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FactCheck Q&A: as the climate changes, are 750 million refugees predicted to move away from flooding?

How does Peter Singer’s figure of 750 million fit within the range of estimates on ‘climate change refugees’? Q&A

The Conversation is fact-checking claims made on Q&A, broadcast Mondays on the ABC at 9.35pm. Thank you to everyone who sent us quotes for checking via Twitter using hashtags #FactCheck and #QandA, on Facebook or by email.

Excerpt from Q&A, August 2, 2016, watch from 1.12.

PETER SINGER: That is going to basically inundate every coastal city around the world, including, of course, all Australian major cities are coastal. It is going - estimated to cause something like 750 million refugees just moving away from that flooding. Never mind those who also because refugees because (indistinct)…

VIRGINIA TRIOLI: Some of those claims are contested, of course?

PETER SINGER: Well, they are contested but do you want to take the chance, right? – Peter Singer, Ira W. DeCamp Professor of Bioethics, Princeton University, speaking on Q&A with host Virginia Trioli, August 2, 2016.

Ethicist Peter Singer told Q&A that climate change-related sea level rises are “estimated to cause something like 750 million refugees just moving away from that flooding”.

It is beyond the scope of a FactCheck to say with any certainty what will happen in the future. And there is no single official data source on the numbers of people who migrate because of the impacts of climate change, partly because there is no legal definition of a “climate change refugee”. Furthermore, most such displacement occurs within countries, not across international borders, and is always due to a number of different factors. Finally, there is no systematic monitoring of such movement.

That said, we can check how Singer’s figure of 750 million fits within the range of estimates that exist on this question.

Checking the source

When asked by The Conversation for sources to support his statement, Peter Singer said:

Factchecking always welcome! My source for the figure is Climate Central and in terms of the possible extent of sea level rises, please see this paper by Hansen et al.

The figure I gave is near the top end of the Climate Central range, but remember that I agreed with Virginia Trioli that this is contested. I argued that if it is even a small chance, the stakes are too high to be worth taking the risk.

Climate Central is a group of scientists and journalists researching and reporting climate change and its effects. In 2015, the group said that:

Carbon emissions causing 4°C of warming — what business-as-usual points toward today — could lock in enough sea level rise to submerge land currently home to 470 to 760 million people, with unstoppable rise unfolding over centuries.

Predictions vary and uncertainties abound, but climate scientists say it is possible we may reach 4°C of warming by 2100 if insufficient effort is made to reign in emissions.

As Singer acknowledges, his figure of 750 million is at the upper end of estimates – and he readily agreed that estimates are contested.

Without detracting from Singer’s broader point about the human consequences of climate change, it is worth taking a closer look at the context, assumptions and methodologies behind some of these alarming-sounding figures.

What does Singer’s source say about climate refugees?

When Climate Central released its Mapping Choices report in 2015, the headline it used on its website was “New Report and Maps: Rising Seas Threaten Land Home to Half a Billion”.

But to be clear, Climate Central’s full report did not say that 750 million people would need to move away due to rising sea levels – in fact, unlike Singer, it didn’t use the term “refugees” at all.

Instead, it said only that under a 4°C warming scenario, there could be “enough sea level rise to submerge land currently home to 470 to 760 million people” (emphasis added).

Many people would indeed move in that scenario – but past experience from around the world means we can be confident that many would also stay and try to live with a changed environment.

The Climate Central report acknowledges that its estimates do not take adaptation strategies into account, noting:

Results do not account for present or future shoreline defences, such as levees, that might be built, nor for future population growth, decline or relocation.

A vast range of estimates – and plenty of guesswork

Some of the numerical estimates on climate-related displacement are based on crude methodologies, as explained in my 2012 book, Climate Change, Forced Migration, and International Law.

For example, in 1993 social scientist Norman Myers wrote a paper suggesting that 150 million people could be displaced by climate change by the the mid-21st century. He had identified areas expected to be affected by sea-level rise, and then calculated the anticipated population of those areas in 2050. In subsequent work and interviews, he said the figure could be closer to 200 million or 250 million. Estimates ranging from 50 million to 600 million to even a billion have been cited by some.

The Observer published an article in 2010 headlined “Climate change will cost a billion people their homes, says report”.

However, that report misconstrued a paper by Dr François Gemenne – whose work is empirically based and well-reasoned – that referred to the Intergovernmental Panel on Climate Change’s (IPCC) comment that freshwater availability in a changing climate may adversely affect more than a billion people by the 2050s. That’s a different story from the one told in The Observer’s headline.

Many of these upper end estimates – and the methodologies used to calculate them – have been criticised by other researchers, who note that very big estimates often fail to account for adaptation.

The IPCC itself has said that:

Estimates of the number of people who may become environmental migrants are, at best, guesswork.

How much weather-related displacement of people have we seen so far?

Peter Singer’s comment was about future impacts of climate change. But what do we know about current and past climate-related movement?

The best statistics on this are published by the Internal Displacement Monitoring Centre (IDMC), the leading source of information on internal displacement whose role has been endorsed by the UN. It said in its Global Estimates 2015: People displaced by disasters report that:

Since 2008, an average of 22.5 million people have been displaced by climate- or weather-related disasters [each year].

Internal Displacement Monitoring Centre (IDMC)

These figures were also recognised in the Nansen Initiative’s Agenda for the Protection of Cross-Border Displaced Persons in the context of Disasters and Climate Change, endorsed by 109 States (including Australia) in late 2015, and by the UN Secretary-General’s report on refugees and migrants prepared for a high-level summit on large movements of refugees and migrants to be held in New York in September 2016.


Are rising seas “estimated to cause something like 750 million refugees” to have to move, as Peter Singer said? Not according to the source he provided, which actually found that sea level rises under a 4°C warming scenario could submerge land currently home to 470 to 760 million people; the report didn’t say that all or most would subsequently become refugees.

As Singer acknowledged, his figure of 750 million people being affected by climate change-related flooding in future is at the upper end of estimates – and is contested. The methodologies and assumptions underpinning some of the upper end estimates have been critiqued by scholars, as they often do not adequately account for adaptation. – Jane McAdam


In general, I and others in the migration field would strongly agree with the author’s sound critique of Singer’s assertion.

Human mobility in the context of climate change is complex. Limits to a more nuanced understanding of this issue may be due to a lack of agreement on the legal definitions and the methodological choices made to project numbers of environmental migrants, as well as - importantly - an understatement of the agency and adaptive capacities of people.

Communities in coastal and low-lying areas that may be affected by sea-level rise in the future are affected today by recurrent natural hazards, coastal erosion, land subsidence, and saltwater contamination of arable land.

Empirical studies, including from the United Nations University, have explored how migration contributes to livelihoods and household adaptation strategies.

Experts tend to agree that the types of movements that might fall under that moniker “climate migrant” are varied and complex. Robust estimates by the Internal Displacement Monitoring Centre fall short of accounting for people living in prolonged displacement, displaced across borders (generally agreed to be a minority), or migrating away from their homes due to the long-term effects of climate change (erratic weather, droughts, and the gradual loss of land). The last grouping may be the largest – and would be considered labour migration under current definitions.

The author’s section on weather-related displacement rightly adds an important dimension to a focus on sea-level rise, which is by no means the only cause of movement. An additional important point: climate change experts have largely been reluctant to attribute any individual weather event to climate change, thus making it difficult to attribute displacement due to climate- or weather-related disasters to climate change. – Julia Blocher

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