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Global warming and cooling in the future

Here are the central points of the preceding material;

Earth would be an ice planet without the greenhouse effect.
Weather prediction and climate prediction are complicated.
The Earth is a complex thing.
The Earth is getting warmer.
The current average temperature of the Earth is high but not unusually so.
Human activities can effect global climate.
Global temperature and carbon dioxide levels are closely connected.
Global temperature and methane levels are closely connected.
Current carbon dioxide and methane levels greatly exceed past levels.

These are all easily verified facts.

IPCC projections

In 2001 the IPCC made these projections. [1]

By the year 2100, the average temperature of the Earth will be between 1.5C and 4.5C warmer. The increase will not be uniform. The increase will be less in the tropics and the southern hemisphere. The increase will be greater in the northern hemisphere and very large in the Arctic. The projected 12C increase for the Arctic is enough to thaw the permafrost. 

By the year 2100, carbon dioxide concentration will be between 540 and 970 ppm. That compares with the current reading of 379 ppm. 

These projections are very imprecise. But even the low projections represent very significant changes. 

Do your own projections

If you have any doubts about the reality of global warming, consider this: The greenhouse effect makes the Earth 33C warmer. Carbon dioxide explains 65%, or 22C of the warming. The carbon dioxide in the atmosphere has increased from 312 ppm to 379 ppm or 21.5% since 1958. Adding 21.5% of 22C is almost 5C of global warming. Then consider that carbon dioxide levels are rapidly increasing. A large temperature increase has not occurred because of the cooling effect of sulfur dioxide and because of the thermal inertia of the oceans.

You can calculate your own projection for carbon dioxide concentration for 2100 based on the current rate of increase. The current rate of increase (as noted earlier) is 1.87 ppm per year. That would add 179.5 ppm in 96 years. The current reading is 379 ppm giving 558.5 ppm in 2100.

The ice record goes back more than 400,000 years. Atmospheric carbon dioxide concentration never exceeded 300 ppm in all that time. It was usually much lower. Now the concentration is 379 ppm and 600 ppm and even 900 ppm seem possible by the end of the century. Knowing this, and knowing the role that carbon dioxide plays in the greenhouse effect, must be alarming.

What will happen

It is impossible to know precisely what will happen to the Earth's climate. The models are not very good and they require good data which are hard to get.

But a few things can be said. A 1C or 2C global temperature increase applied for 1 or 2 centuries will have a profound effect. That is enough to cause the icecaps of Greenland and Antarctica to melt and the oceans to rise. Some northern areas could become farmland while the Sahara might become bigger. Many plants and animals will find themselves in climates they are not suited for. Storms may become more intense. 

A temperature rise of a few degrees will change the appearance of the globe. A temperature rise of a few degrees will cause the Earth's oceans to rise by 5 meters. That is enough to put almost half of Florida under water as this map illustrates.[2] Some countries would disappear including Bangladesh and the Netherlands. (Water added to the ocean from melting icecaps is not the primary reason for the rising oceans. The reason is the increase in volume that results from warming the ocean.)

Climate is obviously a universal concern. The findings of scientists that lead to the predictions need to be widely understood.

[1] In 1988 the United Nations established the IPCC (Intergovernmental Panel on Climate Change). The IPCC is fundamentally a scientific body although the UN is a political institution. Leading scientists from around the world make up the IPCC. In 2001, the IPCC published a report called Climate Change 2001: The Synthesis Report. It is available online. You can download all of it or single chapters. There are two summaries; one is technical and one is for policymakers. You can see The Synthesis Report and related reports at:
http://www.grida.no/climate/ipcc_tar/

[2] http://www.pbs.org/wgbh/warming/ In "What's Up with the Weather?" NOVA and FRONTLINE join forces to investigate the science and politics of one of the most controversial issues of the 21st century: the truth about global warming. Click on water world.

http://www.giss.nasa.gov/research/impacts/ NASA/Goddard Institute for Space Studies. The Antarctic ice core data is from a very readable presentation called Can We Defuse the Global Warming Time Bomb? given in June 2003 by James Hansen. This is a 1.5 megabyte PDF report. Look at the list of science briefs.