Quoted from: https://www.nber.org/reporter/2017number3/integrated-assessment-models-climate-change
The Dynamic Integrated model of Climate and the Economy (DICE) and Regional Integrated model of Climate and the Economy (RICE) models have gone through several revisions since their initial develop-ment around 1990. The latest published versions are the RICE-2010 and DICE-2016R2 models. The latest DICE model is available in GAMS, a fine mathematical software system, and a full description of the earlier version is available.
DICE is a globally aggregated model. RICE is essentially the same, except that output and abatement have structures for 12 regions. This discussion will use the term "DICE model," and for most modules the analysis applies equally to the RICE model.
The DICE model views the economics of climate change from the perspective of neoclassical economic growth theory. In this approach, economies make investments in capital, education, and technologies, thereby reducing consumption today in order to increase consumption in the future. The DICE model extends this approach by including the "natural capital" of the climate system as an additional kind of capital stock. By devoting output to emissions reductions, economies reduce consumption today but prevent economically harmful climate change and thereby increase consumption possibilities in the future.
The DICE model has 12 behavioral equations, two variables to be optimized, and several identities. In the GAMS version, the simplest model has about 240 lines of operational code. A run of 1,000 years takes five seconds, so it can be used for projects with multiple states of the world and Monte Carlo experiments.
The RICE model has the same basic economic and geophysical structure, but contains a regional elaboration. The specification of preferences in RICE is different because it must encompass multiple regions. The general preference function is a Bergson-Samuelson social welfare function over regions. The model is specified using the Negishi approach, in which regions are aggregated using time- and region-specific weights subject to budget constraints.
This sketch of a pair of IAMs in the DICE and RICE models makes it clear that they are highly simplified representations of complex economic and geophysical realities — what might be called geo-macroeconomics. While small and comprehensive models have many advantages, they also have major shortcomings because of their simplifications.
A useful analogy here is to return to the animal kingdom. Each model is like an animal that has its fruitful niche in the analytical ecosystem. Small models can be fleet and can adapt easily to a changing environment or new data, while large models take many years to mature but are able to handle much larger and more complex tasks.