Climate and Water Resource Case Study

Overview of Climate Change
Greenhouse Effect and Climate Change
What is the world doing about climate change?
Investigating Regional and Local Projected Climate Change
Consequences of Projected Climate Change
Chapter 7 title
Chapter 8 title

Chapter 2 - B3. Greenhouse Effect: Gas Concentration


The current concern about the greenhouse effect and climate stems from the amounts of greenhouse gases that are being released into the atmosphere from the burning of fossil fuels, deforestation, agricultural and industrial practices, release of synthetic chlorofluorocarbons, and other humankind activities.  Accumulation of these heat-absorbing greenhouse gases in the atmosphere can result in an enhanced greenhouse effect and consequent global warming amplified by human activities.  The concern is that an enhanced greenhouse effect may elevate global temperatures above levels that have not occurred for hundreds of thousands of years.  The degree to which the accelerating rate of increase of greenhouse gases in the atmosphere will impact our climate is a topic of much debate and uncertainty because of the many variables that are involved in the climate system and their feedbacks.

Atmospheric Gas Concentration

            So how do we measure the quantity of carbon dioxide in the earth's atmosphere? An important concept in the discussion about greenhouse gases is concentration and it is the way we measure the quantity of gases in the atmosphere. Concentration is simply how much of a particular stuff is in all the stuff. Confused? Well, a simple example would be a mixture of brown and white rice grains. The brown rice concentration would be the number of brown rice grains divided by the total number of rice grains (brown grains plus white grains). Concentration can be given in a variety of units with mass and volume being most popular. A more technical definition is that concentration is calculated by the fraction of the total of a subsubstance made up of one component. Concentrations have a variety of units, but for our purposes one of the most important is parts per "something" where "something" usually is thousands, millions, billions, or trillions. The following abbreviations are used for these units:

ppm = parts per million by weight, mass, or volume

ppb = parts per billion by weight, mass, or volume

ppt = parts per trillion by weight, mass, or volume

Sometimes, there is a "v" that follows - e.g ppmv - which means parts per million by volume.

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