Economists use game theory to understand decision making where the outcome for an economic actor – individual, firm, government, etc. – depends on the actions and reactions of other actors. It models how rational actors make optimal decisions based on their expectations about such actions and reactions of competitors. Sometimes these expectations will be based on considerable knowledge; sometimes they will be based on hunch or the degree of optimism or pessimism.
Perhaps the most famous game is the prisoners’ dilemma. This is where two or more firms (or people) independently attempt to choose the best strategy, thinking about how their rivals are likely to react. But they end up in a worse position than if they had co-operated in the first place. For example, if a firm is considering cutting price, it would gain market share if the other firm does not cut price; in such a scenario it is likely to gain by cutting price. If, however, the other firm is expected to cut its price, the first firm will have to cut price itself to avoid losing market share; in this scenario it will also cut price. Assuming the other firm reasons the same, the outcome is likely to be a price war, with both firms losing profit. However, if they both colluded to maintain prices or even raise them (assuming they can evade any legal restrictions on collusion), they will both gain.
Another example is the game of chicken. This is where two or more actors engage in brinkmanship, hoping that the other actor(s) will give in first. Take the above example of a price war. Assume that two firms are engaging in price cutting. They know that this will damage their short-term profit. But each hopes that the other will give up first and may then be willing to collude or, better still, be driven out of business. If either firm thinks it can win the game, it will reason that short-term pain is justified by long-term gain.
The war in Iran
A game of chicken is currently being ‘played’ by the USA and Iran. Iran is blocking the Strait of Hormuz; the USA is blockading Iranian ports, preventing ships from arriving or leaving. Both policies inflict economic pain. Blocking the Strait of Hormuz has driven up oil and gas prices and the prices of many other products exported through the Strait – products such as fertilisers, plastics, petrochemicals, sulphur, methanol and helium.
Each side hopes that the economic pain inflicted on the other will cause it to give up first.
But the game is ‘asymmetric’: the costs of continuing the blockades are different for each side and thus the pressures on each side to concede differ. For Iran, the blockade of its ports is massively curtailing its exports and is doing huge damage to its economy, already battered by bombing. But the war has so far seemed to allow the Iranian authorities to tighten their political grip and they may be prepared to play the ‘long game’ by rallying the Iranian population against the US and Israeli assault. The authorities may calculate that the Iranian people will be prepared to endure greater hardship for some time.
The USA is facing a much lower economic cost. Much of the hardship from the effective closure of the Strait of Hormuz is being borne by other countries. Energy and fertiliser shortages and the resulting rise in price of these critical inputs threaten a humanitarian disaster in some of the poorest countries. Harvests will be down, as will GDP; food prices will soar. There will be widespread economic hardship across Africa and much of Asia, particularly in those countries struggling with existing high debt burdens.
But for Donald Trump and his administration, those costs are likely to be seen as important only in so far as they affect the USA. However, oil prices are determined in international markets and, despite the US economy gaining from higher oil prices as the USA is a net exporter, the price of fuel to the US consumer has risen substantially. Petrol prices in the USA have risen some 45% since the start of the war and jet fuel prices have doubled, driving up air fares. With the prices of other key products, such as medicines, clothing and electronics increasing too, US inflation is now rising – aggravated by the effects of the tariffs on many products. These costs matter to the US consumer and, with mid-term elections approaching and with Donald Trump’s approval rate plummeting, the USA is likely to be more sensitive to short-term economic costs than Iran.
But the USA poses a much greater military threat to Iran than vice versa and this is seen in the USA as a major advantage in this high-stakes game of chicken. But the Iranian authorities’ willingness to endure further military strikes for what they see as long-term gain, may make them unlikely to concede first.
Podcast and video
Articles
- Chicken
Stanford University, Janet Chen, Su-I Lu and Dan Vekhter
- Who will blink first as the Iran war hits the world economy?
