An extra month of dangerous heat for 560 million children, and the arithmetic behind "nearly triple"

Divide the two headline figures by their own percentages and the cohorts behind them fall out. Up to 560 million children is 43 percent of the world's under-10s, which implies an age band of about 1.30 billion ^[2][15]. The 190 million people in their 60s carrying the same extra month are 30 percent of theirs, implying roughly 630 million ^[3][16]. The children's band is a little more than twice as large before any heat is counted ^[16]. So the per-person gap is 43 against 30, about 1.4 to one, and the near-triple headcount gap is that 1.4 multiplied by the demography ^[17][14]. Both are true statements about unfairness. They are not the same statement, and the one that survives a shrinking birth cohort is the smaller one.

That distinction runs through the projections, where the shares move faster than the heads. Between the 1.5C and 2C snapshots the count of children with an extra month rises by 30 million, while the share rises ten points, from 49 to 59 percent ^[4][20]. Back out the denominators and the reason shows: about 1.27 billion children in the first, about 1.10 billion in the second, a fall of roughly 13 percent ^[19]. The published figures are rounded to two digits, so those implied totals are approximate. Anyone quoting 59 percent should say that part of the increase is fewer children rather than more heat.

The cleanest attribution number in the release is the other one. For total heat stress of five months or more, the study sets 120 million children in a world without human influence against 350 million today, which is 230 million children in that bracket who would not otherwise be in it ^[6][18]. That statistic names both worlds, which the extra-month figure does not. It is also worth noting that 560 million is presented as an upper bound, with no lower bound printed ^[2].

None of this lands evenly. The largest increases in humid heat are in tropical regions and poorer countries, where populations are younger, and South Asia, Southeast Asia and West Africa hold the most exposed children today ^[8]. Humid heat is the chosen variable because it stops sweat from doing its job ^[9], and small bodies heat up faster and sweat less efficiently than adult ones ^[10]. Rosa Pietroiusti of VUB, the lead author, said climate change is "already causing hundreds of millions of children to suffer from dangerous heat worldwide," and that children in developing countries face disproportionate exposure now and in future despite having contributed least historically ^[12].