Climate Migration: What Do We Really Know?

By Klaas Lenaerts, a Research Analyst at Bruegel, and Simone Tagliapietra, a Senior fellow at Bruegel. Originally published at Bruegel.

How Can Climate Change Affect Migration?

Migration comes in many forms – temporary or permanent, local, rural-urban or international, forced or voluntary – and happens for many reasons – economic or political, or because people are fleeing from acute violence or natural disasters. The ways in which climate change could affect migration are therefore complex.

The academic literature distinguishes between impacts from fast-onset events like hurricanes, and slow-onset events like declining agricultural yields or desertification. The former usually have a direct impact resulting in forced, temporary and local displacement, whereas the latter more often have an indirect economic impact causing long-term, gradual and often voluntary migration. Rising sea levels, although a slow-onset event, can nevertheless directly result in forced and local migration, and threatens many densely populated areas worldwide. Moreover, over time the frequency of climate-related natural disasters is expected to increase, which raises questions about the impact of repeated fast-onset events.

Another layer of complexity is added by the fact that migration responses differ between individuals, for example because wealthier migrants can afford to move further, while poor farmers might not be able to move at all if their incomes decline due to climate change. Individuals from more developed countries may not even need to move, as their incomes do not depend heavily on agriculture or because they have the means to adapt to the effects of climate change.

What Do Empirical Studies Say?

The complex reality of migration (and the lack of adequate historical data to capture incipient climate change and consistent data on migration) is mirrored by the contrasting results of empirical studies and models that try to estimate past or future effects of climate change on migration. One 2016 study, for example, found that in middle-income countries rising long-term average temperatures increase migration from rural areas to cities, as well as migration to nearby countries. In poor countries, it found a negative effect for both internal and international migration, which is attributed to exacerbated income constraints on poor agricultural workers. Other studies find positive effects of weather anomalies on migration both within and from sub-Saharan Africa, suggesting that income constraints are not absolute. Another 2015 paper did not find any direct effect of long-term climate factors on international migration but suggested that natural disasters and rainfall shortages can have an indirect effect through income differentials.

What does this mean for migration to Europe?

Unsurprisingly, the answer is not entirely clear. In line with the idea of income constraints as well as restrictive migration policies, most of the literature suggests that migration from developing countries in response to climate change will grow but will be mostly internal or towards neighbouring countries. Current observations seem to support this. The 2016 study found that climate change only boosts international migration from middle-income countries to similar, nearby countries, which mostly excludes OECD countries as a destination. Similarly, the 2015 paper only reported some evidence for south-south migration, rather than migration to high-income countries. The IPCC therefore states that there is only low confidence about climate change contributing to migration to Europe.

However, the extent to which findings based on historical data will hold in the future is debatable. Many low- and middle-income countries have become more prosperous since the start of this century, which may have eased potential financial constraints on migration. Moreover, globalisation has already facilitated migration by creating migrant networks in OECD countries, which can support aspiring migrants both practically and financially.

Predictions of climate migrant numbers are often quoted to raise alarm, as migrants are expected to come primarily from the regions surrounding Europe: Africa, the Middle East and Central Asia. For example, a report by the International Organisation for Migration is sometimes quoted claiming that up to 1 billion people will be displaced by 2050. What it actually tells us is that no one really knows how many people will be on the move. 200 million is an accepted figure, but the range of estimates goes from 25 million to 1 billion by 2050. It also depends on which scenario materialises for climate action and global development.

The high estimate of 1 billion comes from a Christian Aid report, but this report in fact says that ‘only’ 250 million people will be displaced by climate change-related phenomena. The other refugees are displaced by (possibly related) conflicts and natural disasters (100 million) and development projects (645 million). While this is worrying from a humanitarian point of view, the implications for European migration policies may be less severe, as very few of those will leave their own countries.

Similarly, the Institute for Economics and Peace says that 1.2 billion people will be at risk of displacement due to climate change by 2050. However, the report does not say these migrants will all move to Europe or other developed regions, merely that this many people will be living in countries that lack sufficient climate resilience. Another recent report by the World Bank estimates that by 2050, between 125 and 216 million climate migrants could actually move internally in low- and middle-income countries depending on climate outcomes. It does not say how many migrants are expected to move internationally.

