Climate Change: Demystifying the Application of Earth Systems Models for Climate Science

1. Climate Change: Demystifying the Application of Earth Systems Models for Climate Science Richard B. Rood Cell: 301-526-8572 2525 Space Research Building (North Campus) rbrood@umich.edu http://clasp.engin.umich.edu/people/rbrood June 20, 2017

2. Some Resources • Gettelman and Rood: Demystifying Climate Models: A User’s Guide to Earth Systems Models • Springer, Open Source, (It is free.) • Introductory Material OpenClimate Mini-page • Model Introduction OpenClimate Mini-page • Rood’s Class MediaWiki Site • http://climateknowledge.org/classes/index.php/Climate_Change:_The_Move_to_Action

3. Outline • Models • Definition • Models and Scientific Investigation • Models in Climate Science • Establishing Trust: Numerical Experimentation • Looking Towards the Future • Summary

4. Assumption • I am talking to an audience that knows what “model” means in the context of weather and climate science. • Knows the jargon of meteorology From: http://www.halfhull.com/main.jpg

5. What is a Model? • Model (Dictionary) • A schematic description of a system, theory, or phenomenon that accounts for its known or inferred properties and may be used for further studies of its characteristics

6. We live lives full of models • Models are everywhere in our lives and work • Architecture • Epidemiology • Aerospace • Computer assisted design • Games • The bridge over the Missouri River • Landing things on Mars • Investing my retirement account • How much rent can I afford • My digital thermometer

7. What is a Model? • Model (Dictionary) • A schematic description of a system, theory, or phenomenon that accounts for its known or inferred properties and may be used for further studies of its characteristics • Weather and Climate • Provide numerical approximations of the equations that describe the atmosphere, land, ocean, ice, biology of the Earth – • process definition, diagnostics, predictions, and projections • Solves conservation equations: • energy, momentum, mass

8. Models and Scientific Investigation OBSERVATIONS THEORY EXPERIMENT

9. Models and Scientific Investigation OBSERVATIONS THEORY PREDICTION

10. Models and Scientific Investigation OBSERVATIONS PROCESSES SIMULATION

11. Computational Science (Post and Votta, PhysToday, 2005) • Computational Science & Numerical Simulation • Given what we know, can we predict what will happen, and evaluate (validate) that what we predicted would happen, happened? • Validation: Comparison with observations • Philosophy: Do we ever know if we get the right answer for the right reason? • Computational and natural science: Establish the credentials of a model to help inform us about the application for which the model was designed.

12. Models in Climate Science

13. Models and Model Infrastructure Infrastructure Models & Model Simulations Connects it all together. Critical for - Scientific credibility - Collaboration - Development - Efficiency - Analysis - End user Solves the conservation equations - Mass - Momentum (~ weather) - Energy (~climate) Split into “processes” - Fluid dynamics - Radiation - Moist physics - Turbulence

14. Observations and Models: Processes Infrastructure Observations Models & Model Simulations PROCESSES DIAG. & TEST Define & test model “physics” Diagnostic applications

15. Observations and Models: Weather Forecasts Infrastructure Observations Models & Model Simulations INITIAL COND. FORECASTS Start Forecasts Validation Prognostic applications

16. Observations and Models: Assimilation Infrastructure Observations Models & Model Simulations MELD Assimilation & Reanalysis Initial Conditions Validation Scientific Investigation Data System Monitoring

17. Observations and Models: Predictions and Projections Infrastructure PROCESSES PREDICTIONS Observations Models & Model Simulations INITIAL STATE PROJECTIONS Define & test model “physics” Diagnostic applications Prognostic applications Start Forecasts Validation Assimilation & Reanalysis

18. Complexity / Types of Models(Rood, Perspective) • Conceptual / Heuristic Models • Integrated, theory based (ex. Geostrophic balance) • Statistical models • Past behavior and correlated information used to make predictions • Physical models: First principle tenets of physics (chemistry, biology) • Mechanistic: some aspects prescribed • Comprehensive: coupled interactions, self-determining • (State Earth will Warm) • (Details of Warming, Feedbacks)

19. CLOUD-WORLD BIOLOGY BIOLOGY The Earth System Model: Climate Models SUN ATMOSPHERE OCEAN ICE (cryosphere) LAND

20. Establishing Trust: Numerical Experimentation • Hindcasting • Historical simulation

21. Medieval warm period • “Little ice age” • Temperature starts to follow CO2 as CO2 increases beyond approximately 300 ppm, the value seen in the previous graph as the upper range of variability in the past 350,000 years. Let’s look at observations from the last 1000 years Surface temperature and CO2 data from the past 1000 years. Temperature is a northern hemisphere average. Temperature from several types of measurements are consistent in temporal behavior.

22. Let’s look at just the last 1000 years Surface temperature and CO2 data from the past 1000 years. Temperature is a northern hemisphere average. Temperature from several types of measurements are consistent in temporal behavior. { Note that on this scale, with more time resolution, that the fluctuations in temperature and the fluctuations in CO2 do not match one-to-one. What is the cause of the temperature variability? Can we identify mechanisms, cause and effect? How?

23. What do we do? • We develop models based on the conservation of energy and mass and momentum, the fundamental ideas of classical physics. (Budget equations) • We determine the characteristics of production and loss (forcing) from theory and observations of, for instance, the eruption of a major volcano and the temperature response as measured by the global observing system. • We simulate the temperature (“Energy”) response. • We evaluate (validate) how well we did, characterize the quality of the prediction relative to the observations, and determine, sometimes with liberal interpretation, whether or not we can establish cause and effect.

