Indonesian peat fires put 19.7 million tonnes of CO2 into one week of September

Fires on Borneo and Sumatra released 19.7 million metric tonnes of carbon dioxide between 1 and 7 September, according to Fire Emissions Watch, the Copernicus portal run with European Union climate data. That figure overtook Russia for the week and accounted for more than a third of all recorded wildfire carbon on the planet. Intensity in the worst cells passed 1,500 kilograms per square kilometre, more than ten times the Russian level for the same days.

Emissions sat 273 percent above Indonesia's seasonal average and still below the 21.7 million tonnes recorded in the matching week of 2015, the last comparable El Niño year. The season is not finished. Copernicus scientists have also warned that peat burning underground is easy to undercount from space, so 19.7 million tonnes is a floor.

Pontianak, the capital of West Kalimantan, logged an air-quality index of 394 on 9 September on IQAir's scale. Anything above 300 is classed as hazardous. Indonesia's health ministry recorded respiratory infections rising from 50,891 cases on 1 September to 113,336 on 9 September. NASA's Aqua satellite, on 1 September, saw both surface flame and heat consistent with fires in drained peat.

Why peat changes the arithmetic

Indonesia holds about 36 percent of the world's tropical peat. Drained peat does not burn like a grass fire. It smoulders in the soil, often for days, and throws up carbon that satellites can miss if the flame front is cool or buried. Pantau Gambut, an Indonesian monitor, has counted more than 28,000 peat hotspots in 2026, including more than 1,600 inside active oil-palm concessions in West Kalimantan.

Hotspot counts from 1 August to 8 September reached 13,443, against 9,454 in the same stretch of 2015. Area burned in August was estimated near 600,000 extra hectares across Kalimantan, Sumatra and South Papua. In 2015 the country lost 2.6 million hectares in a full year.

About 90 percent of Indonesia had little or no rain in early August, according to the national weather agency. El Niño is the near-term driver. Land conversion is the longer one. Once peat is drained for plantation, a dry year finds fuel that a wet forest would have denied it.

Haze and a new capital

Fires have pushed toward Nusantara, the new administrative capital in eastern Borneo. Haze from Kalimantan and Sumatra does not stop at the water. Singapore and Malaysia have lived through this cycle before. The 2015 event closed schools and grounded flights across the strait.

Officials in Jakarta still compare this week with 2015 and note that the number is lower. That comparison is true and thin. 2015 was a disaster year. Sitting just under it in week one of September, with peat still dry and the season open, is not comfort. It is a warning that the next fortnight of wind and rain will decide whether 19.7 million tonnes is a spike or a preface.