Estimates of future climate migration to Europe are rarer. Model estimates in one study put the total number of climate migrants over the twenty-first century between 200 and 300 million, 78% of which is internal, while the rest goes to OECD destinations. Importantly, conflicts triggered by climate change could force more than 50 million additional climate migrants to move during this century. In that case, most of these migrants are expected to move to Europe according to the model.

Finally, a study extrapolating historical data on temperatures and asylum applications estimated that by the end of the century the EU will receive around 100,000 additional asylum applications per year under the currently most likely climate scenario, an increase of 28% compared to 2017.

And Within Europe?

Interestingly, the literature on climate-related migration within Europe is scarce and inconclusive. It does not predict large effects, and any migration taking place would be mostly rural-urban. This does not exclude more significant changes in certain regions. Declining agricultural productivity is one of the most prominent factors in climate-induced migration. One might therefore argue that pressure to migrate might increase in rural areas in Europe’s southernmost regions (especially in EU candidate countries), which at least today depend much more on agricultural employment than the EU average and will also be most exposed to warming temperatures and droughts. Whether people will move to cities within the same country or to another EU country is likely to depend mostly on economic factors.

Figure 1: % share of total employment in agriculture, forestry and fishing by region (NUTS2), data for 2019. Source: Eurostat.

Figure 2: projected % change in annual precipitation by mid-century (2041-2070) by region (NUTS2), in a high-emission scenario (RCP 8.5). Source: Climate-ADAPT.


Overall, the literature on climate-induced migration suggests that people are moving already because of climate change and that increasing numbers will do so in the future, either voluntarily or not. Quantifying future migration is tricky due to complexity and data limitations, and outcomes depend on future climate scenarios and on the definition of a climate migrant. It is also not clear what the main driver will be (sea levels, income losses or instability etc), whether it will be poorer or more prosperous migrants that move, and how many will travel across borders, including to Europe. Most displaced persons may not travel far, but it does seem reasonable to expect a higher number of arrivals in Europe if climate change triggers instability and conflicts over resources in the surrounding regions. Within Europe, only the southernmost regions are likely to see emigration to nearby cities or to other EU countries, which may require a response at the EU level.

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About Lambert Strether

Readers, I have had a correspondent characterize my views as realistic cynical. Let me briefly explain them. I believe in universal programs that provide concrete material benefits, especially to the working class. Medicare for All is the prime example, but tuition-free college and a Post Office Bank also fall under this heading. So do a Jobs Guarantee and a Debt Jubilee. Clearly, neither liberal Democrats nor conservative Republicans can deliver on such programs, because the two are different flavors of neoliberalism (“Because markets”). I don’t much care about the “ism” that delivers the benefits, although whichever one does have to put common humanity first, as opposed to markets. Could be a second FDR saving capitalism, democratic socialism leashing and collaring it, or communism razing it. I don’t much care, as long as the benefits are delivered. To me, the key issue — and this is why Medicare for All is always first with me — is the tens of thousands of excess “deaths from despair,” as described by the Case-Deaton study, and other recent studies. That enormous body count makes Medicare for All, at the very least, a moral and strategic imperative. And that level of suffering and organic damage makes the concerns of identity politics — even the worthy fight to help the refugees Bush, Obama, and Clinton’s wars created — bright shiny objects by comparison. Hence my frustration with the news flow — currently in my view the swirling intersection of two, separate Shock Doctrine campaigns, one by the Administration, and the other by out-of-power liberals and their allies in the State and in the press — a news flow that constantly forces me to focus on matters that I regard as of secondary importance to the excess deaths. What kind of political economy is it that halts or even reverses the increases in life expectancy that civilized societies have achieved? I am also very hopeful that the continuing destruction of both party establishments will open the space for voices supporting programs similar to those I have listed; let’s call such voices “the left.” Volatility creates opportunity, especially if the Democrat establishment, which puts markets first and opposes all such programs, isn’t allowed to get back into the saddle. Eyes on the prize! I love the tactical level, and secretly love even the horse race, since I’ve been blogging about it daily for fourteen years, but everything I write has this perspective at the back of it.


