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Why climate action is a good bet, even if it's not a sure thing

DAILY SCIENCE

When they ran the math, researchers landed on some surprising bets for climate action

Opting for an early transition to a decarbonized society pays off—even if the probability of achieving climate targets like 1.5°C is very low.
February 14, 2023

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Immediately starting a transition to a green economy is a rational approach even if the chances of achieving that transition are small, according to a new study. The findings lend a startling clarity to climate decision-making even as the world hurtles toward the 1.5° C warming benchmark: doing the right thing is still the right thing.

The conclusion flows from a mathematical model of which decisions matter most and how to apportion responsibility for them in uncertain conditions.

Climate change is precisely such a condition of uncertainty because we don’t know exactly how close the world is to climate tipping points. Meanwhile, climate policy is diffuse and unpredictable. If one country instigates a green policy shift it might not end up being fully carried out, and other countries might not follow suit anyway.

Yet all of us who fail to make an effort to stave off the effects of climate change will be morally responsible if those effects occur. So when is it rational to undertake the effort?

“In the context of climate emission policies, taking best decisions can still pay off even when the probability that such decisions are actually implemented becomes very low: for example, because of the inertia of legislation or because of the difficulty of reaching global agreements,” says study team member Nicola Botta, senior scientist at the Potsdam Institute for Climate Impact Research in Germany.

The finding “boils down to the observation that a ‘moral’ approach towards climate decision making is often rational,” Botta adds.

Botta and his colleagues used a previously developed theory of decision-making that enables researchers to determine the best policy choice when decisions are made in a step-by-step way under conditions of uncertainty.

 

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In a paper published in the journal Environmental Modeling & Assessment, the researchers devise a mathematical model based on this theory to evaluate greenhouse gas emission policies. They assume that policymakers want to avoid severe impacts from climate change on the one hand, and avoid harming the economy on the other, and evaluate two policy options with this goal in mind: immediately start a transition to a green economy, or delay the transition until the next decision step.

The researchers used the model to compute the best and worst policy decision at each decision step, and found that immediately launching a green transition is a rational approach across a wide range of uncertainties, even if the likelihood that it will be achieved is small.

The model is so simple as to be stylized: it involves states in which a green transition is either started or delayed; economic wealth is either high or low; and the world is either committed or uncommitted to severe impacts of climate change.

But it’s this very simplicity that enables the model to grapple with uncertainty, Botta explains. In that sense, it’s different from the Integrated Assessment Models (IAMs) that are frequently used in climate change planning for example in reports from the Intergovernmental Panel on Climate Change (IPCC). IAMs tend to be extremely complex—but typically ignore uncertainty.

The new approach could complement IAMs in climate policy planning in two ways, Botta thinks. First, it could be used at the beginning of climate policy discussions to help stakeholders understand the nature of the policy problem, which decisions matter most, and how uncertainties affect which decisions are best.

“This understanding could be enough, for example, to overcome deadlocks in climate negotiations but also useful to inform the application of modeling approaches like IAMs and expert elicitation work,” Botta says.

Then, at the end of the policy advice process, after all the modeling has been done and the experts consulted and the various probabilities have been worked out, the approach could then identify the optimal policy choice, he adds.

Source: Botta N. et al.Responsibility under uncertainty: Which climate decisions matter most?” Environmental Modeling & Assessment 2023

Image: © Anthropocene Magazine

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