Study finds link between climate and conflict

By Laura Shin | August 24, 2011, 10:00 AM PDT

Source: SMART PLANET

People have long speculated that changes in climate can affect human society. For instance, many ancient civilizations, including the Mayan, are thought to have collapsed due to drought.
Now, a study shows that shifts in global climate can also destabilize modern-day societies.
Columbia University researchers have found that an El Niño, which brings hot, dry weather, doubles the likelihood of a civil war in more than 90 tropical countries affected by this climate cycle.
The authors, who are publishing their study in Nature on Thursday, say that El Niño may have played a role in one in five civil conflicts since 1950.
“We’re extending the general hypothesis that throughout history human societies used to be influenced by the climate to say that, now, modern society continues to be influenced by the modern climate …. It wasn’t so difficult to convince people that maybe Angkor Wat or Mayan civilizations collapsed due to climatic changes, but I think it’s harder for people to accept that we still depend on the climate to a very large extent,” author Solomon M. Hsiang, who is now at Princeton, said. (Disclosure: I know Hsiang from a class I took at Columbia University for my master’s four years ago; he was the teaching assistant.)
While Hsiang and his co-authors emphasize their study focuses on the El Niño climate pattern, not climate change, their work could shed light on the potential consequences of global warming, which will make the world more El Niño-like: hotter and drier around the middle.

The connection between El Niño and warfare

El Niño and La Niña are two sides of a weather pattern that oscillates every three to seven years. During El Niño years, tropical parts of the globe become hotter and thirstier than they are during comparatively cool, rainy La Niña years.
The researchers found that the likelihood that a country in the tropics erupts into a civil conflict is 3% during a La Niña year, but 6% during an El Niño year. Countries whose climates are largely unaffected by El Niño only had a 2% chance of experiencing a civil conflict no matter the year.
Hsiang and his co-authors, Kyle C. Meng of Columbia and Mark Cane of Columbia’s Lamont-Doherty Earth Observatory, did not analyze international conflicts because civil wars constitute the vast majority of all conflicts since 1950.
The map below shows, in red, the 93 countries that become warmer in El Niño years, and the 82 unaffected countries in blue.

While Hsiang does not say that El Niño causes these conflicts, he asserts it creates the conditions that make warfare more likely. He compared the presence of El Niño during a conflict to the presence of ice on a road during a car accident:
When there is more ice on the road, there are clearly more car accidents …. Does the ice cause car accidents? The truth is that drivers and their mistakes create car accidents, and the ice is not necessarily at fault, but the ice increases the likelihood with which drivers will make errors.
He, Meng and Cane speculate that the hotter, drier conditions of an El Niño indirectly lead to conflict in several ways: drought could cause large crop losses, which would in turn increase food prices and spark unemployment — and the unemployed have more time to contemplate injustices and act on them. The researchers also cite evidence that hotter temperatures have physiological effects on people, making them more likely to instigate violence.

Import for climate change

Although this study did not look directly at the consequences of global warming, it could portend its impacts and be used to improve preparedness for humanitarian crises, because strong El Niños, which have the greatest connection to warfare, can be predicted up to two years in advance.
Hsiang, Meng and Cane learned from and built upon a widely criticized 2009 study by Marshall B. Burke and others that examined the effect of local climate cycles on conflict in Africa. In anticipation of similar attacks, Hsiang’s team controlled for factors such as country’s income, level of democracy, population, etc. They ran all the checks that the Burke study ran, as well as all the checks that a subsequent opposing study ran. Even then, the El Niño influence persisted.
Hsiang says that Burke’s study tried to see what might happen in the future climate of individual countries by looking at local weather and rainfall — i.e., if a country became slightly hotter than its neighbors, would it be more likely to have a civil conflict?
“But local weather and local rainfall are not good approximations of global climate change,” he says, noting that global climate causes large patterns of environmental changes. For instance, a spate of recent related weather disasters has led to a spike in food prices. “When an El Niño event occurs, it leads to warming and drying throughout the entire tropics. It leads to a reduction in agricultural output throughout the entire tropics. And it is very likely that … each individual society is affected … when agricultural production is falling everywhere at the same time.”
Cane says:
We can’t say what will happen for sure with climate change, but it does show beyond a doubt that even in the modern world, climate variations have an impact on people’s propensity to fight. It is difficult to see why that wouldn’t carry over into a world disrupted by global warming.
photo: Nubian desert in Sudan (Bertramz/Wikimedia)
map: Hsiang et al. Nature

