Climate Forecast System

The bare rock model

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...

Band saturation

Co2 Saturation Spectrum

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...

Blackbody radiation

Blackbody Radiation Global Warming

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...

What Effect Does The Ground Temperature Have On The Shape Of The Outgoing Ir Spectrum

Band Saturation Co2 Methane

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...

The land breathes

Carbon Reservoirs

The CO2 in the atmosphere is only the tiniest fraction of the carbon on Earth (Fig. 8.1). There is also carbon stored at the land surface, in the oceans, in sedimentary rocks, and the deep interior of the Earth. These other carbon reservoirs all breathe CO2, causing atmospheric CO2 to vary, naturally, on all sorts of timescales, from one year to millions of years. The atmosphere contains about 700 gigatons of carbon. A gigaton, abbreviated Gton, is a billion (109) metric tons, equivalent to...

Weather versus climate

What Determines Climate Sun

If you don't like the springtime weather in Chicago, just wait a few days. It's a gray 5 C out there now, but the forecast for the weekend puts it up to 15 C, which is a little more like spring. The 10-day forecast says showers the weekend after that, but no one believes the end of a 10-day forecast anyway. They're better than they used to be, but 10 days is still something of a crap shoot. And here I am sitting down to write about forecasting the climate 100 years from now. I suppose some...

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...

So we have to simulate the weather

The upshot of this chapter is that in order to forecast global warming, we will have to simulate the time and space variations and imbalances in the energy budget, and the way that the Earth's climate responds to this forcing by storing or transporting heat around. The layer model will not do. Unfortunately, the physics which governs the flow of air and water is complex and difficult to simulate by its very nature. The difficulty is that fluid flow such as in the atmosphere and the ocean takes...

Climate forcings in the past

The next step is to ask about natural processes that drive the climate, natural climate forcings. Different climate forcings can be compared with each other in terms of their energy impact on the Earth in Watts per square meter. One Watt per square meter in solar output, for example, is roughly equivalent to 1 W m2 of IR light trapped by CO2, or at least these have about the same impact on model climates. We can roughly estimate the climate impact of radiative forcings using another version of...

Water vapor feedback

Water Phase Diagram Mars

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...

Projects

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...

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...

Energy sources

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...

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...

The rocks breathe

Silicate Weathering Climate Change

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...

Climate variations on orbital timescales

Climatic Variations

The glacial cycles are driven by variations in Earth's orbit. Climate reconstructions on these timescales come from ice cores and ocean sediment cores. We looked at an ice core data set in Fig. 8.3 showing concentrations of CO2 and CH4 in the atmosphere, recorded in bubbles in the ice. Figure 8.3c, which we haven't talked about much yet, is a reconstruction of the temperature where the ice accumulated, in Antarctica (not a global average). The temperature estimate is based on the relative...

Dangerous anthropogenic interference

Another way of approaching the problem is to ask, What would it take to avoid dangerous climate change This was how the FCCC was constructed, to prevent dangerous anthropogenic interference with the climate system. IPCC didn't specify what dangerous interference is, leaving that topic to future discussion which is still happening. One way to define dangerous interference is to base it on the range of climate variability that the Earth has experienced in the last million years or so. If we...

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...

Forecasting climate change

The fundamental process that determines the temperature of the Earth is the balance between energy flowing to the Earth from the Sun and energy flowing away from the Earth into space. Heat loss from Earth depends on the Earth's temperature, among other things (Chapter 2). A hotter Earth loses heat faster than a cooler one, all else being equal. The earth balances its energy budget by warming up or cooling down, finding the temperature at which the energy fluxes balance, with outflow equaling...

Carbon energy and climate

Climate change from fossil fuel combustion is arguably the most challenging environmental issue we face because CO2 emission is at the heart of how we produce energy, which is pretty much at the heart of our modern standard of living. The agricultural revolution, which supports a human population of 6 billion people and hopefully more, has at its heart the industrial production of fertilizers, a very energy-intensive process. It's not easy to stop CO2 emission, and countries and companies that...

