Every year, world leaders gather to find ways of limiting global warming. The latest of these ‘COP’ meetings, COP30, is in Belém, Brazil from 10 to 20 November 2025. COP stands for ‘Conference of the Parties’, the decision-making body of the United Nations Framework Convention on Climate Change (UNFCCC).
Perhaps the best-known of these meetings was in Paris in 2015. This resulted in the Paris Agreement. This is a legally-binding international treaty to limit global warming to well below 2°C and preferably to 1.5°C above pre-industrial levels. This would involve reducing greenhouse gas emissions and/or taking carbon absorbing measures. All UN countries except for Iran, Libya and Yemen are signatories to the agreement.
However, on coming to office in January 2025, President Trump announced that the USA will withdraw from the agreement in January 2026. Instead, he would prioritise fossil fuel production, under the mantra, ‘drill, baby, drill’. Previously he had claimed that global warming is a hoax concocted by China designed to undermine the competitive power of the USA.
Progress in reducing emissions and mitigating climate change
Since 2020, each country has been required to submit its own emissions-reduction targets, known as ‘nationally determined contributions’ (NDCs), and the actions it will take to meet them. Every five years each country must submit a new NDC more ambitious than the last. New NDCs are due this year. As of 12 November, 112 of the 197 countries had submitted a new NDC (including the USA, China, the EU and the UK). These 112 countries account for around 71 per cent of global emissions.
Implementing all new NDCs would reduce global CO2 emissions by between 15 and 25 per cent from current levels by 2035. But this would merely reduce global warming to around 2.6°C above pre-industrial levels. Approximately 35 per cent emissions reductions by 2035 would be required to restrict global warming to 2°C and 55 per cent to restrict it to 1.5°C.
But implementing the Paris Agreement has still had a high degree of success. Without the action taken and being taken over the past 10 years, it is predicted that global temperatures by 2050 would rise by 3–3.5°C.
Rich countries are expected to provide finance to low-income countries. This is required to help such countries adopt green technologies and to adapt to the harmful effects of climate change (e.g. through irrigation schemes and flood defences). At COP29 in Azerbaijan, the ‘Baku Finance Goal’ was agreed. This is an agreement to provide climate finance of $1.3 trillion per year by 2035 to developing countries from all public and private sources.
The subsequent ‘Baku to Belém Roadmap’ provides a set of suggested actions for governments, financial institutions and the private sector to bridge the gap between current climate finance flows and the $1.3 trillion agreed to meet global climate goals. The roadmap is a central focus of the COP30 conference in Belém, with discussions between countries on how to translate the Baku finance goal into concrete, tangible actions and integrate it into formal decisions.
The role of Donald Trump
As well as announcing that the USA will withdraw from the Paris Agreement in January 2026, since coming to office in 2025, President Trump has given billions of dollars of tax cuts to fossil fuel firms and allowed drilling for oil and gas on federal lands. At the same time, he has described renewable energy as ‘a joke’ that will bankrupt countries and has slashed subsidies and tax breaks for solar and wind power, withdrawn permits for wind and solar farms, and cut funding for green energy research.
He wants the USA to be world leader in fossil fuel energy, calling on governments to buy US oil and gas, threatening some countries with tariffs if they do not. Already, Japan, South Korea and several European countries have agreed to buy huge quantities of US oil and liquefied natural gas (LNG). A worry is that other similarly inclined governments, such as Argentina, may roll back on their commitments to a green transition and instead boost their fossil fuel industries.
This gives added urgency to the Belém talks. It is crucial for the rest of the world to stick together in pushing ahead to combat global warming and in adopting and sticking to tough NDCs. It is also crucial for rich countries to support dlow-income countries in adopting climate-friendly investment and in measures to mitigate the effects of global warming.
The economics of climate change
Climate change is directly caused by market failures. One of the most important of these is that the atmosphere is a common resource: it is not privately owned; it is a global ‘commons’. Individuals and firms use it at a zero price. If the price of any good or service to the user is zero, there is no incentive to economise on its use. Thus for the emitter there are no private costs of using the atmosphere in this way as a ‘dump’ for their emissions and, in a free market, no incentive to reduce the climate costs.
And yet when firms emit greenhouse gases into the atmosphere there are costs to other people. To the extent that they contribute to global warming, part of these costs will be borne by the residents of that country; but a large part will be borne by inhabitants of other countries.
