What is Climate Change?
Scientific Background on Climate Change
The scientific community has come to a consensus that global warming (or climate change) is indeed occurring as a result of human activity[i], and has warned of the potential of a number of negative outcomes. 2010 tied as the warmest year on record[ii] and the Earth’s average temperature has warmed by nearly 1 degree Fahrenheit since 1976, while 20% of the polar ice cap has melted since the 1970s. [iii]
Human activities influence global warming in two distinct ways—through the emission of greenhouse gases, and through changes to the earth’s surface that result in lowered greenhouse gas absorption. The term ‘greenhouse gases’ (GHGs) is related to the concept of the greenhouse effect. GHGs trap heat from the sun within the Earth’s atmosphere; warming the Earth just enough to support life—without the greenhouse effect, the average temperature on Earth would be around -19 degrees Celsius. GHGs have historically been absorbed by natural “carbon sinks”, mostly plants and forests which absorb carbon dioxide (CO2) as part of their natural growing process.Increasing deforestation and urban development have decreased the amount of GHGs being absorbed while at the same time, human activity has dramatically increased the amounts of GHGs entering the atmosphere, leading to a large net gain in GHGs in the atmosphere which then trap increasing amounts of heat—slowly warming the planet.
Greenhouse Gases (GHGs)
One often hears global warming described in the context of carbon dioxide (CO2). In fact, CO2 is only one of six major GHGs for which there is concern. The six primary GHGs are (1) carbon dioxide (CO2), (2) methane, (3) nitrous oxide (NO) and the fluorinated gases: (4) sulfur hexafluoride, (5) hydroflurocarbons (HFCs) and (6) perfluorocarbons (PFCs). GHGs are often described in terms of “carbon equivalents”, to ensure a standard methodology of measurement. As the occurrence of global warming has become validated by the scientific community, and the need to mitigate the effect has been widely recognized, increasing scrutiny has been placed on those industries that are responsible for the greatest amounts of CO2 equivalents.
The most widely recognized and largest source of CO2 is the burning of fossil fuels. The largest growth in global GHG emissions between 1970 and 2004 has come from the energy supply sector (an increase of 145%).[iv] Beyond the energy sector, a range of different activities contribute to climate change. Learn more about the healthcare sector’s contribution to climate change at How Healthcare Affects Climate Change.
