The Cambridge "Green Blue" competition to reduce emissions / Feb 2025

Carl Edward Rasmussen recently gave a great talk in our group about his thoughts on mechanisms against climate change. He persuasively argued that the Paris Agreement was doing more harm than good by giving the illusion of being a concrete agreement, but is in reality a huge distraction. Our actual emissions have increased since the Paris agreement was signed!

Carl argues that a climate system ultimately only responds to collective actions, and without a global cooperative incentive each nation will spring back to their own isolated short-term incentives that lead to an increase in fossil fuel burning. He has just published the "Themis Mechanism" as a simple alternative for equitable global emission reduction (long form).

This got me brainstorming with Carl about how to test his theories out and we came up with an idea that is either terrible or awesome; please read on and judge appropriately. I think we should take advantage of Cambridge's unique structure to trial the Themis mechanism via a new competitive decarbonisation sporting league among Colleges that I dub the "Cambridge Green Blue". Given the Chancellor's recent unveiling of an innovation corridor between Oxford and Cambridge, the timing could not be better for an initiative like this. (TL;DR sign up at the bottom of this post if you'd like to participate)

The basics of the Themis mechanism

First, let's understand what Carl is proposing, which is built on three foundations:

• Our atmosphere is a shared resource, a commons. Fossil fuel users benefit fully from fuel consumption, while the CO2 cost is spread globally. This dilution effect makes continued use rational for individuals but collectively disastrous. [...] To prevent this, we must cooperate to guarantee positive climate results.
• The root cause of climate change is the failure to account for the true cost of emissions. By treating the atmosphere as a free resource, we encourage overexploitation. Themis corrects this unpriced externality by pricing greenhouse gas emissions.
• Effective cooperation requires a fair guiding principle. Themis upholds equity: that our atmospheric resources should be shared equally between all humans. -- Carl Edward Rasmussen, The Themis Mechanism

As I noted last week, most tech companies regularly break future carbon pledges due to competitive pressure. So it's good to see that Themis requires only immediate commitments rather than long-term pledges which are impossible to police. Instead of forcing unwilling participants to join, Themis is a coalition in which partners check on each other, learn by doing, and build up mutual trust.

The core scheme itself is based on a value P_y which is the price of emitting a single ton of CO2 into the atmosphere in year y. Here's how it works:

1. Every year y there is a price P_y that all nations agree to.
2. At year end, each members pays P_y times their emissions into a common pool.
3. The pool is immediately redistributed to members in proportion to their population.
4. Each member votes on P_y+1 and the median result decides next year's price.

This mechanism only depends on per-capita emissions for one year, and not on any future pledges or historic emissions. If a country has above average per capita emissions, then they pay into the common pool. If they are below average per capita, then the country benefits from payments from the pool. The system permits co-existence with any other carbon reduction efforts, and works with a non-exhaustive pool of nations participating.

Will Themis be more effective than Paris?

The main reason Themis might fail is that participating in the league disadvantages the participants vs those just continuing with business-as-usual. The economics theory behind Themis is similar to a Pigouvian tax which dates back to a century ago, when the Cambridge economist Arthur Pigou suggested in 1920 that a tax equal to the external cost of pollution could align private costs with social costs. This idea also works for discounting future actions, and is the basis for some of our own work on pricing impermanent but delayed emissions.

From an economic theory perspective, Pigou and the other prominent Cambridge economist at the time JM Keynes^[1] had deep disagreements. Keynes argued for higher interest rates to boost aggregate growth, while Pigou wanted to give people an increase in real wealth relative to prices. Both of their approaches ultimately lost out by the 1980s as free market economics ruled supreme instead, leading to the current "grow, emit and die" competitive spiral of doom we find ourselves in. However, Pigou's theories are clearly ones we should revisit today in light of Themis: by raising the cost of emitting via taxes (or Themis contributions) we can incentivise countries to reduce pollution or decarbonise instead of treating the atmosphere as a free sink to dump into.

