28 reports in this theme, newest first.
By 2087, most of humanity will live in sub-Saharan Africa or South Asia. By the 2090s, the median person would live at a mean annual temperature of 26–28 °C, up from 22 °C, and the worst-off quarter beyond 28.5–29.4 °C, with one to more than two months of dangerous heat a year, in air already six times dirtier than the WHO guideline. A low-emissions, high-development path keeps unprecedented heat to 0.6 billion people instead of 3.8 billion.
Droughts have barely become more frequent, but they have become hot. Half of warm-season drought months in 1995–2024 were also extremely hot, up from three in ten in 1951–80 and seven in ten in 2021–24. Dry-to-wet whiplash is up 30%, and hot-dry years produce the great smoke and dust events. By the 2090s, 0.34 billion people would live with two or more compound hazards on a low-emissions path, 5.2 billion on a high one.
About 11.6 million people a year die in six channels that polycrisis prevention targets. Matching the best quarter of income peers would protect 4.6 million of them and reaching the next income tier 7.0 million, but doing both would protect 8.6 million. The burdens cluster in the same 55 countries and share drivers such as health coverage and sanitation, and closing the gaps by 2040 would protect about 172 million lives by 2050.
In 2022 the median fuel importer's bill jumped from 4.5% to 7.4% of GDP, and the jump tracked how much each country imported, not how clean its power was (r = −0.08). Import bills are mostly oil and gas for transport, heat and industry, so the transition protects only when it reaches those uses. When it does, it also cuts the 86% of fossil air-pollution deaths borne by importers and the emissions behind climate risk.
Burning coal, oil, gas and biofuels caused 48% of the 3.8 million deaths from outdoor fine particles in 2017, the same combustion that drives climate change. Each million tonnes of fossil CO₂ carries about 105 deaths a year in lower-middle-income countries and 9 in rich ones, so poorer countries, which emit 11% of fossil CO₂, bear 34% of fossil-fuel air-pollution deaths. Cleaning the air must be paired with methane cuts: alone it adds 0.26°C by 2050, but with methane cuts only 0.02°C.
Each 0.1 rise in the Human Development Index goes with about 63% fewer people hit by climate disasters, 62% fewer near-poor and 25% less death from communicable disease. Within countries over time, the share affected by climate disasters falls 40% per 0.1. Yet human development gains in 2019–2023 were half those of the 2000s, the gap between low- and very-high-HDI countries has stopped closing, and development has not damped growth volatility or pandemic mortality. Those tail risks need their own institutions.
Forty-eight countries, 36 of them in sub-Saharan Africa, are trapped in two or more degradation cycles, and they hold 78% of the world's extremely poor. Polluting cooking fuel, missing sanitation and forest loss move together even among countries at the same income. Fifty-two countries escaped at least one cycle after 2000, through clean-cooking drives, sanitation campaigns and forest recovery, and cut extreme poverty by a median 26 points, more than twice as much as those that stayed trapped. Air pollution is the cycle growth has not broken.
In low- and middle-income countries, 69% of people now cook mainly with gas or electricity, up from 27% in 1990, but 2.03 billion still rely on wood, charcoal, coal or kerosene. In sub-Saharan Africa the number using polluting fuels has risen by about 340 million since 2000, and charcoal users have more than tripled. At least 1.37 billion people without clean cooking already have electricity, which makes efficient electric cooking a second lane alongside LPG. Even so, the 2015–2023 pace would leave about 1.6 billion people without clean cooking in 2030.
Half the world's school-age children — 962 million in 35 countries — live where most 10-year-olds cannot read a simple text and climate hazard is high. Children's exposure to dangerous heat doubles by mid-century, with sub-Saharan Africa's share tripling to a quarter, yet only one in five primary schools in low-income countries has electricity to run a fan. Because schooling is among the strongest predictors of how well people cope with disasters, every lost school day today weakens tomorrow's resilience.
The water polycrisis has two faces. In 35 countries with 4.1 billion people, from Egypt to India and China, water is physically scarce: withdrawals exceed 40% of supply, agriculture takes three-quarters and aquifers are falling. In 47 countries with 1.6 billion people, mostly in Africa, water is plentiful but nearly a third of people lack basic water, unsafe water kills at six times the rate of well-served countries and grids hang on hydropower. They meet in Sudan, Afghanistan and Yemen — and each needs a different fix.
In 35 countries with 1.45 billion people, from Nigeria to Bangladesh, fine-particle pollution is stuck high or still rising while income stays below $10,000 a head — and growth has not cleaned the air of the poorest third of countries at all. The loop runs both ways: poverty means smoky fuels and weak regulation, and pollution costs 3.7 years of life expectancy in lower-middle-income countries and erodes human capital. China turned the corner at $14,000 a head and India at about $7,000 — proof that clean air can come early, as growth policy rather than its reward.
Thirty-six countries with 3.0 billion people combine high climate hazard, high pollution exposure and weak coping capacity — across the Sahel, West and Central Africa and South Asia. The opportunity is concentrated too: the 60 countries breathing 25 µg/m³ or more emit 74% of the world's coal CO₂ and half its greenhouse gases, so in a handful of airsheds the same coal and methane cuts that slow warming would clean the air for billions.
