New tests seek peace in climate conflict blame game

Researchers are hoping to work out how climate change affects risk of conflicts, such as the one in Somalia in which this tank was destroyed. Image credit: Carl Montgomery, via Flickr Creative Commons license

Researchers are hoping to work out how climate change affects risk of conflicts, such as the one in Somalia in which this tank was destroyed. Image credit: Carl Montgomery, via Flickr Creative Commons license

After researchers last year went through every paper linking climate changes and human violence, finding a strong connection, new findings suggest that one rare study disagreeing used the wrong maths. Kyle Meng from Princeton University in New Jersey and Solomon Hsiang from the University of California, Berkeley, now hope they’ve settled previous conflicts over the climate-conflict link. “We think this allows the community to move forward onto what I believe are the next set of important questions,” Kyle told me. “Why exactly does climatic change affect violence and what can we do to lessen the effects of climate on violence?”

In last year’s paper, Solomon and his Berkeley colleagues Ted Miguel and Marshall Burke brought together 45 sets of evidence spanning 10,000 years. Reanalysing worldwide measurements from scratch they found that 2°C global temperature rise could make conflicts like civil wars more than 50% more common in many parts of the world.

One paper that didn’t fit with their findings had been published in 2010 by Halvard Buhaug at the Peace Research Institute Oslo, Norway. Halvard’s study used the same data as a 2009 paper that found a climate-conflict link in Africa, written in 2009 by a team including Ted and Marshall. However, Halvard used different models indicating that political and economic factors were more important and that climate was ‘not to blame’.

Halvard’s argument revolves around a mathematical ‘robustness check’ into the statistics used by the 2009 paper. Such checks are common in social science, Kyle explained. “However, it is important to note that not all robustness checks are valid,” he said. “In general, robustness checks are designed to examine whether, given a particular outcome, a statistical model may be producing biased results, such as when improper comparisons are being made amongst observations.”

War by numbers

Princeton University's Kyle Meng has given Halvard Buhaug's 'robustness check' of research on the climate-conflict link a robustness check of its own. Image credit: Kyle Meng

Princeton University’s Kyle Meng has given Halvard Buhaug’s ‘robustness check’ of research on the climate-conflict link a robustness check of its own. Image credit: Kyle Meng

In a Proceedings of the National Academy of Sciences of the USA paper published Monday, Kyle and Solomon argue Halvard’s checks actually increase bias. Their first criticism is that the statistical models he uses overlook differences between countries in the original study and assume they’re all the same. And Halvard then looks at different ways to measure the conflicts that climate might affect. In the original 2009 paper, Ted and Marshall’s team had counted years during which there has been conflict in a country. But they had only looked at large conflicts, with over 1,000 casualties in a year, missing out civil wars like the one in Sierra Leone between 1991 and 2000. So Halvard included conflicts with at least 25 battle deaths a year.

But there’s a big probability difference between the two measures, with wars causing over 1,000 deaths happening only once a century per country in Africa. Conflicts causing at least 25 deaths happen every four years per country. Kyle and Solomon argue that probability difference needed to be considered in Halvaug’s statistical model, but wasn’t, and means he wasn’t making a fair comparison. “Think of the original main result as equivalent to saying ‘smoking causes lung cancer’,” Kyle explained. “This amounts to stating that ‘smoking may or may not cause breast cancer’ – the two measures are different and may be caused by different factors.”

So, taking the same original data that Halvaug used, Kyle and Solomon looked at 25 death-per-year conflicts, but this time doing what they think are the right statistical calculations. They also examined the effect of assuming no difference in conflict likelihood between African countries, and compared the results to the 2009 paper. In that original study, Marshall and Ted’s team had found that a 1°C global temperature rise would make 1000-death-per-year wars in Africa 40% more likely. Switching to the 25 death-per-year measure and assuming no country differences made the uncertainty range so vast that they could not say Halvard’s paper disagreed with that original finding. Having done this using statistical tests, including one called an F-test, Kyle and Solomon urge other researchers to use their methods more often.