CNN, Nic Robertson (23/4/26)
- Game theory explains why the US’s goals in Iran keep changing
New Scientist, Petros Sekeris (21/4/26)
- The Islamabad Game: From Lose-Lose to Win-Win in the Iran War
Times of Israeil, Vincent James Hoope (28/4/26)
- Deadly game they’re playing: Why Iran, Israel, and the US can’t stop escalating
The Business Standard, Bangladesh, Mohammad Omar Farooq (29/4/26)
- The Middle East’s game of chicken
Funds Global MENA, Raphael Olszyna-Marzys (27/4/26)
- The Strait of Hormuz shows how everything is now about leverage
The Conversation, Renaud Foucart (22/4/26)
Questions
- Explain the prisoners’ dilemma game and explain what is meant by the Nash equilibrium in the game.
- What is the Nash equilibrium of a game of chicken?
- Explain the asymmetries in the ‘game’ being ‘played’ by the USA, Israel and Iran?
- What other actors are there in the ‘game’ and do they play any significant role?
- How important is information and understanding held by the USA, Israeli and Iran about the likely consequences of their actions?
- What can mediators, such as Pakistan, do to de-escalate the situation?
- What are the likely long-term costs to the global economy if the blocking of the Strait of Hormuz persists for a number of months?
With relentless bombing of Iran by Israel and the USA, and with Iranian counterattacks on Gulf states, the costs of the war are mounting. The most obvious are in terms of human lives, injuries and suffering. But there are significant economic costs too. Some of these are immediate, such as the rising price of oil and hence the costs of fuel, or the fall in stock market prices. Some will be longer term, depending on how the war develops. For example, prices could rise more generally as supply chains are disrupted.
The impacts will vary across the world and across markets. The most obvious markets to be affected are those where significant supply comes from the Persian Gulf. Approximately 20% of total global oil consumption passes through the Strait of Hormuz, which connects the Persian Gulf with the Arabian Sea and the Indian Ocean.
Oil prices rose considerably in the days following the start of the war on 28 February, with Brent crude, a key measure of international oil prices, rising from $71.3 on 27 February to a peak of $119.4 per barrel by the morning of 9 March – a rise of 67%. It was possible that they would rise even further in the short term. However, prices fell back substantially later on 9 March after G7 finance ministers declared that the group ‘stands ready’ to release oil from strategic reserves if needed. By late in the day, the price had fallen to below $85. (Click here for a PowerPoint of the chart.)
However, despite the announcement on 11 March that 32 countries had agreed to release 400m barrels of oil reserves, oil prices began rising again and reached $100 on 12 March after three tankers had been struck in the Gulf, two of them close to the Strait of Hormuz. With Iran pledging to keep the Strait closed, there were worries that the release of oil reserves would provide only temporary relief. Just over 20m barrels of oil normally pass through the Strait of Hormuz. The 400m barrels released from storage is the equivalent, therefore, of only 20 days’ worth of lost oil from the Gulf.

Not only did oil prices rise, but the price became much more volatile as markets reacted to the news on a continuous basis. Intra-day fluctuations in oil prices of several percentage points became typical, reflecting shifting expectations. The second chart shows daily fluctuations, with the highest and lowest prices for each day shown, along with the closing price. (Click here for a PowerPoint.)
The biggest fluctuation had been on 9 March when fears of the closing of the Strait of Hormuz saw the price of Brent crude rising to nearly $120 but falling to around $84 later in the day (a fall of around 30%) after the G7 announcement about releasing reserves.
There was another big fluctuation on 23 March. The previous day (Sunday), President Trump threatened to bomb Iran’s power plants if Iran did not allow free passage of ships through the Strait of Hormuz. Iran threatened to retaliate by striking Gulf countries’ energy and water systems. In early trading on Monday 23rd, Brent crude rose to over $115 per barrel. But later that day, Trump said that there had been constructive talks between the USA and Iran. The oil price immediately dropped to around $96 – a fall of 17% – before settling at around $100.
Rising oil prices will drive up inflation. For those countries with a heavy dependence on Gulf oil, particularly countries in Asia, there could be significant supply problems. For oil exporters in the Persian Gulf, with tankers unable to traverse the Strait of Hormuz, the economic impact is huge. Oil exporters outside the Gulf, such as Russia, Norway and Canada, however, will gain from the higher prices. Clearly the size of these effects will depend on how long the conflict continues and how long the Strait of Hormuz remains closed.
