Updated CMOS Position Statement on Climate Change

The process of revising the CMOS position statement on climate change:

In August 2019, the CMOS Council approved a revised position statement on climate change. The previous statement dated from 2014 and important developments in the science of climate change had occurred in the intervening years. In particular, the 2018 release of the Intergovernmental Panel on Climate Change’s Special Report on 1.5 C and the 2019 release of Canada’s Change Climate Report (CCCR). CMOS members made important contributions to these assessment reports, and they have important implications for Canadian society. The revised statement (below, and on the CMOS website) is designed to highlight these and communicate the basic physical science of climate change.

The CMOS Scientific Committee undertook the revision in spring 2019, after CCCR was published. The committee surveyed the climate change statements of other professional societies. There was a consensus that the shorter statements were more effective to communicate to the public and policymakers: less is more. The committee established a goal of an approximately two-page statement in the form of a list of bullet points. The latter choice was inspired by the Canada’s Changing Climate Report “Headline Statements”, an excellent distillation of the lengthy underlying report. To make explicit that the CMOS statement on climate change builds on extensive national and international assessment reports, which include the references to underlying peer-reviewed publications, there are links to the web addresses of four reports.

After the Scientific Committee co-chairs Timothy Merlis and Clark Richards produced a draft statement, the majority of Scientific Committee members and several CMOS Councilors offered suggestions for revision to ensure the statement was clear and precise. This drew on the broad scientific expertise of the Scientific Committee and the experience of the past Scientific Committee chair Adam Monahan, who led the writing of the previous statement. In the process of producing a shorter, hopefully more effective statement, some existing material was removed. This is a delicate balance and subsequent statements may be longer to include new developments or science that become prominent in public discourse. At the moment, our view is that the highest priority for CMOS is to effectively communicate the basic science of anthropogenic climate change and its impacts on Canada.


[This position statement was authored by the Scientific Committee of CMOS, and approved by CMOS Council on August 26, 2019.]

The Canadian Meteorological and Oceanographic Society (CMOS) is a national society of individuals and organizations dedicated to advancing atmospheric and oceanic sciences, as well as related environmental disciplines. CMOS has more than 700 members from Canada’s major research centres, universities, private corporations, and government institutes. CMOS is uniquely positioned to provide scientific information to Canadians on the science of climate change. Many of its members are internationally recognized scientists who are extensively involved in comprehensive assessments of the current state of knowledge with respect to this complex issue. Such assessments require atmospheric and ocean scientists working together with scientists in related environmental, social, and economic disciplines to advise policymakers and the public on climate change.

This statement on the science and implications of climate change draws on national and international assessment reports, such as Canada’s Changing Climate Report (2019), the World Meteorological Organization Statement on the state of the global climate in 2018 (2019), the United Nations Intergovernmental Panel on Climate Change Special Report Global Warming of 1.5° C (2018), and the United Nations Intergovernmental Panel on Climate Change Fifth Assessment Report (2013). These reports include references to underlying peer-reviewed scientific literature upon which this statement is based.

  • Earth’s climate—arising from the interaction of the atmosphere, ocean, ice, land surface, and living things—undergoes changes from both human activity and natural causes.
  • Knowledge of climate change is based on observations of the climate and scientific understanding of physical, chemical, and biological processes.
  • Humans influence the climate through changing the atmosphere’s composition, primarily through emissions of greenhouse gases as a result of combustion of fossil fuels and deforestation. Carbon dioxide (CO2) is the dominant human-emitted greenhouse gas. The current CO2 concentration is approximately 50% above the pre-industrial levels.
  • Human activity has been the main cause of the observed increase in temperature since the middle of the 20th century. The four recent years (2015-2018) have been the warmest years on record for global surface temperature. A long-term warming will continue in the 21st century, although individual months or years will also be affected by natural climate variations.
  • Changes in climate result in responses in average and extreme temperature and precipitation, as well as in wind, sea level, snow and ice cover. There are also numerous other responses, such as ocean acidification and deoxygenation. Many of these responses, including those attributed to human activity, have already been observed and are predicted to continue in the future.
  • Change has both global (e.g., increasing surface temperature) and regional (e.g., reduction of Arctic sea ice) effects. Important effects specific to Canada, drawing on Canada’s Changing Climate Report 2019 include the following:
    • Warming in Canada is, on average, about double the magnitude of global warming. Northern Canada has warmed and will continue to warm at more than double the global rate.
    • The effects of warming in Canada include more extreme heat, less extreme cold, longer growing seasons, increased precipitation in most areas, increased wildfire risk, shorter snow and ice cover seasons, earlier spring peak streamflow, thinning glaciers, thawing permafrost, increased coastal erosion, rising sea level, and more frequent coastal flooding.
    • Canadian areas of the Arctic and Atlantic Oceans have experienced longer and more widespread sea ice-free conditions. Canadian Arctic marine areas, including the Beaufort Sea and Baffin Bay, are projected to have extensive ice-free periods during summer by mid-century. The last area in the entire Arctic with summer sea ice is projected to be north of the Canadian Arctic Archipelago.
    • Because some further warming is unavoidable as a result of past and present emissions, these trends will continue over the next century.
  • Future climate projections are based on scientific understanding of physical, chemical, and biological processes that affect climate and estimates of future human activity. There is uncertainty in projections that results from both incomplete scientific understanding and uncertain future human activity. Reducing the uncertainty that arises from incomplete scientific understanding of climate change and quantitatively assessing natural climate variations are core professional goals of many CMOS members.
  • A range of future human greenhouse gas emission scenarios are used to inform climate change impact assessment, climate risk management, and policy development. Important climate change effects associated with various emission scenarios are summarized below.
    • With current emission reduction plans and commitments, the future temperature and sea level changes are likely to result in averaged surface temperature increases of 4-6 °C for Canada (even higher for northern regions) and coastal sea level rises approaching 1 metre for some populated parts of Canada by the end of the century.
    • High emissions scenarios, which closely mirror today’s business as usual emissions, will have substantially more future climate change effects than this.
    • Scenarios with limited warming will only occur if Canada and the rest of the world reduce net carbon dioxide emissions to near zero early in the second half of the century and reduce emissions of other greenhouse gases substantially. To limit global warming to 1.5°C by 2100, projections indicate we must achieve net zero emissions globally by approximately 2050.

CMOS strongly endorses the results of the recent Government of Canada’s Changing Climate Report, and, in collaboration with researchers, citizens, governments and industry, stands ready to work collectively toward rapid decarbonization of the economy and investment in renewable energy sources. CMOS is also committed to assisting Canadians learn how to adapt to the climate changes to which we are already committed, for both present and future generations.

More like this:

Canada’s Changing Climate Report, CCCR, climate projections, CMOS Scientific Committee, Position Statement

For previous issues go to the Archives page on the main CMOS site.

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