IPCC blog series – Working Group 3 – Mitigation of climate change

This blog is part of a series on the Intergovernmental Panel on Climate Change’s recent 6th Assessment Report, with this post covering the output of Working Group III and the proposed solutions and mitigations for the climate crisis. This article also features a chat with IPCC Lead Author Dr Jo House and contributor Viola Heinrich, researchers at the University of Bristol and Cabot Institute for the Environment. 

Of the three Working Groups, the third makes for the most positive reading. As the title suggests, this one is all about the mitigation of climate change and preventing the disastrous climate futures explained by Working Groups I and II. Whilst remaining focussed on the impending nature of the climate crisis, this report spells out that we have the solutions.

As discussed in the previous posts, massive behavioural changes are needed at government and societal levels. When I spoke to academics, they were positive that we were well past the point of whether climate change is real or has an impact on humanity and that economically minded leaders are starting to see the benefits of sustainable practice and the economic security it brings. Governments and states are listening and looking at policy to mitigate the crisis.

Let’s look at some of the solutions and mitigations proposed:

The quicker we act, the less economic impact

This follows on nicely from previous reports that stated the effects of warming increase with each incremental global average temperature increase. That is to say, a +1.5 degrees C future will see less devastation than a +2 degrees C or even a +1.7 degrees C rise in temperature. Such disasters (drought, extreme weather, flooding) require huge amounts of money resources to sort out. From an economic security point of view, it makes complete sense to act with great urgency. The climate crisis is already here, and therefore already having an economic impact. Action immediately will mitigate against the future potential costs of a climate disaster.

Relative to the economic impact of climate disaster in the future, the investment of reducing the impact of the crisis and securing a liveable planet is small.

The immediate reduction of fossil fuel production and limitation of greenhouse gases in the pursuit of Net Zero

As discussed before, the greatest culprit of the climate crisis is unequivocally greenhouse gas (GHG) emissions from fossil fuels. Therefore, in an ideal world, the immediate halt of fossil fuel extraction, production and consumption would be enough to prevent an overshoot +1.5 degrees C (as discussed in the first report, there is a lag between emissions and warming). Unfortunately, this is not an ideal world, so significant policy to pursue a Net-Zero will be needed.

Going further, carbon must also be removed from the atmosphere somehow, to allow the planet to return to preindustrial atmospheric carbon levels.

Carbon removal, naturally and technologically

A key aspect to the third Working Group is its arguments for carbon capture. This could be either through natural carbon removal through plants and trees, or by using carbon removal technology through direct air capture.

Carbon capture will be essential to solving the climate crisis, as carbon needs to be removed in order to return to the pre-industrial levels of atmospheric carbon. As well as this, proposed tech allows for carbon to be captured at the source of emissions. The issue is that carbon capture could lead to a dependence on the technology.

Companies, understandably, are drawn to the idea of “planting trees” to offset their emissions. It’s visible, tangible, and easy for the public to grasp. However, it’s not always the most efficient use of land and resources, and some worry that these methods will be exploited as a crutch to not reduce emissions output. While an extremely important step in mitigating climate change, some worry that there may be a resultant reliance on carbon removal over carbon emission reduction, allowing the world’s most prolific polluters to continue maintain their carbon output.

One of the most cost-effective mitigation techniques is simply the protection of existing forests and natural sites. The IPCC also stresses that decisions of protection like these must involve the input of the indigenous communities living there.

From the policy level to the personal level

It’s brilliant to be making the personal decisions to limit your own carbon impact, but individuals have limited impact on the climate system. What these reports suggest is wide reaching policy at state level to incentivise populations to make better climate conscious choices, by making things easier through improved infrastructure and methods of “demand management”, reducing the consumption of resource intensive products like meat and dairy. Diet changes at a population scale will be needed to combat the emissions of methane (another greenhouse gas) in particular.

In urban environments, investment in public transportation and cycling infrastructure would go a long way to reduce emissions. As would policy that makes retrofitting buildings to be more energy efficient and building new infrastructure with energy efficiency in mind.

For a great bit of further reading, the IPCC Special report on Climate Change and Land goes into much further detail about the impact of changing diets and consumption habits at scale.

