Greenhouse Gasses and Climate Change

The global community has become increasingly aware of the concerns that the build-up in the atmosphere of greenhouse gasses, 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 degrees C. 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 degrees 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 degrees. At this temperature, essentially all of the waves radiated outward by the earth are infrared, with wavelengths ranging from 4 to 100 micrometers. Some gasses 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 megatonnes of carbon dioxide. In 2014, it was refitted with a more efficient turbine and a scrubber designed to remove up to 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 became operational in October 2014 and is the first power plant in the world to capture and store carbon dioxide. SaskPower estimates that in 2016 it will achieve the capture of 800,000 tonnes. 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. In preparation for the COP 21 meeting in Paris in 2015, the federal government announced a new target of 30% reduction by 2030. The international agreement reached at the Paris meeting calls for a goal of limiting global temperature increase to less than 2 degrees C, and in fact aiming for 1.5 degrees. The most recent report of the Intergovernmental Panel on Climate Change states that the world needs to decrease emissions by an estimated 40% to 70% by 2050 and essentially 100% by 2100 to achieve even the more modest 2-degree target. Canada’s performance has so far been woefully inadequate. In fact, after a dip associated with the 2008 recession, our total emissions have continued to rise in spite of our declared goals. Environment Canada estimates that our 2020 emissions are likely to be approximately equal to the 2005 level rather than 17% less. It is our responsibility to make our government aware that although we are not likely to meet this target, we expect the current administration to honour or even exceed the 30% reduction promised for 2030.

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, revised February 2016

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