And it is not just oil that is affected. Other products, such as liquified natural gas (LNG), petrochemicals, industrial materials, fertilizers for food production, medicines, helium for microchip production, metals and minerals are transported through the Strait of Hormuz. Gulf countries import much of their food through the Strait. On 18 March, Israel struck Iran’s huge South Pars gas field off the Gulf coast. This is the largest gas field in the world and is a major source of export revenue for Iran. Iran responded by striking the Qatari gas hub in Ras Laffan. Donald Trump responded by threatening to ‘blow up’ the entire Iranian South Pars gas field if Iran made further strikes on Qatar. The effect of this escalation was to drive oil and gas prices up further. By the week ending 20 March, the oil price closed at just over $112 per barrel.
Cuts in supplies of oil and other products represent an adverse supply shock. Such shocks push up prices (cost-push inflation), while adversely affecting aggregate output. This can lead to stagflation – a combination of higher inflation and stagnation or even falling output. Central banks with a simple mandate to keep inflation to a target are likely to raise interest rates, or at least delay in reducing them. In the USA, with a dual mandate of controlling inflation but also maximising employment, the response may be less deflationary, depending on the judgement of the Federal Reserve.
Uncertainty
There is great uncertainty about how long the conflict will last. There is also a lack of clarity and consistency from the US administration about its war aims. This uncertainty has affected financial markets, which have seen considerable volatility. Stock markets have seen widespread falls, with airline, travel and AI-heavy stocks being particularly vulnerable.
If the war is concluded relatively swiftly, the economic effects could be relatively small. If the war continues, and especially if the Gulf countries are drawn further into the conflict and if the conflict spreads to other countries, the economic effects could be much more substantial. A prolonged conflict could see oil prices remaining above $100 per barrel, potentially increasing global inflation by 1 percentage point or more. This would slow or halt the move by central banks to cut rates and thereby reduce global economic growth – potentially, as we have seen, leading to stagflation.
The uncertainty was reflected in the decision of the Fed to keep interest rates unchanged at its meeting on 17/18 March. The Fed has the twin targets of keeping inflation close to 2% and maximising employment. Fed Chair, Jay Powell, acknowledged the current tension between the two goals: ‘upward risks for inflation and downward risks for employment, and that puts us in a difficult situation’. He also recognised that the future for inflation and the economy was highly uncertain as the war developed. This made interest rate setting difficult.
Then there is the issue of a potential new international refugee crisis. If the economic and political system in Iran deteriorates rapidly, this could trigger a wave of migration to neighbouring countries, such as Turkey, already hosting large numbers of refugees. Many could seek sanctuary further afield in Europe, with several countries already facing a backlash against immigration. The political and economic effects of this on host countries could be significant – but as yet, highly uncertain.
Articles
- Assessing the global economic impact of the Middle East war
ING, Carsten Brzeski, Warren Patterson, James Knightley and Deepali Bhargava (5/3/26)
- How the Hormuz closure could affect food, medicines and smartphones
BBC News Verify, Ben Chu (27/3/26)
- How will the Iran war affect the global economy?
Chatham House, Neil Shearing (6/3/26)
- ‘The stakes are enormous’: how a prolonged Iran war could shock the global economy
The Guardian, Richard Partington (22/3/26)
- Iran war is latest threat to a global economy rattled by Trump
Aljazeera, John Power (7/3/26)
- Why an Iran war inflation shock could wreck global economic recovery
The Guardian, Phillip Inman and Kalyeena Makortoff (8/3/26)
- Why has the Iran war sparked fears of stagflation for the global economy?
The Guardian, Luca Ittimani (9/2/26)
- Why the price of oil matters more than you might think
BBC News, Natalie Sherman and Mitchell Labiak (10/3/26)
- Strait of Hormuz: Factsheet
IEA (February 2026)
- Could this energy crisis be worse for the global economy than COVID?
The Conversation, Adi Imsirovic (26/3/26)
- Faisal Islam: Oil price spiral may be slowed but not stopped by G7 emergency move
BBC News, Faisal Islam (9/3/26)
- What on earth is going on with the oil price?
