Climate Change

Source:  NASA

Those discussing “Climate Change” are talking about long-term changes in weather patterns. “Weather” happens over the short-term. “Climate” is generally considered to be weather averaged over a minimum of 30 years.

The global warming issue is about long-term, difficult-to-reverse, worldwide climate change. The high quality and large quantity of data available, the extensive time period from which it's been collected (650,000 years including data from ice field cores) and the existence of recent, in-depth studies by respected organizations have offered persuasive arguments that global warming is taking place and that the process may be accelerating.

Debates over how quickly and drastically world climate is changing are easy to find and questions about the extent to which human activities contribute either remain, or have answers which are disputed. If opinions were remedies we’d no longer have a problem.

The EARTH'S ENERGY BALANCE

The earth maintains a balance between incoming solar radiation and outgoing radiation. It’s this balance which determines temperatures on the surface of the earth. This is a short description of that process…

Shortwave radiation (think of it as heat) from the sun shines upon the earth.

1. 35% of the sunlight hitting the earth’s atmosphere is reflected back into space by clouds, aerosols (small particles floating in the air) and light-colored land features such as ice, snow and deserts.

2. About 50% of the original solar radiation is absorbed by the earth and oceans.

3. The earth’s surface also radiates heat, but because the earth is colder than the sun, this heat is in the form of longwave radiation. Everything on earth emits longwave radiation.

1. If over the long-term the earth radiates more heat than it absorbs, it becomes increasingly colder.
2. If the earth absorbs more heat than it radiates, it becomes warmer.
3. To remain in balance and maintain a steady temperature, the earth’s outgoing radiation must equal the incoming radiation.

Source: NASA

The GREENHOUSE EFFECT

Greenhouse gases in the atmosphere absorb radiation (heat) which has been reflected by or radiated from the earth and radiate it back to the earth, warming the earth’s surface. Without this process, the temperature of the earth would be below the freezing point of water, so the greenhouse effect is a natural, necessary process. Greenhouse gases are produced naturally in addition to being produced by humans.

GREENHOUSE GASES

Water Vapor

Water vapor is by far the most important greenhouse gas, creating approximately 95% of the greenhouse effect. Almost all water vapor is produced through natural processes. Although many studies and sources of information choose to not include water vapor when listing greenhouse gases, this omission results in misrepresentation of global conditions. 

In the warm equatorial regions which already have large amounts of water vapor in the air, the relatively small amounts of human-produced greenhouse gases have little effect. In the cold, dry polar regions, the effects of human-produced greenhouse gases are much greater. As the greenhouse effect has grown stronger, polar ice caps have begun to melt and recede, exposing dark land which absorbs heat and speeds the melting process. 

Carbon Dioxide

Carbon Dioxide (CO₂) is the second most important greenhouse gas, much of which is produced by human actions. In 2004, humans put over 27 billion metric tons of carbon dioxide into the atmosphere. That number grows larger each year and  is absorbed not only by the atmosphere, but by the oceans and the biosphere.

Stored in these various manners, it has no overall, single, specific lifespan, so the amount of time required for CO₂ to dissipate naturally is difficult to pinpoint. Roughly 50% is now removed within a century and 20% will take many thousands of years. A considerable lag time exists between the reduction of CO₂ emissions and a reduction of levels in the atmosphere. Once it’s produced, it lasts a long, long time.

Although CO₂ represents only 4% of greenhouse gases in the atmosphere, the concern lies in the vast amounts accumulating in the atmosphere, oceans and biosphere. The tables below show how atmospheric levels reflect emissions.

                                        Source: Oak Ridge National Laboratories                                                              Source

Trends in Atmospheric Human-produced Carbon Dioxide Emissions and Concentrations

75% of human-produced CO₂ is introduced into the atmosphere by the burning of fossil fuels. The remaining 25% is the result of forest-clearing and burning of plant products for fuel.   

The Greenhouse Gases

The two most abundant gases on earth- nitrogen and oxygen- make no contribution to the greenhouse effect.

Long-lived gases such as carbon dioxide, methane and nitrous oxide are chemically stable and remain in the atmosphere for decades or centuries.

Short-lived gases such as sulphur dioxide and carbon monoxide are chemically reactive and are more quickly removed by natural oxidation and precipitation.

Source

This chart shows one study of the percentage each greenhouse gas contributes to the total greenhouse effect

 Burning 1 gallon of gasoline weighing 7 lbs. puts 19.6 lbs. of CO₂ into the air. learn how!

The Carbon Dioxide Information Analysis Center (CDIAC) is the primary climate-change data and information analysis center of the U.S. Department of Energy (DOE).  They have an excellent  Frequently Asked Questions page.