97% of Climate Scientists Really Do Agree
“97 percent of climate scientists agree: Humans are causing global warming.”
It’s one of the most famous statistics in all of science: That experts, the people who
know the most about Earth’s climate, agree–almost universally–that humans are warming the
Where does this 97% number come from?
The most famous source of the 97% agreement comes from a study in 2013 by Australian scientist
He looked at almost 4,000 scientific papers that made some statement about whether humans
were the main cause of climate change.
And 97% of those papers agreed with the consensus.
To make sure nothing was misinterpreted, he also asked scientists to rate the views of
their own papers, and they found the same 97% agreement.
It shouldn’t surprise you to learn that people have attacked this study, saying its
methods were wrong, and that it miscounted things.
But even if we ignore Cook’s study, turns out lots of other people have looked at this
question and found a similar answer.
Between 90-100% of experts agree the climate is changing, Earth is getting
warmer, and we’re responsible for a lot of it.
What does it mean to measure consensus?
First, you identify the experts.
In this case, the experts are thousands of scientists who study climate and publish their
work in peer-reviewed journals.
Peer review means that every finding that’s published is analyzed by people working in
the same field, people who really know what they’re talking about.
Mistakes occasionally happen, but this system is built to correct those mistakes, and it’s
by far the best process humans have ever come up with for doing good science.
Once we find this group of experts, we analyze their opinion: for or against a particular
idea.
Sometimes this is done by studying what scientists have written in their papers.
Other times scientists are surveyed directly.
This can even be done by listening to what scientists say in public.
Now some scientists don’t explicitly express an opinion either way.
They’re not included in the analysis.
Consensus is the fraction who support an idea divided by the sum of those who support plus
All these different methods have ended up with the same conclusion: The people who know
the most almost universally agree about what’s causing global warming.
But if you ask everyday people what they think the consensus is, they guess that only 55%
That’s way off from what experts actually think.
Because–surprise!–there are people out there who spend a lot of money and effort
A big argument among critics of the 97% agreement is that in a lot of research papers, scientists
never specifically write “humans are causing most global warming”.
These papers are usually excluded from studies about consensus, because they don’t give
People draw different conclusions from this.
Some say not giving a position is exactly what you’d expect from scientists who agree
that something’s basically settled, like how physicists don’t write “gravity is
real” in every single paper, biologists aren’t regularly citing Darwin and natural
But critics of global warming science claim that any scientist who doesn’t specifically
say in every paper that they agree with the consensus, should be counted as uncertain,
or even counted as rejecting it.
And this is a very strange claim to make, that any climate scientist who doesn’t write
“I believe that humans are the main cause of global warming” is actually uncertain
or doesn’t believe that humans are the main cause of global warming.
To show you why this is flawed, let’s apply the same logic to another scientific idea.
Plate tectonics is the theory that Earth’s crust is made up of several large chunks that
move over time, and that new crust is made at some places and eaten up at others.
Not a controversial idea today, but you might be surprised to learn that before the 1950s
and 60s, most scientists didn’t accept it.
Researchers looked at recent geology papers using the same criteria the critics of global
warming science claim should be used on climate consensus: That any paper that doesn’t explicitly
state that “plate tectonics is real” should be counted as uncertain, or as rejecting it.
Turns out, not one single paper, out of hundreds, specifically endorsed the theory of plate
So clearly, plate tectonics is a hoax?
Doubt about what’s causing climate change really only exists among people who… how
do i put this… aren’t experts.
And that’s a big problem, because when we think scientists are divided on an issue,
we’re less likely to think the issue is a problem.
This also means if more people understood how much agreement there really is about humans
causing climate change, we could start paying attention to more important questions like
People sometimes say that science doesn’t work by consensus, or by agreement, and that
every truth must be decided by experiment.
Consensus, or agreement, is a hugely important part of science.
When scientists do experiments, they don’t repeat or re-establish every single bit of
knowledge that got them to that point.
They, and I hope we, trust in the process of science.
In every field, there are things that are well-enough proven, that are agreed upon,
and these are where scientists start from to journey out into what’s actually unknown.
And when it comes to the science of global warming and climate change, experts agree
maybe it’s time we accept the consensus, I think it’s time we start talking about
That’s why I’m excited today to announce a new project here on YouTube, one I’ve
been working on for most of the last year.
It’s a new channel dedicated to stories about climate change and climate science,
It’s brought to you by the same amazing people that make these awesome videos here
on It’s Okay To Be Smart, along with a few new faces
Hot Mess is going to be the best channel on YouTube for stories about our planet’s changing
I know that’s something that a lot of you care about.