Summary
This is a series of articles on models. In this series, I am trying to develop a way to build a foundation for non-scientists to feel comfortable about models and their use in scientific investigation.
Doing Science with Models 1.7: I have tried to demystify the use of models in science and climate science in several ways. Here is the series of ideas that I have tried to line up.
1) Models are everywhere, and we use them all of the time. I introduced examples of commonly used models such as ledger sheets and building plans. In fact, whenever we are faced with a new problem, we naturally look to models for possible solutions. Most commonly that model is – do I have experience in a previous situation that helps me in this situation? That might be followed with – do I have friends who have relevant experience? Can I hire expertise? When we are faced with no experience of a situation; that is, we have no model, then we are thrown into a situation where we might have difficulty understanding impacts, risks, and what to do. Whether or not we explicitly recognize it, models are part of human thinking and problem solving. (Models are Everywhere, Ledgers, Graphics, and Carvings)
2) The arithmetic that we use to figure out how much money we have, the budget equation, is a model.
Today’s Money = Yesterday’s Money + Money Gained – Money Spent
Some of the models that we use are mathematical and provide us with a way to quantify things that are important to us. (Balancing the Budget)
3) We have become comfortable with coding models on computers. With the spread of computers in the past 20 years, we, for example, use computers to balance our checkbooks and plan our budgets. We enter numbers and words into forms and press some buttons, and seconds later, we have categorized accounting of our income and expenses. (Ledgers, Graphics, and Carvings)
4) The same form of the budget equation that we use to balance our checkbook can be used to make an accounting of the energy of the Earth.
Today’s Energy = Yesterday’s Energy + Energy Gained – Energy Lost.
Therefore, if we can measure energy, sources of energy, and loses of energy, we can make a quantitative accounting. (Balancing the Budget)
5) Point of view is important. The accounting of the Earth’s energy, hence a description of the climate, depends on your point of view. If you were sitting on Mars, then you might only be interested in the energy that comes to and leaves the Earth. If you are a person on the surface of the Earth, you need to know the energy in the atmosphere, the land, the ocean, and the ice. Therefore you need budget equations for each of these components of the Earth’s climate. This is like having several energy accounts. The transfers between accounts appear as exchanges: loses to one account and gains to others. (Point of View)
6) Complexity arises because there are many energy accounts and many ways to transfer energy from one account to another. Even though every energy exchange might be simple, when we put all of the exchanges together the total system is complex. Energy might collect in one place, for example evaporated water in the tropical atmosphere, and it might be lost and deposited some place else, for example ice sheets in Greenland. There is the possibility of transfer of large amounts of energy between these collections of energy. (Looking Under the Cloak of Complexity)
7) The Earth’s climate is constrained by the processes that govern the transfer of energy from one account to another. Well-known rules, or laws, govern the way that energy is transferred. They are strictly and precisely defined. The Earth’s climate can be quantified by accounting for the energy. Because of the laws that govern energy transfer, we can in principle make credible estimates of the Earth’s climate in the future. (The Free Market and the Climate Model)
8) It takes time for energy to move around to the different energy accounts. For example, a lot of energy can be stored in the ocean for long periods of time. Long? Compared to what? Long compared to the atmosphere and perhaps compared to the life times of humans. Ice sheets have had life times of hundreds of thousands of years, and they represent the accumulation of many years of energy transport. (Looking Under the Cloak of Complexity)
If we use this framework to think about climate, climate models, and climate change, then when we add carbon dioxide to the atmosphere what are we changing? From the point of view of the human on the surface of the Earth, we are changing the amount of time that the energy from the Sun is stored near the surface of the Earth. Some of this energy shows up as an increase in temperature at the surface. Some warms the ocean. Some changes the water budget and the weather. Ultimately, some makes it way back to outer space, but not until after it causes a set of changes important to the person on the surface of the Earth.