Can climate models reliably project future conditions?
Based on Science
Climate models provide reliable projections of many aspects of a warming planet over the next century and beyond due to human-caused climate change.
Last update August 23, 2021
Models are the main way that scientists project climate change.
Climate models are sets of mathematical equations based on the laws of physics, chemistry, and biology that are used to understand Earth’s changing climate. Because climate cannot be studied in a laboratory, these models are run on computers to make projections of how the climate is changing.
Scientists use different types of models to quantify different aspects of climate change. They include:
Models to project the amount of greenhouse gases that humans will create
Earth system models to project how Earth’s climate system will respond to those emissions
Impact models to project how the resulting climate changes will affect people
Scientists can test how well climate models perform.
Scientists have been studying climate change for more than 50 years. Climate models have gotten better and better over time.
One way to test how well models perform is to look at older models and see if their predictions came true. A study of 17 climate models going back to the early 1970s found that most of the models did a good job of predicting temperatures in the decades ahead.
In addition to projecting Earth’s climate over long periods, scientists also use models to predict short-term conditions such as weather, the behavior of the jet stream, and events such as El Niño. These predictions have gotten much more accurate over time.
Another way to test models is to see if they can replicate climate changes that occurred in Earth’s past. Models that replicate previous climatic shifts, such as warm periods and ice ages, are considered more reliable. However, it’s important to keep in mind that the future may bring changes that Earth has never experienced before, so past performance can only go so far in guaranteeing reliable model projections for the future.
Scientists are more confident about some projections and less confident about others.
No model is 100% correct, as some degree of approximation is always needed when making projections. Still, models represent what is likely to happen based on our most advanced knowledge and certain assumptions about Earth processes that cannot be directly represented with data.
In general, scientists have a good understanding of how the basic laws of physics, chemistry, and biology govern the atmosphere, ocean, land, ice, and other parts of Earth’s climate system. Based on this information, scientists have high confidence that climate models accurately reflect how the buildup of greenhouse gases is causing the climate to change, especially at the global level.
What is far less certain are the aspects of climate change that depend on people’s behavior. How much greenhouse gas will people add to the atmosphere, and how fast? Will people be able to adapt to climate changes? The answers depend on technology, economics, and policy. Because scientists cannot know the answers to these questions, they come up with a range of plausible scenarios and derive what outcomes might be expected from them.
Through observations and with the help of models, scientists are very certain that:
Earth’s temperature is getting warmer due to human activity
The impacts of climate change will be more costly and harmful the longer we wait to reduce emissions
Climate models accurately reflect the main ways that greenhouse gases affect Earth’s climate system at the global level
Scientists are less certain about:
Exactly how various emission scenarios will translate into local climate conditions
Whether the climate might change in ways that did not occur in the past or that scientists have not been able to study because there are no records
Our actions affect the future climate and climate change impacts.
Most climate models are based on assumptions about future greenhouse gas emissions. People cannot control the way Earth’s climate system responds to these emissions. But we do control the amount of greenhouse gases that we emit. Societies can slow climate change by reducing emissions.
