Greenland is the largest island in the world and on it rests the largest ice mass in the Northern Hemisphere. If all that ice melted, the sea would rise by more than 7 metres.
But that’s not going to happen is it? Well not any time soon, but understanding how much of the ice sheet might melt over the coming century is a critical and urgent question that scientists are trying to tackle using sophisticated numerical models of how the ice sheet interacts with the rest of the climate system. The problem is that the models aren’t that good at reproducing recent observations and are limited by our poor knowledge of the detailed topography of the subglacial terrain and fjords, which the ice flows over and in to.
One way around this problem is to see how the ice sheet responded to changes in climate in the past and compare that with model projections for the future for similar changes in temperature. That is exactly what colleagues and I did in a new study now published in the journal Nature Communications.
We looked at the three largest glaciers in Greenland and used historical aerial photographs combined with measurements scientists had taken directly over the years, to reconstruct how the volume of these glaciers had changed over the period 1880 to 2012. The approach is founded on the idea that the past can help inform the future, not just in science but in all aspects of life. But just like other “classes” of history, the climate and the Earth system in future won’t be a carbon copy of the past. Nonetheless, if we figure out exactly how sensitive the ice sheet has been to temperature changes over the past century, that can provide a useful guide to how it will respond over the next century.
Greenland’s glaciers contain around 8% of the world’s fresh water. Jonathan Bamber, Author provided
We found that the three largest glaciers were responsible for 8.1mm of sea level rise, about 15% of the whole ice sheet’s contribution. Over the period of our study the sea globally has risen by around 20cm, about the height of an A5 booklet, and of that, about a finger’s width is entirely thanks to ice melting from those three Greenland glaciers.
Melting As Usual
So what does that tell us about the future behaviour of the ice sheet? In 2013, a modelling study by Faezeh Nick and colleagues also looked at the same “big three” glaciers (Jakobshavn Isbrae in the west of the island and Helheim and Kangerlussuaq in the east) and projected how they would respond in different future climate scenarios. The most extreme of these scenarios is called RCP8.5 and assumes that economic growth will continue unabated through the 21st century, resulting in a global mean warming of about 3.7˚C above today’s temperatures (about 4.8˚C above pre-industrial or since 1850).
This scenario has sometimes been referred to as Business As Usual (BAU) and there is an active debate among climate researchers regarding how plausible RCP8.5 is. It’s interesting to note, however, that, according to a recent study from a group of US scientists it may be the most appropriate scenario up to at least 2050. Because of something called polar amplification the Arctic will likely heat up by more than double the global average, with the climate models indicating around 8.3˚C warming over Greenland in the most extreme scenario, RCP8.5.
Despite this dramatic and terrifying hike in temperature Faezeh’s modelling study projected that the “big three” would contribute between 9 and 15 mm to sea level rise by 2100, only slightly more than what we obtained from a 1.5˚C warming over the 20th century. How can that be? Our conclusion is that the models are at fault, even including the latest and most sophisticated available which are being used to assess how the whole ice sheet will respond to the next century of climate change. These models appear to have a relatively weak link between climate change and ice melt, when our results suggest it is much stronger. Projections based on these models are therefore likely to under-predict how much the ice sheet will be affected. Other lines of evidence support this conclusion.
What does all of that mean? If we do continue along that very scary RCP8.5 trajectory of increasing greenhouse gas emissions, the Greenland ice sheet is very likely to start melting at rates that we haven’t seen for at least 130,000 years, with dire consequences for sea level and the many millions of people who live in low lying coastal zones.
What do Bristol residents really think about climate change? We know that Bristol has a reputation as a green city, but is it just ‘greenies’ at the centre of town who care? What kinds of policies would be acceptable or desirable? Are people aware of what the Council is planning to do?
Our team of eight researchers set out to all four corners of the city with clipboards , to find out what Bristol residents have to say. They approached people at bus stops, in leisure centres, at libraries and on the street to ask questions like:
What comes to mind when you think of climate change?
How does it make you feel?
Are you aware of any planned changes in the city in relation to climate change?
Are there any future changes you would or wouldn’t want to see?
