Canada’s GHG Emissions: Do changes year by year mean anything?

Dr. John G. Hollins, past Chair CACOR Board of Directors, examines Canada’s GHG emissions.

This note provides an assessment of the significance of the annual changes reported by Canada. 

Environment Canada submits an annual report to the United Nations Framework Convention on Climate Change (UNFCCC) on Canada’s emissions of greenhouse gases (GHG) a year or more after the fact [ii].

All facilities with emissions over 10 kilotonnes CO₂ equivalent[1]/year are required to report their emissions of GHG during the following year.  Four methods of calculating these emissions are accepted.[2]   Environment Canada states that it does quality control, but it does not report on its quality control.

Quantities derived by calculation are more susceptible to error than direct measurements.  Even when CO₂ is sampled in the flue of a coal-fired power station, for example, the total is calculated using other parameters.

The method of calculating emissions from the combustion of fuels is not described, but is presumably based on reporting by Statistics Canada, for example, volumes of motor fuels.  These are probably accurate.

Canada’s annual submissions to the United Nations are reported in the media and by interested parties. The change from the previous year is featured, especially if it has increased.  Changes from multiple earlier years are not usually mentioned.

No estimates of variance are provided, so it is not possible to know directly from these reports whether the year-over-year changes are significant or not.

Canada’s annual emissions

Here is a graph of the annual emissions reported by Canada from 1990 to 2017.

Drop

The most notable feature of this graph is the drop between 2007 and 2009 of almost 8%.  A trained statistical eye would conclude that this decline was probably statistically significant and, remembering the Kaya Identity, relate it to the financial crisis of 2008.

Kaya Identity

Canada’s GDP growth was lower than normal in 2008 (+1%) but declined only in 2009 (-3%), so that’s a partial explanation.

Before and after the drop

What about the other year-over-year changes? 

The graphic below provides the change in emissions in a given year from the previous year for two sets of five years:  preceding and following the drop.  The average change year-over-year for these ten years was +3 Mt CO2e/y and the variance was ±12 Mt CO2e/y (one standard deviation). This is a classic case of the problem of calculating small differences between large numbers.

In three of these ten years, the year-over-year change is larger than one standard deviation (33% probability of that happening), in one year the change is almost two standard deviations (5% probability).

Conclusion

Presentation of, and especially argument about changes between one year and the previous year are meaningless.  The answer to the question in the title is no.

Canada’s emissions between 2003 and 2016, leaving out the drop in 2008 and 2009, were essentially stable. Following the drop, they recovered quickly to roughly what they had been.

In establishing potential pathways for Canada to meet its 2030 Paris commitment and beyond, CACOR’s Pathways Project has deliberately looked out 50 years. Understanding the history also requires long approach.

[1] 

The power of all greenhouse gases are reported in the equivalent power of carbon dioxide, the principal greenhouse gas emitted by human activity.

[2] 

1. Monitoring or direct measurement;
2. Mass balance;
3. Emission factors;
4. Engineering estimates.

[i]  Dr. Hollins taught Physics101, which includes the statistics of measurement, as a sessional lecturer in the Physics Department of Carleton University.  He is Past Chair of the Canadian Association for the Club of Rome.  The views presented here are his.

[ii]  All the data in this paper were taken from Environment Canada.