These climate costs are external costs to the firm and are illustrated in the figure. It shows an industry that emits CO2. To keep the analysis simple, assume that it is a perfectly competitive industry with demand and supply given by curves D and S, which are equal to the marginal private benefits (MPB) and marginal private costs (MPC), respectively. There are no externalities on the demand side and hence MPB equals the marginal social cost (MSB). Market equilibrium is at point a, with output at Qpc and price at Ppc. (Click here for a PowerPoint.)
Assume that the emissions create a marginal cost to society equal to MECc. Assume that the MEC increases as output and total emissions increase. The MECc line is thus upward sloping. At the market price of Qpc, these external climate costs are equal to the purple vertical line. When these external climate costs are added to private costs, this gives a marginal social cost given by MSC = MPC + MECc. The gives a socially optimal level of output of the product of Q* at a price of P*, with the optimum point of c.
In other words, other things being equal, the free market overproduces products with climate externalities. If the output is to be reduced to the social optimum of Q*, then the government will need to take measures such as those advocated in the Paris Agreement. These could include imposing taxes on products, such as electricity generated by fossil fuels, or on the emissions themselves. Or green alternatives, such as wind power, could be subsidised.
Alternatively, regulations could be used to cap the production of products creating emissions, or caps on the emissions themselves could be imposed. Emissions permits could be issued or auctioned. Only firms in possession of the permits would be allowed to emit and the permits would cap emissions below free-market levels. These permits could be traded under a cap-and-trade scheme, such as the EU’s Emissions Trading Scheme. Again, such schemes are advocated under the Paris Agreement.
COP30 and progress in tackling climate change
The USA is not attending COP30 in Brazil. Nor is the Chinese leader, Xi Jinping. However, there are growing opportunities for translating aims into practical policies for specific sectors, such as energy, transport and carbon-intensive industries. These policies may require some degree of government action – taxes, subsidies or regulation – to internalise climate externalities. But increasingly, green alternatives are becoming economically viable without subsidies or with just initial government funding to ‘crowd in’ private investment, which will then attract further private capital as external economies of scale kick in. Increasingly investors will find profitable opportunities in climate-friendly projects.
At the same time, while the USA is moving away from climate-friendly investment (as least for the term of the Trump Presidency), China is moving in the opposite direction, with massive investment in solar panels, wind turbines, EVs and batteries – investment that is bringing down their cost and thereby encouraging their adoption around the world. Such technologies create huge opportunities for low-income countries to provide affordable energy and to create local jobs, both skilled and unskilled. It also helps them achieve much greater energy security by reducing their reliance on fossil fuel imports
Chinese advances in green technology are also providing a stimulus to other countries to invest in renewable industries to prevent Chinese dominance. The danger, however, of Chinese dominance in the renewable sector in high-income countries is that it may encourage them to impose tariffs on Chinese imports of EVs, solar panels, etc. to protect their own industries.
But despite the growing opportunities for profitable adoption of green technologies without government support, there is still much that governments need to do to encourage the process. COP meetings are an important forum for discussing such policies and holding governments to account for meeting or not meeting their targets.
Articles
- What is COP30 and why does it matter for the climate?
Chatham House, Anna Åberg (5/9/25)
- COP30 in Brazil: What is at stake for global collaboration on climate and nature?
World Economic Forum, Pim Valdre (5/11/25)
- What is COP30 and why does it matter?
CNN, Laura Paddison (11/11/25)
- Why COP 30 in Brazil Matters for a Thriving Economy and a Safe, Livable Planet
Union of Concerned Scientists (UCS),Rachel Cleetus (7/11/25)
- Nationally Determined Contributions: The Action Plans Behind Global Efforts To Fight the Climate Crisis
Center for American Progress (CAP, Kalina Gibson and Courtney Federico (22/9/25)
- New climate pledges only slightly lower dangerous global warming projections
UN Environment Programme, Press Release (4/11/25)
- COP30: Trump and many leaders are skipping it, so does the summit still have a point?
BBC News, Justin Rowlatt (10/11/25)
- Trump dismisses clean energy as ‘a joke.’ But Americans deserve facts, not fear
USA Today, Mark McNees (23/9/25)
- The surprising countries pulling off stunningly fast clean energy transitions
CNN, Ella Nilsen and Samuel Hart (7/11/25)
Could the world’s biggest polluter be its savior against climate change?
