2004 and 2007, fossil fuel use increased by 21%. Sarah felt that this was because funders ignore policy. For example, a Japanese company gave Tuvalu three diesel energy generators. Tuvalu asked for generators that could run on coconut oil in line with environmental policy but due to cost, the donators could not provide these. Tuvalu couldn’t afford to run the diesel generators so Japan donates $2m of oil every year to run them making Tuvalu totally dependent on donations for its energy supply.

There is no market, no money and no tourist industry in Tuvalu so there is no way of generating money. It is an isolated island and boats to Fiji run every 5-6 weeks. When weather is bad, food, oil and supplies are not delivered.

Sarah explained how there is no joined up thinking with international aid and no long term plans after the aid has disappeared. An example of this is where water tanks were given to each home in Tuvalu and they were also made in Tuvalu. The problem with the design was that it has a sealed top which meant it could not be stacked. This meant it would have taken 25 years to get everyone a tank, as only six tanks would fit on each ship. The good news was that they managed to get a barge to ship them out, but it is this lack of foresight which hampers the success of aid activities.

Sarah also mentioned how 35% of aid goes straight back to the company who gave the money to pay for ‘technical assistance’ and admin fees. There are other fees which come out of international aid. In fact if aid was taken away from Tuvalu, it wouldn’t affect the people much as the aid hardly reaches them anyway.

Interestingly, the people of Tuvalu are extremely mentally resilient to the threat of climate change. When asked if they would move off the island if climate change flooded their islands, they were determined to stay on the island no matter what. When the question was framed in an economic sense, for example would they move off the island for work, they were more open to the idea of moving off the island. This is a difficult ethical argument. What right do we have to move the islanders to safety, to move them to a different country, culture and language when they do not want to go?

Climate change may be physically sinking the small low-lying islands of the Pacific, but it is the international aid agencies which are arguably sinking them beyond recovery. A drastic change is needed in the management and distribution of international aid in order to save these dying islands from the rest of the world’s actions.

Listen again to Sarah Hemstock’s Cabot Institute seminar.

This blog was written by Amanda Woodman-Hardy (@Enviro_Mand), Cabot Institute

Amanda Woodman-Hardy, Cabot Institute