In a rational world, it would have been an entirely unnecessary research project. But sadly not in Australia and the USA, hotbeds of climate change denialism.

US and Australian scientists have found an extraordinary degree of scientific concensus on the reality of climate change: 97% of climate scientists agree that climate change is happening – and that it is caused by humans.

Since the governments of 195 nations have de facto already accepted this, and collectively vowed at the UN climate conference in Paris last December to reduce greenhouse gas emissions from fossil fuel combustion and contain global warming if possible to a rise of 1.5C, it might be expected that citizens would need no further convincing. But surveys shows that they do – and particularly in the US.

So John Cook, climate communication fellow at the University of Queensland’s Global Change Institute in Australia, and colleagues from the US, Canada and Europe report in Environmental Research Letters that they have examined all the research yet again.

And they have come up yet again with a conclusion that supports all previous research: that 96%-98% of climate scientists agree that climate change is caused by humans.

Consensus on consensus

Cook says he hopes this latest finding, which he terms “consensus on consensus”, will enable scientists to focus on the real work – addressing climate change. “Global warming is the most serious issue of our age, and now scientists, engineers, and business and political leaders can focus their efforts on addressing it”, he says.

Sarah Green, a chemistry professor at Michigan Technological University and one of the report’s co-authors, adds: “What’s important is that this is not just one study – it’s the consensus of multiple studies.”

Another co-author, Professor Naomi Oreskes, professor of the history of science at Harvard University, says: “Non-expert opinion and making unsupported assumptions can hugely impact the findings. However, with multiple studies finding consistent high levels of scientific agreement, we are confident the debate can now be put to bed.”

The researchers base their conclusion on seven independent consensus studies already conducted by the co-authors. And it includes one in 2013, in which scientists surveyed more than 11,944 abstracts of scientific papers, and concluded – not for the first time – that most scientists agree that humans are changing the climate in which they so successfully evolved.

There has always been healthy and necessary scepticism about any research conclusion, and scientists themselves expect their conclusions to be replicated or proved in error, and their favourite hypotheses to be challenged, repeatedly.

But there has also been an apparently organised programme, for more than a decade, of outright denial and counter-claim. Additionally, climate scientists have been the subject of condemnation and abuse not normally heaped upon academic researchers.

None of these factors has much altered the overall conclusion, in a programme of sustained international research launched in 1988: climate is changing, and human economic activity is making it happen.

Levels of climate expertise

In the latest study, the researchers once again concluded that the greater the levels of expertise in climate science among those quizzed, the greater the likelihood of agreement that humans cause climate change.

Sources of possible confusion might include surveys of people who had already made up their minds that it isn’t happening or that it isn’t the fault of humans. It was possible, too, that those quizzed were not themselves experts in climate science: some might be economic geologists, with expertise in coal or oil deposits.

But the outcome, after more than a quarter of a century of scientific consensus on climate change, remains the same: only 12% of people in the US and 15% in Australia are aware that there is strong agreement among climate scientists.

“The public has a very skewed idea of how much disagreement there is in the scientific community”, Professor Green says.

And as the paper concludes: “Agreement, or perceived agreement, about the extent and causes of climate change has no bearing on rational choices about greenhouse gas emission reduction – those are driven by the trade-offs between the impacts of climate change and the impacts of climate policy.

“But it does affect the public perception of and the political debate on climate policy, as does the integrity of climate research.”

Tim Radford writes for Climate News Network, where this article originally appeared.