Climate Model Overview

This page is designed to provide some of the ‘big picture’ context on what climate models are and the types of use cases they’re best suited for – and those that they tend to struggle with as well. We hope this is helpful in providing some conceptual orientation for some of the more detailed topics discussed in the rest of these pages.

What Are Climate Models?

Simply speaking, a climate model is nothing more than a set of computer code. BUT it’s a set of computer code that describes everything that’s happening at every location around the world! …Or at least, everything that we’ve figured out how to describe using equations, which are then broken down or “discretized” along a three-dimensional grid covering the whole planet.

Generally, climate models include representations of physical (and more recently, biological) processes happening in the atmosphere, ocean, and land. The level of complexity of various processes can differ – as can the estimates (sometimes called ‘parameterizations’) of things happening on spatial scales much smaller than the grid boxes that the model breaks the planet down into.

There are already some great explainers out there that go into detail about what climate models are and fundamentally how they work; we like these a lot!

When Are Climate Models Useful?

The uses for climate model output are as varied as the imaginations of the people using them! Here are some of the more common examples:

Academic Research: Traditionally, climate models have been used in academic research applications, which in and of themselves vary quite widely.
Assessment Reports: Model output is also a central feature of climate assessment reports which provide governments with “state of the science” summaries of ongoing and projected future impacts of climate change: the best-known example is of course the Intergovernmental Panel on Climate Change (IPCC), but other national-level assessments also exist (the US National Climate Assessment tends to be particularly in-depth).
Climate Adaptation: Climate model output also features heavily in climate adaptation efforts, which are becoming more and more prevalent as the impacts of climate change become apparent. The US Climate Resilience Toolkit has some handy background information on this topic!
Insurance/risk assessment: More recently, various industries have become extremely interested in using climate model information. The insurance industry was an early adopter, as climate change is altering the probability of (expensive!) climate-driven disasters. Just as one example, here is an explainer by Price Waterhouse Coopers on climate risk assessment – check out their description of emissions scenarios!

How Good Are Climate Models?

Even though climate models are extremely useful for a wide range of applications, like any tool they have imperfections and limitations. Some of the more common ones include:

Limited resolution: The grid ‘boxes’ in most climate models are pretty large: something like 100km (60 miles) on a side. That means that things happening on smaller scales are not going to be very well represented. There are techniques for getting around this (see out pages on downscaling for more details), but generally it’s wise to be cautious when using climate models to describe smaller-scale changes.
Biases in average climate: Models are really good at representing the global-average climate! But when you look in more detail at the spatial patterns of climate variables, you see that they don’t quite match up with the real world. For instance, the location of prevailing weather patterns can sometimes be slightly off from where we see them in real life; climate variability is sometimes centered in slightly the wrong place in the tropical oceans; and the statistics of rainfall aren’t exactly the same as what we observe.

Check out the Carbon Brief explainer section on model limitations for more information!