ENVIRONMENT

What Are The Chances That Climate Change Is"Natural"?April 14, 2014 | by Justine Alford

photo credit: Wikimedia Commons.

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A new study which statistically analyzed temperature data over the pre-industrial period and

the industrial period has rejected the hypothesis that global warming is due to natural

variability at confidence levels greater than 99%. The results have been published in the

journal Climate Dynamics.

Although there is a large body of evidence to suggest that current global warming is largely

due to human activities, much of this has relied on models called general circulation models

(GCMs). GCMs are computer-driven models that are key components of global climate

models, which as the name suggests are used for modeling climate. Although they are

useful tools, some are skeptical as to whether they can really infer connections between

anthropogenic factors and global warming. This, coupled with the fact that there has been a

tendency to over-rely on them when making assertions, has created a need for empirically

based methodologies to complement the GCMs.

Professor Shaun Lovejoy from the McGill University used data from the (mostly) pre-

industrial period (1500-1900) and the industrial period (1880-2000), and calculated the

probability that global warming since 1880 is due to natural temperature fluctuations, rather

than man-made emissions, using statistical analysis.

In order to assess natural variation in climate prior to the industrial period, Lovejoy used

both fluctuation-analysis techniques which allow an understanding of temperature variations

over different time scales, and multi-proxy climate reconstructions. These reconstructions

make use of data derived from sources such as tree rings and ice cores.

To do the same for the industrial period, he used CO production from fossil fuel burning as

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a broad surrogate for all anthropogenic (man-made) forcings. He claimed that this is

justified because of the relationship between the emission of greenhouse gases and

particulate pollution with global economic activity.

The conclusion drawn from the data was clear- he rejected the natural variability hypothesis

with confidence levels of over 99%. It is necessary to understand that rejecting one

hypothesis does not prove another- his data therefore does not prove that global warming

has an anthropogenic causation. However, the results do enhance the credibility of this

ulterior hypothesis.

It is also very important to point out that the confidence levels are likely to be exaggerated

since the data used for the pre-industrial era cannot be 100% certain as measurements

were taken in an indirect manner, since temperature data was not recorded 500 years ago.

Therefore there is a degree of uncertainly in this data, which would inherently affect the

statistical confidence. However, this does not mean that his overall conclusion is invalid, and

this still remains an important study.

The data generated by the study also allowed Lovejoy to make predictions like those

recently published by the International Panel on Climate Change (IPCC). The IPCC predict

that if atmospheric CO levels double, the climate will increase by between 1.9-4.2 C.

Lovejoy’s data complemented this with predictions of temperature rises between 1.5-4.5 C.

While this is just one study, it does add to the ever growing body of evidence that the global

warming we are experiencing cannot solely be attributed to natural fluctuations in

temperatures.

tags climate change, global warming

227 Comments IFL Science Login

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Jai Waddell • 3 hours ago −Climate change would have occurred had we not crawled out of the primordial

ooze, however it would happen at the time or speed it is happening now. We are

affecting the climate and there are very few if any self-respecting scientists who

would deny this out-right. The one point about it that annoys me is that people say

we are killing the Earth. We're not, we are making humans ability to live on the

planet lower and therefore likely killing our own race. The earth will survive and

there will likely be other forms of life that populate the world when we are gone.

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• Reply •

there will likely be other forms of life that populate the world when we are gone.

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• Reply •

Kota • 3 hours ago Jai Waddell

I agree completely.

3

• Reply •

Steven Sullivan • 26 minutes ago Jai Waddell

You're missing a 'not' there in that first sentence: it would *not* happen at

the same time or speed....

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• Reply •

Alan Bean • an hour ago Jai Waddell

Whether or not it is manmade is irrelevant. The issue is that it is already a

problem, and if we want to find some way of surviving on Earth for much

longer, we had best get to solving it.

Also, fun fact about greenhouse gasses: the biggest one IS NOT CO2, it's

H2O.

1

• Reply •

Jeremy • 44 minutes ago Alan Bean

Therefore it is not irrelevant. How are we to solve a problem we do

not know the cause of.

1

• Reply •

Steven Sullivan • 23 minutes ago Alan Bean

So what? Water vapor is the greenhouse gas that makes the

atmosphere most sensitive *to C02*. It is an amplifier of C02's

effect.

