2525 Space Research Building (North Campus) 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

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

Models and Scientific Investigation Models in Climate Science Outline Models Definition Models and Scientific Investigation Models in Climate Science Establishing Trust: Numerical Experimentation Looking Towards the Future Summary The Conservation Principle: Balancing the Budget: The conservation of energy and mass, role of atmosphere, ocean, ice, and land; The Earth System; Modeling as budget and accounting, relation to scientific method

From: http://www.halfhull.com/main.jpg 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

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

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 The Conservation Principle: Balancing the Budget: The conservation of energy and mass, role of atmosphere, ocean, ice, and land; The Earth System; Modeling as budget and accounting, relation to scientific method

What is a Model? Model (Dictionary) Weather and Climate 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

Models and Scientific Investigation OBSERVATIONS THEORY EXPERIMENT

Models and Scientific Investigation OBSERVATIONS THEORY PREDICTION

Models and Scientific Investigation OBSERVATIONS PROCESSES SIMULATION

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.

Models in Climate Science

Models and Model 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 Representation of the “physics,” the climate, the theory, and mathematics. Importance of application Integral constraints, conservation laws

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

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

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

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

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)

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

Establishing Trust: Numerical Experimentation Hindcasting Historical simulation

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. 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. Medieval warm period “Little ice age”

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? This is an important point in the ultimate argument, on short time scales co2 and T are not so well correlated. T responds to other factors. These factors will be evaluated based on modeling experiments, which follow from (imperfect) observations of cause and effect as determined by observable events, e.g. volcanos.

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.

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

After 1800 need to consider the impact of man 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.

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

Figure TS.23 20th Century Simulations Example of Attribution Figure TS.23. (a) Global mean surface temperature anomalies relative to the period 1901 to 1950, as observed (black line) and as obtained from simulations with both anthropogenic and natural forcings. The thick red curve shows the multi-model ensemble mean and the thin lighter red curves show the individual simulations. Vertical grey lines indicate the timing of major volcanic events. (b) As in (a), except that the simulated global mean temperature anomalies are for natural forcings only. The thick blue curve shows the multi-model ensemble mean and the thin lighter blue curves show individual simulations. Each simulation was sampled so that coverage corresponds to that of the observations. {Figure 9.5} Example of Attribution

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

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.

IPCC (2007) projections for the next 100 years. Figure SPM.5. Solid lines are multi-model global averages of surface warming (relative to 1980–1999) for the scenarios A2, A1B and B1, shown as continuations of the 20th century simulations. Shading denotes the ±1 standard deviation range of individual model annual averages. The orange line is for the experiment where concentrations were held constant at year 2000 values. The grey bars at right indicate the best estimate (solid line within each bar) and the likely range assessed for the six SRES marker scenarios. The assessment of the best estimate and likely ranges in the grey bars includes the AOGCMs in the left part of the figure, as well as results from a hierarchy of independent models and observational constraints. {Figures 10.4 and 10.29}

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 The Conservation Principle: Balancing the Budget: The conservation of energy and mass, role of atmosphere, ocean, ice, and land; The Earth System; Modeling as budget and accounting, relation to scientific method

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 The Conservation Principle: Balancing the Budget: The conservation of energy and mass, role of atmosphere, ocean, ice, and land; The Earth System; Modeling as budget and accounting, relation to scientific method

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.

Models and Scientific Investigation Models in Climate Science Outline Models Definition Models and Scientific Investigation Models in Climate Science Establishing Trust: Numerical Experimentation Looking Towards the Future Summary The Conservation Principle: Balancing the Budget: The conservation of energy and mass, role of atmosphere, ocean, ice, and land; The Earth System; Modeling as budget and accounting, relation to scientific method

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

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?

Background Materials

Roles of Uncertainty / Variability at Different Times Hawkins and Sutton, 2009

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

Conservation principle (with income and expense) Mtoday = Myesterday + I - E This is the balance equation, basic conservation. Changes come from production and loss. Let’s get some money and buy stuff. Expense

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 This is a meaningful representation of production and loss because it brings in the idea of there being a rate, a time dependency, to the production and loss. If it is just constant, it runs away with time. Expense

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 by the number of months. Now we are headed to a rate in Money and a rate in Time (N). This is essentially a time derivative. Divide both sides by N, to get some notion of how difference changes with time. (Mtoday - Myesterday )/N = I – E

E = e*M 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

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

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. This is the balance equation, basic conservation. Changes come from production and loss. Energy emitted by Earth (proportional to T) Expense

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

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

Conservation of Energy Conceptual model of Earth’s temperature from space

Energy emitted by Earth 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 Income (Production = Energy from Sun) and Expense (Loss = Energy emitted by Earth) figure adapted to the Earth system. Energy emitted by Earth (proportional to T)

The first place that we apply the conservation principle is energy We reach a new equilibrium Changes in orbit or solar energy changes this

The first place that we apply the conservation principle is energy We reach a new equilibrium Changing a greenhouse gas changes this

Or Tomorrow? Balancing the Budget Today’s Money = Yesterday’s Money + Money I Get – Money I Spend Today’s CO2 = Yesterday’s CO2 + CO2 I Get – CO2 I Spend Today’s Energy = Yesterday’s Energy + Energy I Get – Energy I Spend Or Tomorrow?

