Energy sources
Our civilization is based on energy. We will express global energy fluxes in units of terawatts. A Watt is a flux of energy flow, equal to Joule per second, where Joule is a unit of energy like calories. A hair dryer might use 1000 W of power, or 1 kilowatt, kW. A terawatt is 1012 W, and is abbreviated as TW. The Sun bathes the Earth in energy at a rate of about 173,000 TW. Photosynthesis captures about 100 TW. Mankind is consuming about 13 TW of energy per year. Some of our 13 TW of energy use...
Convection in the layer model
The layer model that we constructed in Chapter 3 did not have convection. Think about a layer model with multiple atmospheric layers, such as one constructed in Project 2 in Chapter 3. The temperatures of the layers decrease with altitude, just like the real atmosphere does, but the only way that heat is carried between the layers in the layer model is by blackbody radiation. One could construct a model with a continuous atmosphere, with temperature varying smoothly with altitude like the real...
Projects Cru
1. Compound interest. The formula to compute compound interest for a bank account is Balance t Balance initial ek't This was first presented in Chapter 5 when we met the exponential function ex. Assuming an interest rate of 3 per year, how much would an investment of 1.00 made today be worth in the year 2100 What if the interest rate were 5 per year 2. AT2x. The formula to estimate temperature response to changing CO2 concentration is This formula was first introduced in Chapter 4. Calculate...
Convection
Now we are ready to weave our seeming disparate threads of story together into a picture of what controls the temperature as a function of altitude in the atmosphere. The pieces are assembled into a process called convection. Convection takes its place among conduction and radiation, which we have already discussed, as a means of carrying heat in the environment. Convection occurs when a fluid medium is heated from the bottom or cooled from the top, and the heavy water atop light water causes...
Online models
A model of infrared radiation in the atmosphere A model of visible infrared radiation in the atmosphere A model of the geological carbon cycle ISAM Integrated assessment model for future climate change The Kaya Identity model for the growth of the human footprint Browsing the results of a coupled climate model
Blackbody radiation 1
So where can we see electrical energy traveling the other way, from matter into light One example a red hot electric burner shines light you can see. The light derives its energy from the vibrations or thermal energy of the matter. We normally don't think of it, but it turns out that your electric burner continues to shine even when the stove is at room temperature. The difference is that the room temperature stove emits light in colors that we can't see, down in the IR range. If we imagine our...
Alternatives
One obvious possibility is conservation. The United States uses twice the energy per person as is used in Europe or Japan Fig. 9.11 . In part this is because the human terrain of the United States developed in a more automotive way, whereas public transit and trains are better developed in Europe and Japan. In addition, Americans drive larger cars and live in larger houses. I personally enjoy life in Europe. I would far prefer to take a train to work, in which I can read or watch people, rather...
Projects Gai
1. The orbit and seasons. Answer this question using an online model of the intensity of sunlight as a function of latitude and season at http understandingtheforecast.org Projects orbit.html. The model calculates the distribution of solar heating with latitude and season depending on the orbital parameters of the Earth. Enter a year ad and push calculate. The eccentricity is the extent to which the orbit is out of round an eccentricity of zero would be a fully circular orbit. Obliquity is the...
Adiabatic expansion
Here begins the second apparently unrelated thread of our story. If we compress a gas, its temperature goes up. This occurs even if we don't allow any heat to enter the gas or leave it, say if we had gas inside an insulated piston that we compress or expand. The condition that we are describing, a closed system with no heat coming in or out, is called adiabatic. If gas is compressed adiabatically, it warms up. If you ever let the air out of a bicycle tire by holding the little valve open with...
Pressure as a function of altitude
Gases and liquids exert pressure on the surfaces of solids that are immersed in them, simply the force of the atoms bouncing off of the solid surface. The pressure gets lower as you climb higher in the atmosphere. As we ascend, we decrease the amount of fluid that is above us, decreasing the pressure that we feel. Scuba divers know that diving 10 m deep increases the pressure by about 1 atm. Each 10 m of depth is the same 1 atm pressure increase descending from 30 to 40 m would increase the...
The ocean breathes
The ocean carbon reservoir is larger than either the land surface or the atmosphere. The ocean's carbon is not only dead, but it is also oxidized energetically dead as well as biologically dead. The carbon is in the forms CO2, H2CO3, HCO-, and CO , all of which we will get to know better in Chapter 10. The sum of all of them is called dissolved inorganic carbon. The ocean dissolved inorganic carbon pool is larger than the atmospheric pool by a factor of about 50. There is also dissolved organic...
Projects Bzb
Answer these questions using the full-spectrum radiation model at http understanding 1. Compare two codes. You will find that the two radiation codes give very different answers for the temperature sensitivity to CO2 and water vapor. What is the AT2x for each model Is it the same for doubling from 100 to 200 ppm as it is for 350 to 700 ppm The model includes the water vapor feedback automatically, but we can turn this off by zeroing the relative humidity. What is the AT2x without the water...
Projects Iui
1. Lapse Rate. Use the online full-spectrum radiation model at Adjust the lapse rate in the model and document its impact on the equilibrium temperature of the ground. 2. Skin Altitude. Answer this question using the online IR radiation model. a. Run the model in some configuration without clouds and with present-day pCO2. Compute a T4 using the ground temperature to estimate the heat flux that you would get if there were no atmosphere. The value of a is 5.67 10 8 W m2 K4. Is the model heat...
