1. Understanding Models Activity 3: Atlas of Change

2. What does “model” mean to you?

3. What is a scientific model? Model: a representation of a part of the real world – A model shares some characteristics with the thing it represents, but not all. – A model is simpler than the real thing. – There are many different types of models. “All models are wrong, but some are useful.” -George Box

4. What are models for? Models explain observations or data Example: Geocentric (Earth-centered) model of the solar system – Explained observed motion of stars – Predicted future motion 16 th century representation of the geocentric model by Portuguese cosmographer Bartolomeu Velho.

5. Geocentric vs. Heliocentric Models In 1543 Copernicus suggested that the sun (not the Earth) was at the center of the solar system. – Heliocentric (sun-centered) solar system – Explains some observations that the geocentric model could not explain Early 18 th century depiction of the heliocentric model of the solar system.

6. Assessing Accuracy of Models Accuracy of projections – Hindcasts Forecasts look forward; hindcasts look backward Does the model fit observations made so far?

7. Assessing Accuracy: Climate Models Test against recent data Test against data from the distant past Test against other models Scientists collect and analyze ocean sediments for clues into what the climate was like in the distant past.

8. Scientific Uncertainty Understanding uncertainty – How we use the term – How scientists use the term Complexity and uncertainty – Many different variables interact with each other – Difficult to predict with certainty – Examples Weather models Ecosystem models Climate models

9. Dealing with Uncertainty Using statistics – Run model multiple times (virtual experiments) – Use multiple models and combine results – Suggest a range of probable outcomes

10. Example: Modeling Hurricanes

11. Other Uses for Models Understanding a system better

12. Outputs of Models Current conditions Hadley (High Emissions) Hadley (Low Emissions)