Guess what? A study of about 1,500 climate policies in 35 countries found that the single most effective policy in reducing carbon emissions was a carbon tax.

Exactly the Rudd policy that Tony Abbott axed two decades ago.

The study, by a battery of scientists from around the world, was published in Science in August this year. They undertook a global, systematic ex-post evaluation to identify policy combinations implemented between 1998 and 2022 across 41 countries from six continents. The approach integrated a comprehensive climate policy data base with a machine learning based approach. The data base included the top three greenhouse gas emitters globally – China, the United States and India.

All told they identified 63 policy interventions with total emission reductions of between 0.6 billion and 1.8 billion metric tonnes of CO2. Their conclusion: “our insights on effective but rarely studied policy combinations highlight the important role of price-based instruments in well-designed policy mixes and the policy efforts necessary for closing the emissions gap.”

Annika Stechemesser, a co-author and researcher at the Potsdam Institute for Climate Impact Research in Germany, said the right mix of policies is more important than using as lot of policies. She cited the example of the UK phasing out coal-fired stations working because it was used in tandem with pricing mechanisms.

Many different policies were examined, and OECD data showed a consistent increase in the number of implemented policies across all sectors of the economy between 1998 and 2022. The authors said: “With 270 cases command and control measures such as emission standards and technology mandates are the most frequently used policies in all sectors. Market-based policies are primarily concentrated in developed economises and most prevalent in the transport sector. Among market-based policies subsidies are popular whereas carbon pricing (carbon taxes and emission trading schemes) remain limited.”

While the carbon price mechanism was the best single response to climate change other responses in specific industries were also significant.

The authors say that “successful policy mixes vary across sectors and that policy makers should focus on sector-specific best practices when designing climate policy rather than following a one-size-fits all approach.”

Areas which include profit-maximising firms – namely industry – pricing is a particularly effective policy. Where there is a large share of private consumer incentives in adoption decisions (car choice and heating systems renewal for instance) there needs to a greater focus on how the individuals make decisions.

But the authors also provide some very sobering news. They conclude that, even if all the countries in their sample managed to replicate their past successes in reducing emissions, they would still need to replicate past successes more than four times what has occurred before to close the emissions gap.

Meanwhile, the UN has advised that the world’s annual emissions are projected to be 15 Gt of CO2 equivalents higher by 2030 than would be required to keep global warming to less than 2 degrees above pre-industrial levels.

Xu Chi, an ecologist at Nanjing University, told Nature (22/8) “This study provides a warning to countries around the world that their climate policies have had very limited effects so far. Existing policies will need to be re-evaluated and changes will need to be made.”

Meanwhile Peter Dutton is planning to build nuclear power stations around the country, some of them on earthquake fault lines and vulnerable to rising sea levels by the time they are completed.

He is even touting a nuclear technology – small modular reactors – which does not exist.

Any responsible government with even a small element of courage would take heed of this latest study. Sadly, that’s not what Australia currently has in the Albanese one.