Heating up.

In the 1995 second assessment report (SAR) the Intergovernmental Panel on Climate Change made the widely quoted statement that "The balance of evidence suggests a discernible human influence on global climate." The phrase "balance of evidence" was used deliberately to suggest the (English) common-law standard of proof required in civil as opposed to criminal courts: not as high as "beyond reasonable doubt." In 2001, the third assessment report (TAR) upgraded this by saying "There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities"

Back in 1824, good old Jean Baptiste Joseph Fourier discovered the process we now call the greenhouse effect. A mathematician and physicist in France, Fourier came up with a formula involving sines and cosines to describe the transfer of heat among molecules.

The "natural" greenhouse effect is essential to the maintenance of life on Earth. The problem that appears to be occurring today is the "anthropogenic" greenhouse effect. That's the scientific word for human activities, such as the burning of fossil fuels, that add to the natural heating.

A bi-product of burning coal, oil, and gas, is carbon dioxide (C[O.sub.2]), which has thickened the warming blanket of the Earth's atmosphere. This blanket allows the Sun's heat to warm up the planet but traps the heat in, keeping the atmosphere warmer.

By 1865, factories and steam locomotives had been belching out vast quantifies of smoke and C[O.sub.2] for several decades. Then, the average air temperature at the surface of the Earth was around 13.7[degrees]C. By the 1990s, millions of gasoline-powered engines were burning fossil fuels and most of our buildings were heated or cooled by similar energy sources.

Based on climate models used by the United Nations Intergovernmental Panel on Climate Change (IPCC), temperatures may increase by 1.4[degrees]C to 5.8[degrees]C between 1990 and 2100. That could spell disaster, with rises in sea level and changes in the amount and pattern of precipitation. And, that will mean more extreme weather events such as floods, droughts, heat waves, lower agricultural yields or biological extinctions.

The IPCC also concludes that most of the warming observed over the last five decades has been caused largely by us. An international group of science academies from the G8 countries (Canada, France, Germany, Italy, Japan, the United Kingdom, the United States, and Russia) and Brazil, China, and India support this view.

In their 1990 book It's a Matter of Survival (ISBN: 0814659322), David Suzuki and Anita Gordon say a warmer world in 2040 will have no forests. They predict that fisheries will be affected, and there will be widespread starvation, while coastal towns will be destroyed. The authors say that it's "our carbon dioxide emissions that are threatening to sink entire nations. Europe, America, and what used to be the Soviet bloc countries generate 71 percent of the world's carbon dioxide. Sea-level rise and drought in the next five decades could drive more than 60 million people from their homes ... Progress could become more costly than we ever imagined."

A recent international scientific study of Arctic climate change (released in November 2004) confirms the Arctic is warming more rapidly than the rest of the globe. The Arctic Climate Impact Assessment (ACIA) predicts that the rapidly warming Arctic will have a major physical, ecological, social, and economic impact worldwide this century. For four years, more than 300 scientists from 15 countries examined the region and found that temperatures there are rising at twice the global average.

According to the 1,400-page report, temperatures in the Canadian Arctic have risen by three to four degrees over the past 50 years, and sea-ice cover has declined 10 percent over the past 30 years. Eventually, the ice melt is expected to open the Northwest Passage for year-round shipping, while devastating ice-dwelling seals and polar bears in the next 50 years. It also could result in other countries challenging Canada's sovereignty in the North.

As well, a projected warming and melting of the Greenland Ice Sheet is expected to contribute to global sea-level rise. This will change regional climates and swamp coastal areas worldwide.

The combined effect of rising sea levels, decreasing sea ice, and thawing permafrost will leave coastal Arctic towns vulnerable to erosion and flooding. The changes will have a huge impact on Aboriginal lifestyles which will face major economic and cultural adjustments. New health issues will also arise as increased ultraviolet radiation will affect people, as well as animals, and plants: the current Arctic generation is expected to receive about 30 percent more UV than their parents.

If global warming does destroy us in the end, it won't be the first time Earth has seen such devastation.

Researchers at the University of Washington recently reported that an ancient version of global warming, known as the Great Dying, may have caused the biggest mass extinction on the planet. The warming, a result of volcanic activity about 250 million years ago, wiped out about 90 percent of all marine life and nearly three-quarters of land-based plants and animals. It was a lengthy process: the researchers found evidence of a gradual extinction over about 10 million years followed by a sharp increase in the extinction rate that lasted another five million years. It's thought to have been the result of a combination of warming and oxygen deprivation, unlike the mass extinction of the dinosaurs 65 million years ago that has been linked to an impact by a large asteroid or comet off the coast of what is now Mexico.