The answers came in from 333 residents of all parts of the city in February and March 2020, and then a further 1343 residents took part in an online survey in June, which included an additional question about whether Covid-19 had shifted their views on climate change in any way.
Careful analysis of the responses revealed the following insights:
Bristol residents are concerned about climate change and would welcome City leadership and policy that enables them to take action. People want change, but they don’t necessarily have the will or indeed power to act as individuals.
The emotion of fear was widely identified but what this meant for action was mixed. In some cases it motivated change while in others it held back action.
Transport is the biggest area of concern talked about both before and during the Covid-19 lockdown.
Residents are willing to see radical change in the city, and are frustrated that the visible steps taken so far aren’t enough to address the climate emergency. with the lack of visible steps that have been taken so far.
Equality and fairness is important to Bristolians, including an expectation that all sectors should pull their weight and that the cost of adaptation to climate change should not be carried by, or lead to the exclusion of, those least able to pay.
Residents expect a high level of integrity from Bristol City Council.
This research coincides with the launch of Bristol’s One City Climate Strategy, a cross-sector approach to the climate emergency in Bristol. The promotion and communication of the One City Climate Strategy is a good opportunity for increasing understanding of the city’s plans, and involving residents in shaping what we do, and we hope that this research can inform that process. It is clear that people from across the city care about climate change, and are afraid and angry, but they want to see bold and consistent city wide leadership, and to know that the efforts they make to contribute to the change we need are part of a wider collective effort where everyone pulls their weight.
To find out more about what people said and the recommendations coming out of this research, you can download the full report.
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This blog is written by Cabot Institute member Dr Jack Nicholls and Emilia Melville. This blog was reposted with kind permission from Praxis Research.
Evidence that the Earth is warming at an alarming rate is indisputable, having almost doubled per decade since 1981 (relative to 1880-1981). In many countries, this warming has been accompanied by more frequent and severe heatwaves – prolonged periods of significantly above-average temperatures – especially during summer months.
Heat-health risks are not equally distributed. Cities face heightened risks due to the urban heat island (UHI) effect, where urban areas exhibit warmer temperatures than surrounding rural areas. This is primarily due to the concentration of dark, impervious surfaces. In the event of a heatwave, cities are therefore not only threatened by even warmer temperatures, but also by high population densities which creates greater exposure to such extreme heat.
UHIs have been observed and modelled across several of the UK’s largest cities. For example, in Birmingham an UHI intensity (the difference between urban and rural temperatures) of 9°C has been recorded. Some estimates for Manchester and London reach 10°C. However, little research has been conducted into the UK’s smaller cities, including Bristol, despite their rapidly growing populations.
Heat vulnerability
In the UK an ageing population implies that heat vulnerability will increase, especially in light of warming projections. Several other contributors to heat vulnerability are also well-established, including underlying health conditions and income. However, the relative influence of different factors is extremely context specific. What drives heat vulnerability in one city may play an insignificant role in another, making the development of tailored risk mitigation policies particularly difficult without location-specific research.
The adaptation of infrastructure to cope with extreme heat
The avoidance of heat-related deaths
Yet, the same report that outlines these goals also highlights an insufficient understanding of hotspots and heat risk in Bristol. This poses the question – how will Bristol achieve these targets without knowing where to target resources?
Bristol’s urban heat island
Considering the above, over the summer I worked on my MSc dissertation with two broad aims:
Quantify Bristol’s urban heat island
Map heat vulnerability across Bristol wards
Using a cloud-free Landsat image from a heatwave day in June 2018, I produced one of the first high-resolution maps of Bristol’s UHI (see below). The results were alarming, with several hotspots of 7-9°C in the central wards of Lawrence Hill, Easton and Southville. Maximum UHI intensity was almost 12°C, recorded at a warehouse in Avonmouth and Lawrence Weston. Though this magnitude may be amplified by the heatwave event, these findings still suggest Bristol exhibits an UHI similar to that of much larger cities including London, Birmingham and even Paris.
Image credit: Vicky Norton
Heat vulnerability in Bristol
Exploratory statistics revealed two principal determinants of an individual’s vulnerability to extreme heat in Bristol:
Their socioeconomic status
The combined effects of isolation, minority status and housing type.
