The ABC’s Of Global Climate Change

Siur-thinkstock-480457436-Coal StacksReprinted with permissions from the Canadian Association of Physicians for the Environment (  Kim Perrotta, Executive Director, CAPE

In 2015, the International Panel on Climate Change (Panel) reported that: greenhouse gas emissions (GHGs) from human activity are now higher than any other period in human history; the concentration of GHGs in the atmosphere is now higher than at any other time in the last 800,000 years; and it is “extremely likely” that emissions from human activity, along with other human activities such as deforestation, have been the dominant cause of global warming since the mid-20th century (1).

The Panel reported that, in 2010, approximately 49 Gigatonnes (Gt) of GHGs were emitted from human activity, and that fossil fuel combustion and industrial processes were responsible for more than three quarters of those emissions (1).

51Systems-Thinkstock-490736941-Flooded NeighbourhoodAccording to the Panel, there is fairly strong to very strong evidence that climate change has: more than doubled the occurrence of heat waves in some locations; increased heat-related deaths in some regions; increased extreme precipitation and the risks of flooding in some regions; increased extreme sea levels (e.g., storm surges) since 1970 as a result of increasing sea levels; and significantly increased the vulnerability of some ecosystems and human populations to heat waves, droughts, floods, and cyclones (1).

The impacts of climate change on human health and the environment are expected to become more extreme as we move through the 21st century.  Under a number of different scenarios, it is predicted that climate change will: increase the frequency and intensity of heat waves and extreme precipitation; increase ocean temperatures, ocean acidification, and sea levels; continue to melt permafrost and glaciers; increase the risk of extinction for many plants and animals; undermine the security of food and water supplies; and increase the displacement of people (1).  

The severity of these risks, however, will vary significantly depending upon the actions taken to reduce emissions and protect carbon sinks.  The risks are expected to be severe if global temperatures increase by 4 degrees relative to pre-industrial times.  They are expected to be moderate to high if global temperatures increase by 1 to 2 degrees.  While some of the risks of climate change are now unavoidable, the risks of climate change can be substantially reduced by aggressively cutting emissions of GHGs in the very near future (1).   

In order to keep the global temperature from increasing by 2 degrees, models suggest that annual GHG emissions around the world must be reduced by 40 to 70% of 2010 levels by the year 2050.  To keep the global temperature from increasing by 1.5 degree, annual GHG emissions must be reduced by 70 to 95% of 2010 levels by the year 2050 (1).

Wind Turbines, Leamington, Ontario, Kim PerrottaIn order to meet these aggressive goals, the Panel has identified a number of key measures: moving away from the use of coal and other fossil fuels for the generation of electricity; enhancing energy efficiency to reduce energy demand; and encouraging behavioural changes to reduce energy demand.  In the majority of the models that support a stable climate future, the share of low-carbon electricity supply (e.g., hydro electricity, solar energy, wind turbines) increases from current levels of about 30% to more than 80% by 2050 (1).  

The Panel notes that many of the actions needed to reduce GHG emissions are associated with co-benefits or adverse side effects.  It notes, however, that the co-benefits associated with “energy end-use measures” outweigh the potential for adverse side effects (1).  For example when coal plants are phased out with investments in energy efficiency and renewable energies, significant health benefits can result from improvements in air quality (2).  Likewise, when public transit and bike lanes shift commuters out of their vehicles, significant health benefits can result from improvements in air quality and increases in the levels of physical activity among residents (3).    


  1. International Panel on Climate Change (IPCC). 2015. Climate Change 2014 Synthesis Report for Policy Makers.
  2. Pembina Institute, CAPE, Asthma Society, Lung Assocation of Alberta and NWT. 2013. A Costly Diagnosis – Subsidizing coal power with Albertans’ health.  Prepared by Kristi Anderson, Tim Weis, Ben Thibault, Farrah Khan, Beth Nanni, and Noah Farber.
  3. Grabow, Maggie, Scott Spak, Tracey Holloway, Brian Stone Jr., Adam Menick, Jonathan Patz. 2011. “Air Quality and Exercise-Related Health Benefits from Reduced Car Travel in the Midwestern United States”,Environmental Health Perspectives.