Conservation principle Conserved Quantities: mass (air, ozone, water) momentum, Energy Need to Define System Need to count what crosses the boundary of the system System depends on your point of view This is important to think about because it strongly constrains what can and cannot happen. There is just so much energy coming into the earth system, and it has to be conserved in the case of a stable climate. It will be slightly out of balance when the climate is warming (holding more energy) or cooling (losing energy). Ultimately, in the climate problem we will require a more detailed examination … namely we are talking about warming (or cooling) at the surface. Conservation will require cooling (or warming) elsewhere in the system, because ultimately, the earth needs to get rid of its energy.

Point of View SUN EARTH PLACE AN INSULATING BLANKET AROUND EARTH FOCUS ON WHAT IS HAPPENING AT THE SURFACE EARTH: EMITS ENERGY TO SPACE  BALANCE

Simple earth 1

Models and Modeling

Models Blogs on Model Tutorial (Start with #3) Models are everywhere Ledgers, Graphics and Carvings Balancing the budget Point of View Cloak of Complexity

What is a Model? Model Numerical Experimentation A work or construction used in testing or perfecting a final product. 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. Numerical Experimentation Given what we know, can we predict what will happen, and verify that what we predicted would happen, happened?

Models are everywhere http://www.halfhull.com/main.jpg

How Many Use Spread Sheets?

Ledgers, Graphics and Carvings  Spreadsheets  Computers

Radiation Balance Figure This is a figure where things are in balance. What goes out = what comes in.

Let’s build up this picture Follow the energy through the Earth’s climate. As we go into the climate we will see that energy is transferred around. From out in space we could reduce it to just some effective temperature, but on Earth we have to worry about transfer of energy between thermal energy and motion of wind and water.

Building the Radiative Balance What happens to the energy coming from the Sun? Energy is coming from the sun. Two things can happen at the surface. In can be: Top of Atmosphere / Edge of Space Reflected Or Absorbed

Building the Radiative Balance What happens to the energy coming from the Sun? Top of Atmosphere / Edge of Space Reflect We also have the atmosphere. Like the surface, the atmosphere can: or Absorb

Building the Radiative Balance What happens to the energy coming from the Sun? Top of Atmosphere / Edge of Space Reflect a lot In the atmosphere, there are clouds which : Absorb some

Building the Radiative Balance What happens to the energy coming from the Sun? RS Top of Atmosphere / Edge of Space For convenience “hide” the sunbeam and reflected solar over in “RS”

Building the Radiative Balance What happens to the energy coming from the Sun? RS Top of Atmosphere / Edge of Space Consider only the energy that has been absorbed. What happens to it?

Building the Radiative Balance Conversion to terrestrial thermal energy. RS Top of Atmosphere / Edge of Space 1) It is converted from solar radiative energy to terrestrial thermal energy. (Like a transfer between accounts)

Building the Radiative Balance Redistribution by atmosphere, ocean, etc. RS Top of Atmosphere / Edge of Space 2) It is redistributed by the atmosphere, ocean, land, ice, life. (Another transfer between accounts)

Building the Radiative Balance Terrestrial energy is converted/partitioned into three sorts RS Top of Atmosphere / Edge of Space It takes heat to Turn ice to water And water to “steam;” that is, vapor 3) Terrestrial energy ends up in three reservoirs (Yet another transfer ) CLOUD ATMOSPHERE WARM AIR (THERMALS) PHASE TRANSITION OF WATER (LATENT HEAT) RADIATIVE ENERGY (infrared or thermal) SURFACE

Building the Radiative Balance Which is transmitted from surface to atmosphere RS Top of Atmosphere / Edge of Space 3) Terrestrial energy ends up in three reservoirs CLOUD CLOUD ATMOSPHERE (LATENT HEAT) (THERMALS) (infrared or thermal) SURFACE

Building the Radiative Balance And then the infrared radiation gets complicated RS Top of Atmosphere / Edge of Space 1) Some goes straight to space 4) Some is absorbed by clouds and atmosphere and re-emitted upwards 2) Some is absorbed by atmosphere and re-emitted downwards 3) Some is absorbed by clouds and re-emitted downwards CLOUD CLOUD ATMOSPHERE (LATENT HEAT) (THERMALS) (infrared or thermal) SURFACE

Want to consider one more detail What happens if I make the blanket thicker?

