Climate Models: Simulating the Earth

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Climate models can give us a great deal of information about what sort of rules the climate follows and how the climate might look like in the future. A climate model is the result of a simulation run on a virtual Earth. This simulation mimics the real Earth and its climate as well as any influences the planet might have on the climate. They are used to predict the future of the climate using computers.

Big Ideas: 
  • Climate models simulate the Earth's climate so that we do not have to wait for the consequences to arrive before making decisions.
  • They predict the future of the climate using complicated equations solved by powerful computers.
  • We know they work because they can be used to predict historical data and their results match with what really happened.

To predict what the Earth's climate might look like in the future, given many different factors, scientists often use computational climate models. These virtual Earths can have their climates simulated many years into the future. On virtual Earth, everything, including land, atmosphere, water, and sea ice, is converted to a computerized representation. The components of this simulation are then related to one another through mathematical equations based on the laws of physics. Like how a photograph on your computer is broken up into tiny square pixels, discrete points of data, these computer models also break up, or "discretize", the simulation of the Earth into a mesh of points. For this mesh of points, the computer solves equations to calculate what happens for each point. When the millions and millions calculations are complete, the results show how the climate evolves with time. These simulations are now so fine-grained in time and space that the same codes are used for weather forecasting (i.e. short-term, local atmospheric conditions) as well as decades-long climate predictions.

Climate models are used to predict future climate change, but they can also be used to predict the causes of past climate change as well. This prediction of causes is called "attribution". In the process of attribution, climate models are first used to estimate how certain factors, such as greenhouse gas emissions from human activity, could affect the climate, and what patterns they would have caused. Using statistical tools, scientists find out whether these patterns exist in real climate observations and measurements gathered over the past century. They do another simulation without this factor, and see if those results match the real historical data better, or worse. Scientists have found that, without the inclusion of human influences into the simulation, the climate model predictions do not match (and deviate far from) the climate observations of the latter half of the 20th century.

Climate models and their results can help us make informed policies and decisions that will influence the future of our climate. They provide climate values predicted using mathematical equations derived from the laws of physics and have been experimentally shown to be accurate by using observations in the real world and comparing them against simulation results. By providing these models with "what if" scenarios it is possible to see what the future might look like for the climate as time progresses with humanity taking one course of action versus another. The predicted results of the climate model might help us better make decisions with regards to global greenhouse gas emissions, to adapt to, prepare for, and mitigate a changing climate.

To find out more about how climate models are used, take a look at this video presented by the Pacific Institute for Climate Solutions:

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