Polite fight

Halvard Buhaug from the Peace Research Institute Oslo in Norway doesn't feel his paper has been proved wrong, but doesn't reject the idea of a climate-conflict link either. Image credit: PRIO

Halvard Buhaug from the Peace Research Institute Oslo in Norway doesn’t feel his paper has been proved wrong, but doesn’t reject the idea of a climate-conflict link either. Image credit: PRIO

Unsurprisingly, Halvard doesn’t agree that the new paper shows his earlier one was wrong. “They include a couple of ‘tests’ that make little sense in this particular context but derail the attention from what should be at the core: the extent to which temperature is robustly associated with conflict risk,” he argued. He added that it’s Kyle and Solomon doing the wrong maths: they shouldn’t compare his paper with Marshall and Ted’s, but with the “null hypothesis” that temperature doesn’t affect conflict. In that context, the huge uncertainty ranges in the latest paper would suggest “temperature is not robustly and significantly related to civil conflict”, he said.

While Halvard stands by his work, he stressed that he does think that climate can contribute to causing conflict. “I certainly do not question anthropogenic climate change and I also do not dispute the notion that climatic extremes may be associated with certain forms of political violence under given conditions,” he says. “It’s just that we haven’t yet been able to pin down all the unknowns in such a complex causal relationship. But we will, eventually.”

The continuing debate, even as Solomon, Kyle and their colleagues expand their dossier of evidence linking climate and conflict, is typical of the way science hammers ideas into shape. And though Kyle is confident in his new paper’s findings, he highlighted that the desire to get deeper into the workings of the link unifies all the scientists. “To use our earlier example: we’re now able to state that ‘smoking causes lung cancer’, but we are far from being able to explain why exactly this occurs and what type of intervention can be employed to lower lung cancer risks,” he explained. “At the end of the day, we’re all on the same team, trying to understand a fiendishly complicated aspect of our world. Now that the existence of the relationship has been solidly established, we’ll need everyone in the research community, of all backgrounds, to find out why is this going on and how might we address it.”

Journal references:

Marshall B. Burke, Edward Miguel, Shanker Satyanath, John A. Dykema and David B. Lobell (2009). Warming increases the risk of civil war in Africa Proceedings of the National Academy of Sciences of the USA DOI: 10.1073/pnas.0907998106
H. Buhaug (2010). Climate not to blame for African civil wars Proceedings of the National Academy of Sciences of the USA DOI: 10.1073/pnas.1005739107
Solomon M. Hsiang, Marshall Burke, Edward Miguel (2013). Quantifying the Influence of Climate on Human Conflict Science DOI: 10.1126/science.1235367
Solomon M. Hsiang and Kyle C. Meng (2014). Reconciling disagreement over climate–conflict results in Africa Proceedings of the National Academy of Sciences of the USA DOI: 10.1073/pnas.1316006111
Halvard Buhaug (2014). Concealing agreements over climate–conflict results Proceedings of the National Academy of Sciences of the USA DOI: 10.1073/pnas.1323773111

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4 Responses to “New tests seek peace in climate conflict blame game”

  1. rpauli Says:

    Thanks for the overview report.

    Gosh, here we are just a few years into the progressive destabilization of global climates – trapped in calamities greater than ever before seen in human history. Not just written history, but the history of our species. No matter what we do, it will get worse, we have no precedents for either environmental or social disruption.

    Now, the past has lesser and lesser relevance to the future. And this handful of ambitious young academics.thinks it has things figured out. I might invite them to do the same studies in just a few years.

  2. Scottish Sceptic Says:

    Hi, I can’t find out how to contact you, so I’ll leave this as a comment.

    I am writing to you on behalf on the Scottish Climate & Energy Forum, we are conducting a survey of those interesting in the climate debate. The aim of the survey is to understand the nature and background of those interested in the climate debate online. It will provide an invaluable insight into the education and work experience of participants, test the relevance of politics in forming views and assess employment and social factors for their relationship with views on climate.

    We would be very grateful if you would take the time to complete the survey and publicise it on your blog. The responses are confidential.

    The url is:

    http://scef.org.uk/survey/index.php/868721/lang/en.

