DICE

The Dynamic Integrated model of Climate and the Economy (DICE) is an integrated assessment model.^2,3 In one model it runs from economic activity to emissions, through the carbon cycle and climate, to damages and back to policy.^2,3 William Nordhaus of Yale built it; the original was published at Yale in 1992.^2,4 It has been revised several times, and the latest version, DICE-2023, is described by Lint Barrage and William Nordhaus in the Proceedings of the National Academy of Sciences, March 2024.^1,3 A regional version, RICE, divides the world into regions; its current version was developed by Zili Yang.^1,3

The core is a model of economic growth (the Ramsey model) in which society can give up some consumption today to cut emissions and so be better off later through damages avoided.³ It is built mainly to find the best policy: it chooses the path of emissions cuts that maximises economic well-being over time, though it can also score a given policy.³ Damages grow with the square of the rise in global temperature since pre-industrial times.³ The 2023 review of studies puts them at 1.6% of world output at 3 °C of warming, though those studies leave out many impacts, such as biodiversity loss, ocean acidification and extreme events.³ For its carbon cycle the 2023 version uses DFAIR, adapted from the FAIR impulse-response model.³ Emission cuts can deepen by at most 12 percentage points in each five-year period, and every scenario assumes all countries take part with one harmonised carbon price, an assumption the paper calls highly optimistic.³

Its best-known output is the social cost of carbon: the damage, in today's money, done by one more tonne of carbon dioxide.³ DICE-2023 puts it at $66 per tonne for 2020.³ The US and other governments have used DICE to calculate this figure.^2,3 The same paper projects 3.6 °C of warming by 2100 under current policies, measured from 1765.³

The model is published in a public Yale folder linked from the paper.^1,3 It holds the GAMS code (DICE2023-b-4-3-10) and an Excel version kept in step with it.¹ Beside them are background notes on discounting, damages, non-CO2 gases and DFAIR, and a draft third edition of the user's manual dated May 2024.¹ GAMS is a commercial modelling language; the folder's notes say a licence costs around $1000, and free trials are limited in model size.¹ The code is marked as copyright, with no open licence.¹

DICE has no places in it, only one world economy with a single commodity.³ What it offers someone working on a place is the reasoning behind a carbon price or a social cost of carbon used to value a local project's emissions, and how much that figure moves with the discount rate and the damage estimate.³ For models that represent energy technologies and regions in detail, see GCAM, MESSAGEix and REMIND.