The missing middle: The most likely climate scenario the world is tracking

Most institutional climate analysis starts from one of two scenarios: a 1.5°C world of rapid decarbonization, or a 4°C hot-house world. Regulators ask for them, and they fill most stress tests and disclosure reports. They are also the two least likely outcomes. Halving global emissions within 25 years has no support in the observed record, and emissions climbing through 2050 runs against the decoupling of growth from carbon in most major economies.

Every scenario gets a probability

This research runs the observed emissions record forward thousands of times and measures which standard scenarios each path resembles. Scenarios are compared on cumulative carbon from 2000 to 2050, the quantity that drives warming, using Global Carbon Budget data. The library covers 19 IPCC, NGFS and Inevitable Policy Response scenarios, and none is discarded.

The tails hold less than 0.2%

Together, the 1.5°C fast-cuts and rising-emissions worst cases carry under 0.2% of the probability. Almost the whole distribution sits between pledges being kept and today’s policies only, with a single scenario carrying more than 70% of the weight. Blending every scenario by its probability gives one central pathway, the Emmi most-likely scenario, along with the warming it implies.

Report against the tails, invest against the expected world

Disclosure is a stress test, and the prescribed tail scenarios remain the right tool for it. Investment decisions run on expected outcomes. Under a 1.5°C pathway, every company in the paper’s sample of major listed companies shows maximum transition risk. Under the closest published match to the expected case, utilities and airlines fall to low single digits or low tens of percent. A coal-heavy utility stays at the maximum, which shows the expected case still flags structural risk where it exists.

Download the full white paper to see which future the world is tracking and the warming it implies.