John Weyant: Integrated Assessment Modelling informing future climate policy
“Whether or not we keep up with the needs of policymakers will be determined by how much they trust the results from models and how relevant they are to their needs.” Professor John Weyant of Stanford University discusses the evolution of Integrated Assessment Models (IAMs), emphasizing the importance of incorporating growing datasets to meet policymakers’ needs. The Integrated Assessment Modeling Consortium (IAMC) gathers leading climate modeling experts, facilitating crucial advancements in scenario development for climate policy. Its contributions, including defining concepts like Net-Zero, are crucial in informing international climate agreements and shaping future strategies for combating climate change.
The sixteenth Annual Meeting of the Integrated Assessment Modeling Consortium (IAMC), organized by the CMCC, took place in Venice in mid November 2023. Bringing together the world’s top experts in integrated assessment of climate models, the IAMC is the network that provides the IPCC with the tools required to create future scenarios and climate predictions which are then crucial towards developing climate policies.
The scenarios produced by research institutes affiliated with IAMC have provided fundamental scenarios and analyses to the IPCC and individual countries to help them define technological, economic, and social strategies compatible with international climate agreements. For example, the concept and strategies of Net-Zero were defined by scenarios produced by models belonging to IAMC, including CMCC models. The IAMC has helped coordinate the work of these modeling groups and communicate their results to decision makers.
Professor John Weyant of Stanford University talks us through the evolution of Integrated Assessment Models (IAM) — complex models that focus on the interaction between the economy, society, and the environment to provide relevant information for public policies — from a national, regional, and global perspective.
As data on economic and social issues continues to increase, Weyant addresses how IAMs can be enhanced to further address the needs of decision makers.
“Now that we have more and more data available [we need to] augment or incorporate those kinds of things into the IAMs. Whether or not we keep up with the needs of policymakers will be determined by how much they trust the results from the models and how relevant they are to their needs.”
In what ways does the IAMC contribute to the current panorama of climate related research?
As mentioned here at the sixteenth Annual Meeting, IAMC’s work is viewed as quite relevant. We had the newly elected chairman of the IPCC, Jim Skea, talking remotely and he said that in the IPCC’s last cycle IAMs had really come into their own and helped shape the debate within the IPCC and climate negotiations more than ever before.
In the last round of the IPCC, a lot of the public and climate debate, and the negotiating sessions saw IAMs being frequently viewed as necessary for obtaining more relevant information about alternative courses of action. A lot of the substance here at this meeting has been on ways that models could be enhanced and improved to look more clearly at things that are now recognized as being important, like equity amongst regions, amongst income groups, among ethnic groups and so forth.
Our work is viewed as very important and part of the message that speakers at the event delivered was a desire for this to continue into the next cycle. Kate Calvin, who is a newly elected Working Group III co-chair and long time participant in IAMC activities, joined Skea in saying that they look forward to working with IAMC to make sure that the tools are used and that they are as useful as possible for decision makers.
What has the evolution of IAMs been?
When I started doing model comparison projects, believe it or not, there was no internet, very poor data processing and graphics capability. I used to draw tables by hand for people to fill in with data. I would usually hire an undergraduate student to key the data into a particular format. Then, I would have to rent out a verse attack plotter for 1,000 USD an hour to actually draw the plots. Now we have people queuing up these model comparisons and running them in the background on their laptops at virtually no marginal cost. So that makes me more optimistic.
All the way back at the beginning of my career we would do model comparisons mostly on U.S. domestic issues: oil, gas, coal, electricity, energy efficiency and what not. And then, in an interesting progression, in the 80s, I was also doing energy modeling for global energy markets.
There were a few global energy markets that had oil, gas and coal and some of those led to the development of the first IAMs because you have global energy, which is a big source of greenhouse gas emissions, and if you put constraints on greenhouse gas emissions and look at how they affect the cost of running the energy system, that turns out to be useful information.
And then, over the years, many of the groups added simple climate models and the carbon cycle, which takes those emissions and turns them into concentrations, which leads to forcing, which leads to temperature change and so on. We performed studies on emission limits, concentration limits, temperature limits and started working on the allocation of responsibilities for reducing emissions, the so-called burden sharing across nations.
Then the model comparison business really went from being, before the turn of the century, mostly USA-based, to being found in major European institutions such as the CMCC, the International Institute for Applied Systems Analysis (IIASA), PBL Netherlands Environmental Assessment Agency, the Potsdam Institute for Climate Impact Research (PIK) and so on.
How has the way we use IAMs changed?
Early this century the work was all about long term sustainability and looking at the discontinuities in the underlying physical systems. However, the aspect that really gets the headlines now is extreme weather events: hurricanes, floods, droughts, wind storms, etc. These events catch the attention of the public who then express their concerns to their government representatives.
I was interviewed about climate impact assessment by a congressional committee that was in charge of budget priorities in the USA. All members of the committee across both political parties were concerned about extreme climate events in their districts. There was extreme flooding and Hurricane Sandy in New York, the deep freeze in Texas, there was wildfire and wildfire smoke in California, etc…
Concern about extreme events kept IAM funding up during the Trump administration because there was broad-based support in Congress and the President’s budget was so far below the level that either the House of Representatives or Senate were comfortable with.
Have IAMs improved in recent years?
There has been a pretty rapid refinement of the models in the last few years. One way is in the requisite disaggregation in space and time to be more directly tied to climate impacts and equity concerns on the ground in particular regions, especially around extreme events as opposed to slowly changing systems.
A lot of the talks here have been on the various ways to augment or incorporate those kinds of factors into the IAMs. Whether or not we keep up with the needs of policymakers will be determined by how much they like the models and how relevant they are. This is part of the challenge.
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