Climate Models: How we know what climate change will do next

5 minute read

Updated on: 28 Jun 2020

You may have heard a lot about how global temperatures are going to increase dramatically in the near future due to climate change. But how do we know this?

Sorry to all of you car-loving readers, but in this chapter we’ll actually be talking about simulations of the Earth’s climate [ref]. Still, it’s pretty cool to be able to make predictions of the future right?

Image of Predictions to Policy Action

Predictions to Policy Action

Review: What is the climate?

The climate system involves the atmosphere, oceans, ice, land, and all living things on Earth [ref]. Interactions between these different elements mean that the climate system varies constantly [ref1,ref2]. For example, much of the water we experience as rain over the land areas we live on actually originates from evaporation from the ocean surface [ref]. The climate can also be forced to change by events that are not part of the natural climate system, like volcanic eruptions [ref] or increased CO₂ emissions [ref]. These are called forcings [ref].

Image of The Climate System

The Climate System [ref1,ref2,ref3]

How do climate models allow us to do this?

Climate models make predictions by simulating the interactions between parts of the climate system and external forcings [ref]. To do this, scientists must represent these interactions using complex scientific equations [ref1,ref2,ref3]. For example, some equations will be based on making sure the energy [ref1,ref2] from the Sun is equal to all the energy absorbed or reflected by the Earth and the clouds in the atmosphere [ref].

Image of Atmosphere Energy Balance

Atmosphere Energy Balance [ref1,ref2]

Climate scientists make predictions for future climates using climate models, by putting possible scenarios for amounts of CO₂ emissions and other variables into equations [ref].

Are climate models accurate?

Climate models have been used to make accurate predictions for the past 50 years [ref] and have got a lot better during this time [ref].

Scientists know this because they test their models using data from past climates [ref]. If a climate model can simulate past climates, then it is more likely to correctly simulate future climates [ref].

For example, the models used in a scientific report written by thousands of scientists in 2013 correctly replicated past global surface temperatures with a 99% success rate [ref]!

Image of 99% success rate

99% success rate [ref]

Scientists are constantly working to check [ref] and improve [ref] how accurately their models make predictions, but even so, models can never be 100% accurate [ref].

For this to happen, scientists would need to understand and simulate every aspect of the climate system [ref] and know exactly how each and every one of us would act in the future. Without a crystal ball, this is quite difficult [ref1,ref2]!

If climate models aren’t 100% accurate, why use them?

Despite some uncertainty in climate model predictions, they are extremely useful.

A key point to realise is that climate scientists don’t need to predict the exact future to help policymakers; by using several different, well thought out scenarios of human responses to climate change (from doing nothing to doing a huge amount), climate modellers can give policymakers an idea of the range of possible changes in climate [ref1,ref2] resulting from different policy actions [ref1,ref2].

Image of Predictions based on Policy

Predictions based on Policy [ref]

Can you see in the graph that if we don’t take any climate action, temperatures could rise by anywhere between 3°C to 10°C by 2200 [ref]? We don’t know, but either way that is certainly going to be bad for us!

Climate models can inform policymakers with information and evidence to start making well-informed decisions about future environmental actions [ref1,ref2].

For example, greenhouse gas emissions will increase future temperatures and affect future weather patterns [ref]. Models can be used to predict how human activities, such as increased emissions, will affect the climate [ref].

Conclusion

All climate models have limitations but, properly used, they can make important contributions to tackling climate change.

Next chapter!