• Reply •

Adrian Strzelczyk • 6 minutes ago Jai Waddell

To quote George Carlin: "The planet is fine. The people are fucked".

• Reply •

Sam Coyne • 30 minutes ago Jai Waddell

How the hell are we not killing the Earth? There is a mountain of plastic in

the Pacific Ocean. We have lists of 5-6 species a year that are confirmed

to be extinct. I'm in Michigan right now, and we just had a week of 70

degree weather followed by snowstorms. In mid April. There is a difference

between natural shifts in climate and downright decimation of the climate.

That kind of shift in weather, as well as the various other off-the-charts shit

going on, would NEVER have occurred through a natural process. You sir,

are betting on that 1% opposition I think.

1

• Reply •

Brandon • an hour ago Jai Waddell

Yeah, but.. we are 'actively' wiping out entire populations of other living

creatures besides just humans.. which makes the Earth more Dead

• Reply •

Notorious_bob • 3 hours ago

not to be all "scientist" on you but do you have 100-400 years of statistics PRIOR

to the industrial revolution, or are we just going to speculate coincidence?

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• Reply •

Moonkae • 3 hours ago Notorious_bob

"do you have 100-400 years of statistics PRIOR to the industrial revolution"

Yes, ice cores are mentioned and we can certainly speculate with

reasonable accuracy (based on evidence) what the climate was like

hundreds, thousands, even hundreds of thousands of years ago. Ice cores

are only one example of extrapolating climate data and I'm sure there are

dozens of other methods (tree ring analysis being another).

48

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• Reply •

David A Simpson • 2 hours ago Moonkae

Do you have ANY clue what the resolution of ice core data is? They

can tell one century from another most of the time. They cannot tell

one decade from another with confidence. Two ice cores from a

mile apart will give you a very different "history". Correlating

(averaging) across a number of cores reduces your confidence by

the standard deviation of the data. The "climate community" has

agreed to ignore all of these pesky details and has published an

"official" dataset of the pre-history temperature data. It is an

average of averages with a LOT of barely justifiable assumptions

that altogether results in a confidence level under 70% when looked

at with rigorous statistical methods..

So if the data has a confidence level of 65%, then it is simply

irresponsible to claim that using this data provides a 99%

confidence level--your combined confidence will never be greater

than the product of the confidence level of the underlying data,

unless you are a "confidence man".

The tree ring data is slightly better from sample to sample, but still

doesn't distinguish between, temperature, rainfall, and non-climate

events (e.g. bug infestation, fires destroying trees that are shading

the tree being cored, etc.).

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• Reply •

Jack Ebersole • 2 hours ago David A Simpson

Actually, ice cores are extremely precise from location to

location in terms of gas concentration because

atmospheric gas is evenly concentrated. You don't look at

the average of all ice cores, you look at the relationships

between data of cores taken at different locations. CO2 will

be a little higher in Greenland than Antarctica, but they show

the same rate of change.

8

• Reply • One other person is typing…

Calvin Armstrong • 2 hours ago David A Simpson

Maybe you could enlighten us with peer reviewed papers on

the matter of ice cores

6

• Reply •

Wiz of Oz • 16 minutes ago Calvin Armstrong

http://cdiac.ornl.gov/trends/c...

"±2 years"

• Reply •

CB • 2 hours ago David A Simpson

I've heard that modern sclero-chronology techniques (think

tree rings, but in mollusk shells) allow investigators to see

seasonal fluctuations. There are clearly a lot of factors that

influence local isotope concentrations, but the data still

provides insight into temperature fluctuations.

• Reply •

Michael McDowell • an hour ago CB

That's an interesting subject matter, I'll have to look into it to

see if there is any truth to that suggestion.

1

• Reply •

jnojr • 3 hours ago Moonkae

So, if we KNOW that there were periods that were much cooler or

warmer today… how is it that a slight change in mean temps in a

statistically insignificant period of time "prove" that humans are

causing global warming?

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• Reply • 4

• Reply •

Luca Amerio • 3 hours ago jnojr

3 words: rate of change

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• Reply •

el duderino • 3 hours ago Luca Amerio

... has been fluctuating ever since earth became.

