When we think about climate change, plenty of direct consequences spring to mind: rising temperatures, extreme weather, melting ice caps, shrinking habitats for wildlife. Some effects, however, are perhaps not so obvious.

Kate Guy is a DPhil candidate in Oxford's Department of Politics and International Relations, researching the links between climate change and threats to national and international security. If international efforts to address global temperature rise have thus far largely been about negotiation and cooperation between states, what happens if the effects of environmental change threaten to derail that cooperation? Will scarcer resources lead to increased conflict and competition between and within nations? And how can governance be maintained against a backdrop of increased environmental and economic 'shock'?

A research fellow with the Washington DC-based Center for Climate and Security, and previously an expert working on the negotiation of the UN's Sustainable Development Goals, Guy (née Offerdahl) is looking systematically at the security risks associated with climate change across a variety of warming scenarios.

'It's a topic of growing importance as the impacts of climate change become more pronounced,' says Guy, who also works as a research assistant to the Dean of Oxford's Blavatnik School of Government. 'In the US, the Pentagon and intelligence communities have been giving climate risks increased attention. The UN Security Council has also started to look at climate change as part of its most high-profile security deliberations.'

Through her background in politics and policymaking, Guy has witnessed first-hand the international efforts to 'negotiate our way out of climate change'. But she has also seen the opposite taking place.

'Having come from this world working in international institutions and diplomacy, I became interested in how climate change could begin to have a detrimental impact on cooperation,' she says. 'My research considers how states might shift their alliances and security relationships in the face of widespread climate change, and which climate risks are most threatening to the current global order.'

According to Guy, the effects of climate change – direct and indirect – that are likely to have an impact on national and global security include extreme weather events, pressure on resources and crop yields, sea level rise, the spread of disease, economic instability, population migration and radicalisation, and even potential mitigation efforts such as the use of geoengineering and nuclear technologies. 

'The security community classifies all of these climate impacts as “threat multipliers”,' says Guy. 'It's often difficult to demonstrate direct causality between climate change and shocks, and they may not be severe threats in and of themselves, but in combination they could have serious consequences on the ground. There are also threats of what we call “fat-tail risks”, which are high-impact but low-probability events – like the potential collapse of the West Antarctic ice sheet, which would lead to catastrophic levels of sea level rise globally.'

The most pressing and useful task for researchers, she adds, is scenario planning – in particular, looking at those regions and areas facing the biggest overlap of climate risks and considering their security implications. 'For example, in an extreme scenario of 4°C temperature rise, which our current emissions put us on track to reach, we're likely to see widespread drought and crop failure, which could lead to political instability in states whose governance is already fragile. One of the saddest things about climate change is that the places likely to be most vulnerable to shocks are often the places that are less economically developed and therefore less able to adapt to environmental change. In the Sahel region of Africa, for example, we're already seeing increased violence and fighting over scarce resources in the context of prolonged drought and food insecurity.'

What’s really interesting in terms of projecting the security implications of climate change is that we are able to use sophisticated climate prediction models to look into the future – including lots of fantastic work being produced right here in Oxford.

An increase in the fragility of states is a common prediction among those who study the effects of rising temperatures. 'It's been suggested that a half-degree increase in temperature leads to a 10% to 20% increase in intergroup conflict,' says Guy. 'We're already living with some of the consequences of climate change: we've experienced about a one-degree rise in temperatures from pre-industrial levels, and it's estimated that climate and natural disasters in 2018 alone pushed another 29 million people around the world into food insecurity. We need to mitigate immediately and keep ourselves under the threshold of 1.5°C, because if we allow climate change to spiral out of control then the effects on the ground will quickly spiral out of control as well.

'I don't believe we have the global institutions in place at the moment to deal with a climate-changed world, and nor do I think our existing treaties and alliances will be applicable in a world in which resources are highly constrained and shocks are frequent.'

State rivalry is already on the rise, says Guy, citing the example of the Arctic Council. An innovative intergovernmental forum, the Arctic Council was set up to discuss the issues affecting the Arctic region, with representation from indigenous groups and observer states at the table. 'What we're seeing now – and what I'm predicting is likely to happen around the world – is a breakdown in cooperation among the Arctic Council members as the region's sea ice rapidly melts, resulting in shipping routes and access to drilling becoming open for longer periods each year. Countries are not necessarily coming to international fora in good faith anymore, because the push and pull of self-interest takes precedence.'

There are, however, some reasons for optimism. Guy says: 'One bright spot is that there is evidence that these risks and shocks could, if we handle them correctly, lead to the creation of new and improved spaces for international cooperation. Take the 2014 international response to Ebola, for example. It was a terrible global shock with enormous loss of life, but the international community came together relatively quickly to contain the virus and create innovate new solutions. That could be a model for similar future shocks.'

She adds: 'What's really interesting in terms of projecting the security implications of climate change is that we are able to use sophisticated climate prediction models to look into the future – including lots of fantastic work being produced right here in Oxford. What we haven't done well is link this research into an understanding of climate change's second-, third- and fourth-order effects. For example, what would a one-foot sea level rise mean for the governance and security of the affected regions? We haven't yet collaborated enough across the hard and social science disciplines to answer these questions, but there's a great opportunity there – particularly in a place like Oxford.'