Climate Change

What is Climate Change?

Climate is the long-term average of weather patterns observed for a particular region¹. Climate change is defined as any change in climate over time, either natural or human influenced. The rate of climate change on earth has dramatically increased since industrialization and so for our purposes, climate change refers to deviations in long-term weather patterns as a result of human activities that result in increasing concentrations of greenhouse gases (GHGs) in the atmosphere, which trap heat and increase global temperatures also known as the greenhouse effect (Figure 1).

Figure 1.  The Greenhouse Effect

Source:  Sustainable Energy Ireland (SEI), 2007

Greenhouse gases are not equal in terms of their ability to capture and remit heat. The global warming potential (GWP) of each GHG takes into account both the ability to trap heat and the lifetime of the gas. Methane (CH₄) and nitrous oxide (N₂O) are 21 and 310 times more potent than carbon dioxide (CO₂) respectively (Table 1).

Table 1.  Global warming potential of common GHGs

GHG	Formula	100-Year GWP	Atmospheric Lifetime (years)
Carbon Dioxide	CO2	1	Variable
Methane	CH4	21	12 ± 3
Nitrous Oxide	N2O	310	120

Atmospheric GHG concentrations have increased dramatically since the pre-industrial revolution as a result of human activities. These activities have created new sources of GHGs (intensive fossil fuel burning) as well as removed valuable sinks (ex. deforestation), and it is the balance of sources and sinks which determines the amount of GHG in the atmosphere. In the past 50 years startling observations have been made globally:

• Glaciers are melting
• Sea levels are rising
• Average global air and ocean temperatures are increasing
• Greater temperature extremes are being observed
• Longer and more intense droughts are occurring
• Wind and precipitation patterns are being altered

 

References:

¹  Environment Canada, 2008

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