MimiDICE2016R2

This repository is a work-in-progress implementation of the DICE 2016R2 model, originally created in GAMS and described here and in the following paper:

Nordhaus, William. 2018. "Projections and Uncertainties about Climate Change in an Era of Minimal Climate Policies." American Economic Journal: Economic Policy, 10 (3): 333-60.

As of now this is a WIP, as we are still working on getting testing of our outputs to properly match the outputs of the GAMS model runs. Anyone interested in helping with this effort is encouraged to reach out!

As described in Nordhaus, William. 2018. "Projections and Uncertainties about Climate Change in an Era of Minimal Climate Policies." American Economic Journal: Economic Policy, 10 (3): 333-60 the only difference between the difference between this repository and MimiDICE2016 is the damage function parameter setting of the a2 damage quadratic term parameter to 0.0027 as opposed to 0.00236 as set in DICE2016R.

Software Requirements

You need to install Julia 1.1.0 or newer to run this model. You can download Julia from http://julialang.org/downloads/.

Preparing the Software Environment

To install MimiDICE2016R2.jl, you need to run the following command at the julia package REPL:

pkg> add https://github.com/anthofflab/MimiDICE2016R2.jl

You probably also want to install the Mimi package into your julia environment, so that you can use some of the tools in there:

pkg> add Mimi

Running the model

The model uses the Mimi framework and it is highly recommended to read the Mimi documentation first to understand the code structure. For starter code on running the model just once, see the code in the file examples/main.jl.

The basic way to access a copy of the default MimiDICE2016R2 model is the following:

using MimiDICE2016R2

m = MimiDICE2016R2.get_model()
run(m)

Calculating the Social Cost of Carbon

Here is an example of computing the social cost of carbon with MimiDICE2016R2. Note that the units of the returned value are 2010US$/tCO2.

using Mimi
using MimiDICE2016R2

# Get the social cost of carbon in year 2020 from the default MimiDICE2016R2 model:
scc = MimiDICE2016R2.compute_scc(year = 2020)

# You can also compute the SCC from a modified version of a MimiDICE2016R2 model:
m = MimiDICE2016R2.get_model()    # Get the default version of the MimiDICE2016R2 model
update_param!(m, :t2xco2, 5)    # Try a higher climate sensitivity value
scc = MimiDICE2016R2.compute_scc(m, year = 2020)    # compute the scc from the modified model by passing it as the first argument to compute_scc

The first argument to the compute_scc function is a MimiDICE2016R2 model, and it is an optional argument. If no model is provided, the default MimiDICE2016R2 model will be used. There are also other keyword arguments available to compute_scc. Note that the user must specify a year for the SCC calculation, but the rest of the keyword arguments have default values.

compute_scc(m = get_model(),  # if no model provided, will use the default MimiDICE2016R2 model
    year = nothing,  # user must specify an emission year for the SCC calculation
    last_year = 2510,  # the last year to run and use for the SCC calculation. Default is the last year of the time dimension, 2510.
    prtp = 0.03,  # pure rate of time preference parameter used for constant discounting
)

There is an additional function for computing the SCC that also returns the MarginalModel that was used to compute it. It returns these two values as a NamedTuple of the form (scc=scc, mm=mm). The same keyword arguments from the compute_scc function are available for the compute_scc_mm function. Example:

using Mimi
using MimiDICE2016R2

result = MimiDICE2016R2.compute_scc_mm(year=2030, last_year=2300, prtp=0.025)

result.scc  # returns the computed SCC value

result.mm   # returns the Mimi MarginalModel

marginal_temp = result.mm[:climatedynamics, :TATM]  # marginal results from the marginal model can be accessed like this

Pulse Size Details

By default, MimiDICE2016R2 will calculate the SCC using a marginal emissions pulse of 5 GtCO2 spread over five years, or 1 GtCO2 per year for five years. The SCC will always be returned in $ per ton CO2 since is normalized by this pulse size. This choice of pulse size and duration is a decision made based on experiments with stability of results and moving from continuous to discretized equations, and can be found described further in the literature around DICE.

For a deeper dive into the machinery of this function, see the forum conversation here, which is focused on MimiFUND but has similar internal machinery to MimiDICE2016R2, and the docstrings in marginaldamage.jl.