Climate Change: Preparing for the Health Impacts

Climate Change 101

Kaila-Lea Clarke, Climate Change and Health Office, Safe Environments Programme, Healthy Environments and Consumer Safety Branch, Health Canada, and Denis Bourque, Meteorological Service of Canada, Environment Canada

Climate change is the long-term shift from the usual or expected weather patterns for a particular area. Although it is not a new problem, climate change is receiving increasing attention because current changes are occurring at an alarming rate and magnitude. In this article, the authors introduce the term "climate change," explain its causes, and identify some current and future environmental impacts.

Weather, Climate and Climate Change

To understand climate change and measure its impacts, you first need to know what it is and what causes it. "Weather" and "climate" are often used interchangeably, but they are actually two distinct terms. Weather is defined as day-to-day atmospheric conditions, whereas climate is the average weather - including seasonal extremes and variations - for a specific location or a region.¹ Climate is calculated by averaging weather conditions and patterns over a long period of time - usually 30 years.¹

Occurring over decades, climate change is a long-term shift from the usual or expected climate patterns for a particular area.¹ This shift is measured by changes in some or all of the features associated with average weather for an area. On a global scale, climate change means a long-term shift in the Earth's prevailing weather - for example, shifts in atmospheric and surface variables such as:

• temperature
• precipitation
• wind
• humidity
• cloud cover
• soil moisture
• sea surface temperature
• concentration and thickness of ice

Climate change involves changes in average weather conditions, as well as changes in how much the weather varies from these averages. The latter is usually referred to as climate variability.¹ Climate change can result from both natural processes and human influences. Natural processes that contribute to climate change include variations in the intensity of the sunlight and solar radiation reaching the Earth, volcanic eruptions and ocean currents.^1,2 Human influences include emissions of greenhouse gases and gases that deplete the stratospheric ozone layer, deforestation, local air pollution, and agricultural practices and alterations in land use.^{1, 2}

Climate Change and Greenhouse Gases

The Earth's climate is regulated by the amount of energy it receives from the sun and the amount that is radiated back toward space. As shown in Figure 1, the land and oceans absorb much of the energy that reaches the Earth, while the remaining energy is released back into the atmosphere in the form of heat (infrared radiation). While most of this heat escapes into space, some is absorbed by atmospheric greenhouse gases that act like an insulating blanket or the glass walls of a greenhouse - holding in the heat and helping to warm the planet.¹ The process by which the Earth's atmosphere captures and holds escaping heat is called the greenhouse effect. Atmospheric gases, such as carbon dioxide (CO₂), methane, nitrous oxides and water vapour, are called greenhouse gases (GHGs). Most GHGs occur naturally, but human activities have increased their concentrations^{1, 2, 3} and introduced other GHGs, such as chlorofluorocarbons (CFCs), which also contribute to depletion of the ozone layer.

Figure 1: The Greenhouse Effect

Source: Adapted with permission from Environment Canada, 2005. ⁴

A Natural Phenomenon

The natural greenhouse effect is an important phenomenon. Without it, the Earth's average surface temperature would be a frigid -18^oC, rather than the current temperate +15^oC.³ Although greenhouse gases have created ideal conditions for human, animal and plant life to thrive, disturbances in their natural concentrations now threaten those life-supporting conditions. Figure 2 illustrates the recent rise in CO₂.

Figure 2: Trends in Atmospheric Carbon Dioxide (CO₂) Concentration over the Past 1,000 Years

Source: Adapted with permission from Natural Resources Canada from D.S. Lemmen and F.J. Warren, 2004. ⁵

Global Warming

Since the industrial revolution, humans have been burning increasingly large quantities of fossil fuels, such as coal, oil and natural gas, which increase the concentration of CO₂ in the atmosphere (CO₂ has increased approximately 30%³). This enhances the greenhouse effect and causes the Earth's surface temperature to rise. Other human activities, such as waste disposal and land clearing, have also contributed to the increase in GHGs.^{1, 2} The resulting increase in the temperature of the Earth's lower atmosphere is referred to as global warming. This temperature increase contributes to changes in atmospheric conditions referred to as climate change by triggering a series of changes within the overall global climate system.³

Some Environmental Impacts of Global Warming³

• Changes in precipitation (some areas will get more, others less) could result in a greater incidence of flooding.
• Rising sea levels will cause increasing coastal erosion, which may damage fish spawning grounds and flood low-lying coastal areas, resulting in the loss of rich, alluvial farmlands and the displacement of populations.
• Melting glaciers and polar ice caps may further raise sea levels and possibly reduce late summer river flows in regions such as the western Prairies.
• There will be a higher incidence of forest fires and pests (tropical and boreal forests are especially vulnerable), which will likely change species composition.
• Some plant and animal species that are unable to move or adapt fast enough to the changing conditions will be lost, and others more suited to the new environments will increase.
• There will be more frequent and intense storms and tornadoes, which could result in a greater incidence of natural disasters - for example, landslides and damage from ice, waves and high winds.