These determinants were scored for each ward and compiled to create a heat vulnerability index (HVI). Even more concerning than Bristol’s surprising UHI intensity is that wards exhibiting the greatest heat vulnerability coincide with areas of greatest UHI intensity – Lawrence Hill and Easton (see below).
What’s also interesting about these findings is the composition of heat vulnerability in Bristol. Whilst socioeconomic status is a common determinant in many studies, the influential role of minority status and housing type appears particularly specific to Bristol. Unlike general UK projections, old age was also deemed an insignificant contributor to heat vulnerability in Bristol. Instead, the prevalence of a younger population suggests those under five years of age are of greater concern.
Image credit: Vicky Norton
Implications
But what do these findings mean for Bristol’s climate resilience endeavours? Firstly, they suggest Bristol’s UHI may be a much greater concern than previously thought, necessitating more immediate, effective mitigation efforts. Secondly, they reiterate the context specific nature of heat vulnerability and the importance of conducting location specific research. Considering UHI intensity and ward-level heat vulnerability, these findings provide a starting point for guiding adaptive and mitigative resource allocation. If Bristol is to achieve climate resilience by 2030, initial action may be best targeted towards areas most at risk – Lawrence Hill and Easton – and tailored to those most vulnerable.
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This blog is written by Vicky Norton, who has recently completed an MSc in Environmental Policy and Management run by Caboteer Dr Sean Fox.
Voi e-scooter parked across the pavement outside Victoria Rooms in Clifton. Image credit: Georgina de Courcy-Bower
At the end of October this year, the Swedish company Voi launched their e-scooters in Bristol as part of a pilot scheme. The government brought the scheme forward in the hope that e-scooters would ease demand for public transport and allow for social distancing during the Covid-19 pandemic. Earlier in the year, Marvin Rees said that he hoped e-scooters would help the city reduce congestion and air pollution. These are two key issues associated with a car-dominated transport system present in Bristol and many other cities around the world.
I have been investigating whether e-scooters could help Bristol to meet its sustainable transport targets. These include meeting net-zero emissions by 2030 and simultaneously reducing inequality within the city. However, between 2005 and 2017 the decrease in CO2 emissions in Bristol’s transport sector was only 9%. To reach net-zero by 2030, there will need to be an 88% decrease from the 2005 baseline.
E-scooters have been called a ‘last mile’ solution to fill the gaps between transport links and homes or offices which could draw more people away from their cars. My research has found that policies towards the new micromobility focused on decreasing transport inequalities in the United States. Conversely in Europe, there was more consideration for the environmental impact, but both continents have policies emphasising the importance of safety.
E-scooters and the environment
Despite cities frequently referencing environmental sustainability, few were found to have policies or regulations to ensure this. There was often an assumption that e-scooter users would previously have made their journey by car. However, in Paris only 8% of users would have driven if e-scooters were not an option. This was higher in the US, with cities consistently having a modal shift from cars of over 30%. However, this was explained by the lower availability of public transport compared with European cities. Therefore, US policies would not have the desired effect in Bristol.
A second environmental consideration is the lifecycle analysis of e-scooters. This shows that e-scooters still produce a significant amount of CO2 emissions, particularly when compared to active travel. E-scooters used as part of a sharing scheme are also frequently vandalised which shortens their lifespan. In UK cities which started their trials before Bristol, operators have already complained of high rates of vandalism. Many are also thrown into rivers which causes ecological impacts.
E-scooters and inequality
Many cities in the US have regulations aiming to improve access to transport for low-income communities. This has included unsuccessful discounted services. Operators have often failed to comply or the schemes have not been marketed. A more successful regulation was rebalancing e-scooters to ensure that some are placed in deprived communities. However, operators have claimed that this is economically and environmentally unsustainable. Using large trucks to move e-scooters around the city will increase CO2 emissions associated with them.
It is important that environmental goals do not come at the cost of excluding certain communities in the city, and vice versa. However, overall the most significant factor for decreasing inequality or decreasing CO2 emissions is which mode the shift comes from.