CNN, Simone McCarthy (17/11/25)
- COP 2025: Outlook and Implications for Investors
RankiaPro, Joanna Piwko, Allegra Ianiri, Marie Lassegnore and Jean-Philippe Desmartin (10/11/25)
Information and Data
Questions
- Summarise the Paris Agreement.
- Summarise the Baku to Belém Roadmap to 1.3T.
- What incentives are there for countries to stick to their NCDs?
- Using a diagram similar to that above, illustrate how the free market will produce a sub-optimal amount of solar power because the marginal social benefit exceeds the marginal private benefit. How might the calculation be changing?
- How might game theory be used to analyse possible international decision making at COP conferences? How might this be affected by the attitudes of the Trump administration?
- Is it in America’s interests to cease investing in green energy and green production methods?

Politicians, business leaders, climate scientists, interest groups and journalists from across the world have been meeting in Dubai at the COP28 climate summit (the 28th annual meeting of the Conference of the Parties (COP) to the United Nations Framework Convention on Climate Change (UNFCCC)). The meeting comes at a time when various climate tipping points are being reached or approached – some bad, but some good. Understanding these tipping points and their implications for society and policy requires understanding not only the science, but also the various economic incentives affecting individuals, businesses, politicians and societies.
Tipping points
A recent report (see first reference in articles section below) identified various climate tipping points. These are when global temperatures rise to a point where various domino effects occur. These are adverse changes to the environment that gather pace and have major effects on ecosystems and the ability to grow food and support populations. These, in turn, will have large effects on economies, migration and political stability.
According to the report, five tipping points are imminent with the current degree of global warming (1.2oC). These are:
- Melting of the Greenland ice sheet;
- Melting of the West Antarctic ice sheet;
- Death of warm-water coral reefs;
- Collapse of the North Atlantic Subpolar Gyre circulation, which helps to drive the warm current that benefits Western Europe;
- Widespread rapid thawing of permafrost, where tundra without snow cover rapidly absorbs heat and releases methane (a much more powerful source of global warming than CO2).
With global warming of 1.5oC, three more tipping points are likely: the destruction of seagrass meadows, mangrove swamps and the southern part of the boreal forests that cover much of northern Eurasia. As the temperature warms further, other tipping points can interact in ways that drive one another, resulting in tipping ‘cascades’.
But the report also strikes an optimistic note, arguing that positive tipping points are also possible, which will help to slow global warming in the near future and possibly reverse it further in the future.

The most obvious one is in renewable energy. Renewable power generation in many countries is now cheaper than generation from fossil fuels. Indeed, in 2022, over 80% of new electricity generation was from solar and wind. And as it becomes cheaper, so this will drive investment in new renewable plants, including in small-scale production suitable for use in developing countries in parts not connected to a grid. In the vehicle sector, improved battery technology, the growth in charging infrastructure and cheaper renewable sources of electricity are creating a tipping point in EV take-up.
Positive tipping points can take place as a result of changing attitudes, such as moving away from a meat-intensive diet, avoiding food waste, greater use of recycling and a growth in second-hand markets.
But these positive tipping points are so far not strong enough or quick enough. Part of the problem is with economic incentives in market systems and part is with political systems.
Market failures
Economic decisions around the world of both individuals and firms are made largely within a market environment. But the market fails to take into account the full climate costs and benefits of such decisions. There are various reasons why.
Externalities. Both the production and consumption of many goods, especially energy and transport, but also much of agriculture and manufacturing, involve the production of CO2. But the costs of the resulting global warming are not born directly by the producer or consumer. Instead they are external costs born by society worldwide – with some countries and individuals bearing a higher cost than others. The result is an overproduction or consumption of such goods from the point of view of the world.
The environment as a common resource. The air, the seas and many other parts of the environment are not privately owned. They are a global ‘commons’. As such, it is extremely difficult to exclude non-payers from consuming the benefits they provide. Because of this property of ‘non-excludability’, it is often possible to consume the benefits of the environment at a zero price. If the price of any good or service to the user is zero, there is no incentive to economise on its use. In the case of the atmosphere as a ‘dump’ for greenhouse gases, this results in its overuse. Many parts of the environment, however, including the atmosphere, are scarce: there is rivalry in their use. As people increase their use of the atmosphere as a dump for carbon, so the resulting global warming adversely affects the lives of others. This is an example of the tragedy of the commons – where a free resource (such as common land) is overused.
