The Alberta oil sands and climate

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The US federal government recently rejected approval for TransCanada's proposed Keystone XL pipeline. But TransCanada plans to submit a revised proposal shortly. The proposed pipeline is part of a US$13 billion system aimed at connecting the bituminous oil sands in Alberta, Canada with refining capabilities in the United States, including those as far south as Texas1. There has been widespread public interest in, and opposition to the pipeline, primarily owing to environmental concerns (for example, ref. 2). Similar public opposition has arisen towards the proposed Northern Gateway pipeline in British Columbia, which aims to make the oil sands accessible to Asian markets.

The size of the Alberta oil-sand deposits is massive. Estimates for oil-in-place are 1.8 trillion barrels3, although the economically viable 'proven reserve' is estimated at only around 170 billion barrels with 26 billion barrels under active development3. For orientation, Alberta's 1.8 trillion barrels of oil-in-place is roughly seven times the size of Saudi Arabia's proven reserves4. It has been suggested that construction of the TransCanada pipeline will encourage an expansion of the area under active development2. Indeed, greenhouse-gas emissions resulting from expanding oil-sand production are Canada's fastest-growing emissions source5, and have the potential to contribute significantly to anthropogenic climate change. This is accentuated by the fact that the oil sands are more energy intensive to produce than conventional crude oil — and have a greater 'well-to-wheel' carbon footprint6 (see Supplementary Information).

Global warming



Table 1 Oil-sand potential for global warming in the context of global fossil-fuel resources.



Carbon footprints



Recent estimates show that an enormous global fossil-fuel total resource base is available to meet this growing demand11 (Table 1). Resources here are defined as those fossil fuels in the Earth's crust for which “economic extraction is potentially feasible”11 — an upper limit of nature's bounty and human techno-economic ability. Coal resources have the largest potential for global carbon emissions (79% of the total), followed by unconventional gas (15%) and only then the unconventional oil of which the Alberta oil sands form a part (3%; Fig. 1). Coal's significance is due to the large tonnage available, together with its high carbon content. It is clear that the total global fossil-fuel resource base could easily yield over 2 °C of warming given sufficient global demand and a lack of international regulation.

Figure 1: Central estimate of the potential for warming of the different fossil-fuel resources in Table 1.

The red line indicates the limit of 2.0 °C warming from pre-industrial times agreed to under the Copenhagen Accord. Note, that here we only consider the effects of anthropogenic carbon dioxide. The potential for warming associated with proven Alberta oil-sand reserves is indicated as a barely visible sub-component (shown in pink) of unconventional oil (global). The potential warming of the total Alberta oil-sands oil-in-place (OIP) is shown in black. *The carbon–climate response method is not valid for emissions above about 20×1017 g C, so these figures are not valid climate change estimates, but are included for comparison.



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Correspondence to Andrew J. Weaver.

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Supplementary Information (PDF 428 kb)

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