The most effective way to encourage a modal shift away from cars is to reallocate space to other modes and start designing cities around people. However, making such a significant change in the way we live our lives will be met with backlash from some. E-scooters can help mitigate this by providing an alternative mode of transport that could make the reallocation of road space to micromobilities more politically feasible.
Safety of e-scooters
What can be agreed upon by everyone is that e-scooters must be safe for users and for those around them. The main complaints about e-scooters are that they block pavements for more vulnerable pedestrians and in most cities, e-scooters are banned from pavement riding. Nevertheless, casual observation shows that this is often ignored. However, in Portland it was found that the presence of cycle lanes and lower speed limits decreased e-scooter pavement use by around 30%. In Bristol, 70% of respondents for a Sustrans survey supported building more cycle tracks even if it took space away from other traffic. The presence of cycle tracks could also lead to more active travel which has co-benefits for individual health and wellbeing.
Governance of e-scooters
E-scooters and other shared mobility technologies are part of a change in governance. There is now collaboration between public and private and it is essential that communication between the two is transparent. Local authorities must make clear their goals and set boundaries for operators without restricting them to the extent that they are unable to provide their services.
Overall, e-scooters alone are not going to solve our dysfunctional urban transport systems. However, they might provide a catalyst for more radical change away from the car-dominated city.
Is hydrogen the lifeblood of a low-carbon future, or an overhyped distraction from real solutions? One thing is certain – the coal, oil and natural gas which currently power much of daily life must be phased out within coming decades. From the cars we drive to the energy that heats our homes, these fossil fuels are deeply embedded in society and the global economy. But is the best solution in all cases to swap them with hydrogen – a fuel which only produces water vapour, and not CO₂, when burned?
Answering that question are six experts in engineering, physics and chemistry.
Road and rail
Hu Li, Associate Professor of Energy Engineering, University of Leeds
Transport became the UK’s largest source of greenhouse gas emissions in 2016, contributing about 28% of the country’s total.
Replacing the internal combustion engines of passenger cars and light-duty vehicles with batteries could accelerate the process of decarbonising road transport, but electrification isn’t such a good option for heavy-duty vehicles such as lorries and buses. Compared to gasoline and diesel fuels, the energy density (measured in megajoules per kilogram) of a battery is just 1%. For a 40-tonne truck, just over four tonnes of lithium-ion battery cells are needed for a range of 800 kilometres, compared to just 220 kilograms of diesel.
With the UK government set to ban fossil fuel vehicles from 2035, hydrogen fuel cells could do much of the heavy lifting in decarbonising freight and public transport, where 80% of hydrogen demand in transport is likely to come from.
A fuel cell generates electricity through a chemical reaction between the stored hydrogen and oxygen, producing water and hot air as a byproduct. Vehicles powered by hydrogen fuel cells have a similar driving range and can be refuelled about as quickly as internal combustion engine vehicles, another reason they’re useful for long-haul and heavy-duty transport.
Hydrogen fuel can be transported as liquid or compressed gas by existing natural gas pipelines, which will save millions on infrastructure and speed up its deployment. Even existing internal combustion engines can use hydrogen, but there are problems with fuel injection, reduced power output, onboard storage and emissions of nitrogen oxides (NOₓ), which can react in the lower atmosphere to form ozone – a greenhouse gas. The goal should be to eventually replace internal combustion engines with hydrogen fuel cells in vehicles that are too large for lithium-ion batteries. But in the meantime, blending with other fuels or using a diesel-hydrogen hybrid could help lower emissions.
It’s very important to consider where the hydrogen comes from though. Hydrogen can be produced by splitting water with electricity in a process called electrolysis. If the electricity was generated by renewable sources such as solar and wind, the resulting fuel is called green hydrogen. It can be used in the form of compressed gas or liquid and converted to methane, methanol, ammonia and other synthetic liquid fuels.
But nearly all of the 27 terawatt-hours (TWh) of hydrogen currently used in the UK is produced by reforming fossil fuels, which generates nine tonnes of CO₂ for every tonne of hydrogen. This is currently the cheapest option, though some experts predict that green hydrogen will be cost-competitive by 2030. In the meantime, governments will need to ramp up the production of vehicles with hydrogen fuel cells and storage tanks and build lots of refuelling points.