Inter-generational problems. The effect of the growth in carbon emissions is long term, whereas the benefits are immediate. Thus consumers and firms are frequently prepared to continue with various practices, such as driving, flying and using fossil fuels for production, and leave future generations to worry about their environmental consequences. The problem, then, is a reflection of the importance that people attach to the present relative to the future.
Ignorance. People may be contributing to global warming without realising it. They may be unaware of which of the goods they buy involve the release of carbon in their production or how much carbon they release when consumed.
Political failures
Governments, whether democratic or dictatorships, face incentives not to reduce carbon emissions – or to minimise their reduction, especially if they are oil producing countries. Reducing carbon involves short-term costs to consumers and this can make them unpopular. It could cost them the next election or, in the case of dictatorships, make them vulnerable to overthrow. What is more, the oil, coal and gas industries have a vested interest in continuing the use of fossil fuels. Such industries wield considerable political power.
Even if governments want the world to reduce carbon emissions, they would rather that the cost of doing so is born less by their own country and more by other countries. This creates a prisoner’s dilemma, where the optimum may be for a large global reduction in carbon emissions, but the optimum is not achieved because countries individually are only prepared to reduce a little, expecting other countries to reduce more. Getting a deal that is deemed ‘fair’ by all countries is very difficult. An example is where developing countries, may feel that it is fair that the bulk of any cuts, if not all of them, should be made by developed countries, while developed countries feel that fixed percentage cuts should be made by all countries.
Policy options
If the goal is to tackle climate change, then the means is to reduce the amount of carbon in the atmosphere (or at the least to stop its increase – the net zero target). There are two possibilities here. The first is to reduce the amount of carbon emissions. The second is to use carbon capture and storage or carbon sequestration (e.g. through increased forestation).
In terms of reducing carbon emissions, the key is reducing the consumption of carbon-producing activities and products that involve emissions in their production. This can be achieved through taxes on such products and/or subsidies on green alternatives (see the blog ‘Are carbon taxes a solution to the climate emergency?‘). Alternatively carbon-intensive consumption can be banned or phased out by law. For example, the purchase of new petrol or diesel cars cold be banned beyond a certain date. Or some combination of taxation and regulation can be used, such as in a cap-and-trade system – for example, the EU Emissions Trading System (EU ETS) (see the blog ‘Carbon pricing in the UK‘). Then there is government investment in zero carbon technologies and infrastructure (e.g. electrifying railways). In practice, a range of policy instruments are needed (see the blog ‘Tackling climate change: “Everything, everywhere, all at once”‘).
With carbon capture, again, solutions can involve a mixture of market mechanisms and regulation. Market mechanisms include subsidies for using carbon capture systems or for afforestation. Regulation includes policies such as requiring filters to be installed on chimneys or banning the felling of forests for grazing land.
The main issue with such policies is persuading governments to adopt them. As we saw above, governments may be unwilling to bear the short-term costs to consumers and the resulting loss in popularity. Winning the next election or simple political survival may be their number-one priority.
COP28
The COP28 summit concluded with a draft agreement which called for the:
transitioning away from fossil fuels in energy systems, in a just, orderly and equitable manner, accelerating action in this critical decade, so as to achieve net zero by 2050 in keeping with the science.
This was the first COP summit that called on all nations to transition away from fossil fuels for energy generation. It was thus hailed as the biggest step forward on tackling climate change since the 2015 Paris agreement. However, there was no explicit commitment to phase out or even ‘phase down’ fossil fuels. Many scientists, climate interest groups and even governments had called for such a commitment. What is more, there was no agreement to transition away from fossil fuels for transport, agriculture or the production of plastics.
If the agreement is to be anything more than words, the commitment must now be translated into specific policy actions by governments. This is where the real test will come. It’s easy to make commitments; it’s much harder to put them into practice with policy measures that are bound to impose costs on various groups of people. What is more, there are powerful lobbies, such as the oil, coal and steel industries, which want to slow any transition away from fossil fuels – and many governments of oil producing countries which gain substantial revenues from oil production.
One test will come in two years’ time at the COP30 summit in the Amazonian city of Belém, Brazil. At that summit, countries must present new nationally determined commitments that are economy-wide, cover all greenhouse gases and are fully aligned with the 1.5°C temperature limit. This will require specific targets to be announced and the measures required to achieve them. Also, it is hoped that by then there will be an agreement to phase out fossil fuels and not just to ‘transition away’ from them.