SUGGESTED ACTIVITIES:

1. University of Saskatchewan marine scientist Alec Aitken says increased shipping traffic in the North is almost certain to bring "absolute and outright challenges to our national sovereignty." Do a report on which countries could challenge Canada's claims over the Arctic and how they might be handled.

2. In 2004, the Danish government, which controls Greenland, declared its intention to claim the mineral rights under the North Pole. Write a follow-up report on Arctic mining and the scramble to claim the region involving Denmark and Canada, with the United States and Russia as interested bystanders.

3. At the opposite climate extreme, Earth has weathered some frigid times as well. According to The Globe and Mail, two research papers published in 2005 in Geophysical Research Letters "outlined a scenario in which the Earth iced over after the solar system passed through a cloud of interstellar dust so large that it took as long as 500,000 years to pass all the way through. There is evidence that from 600 million to 800 million years ago, there were at least two glaciations that covered much of the planet." Discuss whether or not you think this supports the view of skeptics that the current changes in climate are natural.

Websites

Earth Science Activities: The Franklin Institute Online--http:// sln.fi.edu/tfi/activity/ earth/earth-4.html

NOVA online--www.pbs. org/wgbh/nova/ice/ greenhouse.html

United Nations Environment Program--http://www.grida. no/climate/vital/03.htm

FACT FILE

While some models indicate that summer sea ice in the Arctic will disappear by the end of the century, others predict it will be reduced only by half.

Inuit have no worlds for robin, salmon, hornets, and barn owls, which all are appearing in the Arctic for the first time as a result of global warming.

The arguments over global warming are viewed differently in different parts of the world. In Europe, for example, global warming has gained wider acceptance than in other parts of the world, most notably the United States.

IT'S IN THE WATER

One scientist at the Scripps Institution of Oceanography in La Jolla, California, says the sea is a better place to look for climate change than the air.

Dr. Tim Barnett says water has a far higher capacity to retain heat than air, so most of any heat that's causing global warming would be expected to end up in the oceans. That's just what he and his team of scientists found. After studying ocean-temperature surveys made over the past 65 years, which involved examining seven million observations of temperature, salinity, and other variables in the world's oceans collected by the U.S. National Oceanic Atmospheric Administration, they confirmed that the sea has warmed by 0.5[degrees]C n the last 40 years. Only the greenhouse computer models studied matched the changes that have been observed in practice so the researchers concluded that warming has been triggered by human activity.

"All the potential culprits have been ruled out except one," says Dr. Barnett.

GLOBAL DIMMING

Not only is the world getting warmer. It's getting darker too. Scientists aren't entirely sure why we're receiving less sunlight (visual light as opposed to ultraviolet light that is increasingly penetrating our ozone layer) but pollution is thought to be partly to blame. Tiny particles of soot and sulphur compounds, for example, reflect sunlight and promote the formation of bigger, longer-lasting clouds. Records show that over the last 50 years the average amount of sunlight reaching the ground has gone down by almost three percent a decade.

While the rate of dimming varies around the world, the largest reductions have been found in the mid-latitudes of the northern hemisphere.

However, the trend started to reverse in the 1990s. Recent data reveals the planet's surface has brightened by about four percent during the past decade as a result of pollution control.

One of the biggest concerns of some scientists is that the dimming, with its cooling effect, has offset the warming from greenhouse gases. As the cooling is reduced, they fear that global warming will be far more serious than previously predicted. Some have suggested the temperature could rise as much as 10[degrees]C by 2100 twice the current prediction, which in itself is expected to cause enormous damage.

Scientists have also linked global dimming to lack of rain in sub-Saharan Africa--and the catastrophic droughts that hit Ethiopia in the 1980s. They worry that the same thing will happen again in areas such as Asia, home to billions of people.

And there's more. Some experts suggest that such a rise in temperature would trigger a rapid and irreversible release of the huge deposits of methane hydrates, currently locked beneath the ocean floor. That's bad news because methane gas is one of the most powerful of the greenhouse gases (about 21 times stronger than carbon dioxide). Some consider this another possible theory behind the Permian-Triassic extinction event (the Great Dying) approximately 250 million years ago. It may also have something to do with the extinctions associated with the Paleocene-Eocene Thermal Maximum around 55 million years ago. This marked one of the most rapid and extreme global warming events recorded in geologic history. Sea surface temperatures rose almost 8[degrees]C over a period of a few thousand years. Scientists have found the entire depth of the ocean warmed, severely reducing oxygen levels and causing mass extinctions of deep-sea life. It is estimated that it took the planet as tong as 100,000 years to recover to a "normal state" following the Thermal Maximum.