Greenhouse Gases and Climate Change

The global community has become increasingly aware of the concerns that the build-up in the atmosphere of greenhouse gases, in particular carbon dioxide, is leading to catastrophic warming of the earth.  In its latest report, Working Group III of the Intergovernmental Panel on Climate Change have predicted that without additional efforts to reduce emissions beyond those in place today, the temperature of the earth in the year 2100 is likely to have increased over pre-industrial levels by a figure in the range 3.7 to 4.8  ⁰C. So what is going on here and why the concern about carbon dioxide?

The earth receives energy from the sun in the form of electromagnetic radiation, or light waves. The energy is transmitted over a range of wavelengths from ultraviolet to infrared, with a peak value determined by temperature.  The temperature of the sun is nearly 6000  ⁰C and the peak is in the visible portion of the spectrum.  Some of this radiation is reflected away, but much passes through the atmosphere to be absorbed by the earth. The earth itself radiates energy and the balance between energy absorbed and energy released has resulted in an equilibrium average global temperature of about 15   ⁰C. At this temperature, essentially all of the waves radiated outward by the earth are infrared, with wavelengths ranging from 4 to 100 micrometers.  Some gases in the atmosphere are efficient at absorbing this infrared radiation and re-emitting it in all directions, including back to the earth where it contributes to warming.  Water strongly absorbs in the range 4 to 7 micrometers and carbon dioxide in the range 13 to 19 micrometers. There is a window between 7 and 13 micrometers though which about 70% of the earth’s radiant energy escapes.  But the balance is delicate. Global warming is real and can be linked to the increase in concentration of carbon dioxide resulting from deforestation and burning of fossil fuels. The problem with carbon dioxide is that, unlike water vapor, once it is in the atmosphere it hangs around for a long time. Even if all emissions stopped tomorrow it would take hundreds of years for recovery to pre-industrial levels.  

The world will unfortunately continue to rely on fossil fuels for many years. Does this mean that catastrophic climate change is inevitable? Not necessarily. There are some strategies that can buy us time as the world converts to alternative energy sources. One emerging strategy is carbon capture and storage.  The Province of Saskatchewan is taking a lead in this area.  SaskPower’s Boundary Dam unit #3 is Canada’s largest coal-fired plant, generating 110 megawatts of electricity. Each year it emits 1.1 million tonnes of carbon dioxide.  In 2014, it is being refit with a more efficient turbine and a scrubber to remove 90% of the carbon dioxide from its effluent.  The process involves passing the flue gasses through a solvent that binds to the carbon dioxide while allowing other effluent gasses to escape. The solvent is drawn off and heated to release the carbon dioxide.  The recovered gas is then compressed and pumped to the nearby Weyburn oilfield and Deadwater saline aquifer for storage underground. The refit unit is expected to be operational in the summer of 2014 and will be the first power plant in the world to capture and store carbon dioxide.  A second plant is under construction in The US and the UK has plans to convert a gas-fired plant in the near future.  Underground storage is currently the only technology capable of eliminating gigatonnes of carbon dioxide per year.

Does this mean that we can be complacent about climate change? The answer is a definite NO.  At most, carbon capture and storage is a temporary solution and only a partial solution. We need to spend more on innovation and technology. As individuals we have a responsibility to reduce our own reliance on fossil fuels. We also have a responsibility to hold our governments at all levels accountable for their actions. In 2009, our federal government signed on in Copenhagen to the UN Framework Convention on Climate Change, by promising that our annual greenhouse gas emissions in the year 2020 will be 17% less than our 2005 levels. This is grossly insufficient. The recent report of the Intergovernmental Panel on Climate Change says the world needs to decrease emissions by an estimated 40% to 70% by 2050 and 100% or more by 2100 if we want to hold the global temperature increase to less than 2 degrees C.  Canada ‘s promised 17% reduction is inconsistent with this recommendation.  Our target is approximately 600 megatonnes total emissions in 2020. In October 2013, Environment Canada estimated that our 2020 emissions are likely to be over 700 megatonnes, in fact approximately equal to the 2005 level rather than 17% less. It is our responsibility to make our government aware that we expect it to keep its declared promise on reductions and to develop a strategy to reduce emissions even further than our current target.To date there has been no significant regulation of the oil and gas sector of our economy. This is the one sector that is projected to significantly increase its emissions from 2005 to 2020, in large part due to an estimated 67 megatonne increase associated with the production of bitumen from tar sands.

Sources:

The Greenhouse Effect, J and M Gribbin, NewScientist, 6 July 1996|
IPCC-WGIII-AR5-SPM,  April 2014
Trailblazing Power Plant, C Brahic, NewScientist,  5 March 2014
Canada’s Emission Trends, Environment Canada, October 2013

Jim Corbett
April 2014

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