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Unit 7 Climate Models

HOW TO CLIMATE MODELS WORK?

This is a graph of how computer climate models have evolved.  Source: intergovernmental panel on Climate Change, Third Assessment Report, Technical Summary of Working Group I Report, 2001

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When you run into climate deniers they often say that computer models that are predicting global warming, melting of the ice caps, and sea level rises, etc., are not accurate.  Computer models are complicated so, I’d like to start off with what are computer models, then I’ll address the deniers later.

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What is a climate computer model? In essence, they are extremely complicated mathematical formulas that ingest data about our world into a huge set of computers.  Those formula’s then make forecasts of the effects of increasing carbon on our climate by taking into account the Earth’s natural cycles, physics, chemistry of the air and ocean, land forms, and organisms on earth, along with energy inputs from the sun, plus a lot more!  The result forecast the Earths climate in a time frame from years to centuries in the future.

There are many different models, some focus on just one factor (like ice cover) while others can take a world view of many different factors in our climate.  Carbonbrief.org does a good job of explaining climate models, the site says “scientists put the fundamental physical equations of the Earth’s climate into a computer model, which is then able to reproduce – among many other things – the circulation of the oceans, the annual cycle of the seasons, and the flows of carbon between the land surface and the atmosphere”.

Scientists started using computer models with the invention of the computer.   The math and science existed of weather and climate forecasting existed in a very basic form before computers, but the amount of time it took to preform the calculations were too large for humans to complete by hand in a timely manner.  The first computer models were crude, simulating climate with just a flat land and an atmosphere.  Things such as oceans, topography and biology were added later.

Computer models of the climate in the 1970’s started to lock onto the idea that the burning of hydrocarbons was going to lead to a warming of the climate.  As the computer models advanced, this warming trend continued to be forecast.  Today’s computer models are extremely complicated and as computer power increases, so do the computer models complexity.  The alarming part of the forecast warming is that in the 2010’s models started pointing to an even larger warming of our climate than what was previously forecast.  The more we know about the earth and the process of putting this information into computer models, the more it shows that climate models are still forecasting significant warming (caused by humans) and that if not mitigated, will lead to a very fast and very destructive temperature increase on Earth.  Makes me think of the movie Apollo 13,  “NASA,  we have a problem”.

How do we know these models are accurate?  Much of the world has a good set of records that go back over one hundred years.  We also have climate records from tree ring, ice core, and sea and lake sediment science that discovered climate data goes back thousands of years.  Climate scientists run the models starting at a hundred years back and thousands of years back and forecast the climate up to the present time.  If the models correctly forecast the climate of the past up until now, we know they run well, and all the currently accepted models have this built-in confidence, so their forecasts are considered accurate.  They are not perfect, but the models are the best science we have to forecast Climate Change.

To learn about computer modeling, I highly recommend reading “How do climate models work” by Carbonbrief.org  https://www.carbonbrief.org/qa-how-do-climate-models-work  The Ted presentation on this website is very insightful on how models work. https://youtu.be/JrJJxn-gCdo

Climate deniers will say thinks like we can’t predict the weather correctly in 5 days how can we predict the climate in 100 years from now.  The answer is that the weather and climate are different.  Climate looks at long term trends in temperature, CO2 concentrations, precipitation patterns and we are very good predicting those.  Look at what the computer models have done correctly. From Grist.org: models predict that surface warming should be accompanied by cooling of the stratosphere, and this has indeed been observed;

• models have long predicted warming of the lower, mid, and upper troposphere, even while satellite readings seemed to disagree — but it turns out the satellite analysis was full of errors and on correction, this warming has been observed;

• models predict warming of ocean surface waters, as is now observed;

• models predict an energy imbalance between incoming sunlight and outgoing infrared radiation, which has been detected;

• models predict sharp and short-lived cooling of a few tenths of a degree in the event of large volcanic eruptions, and Mount Pinatubo confirmed this;

• models predict an amplification of warming trends in the Arctic region, and this is indeed happening;

• and finally, to get back to where we started, models predict continuing and accelerating warming of the Earth's surface, and so far, they are correct.

CLASS ACTIVITIES

Activities concerning climate modeling can go in many directions.  For most teachers, I’d like to de-emphasize the math involved, as you will lose most of your students quickly.  I’d encourage you to show the different inputs and cycles that these models use to forecast the future climate.  These are subjects we covered in interconnectedness.  For your advanced mathematics students, you can obviously show them the basic equations used in climate model. We certainly need future mathematicians and scientists that can create more accurate climate models!  Some questions about climate models you will want your students to think about include:

• What is a computer model?

• How can 100 year or 10,000 year models work when we can’t forecast weather more than 5 days in advance?

• What’s the importance of having more than 1 computer model?

• Are computer models getting better at forecasting?

• What are the latest computer models forecasting?

• Are there any large scale forcing mechanisms that are warming our climate besides human added CO2?

Very basic video on how climate models work. By the UKMET office.

A Great video by SciShow is on YouTube.  While the presenter speaks quickly (I recommend taking the video in chunks) he does a very good job explaining why climate models are accurate at predicting increasing temperatures.  https://www.youtube.com/watch?v=i9EyFghIt5o

Class activities on climate models by High Adventure Science: https://authoring.concord.org/sequences/476/activities/9339/63b05f68-8cac-4133-835f-121a62fef301?show_index=true

Students can experiment online with CO2 concentrations and adjust those to see the effect on temperature.

http://has.concord.org/global-climate.html

Ttwo news article on how new finding on Earth’s systems challenge climate models:

More dust in atmosphere https://www.space.com/earth-atmosphere-dustier-thought-climate-models.html

Oceans absorbing more CO2 than expected https://newatlas.com/environment/study-ocean-absorbs-double-co2/

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