Read the IPCC Special Report on Climate Change and Land

As previously discussed in the blog post on the WGII report, the impacts of climate change are not equal or in proportion to climate impact of the nation affected. Therefore, much of the mitigation will need to take the form of humanitarian aid, improving infrastructure for nations without the resources to do so themselves.

The IPCC reports end on a poignant note: “International cooperation is a critical enabler for achieving ambitious climate change mitigation goals”.

Insight from IPCC Lead Author Dr Jo House and contributor Viola Heinrich

Dr Jo House

Dr Jo House is Reader in Environmental Science and Policy, Research Lead of Cabot Institute for the Environment’s Environmental Change theme and a Lead Author on the IPCC’s AR6 Working Group III report.

Viola Heinrich is a Physical Geography PhD Candidate at the University of Bristol, studying the emissions and climate mitigation potential within the land use sector in the tropics, especially the Brazilian Amazon. Viola assisted Dr House in her AR6 work, producing figures for WG III.

How did you get involved with the IPCC and WGIII?

Dr Jo House – “I have been working on IPCC reports for 20 years. I was first employed as a chapter scientist to support the chapter team for working group I, 3rd assessment report carbon cycle chapter. I was then made a lead author for the synthesis report for AR3. Since then, I have been a lead author or contributing author on all three Working Groups, as well a lead author for the Special Report on Climate Change and Land. I am also a lead author twice for the IPCC Task Force on Inventories, who provide methodological guidance to countries on how to produce their greenhouse gas inventories, for reporting to the UNFCCC, as well as accounting under the Kyoto Protocol.

Viola Heinrich

Despite the long hours and the many thousands of comments we must respond to, I do IPCC because I care about climate change, and IPCC gets the science into the hands of people who can do something about it.”

Viola Heinrich – “I’m a PhD student working on understanding the emissions and climate mitigation potential within the land use sector in the tropics, especially the Brazilian Amazon. Jo, as my supervisor, approached me in 2019 to help produce some figures for her work on AR6 and WGIII.

It was a great learning experience seeing how these report cycles work and one bonus was that the work I produced for the IPCC reports was able used in the introduction to my PhD thesis”

What’s one key message you’d like to highlight from WGIII?

Dr Jo House – “We are nearly already too late to stay within 2 degrees, so we need to reduce fossil fuels usage drastically and rapidly to avoid even worse impacts.

Also specifically from a land perspective: The land has potential for mitigation, but it cannot do it all, planting trees is not a get out of jail free card for continuing to burn fossil fuels.”

Viola Heinrich – “This report has followed nicely on form previous cycles in that it has reaffirmed what we know about the land use component and the mitigation potential of the land use sector (20% to 30% by 2050). The big caveat of course is that the land can’t do it all and we need to be actively reducing emissions rather than relying in capture methods from trees for example.

Another interesting factor about the report is that it stresses the importance of considering the local communities in places where solutions and mitigations take place, seeking their expertise in protection, and understanding how these actions will affect them.”


As always, we recommend taking a look at the IPCC’s full reports and report summaries for yourself if you seek to further understand the evidence and reasoning behind their headline statements.

That wraps up the blog series, I hope that it was enjoyable and informative.


This blog series was written by Cabot Communications Assistant Andy Lyford, an MScR Student studying Paleoclimates and Climate modelling on the Cabot Institute’s Master’s by Research in Global Environmental Challenges at the University of Bristol.

Andy Lyford



The Paris Agreement – where are we now?

Cabot Annual Lecture 2018

This year the Cabot Institute Annual Lecture posed a critical question: where are we with current efforts to tackle global climate change? The event brought together over 800 people to hear from leading Cabot Institute experts in climate science, policy, and justice, Dr Jo House, Dr Dann Mitchell, Dr Alix Dietzel and Professor Tony Payne. It was both an appraisal of the findings of the recently published report of the Intergovernmental Panel on Climate Change (IPCC), and a grounded call to climate action.