Thinking about the greenhouse A thought experiment of a simple system. Top of Atmosphere / Edge of Space Let’s think JUST about the infrared radiation Forget about clouds for a while 3) Less energy is up here because it is being held near the surface. It is “cooler” ATMOSPHERE 2) More energy is held down here because of the atmosphere It is “warmer” (infrared or thermal) SURFACE

Thinking about the greenhouse Why does it get cooler up high? Top of Atmosphere / Edge of Space 1) If we add more atmosphere, make it thicker, then 3) The part going to space gets a little smaller It gets cooler still. ATMOSPHERE Remember this when we later look at observations of what has happened? It is part of attribution. 2) The part coming down gets a little larger. It gets warmer still. (infrared or thermal) SURFACE The real problem is complicated by clouds, ozone, ….

Think about that warmer-cooler thing. Addition of greenhouse gas to the atmosphere causes it to get warmer near the surface and colder in the upper atmosphere. This is part of a “fingerprint” of greenhouse gas warming. Compare to other sources of warming, for example, more energy from the Sun.

Think about a couple of details of emission. There is an atmospheric window, through which infrared or thermal radiation goes straight to space. Water vapor window Carbon dioxide window is saturated This does not mean that CO2 is no longer able to absorb. It means that it takes longer to make it to space.

Thinking about the greenhouse Why does it get cooler up high? Top of Atmosphere / Edge of Space 1) Atmospheric Window 2) New greenhouse gases like N20, CFCs, Methane CH4 close windows ATMOSPHERE Remember this when we later look at observations of what has happened? It is part of attribution. 3) Additional CO2 makes the insulation around the window tighter. (infrared or thermal) SURFACE The real problem is complicated by clouds, ozone, ….

So what matters? Changes in the sun THIS IS WHAT WE ARE DOING Things that change reflection Things that change absorption When we think of mitigation of climate change, managing or controlling warming, we really only have two things to think about, things that change absorption and things that change reflection. If something can transport energy DOWN from the surface.

Think about the link to models energy reflected = (fraction of total energy reflected) X (total energy) energy absorbed = total energy - energy reflected = (1-fraction of total energy reflected) X (total energy) fraction of total energy reflected  Clouds Ice Ocean Trees Etc.

Radiation Balance Figure In this figure out = in This is a figure where things are in balance. What goes out = what comes in.

Energy in Earth System: Basics Science  Observations  Evaluation  Measurement Can we do the counting to balance the budget? Can we measure the imbalance when the Earth is not in equilibrium?

Radiative Balance (Trenberth et al Radiative Balance (Trenberth et al. 2009) In this figure out does not = in In this figure what goes out does not equal what goes in: The Earth is warming. The amount of warming is about 1 out of 340

IPCC (2001) projections for the next century http://www.grida.no/publications/other/ipcc_tar/ … Figure SPM-10b: Variations of the Earth’s surface temperature: years 1000 to 2100. From year 1000 to year 1860 variations in average surface temperature of the Northern Hemisphere are shown (corresponding data from the Southern Hemisphere not available) reconstructed from proxy data (tree rings, corals, ice cores, and historical records). The line shows the 50-year average, the grey region the 95% confidence limit in the annual data. From years 1860 to 2000 are shown variations in observations of globally and annually averaged surface temperature from the instrumental record; the line shows the decadal average. From years 2000 to 2100 projections of globally averaged surface temperature are shown for the six illustrative SRES scenarios and IS92a using a model with average climate sensitivity. The grey region marked “several models all SRES envelope” shows the range of results from the full range of 35 SRES scenarios in addition to those from a range of models with different climate sensitivities. The temperature scale is departure from the 1990 value; the scale is different from that used in Figure SPM-2.

IPCC (2007) projections for the next century Figure SPM.5. Solid lines are multi-model global averages of surface warming (relative to 1980–1999) for the scenarios A2, A1B and B1, shown as continuations of the 20th century simulations. Shading denotes the ±1 standard deviation range of individual model annual averages. The orange line is for the experiment where concentrations were held constant at year 2000 values. The grey bars at right indicate the best estimate (solid line within each bar) and the likely range assessed for the six SRES marker scenarios. The assessment of the best estimate and likely ranges in the grey bars includes the AOGCMs in the left part of the figure, as well as results from a hierarchy of independent models and observational constraints. {Figures 10.4 and 10.29}

IPCC (2013) projections for the next three centuries http://www.climatechange2013.org/images/figures/WGI_AR5_Fig12-5.jpg Time series of global annual mean surface air temperature anomalies (relative to 1986–2005) from CMIP5 concentration-driven experiments. Projections are shown for each RCP for the multi-model mean (solid lines) and the 5 to 95% range (±1.64 standard deviation) across the distribution of individual models (shading). Discontinuities at 2100 are due to different numbers of models performing the extension runs beyond the 21st century and have no physical meaning. Only one ensemble member is used from each model and numbers in the figure indicate the number of different models contributing to the different time periods. No ranges are given for the RCP6.0 projections beyond 2100 as only two models are available.

Radiative Forcing Changes Excellent article on history of this figure http://www.realclimate.org/index.php/archives/2013/10/the-evolution-of-radiative-forcing-bar-charts/ Interesting History of This Plot at RealClimate

Questionnaire: Kansas City, AMS, Broadcast Meteorologists, Model Short Course