Last week, countries agreed to address the problem of climate change for the long term, rather than as a stop-gap measure, to eliminate greenhouse gas emissions in the second half of this century. We must celebrate their effort.

However, security impacts of climate change show how its consequences can slip wildly beyond our control and understanding by spilling across borders and creating new consequences. It is vital, therefore, that civil society groups including my own, the Global Military Advisory Council on Climate Change (GMACC), hold governments fast to their targets and explain the consequences of failure.

Climate change has both direct impacts and indirect consequences which together present a new challenge for which we have no training. Direct climate impacts include more frequent extreme weather, from the poles to the tropics, from the coasts to the small island states like Tuvalu to the ceiling of the world in Nepal. No country is too big or small, or isolated from the problem.

To illustrate, in the past two weeks we have seen costly floods, especially the devastating and deadly one in India and also in Britain. While climate change may reserve its worst pain for developing countries, it will impact everybody.

And that global, systemic risk becomes clearer when we consider the indirect effects. Where people are unsafe, they will seek shelter and move as the migration of the troubled people across Europe this year shows.

It is not speculation to implicate climate change in the Syrian civil war and a subsequent mass migration across Europe. Syria experienced its worst recorded drought from 2006 to 2011, in turn displacing farmers from scorched fields to over-crowded cities, stirring unemployment and unrest, and ultimately civil war. A recent study showed how a long-term drying trend in the eastern Mediterranean, caused by climate change, had made the Syrian drought twice as likely.

Neither is it speculation to draw a further link to the rise of ISIS. We know that marginalised people, in this case uprooted by extreme drought, are a recruitment opportunity for extremist and terrorist groups. We have seen how these groups reach the victims of natural disasters first before the state by responding to and then exploiting their plight.

We have seen the impacts: regional conflict, and mass migration. There are now almost three million Syrian migrants in Turkey, or 4% of the population, while a million more are making their way to or are already in Europe. Such migration is not only a problem of human security, but threatens the stability of bordering countries, including Turkey, Lebanon and Jordan, which are becoming overwhelmed.

Similar examples abound, where local, climate-related disasters have unravelled on a global scale. Scholars calculate that the Russian heat wave of 2010 was made more acute by climate change. By destroying the nation’s wheat harvest, it triggered an export ban and higher global food prices, which in turn saw street protests on the other side of the globe, and provided a catalyst for the Arab Spring.

By inflicting social and economic shocks, climate change can also spawn disease, especially in weakened, fragile states, where problems escalate so easily.

Water shortages may illustrate best how climate change threatens our most basic needs. At present we are at risk of water-related conflicts in 50 countries on five continents, according to the Global Policy Forum. Scientists tell us that the number of city dwellers facing water shortages will grow to almost one billion by 2050, from 150 million today, partly as a result of climate change.

And then there is sea level rise. One metre of sea level rise would submerge about a fifth of the territory of my home country, Bangladesh. The government last week declared that some 40 million people were threatened, risking climate migration on a biblical scale.

These examples show how the impacts of climate change are non-linear, a complex web of consequences and new consequences. It is myopic, therefore, for a country to think that the problem does not affect them, because they are not a victim directly. Climate change calls for a deeper understanding and a wider vision of leadership which understands the wider nature of the problem.

These are problems not just for leaders, but for all our civilisation.

Military leaders increasingly get it. In its latest global strategic outlook to 2045, Britain’s ministry of defence warned that some 60 million people would move from desertified areas of sub-Saharan Africa to northern Africa and Europe by 2020, a figure that it said would thereafter increase.

The military will see an evolving, humanitarian role, and must work with the wider security community to respond to climate impacts, and be prepared.

The GMACC has called on leaders for urgent action to implement the Paris agreement, to save the earth from catastrophic consequences.

Politicians are struggling to join the dots on climate change given these new, unchartered demands. All people, including experts, activists and individuals must therefore hold them to account, to ensure that they take the next step, to implementation, and the Paris agreement turns from process to success.