Climate Science - What Is Scientific Consensus?
So far in our climate science series, we have introduced the basics of climate science, shown how humans are already impacting the climate, explained tipping points and feedback loops, given a brief history of how we got to this point, and looked to the future of our climate. In Part 6 we investigate the topic of Scientific Consensus.
One of the most common rebuttals of the idea that humans are causing our climate to change is that the “science is not settled”. This phrase implies that the scientific community are still grappling with the issue of whether humans are causing climate change, and can be heard on TV, read in newspapers, and has even been repeated by US presidents. The implication is that there is a lack of “scientific consensus” as to whether humans are causing climate change.
In this blog, without looking into any of the ulterior motives behind why some people would deny climate change exists, we will explain what scientific consensus means, and examine whether it applies to the theory of anthropogenic climate change.
Some of the confusion arises from certain terms, such as consensus and theory, having very different meanings in a scientific setting to their everyday colloquial use.
Scientific consensus is achieved when the great majority of scientists of a given field agree upon a position based on a large amount of evidence. Consensus is not just a general agreement or a “poll of scientists”, but is dependent on the expertise of the scientists in question and is based on the accumulation and verification of evidence.
A scientific theory has been defined as “an explanation of some aspect of the natural world that has been substantiated through repeated experiments or testing”. The colloquial definition of theory is “an idea”, but as this definition shows, a scientific theory is more like a fully validated model for how a certain aspect of the world works.
There are other examples of scientific theories that have gained the consensus of scientists, including evolution, gravity, the big bang, the effectiveness of vaccines, the link between smoking and cancer, the list goes on. It is also important to note that reaching a consensus does not mean the work in that field is complete, far from it, but it does mean that the vast majority of scientists agree on the basic principles of the theory.
So, do the vast majority of climate scientists agree that humans are causing the world’s climate to change?
This question has been extensively investigated:
In 2013 another peer-reviewed study looked at over 11,000 scientific papers relating to climate change, and found that “Among abstracts expressing a position on (anthropogenic global warming), 97.1% endorsed the consensus position that humans are causing global warming”.
A 2015 review of six independent studies found that “the consensus that humans are causing recent global warming is shared by 90%–100% of publishing climate scientists”.
And in 2020 a peer-reviewed study on “Expert credibility in climate change” looked at 1,372 climate researchers that actively published in their field, and found that 97-98% of them supported the tenets of anthropogenic climate change as set out by the IPCC.
This implies that whenever TV studios want to have a balanced “debate” over climate change, they should really invite 97 climate scientists on vs 1 or 2 sceptics, as demonstrated on Last Week Tonight with John Oliver.
The consensus among climate scientists is clear, but it is worth remembering this is not limited to scientists from any one country, there is global recognition of the effect of humans on the climate. 195 countries are members of the IPCC, 174 states in addition to the European Union signed the Paris Agreement, and 80 National Academies of Science across the world (shown in red below) have either implicitly or explicitly endorsed the consensus of anthropogenic climate change. There aren’t many other topics that cause such unanimous agreement between countries otherwise in conflict or competition with each other.
In conclusion, while scientists are still predicting the future of our climate, investigating our past climates, examining the danger of tipping points and determining how fast we need to reduce emissions, they are no longer debating whether or not humans are causing climate change, on that topic the scientific consensus is overwhelming.