Pollution and people concentrate in the same places: the average person breathes air 1.53 times dirtier than the average inhabited square kilometre. But most of a city's pollution is not its own — in the median city the background 165 km away is 79% as polluted as the centre, and the wind carries city smoke downwind. Exposure is most unequal by income: 41.7 µg/m³ for lower-middle-income countries, 3.2 times the high-income level — so clean air needs regional, not just urban, action.
Disasters kill far fewer people than they did — 6 per million a year in the 2010s against 99 in the 1960s — because capacity rose faster than threat. Within countries, each extra year of adult schooling has cut deaths per 1,000 people affected by about a third. Projected to 2100, that capacity keeps winning in most futures, but not in a fragmented, high-warming SSP3 world, where population and hazard outpace schooling and expected deaths rise in two-thirds of countries.
Where coping capacity is strong, recorded deaths from floods, storms, droughts, landslides and wildfires stay near 0.6 per million people a year whether hazard is low or high. Where it is weak they rise to 8.7 per million in the most exposed third — a 14-fold gap. About 14,000 recorded deaths a year are avoidable at that benchmark, and the true toll is larger because heat deaths are counted almost only in rich countries.
Very hot days are deadlier when the air is dirty: across 620 cities, a very hot day raised deaths by 12.8% when particle pollution was high against 5.3% when it was low. And the two hazards travel together — in 2024 ozone was higher on hot days in 131 of 149 large cities. About 2.6 billion people live in countries that are both hot and polluted, three-quarters of the population of lower-middle-income countries against 4% in high-income ones.
The poorest half of humanity breathes 66% of the world's fine-particle exposure above the WHO guideline. Exposure peaks not in the poorest countries but in lower-middle-income ones, where industry, dense cities and solid-fuel cooking coincide: their population-weighted average is 42.5 µg/m³, against 12.5 in high-income countries. Since 2010 three in four high-income countries have cleaned their air, against fewer than half of lower-middle-income ones.
Air pollution currently hides a large share of greenhouse warming: sulphur dioxide alone has offset about 0.4°C. Cleaning the air without also cutting methane adds warming in the IPCC's own scenario data, while cleaning the air and cutting methane together removes almost all of that penalty by 2050. Pollution and climate are one feedback system, and the levers that work on both — methane, black carbon and ozone precursors — come first.
Humanity will live about 739 billion person-years between 2025 and 2100. On current trends, 180 billion of them will be spent under at least two of three hazards: polluted air, a hot climate and a high-risk country. Counting exposure cumulatively shows that clean air and resilience with peace each avoid more of those years this century than the gap between warming pathways, though mitigation decides how many people end up near the edge of the human climate niche.
From 2000 to 2024, about 174 million children died before their fifth birthday, more than ten times the 14.9 million excess deaths of the pandemic's first two years. Today 69% of those child deaths fall in the high-risk countries that hold a quarter of humanity. Matching the best quarter of each income group would avert 2.4 million child deaths a year, nearly half the total, and 34 million more by 2050 than on current trends.
Internet use has exceeded electricity access by more than five points in only 10 of 3,072 country-years across the Global South, and health coverage has rarely passed 60 before electricity reaches 90 per cent. Yet health is the slowest layer to build. On current trends only 28 of 129 low- and middle-income countries reach universal energy, water, health and digital access by 2050. Their data shows the order in which to build.
Extreme wildfires have more than doubled in two decades, methane rose at record pace in 2020–21 as warming wetlands released more, and ozone already cuts global soybean yields by about an eighth. Mapping five pollution–climate feedback loops shows where each can be cut most cheaply, from leaking gas wells to cooking stoves.
With the 2030 Agenda two-thirds spent, 36 per cent of assessable SDG targets are on track or moving moderately and 15 per cent have gone into reverse. The pattern beneath those numbers is not random, and it says a good deal about where the remaining effort should go.
Air pollution contributed to 7.9 million deaths in 2023, and an estimated 5.13 million excess deaths a year are attributable to fossil-fuel air pollution that a transition would remove. The burden is heaviest in the thirty-three megacities, where combustion is densest and exposure closest. This report sets out the evidence that decarbonization is, in practice, the largest public-health programme available to them, and how to design it to collect that return.
Cheap adaptation technologies with strong measured returns are distributed and then abandoned. The usual explanations blame the money or the country, but neither accounts for two technologies diffusing at wildly different rates through the same channel. Five attributes of the product explain most of the variation.
Climate change and air pollution come out of the same combustion, which has made it natural to treat them as one problem. They differ in residence time by five orders of magnitude, in the geography of their harm, and in the sign of their effect on the planet's energy balance — and each difference changes what a combined strategy can do.
Pollution, poverty and climate cause one another in every direction, and are managed by three ministries on three timetables. Integrated strategies keep failing not because the analysis is wrong but because integrated things must still be bought by a single budget holder on a single clock. The remedy is to appraise on the fastest.
The clean transition is usually argued as climate policy — a cost accepted now for a distant temperature. Read instead as risk-mitigation infrastructure, it lowers four coupled dangers at once: climate destabilisation, air-pollution mortality, energy insecurity and coercive energy geopolitics. The operative variable is not ambition but deployment.