Science, Technology, Energy and Mines

What is Climate Change?

The term “climate change” refers to any changes in climate over time, whether as a result of natural phenomena or human activity.

Natural fluctuations in our climate have occurred over a long period of time. What is not natural is the accelerated rate of change that is the result of massive increases in carbon dioxide and other greenhouse gases in our atmosphere. These gases are created when we burn fossil fuels to run our vehicles, to heat or cool buildings, and conduct a variety of other human activities. While natural changes can occur over thousands of years, the changes we are seeing today are occurring in less than one hundred years. When climate change occurs this suddenly, it can have a significant impact on people, economies and the environment. Only by slowing the rate of climate change can we hope to adapt successfully.

Climate versus weather

Climate is not the same as weather. Weather is short term – hour-by-hour, day-by-day, season-by-season conditions of the atmosphere such as temperature, humidity, atmospheric pressure, cloudiness and precipitation. Climate, on the other hand, refers to the long-term average pattern of weather and condition of the atmosphere. Climate is what you expect, such as cold winters. Weather is what you get, such as a blizzard.

The greenhouse effect Earth’s temperature is controlled by a natural system which acts like a greenhouse to keep the sun’s heat in and keep the earth warm.

Quick Facts In 2004, Canada’s GHG emissions had increased by 26.6% over 1990 emissions levels.

Greenhouse gases allow incoming solar radiation to pass through the atmosphere while preventing most of the infrared radiation from the earth’s surface and lower atmosphere from escaping into outer space. This process occurs naturally and, without this phenomenon, our planet would be too cold to support life.

The enhanced greenhouse effect occurs when more and more greenhouse gases are added to the atmosphere, trapping in more of the sun’s heat and causing global average surface temperatures to rise.

Greenhouse gases Any gas that absorbs infrared radiation in the atmosphere is considered a greenhouse gas. These gases include: carbon dioxide (CO2) methane (CH4) nitrous oxide (N2O) hydrofluorocarbons (HFCs) perfluorocarbons (PFCs) sulphur hexafluoride (SF6) water vapor (HO) ozone (O3) Global warming Global warming refers to an increase in the surface temperature of the earth. In the distant past, global warming occurred as the result of natural influences. Today, however, the term is most often used to describe the warming that the earth is experiencing as a result of increased emissions of greenhouse gases. The United Nations Intergovernmental Panel on Climate Change (IPCC) has concluded that today’s global warming is very likely a result of increased concentrations of greenhouse gases resulting from human activity. In particular, they note the increases since 1750 in concentrations of carbon dioxide, methane and nitrous oxide. These three gases are of primary concern because they are closely associated with human activities. Carbon dioxide changes have resulted primarily from the burning of fossil fuels and land use changes. Methane and nitrous oxide increases are caused mainly by agricultural activities. back to top

Quick Facts Water vapour exists naturally in the atmosphere as a result of respiration, transpiration and evaporation. As the earth’s temperature rises, more and more water vapour will be stored in the atmosphere thus enhancing the greenhouse effect. When we think of ozone, we tend to think about the earth’s protective ozone layer which is being depleted by human-caused emissions. This stratospheric ozone protects the earth from the sun’s biologically harmful ultraviolet (UV) radiation. However, lower down in the troposphere (0-11kilometers above the earth’s surface), ozone acts as a greenhouse gas. Tropospheric ozone is formed by the interaction of sunlight, particularly ultraviolet light, with hydrocarbons and nitrogen oxides. While a small amount is produced naturally, most is created as a result of human-caused emissions. Methane is a potent greenhouse gas, warming the earth 21 times as much as the same mass of carbon dioxide. Nitrous oxide is 310 times more potent than carbon dioxide.

Warming trends

Pre-industrial global concentrations of greenhouse gases can be measured over periods of thousands of years though the analysis of ice cores. Since 1750, human activities have resulted in the dramatic increase of carbon dioxide, methane and nitrous oxide.

There is no doubt that this is having an impact. The IPCC has found that globally, “eleven of the last twelve years (1995-2006) rank among the 12 warmest years in the instrumental record of global surface temperature since 1850.” In the past 50 years, the increasingly dramatic signs have been seen everywhere:

• alpine and ocean glaciers are melting
• sea levels are rising
• global average air and ocean temperatures are increasing
• greater temperature extremes are being experienced
• more intense and longer droughts are occurring
• wind patterns and precipitation patterns are changing

There has been nothing comparable to this global warming in the past 1,300 years according to the IPCC. Paleoclimate findings reveal that the last time the earth’s polar regions were significantly warmer than today’s temperatures over an extended period was about 125,000 years ago. Those changes were due to differences in the earth’s orbit and resulted in melting polar ice which raised sea levels by 4 to 6 metres.

The IPCC projects a future warming trend of about 0.2 degrees Celsius per decade over the next 20 years. While this number might strike some as being insignificant, this rise over time is almost certain to increase extremes of heat, heat waves and heavy precipitation events, as well as continuing to raise sea levels. The IPCC notes, “Even if the concentration of all greenhouse gases and aerosols had been kept constant at year 2000 levels, a further warming of about 0.1 degrees Celsius per decade would be expected.”

Climate changes will not be uniform throughout the world. Higher northern latitudes can expect to experience the greatest warming trends along with increases in precipitation and extratropical storms. Most subtropical regions will face decreased levels of precipitation, exacerbating drought conditions. Low-lying areas, small islands and the mega-deltas of Africa and Asia will see increased flooding due to rising sea levels, affecting many millions of people. We are already experiencing the effects of global warming right here in Manitoba. Our average weather has changed and our province is feeling the impact. For more information, see How Will Climate Change Affect Us.

Quick Facts An extratropical storm occurs when a tropical cyclone moves into the cooler and windier environment of the mid-latitudes and transforms in structure, size and intensity. The resulting storm can lose or gain strength, depending on a number of atmospheric components. Extratropical storms are an ongoing concern for Canada since they are very difficult to forecast and can bring surprising severity of weather because of their high moisture content and rainfall.

Predictions and analysis on this page were excerpted from:

• The Intergovernmental Panel on Climate Change; Climate Change 2007: The Physical Science Basis
• The Intergovernmental Panel on Climate Change; Climate Change 2007: Climate Change Impacts, Adaptation and Vulnerability
• Report of the Manitoba Climate Change Task Force; Manitoba and Climate Change – Investing in our future (2001)
• Climate Change Connection, Resource Conservation Manitoba; Puzzled about Climate Change?
• Environment Canada. National Inventory Report 1990-2004 (2006)
• Environment Canada – Canadian Hurricane Centre
• Kyoto and Beyond: The Low Emission Path to Innovation and Efficiency

Additional Resources:

What is Climate Change?
Environment Canada – Frequently Asked Questions about the Science of Climate Change
Climate versus weather
Environment Canada – Frequently Asked Questions about the Science of Climate Change
The greenhouse effect
Intergovernmental Panel on Climate Change (IPCC) – Glossary of Terms
Greenhouse gases
Intergovernmental Panel on Climate Change (IPCC) – Glossary of Terms
Global warming
Intergovernmental Panel on Climate Change (IPCC) – Climate Change 2007 – The Physical Science Basis – Summary for Policy Makers
Warming trends
Intergovernmental Panel on Climate Change (IPCC) – Climate Change 2007 – The Physical Science Basis – Summary for Policy Makers

Intergovernmental Panel on Climate Change (IPCC)

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