Reasons for hope
Despite the unwillingness of many countries, especially the oil and coal producing countries, to phase out fossil fuels, there are reasons for hope that global warming may be halted and eventually even reversed. Damage will have been done and some tipping points may have been reached, but further tipping points may be averted.
The first reason is technological advance. Research, development and investment in zero carbon technologies is advancing rapidly. As we have seen, power generation from wind and solar is now cheaper than from fossil fuels. And this cost difference is likely to grow as technology advances further. This positive tipping point is becoming more rapid. Other technological advances in transport and industry will further the shift towards renewables and other advances will economise on the use of power.
The second is changing attitudes. With the environment being increasingly included in educational syllabuses around the world and with greater stress on the problems of climate change in the media, with frequent items in the news and with programmes such as the three series of Planet Earth, people are becoming more aware of the implications of climate change and how their actions contribute towards the problem. People are likely to put increasing pressure on businesses and governments to take action. Growing awareness of the environmental impact of their actions is also affecting people’s choices. The negative externalities are thus being reduced and may even become positive ones.
Articles
- Global Tipping Points
University of Exeter, Global Systems Institute, Timothy M. Lenton et al. (6/12/23)
- Report: Pivotal moment for humanity as tipping point threats and opportunities accelerate
Phys.org (6/12/23)
- Earth is closing in on catastrophic climate ‘tipping points’, over 200 scientists warn
Independent, Vishwam Sankaran (6/12/23)
- Earth on verge of five catastrophic climate tipping points, scientists warn
The Guardian, Ajit Niranjan (6/12/23)
- Cop28: King Charles warns of ‘vast, frightening experiment’ on natural world
The Guardian, Fiona Harvey, Nina Lakhani, Aletha Adu, Damian Carrington, Patrick Greenfield and Oliver Milman (1/12/23)
- UK likely to miss Paris climate targets by wide margin, analysis shows
The Guardian, Fiona Harvey (5/12/23)
- Water and the High Price of Bad Economics
Project Syndicate, Mariana Mazzucato , Partha Dasgupta, Nicholas Stern, and Johan Rockström (1/12/23)
- Fossil fuels: Can humanity really kick its addiction?
BBC News, Justin Rowlatt (10/12/23)
- Five climate change solutions under the spotlight at COP28
BBC News, Mark Poynting (6/12/23)
- COP28: Five reasons for optimism on climate
BBC News, Matt McGrath (8/12/23)
- COP28 Agreement Signals “Beginning of the End” of the Fossil Fuel Era
UN Climate Press Release (13/12/23)
- COP28 climate summit ends with deal to transition away from fossil fuels
CNBC, Ruxandra Iordache and Sam Meredith (13/12/23)
- Cop28 landmark deal agreed to ‘transition away’ from fossil fuels
The Guardian, Adam Morton, Fiona Harvey and Patrick Greenfield (13/12/23)
- COP28 draft agreement drops phaseout of fossil fuels
Financial Times, Attracta Mooney, Aime Williams and Alice Hancock (13/12/23)
- Examining COP28’s potential impact on climate change
BBC News, Matt McGrath (13/12/23)
- Cop28 failed to halt fossil fuels’ deadly expansion plans – so what now?
The Guardian, Damian Carrington (14/12/23)
- The momentum of the solar energy transition
Nature Communications, Femke Nijsse, Jean-Francois Mercure, Nadia Ameli, Francesca Larosa, Sumit Kothari, Jamie Rickman, Pim Vercoulen and Hector Pollitt (17/10/23)
COP28: Bill Gates on climate optimism, wealth and the human condition
BBC News on YouTube, Bill Gates (2/12/23)
- From the Paris agreement to COP28, how oil and gas giants try to influence the global climate agenda
The Conversation, Alain Naef (8/12/23)
- COP28: Phasedown or Phaseout, Fossil Fuels Must be Addressed to Meet 1.5C Goal
Forbes, Felicia Jackson (5/12/23)
Questions
- Use a diagram to demonstrate the effects of negative externalities in production on the level of output and how this differs from the optimum level.
- Use another diagram to demonstrate the effects of negative externalities in consumption on the level of consumption and how this differs from the optimum level.
- What was agreed at COP28?
- What incentives were included in the agreement to ensure countries stick to the agreement? Were they likely to be sufficient?
- What can governments do to encourage positive environmental tipping points?
- How may carbon taxes be used to tackle global warming? Are they an efficient policy instrument?
- What can be done to change people’s attitudes towards their own carbon emissions?