Paris commitments

In 2015 world leaders adopted the Paris Agreement committing all parties to limiting global average temperatures to well below 2 °C above pre-industrial levels and to pursue efforts to limit warming to 1.5 °C. All countries undertook to achieve global peaking of greenhouse gas emissions as soon as possible and to enact increasingly ambitious mitigation measures in line with the overarching temperature goals. The Paris Agreement, in contrast to the preceding Kyoto Protocol, is not based on legally binding reductions targets for developed countries, but on a voluntary system of pledges known as ‘nationally determined contributions’ for all parties which will be subject to a stocktake of global progress every five years, beginning in 2023.

Although the Paris Agreement initially offered great promise with pledges being made by both developed and developing countries, a report by the UN Environment Programme in November 2017 examining progress towards the global temperature goals found that even if all current pledges are honoured, we remain on track for some 3 °C of warming by 2100. In light of this, and under the Presidency of Fiji, the first Small Island State to preside over a Conference of the Parties at COP23 last year, the focus has been on building momentum for more urgent action through the facilitative ‘Talanoa dialogue’ and on hashing out the final operating procedures for the Agreement. The findings of the IPCC Report on Global Warming of 1.5°C, published on 8 October represent a further important piece of the picture of global progress, which three of the Cabot speakers shed light upon as contributing authors.

Why 0.5°C of warming matters

The findings of the report are significant in illustrating the projected differences in climate change impacts between the 1.5°C and 2°C temperature thresholds. Dr Dann Mitchell outlined the evidence for increases in regional mean temperatures and for the increasing likelihood of temperature extremes of the kind witnessed during this summer’s European heatwave, which we could see occur almost every year at 2°C of warming. These extremes, together with the projected intensification of storms presented in the report, are closely linked to human risks to health, wellbeing and livelihoods.

Cabot Annual Lecture 2018
Dr Dann Mitchell

Professor Tony Payne echoed these concerns with respect to the findings of the report on sea-level rise which predict an extra 10cm rise between the 1.5°C and 2°C temperature thresholds, equating, in turn, to an additional 10 million people at risk of related impacts including inundation and displacement. The destabilisation of the ice sheets is set to become more likely beyond 1.5°C, entailing risks of much greater sea-level rise in the future. Professor Payne further outlined the strikingly severe consequences for coral reefs of the two temperature thresholds, with projections that at 2°C all coral in the oceans will die, while by limiting temperature to 1.5°C, some 10-30% of coral will survive. Reefs are not only crucial for the maintenance of healthy marine ecosystems, but also for the millions of people around the world who depend upon those ecosystems for their food security and livelihoods.

Cabot Annual Lecture 2018
Professor Tony Payne

A call for action

Against these stark warnings on the significance of limiting global temperatures to 1.5°C, Dr Jo House outlined some key recommendations for how we can get on track. The IPCC report sets out a number of pathways for action, each calling for changes across a broad spectrum of policy sectors with the aim of rapidly reducing greenhouse gas emissions and enhancing the absorption of existing carbon in the atmosphere. These changes include moving away from fossil fuels to renewable sources of energy, greening the transport sector, replanting forests, and investing in carbon capture and storage technologies. Dr House underlined the importance of action at all levels of governance to meet these goals. At the national level in the UK under the provisions of the Climate Change Act we are already committed to an 80% reduction on 1990 levels by 2050, while at the city level in Bristol, the Climate and Energy Security Framework commits to the same target, with a 50% reduction to be achieved by 2025.

Cabot Annual Lecture 2018
Dr Jo House

This action in climate policy is increasingly being driven by sub-state actors and Dr Alix Dietzel highlighted the crucial role that local government, civil society groups, citizens initiatives, corporations, and individuals are playing in this. Dr Dietzel expressed cause for hope in the reaction of sub-state actors to the announcement of the withdrawal of the United States from the Paris Agreement, with the ‘WE ARE STILL IN’ movement garnering support from city mayors, governors, tribal leaders, universities, and businesses for continuing commitment to the Paris goals. At the individual level, the actions we can all take within the boundaries of our own capabilities were discussed, outlining our capacity to affect change through our consumption and lifestyle choices. The need to consider the ethical questions surrounding our responsibilities as individuals and global citizens remains crucial, particularly in light of the disproportionately harmful effects that climate impacts will have upon those who have contributed least to the problem.

