Claim: 2°C temperature increase will make people angry

From Princeton University (with help from Berkeley)

Cool heads likely won’t prevail in a hotter, wetter world

Should climate change trigger the upsurge in heat and rainfall that scientists predict, people may face a threat just as perilous and volatile as extreme weather — each other.

Researchers from Princeton University and the University of California-Berkeley report in the journal Science that even slight spikes in temperature and precipitation have greatly increased the risk of personal violence and social upheaval throughout human history. Projected onto an Earth that is expected to warm by 2 degrees Celsius by 2050, the authors suggest that more human conflict is a likely outcome of climate change.

Caption: Researchers from Princeton University and the University of California-Berkeley suggest that more human conflict is a likely outcome of climate change. The researchers found that even one standard-deviation shift — the amount of change from the local norm — in temperature and precipitation greatly increase the risk of personal violence and social upheaval. Climate-change models predict an average of 2 to 4 standard-deviation shifts in global climate conditions by 2050 (above), with 4 representing the greatest change in normal conditions. Credit: Image by Science/AAAS

The researchers analyzed 60 studies from a number of disciplines — including archaeology, criminology, economics and psychology — that have explored the connection between weather and violence in various parts of the world from about 10,000 BCE to the present day. During an 18-month period, the Princeton-Berkeley researchers reviewed those studies’ data — and often re-crunched raw numbers — to calculate the risk that violence would rise under hotter and wetter conditions.

They found that while climate is not the sole or primary cause of violence, it undeniably exacerbates existing social and interpersonal tension in all societies, regardless of wealth or stability. They found that 1 standard-deviation shift — the amount of change from the local norm — in heat or rainfall boosts the risk of a riot, civil war or ethnic conflict by an average of 14 percent. There is a 4 percent chance of a similarly sized upward creep in heat or rain sparking person-on-person violence such as rape, murder and assault. The researchers report that climate-change models predict an average of 2 to 4 standard-deviation shifts in global climate conditions by 2050.

Establishing a correlation between violence and climate change now allows policymakers and researchers to examine what causes it and how to intervene, said lead author Solomon Hsiang, who conducted the work as a postdoctoral research associate in the Program in Science, Technology and Environmental Policy in Princeton’s Woodrow Wilson School of Public and International Affairs.

IMAGE: The researchers analyzed 60 studies from a number of disciplines that have explored the connection between weather and violence in various parts of the world, and throughout human history. A…

Click here for more information.

“We think that by collecting all the research together now, we’re pretty clearly establishing that there is a causal relationship between the climate and human conflict,” Hsiang said. “People have been skeptical up to now of an individual study here or there. But considering the body of work together, we can now show that these patterns are extremely general. It’s more of the rule than the exception.

“Whether there is a relationship between climate and conflict is not the question anymore. We now want to understand what’s causing it,” Hsiang said. “Once we understand what causes this correlation we can think about designing effective policies or institutions to manage or interrupt the link between climate and conflict.”

The existing research had essentially shown an overall link between climate conditions and these conflicts, but that link needed to be extracted from reams of figures from various disciplines in order for the research to reach general conclusions, Hsiang said. Hsiang, who is now an assistant professor at Berkeley’s Goldman School of Public Policy, worked with co-first author Marshall Burke, a doctoral candidate in Berkeley’s Department of Agricultural and Resource Economics, and Edward Miguel, the Oxfam Professor of Environmental and Resource Economics at Berkeley.

“We attained a huge amount of the data that was available and we used the same method on all of the data so that we could directly compare studies,” Hsiang said. “Once we did that, we saw that all of the results were actually highly consistent — previously they just weren’t being analyzed in a consistent way.”

The researchers examined three categories of conflict: “personal violence and crime,” which includes murder, assault, rape and domestic violence; “intergroup violence and political instability,” such as civil wars, riots, ethnic violence and land invasions; and “institutional breakdowns,” which are abrupt and major changes in governing institutions or, in extreme cases, the collapse of entire civilizations.

