# How Climate Models Work — and Why We Should Trust Them

> Climate models are complex, but understanding their basis helps evaluate their reliability. Here is how they work and what gives scientists confidence in their projections.

*Section: Science — By Elena Marsh (Environment & Climate Correspondent) — Published November 26, 2025 — 1 min read*

Canonical URL: https://dailyjunction.co.uk/science/how-climate-models-work
Tags: climate models, climate science, global warming, physics, ipcc

## Key takeaways

- Climate models are built on established physics — thermodynamics, fluid dynamics, radiation — not statistical extrapolation
- Models have successfully predicted phenomena discovered after they were built, the strongest test of their validity
- Uncertainty in projections comes primarily from future emissions scenarios, not from uncertainty in the physics
- The range of model projections gives a probability distribution for outcomes, not evidence that models are unreliable

## What climate models are

Climate models (General Circulation Models or Earth System Models) are mathematical representations of the climate system: the atmosphere, ocean, land surface, sea ice and biosphere. They divide the Earth into a three-dimensional grid and solve equations of fluid dynamics, thermodynamics and radiative transfer to simulate how energy moves through the climate system over time.

## The physics foundation

The core physics in climate models — conservation of energy, momentum and mass; thermodynamics; the behaviour of gases and fluids — is not disputed and has been validated in countless other applications. The greenhouse effect (CO2 and other gases absorbing and re-emitting infrared radiation) is basic physics that has been understood and measured since the 19th century.

## How we know models work

The strongest test of any scientific model is predictive power: can it predict things not yet known when the model was built? Climate models pass this test. They successfully reproduced the cooling effect of volcanic eruptions (the 1991 Pinatubo eruption closely matched model predictions), the pattern of warming (poles warming faster than tropics), the differential warming of land versus ocean, and the stratospheric cooling that accompanies tropospheric warming — a distinctive fingerprint of greenhouse gas forcing rather than solar variation.

## The uncertainty question

Model projections include ranges — for instance, global average temperature is likely to rise between 1.5°C and 4°C by 2100 under high-emissions scenarios. This range does not reflect ignorance about the physics; it reflects primarily two uncertainties: future emissions (dependent on human choices about energy systems) and climate sensitivity (how much warming results from a doubling of CO2, which depends on feedback processes like cloud behaviour). The uncertainty is real and honestly characterised; it cuts both ways, with the upper end of the range representing worse outcomes than the central estimate.

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## Sources

- [Nature](https://www.nature.com)
- [New Scientist](https://www.newscientist.com)

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