BBC News, Jemma Crew (12/3/26)
- Asia scrambles to confront energy crisis unleashed by Iran war – with no end in sight
The Guardian, Callum Jones (12/3/26)
- The grim choice facing the Trump administration: Economic or naval collapse?
CNN, Phil Mattingly and Zachary Cohen (9/3/26)
- Israel strikes Iran’s South Pars gasfield hours after forces kill intelligence minister
The Guardian, Lorenzo Tondo and William Christou (18/3/26)
- What Fed Chair Jerome Powell said — and didn’t say — about the oil crisis
Yahoo Finance, Jake Conley (19/3/26)
- What strikes on the world’s largest natural gas sites could do to the global economy
CNN, Hanna Ziady (19/3/26)
- How the Iran Conflict May Fuel a New International Refugee Crisis
Forbes, Andy J Semotiuk (5/3/26)
- Iran’s neighbours brace for fallout as war threatens new refugee crisis
Aljazeera, Abid Hussain (17/3/26)
- Two months into the Iran war, almost everybody is a loser
CNN, Ivana Kottasová (2/5/26)
Data
Report
Questions
- Who are the biggest gainers and losers from disruption to oil supplies from the Persian Gulf?
- Illustrate the effect of the current oil price shock on an aggregate demand and supply diagram (either static or dynamic).
- Why is the Iranian war likely to be less damaging to the European economy than the Ukrainian war has been?
- Why have AI-related stock prices been vulnerable to the uncertainty caused by the Iranian war?
- How have the Bank of England and the Federal Reserve Bank responded to higher oil prices and the broader economic effects of the war? Why might their responses be different in the coming months?
- What is the likely impact of the Iranian war on global economic recovery?
- How might the Iranian war affect global economic alliances?
- How is the current oil price shock likely to affect the eurozone? Will it be different from the oil price shock that followed the Russian invasion of Ukraine?
- What are the likely economic effects of large-scale migration caused by the war?
Three recent reports (see links below) have suggested that US consumers and businesses pay most of the tariffs imposed by the second Trump administration. The percentage varies from around 86% to 96%. US customs revenue surged by approximately $200 billion in 2025, but this was a tax paid almost entirely by US consumers and businesses. Foreign suppliers largely maintained their (pre-tariff) prices. They took a hit in terms of reduced volumes rather than reduced pre-tariff prices.
The incidence of a tariff between consumers, domestic importers and overseas producers will depend on price elasticities of demand and supply. The following diagram shows a product where the importing country is large enough to have a degree of market power, which will normally be the case with the USA. The greater its buying power, the flatter will be its demand curve, showing that the foreign supplier will have little influence on the price. With no tariff, the equilibrium price paid by importers will be at point a, where demand equals supply. Q1 would be imported at a price of P1.
Imposition of a tariff will shift the supply curve upwards by the amount of the tariff. The new equilibrium price paid by importers will be at point b, where the new supply curve crosses the demand curve. Importers thus now pay a post-tariff price of P2: an effective rise in price of P2 minus P1. Foreign exporters receive P3, which is what they are paid by importers after the tariff has been paid.
The consumer price will be above P2 as that includes a mark-up by US businesses on top of the price they pay to import the product. Importers may bear some of the increase in price and not pass the full amount onto consumers, depending on competition and their ability to absorb cost increases.
President Trump argued that there would be very little rise in price from the tariffs and that overseas suppliers would bear the brunt of the tariffs. Indeed, recently he has argued that this must be the case as US inflation has been falling. In response, critics maintain that the rate of inflation would have fallen more without the tariffs and that current prices would be lower than they are. Also, if US importing firms or retailers bear some of the increased cost, even though this helps to dampen the price rise, their lower profits could damage investment and employment.

The Reports
The first report is from the New York Fed (one of the regional branches of the Federal Reserve Bank). It examines the effect of tariffs imposed in 2025, over three periods: (i) January to August, (ii) September to October, and (iii) November. In the first period, 94% of the tariffs were paid by US importers and 6% by foreign exports; in the second period, the figures were 92% and 8% and in the third period, 86% and 14%.