    If you would like to be kept up to date with this survey please email or have any questions or suggestions, please do not hesitate to contact me.

    regards,

    Mike Haseler

    • rpauli Says:

      I dunno, it seems like you have a well defined agenda. I took the test and then found out from your home page that you have quite a deluded science that you seem to be promoting. :

      ==========================================================

      Survey on participants of climate debate

      The Scottish Climate & Energy Forum have been working to produce a survey on the background of participants in the climate debate. Now, after some excellent feedback, the survey is ready. The url is:

      http://scef.org.uk/survey/index.php/868721/lang/en.

      Please help us by filling in the survey and passing onto all those who are interested in climate on line.

      The aim of the survey is to understand the nature and background of those interested in the climate debate on line. It will provide an invaluable insight into the education and work experience of participants, test the relevance of politics in forming views and assess employment and social factors for their relationship with views on climate.

      regards,

      Mike Haseler
      Chairman
      2 Comments
      Submission to House of Commons Energy & Climate Committee on the IPCC

      This is just a short post to provide a link to the submission to the House of Commons Climate & Energy Committee inquiry into AR5 and the IPCC.

      0 Comments
      Report: Lecture by Prof Salby 7th Nov 2013
      Climate: What we know and what we don’t

      downloadable version

      Professor Salby giving his presentation on 7th November 2013
      to the Scottish Climate & Energy Forum.
      produced by Mike Haseler BSc. MBA
      Summary

      In order to understand the importance of the evidence presented by Salby it is necessary to understand the case for attributing the recent rise in CO2 to human emissions. This starts with the assertion that man-made, rather than natural, emissions of CO2 can be shown to be the cause of the recent rise in atmospheric CO2 because:

      The recorded rise in CO2 from 1958 of about 100ppm is larger than anything apparent in the proxy record. This “unprecedented” rise is seen as a fingerprint of recent human activity

      The ratio of carbon 13 to carbon 12 in the atmosphere has decreased since 1830. This was thought to be due to the burning of fossil fuels which have a lower ratio of carbon 13. As such the reduction in the ratio was thought to be the “fingerprint” of man-made emissions.

      And then it is argued that this rise in CO2 is causing global warming because:

      CO2 and temperature move together in an apparent relationship in the proxy records

      In his lecture Salby showed:

      Whilst there is a good fit in the ancient record from proxy ice-cores, the measurements of recent global temperature is poorly correlated with the measured level of CO2.

      Instead, net emissions of CO2 (not the level) is more closely related to temperature.

      If we model surface conditions with temperature & humidity in the atmosphere:

      net emissions of CO2 can be predicted from surface conditions

      net emissions of Methane can be predicted from surface conditions

      net emissions of Carbon 13 can be predicted from surface conditions

      Evidence shows that the sources of atmospheric CO2 (as shown by areas with highest concentration) are not related to man-made emissions from burning fossil fuels.

      The evidence shows Carbon 13 is not a fingerprint of human emissions.

      The IPCC are wrong to say: “all … increases [in CO2] are caused by human activity.” or “the increased atmospheric CO2 concentration is known to be caused by human activities”.

      In significant part, changes in the level of CO2 are controlled by global temperature.

      Furthermore he proposed a mechanism to explain the anomaly between the behaviour of CO2 in the actual atmosphere and that seen in the proxy record from the ice core. This was that there was a non-conservative damping mechanism such as diffusion or loss in removal of the ice core.

      Non-conservative influences would cause past atmospheric CO2 to be significantly underestimated, so it is likely that the recent rise in CO2 is not unprecedented.

      All the recent history of CO2 can be explained from surface conditions alone.

      0 Comments

      Read more: Report: Lecture by Prof Salby 7th Nov 2013
      The Sceptic View

      The Sceptic view is the final statement published 6th May 2012 prepared after a discussion on the blog Scottish Sceptic by a number of regular contributors to that blog as well as others who participated from Wattsupwiththat , Bishop Hill and other blogs. It was an agreed statement by those participating in the discussion. As such it represents the most authoritative statement of the views of Climate “Sceptics”/”Skeptics” as of May 2012.”

      • rpauli Says:

        Too bad. If the Scottish Sceptics cannot learn from the climate science, then I am not sure they can learn from the data of an opinion poll. Now I think we should skip the tests… call it “why bother” on the test. So maybe “All global warming is just a human misperception”??


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