At least we are talking about climate change again.

The president of the World Bank, Jim Yong Kim, said in a speech on April 2 that: “Climate change is not just an environmental challenge. It is a fundamental threat to economic development and the fight against poverty.”

In January, the IMF suggested that one way to deal with the problem of the carbon emissions that are exacerbating climate change might be to end the $1.9 trillion in direct and indirect fossil fuel subsidies that keep hydrocarbons artificially competitive.

The UN’s Human Development Report, the annual temperature gauge for the world’s ills, discussed its impact on sustainable poverty reduction. The UN Development Programme’s director general, Helen Clark, talked about it in a speech in Costa Rica this March.

“Some may still deny the overwhelming judgment of science, but none can avoid the devastating impact of raging fires, and crippling drought, and more powerful storms,” President Obama said, out in the winter sunshine for his inaugural address in January 2013. Two hundred miles away, New York was still picking through the debris from Hurricane Sandy, the words of its mayor, Michael Bloomberg — “Our climate is changing” — still ringing across the political waters.

And of course, we are still talking about the science — as Northern Europe is gripped in an unfeasibly long winter, the link between shrinking arctic ice and the shifting of the Jet Stream becomes an interesting new area of study.

In the developing world, climate change is not an abstract.

Having been bombarded for thirty years by charity-supplied images of fly-bitten deserts, people flying for the first time into sub-Saharan Africa are often surprised by the vast swathes of green that roll by beneath them. The reasons for persistent food insecurity in parts of the continent over the past half century are many — sometimes structural, sometimes political, but rarely have they been purely climatic.

The continent, viewed conveniently, if inaccurately as a whole, is also booming in economic terms. The aggregate gross domestic product of Africa has grown, uninterrupted, year-on-year for a decade. Such numbers always mask inequalities at the ground level, but many countries and communities have been moving ever upwards, out of poverty. Now though, even in the islands of relative prosperity, that progress is threatened by shifts in weather and climate.

Talk to those on the frontline and they are in little doubt.

In his station at the base of Mount Kenya, the cloud-wrapped pivot around which the country's agricultural heartland revolves, the acting head warden of the national park, a vital, energetic man called Simon Gitau, baldly states that climate change is his daily reality.

“I don’t want to see the Al Gore movie [An Inconvenient Truth]. I have seen it happen here,” he told me late last year.

Yes, the action of populations directly abutting the great montane forest has chipped away at the ecosystem, poaching has undermined its biodiversity and the excision of trees for farmland and settlement has damaged, perhaps terminally, the water table. But beneath all of those harmonics is the underlying bass note of macro-level climate change.

When he was a child, Gitau’s home, 2,000 metres above sea level in the foothills of the Aberdare mountains, routinely saw sub-zero temperatures at night. Today that rarely, if ever, happens. The glaciers on the peaks of the mountains are receding apace. The irreplaceable old-growth forests are dry and vulnerable to wildfires. If those go, the water that they fix on the mountainside, which runs down to irrigate the country, could evaporate, dooming Kenya's breadbasket to creeping degradation and desertification. Gitau shudders visibly when he contemplates the threat of fire.

Further to the west, where tea fields flicker yellow and gold, temperature variations and shifting rain patterns — some years the short rains come late, some years they come early, some years they barely come at all — have made livelihoods unpredictable. Only the khat growers, who rattle down the highway at 90km an hour in high-powered 4x4s to get their goods to Mombasa or on a plane to Mogadishu, seem to have any certainty about their economic future.

To the north, in the semi-desert regions that span over the borders into Uganda, Kenya, South Sudan and Ethiopia, pastoralists have always played chess with their environment, shifting their herds massive distances in a rolling search for pasture. In the Kenyan county of Turkana, wealth is based on livestock, and there are those who would be dollar millionaires were they ever able or willing to convert their beasts to cash. But the landscape, always dry and scaled, is more so, what rivers there are reduced year-on-year to thick ooze, except when the parched earth gives a conduit to flash floods from the highlands over the border.

When droughts come, animals die — that has always been the case. But drought used to be a twenty-year problem and now it is a biannual or triennial event. What resilience these politically and socially marginalised communities used to have has been eroded to breaking point.

In Turkana today, nine out of ten people live below the international poverty line of $1.25 per day; more than 250,000 survive on food aid.

This is a theme repeated across the entire continent. People more connected with the land, outside of the atmospheric controls of western cities, talk convincingly of how things used to be. In Koulouck, Senegal, where the sand has crept from the Sahel to engulf whole regions that once produced fruit trees and senna for telegraph poles, groundwater has dried up, once thriving communities look to the government and charities for food aid and the positive cycle of poverty reduction is broken, driving independent people to aid dependence. This degradation is in part because of the removal of tree barriers, but partly because rains that used to come, don't, and temperatures have ticked upwards.

In Zambia, international experts warn that the giant rivers of Southern Africa that pump dams to power cities and feed commercial farms will run dry. The infrastructure built at huge cost will cease to function. In Namibia, the discovery of a huge aquifer beneath the desert has prompted arguments over its management that remind the country of its impending water shortages.

In South Sudan, where the wide Nile cuts through the capital, a sole calm and timeless presence in that frenetic new city, the wet season turns the centre of the country to an impassable, liquefied mess. But for all of the hope brought by the end of the Sudanese civil war and independence, the fear is rising that conflicts once fought over oil will next be fought over water.

Cities, too, face new threats. Water from the mountains feeds the rivers that feed the cities. The urban poor are among the most vulnerable to the wider impacts of climate change. As a March study from the International Institute for Environment and Development points out, low income groups in developing world cities are net buyers of food, unlike their rural counterparts who, while under climate pressure, may have subsistence farming to survive on. As food becomes scarce and expensive, it is those now crowding into the booming cities of Africa and Asia who will face starvation and malnutrition.

No, we do not entirely understand the local, regional and global dynamics of climate change. No, we can rarely, if ever, attribute individual weather events to climate change because, well, that isn’t how statistics works. Because the driving force of science is doubt, fighting the dogma of 'skeptics' — that word implies rational, rather than purely emotional or commercial objections to the science, and could be considered misleading — is nearly impossible. But while the debate rages on in high places, on the ground the truth is plain to see.

Climate change is not theory or a policy area to debate, nor is it just about absolutes measured in degrees Celsius, it is a grim dynamic equation of uncertainty and risk that is playing out right now.

It is people already on the frontiers — socially, economically or geographically — who are least able to absorb the risks or the impacts. People striving to escape the poverty and inequality of their circumstances are thrown back into insecurity and dependence. Populations move, and in the friction of their exodus drive conflicts.

Livelihoods collapse, people die, vital ecosystems are lost forever and, cynically, money is wasted. The decades of progress made by aid and development assistance — flawed though it may have been — are being undone. Those with cash may need to constantly subsidise those on the fringes just to keep them clinging to the edge of the abyss.

Still. At least we’re talking about it again.