Although the exact causes for ice ages, and the glacial cycles within them, have not been proven, they are most likely the result of a complicated dynamic interaction between such things as solar output, distance of the Earth from the sun, position and height of the continents, ocean circulation, and the composition of the atmosphere.
Between 52 and 57 million years ago, the Earth was relatively warm. Tropical conditions actually extended all the way into the mid-latitudes (around northern Spain or the central United States for example), polar regions experienced temperate climates, and the difference in temperature between the equator and pole was much smaller than it is today. Indeed it was so warm that trees grew in both the Arctic and Antarctic, and alligators lived in Ellesmere Island at 78 degrees North.

But this warm period, called the Eocene, was followed by a long cooling trend. Between 52 and 36 million years ago, ice caps developed in East Antarctica, reaching down to sea level in some places. Close to Antarctica, the temperature of the water near the surface dropped to between 5 and 8 degrees Celsius. Between 36 and 20 million years ago the earth experienced the first of three major cooling steps. At this time a continental-scale temperate ice sheet emerged in East Antarctica. Meanwhile, in North America, the mean annual air temperature dropped by approximately 12 degrees Celsius.

Between 20 and 16 million years ago, there was a brief respite from the big chill, but this was followed by a second major cooling period so intense that by 7 million years ago southeastern Greenland was completely covered with glaciers, and by 5-6 million years ago, the glaciers were creeping into Scandinavia and the northern Pacific region. The Earth was once more released from the grip of the big chill between 5 and 3 million years ago, when the sea was much warmer around North America and the Antarctic than it is today. Warm-weather plants grew in Northern Europe where today they cannot survive, and trees grew in Iceland, Greenland, and Canada as far north as 82 degrees North.

We are still in the midst of the third major cooling period that began around 3 million years ago, and its effect can be seen around the world, perhaps even in the development of our own species. Around 2 and a half million years ago, tundra-like conditions took over north-central Europe. Soon thereafter, the once-humid environment of Central China was replaced by harsh continental steppe. And in sub-Saharan Africa, arid and open grasslands expanded, replacing more wooded, wetter environments. Many paleontologists believe that this environmental change is linked to the evolution of humankind.
Climate change on ultra-long time scales (tens of millions of years) are more than likely connected to plate tectonics. Plate motions lead to cycles of ocean basin growth and destruction, known as Wilson cycles, involving continental rifting, seafloor-spreading, subduction, and collision.
Changes in the concentration of carbon dioxide in the atmosphere are a strong candidate to explain the overall pattern of climatic change. Carbon dioxide influences the mean global temperature through the greenhouse effect. The globally averaged surface temperature for the Earth is approximately 15 degrees Celsius, and this is due largely to the greenhouse effect. Solar radiation entering earth’s atmosphere is predominantly short wave, while heat radiated from the Earth’s surface is long wave. Water vapor, carbon dioxide, methane, and other trace gases in the Earth’s atmosphere absorb this long wave radiation. Because the Earth does not allow this long wave radiation to leave, the solar energy is trapped and the net effect is to warm the Earth. If not for the presence of an atmosphere, the surface temperature on earth would be well below the freezing point of water.

Through a million year period, the average amount of carbon dioxide in the atmosphere is affected by four fluxes: flux of carbon due to (1) metamorphic degassing, (2) weathering of organic carbon, (3) weathering of silicates, (4) burial of organic carbon. Degassing reactions associated with volcanic activity and the combining of organic carbon with oxygen release carbon dioxide into the atmosphere. Conversely, the burial of organic matter removes carbon dioxide from the atmosphere.

Plate collisions disrupt these carbon fluxes in a variety of ways, some tending to elevate and some tending to lower the atmospheric carbon dioxide level. It has been suggested that the Eocene, the early warm trend 55 million years ago, was caused by elevated atmospheric carbon dioxide and that a subsequent decrease in atmospheric carbon dioxide led to the cooling trend over the past 52 million years. One mechanism proposed as a cause of this decrease in carbon dioxide is that mountain uplift lead to enhanced weathering of silicate rocks, and thus removal of carbon dioxide from the atmosphere.

The earth is transitioning into a rapid period of increase in carbon dioxide on the scale of much slower geological increases in the past. This is also correlating to a rapid increase in global warming temperature, seen in the warmer periods of the Eocene, but at a much faster and alarming rate due primarily to the activities of man. This is a factor nature never had to deal with before.

