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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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At a glance - The 97% consensus on global warming

Posted on 16 May 2023 by John Mason, BaerbelW

On February 14, 2023 we announced our Rebuttal Update Project. This included an ask for feedback about the added "At a glance" section in the updated basic rebuttal versions. This weekly blog post series highlights this new section of one of the updated basic rebuttal versions and serves as a "bump" for our ask. This week features "The 97% consensus on global warming". More will follow in the upcoming weeks. Please follow the Further Reading link at the bottom to read the full rebuttal and to join the discussion in the comment thread there.

At a glance

What is consensus? In science, it's when the vast majority of specialists agree about a basic, well-established principle. Thus, astronomers agree that the Earth orbits around the Sun. Biologists accept that tadpoles hatch out from frog-spawn and grow into adult frogs. Almost all geologists agree that plate tectonics is real and you'd be hard-placed to find a doctor who thinks smoking is harmless.

In each above case, a phenomenon has been so thoroughly investigated that those who specialise in its study have stopped arguing about its explanation. Nevertheless, these examples are all things that were once argued about, often passionately. That's how progress works.

The establishment of scientific consensus is therefore the end-point of an often lengthy time-line starting with something being observed and ending with it being explained. Let's look at a classic and highly relevant example.

In the late 1700s, the Earth-Sun distance was calculated. The value, 149 million kilometres and incredibly close to modern measurements, got French physicist Joseph Fourier thinking. He innocently asked, in the 1820s, something along these lines:

Why is Planet Earth such a warm place? It should be an ice-ball at this distance from the Sun.

Such fundamental questions about our home planet are as attractive to inquisitive scientists as ripened fruit is to wasps. Fourier's initial query set in motion a process of research that within a few decades had experimentally confirmed that carbon dioxide has heat-trapping properties. Through the twentieth century, the research intensified, particularly during the Cold War when there was major interest in the behaviour of infra-red (IR) radiation in the atmosphere. Why? Because heat-seeking missiles, invented at the time, home in on jet exhausts which are IR hotspots, so they needed to thoroughly understand what makes IR tick.

That research led to the publication, some 130 years after Fourier's initial interest, of the landmark 1955 paper by Gilbert Plass, “The Carbon Dioxide Theory of Climatic Change”, explaining in detail how CO2 traps heat in our atmosphere. Note in passing that Plass used the term "Climatic Change" all the way back then, contrary to the deniers' frequent claim that it is used nowadays because of a recent and motivated change in terminology.

From observation to explanation, this is a classic illustration of the scientific method at work, Fourier gets people thinking, experiments are designed and performed and in time a hypothesis emerges. The Oxford English Dictionary states: “a hypothesis is a supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation.”

Once a hypothesis is proposed, it becomes subject to rigorous testing within the relevant specialist scientific community. Testing ensures that incorrect hypotheses fall by the wayside, because they don't stand up to scrutiny. But some hypotheses survive such interrogation. As their supporting evidence mounts up over time, they eventually graduate to become theories.

Theories are valid explanations for things that are supported by an expert consensus of specialists. Gravity, jet aviation, electronics, you name it, all are based on solid theories that are known to work because they have stood the test of time and prolonged scientific inquiry.

In climate science today, there is overwhelming (greater than 97%) expert consensus that CO2 traps heat and adding it to the atmosphere warms the planet. Whatever claims are made to the contrary, that principle has been established for almost seventy years, since the publication of that 1955 landmark paper.

Expert consensus is a powerful thing. None of us have the time or ability to learn about everything, so we frequently defer to the conclusions of experts. It’s precisely why we visit doctors when we’re ill. Yet the public underestimates the degree of expert consensus that our vast greenhouse gas emissions trap heat and warm the planet. That is because alongside information, we have misinformation and certain sections of the mass-media are as happy to trot out the latter as the former. We saw a very similar phenomenon during the COVID-19 pandemic and it cost many lives.

For those who want to learn more, a much longer and detailed account of the history of climate science is available on this website.

Please use this form to provide feedback about this new "at a glance" section. Read a more technical version via the link below!

Click for Further details

In case you'd like to explore more of our recently updated rebuttals, here are the links to all of them:

Myths with link to rebuttal Short URLs
Ice age predicted in the 1970s
It hasn't warmed since 1998
Antarctica is gaining ice
CRU emails suggest conspiracy
What evidence is there for the hockey stick
CO2 lags temperature
Climate's changed before
It's the sun
Temperature records are unreliable
The greenhouse effect and the 2nd law of thermodynamics
We're heading into an ice age
Positives and negatives of global warming
The 97% consensus on global warming


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Comments 1 to 2:

  1. Incredibly well written, informative, accurate explanation. A delight to read.  Although I still have some trouble reconciling "at a glance" with quite a long explanation.

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  2. @ NigelJ - thanks. At a glance are always ideally <500 words that can be read e.g. when you have phoned that utility company and are waiting for an actual human to answer while the tinny music plays on - in fact my experience of the utilities of late is that I could get through a dozen of them. The longer ones (this one's around 700 words) occur either when something has been so slagged off by the opposition that it deserves fuller explanation at all levels - OR when said opposition has picked an obscure and complex topic with which to make word-salad, so lots of first principles have to be explained. In summary - there's no one typical climate myth. Each has to be treated on its anti-merits!

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