Which of the following statistics have you heard before?

1. 250 million climate refugees by 2015?
2. 1 billion climate refugees?
3. 50 million climate refugees by 2010?

There are a lot of different estimates floating around. One of the most common questions we get asked is: which of these answers is correct?

The bad news is that none of these estimates are right. But possibly not for the reasons you might expect. To estimate the number of climate refugees – now or in the future – we need to start by defining exactly what a climate refugee is. We would need a definition of who counts as a climate refugee and who doesn’t. Without a definition it isn’t possible to say how many climate refugees there are – or will be.

• Related: how to define climate refugees

Defining climate refugees

There are several reasons why defining “climate refugees” is difficult. Climate change will certainly have an influence on patterns of migration and displacement. But climate change usually combines with other forces – like job opportunities or conflicts – to lead to someone moving. Disasters like drought, floods and hurricanes have always forced people move. As climate change makes these disasters worse, more people may move. But it’s difficult to say that any particular disaster only happened because of climate change.

So we’re in a tricky position. Climate change does play a role in changing patterns of disasters. And those disasters do cause people to move. But lots of other factors are involved too. This means that picking out one group of people to call “climate refugees” is very difficult.

How many climate refugees are there now?

And that is why it is so hard to say how many climate refugees there are right now.

Consider this example:

Climate change could have an impact on drought and then on farming. This may mean that people move as the income from their farming declines and they need to find other work.

Are they climate refugees? It could well be that if they had access to other non-farming work nearby that they wouldn’t move. So is it climate change that has caused them to move? Or is it the fact that their local economy lacks alternative employment?

Of course we can say that climate change was among the forces that made them move. But is this enough to count this person as a climate refugee? If climate change plays a role in displacement it becomes difficult to draw the line. Because it is so hard to say who is – and who isn’t a climate refugee – it becomes very difficult to say how many there are.

But that doesn’t mean we don’t need to worry. Climate change is going to make disasters worse. And those disasters will result in displacement and migration. But that doesn’t mean there is a easily countable group of people who are climate refugees. We wish it was simpler than this, but unfortunately it isn’t.

How many climate refugees will there be in the future?

Most of the numbers you may have heard about climate refugees are usually predictions. They are estimates of how many climate refugees there will be in the future, rather than how many there are now.

This makes things even more complicated. These estimates are usually made by looking at predictions of sea level rise, then looking at how many people currently live in the areas that will be underwater if the seas do rise to the predicted levels.

This sounds fairly sensible. But it is (again, unfortunately) not so simple. Sea level rise happens fairly slowly and people will move away from impacted areas gradually.

Here is another example:

Suppose someone in Bangladesh moved away from their current home and farm because of sea level rise in (let’s say) 2035. For a lot of the time their land is fine, but sea level rise means that typhoon strikes are flooding their land with salt water more frequently. After several years the farm becomes less profitable so they move to a nearby town and find a different job. Are they a climate refugee?

If they are still alive in 2050 should they be counted as one of the climate refugees that may exist by that date. It isn’t completely clear. They have certainly moved – but whether they count as a refugee is more debatable.

They haven’t crossed and international border – which is part of the official definition of what makes someone a refugee. Further, their circumstances are not ‘refugee-like’. Their circumstances don’t fit with what most people imagine a refugee’s situation is. For example they could living in their own country, living in a decent home and working a good job. Categorizing them as a “climate refugee” doesn’t seem quite right.

It is more accurate to see these future predictions as the being about the number of people who will be affected by sea level rise, rather than predictions about the number of climate refugees.

Can we say anything at all?

You probably came to this page hoping for a definitive answer. The issue of climate-linked migration is complicated, and it’s a field where the answers are often not simple.

However there are some figures and statistics that we think are useful and accurate. The statistics produced by the Internal Displacement Monitoring Centre are very useful. They aren’t statistics on the number of ‘climate refugees’. But they do produce estimates of the number of people displaced by disasters, and even for the number of people displaced by certain kinds of disasters. It’s important to remember that these are etimates of current and past displacement – not predictions about the future. But we can use these estimates to encourage people to consider what he future impacts of climate change on dispacement could be. 

Using these figures we can make statements like:

“24 million people were displaced by weather related disasters this year. As climate change begins to alter patterns of disasters, we can imagine these figures will get worse.”

Sure, it’s not quite as catchy. But it is accurate.