A map of early warning signs clearly illustrates the global nature of climate changes. In its 2001 assessment, the Intergovernmental Panel on Climate Change (IPCC) concluded that, an increasing body of observations gives a collective picture of a warming world and other changes in the climate system.”
While North America and Europe—where the science is strongest—exhibit the highest density of indicators, scientists have made a great effort in recent years to document the early impacts of global warming on other continents. Our map update reflects this emerging knowledge from all parts of the world.
Although factors other than climate may have intensified the severity of some of the events on the map, scientists predict such problems will increase if emissions of heat-trapping gases are not brought under control.
On Feb. 2, 2007, the United Nations scientific panel studying climate change declared that the evidence of a warming trend is “unequivocal,” and that human activity has “very likely” been the driving force in that change over the last 50 years. The last report by the group, the Intergovernmental Panel on Climate Change, in 2001, had found that humanity had “likely” played a role.
The addition of that single word “very” did more than reflect mounting scientific evidence that the release of carbon dioxide and other heat-trapping gases from smokestacks, tailpipes and burning forests has played a central role in raising the average surface temperature of the earth by more than 1 degree Fahrenheit since 1900. It also added new momentum to a debate that now seems centered less over whether humans are warming the planet, but instead over what to do about it. In recent months, business groups have banded together to make unprecedented calls for federal regulation of greenhouse gases. The subject had a red-carpet moment when former Vice President Al Gore’s documentary, “An Inconvenient Truth,” was awarded an Oscar; and the Supreme Court made its first global warming-related decision, ruling 5 to 4 that the Environmental Protection Agency had not justified its position that it was not authorized to regulate carbon dioxide.

Forests represent a third of the earth’s land. This number is rapidly declining in recent years. On average they can support 200 trees per acre. 9.8 billion acres of forest in the world. (1995 estimate)

9,800,000,000 acres of forest X 200 trees/acre = 1,960,000,000,000 trees. Nurseries in the US replace 1.5 billion per year of these 1,960 billion trees.
Tropical rainforests cover about 6% of the Earth’s total land surface area.
Rainforests are disappearing at about 80 acres (16,000 trees) per minute, day and night or a loss of 8,409,600,000 or 8.5 billion per year. These forests are cut down due to land development at a rate 8 times faster than the total number of nurseries in the US can replace.

The earth’s trees if all logged or destroyed at this rate would disappear in 122500000 minutes, 204166 hours, 85069 days, or 233 years. Since trees provide about 1/3-1/2 of the earth’s oxygen, that would make the oxygen level around 10-14% in the year 2240. At Mount Everest Base Camp (5300m), we are exposed to about half as much oxygen as at sea level. At the summit, each breath contains about one third the oxygen at sea level and we are barely able to survive, and only then for a brief period of time. Above 21,000 feet (7000m) the body consumes itself from lack of oxygen and will not survive long.

We could barely survive in 2240 if we maintain a development rate to develop land to the extent we destroy the forests and replace it with pavement.

I wish some people would just do some very basic research before they make conclusions with no thought process other than they heard it from some liberal or conservative talk show or congressman or political activist committee.

Global warming: lets start with oxygen. It’s 21%. Has it changed in the last few hundred years from the last few thousand?

Oxygenic photosynthesis arose long before O2 became abundant in the atmosphere. Fossil evidence of cyanobacterial ecosystems appeared before 3.0 billion years ago. Sulfates (at 3.4 billion) and oxidation of organic matter (3.0 billion) indicate that O2 was present locally around photosynthetic ecosystems. Atmospheric O2 levels rose substantially between 2.2 and 2.07 billion years. Oxygen-sensitive detrital minerals (FeS2, UO2) disappeared, iron was retained as Fe3+ in soils, and redbeds and O2-requiring eukaryotes arose. Banded iron formations, Fe2+-rich finely-laminated deposits, disappeared by about 1.8 billion years, indicating that O2 had finally permeated the deep oceans.
The history of O2 increases reflects planetary and biological change. Sources of O2 strengthened. Oxygenic photosynthesis evolved; cyanobacteria proliferated over widening continental shelves; and plankton arose. Stabilized continents enhanced the preservation of photosynthetic organic carbon. Sinks of O2 weakened, as fluxes of reduced volcanic species (H2, Fe2+, sulfides, etc.) decreased.
Earth’s history offers insights for a survey of extrasolar planets. Life arose very early and depended upon reduced volcanic emanations. Even after oxygenic photosynthesis arose, perhaps 1 billion years or more passed before O2 became a substantial atmospheric constituent. A dependable O2 supply was essential for the development of complex (plants and animals) and intelligent life.
Oxygen levels have since continued to more-or-less rise, peaking at 30% of the total atmospheric content during the Carboniferous era some 350 million years ago. During this time, the burial rate of organic matter was rapid, preventing oxygen from combining with carbon in dead organisms and keeping it in the atmosphere. The high availability of oxygen during this period may explain the enormous insects of the Carboniferous era; if more oxygen is available to the absorbed into the blood, the blood may deliver the oxygen further in the body, supporting larger body structures.
The world nearly suffocated about 250 million years ago, according to a new study of oxygen levels drawn from sediments laid down around the time of the biggest mass extinction in Earth’s history.
Not only did plummeting oxygen levels over a 20 million-year span directly contribute to an event called the “Great Dying,” but the changes also made most dry land above sea level uninhabitable for many animals and plants for millions of years.
“Oxygen dropped from its highest level to its lowest level ever (during the time Earth has supported life) in only 20 million years, which is quite rapid, and animals that once were able to cross mountain passes easily suddenly had their movements severely restricted,” said Raymond Huey, a University of Washington biology professor and co-author of the report. It was published yesterday in the journal Science.
Scientists calculate that 90 percent of all marine life and three-quarters of all land plants and animals became extinct during the episode of low oxygen, greenhouse conditions and lowered sea levels at the boundary of the Permian and Triassic geological periods.
Huey and co-author Peter Ward, a paleontologist at the university who specializes in extinction events, say that global warming, triggered by massive volcanic activity and a lower sea level, was the biggest contributor to the Great Dying.