Environmental Impacts of Climate Change

Knowledge about climate change is growing rapidly as organizations around the world investigate and monitor its progress and various impacts. The Intergovernmental Panel on Climate Change (IPCC), established by the World Meteorological Organization and the United Nations Environment Program, has drawn on the work of hundreds of scientists around the world to produce a series of publications that are now widely used by policy makers, scientists, other experts and students. In its Third Assessment Report, the IPCC attributed much of the increased warming over the last 50 years to GHG emissions resulting from human activities.⁶ Climatologists have determined that the 20th century was likely the warmest in the past 1,000 years, that the 1980s and 1990s were likely the warmest decades since the mid-1800s, and that this general warming trend has continued through 2004.⁶ The Earth's average surface temperature has increased approximately 0.6^oC over the past 100 years.⁵ Many mountain glaciers are also melting at alarming rates, and global sea levels have risen 10 to 25 cm in the last century.⁷ Some additional environmental impacts of global warming are highlighted in the text box above.

How Will Canada Be Affected?

Canada's average temperature increased approximately 1^oC in the past 100 years. Since the global warming trend is strongest in the Arctic, and Canada is a northern country, Canada will likely warm more than the global average during this century - possibly by as much as 5^oC to 10^oC. Temperature increases will vary and certain regions - such as the North, and the southern and central areas of the Prairies - are likely to experience the most pronounced warming.¹ Canada will likely see changes in its water supplies and its ability to grow food, including potentially costly changes to agricultural methods.³ Canadian scientists have examined the anticipated impact of climate change on human health and the environment, including water resources, industries and ecosystems.³ Some of these impacts for specific regions of Canada are outlined in the text box.

Climate Change Projections for Regions of Canada^{1, 2, 3, 8}

Atlantic Canada - severe storms, increased coastal erosion, flooding of freshwater marshes.

Québec and Ontario - extreme weather events, including heat waves, flooding and droughts (causing lake and river levels to decline), and an increase in forest fires. Greater demand for electricity for air conditioning during increasingly hot summers. Air quality is likely to decrease. Frost-free seasons may permit the spread of diseases (e.g., Lyme disease, malaria, West Nile virus). Growing seasons may be extended, potentially benefiting many farmers; however, droughts, pests and crop diseases may offset any benefit.

Prairies - increased incidence of droughts and floods, resulting in both social and economic impacts.

British Columbia - forest and fish stocks may be affected, with warmer waters potentially harming aquaculture. Warmer winters may increase insect pests, while wetter springs could delay planting. There may be an increase in landslides and debris torrents in mountainous areas.

North - likely to experience the most pronounced warming, with particular problems with infrastructure, pipelines, roads and buildings associated with melting frozen ground. Seasonal forest fires may increase in some areas.

Now and in the Future

The effects of climate change are already happening. To better understand future scenarios and impacts, scientists use elaborate computer models to predict how the Earth's climate could be influenced over time by different GHG concentrations and atmospheric conditions. These models incorporate many of the complex interactions and feedback mechanisms within the global climate system. To assess their reliability, the models are tested for their ability to simulate past climate behaviours.

A Final Note

Many nations are responding to climate change by trying to reduce the flow of man-made greenhouse gases and other pollutants into the atmosphere - for instance, by following the guidelines set out in the Kyoto Protocol. However, these measures cannot halt climate change; they will only slow it down and (perhaps) mitigate its severity. Since climate change processes are already under way, efforts must focus on assessing current and future health vulnerabilities, and identifying options for workable interventions and adaptations.

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Issue 11 References

References for Climate Change 101

1. Meteorological Service of Canada & Environment Canada. (2002). Frequently Asked Questions about the Science of Climate Change. Ottawa, ON: Minister of Supply and Services.

2. Environment Canada. (2001). Climate Change Overview: What is Climate Change? Retrieved August 8, 2005, from
< http://www.ec.gc.ca/climate/overview_factors-e.html>.

3. Environment Canada. (2005). Climate Change Overview: The Science of Climate Change. Retrieved August 8, 2005, from
< http://www.ec.gc.ca/climate/overview_science-e.html>.

4. Environment Canada. (2004). The Earth is a Greenhouse. Retrieved August 15, 2005, from
< http://www.climatechange.gc.ca/english/climate_change/earth.asp>.

5. Lemmen, D.S., & Warren, F.J. (Eds.). (2004). Climate Change Impacts and Adaptation: A Canadian Perspective. Ottawa, ON: Natural Resources Canada.

6. Watson, R.T., et al. (2001). Climate Change 2001: Synthesis Report. Contributions of Working Groups I, II and III to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK: Cambridge University Press.

7. Intergovernmental Panel on Climate Change. (2001). Climate Change 2001: Impacts, Adaptation and Vulnerability. Summary for Policy Makers and Technical Summary of the Working Group II Report. Cambridge, UK: Cambridge University Press.

8. Government of Canada. (2005). One-Tonne Challenge: Climate Change Impacts. Retrieved August 8, 2005, from
< http://www.climatechange.gc.ca/onetonne/english/impacts.asp>.