A modern counterpoint to the "lack of competitiveness" argument from participating in a emissions reduction competition is the increasing evidence of runaway tipping points that might suddenly need everyone to decarbonise really quickly. Katherine Hayhoe, the chief scientist at TNC observes that we can't adapt our way out of this climate crisis due to the sheer magnitude of change that will occur if we continue to emit.

Our infrastructure, worth trillions of dollars, built over decades, was built for a planet that no longer exists [...] - Katherine Hayhoe, The Guardian 2022

This is a pragmatic point in favour of countries joining Themis, since participation strengthens their economic infrastructure towards decarbonisation. By joining, countries can trade off some short term losses in their economy with being well hedged for either a "sudden" black swan climate tipping point that requires rapid change in their societal infrastructure, and it also gives them a long-term advantage heading into the inevitable electric future. So perhaps the fact that things are now much worse since Paris could force the emergence of cooperative groups who wish to prepare for sudden change.

As Carl Edward Rasmussen also notes in his Themis proposal, there is consensus among climate scientists that we must cooperate in the planetary commons if we are to succeed. But his proposal seems overwhelmingly difficult to evaluate in a political climate that is moving away from global cooperation. There must be a way to try some of these ideas out at a smaller scale, and especially locally in our sleepy University town!

Cooperation through sport and games

One area where nations have remained cooperative through no clear immediate financial gain is that of competitive sport. We just had the Paris Olympics with almost every nation in the world competing for no good reason other than a desire to win. And they're not seeking to win money as in most other areas of competition; instead it's just virtual credit in the form of medal tables that are celebrated from the largest to the smallest countries!

Sporting events such as the Olympics are highly structured events with clear rules dictating almost every aspect. An interesting consequence of decoupling the rules of the games from direct financial incentives is that many sports are not zero-sum games. In rugby union or football for example, the winner gains more than the loser loses. While this structure can encourage match-fixing due to the asymmetry, participants also build trust amongst themselves over the years, for example via promotion through divisions. Game theorists often note how stable cooperation emerges in infinitely repeated games. Sports seasons are simply repeated competitions; over time, codes of conduct evolve and become self-policing agreements for mutual benefit (avoiding injuries, preserving dignity in loss, etc). There are clear lessons for the Themis mechanism here, as it also needs to establish long-term cooperation deep into the next century until total CO2 levels decline.

Away from physical sports, we also see similar scoring dynamics in boardgames! There is a whole genre of semi-competitive boardgames such as Archipelago which are "competitive games that everyone can lose". This sounds a lot like Themis; we want to be able to stave off emissions disaster, but otherwise be the top dog in our league for every other aspect of our societies! The game rules must be structured so that even selfish players find it in their interest to cooperate to avoid losing. In Archipelago, the rule is simple: if instability within the game hits a certain point, all players lose, which forces even the leader to sometimes help the laggard to save themselves.^[2]

Enter the Cambridge Green Blue

So how is this relevant to evaluating the global Themis mechanism from earlier? Everything global must start locally, so I propose a new semi-competitive league here in Cambridge, with willing Colleges as participants, and with virtual points instead of using real currency. And just like the two century old tradition, we should make this sufficiently competitive to gain a coveted sporting blue! To give you some context, being really good at tiddlywinks can gain you a quarter blue.

In the rest of this post, I've written up the structure of this league with Ostrom's principles in mind, by treating the CO2 management problem as a common pool resource. Cambridge Colleges have been around for centuries and so naturally appreciate the long perspective required; Pembroke was founded in 1347. Our collective collegiate goal is to urgently reduce CO2e that accumulate in the atmosphere and contribute to climate change for hundreds of years. This requires cooperation and learning from each other, but also a certain drive to do better than each other to get to the goal as quickly as we can.

What do we measure in this league?

