CLIMATE AND WEATHER

The difference between climate and weather is like the difference between the forest and the trees.

Weather is what we experience (and complain about) on a daily basis. We understand it in the familiar terms of the weather report: cloudy, windy, rainy, humid, sunny or snowy.

Climate is a description of average weather conditions over time, a period of at least 30 years or more.

CONSTANT CHANGE

Climate results from interaction between the atmosphere, the oceans, the land surface, the polar ice caps and biological life (plants, animals and humans). Our climate is constantly changing, but most of the change takes place over generations and goes unnoticed. However, a sudden extraordinary event in one place can bring about rapid change all over the globe. For example:

Dust in the atmosphere from volcanic explosions can result in cooling due to increased reflection of solar energy. A huge volcanic eruption in Indonesia in 1815 has been linked to the 1816 'year without summer' in the eastern US and Canada.²

In 1983 El Niño, a warm ocean current off the Peruvian coast, was 7^0°C warmer than usual. Weather across the world was altered - including floods along the west coast of North and South America and droughts in southern Asia, Africa and Australia.

CARBON CULPRITS

Carbon dioxide is the single most important greenhouse gas and is linked directly to industrial development and deforestation.

When all greenhouse-gas sources are added together the responsibility for global warming is as follows¹⁰:

The West (15% of world pop.) - 46%
USSR/Eastern Europe (7% of pop.) - 19%
Third World (78% of pop.) - 35%

THE GREENHOUSE EFFECT

A layer of gases in the atmosphere acts like an insulating blanket trapping solar energy that would otherwise escape into space. Without these 'greenhouse gases' the earth would be frozen, barren and lifeless.

HOW IT WORKS
1. Solar energy enters the atmosphere unaffected by the greenhouse gases.
2. The sun's rays are absorbed by the earth, then reflected back at longer heat wavelengths.
3. Greenhouse gases absorb this heat, then send it back to the surface.
4. When greenhouse gas concentrations increase, more heat is captured causing temperatures in the lower atmosphere and surface to rise. This affects both weather and climate.

COLD COMFORT

By analyzing gas trapped in glacial ice scientists have found CO₂ levels have risen steadily since the Industrial Revolution. CO₂ concentrations are presently rising by 3-4% a decade and have increased by 25% over the last 300 years.

FEELING THE HEAT

Over the past 300 years, as a result of human activity, concentrations of the main greenhouse gases have increased significantly. There are strong indications that global warming has already begun as a result.

In the last 90 years the earth has warmed by about half a degree centigrade. That may not sound like much - but a small change can make a big difference. Our average global temperature is only 5°C warmer today than during the last ice age 13,000 years ago.⁵

The present global surface temperature is about 0.4°C higher than the mean value from 1950 to 1980.

The 1980s were the warmest decade on record; the warmest years this century were (in order) 1988,1987,1983,1981,1980 and 1986.⁶

Estimated contribution to global warming of main greenhouse gases in the 1980s.

PUMPING GAS

THE MAIN GREENHOUSE GASES

Carbon dioxide (CO₂)
Source: Comes mostly from burning fossil fuels (oil, gas and coal) for electricity and in cars and factories. Also from forest burning.
Annual Increase: 0.5%
Life span: 7 years

Methane (CH₄)
Source: Bacterial decomposition of organic matter (without oxygen) in rice paddies, swamps and intestines of ruminants like cows and sheep. Also from burning wood, mining coal.
Annual increase: 1%
Life span: 10 years
Traps heat: 30 times stronger than CO₂.

Chlorofluorocarbons (CFCs)
Source: Chemically synthesized for use as coolants in refridgerators and air conditioners. Also used in foam insulation, aerosol sprays.
Annual increase: 6%
Life span: up to 15,000 years
Traps heat: 10-20,000 times stronger than CO₂.

Nitrous oxide (N₂O)
Source: Bacterial reactions in soil and water and from the breakdown of nitrogen-based chemical fertilizers. Also from burning fossil fuels and wood (deforestation).
Annual increase: 0.4%
Life span: 170 years
Traps heat: 150 times stronger than CO₂.

Surface Ozone (0₃)
Source: About 75% of surface ozone results from photochemical reaction of sunlight on vehicle pollutants (carbon monoxide, nitrogen oxide and nitrogen dioxide).
Annual Increase: 2%
Life span: 2-3 weeks
Traps heat: 2,000 times stronger than CO₂.

WEATHER WARNING

Sophisticated computer models predict the earth's surface temperature will rise between 3 and 5°C by the middle of the next century - change unprecedented in human history. The exact impact of such a change is unclear. But scientists predict¹²:

greater extremes of weather; more storms and hurricanes in humid tropical countries and drier, hotter weather in semi-arid tropical regions with consequent disruption of food production and water availability.

higher temperatures will melt polar icesheets and glaciers, increasing sea levels by between 1 and 3 metres in 60 years, and causing widespread flooding. The great river deltas of the world would be inundated - it is estimated that a mere 50 cm rise in sea level would permanently flood 12% of Bangladesh. Egypt could lose 20% of its arable land, affecting some 10 million people.

plants and animals will be unable to adapt to rapid temperature increases and new climatic conditions. Vast forests in Canada, Scandinavia and the USSR could die resulting in massive forest fires and the release of a huge volume of additional CO₂, thus accelerating global warming.

1 The Gaia Atlas of Planetary Management, ed. Norman Myers (Doubleday, 1984).
2 Climate Change and Variability, Environment Canada Fact Sheet, 1986.
3 Ibid
4 The Greenhouse Gases, Environment Canada Fact Sheet, 1986.
5 The Changing Climate, Stephen Schneider (Scientific American, Sep 1989).
6 Global Climatic Change, R Houghton and G Woodwell, (Scientific American, April 1989).
7 World Resource Institute as noted in The Economist, 11 March 1989.
8 Solving The Greenhouse Dilemma, Association for the Conservation of Energy, 1989, Policy Options for Stabilizing Global Climate, US Environmental Protection Agency Executive Summary, Feb 1989; see also above point 4.
9 The Greenhouse Gases, UNEP, 1987.
10 Global Warming, C Flavin (Worldwatch, 1989).
11 Ibid
12 Developing Policies for Responding to Climatic Change, UNEP and WMO (Villach, Austria, 1988).