| | What is climate change? | What are the greenhouse gases? | How do people affect GHGs? | How could Canadian agriculture be affected by climate change? | Why should we be paying attention?
What is Climate Change?
Although the Earth's climate is constantly changing and global climate change occurs naturally, the rate of future climate change may be more rapid than at any time in the last 10,000 years. The majority of the world's scientists studying this topic conclude that this expected climate change will differ from previous climate change because of human activity.
The atmosphere has an effect like a greenhouse on the Earth's temperature. The energy from the sun reaching the earth is balanced by the energy the Earth emits to space. Greenhouse gases (GHGs) trap some of the energy the Earth releases to space. The greenhouse gases in the atmosphere act as a thermostat controlling the Earth's climate. Without this natural greenhouse effect, the average temperature on Earth would be -18°C instead of the current +15°C. Therefore, life as we know it would be impossible.
Energy levels of GHGs in the atmosphere have increased in the past 100 years. The scientific evidence for this is very solid. In a 1995 scientific assessment, the Intergovernmental Panel on Climate Change (IPCC) concluded that "the balance of evidence suggests a discernible human influence on global climate".
Global climate change will mean substantial impacts on the environment, including water resources, fisheries, forests, wildlife and ecosystems. Scientists also predict that the enhanced greenhouse effect could amplify climate variability. For the agriculture industry, changes in temperature or precipitation could affect production on Canadian farms.
What are the Greenhouse Gases?
The major GHGs in our atmosphere are water vapor, carbon dioxide (CO2), methane (CH4), halocarbons, which are used as refrigerants, and nitrous oxide (N2O). Modern industry and lifestyles have led to elevated levels of existing GHGs such as carbon dioxide, methane and nitrous oxide, and in some cases, completely new GHGs such as halocarbons (Figure 1).
Figure 1 Greenhouse gases approximate contribution to enhanced heat trapping
Greenhouse gases differ in their ability to absorb the radiation leaving the Earth. The ability of a gas to trap heat depends on its capacity to absorb and re-emit radiation and on how long the gas remains in the atmosphere. In order to compare emissions from different sources, the global warming potential of each gas is equated to the global warming potential of carbon dioxide. For example, the global warming potential of one tonne of methane is 21 times more potent than one tonne of carbon dioxide over a 100 year period (Table 1).
Table 1 Global Warming Potentials
| Gas | Relative Global Warming Potential
(CO2 Equivalent) |
Carbon Dioxide
Methane
Nitrous Oxide | 1
21
310 |
Source IPCC, 1996
How do People Affect GHGs?
Since the industrial revolution, concentrations of GHGs have been increasing steadily as a result of industrialization and deforestation. Environment Canada states that by 1992, carbon dioxide had increased by 30%, methane by 145% and nitrous oxide by 15% in the past 100 years. Current rates of increase are 0.5% per year for carbon dioxide, 0.6% for methane and 0.3% for nitrous oxide. Without a concerted effort by all Canadians, our GHG emissions are expected to be 20 to 25% higher in 2010 than in 1990. If these current rates of increase continue, many scientists expect a significant impact on the world's climate.
Human activities increase GHG levels by introducing new sources or removing natural sinks, such as forests. Sources are processes or activities that release greenhouse gases; sinks are processes, activities or mechanisms that remove greenhouse gases. The levels of greenhouse gases are determined by a balance between sources and sinks.
How Could Canadian Agriculture Be Affected by Climate Change?
As a northern country, scientists expect climate change in Canada to be greater than in most other countries. Scientists also predict increased variability in weather patterns across Canada to accompany the rise in temperatures.
The predicted change in climate will directly affect crop and livestock management decisions such as seeding dates, crop variety choices, pest and disease management, water management strategies and other important factors. This, combined with the fact that GHG emissions change with the type of farming operation and within individual farms, adds another challenge to managing the rapidly changing agriculture industry in a sustainable manner.
Why Should We Be Paying Attention?
Canada and some 160 industrialized nations around the world have signed an international agreement on climate change aimed at reducing greenhouse gas emissions. Under this agreement, which is known as the Kyoto Protocol, Canada has committed to reduce its emissions to 6% below 1990 levels by 2008 to 2012. In other words, emissions must be reduced below those of ten years ago.
The agriculture industry already has some tools that reduce GHG emissions, such as direct seeding and other 'best management practices'. The industry's efforts to develop strategies to reduce its GHG emissions will be guided by cost-effective, practical solutions that maintain or improve Alberta's competitive position in the international marketplace.
Sources:
- "Climate Change 1995: The Science of Climate Change". J T Houghton, L G Meira Filho, B A Callender, N Harris, A Kattenberg and K Maskell (Eds.). Cambridge University Press. 572 pp.
- Environment Canada. 1997. Global Climate Change, "Greenhouse Gases"
- Environment Canada. 1997. Global Climate Change, "The Science of Climate Change".
- Australian Greenhouse Office. 1999. National Emissions Trading: Establishing the boundaries. Discussion Paper No. 1. Commonwealth of Australia.
- Agriculture and Agri-Food Canada. 1998. The Health of Our Air: Toward sustainable agriculture in Canada. Research Branch, Agriculture and Agri-Food Canada.
Alberta Environmentally Sustainable Agriculture Council
Appointed by the Minister of Agriculture, Food and Rural Development.
Mandated to (1) identify and evaluate environmental challenges and opportunities facing the agriculture and food processing industry; and (2) encourage the industry to proactively address environmental issues.
Adapted from: Greenhouse Gases - Things You Need to Know - March 2000. |
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