Fossil fuels and energy

The Sun bathes the Earth in an immense amount of energy, but most of humankind's energy sources derive from stored energy sources such as fossil fuels or radioactive elements rather than instantaneous solar energy. Of the fossil fuels, coal is the most abundant whereas oil is more limited and may be depleted in the coming decades. The amount of natural gas as traditionally extracted is comparable with that of oil, but there is an immense amount of gas frozen in ocean sediments. If we wish to...

Terrestrial biosphere feedbacks

The terrestrial biosphere has the potential to feed back to climate by altering the albedo of the land, and by altering evaporation. Trees have a much lower albedo than does the bare ground. Cooling might lead to the demise of forests, increasing albedo, and driving temperatures down further. Trees also mine ground water and evaporate it from their leaves. The Amazon rain forest is said to perpetuate its own existence by extracting ground water and evaporating it to the air, rather than...

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...

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...

Global warming is a largescale problem

Global warming is a difficult problem to cope with politically because its footprint is so large. It is a global problem, subject to an effect known as the Tragedy of the Commons. An example of this effect is of a field for grazing sheep used in common by all residents of a village. Let's say that each new sheep added to the flock decreases the harvestable weight of each of the other cute little sheep by 10 (Fig. 13.1). A farmer with one sheep can add a second, doubling his number of sheep. But...

Energy through a vacuum

A thermos bottle is designed to slow the flow of heat through its walls. You can put warm stuff in there to keep it warm, or cool stuff to keep it cool. Thermos bottles have two walls an inner and an outer wall. In between the two walls is an insulator. A vacuum is a really good insulator because it has no molecules or atoms of gas in it to conduct heat between the inner and outer walls of the thermos. Of course there will still be heat conduction along the walls. Let's think about a planet....

How a greenhouse gas interacts with earthlight

We have seen that gases are terrible blackbodies because they are very choosy about which frequencies they absorb and emit. What we will now see is that some frequency bands are more important to the climate of the Earth than others. There are two factors to consider. One is the concentration of the gas, which we will discuss below. The other is the frequency of the absorption band relative to the blackbody spectrum for the Earth. Figure 4.3 shows blackbody spectra again for temperatures...

Can You See Evidence For Poleward Migration Of Biome Types

Point your web browser at physics part of the model, temperatures and winds and currents and all that, was described in the Projects section of the last chapter. In addition to that, the run had a land biosphere model, developed at the University of Wisconsin in Madison. Plants on land are described by 16 different biome types, which compete with each other for the land surface. The biomes are listed in Plate 12.5. The run also used a simple groundwater scheme, much simpler than real soils....

The thermometer records

The warming signal we are looking for is small compared with the variations in temperature from day to day, season to season. We want to know whether the planet surface as a whole is getting warmer, so we will have to average out all the weather. It could be treacherously easy for some bias in the raw data to be undetected or otherwise not corrected for. A computed average temperature for some particular place has to be balanced between daytime and nighttime temperature measurements, for...

Default Settings In Kaya Identity Scenario Prognosticator

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...

Greenhouse gases

The layer model assumes that the atmosphere acts as a blackbody in the infrared (IR), absorbing and emitting all frequencies of IR light. In reality, gases absorb IR light selectively, and most of the gases in the atmosphere do not interact with IR light at all. The difference can be understood in terms of the effect of molecular vibration on the electromagnetic field. Because gases absorb IR selectively, there are some radiation bands that are completely absorbed (the gases are saturated), and...

Gases vibrations and light

Most of the mass of an atom is in its nucleus, which resembles the massive Sun at the center of the solar system. Electrons float in ghostly quantum mechanical probability clouds, called orbitals, around the nucleus. The two nuclei of two different atoms always repel each other because of their positive charges. The orbitals for the electrons fit together better, however, with certain numbers of orbitals than with others. The electrons from two different atoms may be able to combine their...

The chemistry of carbon

Carbon has a rich, spectacular, wondrous chemistry. There are more scientists studying the chemistry of carbon than any other element, I am sure. The nearest relative of carbon is the element silicon which is located directly underneath carbon on the periodic table. Silicon is one of the more abundant elements on Earth, and the chemistry of the rocks in the mantle is controlled to a large extent by the whims of silicon. Silicon tossed out into the environment finds its way into hundreds of...

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...