Hydrogen can play a key role in decarbonising rail travel too, alongside other low-carbon fuels, such as biofuels. In the UK, 6,049 kilometres of mainline routes run on electricity – that’s 38% of the total. Trains powered by hydrogen fuel cells offer a zero-emission alternative to diesel trains.
The Coradia iLint, which entered commercial service in Germany in 2018, is the world’s first hydrogen-powered train. The UK recently launched mainline testing of its own hydrogen-powered train, though the UK trial aims to retrofit existing diesel trains rather than design and build entirely new ones.
Aviation
Valeska Ting, Professor of Smart Nanomaterials, University of Bristol
Of all of the sectors that we need to decarbonise, air travel is perhaps the most challenging. While cars and boats can realistically switch to batteries or hybrid technologies, the sheer weight of even the lightest batteries makes long-haul electric air travel tricky.
Single-seat concept planes such as the Solar Impulse generate their energy from the sun, but they can’t generate enough based on the efficiency of current solar cells alone so must also use batteries. Other alternatives include synthetic fuels or biofuels, but these could just defer or reduce carbon emissions, rather than eliminate them altogether, as a carbon-free fuel like green hydrogen could.
Hydrogen is extremely light and contains three times more energy per kilogram than jet fuel, which is why it’s traditionally used to power rockets. Companies including Airbus are already developing commercial zero-emission aircraft that run on hydrogen. This involves a radical redesign of their fleet to accommodate liquid hydrogen fuel tanks.
An artist’s impression of what hydrogen-powered commercial flight might look like. Airbus
There are some technical challenges though. Hydrogen is a gas at room temperature, so very low temperatures and special equipment are needed to store it as a liquid. That means more weight, and subsequently, more fuel. However, research we’re doing at the Bristol Composites Institute is helping with the design of lightweight aircraft components made out of composite materials. We’re also looking at nanoporous materials that behave like molecular sponges, spontaneously absorbing and storing hydrogen at high densities for onboard hydrogen storage in future aircraft designs.
France and Germany are investing billions in hydrogen-powered passenger aircraft. But while the development of these new aircraft by industry continues apace, international airports will also need to rapidly invest in infrastructure to store and deliver liquid hydrogen to refuel them. There’s a risk that fleets of hydrogen aeroplanes could take off before there’s a sufficient fuel supply chain to sustain them.
Heating
Tom Baxter, Honorary Senior Lecturer in Chemical Engineering, University of Aberdeen & Ernst Worrell, Professor of Energy, Resources and Technological Change, Utrecht University
If the All Party Parliamentary Group on Hydrogen’s recommendations are taken up, the UK government is likely to support hydrogen as a replacement fuel for heating buildings in its next white paper. The other option for decarbonising Britain’s gas heating network is electricity. So which is likely to be a better choice – a hydrogen boiler in every home or an electric heat pump?
First there’s the price of fuel to consider. When hydrogen is generated through electrolysis, between 30-40% of the original electric energy is lost. One kilowatt-hour (kWh) of electricity in a heat pump may generate 3-5 kWh of heat, while the same kWh of electricity gets you only 0.6-0.7 kWh of heat with a hydrogen-fuelled boiler. This means that generating enough hydrogen fuel to heat a home will require electricity generated from four times as many turbines and solar panels than a heat pump. Because heat pumps need so much less energy overall to supply the same amount of heat, the need for large amounts of stored green energy on standby is much less. Even reducing these losses with more advanced technology, hydrogen will remain relatively expensive, both in terms of energy and money.
So using hydrogen to heat homes isn’t cheap for consumers. Granted, there is a higher upfront cost for installing an electric heat pump. That could be a serious drawback for cash-strapped households, though heat pumps heat a property using around a quarter of the energy of hydrogen. In time, lower fuel bills would more than cover the installation cost.
Replacing natural gas with hydrogen in the UK’s heating network isn’t likely to be simple either. Per volume, the energy density of hydrogen gas is about one-third that of natural gas, so converting to hydrogen will not only require new boilers, but also investment in grids to increase how much fuel they can deliver. The very small size of hydrogen molecules mean they’re much more prone to leaking than natural gas molecules. Ensuring that the existing gas distribution system is fit for hydrogen could prove quite costly.
