Article 2, Section 1a of the 2015 Paris Agreement on climate change (UNFCCC, 2015), to which Canada is party, adopted as its goal, “Holding the increase in global average temperature to well below 2⁰C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5⁰C above pre-industrial levels”. As a first and far from adequate step toward staying below these temperature limits, various nations of the world “pledged” to make various reductions in greenhouse gas (GHG) emissions by 2030, either relative to some past level or relative to some hypothetical future emission scenario. Canada pledged to reduce its emissions by 30% relative to the 2005 level by 2030. Were all nations of the world to follow through on their Paris pledges, the net effect would be to stabilize global GHG emissions at a level about 30% above the 2005 level (Fawcett et al., 2015).
There is, however, no simple relationship between emission reductions and temperature warming. The amount of warming by a given time depends on three key factors: (a) the increase of GHG concentrations in the atmosphere, (b) the “climate sensitivity”, and (c) the delay effect as heat (trapped by increasing GHG concentrations) goes into warming the subsurface ocean rather than the surface climate. The increase in CO2 concentration (the primary and most long-lasting GHG of concern) depends on cumulative emissions and the amount absorbed by various “sinks”, primarily the terrestrial biosphere and the oceans. The oceanic absorption involves multiple processes that kick in at multiple time scales, ranging from months to 1000s of years. The climate sensitivity can be thought of as where the climate is heading for a given increase in GHG concentrations, and is, by convention, referred to as the amount of warming for a fixed, doubling of the CO2 concentration or for the heat-trapping equivalent of a CO2 doubling when many GHGs increase in concentration (as is happening in reality). The climate sensitivity depends on various feedbacks (mostly positive) between the initial heat trapping and various climate variables (such as the amount of water vapour in the atmosphere, the extent of snow and ice, and a bewildering array of cloud properties). The greatest uncertainty revolves around cloud feedbacks, which depend on the spatial patterns of surface warming. These patterns, and hence the net cloud feedback and where the climate seems to be heading for a given GHG increase, change over time because the absorption of heat by the oceans is strong in some regions (such as where there is deep downward mixing of surface water) and weak in others; thus, some regions approach their eventual warming (for an eventual stabilized set of GHG concentrations) quickly and some regions approach it slowly, which causes spatial differences in the amount of warming to change over time. Many coupled atmosphere-ocean climate models indicate that the net effect is that during the early stages of the transition to a warmer climate, the climate system warms by an amount consistent with a rather low climate sensitivity (1.5-2⁰C for a CO2 doubling equivalent), but that the true and much larger climate sensitivity (where the climate is heading) emerges later on.
In sum, then, the oceans play three key roles in determining how much warming we get for a given global CO2 emission scenario: by absorbing some of the CO2 that humans emit, by delaying the overall warming at a given time, and by altering the apparent eventual warming itself by distorting the patterns of climatic change and thereby altering the cloud feedbacks.
On the flip side, there are several direct and indirect impacts of GHG emissions on the oceans: effects on marine biota through warming, through changes in the availability of nutrients caused by changes in winds and vertical mixing of waters, through changes (reductions most likely) in oxygen concentration caused by warming and changes in mixing, and through multi-faceted changes in ocean chemistry as the oceans absorb CO2. To these can be added effects on coastal regions through sea level rise induced by heating of ocean waters and melting of land-based ice.
Back to the Paris Agreement: The only targets in the agreement are the afore-mentioned global mean temperature targets. The only reference to oceans is in the preamble to the agreement, which reads, “The Parties to this Agreement … Noting the importance of ensuring the integrity of all ecosystems, including the oceans ….Have agreed as follows …”. However, from the temperature targets, science can be used to back-calculate emission scenarios that are consistent, with varying degrees of probability, with the 1.5⁰C and 2.0⁰C temperature targets. The bottom line is that to have a mere 60% chance of staying below the more lenient 2.0⁰C target (I say “mere” because no-one would fly with survival odds that low), global CO2 emissions need to be reduced to zero by around 2060 (Rogelj et al., 2015). Conversely, if national pledges were strengthened merely enough to maintain constant global emissions (in the face of continuing economic growth) after 2030 (when the current agreement expires), the estimated probability of staying below 2.0⁰C warming is only 7%, while there would be an 8% probability of a catastrophic 4⁰C warming (Fawcett et al., 2015).
While touting its commitment to addressing the real threat of catastrophic climatic change, the Canadian government is actively promoting expansion of one of the most carbon-intensive sources of oil on Earth: the tar (or oil) sands of Alberta and Saskatchewan, most recently through the outright purchase of an oil pipeline (the Kinder Morgan transmountain pipeline) for $4.6 billion that its private-sector owners seemed willing to abandon, and the commitment to spend an even larger sum of public money to triple its capacity. However, simple arithmetic shows that to have even a modest chance of complying with Canada’s Paris pledge, it is not merely sufficient to freeze tar sands operations at their current levels. Rather, tar sands oil production will need to be phased out altogether (along with elimination of coal for electricity generation nationwide and shelving of plans for LNG exports) (Harvey and Miao, 2018). And if the world goes just half way toward eliminating fossil fuel emissions (and hence, demand for oil), the international price for oil would be permanently depressed ($50/barrel or less), which would render investment in pipelines and tar sands expansion a guaranteed money loser (Harvey, 2017). With a fossil fuel phaseout by 2060 – something that could be done if there were the political will to do so – a more likely long term price of oil is $30/barrel.
To conclude, the science indicates severe impacts on human and natural systems, including the oceans, associated with current emission trajectories, and substantial impacts even if the Paris targets are achieved. These impacts in turn have significant ethical implications. Addressing these concerns requires the elimination of fossil fuel use, and its complete replacement with renewable energy, by mid-century, which renders long-term investments in new fossil fuel infrastructure a guaranteed money loser; for these investments to be profitable, one has to hope for a bleak future indeed for our children. Government climate and energy policy should therefore be based on three pillars: best-available science, rigorous ethical reasoning, and sound economics. On all three grounds, current Canadian Federal (not to mention most provincial) policies related to climate and energy fall far short of what is required. Unfortunately, Canada is not alone in this failure. One can only hope that the three pillars of science, ethics and economics will be taken seriously at the upcoming G7 summit on climate, oceans, and clean energy.
Fawcett AW et al. 2015. Can Paris pledges avert severe climate change? Science 350:1168-1169.
Harvey, LDD. 2017. Implications for the floor price of oil of aggressive climate policies. Energy Policy 108, 143-153.
Harvey, LDD and Miao, L. 2018. How the oil sands make our greenhouse gas targets unachievable. Policy Options. 2 January 2018. http://policyoptions.irpp.org/magazines/january-2018/how-the-oil-sands-make-our-ghg-targets-unachievable/
Rogelj J, Schaeffer M, Meinshausen M, Knutti R, Alcamo J, Riahi K, Hare W. 2015. Zero emission targets as long-term goals for climate protection. Environ. Res. Lett. 10, 105007.
UNFCCC, 2015. The Paris Agreement. https://unfccc.int/sites/default/files/english_paris_agreement.pdf (accessed on 10/09/2018)