24. Schematic of a model experiment. Model prediction without forcing Model prediction with forcing Model prediction with forcing and source of internal variability, for example, El Nino, Pacific Decadal Oscillation Observations T Start model prediction T Statistical representation – not deterministic

25. What do we know from model experiments and evaluation (validation) with observations • With consideration of solar variability and volcanic activity, the variability in the temperature record prior to 1800 can be approximated. • After 1800 need to consider the impact of man • Deforestation of North America • Fossil fuel emission • Change from coal to oil economy • Clean Air Act • Only with consideration of CO2, increase in the greenhouse effect, can the temperature increase of the last 100 years be modeled.

26. Let’s look at the “modern” record. • Modern ~ Industrial Revolution ~ Last half of 1800s • When we have direct temperature measures

27. Figure TS.23 20th Century Simulations Example of Attribution

28. 20th Century Simulations Meehl et al., J. Climate (2004)

29. Look towards the future. • Surface temperature anomaly • Intergovernmental Panel on Climate Change (IPCC, every ~ 5 years) • IPCC assesses, does not “do” research • Coupled Model Intercomparison Project (CMIP) • Scientist community designs protocol to evaluate and establish trustworthiness of climate models • CMIP is not the same as IPCC, but are often conflated.

30. IPCC (2007) projections for the next 100 years.

31. Summary: Models • Basic scientific principle or law used in climate science is conservation of energy • Models are an accounting, or calculating the budget, of • Energy • Mass • Momentum • Credibility established by representation of the past, and, when possible, evaluating predictions and projections

32. Summary: Energy Balance of Planet • Earth’s energy balance • Energy from Sun • Energy sent back to space • Things that absorb • Things that reflect • Moving energy around • Storing energy at the surface of the Earth • Greenhouse gases hold the energy a while • Oceans pick it up and hold it longer • Ice takes it up and melts  balances change

33. A fundamental conclusion • Based on the scientific foundation of our understanding of the Earth’s climate, we know with virtual certainty • The average global temperature of the Earth’s surface has risen and will continue to rise due to the addition of gases (esp, carbon dioxide) into the atmosphere that hold heat close to the surface. The increase in greenhouse gases is due to human activities, especially, burning fossil fuels. • Historically stable masses of ice on land have melted and will continue to melt. • Sea level has risen and will rise. • The weather has changed and will change.

35. Outline • Models • Definition • Models and Scientific Investigation • Models in Climate Science • Establishing Trust: Numerical Experimentation • Looking Towards the Future • Summary

36. Some Resources • Gettelman and Rood: Demystifying Climate Models: A User’s Guide to Earth Systems Models • Springer, Open Source, (It is free.) • Introductory Material OpenClimate Mini-page • Model Introduction OpenClimate Mini-page • Rood’s Class MediaWiki Site • http://climateknowledge.org/classes/index.php/Climate_Change:_The_Move_to_Action

37. Poll questions: • I was formally introduced to weather or climate models in school. • Our knowledge of climate change is adequate for us to take action to intervene to reduce carbon dioxide emissions. • Climate models provide adequate information to inform decisions about adaptation. • Climate models are trustworthy. • Provide any comments, qualifications inspired by the questions above. • Write any questions or comments about climate models and climate change you would like to make. • What do you want to get from this presentation?

38. Background Materials

39. Roles of Uncertainty / Variability at Different TimesHawkins and Sutton, 2009

40. Conservation principle • There are many other things in the world that we can think of as “conserved.” For example, money. • We have the money that we have. • If we don’t spend money or earn money, then the money we have today is the same as the money we had yesterday. Mtoday = Myesterday That’s not very interesting, or realistic

41. Conservation principle(with income and expense) Income Mtoday = Myesterday+ I - E Let’s get some money and buy stuff. Expense

42. Conservation principle(with the notion of time) Income Mtoday = Myesterday+ N(I – E) Salary Income per month = I Rent Expense per month = E N = number of months I = NxI and E= NxE Expense

43. Some algebra and some thinking Mtoday = Myesterday+ N(I – E) Rewrite the equation to represent the difference in money (Mtoday - Myesterday) = N(I – E) This difference will get more positive or more negative as time goes on. Saving money or going into debt. Divide both sides by N, to get some notion of how difference changes with time. (Mtoday - Myesterday)/N = I – E

44. Introduce a concept • The amount of money that you spend is proportional to the amount of money you have: • How do you write this arithmetically? E = e*M

45. Some algebra and some thinking (Mtoday - Myesterday )/N = I – eM If difference does NOT change with time, then M = I/e Amount of money stabilizes Can change what you have by either changing income or spending rate All of these ideas lead to the concept of a budget: What you have = what you had plus what you earned minus what you spent

46. Conservation principle Energy from the Sun Income Mtoday = Myesterday + I - E Earth at a certain temperature, T Let’s get some money and buy stuff. Energy emitted by Earth (proportional to T) Expense

47. Some jargon, language • Income is “production” is “source” • Expense is “loss” is “sink” • Exchange, transfer, transport all suggest that our “stuff” is moving around.

48. Equilibrium and balance • We often say that a system is in equilibrium if when we look at everything production = loss. There might be “exchanges” or “transfers” or “transport,” but that is like changing money between a savings and a checking account. • We are used to the climate, the economy, our cash flow being in some sort of “balance.” • As such, when we look for how things might change, we look at what might change the balance. • Small changes might cause large changes in a balance

49. Conservation of Energy • Conceptual model of Earth’s temperature from space

50. Earth: How Change T? Energy from the Sun Stable Temperature of Earth could change from how much energy (production) comes from the sun, or by changing how we emit energy. Earth at a certain temperature, T Energy emitted by Earth (proportional to T)