What 95% certainty of warming means to scientists

Sep 24, 2013 by Seth Borenstein
Smoke pours from a chimney at a cement plant in Binzhou city, in eastern China's Shandong province, Thursday, Jan. 17, 2013. Scientists from around the world have gathered in Stockholm in September 2013 for a meeting of a U.N. panel on climate change and will probably issue a report saying it is "extremely likely" - which they define in footnotes as 95 percent certain - that humans are mostly to blame for temperatures that have climbed since 1951. (AP Photo)

Top scientists from a variety of fields say they are about as certain that global warming is a real, man-made threat as they are that cigarettes kill.

They are as sure about climate change as they are about the . They say they are more certain about climate change than they are that vitamins make you healthy or that in Superfund sites is dangerous.

They'll even put a number on how certain they are about climate change. But that number isn't 100 percent. It's 95 percent.

And for some non-scientists, that's just not good enough.

There's a mismatch between what scientists say about how certain they are and what the general public thinks the experts mean, experts say.

That is an issue because this week, scientists from around the world have gathered in Stockholm for a meeting of a U.N. panel on climate change, and they will probably issue a report saying it is "extremely likely"—which they define in footnotes as 95 percent certain—that humans are mostly to blame for temperatures that have climbed since 1951.

One climate scientist involved says the panel may even boost it in some places to "virtually certain" and 99 percent.

Some climate-change deniers have looked at 95 percent and scoffed. After all, most people wouldn't get on a plane that had only a 95 percent certainty of landing safely, risk experts say.

But in science, 95 percent certainty is often considered the gold standard for certainty.

"Uncertainty is inherent in every scientific judgment," said Johns Hopkins University Thomas Burke. "Will the sun come up in the morning?" Scientists know the answer is yes, but they can't really say so with 100 percent certainty because there are so many factors out there that are not quite understood or under control.

George Gray, director of the Center for Risk Science and Public Health at George Washington University, said that demanding absolute proof on things such as climate doesn't make sense.

"There's a group of people who seem to think that when scientists say they are uncertain, we shouldn't do anything," said Gray, who was chief scientist for the U.S. Environmental Protection Agency during the George W. Bush administration. "That's crazy. We're uncertain and we buy insurance."

With the U.N. panel about to weigh in on the effects of greenhouse gas emissions from the burning of oil, coal and gas, The Associated Press asked scientists who specialize in climate, physics, epidemiology, , statistics and risk just what in science is more certain than human-caused climate change, what is about the same, and what is less.

They said gravity is a good example of something more certain than climate change. Climate change "is not as sure as if you drop a stone it will hit the Earth," Princeton University Michael Oppenheimer said. "It's not certain, but it's close."

Arizona State University physicist Lawrence Krauss said the 95 percent quoted for climate change is equivalent to the current certainty among physicists that the universe is 13.8 billion years old.

The president of the prestigious National Academy of Sciences, Ralph Cicerone, and more than a dozen other scientists contacted by the AP said the 95 percent certainty regarding climate change is most similar to the confidence scientists have in the decades' worth of evidence that are deadly.

"What is understood does not violate any mechanism that we understand about cancer," while "statistics confirm what we know about cancer," said Cicerone, an atmospheric scientist. Add to that a "very high consensus" among scientists about the harm of tobacco, and it sounds similar to the case for , he said.

But even the best study can be nitpicked because nothing is perfect, and that's the strategy of both tobacco defenders and climate deniers, said Stanton Glantz, a medicine professor at the University of California, San Francisco and director of its tobacco control research center.

George Washington's Gray said the 95 percent number the Intergovernmental Panel on Climate Change will probably adopt may not be realistic. In general, regardless of the field of research, experts tend to overestimate their confidence in their certainty, he said. Other experts said the 95 percent figure is too low.

Jeff Severinghaus, a geoscientist at the Scripps Institution of Oceanography, said that through the use of radioactive isotopes, scientists are more than 99 percent sure that much of the carbon in the air has human fingerprints on it. And because of basic physics, scientists are 99 percent certain that carbon traps heat in what is called the greenhouse effect.

But the role of nature and all sorts of other factors bring the number down to 95 percent when you want to say that the majority of the warming is human-caused, he said.

Explore further: UN climate report will not sway US deniers

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tadchem
1.9 / 5 (27) Sep 24, 2013
What a scientist's '95% certainty' means is that he is erroneously trying to fortify an opinion with faux statistical-sounding arguments. What a statistician's '95% certainty' means is that a measurement, replicated a statistically significant number of times, will likely fall within the specified limits 95% of the time.
Sampling error, site selection bias, non-representative measurements, and other problems too numerous to list that arise with efforts to determine the hypothetical 'global average temperature' make the concept empirically and pragmatically meaningless.
Caliban
4.1 / 5 (17) Sep 24, 2013
What a scientist's '95% certainty' means is that he is erroneously trying to fortify an opinion with faux statistical-sounding arguments. What a statistician's '95% certainty' means is that a measurement, replicated a statistically significant number of times, will likely fall within the specified limits 95% of the time.
Sampling error, site selection bias, non-representative measurements, and other problems too numerous to list that arise with efforts to determine the hypothetical 'global average temperature' make the concept empirically and pragmatically meaningless.


No, tc, 95% certainty in scientific terms means exactly what the article articulates it to mean.

It is a standard that is not subject to re-interpretation by you or anyone else in the Denialverse.

