This article originally appeared on the Carbon Brief.

Extreme weather increases the risk of armed conflict in ethnically-diverse countries, a new study suggests.

Around 23% of conflict outbreaks in these countries over the last three decades have occurred during climate-related disasters, such as droughts and heatwaves, the paper says.

The results don’t suggest that weather extremes directly trigger conflict, the researchers say, but that they can be one of many contributing factors.

Carbon Brief speaks to a number of experts to dig a bit deeper into what has become quite a controversial field of climate research.

Climate-related disasters

A host of different factors can increase the risk of armed conflict breaking out in a country. Some examples picked out by previous research include poverty, weak governance, a history of conflict, income gaps between rich and poor, and disputes over natural resources.

The new study, published in the Proceedings of the National Academy of Sciences, suggests that climate-related disasters should be added to this list.

This conclusion stems from a statistical analysis of armed conflicts and the economic damage caused by extreme weather events over the period 1980-2010.

The researchers looked at three categories of climate-related disasters. These include meteorological events (blizzard/snowstorm, hailstorm, tornado, tropical cyclone, winter storm), hydrological events (avalanche, flash flood, general flood, landslide, storm surge), and climatological events (cold wave/frost, drought, heatwave, wildfire).

The results suggest that around 9% of all armed conflicts over the past 30 years have occurred during – i.e. in the same month as – an extreme climatological event.

Taking all three disaster types together, the researchers only found a link when they added another factor – “ethnic fractionalisation” – into their analysis. This is a measure of how how ethnically diverse a country is.

The researchers find that in top-50 most fractionalised countries, around 23% of armed conflicts have occurred at the same time as a climate-related disaster of any kind. 

Other studies of highly fractionalised countries have identified similar links, the paper notes. Prolonged droughts, for example, may have contributed to outbreaks of conflict in Somalia and the ongoing conflict in Afghanistan.

The results suggest that disasters may increase the risk of conflict – though not directly cause it, says lead author, Dr Carl-Friedrich Schleussner, from the Potsdam Institute for Climate Impact Research. He tells Carbon Brief:

“We do not report evidence that climate disasters are directly triggering conflict outbreak, but rather that they may enhance the risk of an outbreak of a conflict rooting in context-specific circumstances.”

While more work is needed to establish exactly how disasters enhance the risk of conflicts, the findings suggest they add pressure to existing ethnic divides, says Schleussner:

“It seems…plausible that such disruptive events fuel smoldering social tensions.”

With extreme weather (pdf) likely to be more intense and frequent as global temperatures rise, the climate could be become a more prominent factor for conflict in the future, says Schleussner:

“Several of the world’s most conflict-prone regions – including North and Central Africa as well as Central Asia – are both exceptionally vulnerable to human-made global warming and characterised by deep ethnic divides.”

This means that a changing climate should be taken into account when developing security policies in these regions, Schleussner says.

No clear picture

The new study adds weight to the link between climate and conflict, says Dr Peter Gleick, an expert on water and conflict at the Pacific Institute, who wasn’t involved in the study. He tells Carbon Brief:

“This paper adds to the growing evidence that climate disruptions can be, and indeed have been, a contributing factor in violent conflicts in the recent past, especially in areas already vulnerable to ethnic, political, or economic disruption.”

But this field of research is still very contested, points out Alex Randall – project manager of the Climate Change and Migration Coalition, who also wasn’t involved in the research. So it’s sensible to view the study in the context of the wider literature.

Many similar studies have focused on specific forms of violence. For example, research has linked drought with riots in sub-Saharan Africa, hot temperatures with violent crime in the US, and flood events with civil conflict in different parts of the world.

But when researchers look at the entire world and all types of violence, there isn’t a clear picture, Randall tells Carbon Brief:

“It’s not possible to say that, universally, climate impacts will lead to more violence.”

For example, huge literature reviews of climate-conflict research, known as “meta-analyses”, have come to different conclusions. A 2013 study of 50 research papers found “consistent support” for a link between the climate and different types of conflict. Yet, another group of researchers disputed this finding, and concluded from their own assessment that the body of research “produced mixed and inconclusive results”.

Even a single climate-related disaster can have more than one impact on the risk of conflict. A study of the aftermath of Typhoon Haiyan, for example, found the crime rate in the Philippines fell in the short-term, before increasing again later down the line. Randall explains:

“The researchers argue this is because of an increase in people helping each other through adversity. But then 12 months later the crime rate increases – probably as people find themselves in deeper poverty.”

However, despite some mixed results from the scientific literature, there is enough evidence to suggest that action to tackle climate change is needed to limit disasters becoming more extreme, Randall says:

“The fact that there is some evidence for climate impacts increasing conflict risk makes the case for [greenhouse gas] emissions reduction even more compelling.”

Ethnicity and history

It’s not just the role of climate in conflicts that needs careful interpretation, says Randall, so too does ethnicity:

“Although it’s true that, historically, many conflicts have erupted along ethnic and religious lines, it is also the case that ethnicity and religion are used and abused by political actors to create divisions within societies where they had not previously existed.”

n other words, it is not diversity itself that leads to violence, but the way that diversity is exploited for political ends, or where different ethnicities are not treated equally. In fact, research suggests that there is no clear link between diversity and conflict.

The study also leaves one question unexplored, says Prof Halvard Buhaug, research professor at the Peace Research Institute, Oslo (PRIO), who also wasn’t involved in the paper.

While the findings suggest that climate-related disasters and conflicts often happen around the same time, there could be a third factor affecting their occurrence, says Buhaug.

The authors point out that there might be a “hidden common cause” behind both, but they don’t go as far as suggesting what that cause could be. Buhaug suggests that a history of conflicts in a country or region would be a likely candidate. He tells Carbon Brief:

“We know that conflict begets conflict, and conflict also is development in reverse – destroying economic activity and material products – thereby increasing the likelihood that a given meteorological event (drought, heat wave, flood) reaches the required level of severity [to cause conflict].”

In other words, a more unstable country is less likely to be able to help its citizens in the aftermath of a disaster – for example, by providing food and clean water – raising the risk of further violence breaking out.

This highlights how important it is to prevent conflict in the first place, says Randall, as well as mitigating climate change:

“There is clearly a massive unmet need for conflict prevention and peacebuilding, and studies like this make that even more important.”

This article originally appeared on the Carbon Brief.