Chapter 1
Climate change is best measured as the gap between what was projected…
Climate change is best measured as the gap between what was projected and what is now observed — and, separately, between what was promised and what has been delivered. On the physical side the projections have broadly held: assessments going back to the 1970s have tracked the warming that followed, and the IPCC's 2013 forecast that temperatures would run 0.3–0.7°C above their 1986–2005 level by the 2030s is running through the middle-to-warm half of its own range. The world is now routinely brushing 1.5°C — 2024 was the first calendar year above it, and 2026 is being fought over as second-, third- or fourth-warmest depending on the dataset.
Chapter 2
The cause is not in dispute
The cause is not in dispute. Fossil-fuel carbon dioxide emissions rose again in 2025 to a record 38.1 billion tonnes, total greenhouse gases reached a record 57.7 billion tonnes of CO₂-equivalent in 2024, and the Global Carbon Project judges the remaining budget for a good chance at 1.5°C virtually exhausted — roughly four years of emissions at current rates. Newer work sharpens it: warming is measurably weakening the land and ocean sinks that have absorbed much of humanity's carbon, so a growing share of each year's emissions stays in the air. The consequences arrive as attributed extremes — a lethal June heat dome over western Europe, then record wildfires in France and Spain that formal analysis tied directly to human-caused warming.
Chapter 3
The political record is the weaker half
The political record is the weaker half. Copenhagen collapsed in 2009 into a five-page accord that bound no one but invented the architecture everything since has used: each country files its own target and is held to it by disclosure rather than sanction. Paris formalised that in 2015 with near-universal membership and no enforcement, and the IPCC's 2018 special report turned 1.5°C from an aspiration in the treaty's text into the number the argument is conducted in — while showing it would need global CO₂ down about 45% from 2010 levels by 2030. Emissions have risen since. The one promise that was measurably kept, the $100bn a year of climate finance pledged at Copenhagen for 2020, arrived two years late. COP30 in Belém, ten years after Paris, produced a voluntary roadmap away from fossil fuels rather than a binding phase-out, and the IPCC itself has now deadlocked four times running on when its next assessment will even appear.
Chapter 4
The genuine surprise has come from the energy system
The genuine surprise has come from the energy system, and it has run the other way — faster than forecast rather than slower. In 2025 renewables overtook coal worldwide for the first time in a century, record solar growth met all of the year's rise in electricity demand, and global fossil-fuel generation stopped growing, falling even in China and India. The IEA had put that crossover in the early 2030s as recently as 2015. Forecasting the physical system has been the harder discipline in the other direction: a run of predictions that the Arctic would be ice-free in summer by 2016, then 2017, then 2018, missed by more than a factor of four, and the field said so at the time. So the topic turns on a single question — whether the transition now visible in electricity can spread across the rest of the economy fast enough to bend the emissions curve before the budget is gone.
And now
Carbon dioxide in the atmosphere averaged 426.8 parts per million in 2025, 153% of the pre-industrial level, the World Meteorological Organization reported on 23 October. Methane and nitrous oxide also set records. The year’s rise, 2.8 ppm, was slower than the one before, as land carbon sinks recovered after the last El Niño.
The plans meant to bend that curve fall short. The UN climate secretariat’s synthesis of 127 new national plans, published on 27 October, finds that delivered in full they would bring emissions to about 6% below 2019 levels by 2035, or 9% with their conditional pledges. It calls that “substantially off track” for 1.5°C. A week earlier, UNEP put the world on course for 2.6°C even if every plan is kept.
The Lancet Countdown linked heat to a record 710,000 deaths in 2023, more than 70% of them attributable to warming. In Japan, warming added 9% to the moisture behind Typhoon Dujuan’s deadly rains, though its effect on the rainfall itself could not be pinned down.
The IPCC will reconvene online on 1–3 December to try again on its assessment timetable. In the US, the EPA has proposed loosening its methane rules for oil and gas.
Where it stands today →