Cabot Annual Lecture 2018
Dr Alix Dietzel

The risks of inaction on the 1.5°C threshold were balanced against the opportunities and benefits of action by the panel. The successful lobbying efforts of climate-vulnerable states to embed the 1.5°C threshold within the Paris framework, alongside the commitment of many governments and sub-state actors to meet it, are cause for hope but we still have a long way to go.

This blog was written by Cabot Institute member Alice Venn, a PhD Candidate in Environment, Energy & Resilience at the University of Bristol’s Law School.

Alice Venn

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Report from a (slightly less-depressed) climate scientist on the All Parliamentary Climate Change Group meeting on “stranded assets”

Synthesis Report of the IPCC. Image credit IPCC

Lets face it, it’s fairly depressing being a climate scientist.  The Synthesis Report of the Intergovernmental Panel on Climate Change was adopted by the world governments last Sunday (2 November 2014). This report drew on the three individual reports published over the last year on the Science, Impacts and Mitigation of climate change, all of which I was proud to contribute to.  Yet apart from a few comments from the global great and good on the urgency of the situation and the need to move away from fossil fuels to avoid changes that will be dangerous for mankind and nature alike, it made relatively little headlines. I was wondering if it would really make any difference to anything that anyone does. I will still dread Daily Mail-reading cab drivers asking me what I do for a living, as it’s disheartening to try and explain the science to someone who has far more pressing and immediate concerns and would rather not think about, let alone believe, what we scientists repeatedly say, stronger, louder, and with far richer detail, but basically unchanged over the last 20 years.

So I was really encouraged, if not elated, after attending the All Parliamentary Climate Change Group meeting on “Stranded Assets: How can policy makers act to ensure economic stability while reducing emissions?”.  It wasn’t just that it was fun to be at the Houses of Parliament on the 5th November.  It seems that certain parts of the financial sector are taking climate risk extremely seriously and advising that investment in the fossil fuel industry (where 15 to 20% of UK pension investments are placed) is no longer the safe bet it used to be, that the risks are too high and that investors should better put their money into “clean” alternatives such as renewables.

What are ‘stranded assets’?

These are assets that succumb to unanticipated devaluation due to technology change, consumer change, regulatory change etc.    In other words, investments in large infrastructure fossil fuel projects could become devalued in the future due to factors such as increasing capital costs of fossil fuels (e.g. due to extraction, regulation, carbon pricing, costs of using carbon capture and storage technology), decreasing costs of competitive renewables, and increasing direct physical risks to the industry from climate impacts.  Thus investing in them is more risky than many investors take account of, as such risks do not currently have to be disclosed.  The Carbon Tracker Initiative have published reports on this, managing to take the science and talk in the language of the financial industry to present a convincing argument for why and how to reassess business models and investment portfolios.

One may easily argue that the Carbon Tracker Initiative was set up to solve the challenge of moving away from fossil fuels through actions within the capital market, so they are bound to say this. But it seems some very established Institutions feel the same.  Just a few weeks ago the Rockefeller Foundation, that initially built their fortune on the back of oil, announced that it was going to move away from investment in fossil fuels and switch to clean technology investment.  Last month at the World Bank, Mark Carney, Governor of the Bank of England warned investors to avoid the “carbon bubble” of stranded fossil fuel assets, as many governments (e.g. Norway and Sweden), businesses and individual wealthy investors commit to divesting away from fossil fuels. The organisation 350.org, having successfully persuaded many companies in the USA to divest, is putting pressure on UK businesses. Edinburgh University has signed up…take note Bristol – is this something we should do?

As Tim Yeo, Chairman of the Energy and Climate Change committee put it, the science is accepted.  The fact that we have to keep within the trillion tonnes of CO2 emissions to avoid “dangerous” changes above 2 degrees seemed to be widely accepted among the various political and financial bodies represented at the meeting.  Cost is now the issue, and those countries (and businesses) that reduce early will have enormous economic benefit.  Is everyone else as convinced? Well sadly not everyone, but at least if enough investors start to move they can lead the governments, which is more of an encouraging prospect than holding out for global agreement and strong action from the governments in Paris next year.
This blog is written by Dr Jo House, Cabot Institute, School of Geographical Sciences, University of Bristol.  Jo is a Leverhulme Research Fellow looking at the role of the terrestrial biosphere in climate change and climate mitigation.

Jo House