What Effect Does The Ground Temperature Have On The Shape Of The Outgoing Ir
Answer these questions using the online model at http understandingtheforecast.org Projects infrared_spectrum.html. The model takes CO2 concentration and other environmental variables as input, and calculates the outgoing IR light spectrum to space, similarly to Figs. 4.3,4.5, and 4.8. The total energy flux from all IR light is listed as part of the model output, and was used to construct Fig. 4.6. 1. Methane. Methane has a current concentration of 1.7 ppm in the atmosphere, and it's doubling...
Water vapor feedback
Water vapor is responsible for more greenhouse heat trapping on Earth than CO2 is, and yet your impression is that global warming is primarily about CO2, not water vapor. Fig. 7.2 A phase diagram for water demonstrating that the water vapor feedback on Earth and Mars is limited, while Venus is free to have a runaway greenhouse effect. Fig. 7.2 A phase diagram for water demonstrating that the water vapor feedback on Earth and Mars is limited, while Venus is free to have a runaway greenhouse...
Lapse rate and the greenhouse effect
The steeper the lapse rate, the stronger the greenhouse effect. If the atmosphere were incompressible like water, and convection maintained a uniform temperature with Fig. 5.10 The layer model from Chapter 3 as it might look if we were to include convection. Convection carries heat vertically in the atmosphere, supplementing the heat carried by radiation. If we were to add convection to the layer model, it would require a few new arrows. Fig. 5.10 The layer model from Chapter 3 as it might look...
Glaciers
The most visual indication of climate change is the melting of mountain glaciers. The vast majority of the mountain glaciers of the world are melting back at astonishing rates Fig. 11.4 . This is happening all over the world. Figure 11.5 shows records of shortening of 20 glaciers around the world. Many of the glaciers have been melting back since the 1700s as a result of natural warming since the Little Ice Age. However, melting has accelerated in the past decades. The Snows of Kilimanjaro see...
The bare rock model
The temperature of the surface of the Earth is controlled by the ways that energy comes in from the Sun and shines back out to space as IR. The Sun shines a lot of light because the temperature at the visible surface of the Sun is high and therefore the energy flux I sa T4 is a large number. Sunlight strikes the Earth and deposits some of its energy into the form of vibrations and other bouncings around of the molecules of the Earth. Neither the Earth nor the Sun is a perfect blackbody, but...
Projects 1
1. The moon with no heat transport. The layer model assumes that the temperature of the body in space is all the same. This isn't really very accurate, as you know that it's colder at the poles than it is at the equator. For a bare rock with no atmosphere or ocean, like the Moon, the situation is even worse, because fluids like air and water are how heat is carried around on the planet. So let's make the other extreme assumption, that there is no heat transport on a bare rock like the Moon....
The rocks breathe
The sedimentary rock carbon pool is larger still than the ocean, land, or atmospheric pools. Carbon exists in the form of limestones, CaCO3, and to a lesser extent as organic carbon. These carbon reservoirs together contain about 500 times as much carbon as the atmosphere and the landscape combined. Most of the organic carbon in sedimentary rocks is in a form called kerogen. Kerogen is useless as a fossil fuel because it is dilute, usually less than 1 by weight of sedimentary rocks, and because...
Band saturation
The core of the CO2 bend absorption band, between 600 and 800 cycles cm, looks smooth rather than jagged and it follows a blackbody spectrum from about 220 K. This is about as cold as the atmosphere gets, and if we change the amount of CO2 in the atmosphere, the intensity of light in this range does not get any lower Fig. 4.5 . We call this phenomenon band saturation. You can see it in a series of model runs in which the CO2 concentration of the atmosphere goes up from 0 to 1000 ppm. The...
Ice albedo feedback
The ice albedo feedback is a positive one that operates mostly in the high latitudes because that is where the ice is. According to our current climate models, global temperature changes will be amplified in the high latitudes, by a factor of about 2 or 4 over global average warming. Climate change today is much more obvious in high latitudes, as in melting of permafrost in Alaska and Siberia and melting of sea ice in the Arctic, than it is in other places like the tropics, for this reason. In...
Methane
Methane is a greenhouse gas, 20 times more powerful per molecule than CO2 at current concentrations see Chapter 4 . Methane has natural sources as well as additional anthropogenic sources to the atmosphere Table 10.1 . Once released into the atmosphere, methane reacts slowly with activated oxygen compounds to oxidize back to CO2. The reactive oxygen compounds are produced by sunlight. In the absence of sunlight methane and O2 gas coexist in ice core bubbles for hundreds of thousands of years...
Water vapor and latent heat
Here comes seemingly unrelated thread number three. Water molecules can exist together in any of three phases gas, liquid, or solid. A transformation from liquid or solid to gas requires an input of a considerable amount of energy. One could write a chemical reaction for water as If you have ever burned your skin with steam from a teapot, this reaction will have meaning for you. Steam from a teapot is probably at the boiling temperature of water, 373 K. This is a temperature you might set for...