5

• Reply •

haydesigner • 3 hours ago el duderino

… but not to this degree.

Seriously, you deniers have NOTHING to support your

claims.

31

• Reply •

Jeddy B Wilkinson Jr • 2 hours ago haydesigner

I'm not a denyer, but I'm also not fully convinced either. I do

however prefer to err on the side of not destroying the

environment as opposed to uncontrolled industrial

expansion. But I'm not comfortable with how much the

AGW movement has become a religion, including decrying

anyone who questions it in any manner to any degree as a

heretic.

30

• Reply •

Josh Rogers • 31 minutes ago Jeddy B Wilkinson Jr

Exactly!

1

• Reply •

Ryan • 6 minutes ago Jeddy B Wilkinson Jr

James Lovelock, who is the author of "Gaia's Revenge", in

a recent interview with the BBC, actually said something

similar. He thinks that climate science has become to

politicized and referred to it as a religion. He considers

himself as an "old school green."

• Reply •

Joel Jenkins • 2 hours ago haydesigner

Maybe us deniers just don't like the politicization of the

issue where it has become heresy to even ask questions

about it. Maybe we just want to make sure we are getting

the full scope, and the scientific methods being used are

legitimate without an individuals opinion dictating the

interpretation of the evidence. You know, the actual

scientific method. Even if climate change isn't real, I still

think we need to change our ways, learn to recycle better,

find cleaner energies, stop destroying the forest on a

massive scale, etc etc; but I want the evidence for and

against it to be heard equally instead of the lashing of any

scientist who says his/her evidence doesn't add up to

showing proof of climate change due to human activities.

5

• Reply •

Mike Rosenkranz • 2 hours ago haydesigner

There's nothing wrong with skepticism, and I don't see

anybody (here, at least) vehemently denying it. It may very

well be caused by humans, and it seems highly likely, but

that doesn't mean we shouldn't ask how much and how

compelling the evidence is. Climate change has happened

before, and even if it's happening faster than we believe it

has/should, that doesn't necessarily mean that it's our fault.

5

skullnbones • 2 hours ago haydesigner

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• Reply •

skullnbones • 2 hours ago haydesigner

You have not proven yours. Your religion has been proven

wrong for 10 years now with predictions of "Snow

becoming a Thing of the Past" and all your other bullshit

predictions to promote a carbon tax and tell us what

lightbulbs to use. There hasn't been ANY warming for 18

years so time to shut the hell up. Time to get on with getting

rid of corrupt government and wars based on lies. Time for

the "Too Big to Fail Banks" to be ground down into the dirt

by the 99%.Time to take back our countries. Power to the

people, not the money-junkies.

8

• Reply •

Yarrrrrnnnnnnn!! • 3 hours ago Luca Amerio

2 words: Not unprecedented

• Reply •

Anne Maus • 2 hours ago jnojr

You should read the text before commenting ":It is

necessary to understand that rejecting one hypothesis does

not prove another- his data therefore does not prove that

global warming has an anthropogenic causation."

10

• Reply •

FugitiveUnknown • 2 hours ago Anne Maus

Given that he's rejecting the idea that this increase is

natural, actually, that is a pretty good indicator that it is us

doing this.

• Reply •

Mike B DuBaldi • 2 hours ago jnojr

1. Rate of change, which increases atmospheric CO2

concentrations increase exponentially. Yes, it is true that

there are instances of exponential increase in atmospheric

CO2 that pre-date humans(Permian/Triassic Boundary,

and countless others), however such events coincide with

cataclysmic geological/cosmic events; and by cataclysmic

events I am speaking of bolide impacts, or volcanic

eruptions greater than VEI-7, flood basalts. Fact is the

largest volcanic event in the last 250 yrs was Tambora

which fell on the small side of VEI-7 and its atmospheric

CO2 releases have been long recycled out. Has there been

any super-volcanic eruptions since Industrial rev? No. Have

there been any large Asteroid Impacts? No. So what is the

exact cause of this CO2 spike in the last 100 yrs? We are

running out of natural events to blame.

