The Atmosphere and The Oceans
ice shelf splits
|Origin of the Earth's Atmosphere|
of atmospheric oxygen
Free oxygen is never more than a trace component of most planetary atmospheres. Thermodynamically, oxygen is much happier when combined with other elements as oxides; the pressure of O2 in equilibrium with basaltic magmas is only about a ten millionth of an atmosphere. Photochemical decomposition of gaseous oxides in the upper atmosphere is the major source of O2 on most planets. On Venus, for example, CO2 is broken down into CO and O2. On the earth, the major inorganic source of O2 is the photolysis of water vapor; most of the resulting hydrogen escapes into space, allowing the O2 concentration to build up. An estimated 20 billion grams of O2 per year is generated in this way. Integrated over the earth’s history, this amounts to less than 3% of the present oxygen abundance. The partial pressure of O2 in the prebiotic atmosphere is estimated to be no more than 0.001 atm, and may have been several orders of magnitude less. The major source of atmospheric oxygen on the earth is photosynthesis carried out by green plants and certain bacteria:
Cells that Rule the Seas
|The Invisible Forest|
cytometry is the measurement (meter)
of characteristics of single cells (cyto) suspended in a
flowing saline stream. A focussed beam of laser light hits
the moving cell and light is scattered in all directions.
Detectors placed forward of the intersection point or side-on
(with respect to the laser beam) receive the pulses of scattered
light and they are converted into a form suitable for computer
analysis and interpretation. The total amount of forward
scattered light detected is closely correlated with cell
size, whereas the amount of side scattered light can indicate
nuclear shape or cellular granularity.
Exxon rep: CO2 output to rise 50 percent by 2020 from Tim Nau
|Structure of the Atmosphere|
In large measure, the atmosphere has evolved in response to and controlled by life processes. It continues to change as a consequence of human activities, but at a rate that is far in excess of the rate of previous evolutionary change. The atmosphere controls the climate and ultimately determines the quality of life on Earth.
gases in the atmosphere that help retain heat are called
greenhouse gases. These gases, primarily carbon dioxide
(CO2), absorb heat instead of allowing it to escape into
space. This "greenhouse
effect" makes the planet a hospitable
place. However, greenhouse
gases can have negative effects, too. Human
activity has increased the amount of CO2 in the atmosphere.
Since the 1800s, industrialized societies have burned fossil fuels such as coal, oil, and natural gas; these processes all give off CO2. During the past 25 years, the amount of CO2 in the atmosphere has increased by about 8 percent. With more CO2 in the atmosphere, more heat is absorbed and retained, causing global temperatures to rise. Some scientists project that by the next century, CO2 levels in the atmosphere could be twice what they are today, causing a global temperature increase of about 3 degrees. Three degrees may not seem like much, but even a few degrees can have serious consequences. Tropical diseases could increase, since mosquitoes and other disease-carrying insects thrive in a warmer climate. Sea levels could rise, and coastal cities such as New Orleans and Washington, D.C., could be battered by storm surges. Prosperous farmland could dry up and agricultural regions could shift, wreaking havoc on the global economy.
|It is possible that the recent warming trend is due more to natural cycles of cooling and warming than to human activity. Global climate change occurs on a scale of tens or hundreds of thousands of years, but scientists have only begun to study these effects in the last 150 years. Still, most scientists agree that just as climate affects our lives, we can affect the climate. Just how much we can influence it remains to be seen.|
|The climatic effects of water vapour|
by Ahilleas Maurellis and Jonathon Tennyson
The Earth Radiation Budget Experiment (ERBE)
. . .but, I thought it was the CO2 that was the culprit?