EXPLAINED | 2026 Could Rank Among the Four Hottest Years. Where Does the Heat Go?

The World Meteorological Organization, the UN’s weather and climate agency, said on 9 November that 2026 is on track to be one of the four hottest years since records began around 1850. The report, released as the COP31 climate talks opened in Türkiye, also found that global sea level had reached a record in the satellite era. The two findings are linked. As the ocean absorbs heat, seawater expands and takes up more room.

What did the UN report find?

The global average surface temperature from January through September 2026 was about 1.47°C above the 1850–1900 average. The agency used nine datasets to make that estimate. All four years from 2023 to 2026 are on course to rank as the four hottest, though 2026’s exact place on the list still depends on the last months of the year.

Where does most of the extra heat go?

Into the ocean. Greenhouse gases such as carbon dioxide slow the escape of heat to space. Earth then takes in more energy than it sends back out. The ocean absorbs about 90% of that surplus. A large body of water can take up a great deal of heat while its temperature changes relatively slowly. Currents and mixing also carry some of that heat below the surface. That is why a single year’s air temperature tells only part of the story.

How can scientists tell what is happening deep underwater?

They send instruments down. Argo, an international network of drifting floats, measures temperature and salt content from near the surface down to about 2,000 metres. The floats transmit readings when they surface. Measurements at different depths let scientists estimate how much heat the ocean is storing. The WMO says preliminary data through July point to a tenth consecutive year of record heat in the upper 2,000 metres.

Why is El Niño making 2026 hotter?

El Niño is a recurring shift in the tropical Pacific. The winds that usually push warm surface water west weaken. Warm water spreads east, and more heat passes from the ocean into the air over the central and eastern Pacific. That can push the global surface temperature higher for a time. It helps explain why some years are hotter than others. The long-term buildup of heat comes chiefly from human greenhouse gas emissions.

How can 2026 be at 1.47°C and still finish above 1.5°C?

The 1.47°C figure covers nine months. Copernicus, the EU’s climate service, used its own dataset through October to project 1.56°C to 1.61°C for the full calendar year. It expects 2026 to be the second year above 1.5°C in its record, after 2024. The Paris Agreement’s temperature goal is judged over decades. A year above 1.5°C shows how close the world is getting to that level of sustained warming.

How can the sea rise without more water being added?

When seawater warms, the same amount of water takes up more space. Scientists call this thermal expansion. Melting glaciers and ice sheets on land raise the sea in a different way by adding water. Both processes help explain why the global average sea level reached its highest point in the satellite record, which began in 1993.

Does the sea rise at the same speed along India’s coast?

The rate varies by region. A study of the North Indian Ocean found that sea level rose by about 5.2 millimetres a year in the western Bay of Bengal from 2003 to 2024, compared with 4.3 millimetres in the western Arabian Sea. Across the whole basin, the researchers estimated that warming and expansion accounted for about 46% of the rise. Winds, currents and changes in salt content also help explain why the rates differ. These figures describe stretches of ocean. To see what the rising water means for a particular city, scientists also have to measure what the land is doing.

What does Chennai’s tide gauge tell us?

Chennai’s gauge records the height of the sea relative to a fixed point on land. A study of its readings found that the water rose by about 2.8 millimetres a year from 1993 to 2023. The same study used satellite data to show that some parts of the city are sinking. When the ground sinks, the gap between the sea and the streets narrows further. A cyclone’s winds can then push water ashore from a higher starting point, making it easier for low-lying areas to flood.

Could El Niño keep temperatures high in 2027?

Yes. The WMO expects this El Niño to persist into early 2027. It says El Niño often has its biggest effect on global temperatures in the year after it develops. India’s ocean-monitoring agency has also warned that waters in the Arabian Sea and Bay of Bengal could put marine life under particular heat stress in March to May 2027, with possible effects on sardine and mackerel catches. That remains a forecast. The WMO’s final report, due in March 2027, will establish where 2026 ranked, while Indian observations will show how the warming plays out closer to shore.