Scientific support for link between human activity and climate change strengthens

Monash University
Monash University

There is almost universal agreement for the link between human activity and climate change among top climate scientists, an international team of researchers has found.

A paper published today in the journal Environmental Research Letters, by researchers from Monash University and US colleges Louisiana State University and George Mason University, revealed how scientific consensus on anthropogenic (human-caused) global warming has evolved over the last decade.

Consensus revisited: quantifying scientific agreement on climate change and climate expertise among Earth scientists 10 years later is based on the results of a survey of 2,780 Earth scientists in 2019 and follows a similar study conducted in 2009.

The research comes as the world focuses on the impact of climate change at the COP26 conference in Glasgow from 31 October.

Of the survey respondents who answered the primary question about the cause of global warming, 91.1 per cent agreed the Earth is getting warmer mostly because of human activity, which is 11 percentage points higher than the 80 per cent found by the 2009 study.

Across all definitions of climate expertise, the highest consensus that the Earth’s temperature is getting warmer mostly because of human activity was among biogeochemistry / ecology scientists.

Monash University researcher Dr John Cook, who was part of the study, said: “Although there have been many studies finding a consensus amongst climate scientists, there’s little research into exactly how agreement has evolved over time and how different definitions of climate expertise shape that view.

“This is the first time the methodology of the 2009 study has been replicated to measure how climate consensus has strengthened over the last decade.”

The authors of the 2019 study found 100 per cent of actively publishing climate experts – who had published 20 or more climate papers each between 2015 and 2019 – accept that global warming is human-caused.

The figure in this group in 2009 was 97.4 per cent.

Researchers also found in the 2019 study that 98.7 per cent of respondents who had at least 50 per cent of their scientific publications in the area of climate change agreed with anthropogenic global warming.

Scientists who reported working between 11-15 years in the area of climate change had the highest acceptance at 98.3 per cent.

Conversely the group with the lowest acceptance (90.7 per cent) reported working 0-5 years in the area of climate change.

“The findings show that consensus has increased across the board, and that consensus increases with the level of expertise – the more you know about climate science, the more likely you are to understand that humans are responsible for climate change,” Dr Cook said.

When analysing the responses by subdiscipline, the authors found those who self-identified as economic geologists had the lowest level of consensus – with 84.1 per cent agreeing with anthropogenic global warming.

This was a group that were the biggest doubters in the 2009 study, but at a much lower 47 per cent agreement.

Researchers found a large increase in the level of agreement on anthropogenic global warming among those self-identifying as meteorologists – from 64 per cent in the 2009 study to 91 per cent in the 2019 study.

Dr Cook also led a study in 2013 which found 97 per cent of climate scientists agree with the theory of human-caused climate change.

It was cited broadly by the likes of then-US President Barack Obama and former UK Prime Minister David Cameron, as well as late night talk show hosts and other politicians.

Dr Cook acknowledged there was a gap between expert consensus of anthropogenic global warming and public understanding.

“It is imperative to strengthen efforts to engage and educate people about the scientific consensus on climate change,” Dr Cook said.

“Such efforts are essential to helping our society make more informed decisions about how to stabilise our climate.”

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