Combining climate measures key to slashing emissions: Study

PARIS – A major new study on the effectiveness of climate measures such as taxes or subsidies in reducing greenhouse gases has found standalone measures fail to make a big difference.

Published in the journal Science on Aug 22, the study examined 25 years of public policies in 41 countries across six continents. In Asia, the countries included India, China, Japan and Indonesia.

It concluded that out of the 1,500 policies analysed in sectors including energy, transport and construction, “only 63 cases of successful climate policies, each leading to average emission reductions of 19 per cent, were identified”.

“The researchers show that bans on coal-fired power plants or combustion engine cars do not result in major emission reductions when implemented alone,” said the Potsdam Institute for Climate Impact Research (PIK) that led the study with Mercator Research Institute on Global Commons and Climate Change (MCC).

“Successful cases only arise in tandem with tax or price incentives in well-designed policy mixes, as shown in the UK for coal-fired power generation or in Norway for cars,” the researchers said.

The study used a new database from the Organisation for Economic Cooperation and Development (OECD) and an innovative approach that combined machine learning methods with established statistical analyses.

It “identified 63 successful policy interventions with total emission reductions between 0.6 billion and 1.8 billion tonnes CO2 (carbon dioxide)”.

By comparison, humanity emitted 57.4 billion tonnes of CO2 equivalent in 2022, according to United Nations estimates.

Among the successes identified was Britain’s introduction in 2013 of a minimum carbon price, subsidies for renewable energy, and a coal phase-out plan.

The researchers hope their work will influence the climate roadmaps countries are updating and must submit to the UN by February 2025.

The aim of these roadmaps is to keep alive the Paris Agreement’s flagship goal of limiting warming to 1.5 deg C from pre-industrial levels.

‘Right mix is crucial’

An interactive website, Climate Policy Explorer, provides an overview of the results, analysis and methods, and is accessible to the public.

“Our findings demonstrate that more policies do not necessarily equate to better outcomes. Instead, the right mix of measures is crucial,” explained the study’s lead author, Dr Nicolas Koch of PIK and MCC.

“For example, subsidies or regulations alone are insufficient; only in combination with price-based instruments, such as carbon and energy taxes, can they deliver substantial emission reductions.”

But Professor Michael Grubb at University College London said by focusing on a small number of statistically significant trend breaks, the researchers missed “the impact of thousands of smaller efforts globally, and the cumulative and often self-reinforcing impact of many smaller measures”.

He also acknowledged it is “the most sophisticated study to date”. “Their conclusion that big impacts require combinations of policies makes absolute sense,” he added.

Dr Robin Lamboll at Imperial College London said. “The study only looks for policies making sudden reductions, whereas most climate policies work on the efficiency of new things or the long-term trajectory of emissions, taking many years to build up greener infrastructure or ways of living.”

Agriculture and land use change, a major emissions sector, was not included in the study. Good data showing reductions in carbon emissions for that sector does not yet exist, Dr Koch said.

In addition, the study covered only the near-term effects, and effects within the country where the policy was adopted, said Jessika Trancik, a professor at the Massachusetts Institute of Technology.

“But in climate change mitigation, we care about the effects on a global scale and bringing emissions down to zero regardless of where emission reductions start,” she said. “So the fact that 63 cases were detected to have a significant impact over the near term where the policies were adopted, it doesn’t mean other policies weren’t effective.”

The good news is that any of the technological tools that are needed to address climate change are now available,” Prof Trancik said, “and ready to be adopted at scale because of a host of different types of policies that came before.” AFP, NYTIMES