A 4C Pacific anomaly with a date on it: what the record El Nino gives operators to plan against

Percentages hide their own arithmetic. Run the 60 per cent backwards: if the projected peak of 4C above normal is 60 per cent above the previous record anomaly, that old record sat near 2.5C, and the extra 1.5C is the part with nothing to calibrate against ^[8][16][17].

Nick Dunstone of the UK Met Office says the size-to-impact relationship is "fairly linear" across most regions, while conceding it is hard to know which regions get hit worst ^[9]. Taken together those two statements define the planning problem: the magnitude scales, the address does not resolve. On the linearity Dunstone describes, impacts would run roughly 60 per cent above those of the strongest previously recorded event ^[19].

What the Met Office will put its name to is direction. Dry over the Amazon, Borneo, Indonesia and Australia for the next few months as the descending arm of the Walker circulation moves onto them ^[10][1], with wildfire risk in those same places "greatly increased", per Dunstone ^[11]. Dry in Central America, where several major coffee producers sit, and dry across India ^[4]. Wetter than usual in Paraguay, Uruguay and southern Brazil, where the 2015-16 event displaced more than 100,000 people ^[13]. Wetter and stormier in the UK and parts of the US ^[5].

The rice figure carries a date worth reading twice. The anomaly peaks at the end of this year ^[8]. The 9 million tonne fall in global production that analysts expect is attributed to 2026-27 ^[18]. India's monsoon is the weakest since 2009, with rainfall tracking about 15 per cent below average in a country where rain supplies 60 per cent of agricultural land ^[12]. So the meteorology, the harvest and the price all land in different accounting periods, and a hedge or a freight commitment written to the life of the El Nino expires before the shortfall is priced.

For insurers the ledger moves in two directions at once. El Nino intensifies upper-level westerlies, and the resulting wind shear tears at forming tropical storms, which lowers the odds of hurricanes reaching North America in summer and autumn ^[6]. That relief is in Atlantic property wind. The additions are drought, wildfire and inland flood, in other territories and other lines.

The reason historical analogues should be treated as a floor rather than a forecast is stated plainly by Samantha Burgess of the EU's Copernicus Climate Change Service: El Nino is adding heat on top of decades of human-driven warming ^[15]. The evidence is in the calendar. Global average sea surface temperature set a record on 26 August, which is odd because the global ocean is normally warmest in March or April, after the austral summer ^[14]. The event is already the strongest on record on some measures ^[7]. During the 1982-83 super El Nino, the Great Fire of Borneo took out 36,000 square kilometres of rainforest ^[2]; thousands of square kilometres of Borneo are burning again, with peat releasing carbon dioxide ^[3].