Extreme climatic conditions amplified violence in all three categories, regardless of geography, societal wealth or the time in history. An aberrant climate coincided with incidents including spikes in domestic violence in India and Australia; increased assaults and murders in the United States and Tanzania; ethnic violence in Europe and South Asia; land invasions in Brazil; police using force in the Netherlands; civil conflicts throughout the tropics; the collapse of ancient empires; and wars and displacement in Middle-Ages Europe.

“We find the same pattern over and over again, regardless of whether we look at data from Brazil, Somalia, China or the United States,” Miguel said. “We often think of modern society as largely independent of the environment, due to technological advances, but our findings challenge that notion. The climate appears to be a critical factor sustaining peace and wellbeing across human societies.”

And the climate does not have to deviate much to upset that peace and wellbeing, Burke said. The 1 standard-deviation shift he and his co-authors uncovered equates to a seemingly paltry change in weather: it’s roughly equal to warming an African country by 0.35°C, or by 0.63°F, for an entire year, or warming a county in the United States by 2.9°C, or by 5.2°F, for a given month.

“These are pretty moderate changes, but they have a sizable impact on those societies,” Burke said. Many global climate models project global temperature increases of at least 2 degrees Celsius over the next several decades, which, when combined with the Princeton-Berkeley findings, suggest that warming at that level could increase the risk of civil war in many countries by more than 50 percent, the researchers said.

The factors that interact with climate to produce chaos and discord are varied. A popular theory is that drought and flooding cripple an economy, especially one based on agriculture or that is already weak. When people look for someone to blame, governmental leaders have a target on their backs, as do any people with whom there is existing tension, such as an ethnic minority or a migrant group from stricken hinterlands.

But sometimes heat just makes people more aggressive. The researchers found that personal violence was far more influenced by a leap in temperature. Hsiang and his colleagues cite studies that equate excessive heat with spikes of violence in the United States and other stable, wealthy countries. For example, a 1994 study found that two groups of police officers undergoing the exact same simulation training were more likely to draw their weapons if the room was uncomfortably warm.

“There’s a large amount of evidence that environmental conditions actually change a person’s perception of their own condition, or they also can change the likelihood of people using violence or aggressive action to accomplish some goal,” Hsiang said.

“Our study is not saying that climate is the only cause of conflict, and there’s no conflict that we think should be wholly attributed to some specific climatic event,” he said. “Every conflict has roots in interpersonal and intergroup relations. What we’re trying to point out is that climate is one of the critical factors the affect how things escalate, and if they escalate to the point of violence.”


The paper, “Quantifying the influence of climate on human conflict,” was published in Science Aug. 1. The study was funded by a Princeton University postdoctoral fellowship in science, technology and environmental policy, a Graduate Research Fellowship from the National Science Foundation, and the Oxfam Faculty Chair in Environmental and Resource Economics at Berkeley.


newest oldest most voted
Notify of

Well, I’m feeling angry just reading that… :0

Bob B

I guess those people who live in the Florida Keys are just one angry bunch!
Walking along the warm Ocean every morning will just want them to get angry
and down a couple of cocktails.


CACCA has apparently already made certain “scientists” & “journalists” cuckoo.

Richard M

Did they factor in the difference in cultures now? With air conditioning prevalent in many cultures many people no longer experience hot weather directly. In fact, by driving people inside it works more like colder weather from a historic perspective. But hey, what kind of grant are you going to get for making that claim?


In my experience, it is increases from a base that make people grumpy.
If global warming merely raises the base, there won’t be much an increase in global grumpiness.


You know what a 2deg temperature drop will make people? Hungry!


Readers digest version:
“We found a correlation. Correlation does not imply causation but … we found a correlation so there MUST be causation. QED”


So, would someone emigrating from Temperate Britain to much hotter Australia suddenly become a much more violent and criminal person?


,Omitted variable fraud. Unfortunately I cannot tell you the omitted variable; it is illegal for EU citizens to do so. Hint: Rape.


So that explains New Orleans.


Does anyone know how much of climate science is impacts and mitigation compared to cause?


tonyb says: August 1, 2013 at 1:03 pm
“….So, would someone emigrating from Temperate Britain to much hotter Australia suddenly become a much more violent and criminal person?…”
Yeah! Them Aussies are violent, win at all cost b*******s!!!
(Unless they are playing cricket in the current Ashes series, of course).