The three key sources of carbon emissions this league would track would initially come from food, heating and travel, noting again that we are only measuring this year's reductions and emissions, not historic or future pledges. We need to design specific mechanisms for each of these, but I'll just sketch out what makes measuring each of these "interesting".

Food consumption and waste

Students, Fellows, visitors and staff all eat a lot of food in the Colleges from all over the world. Communal dining is so central to the Cambridge College experience that it is mentioned in many College statutes as part of our charitable purpose.

In furtherance of the College’s purposes, Fellows shall be entitled to dine daily free of charge at common table. -- Pembroke College Statutes presented to Her Majesty in 2009

Since thousands of meals go through a typical College every day, identifying pragmatic sources of emissions reductions is very important. In a recent committee meeting at Pembroke College, I was incredibly pleased to hear that we've reduced food waste from the kitchens down to just one or two meals a day (which, considering the vast number of meals served is hugely impressive). And similarly, Darwin College reported on the recent plant based May Ball which was a rather fine party, and the world did not end due to black tie attendees being unable to find a sausage roll. How can we communicate the lessons learnt from the catering teams here to other Colleges? The CGB allows us to rank and categorise these initiatives!

Research, with much of it conducted here in Cambridge, shows us that key gains in food impacts come from reducing ruminant meat consumption and the corresponding damage to tropical forests full of biodiversity. Importantly, we're not trying to force every College member to suddenly become vegan, but instead provide sustainable and healthy options. Andrew Balmford and Theresa Marteau have both shown that nudging consumers such as Cambridge students and staff towards less damaging choices by default is entirely practical, without alienating those that insist on their meat'n'twoveg:

A study of over 94000 cafeteria meal choices has found that doubling the vegetarian options from 1-in-4 to 2-in-4 increased the proportion of plant-based purchases by between 40-80% without affecting overall food sales. -- Veg nudge. Impact of increasing vegetarian availability on meals (paper / followup)

The league does need some way to turn these initiatives into a points based system. This is where my colleague Thomas Ball's recent research is instructive. He's been working on quantifying the biodiversity cost of food imports, broken up by the food type. The CGB food points game could correlate consumption choices with where the food comes from and how much it is wasted, and so we could steadily work across Colleges on reducing our impact year-on-year.

Heating without fossil fuels

Turning off the natural gas flows in Colleges is a major challenge. We have some of the oldest buildings in the world around here, and much of the infrastructure is correspondingly aged. Pembroke has just spent a ton of cash on a communal heat pump for our new development in Mill Lane, which got me thinking about how this aspect of the CGB league could be based around this. The rules and regulations for heat pump installation in the UK are incredibly baroque, as Robert McQueen pointed out recently:

I have a neighbour who embarked on a planning application for a heat pump for his terraced house. There is a difference in ridiculous paperwork necessary simply to install <1m from the boundary compared to the presumed consent in permitted development. Of course now they are waiving that requirement but he's stuck half way through the process. I can't even imagine adding listed requirements into that

[...] due to be waived for permitted development - whether that tracks through to the full regulations is anyone's guess. They are already bafflingly inconsistent. -- Robert McQueen, Bluesky, Feb 2025

However, the Cambridge City Council isn't sitting still and has been working with the University on this. Ian Leslie pointed me to city-wide explorations into district heating networks for Cambridge that includes a phase 1 report that plots out what it might look like by using different Colleges as sinks and sources!

Darwin College also reports in their 2023 sustainability report the progress they've made on establishing heat pumps in the River Cam.

In 2022, in a collaboration with six other riverside Colleges, Mott MacDonald were commissioned to monitor water flow, depth and temperature at four locations on the river and to produce a detailed hydrology study. The report, delivered in 2023, confirms the considerable potential of the river to supply heat for space and hot water heating for the adjacent Colleges. -- Darwin sustainability report, 2023

And famously most recently, Kings College installed 400 solar panels on their world-famous chapel, despite opposition from Historic England. This sets a huge precedent for the rest of Cambridge to take similar action, and they deserve recognition for this from the CGB!

