Kyoto Protocol greenhouse gases and the Canadian Environmental Protection Act: chapter 2

2. IPCC Conclusions on Current and Future Climate Changes of Relevance to CEPA

By the operation of Sections 64 and 90 of CEPA, a substance can be recommended for addition to Schedule 1, thus allowing the enactment of preventative or control measures, if it is entering or may enter the environment in a quantity or concentration or under conditions that:

  1. have or may have an immediate or long-term harmful effect on the environment or its biodiversity;
  2. constitute or may constitute a danger to the environment on which life depends; or
  3. constitute or may constitute a danger in Canada to human life or health.

The question then is whether human emissions of GHGs have consequences that meet one or more of the criteria above.

GHGs, upon being emitted to the atmosphere, alter its composition, thereby affecting its chemical and physical properties. The radiative properties of GHGs, and the role GHGs play in the energy balance of the Earth, are well established. GHGs in the atmosphere produce a "greenhouse effect" which describes the role of the atmosphere in insulating the planet from heat loss. Indeed, without the natural greenhouse effect produced by GHGs of natural origin, the average temperature of the Earth would be approximately 33 °C colder than it is. The term 'enhanced greenhouse effect' is the term used to describe the augmentation of atmospheric concentrations of GHGs as a result of human activity.

This report will determine whether human emissions of GHGs, by enhancing the natural greenhouse effect, are harmful according to the criteria set out in Section 64 of CEPA.

If it can be shown that the climate of the Earth has changed recently and that human emissions of GHGs have been a contributing factor, then it will be determined whether or not these changes have been harmful as defined by the criteria set out in CEPA 1999 Section 64. If it can also be shown that continuing human emissions of GHGs will lead to further climate change, then it will be determined whether or not there will be harmful or dangerous consequences in the future as defined by the criteria set out in Section 64 of CEPA 1999.

Collectively, the body of evidence that responds in great detail to these questions is contained within the full technical reports of Working Groups l (Science) and ll (Impacts, Adaptation and Vulnerability) of the IPCC3. The evidence is synthesized and presented in question and answer format in the IPCC Synthesis Report4. Below, a summary is presented of the conclusions from the IPCC TAR that responds to the issues of observed climate change and its causes, and future climate change. In Section 3 of this report, evidence from the IPCC TAR, on the impacts of climate change, will be presented that is most relevant within the context of CEPA Section 64.

2.1 Observed Climate Change and its Causes

The detailed supporting evidence for this summary is presented in Tables 1 and 3 of Annex A.

The Earth's climate has changed since the pre-industrial era. Over the 20th century, the global average surface temperature has increased by 0.6 °C with a very likely* confidence range of 0.4-0.8 °C. It is very likely that the 1990s was the warmest decade, and 1998 the warmest year, of the instrumental record. It is likely that the 20th century warming, at least that of the Northern Hemisphere, is unprecedented during the past 1000 years. The warming has been accompanied by a suite of other changes in the climate system that, together, give a collective picture of a warming world. Most of the warming of the past 50 years is likely to have been due to increases in greenhouse gas concentrations. Concentrations of atmospheric GHGs and their radiative forcings have generally increased over the 20th century as a result of human activities. The rates of increase for carbon dioxide and methane are unprecedented.

On the basis of these conclusions, and for the purpose of considering GHGs under CEPA Section 64, it is valid, as will be done in Section 3, to consider whether there is any evidence of harm from current impacts, arising from recent climatic changes.

2.2 Future Climate Change

The detailed supporting evidence for this summary is presented in Table 2 of Annex A.

It is clearly demonstrated that the amount of future global warming will be dependent on the amount of greenhouse gas from human activity that is emitted in the future. The aggregate quantity of emissions in the future will be influenced by development choices made by individual countries worldwide. That said, carbon dioxide concentrations, globally averaged surface temperature and sea level are projected to increase under all IPCC emission scenarios during the 21st century5. The projected warming of 1.4 - 5.8°C over the period 1990 to 2100 is very likely to be without precedent during the last 10,000 years. Global mean sea level is projected to rise between 10 and 90 cm by the end of this century. There will be regional differences in warming, but it is very likely that nearly all land areas will warm more rapidly than the global average, and that high latitudes will warm the most. The earth's cryosphere (snow, ice and permafrost) will continue to respond to the warming. The widespread retreat of glaciers and ice caps is projected to continue, as is the decrease in snow cover, permafrost and sea-ice extent.

On the basis of these conclusions, and for the purpose of considering GHGs under CEPA section 64, it is valid, as will be done in Section 3, to consider whether there is any threat of harm from future impacts arising from future climate change.

2.3 IPCC Lexicon for Statements of Confidence and Likelihood

Given that the evidence presented in the following sections has been extracted from the Third Assessment Report of the Intergovernmental Panel on Climate Change, knowledge of the IPCC lexicon around likelihood and confidence statements is necessary. The likelihood descriptors were used by IPCC WGI while the Confidence Descriptors were used by IPCC WGII. The IPCC lexicon is as follows:

Likelihood Descriptor % Chance That Statement is True
Virtually certain >99%
Very likely 90-99%
Likely 66-90%
Medium likelihood 33-66%
Unlikely 10-33%
Very Unlikely 1-10%
Exceptionally unlikely <1%

Confidence Descriptor % Confidence
Very high 95% or greater
High 67-95%
Medium 33-67%
Low 5-33%
Very Low 5% or less

The decision to assign a level of probability or confidence to a finding represented the collective judgment of the IPCC authors, based on the observational evidence, modeling results and theory that were examined. In this report, where these terms are used in findings attributed to the IPCC, the criteria above should be assumed to apply.

* See discussion of IPCC lexicon on confidence and likelihood statements at the end of this section.

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