Environment

The primary unit of climate collapse is the zettajoule. If you have never heard of this term, you are not alone. Even scientists who work on a planetary scale struggle to relate the immensity of the change measured by this titanic unit of energy.

What is a zettajoule?

A zettajoule is a billion trillion joules. Typed out on a calculator or computer screen, the row of 21 zeros looks absurdly long – a train of seven carriages, each with three empty windows. Experts often have to resort to abstract terms like “unfathomable”, “almost beyond comprehension” and “really big” to ensure our tiny human minds are sufficiently blown away by what these numbers convey.

Why are zettajoules in the news (again)?

When used to calculate the heat on our planet, that train is accelerating and running out of track. The World Meteorological Organization (WMO) warned this week in its latest annual State of the Global Climate report that our world has a huge and growing energy imbalance, which is warming the oceans, the land and the air to dangerous levels.

The new report says Earth’s energy imbalance increased by about 11 zettajoules a year between 2005 and 2025, which is equivalent to about 18 times total human energy use.