So this aspect of the CGB league could focus on building spatial connections across Colleges. Perhaps the College that brings the most benefit to its neighbours by contributing the most towards a district heating mechanism could win this round.

Reducing impact of international travel

Finally, lots of the Colleges do facilitate international travel, for a variety of reasons ranging from pedagogical to developmental. The most obvious one is when conducting in-person interviews, when candidates fly in from all over the world. Since the pandemic, there has been split opinion among Colleges about returning to in-person interviews or not, with Pembroke opting for in-person this year. While there are lots of good reasons to encourage in-person interactions, the carbon cost has been so low down in the discussion points in the meetings I've attended that it might as well not even be a factor. A CGB league might encourage us to tally up the scores across Colleges more systematically to factor in these costs into the overall decisionmaking.

The other opposite end of the spectrum is international air travel for conferences, which are thankfully quite rare as most of our business is conducted locally. We do host events here such as the SCCS student conservation conference that flies in young scholars from all over the world, but this is quite rightly justified as being essential as it brings together underrepresented young students from all over the world who find tremendous value from meeting each other. I've made more extensive notes on the topic of travel mitigation elsewhere in my note on carbon contributions.

Implementing the Cambridge Green Blue

I've hopefully convinced you that there quite a few interesting dimensions around which we could design our semi-competitive Cambridge Green Blue (CGB) league. I've avoided over-specifying the rules at this early juncture, since I want to bring in more people's thoughts and ideas first. However, here's a strawman attempt.

We treat the emission of CO2 into the atmosphere as a shared common pool resource (CPR); i.e. we can collectively only emit a limited amount if we are to avoid the worst effects of climate change. Cooperation on a global CPR should ideally happen on a global basis, however that current approach is inadequate. Therefore, we must locally initiate mechanisms which will build up into a global framework from the ground up. Cambridge Colleges are institutions for young people who will be greatly affected by climate change, and Colleges make decisions with long time horizons, and a body of scholars should represent intellectual leadership in a time of crises. Therefore Cambridge Colleges should be an ideal proving ground for exploring cooperative frameworks in practise!

The CGB would select its initial College membership and define baseline rules about how to measure emissions collectively, based around the first interest areas of travel, food and heating described above. Members will then write a rule book that follows the Themis mechanism to establish a virtual price for each tonne of emissions, and we will self-report progress monthly with points assigned to those who are beating their baselines of emissions reduction interventions. The league is used to collectively learn from those who are winning, and equalise the playing field in future seasons for the others to catch up.

Following Ostrom's principles, the league looks like this:

1. Define group boundaries and the contents of the CPR. The common pool resource we measure are CO2 emissions from the Cambridge Colleges. The goal is to reduce emissions year-on-year, and so "0" is defined as the previous year’s emissions, with any additional emissions reductions resulting in points awarded. The league therefore measures the CPR as "CO2e tonnes avoided" without getting into any historic or future plans, only what is happening this year.
2. Appropriation and provision of common resources. The Colleges all have initiatives to reduce their CO2e, and have agreed to cooperate towards this common goal. Membership of the league is voluntary, and we make the membership public. We reserve the right to laugh derisively at those Colleges who elect not to participate.
3. Collective-choice arrangements for resource appropriators to make decisions. The league will maintain a points database tracking emissions across heating, travel and food-related emissions reduction activities. The league will not be directly involved in individual College decision making, but we hope to recruit persons from the Colleges who may be involved in those activities in addition to their participation in the league.
4. Effective monitoring by monitors who are accountable to the appropriators. The league will self-report their emissions reductions monthly, and there will be a collective consensus formed on the CO2e measurements across the emissions reductions. The reporters are all part of the Cambridge Colleges, and so have access to internal channels to verify their own claims.
5. A scale of graduated sanctions for resource appropriators who violate community rules. As a voluntary league, we do not anticipate any incentive to cheat. Sanctions will first be redaction of those points from the table, followed by ejection from the league.
6. Mechanisms of conflict resolution that are cheap and of easy access. The league has monthly checkpoints where participants collectively score their emissions reductions. Disagreements about methodologies will be resolved at these meetings, which also aim to collectively educate each other about the diverse emissions reduction methods available.
7. Self-determination of the community recognised by higher-level authorities. Cambridge Colleges have committed to various net-zero targets. Therefore, the emissions reductions tracked by this league will eventually be incorporated into some broader net-zero reporting that apply at a national and international level. But for now, we just want to reduce the real amount year-on-year.
8. Organisation in the form of multiple layers of nested enterprises, with small local CPRs at the base level. Our hope is that the Cambridge Green Blue is the first league of many, with other organisations also following our template. To that end, we will make our rules templates available freely as an open-source rulesheet after the first round concludes successfully. When there are multiple organisations running their own leagues (come on Oxford!), we will build up a bigger collective framework for Themis participants, akin to a sporting governing body.

