Indonesia's peat fires already match big El Nino years, and the forecast peak is October

Peat is what makes the arithmetic here different from a bad fire season anywhere else. The carbon under those forests accumulated over millennia, and clearing the trees dries the peat so that it catches in hot, dry conditions; once lit it burns underground, where it is very hard to extinguish ^[12]. So the Indonesian contribution does not scale like scrub. In 1997 and 1998 it reached as much as 2.5 gigatonnes of CO2, described as about a third of annual fossil fuel emissions at the time ^[3]. Run that backwards and the fossil baseline was roughly 7.5 gigatonnes a year ^[16], which means one country's land carbon released the equivalent of four months of global fossil fuel output in a single burning season ^[17]. The 2015 repeat came to 1.5 gigatonnes, three fifths of the 1997 figure ^[4][18].

The 1997 season registered as a jump in global CO2 levels ^[5]. That is the uncomfortable bit for anyone holding an emissions plan: in a strong El Nino, the year-on-year growth in atmospheric CO2 is partly a readout of how much Bornean peat was dry enough to burn, and no power sector schedule governs that variable.

The two specialists quoted are not hedging in the same direction. Adam Scaife at the UK Met Office says he has never seen an El Nino signal this intense in the forecasts, and that 2026 will far exceed recent experience of the phenomenon ^[7]. The forecast Pacific anomaly, possibly above 3C around October, is at least a degree hotter than 1997 or 2015 and six times the 0.5C departure that defines an El Nino at all ^[8][19]. Mark Parrington at the European Centre for Medium-Range Weather Forecasts, who tracks fire emissions for the Copernicus Atmosphere Monitoring Service, puts it more narrowly: it would not surprise him if the fires produced totals similar to previous strong events ^[9]. Similar, not larger. The emissions expectation is not being scaled up with the sea surface forecast, and the reporting does not explain the gap.

Timing compounds the problem. Regional fires normally run August to October and intensify in El Nino years ^[13]; the forecast temperature anomaly peaks around October ^[8]; and ground sensors are already reading smoke at levels previously seen only in El Nino years, with the season young ^[11]. Parrington expects particularly intense fires in the Amazon and parts of North America next year ^[14], so one ocean event delivers its carbon in two instalments landing in two separate annual inventories.

Whether a warming world makes strong El Ninos more likely is unresolved; that their effects are amplified when they do occur is not ^[15]. Meanwhile the smoke from Borneo and West and Central Kalimantan is closing schools and reaching Singapore and Malaysia ^[10], and that cost is settled long before anyone finishes counting the gigatonnes.