Half of the world’s oxygen is produced via phytoplankton photosynthesis. In the process of photosynthesis, phytoplankton release oxygen into the water. The other half is produced via photosynthesis on land by trees, shrubs, grasses, and other plants.

More than 320 million large trees were destroyed when Hurricane Katrina ripped through the Gulf Coast region in 2005, releasing some 105 million tons of carbon - almost the same amount as all the forests in the United States are able to draw down in a year.
The discovery was made by a team of scientists from Tulane University in New Orleans and the University of New Hampshire in Durham.
Satellite observations are the best way to make routine global maps of Earth’s tree-covered landscapes. Led by ecologist Matt Hansen, scientists from the University of Maryland recently created a global tree cover data set from roughly a year’s worth of observations collected by NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. The team used the satellite data to map tree cover at a spatial resolution (detail) of 500 meters by 500 meters. In shades of white (no tree cover) to deep green (100 percent tree cover), forest cover over the region clearly varies widely both from natural and human factors. Along the eastern seaboard, what was once a vast uninterrupted forest is now punctuated by several areas of low tree cover, showing the location of some of the U.S.’s most densely populated and developed regions. The most obvious location is halfway down the east coast, where the cities of New York, New Jersey, Maryland, and Virginia, as well as the nation’s capital, have created a “clearing” in the continent’s original forest. The low tree cover in the central part of the continent is now a mixture of remnant prairies and agricultural lands.
In the bottom image, the tree-cover is influenced by natural topographic and climatic factors as well as human land use. The large area at right that harbors no trees is part of the West’s arid Great Basin, which dominates most of Nevada. The Great Basin is in the “rain shadow” of the mountain ranges to the west. When moisture-laden air rises up over the mountains, condensation occurs, releasing much of the potential rain before the air ever reaches the Basin, preventing trees from growing there. Human influence is visible surrounding Mt. Shasta, where the forest appears patchy, probably due to development and logging. Shasta’s altitude—4,316 meters— puts the summit well above treeline.

Global warming: lets start with the oxygen loss problem. It’s at 21%. Has it changed in the last few hundred years from the last few thousand? Yes

http://www.learner.org/channel/courses/envsci/visual/visual.php?shortname=oxygen_levels