The second report is The Budget and Economic Outlook: 2026 to 2036 from the Congressional Budget Office. Box 2-1 notes that, as of November 2025, ‘the effective tariff rate was about 13 percentage points higher than the roughly 2 percent rate on imports in 2024’. Its analysis suggests that 95% of the tariffs will be borne by importers. Of these higher import prices, 30% will be borne by US businesses, largely through reduced profit margins, and 70% by consumers through higher prices. This will also allow many businesses which produce goods that compete with foreign imports to ‘increase their prices because of the decline in competition from abroad and the increased demand for tariff-free domestic goods’.
The third report is from the Kiel Insitut. In its Policy Brief, Americaʼs Own Goal: Who Pays the Tariffs?, it finds that US importers and consumers bear 96% of the cost of the 2025 tariffs, with foreign exporters absorbing only about 4%. It bases it findings on shipment-level data covering over 25 million transactions valued at nearly $4 trillion. This also shows that exports to the USA declined as foreign exporters preferred to reduce volumes rather than absorbing the tariffs.
The tariffs raised some $200 billion in 2025, around 3.8% of Federal tax receipts. But, as we have seen, this was paid largely by US consumers and business. It goes some way to offsetting the annual cut in tax revenues of around $450 to $520 billion per year from the tax cuts, largely to the better off, in Trump’s ‘One Big Beautiful Bill’.
Reports
Aricles
- NY Fed report says Americans pay for almost all of Trump’s tariffs
Reuters, Michael S. Derby (12/2/25)
- A year in, it’s official: Americans, not foreigners, are paying for Trump’s tariffs
CNN, Allison Morrow (12/2/26)
- Costs from Trump’s tariffs paid mainly by US firms and consumers, NY Fed says
BBC News, Kali Hays (13/2/26)
- Consumers and businesses paid nearly 90% of Trump tariffs in 2025, new analysis found
CBS News, Megan Cerullo (12/2/26)
- New Studies Challenge Who Really Pays for Tariffs
Investopedia, Diccon Hyatt (12/2/26)
- Trump Tariffs: Tracking the Economic Impact of the Trump Trade War
Tax Foundation, Erica York and Alex Durante (6/2/26)
- Who Is Paying the Trump Tariffs?
Paul Krugman (15/2/26)
Questions
- Summarise the findings of the three reports (but just Box 2-1 of the Congressional Budget Office one).
- Assess the argument that protectionism leads to inefficiency in the protected industries.
- Under what circumstances would exporters to the USA absorb a high percentage of tariff increases? Consider questions of elasticity.
- Can tariffs ever be justified on efficiency grounds?
- Can tariffs be justified as a bargaining ploy? Can they be used as a means of achieving freer and fairer trade?
- Read the blog, President Reagan on tariffs and summarise President Reagan’s arguments. Are they still relevant today?
- Consider the arguments for and against the EU raising tariffs on US goods.
Precious metals, such as gold, silver and platinum, are seen as safe havens by investors in uncertain times. With the on-off nature of Donald Trump’s tariffs, with ongoing wars, such as the war in Ukraine, and with threats of US action in Iran, with inflation slow to fall and pressure by the Trump administration on the Federal Reserve to make precipitant cuts in interest rates, investors have flocked to precious metals.
Precious metals peaked in late January 2026. Compared with just four months earlier, gold was up by 48%, platinum by 76% and silver by a massive 162%. Silver and platinum were also boosted by their industrial uses. Silver has excellent conductive properties and is used for electronics, AI, solar energy (photovoltaic cells), chemical catalysts and medical equipment. Over 50% of its consumption is for industrial purposes. Platinum is used as a catalyst in catalytic converters to reduce exhaust emissions, in medical devices, chemical processing, oil refining, electronics and glass manufacturing.
The rise was fuelled by speculation, which gathered momentum in December and January. But then the prices of all three metals fell dramatically on Friday 30 January and a bit more on 2 February. Despite a moderate bounce back on 3 February, the prices then fell again and by the end of 5 February, gold had fallen by 15%, platinum by 30% and silver by a massive 42% from the peak.

