Ten years ago, I ended up on the mud flats of the Nile delta with a water engineer. He explained how everything we could see around us would be under water if sea levels rose as they are predicted to do - the nearby city of Alexandria is one of the most vulnerable to climate change in the world. It was just before a major conference on climate change, and the aim had been to find stories - and images - of global warming that got beyond the cliche of a melting ice cap. But as a journalist it was hard to bring this future to life; this sleepy bit of coastline hardly evoked the sense of urgency required to mobilise the international attention needed.
This is the central paradox of climate change politics, argued the sociologist, Anthony Giddens, that electorates can't grasp the significance of climate change because it is too abstract, and not dramatic enough (they need catastrophe footage), and won't - until it's too late. By the time we are experiencing massive floods, freak weather, sea-level rises and higher temperatures, we will be well past the point of doing anything about it. He christened it Giddens paradox.
Ten years on, the impact of climate change is frighteningly more concrete. In the remote town of Anakila in Mali, west Africa, I find what we were looking for in the Nile delta 10 years ago. Campaigners know the power of images to drive the message home, and that's why the aid agency Tearfund took me on a 1,000km journey from the capital, Bamako.
Three hours after we left the paved road, we arrived at low mud houses clustered under large mango trees. This is part of the Sahel, and the nine months of the dry season have always left a narrow ecological perch for the community and its subsistence agriculture. They are poor, yet the town is vibrant; the Dogon people are much admired in Mali for their resourcefulness and hard work. Circling the town are the small vegetable gardens on which they depend.
For years now, the elders explain, they have been worried by climate change. Disrupted rain patterns, shifts in winds have no parallel in collective memory; they notice how it is prompting changes in the behaviour of animals and birds. But all of these anxieties are dwarfed by the sand dune now looming above their town - the result of those drier, fierce winds and erratic, intense rainfall.
The dune stands several hundred feet high, spilling into the river and stemming its flow, slowly burying trees whose trunks are now deep in soft white sand. Plenty of fields have been swallowed by the sand already. The villagers' defences against further encroachment are hedges of euphorbia - they surround the rows of sorghum that stand pitifully in ground which is more sand than soil.
The dune glows golden in the sun, a dramatic and unfamiliar eruption in the landscape. This area was once forest, but gradual deforestation has thinned the tree cover and exposed the sandy soils. The dune is moving inexorably towards the outskirts of Anakila. It's a sinister sign of the vulnerability of the Sahel, the grasslands that border the Sahara in a swath across Africa, and where millions have farmed and herded cattle for centuries. The ecological niche in which they have built their lives has always been full of uncertainties - and often hardship - but now the niche on which they have built cultures of great sophistication and resilience is shrinking beneath them as desert threatens.
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This is another paradox of climate-change politics: it is in remote places like this that climate change will hit first and hardest. It is cultures built on deep understanding of their environment - whether the Sami of the Arctic or the Dogon of the Sahara - whose way of life is the first to be threatened. Anakila's residents are the canaries down the mine, their experience a foretaste of an Earth hostile to human inhabitation. But their experience of threat, potential devastation and loss of livelihood is discounted and ignored. No dunes are threatening Manchester.
But Anakila's plight will come back to haunt us in two ways. The entire debate around Africa and aid will shift in coming years from one dominated by charity and post-imperial responsibility to one framed primarily around environmental justice. The continent is one of the most vulnerable, with many of its delicate ecosystems threatened, as Camilla Toulmin's charts in her book, Climate Change in Africa. It is also the least well equipped to respond - and the least responsible for the coming calamities.
Media attention on the climate change talks in Cancún at the end of this month will focus on the negotiations over emission cuts, but equally important is the financing of climate adaptation - at Copenhagen $100bn a year by 2020 was pledged. Detailed proposals are due to be published this week on new forms of climate financing to start bringing this into effect. But the danger is that funding for climate adaptation will be poached from aid budgets. Already the development secretary, Andrew Mitchell, has made it clear that the pledge for foreign aid of 0.7% of GDP inherited from Labour will be used to finance climate adaptation. Ensuring this money reaches communities as marginalised and as poor as Anakila is a huge challenge.
The second way in which Anakila affects us is even more direct. In the faces crowded around me, I realised that there was a missing generation. This was a community of the elderly and the very young, with only a few young women - and virtually no young or middle-aged men. If you have ever wondered in Paris, Barcelona or Rome where the men come from who are trying to sell armfuls of jewellery that no one seems to want, then perhaps places like Anakila might be the answer. We met one man who had got as far as Manchester twice - both times turned back.
Migration puts an added burden on the village. Without their labour, it is even harder to sustain and provide for the community; migration accelerates the disintegration of their way of life. The most ambitious and resourceful attempt the dangerous journey to Europe. Many others swell the sprawling growth of Bamako, one of Africa's fastest-growing cities.
As we left Anakila, we were given gifts - fresh milk and two hens. When might this generosity become a demand for environmental justice? When might such visits prompt anger and recriminations instead of smiles and greetings? Mali is a country of crushing poverty, and the predicted outcomes of climate change could spell catastrophe for much of the country. Back in Bamako, a government spokesperson wanted compensation put on the agenda in Cancún. It's only a matter of time before the demand for compensation becomes the rallying cry for a new generation of activists - not just in Africa, but across the globe.