One very important aspect of this is to adopt a respectful "sportsmanship" rule to the relative ranking of Colleges, and not engage in shaming wars. There is a wide wealth disparity among the Cambridge Colleges, and we could adjust for this using the per-capita rules from the Themis mechanism. Ultimately, it's also about celebrating and learning from every participant and using the competition to spur us on, build each other up, and have fun doing so. We're all in this together.

Err, are you serious about this Anil?

Yeah, I think this is worth a try! I have recently joined the University's Environmental Sustainability Strategy committee, and I've found it extremely difficult to educate myself about the local initiatives going on (not because of any individual's fault, but because there are 31 separate constituent Colleges and University and townspeople sharing a fairly small area). If nothing else, this initiative will let us collectively bring together a wiki of all the positive actions happening across Cambridge. If it succeeds though, I'd like to spread the next iteration of the league to other Universities to run their own (I'm looking at you, Oxford), and see if we can turn this into a distributed game.

I was reading Andrew Balmford's book Wild Hope over the weekend, and his conclusion at the end was that we must not lose hope in our quest for a biodiverse, equitable world. And given the chaotic start to 2025, I can't think of a better place to start something new than within Cambridge, with our collegiate structure already providing a ready-made framework.

So what next? If you're interested in helping Carl Edward Rasmussen and me organise this, get in touch with either of us! I'm on academic sabbatical for a year from the summer, so I'll have loads of time. I'll edit this post with a list of first Colleges that have been in touch. We'll likely organise a pub get-together in early March (exact date to follow) to brainstorm about this without anyone interested.

This post is the result of many conversations around Cambridgeshire over the past year, ranging from a balmy summer dinner in Ely with Andrew Balmford and Theresa Marteau, chilly autumn cups of tea in my Pembroke office with Carl Edward Rasmussen and Carl Henrik Ek, to misty morning coffees at Pages with Melissa Leach and Michael Dales or at Espresso Lane with Eleanor Toye Scott, to cosy pubs with Ian Leslie, Jon Crowcroft, David A Coomes and Patrick Ferris, to College dinners with Sadiq Jaffer and Srinivasan Keshav, and EEG/CSG discussions with Thomas Ball, Alison Eyres, Orlando Timmerman, Thomas Swinfield, Ryan Gibb, Alastair Beresford, Neil Lawrence and Richard Mortier. Many thanks to them for corrections and feedback, and any remaining errors are my own. Changelog: 12th Feb added note on sportsmanship and Carl's NeurIPS@Cam talk.

1. I promise I'm not a JMK shill, despite being a JMK Fellow.

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2. The keen boardgame player will probably observe that there's always one player who decides to cause trouble just for fun, making everyone lose. This can be dealt with by social means.

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