Wolf358
4.8 / 5 (17) Sep 24, 2013
People who want 100% certainty are looking for religion, not science. I'm 95% certain of it, anyway.
antialias_physorg
5 / 5 (10) Sep 25, 2013
They'll even put a number on how certain they are about climate change. But that number isn't 100 percent. It's 95 percent.

95% is the accepted norm for 'statistically significant' (i.e. the level at which it makes sense to publish a scientific paper).

100% is not to be had. Ever. If someone wants 100% certainty they either don't understand the concept of statistics, the concept of science, or the concept of certainty. Such a person should reject the notion that "the sun will rise again tomorrow"
(If such a person were to apply that kind of onus of proof on everything the'd not be able to live their life in any respect. Since they could rely on nothing - not even their next breath)
You can get 100% certainty only in tautological statements or made-up statements not connected to reality (e.g. religion). Neither of which carries any useful information.
antialias_physorg
4.6 / 5 (10) Sep 25, 2013
In general, regardless of the field of research, experts tend to overestimate their confidence in their certainty

Good thing then that this 95% percent value is not an estimate but based on numbers (in ALL scientific research. You NEVER just estimate how good your results are but have to show it with the data using the appropriate statistical methods)
antigoracle
1.5 / 5 (23) Sep 25, 2013
I'm 100% certain their greedy "solution" will make their False Prophet Gore, wealthy.
Neinsense99
2.4 / 5 (17) Sep 29, 2013
I'm 100% certain their greedy "solution" will make their False Prophet Gore, wealthy.

antigoracle and scientific debate
"-- runrigTurd
Now sink back into the darkness, from whence you rose, like a true Turd"
"-- magganusTurd"
"Do you Turds know how to read far less comprehend?"
"And so, the Turd quickly sinks back into the darkness.."
"OK, that one just made you my favorite Turd."
"I believe if I close my eyes and try really...really... hard I may be able to squeeze a small Turd out that falls for that."
"At last, the penny has dropped and stuck in the Turd."
"Turd Stool"
"OMG I can just imagine how fast the GW Alarmist Turds would appear..."
"That's the level I must descend to, so that I may communicate with the GW Alarmist Turds."
"Green, you gotta love green, well.... unless you're a Turd."
"That would just make us deceitful Turds, like you."

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VendicarE
3.8 / 5 (11) Sep 29, 2013
Once again the Scientifically literate like Wolf, and Antialias have it right, and surprise, the anti-science retards like the Anti-Gore-Tard, prove themselves to be mentally ill.

When 95 percent of doctors give me the same medical opinion, I would be fool not to take it.

When 95 percent of science doctorates give denialists the same scientific opinion, they are fools who do not accept it.

ubavontuba
1.6 / 5 (20) Sep 29, 2013
Consensus definition of global warming:

"global warming
n.
An increase in the average temperature of the earth's atmosphere, especially a sustained increase sufficient to cause climatic change."

Global temperatures: http://www.woodfo....6/trend

I'm 95% certain the globe hasn't warmed in more than a decade...

aroc91
4.7 / 5 (13) Sep 29, 2013
Consensus definition of global warming:

"global warming
n.
An increase in the average temperature of the earth's atmosphere, especially a sustained increase sufficient to cause climatic change."

Global temperatures: http://www.woodfo....6/trend

I'm 95% certain the globe hasn't warmed in more than a decade...



If it were 1950 and you plotted '40-'50, you'd be claiming we were going into an ice age. You can't draw a conclusion about climate from 10 years of data.
VendicarE
4 / 5 (10) Sep 29, 2013
And UbVonTard shifts back to using HadCrut3, which he has been repeatedly told excludes large areas of the polar regions and is hence biased toward reporting less change than is actually happening.

UbVonTard has one primary interest... Lying
Lying is what he does.
Lying is what he lives for.
Lying is is stock and trade.

ubavontuba
1.3 / 5 (16) Sep 30, 2013
Consensus definition of global warming:

"global warming
n.
An increase in the average temperature of the earth's atmosphere, especially a sustained increase sufficient to cause climatic change."

Global temperatures: http://www.woodfo....6/trend

I'm 95% certain the globe hasn't warmed in more than a decade...
If it were 1950 and you plotted '40-'50, you'd be claiming we were going into an ice age. You can't draw a conclusion about climate from 10 years of data.
You're confusing "drawing conclusions" with "making predictions."

In regards to recorded history, t's absolutely true to state: Currently, the globe hasn't warmed in more than a decade. And it's absolutely true to state: 1940 to 1950 was a brief period of rapid cooling.

I have not claimed either are predictive.

VendicarE
3.8 / 5 (8) Sep 30, 2013
"You're confusing "drawing conclusions" with "making predictions." - UbVonTard

You aren't capable of doing either with 10 years of temperature data.

No Global trends have any statistical relevance over such a short period of time.

You have been repeatedly told that, and you persist in making the same false claims.

UbVonTard has one primary interest... Lying
Lying is what he does.
Lying is what he lives for.
Lying is is stock and trade.

ubavontuba
1.3 / 5 (15) Sep 30, 2013
"You're confusing "drawing conclusions" with "making predictions." - Uba

You aren't capable of doing either with 10 years of temperature data.

No Global trends have any statistical relevance over such a short period of time.

You have been repeatedly told that, and you persist in making the same false claims.
LOL. Apparently, Vendi-chatterbot believes historical documentation is meaningless. Maybe it thinks roads that have been built in the last ten years shouldn't be included on maps! LOL!