Environment Canada: The Science of Climate Change

24 11 2015

November 23, 2015

Image of Moraine Lake in Banff National Park, Alberta

Image of Moraine Lake
in Banff National Park, Alberta


Key Messages

  • Warming over the 20th century is indisputable and largely due to human activities.
  • Canada’s rate of warming is about twice the global rate: a 2ºC increase globally means a 3 to 4ºC increase for Canada.
  • Effects will persist for centuries because greenhouse gases (GHGs) are long-lived and the oceans are warming.
  • Cumulative CO2 emissions largely determine ultimate warming. A 2ºC warming target may still be attainable, but we are already 65% of the way to the associated carbon limit or budget and global emissions must peak before mid-century.
  • GHG emissions need to become net zero in order to stabilize climate at any temperature.

The Climate System

World Ocean Review

Image: World Ocean Review

Long description

This illustration shows the climate system, its subsystems and relevant processes and interactions. It depicts how energy from the sun is absorbed and re-radiated as the atmosphere interacts with other components of the Earth system, such as the hydrosphere (oceans), the cryosphere (snow, sea ice, and glaciers), the biosphere (animals and plants), the pedosphere (soil) and the lithosphere (rocks). Two-way arrows depict air-ice, ice-ocean, air-ocean, and land air interactions. One-way arrows show incoming solar radiation from the sun and outgoing terrestrial radiation.


  • Energy from the sun is absorbed and re-radiated. The atmosphere acts like an insulator, keeping the surface warm both day and night, providing a life-supporting average temperature of approximately 14ºC.
  • Increases to the amount of GHGs in the atmosphere alter the energy balance (increasing energy absorbed) and lead to climate warming.

Evidence of Climate Change

“Warming is unequivocal”Note *

Global Land and Ocean Temperature Anomalies, January – December
(Annual anomalies relative to 20th century)

Global Land and Ocean Temperature Anomalies, January-December

Long description


  • Global temperature continues to rise; each of the last three decades has been successively warmer than any preceding decade since the 1850s.
  • Warming is not uniform; temperature in Canada has been increasing at roughly double the global mean rate. The Arctic is warming even faster.

Other indicators of a warming planet

Arctic summer sea ice extent

Arctic summer sea ice extent

  • Snow, sea ice, glaciers and permafrost are in decline, consistent with observed warming.

Global average sea level

Global average sea level

IPCC AR5, Summary for Policymakers (WG1), Fig. SPM.3

Long description


  • Global average sea level has risen about 20 cm since 1900 due to expansion of warming ocean waters and the addition of water to the ocean from melting land ice.

Impacts have been observed globally – climate change will amplify existing risks and create new ones

  • Evidence is strongest in natural systems (blue and green).
  • Impacts on human systems (red) include food production, local livelihoods and health.

Map of world showing observed impacts attributed to physical, biological, human and managed systems

Bars represent quantity of evidence

IPCC AR5, Synthesis Report, Summary for Policymakers, Fig. SPM.4

Long description


Observed changes in Canada: Consistent with global changes

  • Longer growing season
  • More heat waves and fewer cold spells
  • Thawing permafrost
  • Earlier river ice break-up
  • Increase in precipitation over large parts of Canada, more snowfall in northwest Arctic
  • Earlier spring runoff
  • Earlier budding of trees
  • Indigenous people of the Arctic are no longer able to predict the weather as their forefathers did (Society for Ecological Restoration).

Canadian Temperature Trends – 1948 to 2012

Canadian temperature trends - 1948-2012

Long description


Canada is already warmer, wetter and stormier




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