  1. Ignacio

    The projected change in annual precipitation suggests the models used to obtain it are is too simplistic as a N/S thing as if with climate change this would be the only changing pattern. It probably relies too heavily on the cessation or reduction of ocean streams but I believe that local phenomena, unpredictable atmospheric phenomena, and equally unpredictable changes in ocean currents make the model basically useless in practical terms though interesting as a starting point for discussions on climate change.

    The model presciently put the limits of Europe in Moldova, Ukraine and Bielorussia…

    1. PlutoniumKun

      Yes, this is always the issue with modelling and local area predictions. Every modeller I’ve talked to has emphasised that they are only accurate at global and regional levels. Once you get down to a more local or national scale, you are really just making educated guesses. There are far too many variables once you get down to the granular level of individual agricultural regions, river basins, mountain valleys, etc.

      Its quite a dangerous thing. I’ve talked to engineers who regularly make statements like ‘we’ve built in assumptions of X mm additional rainfall and flooding events over 50 years into our design’ as if that was climate change just dealt with. When I’ve pointed out that there is no basis for this level of certainty on a river basin scale, I’ve just got confused (or hostile) looks in response. The greatest danger of climate change is the enormous level of uncertainty at the only scale that matters – human scale.

      1. Synoia

        Modelling a Chaotic system (Climate) is rife to providing studies slanted to what the Boss want to get.

        And to steering the money spent on avoiding lack of rain to favoured suppliers, or thieving crackpots in our billionaire class.

      2. Lexx

        “Go, go, go, said the bird: human kind
        Cannot bear very much reality.
        Time past and time future
        What might have been and what has been
        Point to one end, which is always present.”

        Even engineers have their orthodoxy.

        1. Michael C.

          Not sure Eliot would agree, but that end increasingly looks a lot like the end of humanity.

          1. Irrational

            Agree with all of you on simplicity and think Europe is about to make itself very unattractive economically speaking – ref. all the NC posts on Ukraine.
            A minor quibble: the chart shows change of precipitation from baseline, but e.g. BE-Lux is already in limited drought condition, so not much of a consolation that precip stays around the same.

  2. Steve H.

    Caught up with my friend Phil recently, we spoke of our friend Louis, who is hard to find in the first place. He and Denita were living in N Cali until the wildfires hit, so they moved to Portland. We kinda had a handle on where he was there, but then the wildfires hit and they moved back to New Mexico, and even Louis’ brother didn’t have contact info. In now, in New Mexico, the wildfires hit…

    If I were feeling salty, I might suggest that the studies being paid for involve brown people moving to areas experiencing demographic labor shortages.

  3. Alyosha

    I’m far from an expert, but from even a brief overview of paleo-climatology it’s hard to confidently expect gradual and predictable changes. Sea levels rising by X meters over 100 years with the assumption that it’s X/100 can make the problem appear tractable. But what if even 30% of X meters happens in a decade rather than three? The same for rainfall predictions, especially in the Mediterranean basin. A long, slow decrease is problematic. 3-4 years of extreme drought is catastrophic. Or even instability related to concentrated rainfall alternating with drought.

    Over the last ~6 years, Lake Superior has gone from roughly the lowest levels in recorded history to some of the highest. The rise was much faster than the fall. My city had to move Lakeshore Ave inland because stretches of it simply had to be closed all winter. In the past a big storm might temporarily close those areas, but when the lake started regularly chucking boulders across the road and the wave wash was constantly flooding/freezing it, the city just gave up.

  4. jefemt

    Thank you for this. Important and informative. Those climate predictive models are interesting.

    I would love to see an analogous articles vis a vis African continent, and asia/ pacific.
    Of course, N/C/S America– Congress is On It!

    This circles back to the UN report featured here the other day,and has echoes of the obvious embarrassing lack of collective rigor on Covid- data, science, and a truly inclusive, global rational response and plan for future action.

    It also helps me circle back to a myriad of sources projecting and pointing to our glum future.
    No wonder folks eschew me and espit me out.

  5. McWatt

    Had my first climate migrant visit my store a few weeks ago. She said both grandparents, parents and children of her family left the bay area to move to the midwest because of climate. Startling!!

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