* Any views expressed in this opinion piece are those of the author and not of Thomson Reuters Foundation.The more we know about climate-linked migration, the harder it seems to act
The days when newspapers ran headlines about the hundreds of millions of climate change refugees who'd be knocking on the doors of rich countries in the coming decades are long gone. Experts in environmental migration are not exactly mourning the loss.
In the past few years, as researchers have deepened their understanding of how climatic stresses are pushing people to move, they have stopped making predictions about the numbers and started talking about the complexity of the phenomenon.
Recently we ran a story about how impoverished villagers on the mud flats of Pakistan's south coast are being forced to move inland a few kilometres due to a combination of sea-level rise, storm surges, flooding and land erosion - a far cry from the early spectre of mass migration across borders.
But this is the reality of the incremental changes occurring in many places, particularly across vulnerable regions of Asia and Africa, as environments become less hospitable and people consider their options as it gets harder to make ends meet.
Then there are those temporarily forced from their homes by the impacts of extreme weather, such as the floods in southern Africa this month or Typhoon Haiyan in the Philippines in 2013.
According to human rights lawyer Walter Kälin, in the past six years some 160 million people have been displaced by sudden-onset disasters, 90 percent of them linked to weather events. But were they caused by climate change?
"No one can really say to what extent displacement disasters are climate-related compared with weather-related," cautioned Kälin, an envoy for the Nansen Initiative, which is helping states figure out how to protect those displaced across borders by natural disasters.
Even when it comes to people who move because of droughts or encroaching seas, "you still shouldn't forget about the human factor", Kälin told an online seminar on the issue of climate change and displacement this week.
"You have to look at all the causes, and not jump to the conclusion that climate change increases displacement," he added.
That's not to say that experts don't think it will. The problem is they're still unsure about how it will happen, and what to do about it, given that poverty, conflict, ill-health and other stresses are often part of the puzzle.
Nonetheless, efforts are underway to put together the jigsaw and find solutions.
The Nansen Initiative, for example, has been consulting governments on a regional basis, and plans to convene a global conference in October where states may adopt guidelines to protect people displaced internationally by disasters.
But, as University of Oxford professor Roger Zetter pointed out, "many would now throw up their hands in horror" at proposals made a few years ago for a new global convention on climate change refugees - which he described as "extremely problematic".
And Foreign Policy magazine documents the so-far unsuccessful attempts by a Kiribati man and his lawyer to win him legal recognition as a climate change refugee in New Zealand.
So, with little prospect of national or international law coming to the rescue of those afflicted, what hope for help?
Humanitarian officials speaking at the seminar talked about the need for urgent assistance. "People want answers now," said José Riera, an international protection specialist with the U.N. refugee agency (UNHCR).
But the emergency aid system is already overburdened, and will not be able to meet the likely need for "billions and billions" of dollars to deal with the problem of climate-related displacement over time, he emphasised.
Strong arguments are being made for at least some of that money to come from the slowly growing global climate finance pot.
They run like this: Much climate-related displacement so far is happening inside poor countries, but their governments just don't have the resources to deal with the problem. And the historical responsibility lies with industrialised parts of the world most blamed for climate change.
That in effect turns what might have been considered an apolitical humanitarian response to worsening drought in the Sahel region of West Africa, for example, into "a challenge of restorative justice to polluting countries", Zetter noted.
That could open the door to objections from donor governments wary of being made to provide compensation - and to tussles over the thorny questions about cause and effect which remain tricky to answer.
"It is a huge, political global challenge," warned Zetter.
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