Oxygenic photosynthesis arose long before O2 became abundant in the atmosphere. Fossil evidence of cyanobacterial ecosystems appeared before 3.0 billion years ago. Sulfates (at 3.4 billion) and oxidation of organic matter (3.0 billion) indicate that O2 was present locally around photosynthetic ecosystems. Atmospheric O2 levels rose substantially between 2.2 and 2.07 billion years. Oxygen-sensitive detrital minerals (FeS2, UO2) disappeared, iron was retained as Fe3+ in soils, and redbeds and O2-requiring eukaryotes arose. Banded iron formations, Fe2+-rich finely-laminated deposits, disappeared by about 1.8 billion years, indicating that O2 had finally permeated the deep oceans.
The history of O2 increases reflects planetary and biological change. Sources of O2 strengthened. Oxygenic photosynthesis evolved; cyanobacteria proliferated over widening continental shelves; and plankton arose. Stabilized continents enhanced the preservation of photosynthetic organic carbon. Sinks of O2 weakened, as fluxes of reduced volcanic species (H2, Fe2+, sulfides, etc.) decreased.
Earth’s history offers insights for a survey of extrasolar planets. Life arose very early and depended upon reduced volcanic emanations. Even after oxygenic photosynthesis arose, perhaps 1 billion years or more passed before O2 became a substantial atmospheric constituent. A dependable O2 supply was essential for the development of complex (plants and animals) and intelligent life.
Oxygen levels have since continued to more-or-less rise, peaking at 30% of the total atmospheric content during the Carboniferous era some 350 million years ago. During this time, the burial rate of organic matter was rapid, preventing oxygen from combining with carbon in dead organisms and keeping it in the atmosphere. The high availability of oxygen during this period may explain the enormous insects of the Carboniferous era; if more oxygen is available to the absorbed into the blood, the blood may deliver the oxygen further in the body, supporting larger body structures.
The world nearly suffocated about 250 million years ago, according to a new study of oxygen levels drawn from sediments laid down around the time of the biggest mass extinction in Earth’s history.
Not only did plummeting oxygen levels over a 20 million-year span directly contribute to an event called the “Great Dying,” but the changes also made most dry land above sea level uninhabitable for many animals and plants for millions of years.
“Oxygen dropped from its highest level to its lowest level ever (during the time Earth has supported life) in only 20 million years, which is quite rapid, and animals that once were able to cross mountain passes easily suddenly had their movements severely restricted,” said Raymond Huey, a University of Washington biology professor and co-author of the report. It was published yesterday in the journal Science.
Scientists calculate that 90 percent of all marine life and three-quarters of all land plants and animals became extinct during the episode of low oxygen, greenhouse conditions and lowered sea levels at the boundary of the Permian and Triassic geological periods.
Huey and co-author Peter Ward, a paleontologist at the university who specializes in extinction events, say that global warming, triggered by massive volcanic activity and a lower sea level, was the biggest contributor to the Great Dying.

The illegal invasion can only be understood by the corrupting influence on politicians of money for cheap labor for the Republicans or the Welfare votes for the Democrats that makes them dishonor their Oath of Office, the US Constitution against Invasion, and Enforcement of our Immigration Laws!

I guess pot stirring is a good aerobic exercise; you must have forearms like Popeye.

Thanks for the answer, I thought you were going to chicken out on me.

I don’t give a hoot what type of plane Al Gore flies and I’m sure that a person with hundreds of speaking engagements a year may have a bit of a hard time always flying American Airlines? (Ahem)
What is more important is that the focus is on the environment and if you are waiting for a Jesus to come and do the job or some saintly figure, who would not use a private jet or reside in a small abode you may have to wait a long time. As far as Greenpeace or the Sierra Club you are proposing that the only reason for these organizations to operate is for lucre. That is sad indeed. The Sierra Club has been around for a much longer time than the present debate. It is even sadder that instead of at least considering the scientific and rational aspect of the changing and diminishing environment, you are more interested in finding fault, even where there may be none, because you are listening to people whose interests are far from your welfare. As far as Al Gore is concerned, as long as he keeps trying to bring attention to the destruction of the environment and the issues of global warming or even climate change, I don’t care if he uses the space shuttle.

Think about your future and open your eyes. The people who are trying to turn you away from these issues are only trying to prolong the time in which the inevitable expenses of the necessary changes to protect the environment and more importantly the people of this planet will be due. Read important books, written by scientist, not propaganda. The rivers and lakes are being poisoned, your food is poisoned and your health is being played with. Do you honestly think that the constant reduction of green spaces and the cutting down of trees is not going to impact your life? You must travel to India or China and then you will get some enlightenment. Did you know that in Mumbai a citizen of that city has triple the chances of lung cancer than a normal person? That is the same chance as if you smoked two packs a day for all of your life. What else do you need? We have to stop this lock stock and barrel adherence to the republican party. There is no reason why you should be less of a republican unless to buy all of their propaganda pall mall. There is no reason for this kind of ignorance. Demand that your party do what is best for you and stop letting your party erode your rights in the name of corporate profit. Take back your party and demand that the welfare of the people come first. Do you think big corporations care about your beliefs? your religion? No.

Do you, Che’, feel like you have to protect Greg from me because I might hurt his feelings? A retorical question, naturally. He’s a big boy and I’m sure he’d make hamburger of this old lady, should he decide to take off his gloves.
I’ve got to keep my mind sharp to avoid letting my brain go stale. Greg and crosswords are my means for mental exercise. - Bedtime - better put on my night cap and cuddle up to be ready for the morrow.