In high-density housing in inner cities, district heating systems – which distribute waste heat from power plants and factories into homes – could be a better bet in a warming climate, as, like heat pumps, they can cool homes as well as heat them.
Above all, this stresses the importance of energy efficiency, what the International Energy Agency calls the first fuel in buildings. Retrofitting buildings with insulation to make them energy efficient and switching boilers for heat pumps is the most promising route for the vast majority of buildings. Hydrogen should be reserved for applications where there are few or no alternatives. Space heating of homes and buildings, except for limited applications like in particularly old homes, is not one of them.
Electricity and energy storage
Petra de Jongh, Professor of Catalysts and Energy Storage Materials, Utrecht University
Fossil fuels have some features that seem impossible to beat. They’re packed full of energy, they’re easy to burn and they’re compatible with most engines and generators. Producing electricity using gas, oil, or coal is cheap, and offers complete certainty about, and control over, the amount of electricity you get at any point in time.
Meanwhile, how much wind or solar electricity we can generate isn’t something that we enjoy a lot of control over. It’s difficult to even adequately predict when the sun will shine or the wind will blow, so renewable power output fluctuates. Electricity grids can only tolerate a limited amount of fluctuation, so being able to store excess electricity for later is key to switching from fossil fuels.
Hydrogen seems ideally suited to meet this challenge. Compared to batteries, the storage capacity of hydrogen is unlimited – the electrolyser which produces it from water never fills up. Hydrogen can be converted back into electricity using a fuel cell too, though quite a bit of energy is lost in the process.
Unfortunately, hydrogen is the lightest gas and so it’s difficult to store and transport it. It can be liquefied or stored at very high pressures. But then there’s the cost – green hydrogen is still two to three times more expensive than that produced from natural gas, and the costs are even higher if an electrolyser is only used intermittently. Ideally, we could let hydrogen react with CO₂, either captured from the air or taken from flue gases, to produce renewable liquid fuels that are carbon-neutral, an option that we’re investigating at the Debye Institute at Utrecht University.
Heavy industry
Stephen Carr, Lecturer in Energy Physics, University of South Wales
Industry is the second most polluting sector in the UK after transport, accounting for 21% of the UK’s total carbon emissions. A large proportion of these emissions come from processes involving heat, whether it’s firing a kiln to very high temperatures to produce cement or generating steam to use in an oven making food. Most of this heat is currently generated using natural gas, which will need to be swapped out with a zero-carbon fuel, or electricity.
Let’s look in depth at one industry: ceramics manufacturing. Here, high-temperature direct heating is required, where the flame or hot gases touch the material being heated. Natural gas-fired burners are currently used for this. Biomass can generate zero-carbon heat, but biomass supplies are limited and aren’t best suited to use in direct heating. Using an electric kiln would be efficient, but it would entail an overhaul of existing equipment. Generating electricity has a comparably high cost too.
Swapping natural gas with hydrogen in burners could be cheaper overall, and would require only slight changes to equipment. The Committee on Climate Change, which advises the UK government, reports that 90 TWh of industrial fossil fuel energy per year (equivalent to the total annual consumption of Wales) could be replaced with hydrogen by 2040. Hydrogen will be the cheapest option in most cases, while for 15 TWh of industrial fossil fuel energy, hydrogen is the only suitable alternative.
Hydrogen is already used in industrial processes such as oil refining, where it’s used to react with and remove unwanted sulphur compounds. Since most hydrogen currently used in the UK is derived from fossil fuels, it will be necessary to ramp up renewable energy capacity to deliver truly green hydrogen before it can replace the high-carbon fuels powering industrial processes.
The same rule applies to each of these sectors – hydrogen is only as green as the process that produced it. Green hydrogen will be part of the solution in combination with other technologies and measures, including lithium-ion batteries, and energy efficiency. But the low-carbon fuel will be most useful in decarbonising the niches that are currently difficult for electrification to reach, such as heavy-duty vehicles and industrial furnaces.