Figure 1 illustrates the effect of speculation on the rise in price of a precious metal, such as silver. Assume that demand rises from D0 to D1 for the reasons given above. Equilibrium moves from point a to point b and the price rises from P1 to P2. Seeing the price rising, holders of the metal wait until the price rises further before selling. Supply shifts from S1 to S2. Potential purchasers of the metal, anticipating a further rise in price, buy now before the price does rise. Demand shifts from D1 to D2. As a result, equilibrium moves from point b to point c and price rises to P3.
Figure 2 illustrates the effect of speculation on the subsequent fall in prices triggered by a belief that price will fall. Speculative selling shifts the supply curve from S2 to S3. Potential demanders hold back and the demand curve shifts from D2 to D3. Equilibrium moves to point d and price falls from P3 to P4. (Click here for a PowerPoint of the two figures.)
But why did prices fall so dramatically? The first reason was that analysts were beginning to argue that the exuberance of investors had led the price of all three metals to overshoot the fundamental balance of supply and demand. Once a tipping point arrived, people sold quickly to lock in the gains they had made over previous weeks. This profit taking caused prices to plummet as speculation of further falls drove prices lower.
So what was the tipping point? This was the appointment by Donald Trump of Kevin Warsh as the new Chair of the Federal Reserve to take over from Jerome Powell when his tenure comes to an end in May this year.
It was expected that Trump would appoint someone much more willing to cut interest rates and this worried investors, who feared that inflation would rise again. This uncertainty drove demand for precious metals, which are seen as a safe haven. But Kevin Walsh is viewed as hawkish on monetary policy and less likely to slash interest rates than other possible choices for Chair. This triggered the fall in precious metal prices.
But the main factors that drove the demand for the metals still exist. There is still uncertainty, still an increased demand from central banks for gold, still a growing demand for silver and platinum for industrial uses. The next day, 3 February, it seemed that the prices of all three metals had over-corrected. Investors started buying again at the lower prices and consequently prices rose again – once more fuelled by speculation. Gold rose by 6.1%, platinum by 7.9% and silver by 11.6%.
Articles
Data
Questions
- What has happened to the price of silver since this blog was written? Use a demand and supply diagram to illustrate this.
- Identify the factors that affect the demand for and supply of (a) silver; (b) gold.
- What determines the elasticity of supply of silver (a) in total; (b) to the market?
- Choose another commodity other than the three metals considered in this blog. Find out what has happened to their prices over the past 12 months and explain why these price movements have occurred.
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.
The agreement
The agreement reached at the end of the conference marked relatively small progress. There was agreement to increase finance from developed to developing countries to help them adapt to climate change. This would triple to $120bn per year, up from the previously agreed doubling, but the target date was pushed back to 2035 from the previously agreed 2030.
By the end of the conference, 122 of the 197 countries had submitted a new NDC – still 75 countries short, although others are expected.
The conference also agreed to establish a ‘just transition mechanism (JTM)’ to ‘enhance international cooperation, technical assistance, capacity-building and knowledge-sharing, and enable equitable, inclusive just transitions’. However, this is voluntary and no funding was attached, but it could act as the basis for future funding.
The biggest failure of the conference was probably the lack of agreement on phasing out of fossil fuels. This is not surprising given the opposition of the major oil producers. The hope is that the reduction in costs of renewable energy will drive the process anyway – a process that China is keen to accelerate with its investment in solar power and other renewable energy. One hopeful development, however, was the pledging of more than $9bn to halt deforestation, a major source of global warming. (See the Travers Smith article at the end of the Articles list below for a very useful summary of the outcome.)
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)
Post-agreement
- Belém: yet another cop out
Zero Hour, Allan Gray (25/11/25)
- Cop30’s watered-down agreements will do little for an ecosystem at tipping point
The Guardian, Fiona Harvey, Jonathan Watts, Damien Gayle and Damian Carrington (22/11/25)
- COP30: Five key takeaways from a deeply divisive climate summit
BBC News, Justin Rowlatt and Matt McGrath, (25/11/25)
- COP30: What were the key outcomes?
Travers Smith (1/12/25)
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?