8

• Reply •

basegitar • 42 minutes ago jnojr

Luca is right. Normally these kinds of changes happened

over tens of thousands of years, not 150 years. It also

would be a HUGE coincident if it was by chance that the

Earth happened to warm over the course of 150 years by

the amount one would expect given the amount of CO2 we

know we have put in the atmosphere over the same period

of time.

1

Jack Ebersole • 2 hours ago jnojr

Two reasons

The first is rate of change. This is something that happens

over tens of thousands or hundreds of thousands of years

naturally. To date, it has happened over about 120.

The second is that we're not in the part of the cycle where

we'd be anticipating accelerating warming, we're at the end

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• Reply •

we'd be anticipating accelerating warming, we're at the end

of the end of the ice age and warming should be slowing

down, not speeding up.

1

• Reply •

Guest • an hour ago Jack Ebersole

I honestly say it doesn't matter if we are causing climate

change or not (though I know we are). Our pollution is

fucking up so many other things that we will not survive if

we keep this up. Look at the giant island of garbage in the

Pacific, or the massive radiation spill from Fukushima. Look

at the insanely thick air pollution in China. You think this shit

is just going to go away? It is only going to get worse. We

either start dealing with all these problems, or stop

bothering to survive as a species all together.

• Reply •

Coke • 3 hours ago Notorious_bob

'It is also very important to point out that the confidence levels are likely to

be exaggerated since the data used for the pre-industrial era cannot be

100% certain as measurements were taken in an indirect manner, since

temperature data was not recorded 500 years ago.'

Read the article.

25

• Reply •

Notorious_bob • 3 hours ago Coke

i remain in the "it's plausable" camp which is kind of fence sitting

but i have to rely on what my college science education taught me.

I'm not going to go all "tea bagger" about it nor am I going to wave

an Al Gore flag.

13

• Reply •

Corelin • 3 hours ago Notorious_bob

Why are we more worried about the cause than if we can

solve the problem?

41

• Reply •

Moderate213 • 3 hours ago Corelin

Knowing the cause is a pretty huge part of developing a

solution.

13

• Reply •

dont drink the koolaid • 2 hours ago Corelin

What problem?

We are in a discussion about THIS article and there are no

problems referenced here.

• Reply •

Mike Rosenkranz • 2 hours ago Corelin

Because knowing the cause can help us better understand

how to fix the problem. Treat the disease, not the

symptoms.

• Reply •

Jason K. • 3 hours ago Notorious_bob

Assuming people who accept anthropogenic global

warming are therefore Al Gore supporters *is* going all Tea

Bagger about it.

16

• Reply •

B Wolfe • 3 hours ago Jason K.

Not really.

Anthony Russell Cooke • 3 hours ago Jason K.

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• Reply •

Anthony Russell Cooke • 3 hours ago Jason K.

I think he meant he wasn't going to go to either extreme, not

that everyone who is on one side of the argument is a

particular stereotype.

• Reply •

Tom • 3 hours ago Notorious_bob

Direct instrumental data such as the CET run back to the

1600s. All other data will have been derived from 'climate

proxies', google them.

1

• Reply •

Alex • 3 hours ago Coke

the uncertainty mentioned in the article is the same as the

uncertainty in the measurements Moonkae is talking about. every

measurement has an associated uncertainty derived from a

propagation of error analysis

• Reply •

Quelthias • 3 hours ago Notorious_bob

Yeah, I'm sure that just never occurred to climate scientists. The funniest

part about the debate are those on the denial side who also believe the

Earth is only about 6000 years old, according to the Bible. No amount of

scientific evidence will convince them that the Earth is any older, so it does

not work trying to talk to them for anything. Just don't allow them into the

science classes, and I won't have an atheist doing the Sunday mass.

6

• Reply •

Dustin L. Hopper • 3 hours ago Notorious_bob

Not to be all, you're not a scientist....

5

• Reply •

B Wolfe • 3 hours ago Dustin L. Hopper

So, he can't make an opinion? I wish was the case for everything.

The forums, threads, blogs and every opinion about anything and

everything would be nicely silenced.

2

• Reply •

whataloadofcompost • 3 hours ago Notorious_bob

What's wrong with being all scientist?

5

• Reply •

Sarah Hitterman • 2 hours ago Notorious_bob

Very good sir you nailed it!

4

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