And before long cats will be living with dogs. In the claim they make they should replace angry with mad. Mad is a better description of this “work.”
How do they explain that people go to the tropics to relax. In my experience people in the tropics, where it is hot and humid, are not as belligerent as the people in the colder climates.


There is an up side to it being too darn hot
According to the Kinsey Report
Ev’ry average man you know
Much prefers to play his favorite sport
When the temperature is low,
But when the thermometer goes ‘way up
And the weather is sizzling hot,
Mister Adam
For his madam.
Is not,
‘Cause it’s too, too
Too darn hot,
It’s too darn hot,
It’s too darn hot.
I am sure that interventionist environmentalists and Paul Ehrlich will see their population control theme fulfilled.
Credit Cole Porter and “Kiss Me, Kate.” (1948).

People fight over resources. Changes in climate change the quantity and distribution of resources. That’s what causes conflict.

Chuck L

What would make me very angry indeed is if they received a grant to produce this piece of fluff.

Gunga Din

Well, if it does go up by 2*C people will be pis… angry because they can’t afford to run their AC because the price of energy will have skyrocketed in a vain attempt to stop the Earth from doing what it would have done naturally anyway.
What do they say will happen when it doesn’t go up by 2*C and people realize they’ve been duped (and they still can’t afford to run their AC)?


Many of us who live in the northeastern US are well acquainted with the “Florida Brain Melt” syndrome. It is experienced by temperate climate folks who move to Florida. This should be worthy of another study.


If this study is right, isn’t it strange that the worst conflicts, WWI and WWII, happend before we had any AGW?

george e. smith

Well no, not exactly; what wILL make me angry; excuse me, that’s very angry, is watching my tax dollars getting wasted on these deadbeats, who figure it’s ok, to ask other people to fund their fooling around with stuff and nonsense, that does just fine, left to itself.
A pushy restaurant server, the other day, told me I was “cheap” because I only tipped her 10%.
Well since she had inflated my bill, by 35%, by adding on to it, the meals consumed by some people at another table she was serving, I thought she was darn lucky to get anything.
So I explained to her, the reality. As a self employed person, living in California, I now pay at least 75 cents on every dollar in taxes. (Federal business taxes on single proprietor small business income is 39.6%).
So I have to earn $4 for every dollar I spend, including on food, or sales tax on food, or tips for servers, who can’t keep a bill straight.
But I did tip her, because she at least is not asking for a lifetime pension to watch the grass grow, and see if it turns brown.

Iggy Slanter

Wait a moment. Wasn’t it just a couple of years ago when the planet’s fevah was supposed to cause permanent droughts? Now its to cause permanent rainfall? How many times am I supposed to groupthink pivot?


Hitler wasn’t evil and delusional he was just hot. Maybe Napoleon was just tired of the rain. Or is it that during a drop in temperatures of a single deviation the general populace is too worried about fulfilling their hierarchy of needs to become unpleasant with each other? Or even more likely, this study belongs in the fiction section.

The paper is a meta-analysis, that is, statistical results from previous papers were combined to obtain a joint estimate. There are three major problems:
First, the authors were rather exclusive in their paper selection. Many studies that do not find a relationship between climate/weather and violence were omitted.
Second, the authors confuse weather and climate. It is true that people are more irritable during unusually hot weather. It is not true that people in hot climates are more irritable. Impacts of weather variability cannot be extrapolated to climate change.
Third, the authors average apples and oranges. They add rape/kelvin to war/kelvin. The result is meaningless.


Whenever I drive my car through a large city and then out into the surrounding countryside, I always look at the digital readout on my car’s thermometer, and often it is 2 degrees cooler in country side — and yes, most country folk are cooler headed than the city folk — so nothing new here, let’s move along.


This will come as a major surprise to the citizens of Singapore.

Mike Tremblay

Did they eliminate all the social factors at play or just ignore them? This type of study is another example of someone forming a hypothesis and then gathering the data which supports their hypothesis while ignoring the data which doesn’t support it. Conflict between people is bound to occur as long as you have two people in one location – the temperature may reduce the time for it to occur but it will still happen. ie. Have you ever seen a hockey game which didn’t have some violence in it?