Study fingers climate change as cause of recent heat waves

By Laura Shin | August 13, 2012, 3:03 AM PDT

It’s long been a tenet of climate science that specific weather events cannot be attributed to climate change.
But a prominent NASA climate scientist and advocate for policies to combat climate change, James E. Hansen, has now come out with a paper that upends that scientific conventional wisdom.
Using a statistical analysis, Dr. Hansen, the head of NASA’s Godard Institute for Space Studies in Manhattan, and his colleagues found that specific heat waves of recent years – the Texas heat wave in 2011, the Russian heat wave in 2010 and the European heat wave of 2003 – were so out of line with what had traditionally been considered natural variability that they must have been directly caused by climate change.
Additionally, he published an op-ed in the Washington Post asserting that once this summer is over, the U.S. heat wave and drought will also likely be found to be a direct result of climate change.
“I don’t want people to be confused by natural variability — the natural changes in weather from day to day and year to year,” Dr. Hansen said in a press release. “We now know that the chances these extreme weather events would have happened naturally — without climate change — is negligible.”
The paper has divided climate scientists for two reasons: One is simply Dr. Hansen’s visible role as an advocate for action to mitigate climate change. The other is the fact that the paper did not rely on climate science to pinpoint climate change as the cause of these heat waves but simply on math and statistics.
Some felt he had come up with a new way to understand climate extremes and others asserted that he had simply put a new spin on old data.

The study

The paper, published in the Proceedings of the National Academy of Sciences, looked at how temperature varies within a season, and how that variability is changing.
Dr. Hansen and his co-authors, who included Makiko Sato, also a NASA scientist at the Columbia University’s Earth Institute, and Reto Ruedy, of Trinnovim LLC, which provides scientific support for NASA, looked at the climate variability of the years from 1951 to 1980, and contrasted that against the variability of the years since.
They compared how much of the earth’s land surface was under what would have been considered extreme heat from June through August of each year.

From 1951 to 1980, only 0.2% of land surface experienced these heat waves.
But in the years 2006 to 2011, 4% to 13% of land surfaces experienced extreme heat.

They concluded that the heat waves during those years would not have occurred were it not for the greenhouse gases warming our planet.
Therefore, the paper did not show, using climate science, how climate change caused each of those events, but instead looked at the likelihood of these events happening without the presence of climate change and decided that climate change was the only plausible cause for them.

Good science? Or spin?

Scientists were split on whether they agreed with the way Dr. Hansen and his co-authors reached his conclusions.
Andrew Weaver, a climate scientist at the University of Victoria in British Columbia told the Associated Press that the study reframes the way we think about extreme weather in relation to climate change:

“Rather than say, ‘Is this because of climate change?’ That’s the wrong question. What you can say is, ‘How likely is this to have occurred with the absence of global warming?’ It’s so extraordinarily unlikely that it has to be due to global warming.”

But not all scientists were so convinced. Peter Stott of the U.K. Met Office, who co-authored a landmark study on the 2003 European heat wave, had previously found that global warming made it much more likely this type of heat wave would occur, but still attributed some of the cause to natural variability.
Other scientists not involved in the study, pointed out that that the increase in heat extremes demonstrates an overall shift toward warmer global average temperatures, not a change in climate variability.
“The one stretch in the paper is in the linking of the increase in areal extremes to an increase in climate variability,” Gavin Schmidt, a climate scientist who works with Dr. Hansen at GISS, told Climate Central.
What do you think? Did Dr. Hansen come up with a new way to understand climate variability or did he just tell a new tale using old data?

Related on SmartPlanet:

via: The Washington Post, The New York Times, Proceedings of the National Academy of Sciences, Climate Central
photo: DI91m/Wikimedia

Source: SMART PLANET

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