Wasn’t a good chunk of the Battle of Stalingrad fought at 40 below zero?

John F. Hultquist

Napoleon set the French campaign against Russia in motion on 24 June 1812. That turned out well. As is said, the rest is history. Since then Europeans have had good reason to head to the beaches and cool off when it gets hot.

James Allison

When populations grow in warmer climates they need to compete for food and other resources and that causes conflict. Take for example the Australian Aborigines – very peaceful race until resources dwindled and they then became warlike and started killing each other. Anyway that’s what scientists tell us from their interpretation of rock drawings.


Were they cherry picking people in a moderate state of inebriation for this survey?
You want an instant insufferable arsehole, just add sufficient alcohol (the only relevant temperature variable being the temperature of the beverage as served).

John F. Hultquist

Gunga Din says:
August 1, 2013 at 1:20 pm
“Well, if it does go up by 2*C . . .

* Try using Alt0176 to get the degree sign °
That is on a MS-Windows keyboard; hold Alt down, type the four digits.


I wonder if publication bias contributed to the results ( a lot of “my results led me to conclude my paper AGW will have no effects, let me see if I can get it into Sceince”-research never got published and consequently never made it to Hsiangs paper either). Have someone read the paper and seen if the Authors discuss this?
I feel very skeptic about these conclutions and Im not sure if its common scense or paranoia that prevents me from trusting an article in a reputable journal.

Mann and McKibben are so smart, they live in the 2C world already. That’s why they’re always so angry

“such as civil wars, riots, ethnic violence and land invasions; and “institutional breakdowns,” which are abrupt and major changes in governing institutions or, in extreme cases, the collapse of entire civilizations.”
Katrina hurricane already caused a major change in our institution.
Institutional breakdown.
Send 7200 National Guard who are fighting overseas. Woops, forgot, we don’t have ’em got them over there $$$ for Carlysle Group. Scores of police and firefighters who had volunteered to help rescue people were sent to Atlanta for 2 days of training classes on topics including sexual harassment and the history of FEMA. Dick Cheney pretty much forces the manager of the Southern Pines Electric Power Association to divert power crews from working on getting power for two hospitals, moved them to electrical substations to Collins, Mississippi for the operation of the Colonial Pipeline, which carries fuel from Texas to the Northeast.

Gunga Din

John F. Hultquist says:
August 1, 2013 at 1:41 pm

Gunga Din says:
August 1, 2013 at 1:20 pm
“Well, if it does go up by 2*C . . . ”

* Try using Alt0176 to get the degree sign °
That is on a MS-Windows keyboard; hold Alt down, type the four digits.

Thanks for the tip. I can’t guarantee I’ll remember the next time I want to make a “°” sign.

This is a kooky take-off on what we do know for sure. Density of population makes animals, and people, crazier. But there is no benefit is promoting facts; everything defaults to the great non-problem of warming. Warm temperature is something everyone gets used to.
People dying and starving is much more stressful than learning to take siestas or work during cooler hours.

kadaka (KD Knoebel)

I want them to study the possible anger and violence when people armed with axes and saws argue over the last remaining trees in a forest, that they desperately need to keep their families from freezing in winter, because all coal use is effectively banned, electricity is rationed and expensive when available at all, and they can’t afford the “carbon credits” sold by the well-connected licensed brokers to use any other fossil fuels they might come across, if they could ever pay the permit fees to merely apply to be “carbon releasers”.
Of course the conclusions will be anger and violence will decrease once the regulations are once again “administratively re-interpreted” to cover any “vigorously exothermic” release of carbon from long-term storage to the atmosphere, thus wood burning is also effectively banned, thus axes and large wood saws may be legally confiscated as having no non-governmental purpose, thus there will be nothing to fight over and less to fight with.
Also on the plus side, this will result in more cows and goats being adopted as pets, as during the day they can be fed useless gathered grass and leaves, then snuggled up to for warmth at night. Morning joke: “Wow, did you get awake horny or… Oh, that is a horn.”


And here I thought cold would cause food shortages which would cause famine, disease and pestilence; at least that’s what my history books tell me.


That would be why Australia has such a high crime rate, and Australians are so pushy and violent, then?
Living here in the tropics as well, I guess that is why everybody here is so uptight and tense.
Just think it through for two seconds…

Looks like the Editors at Bloomberg thought this was such a good solid piece of research that they posted it on their Home page…
Lets all have a go at them shall we…?

Only in the fantasy world of the Left could such an idea even occur to anyone.

Mike Smith

This is so stupid but so dangerous. Policy makers will lap up this nonsense in order to further their progressive social engineering agendas.


This same 2 degrees is the new perpetual motion machine for the publication mill.

Janice Moore

“‘Establishing a correlation between violence and climate change now allows policymakers and researchers to examine what causes it and how to intervene,’ said lead author Solomon Hsiang… .”

Pitiful, nonsensical, mutterings of a drunken fool.
Hsiang: [paraphrased] More human conflict [hic] is a likely outcome of climate change. [2nd paragraph] Now, the government can determine what causes it.
WUWT: “What causes it” ?!!! You big dope, you just said climate change causes violence.
H: [robotically] The government can now intervene.
WUWT: Intervene to do what?
H: [monotone, glazed stare] To determine [SNAP! — WUWT snaps fingers in H’s face] …. [eyes brighten, sane look on face of H] to determine how to “control the people” by pretending human CO2 makes people super-mad….. [monotone returns, eyes glazed]…. people …. made………….. things…………………………[eyelids drooping, slumping over in chair]………… ninety…. [yawn, eyes close]…….. seven…. . [CLUNK — falls off chair, snoring on floor]
WUWT: H! H?? H!!! [shakes him, won’t wake up] You’re DRUNK! I KNEW it.
We KNOW it. Condemned out of their own prevaricating mouths, they are either drunk, or……………. lying (again).

Where did all the Prop 30 money go? Wasn’t that money supposed to solve all problems? The problem is that this money was given to administrators to do with as they wish. We’re seeing the results of where the money went right now. The approach taken by administrators is to moan about not having enough money so that the taxpayer will give them more; there is no incentive to actually fix problems.

Tim Clark

Here in Wichita, people always fight during a thunderstorm.


Hot and bothered in Chicago…wait… what ?
“Never in 142 years of official weather observations in Chicago has a July 23-29 period been as cool as the one just completed. Temperatures during that time frame averaged 65.6-degrees—well below the long-term average of 74.5.”
Now I’m out of excuses to be angry…., which is an excuse in itself !!


I have read that any event they may occur in any population of anything will tend to increase in direct proportion to the square of the number in the population. I suppose that is because random contacts will increase according to that ratio. The population of the earth was 2 billion in the twenties and 7 billion now,
Was the treatment of populations within a confined area treated uniformly in all studies?

Lewis P Buckingham

Well at least it goes with the Australian ‘angry weather’ narrative that we are supposed to be experiencing.
The East Coast has had some delightful winter weather, warmer than average, but people don’t seem to be fighting.
I am a bit worried though.People from the Southern states will be migrating to Queensland in the sub tropical to tropical zone at Christmas.
That’s well over a 2 degree centigrade jump.
If they read this study they should all be going for a fight, not to relax.
But then,what would they know?

When I’m working out in the freezing cold, which I did in December 2011, I was called out to replace about 40 out side light bulbs and electronic parts around an old peoples home, at 8:30 in the morning I was up a freezing cold ladder trying to use a freezing cold set of Allen-keys to open poorly designed light fittings, when I’d nip my fingers (which I did a lot that morning) I was made incredibly angry. I was angry with the designers of such a badly designed product and getting a cold nip is the worst, the local temperature was about 1C that morning, a 2C rise in global temperature would not have made any difference.
If the local temperature for that day was between 20C to 27C I would have been fine, getting the odd finger nip is expected but in colder conditions it is more painful.
BTW. I didn’t select or install the florescent so-called “Eco-light bulbs”, electronic parts and badly designed fittings which were not suitable for the freezing outdoor temperatures, which was why I was called out.