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Updated Statement on Global Warming of 1.5°

CMOS Statement on the IPCC Special Report on Global Warming of 1.5°C

November, 2018

The Canadian Meteorological and Oceanographic Society (CMOS) is the national society dedicated to advancing atmospheric, oceanic, and related environmental sciences in Canada. CMOS has more than 800 members from Canada’s major research centres, universities, private corporations and government institutes. CMOS is uniquely positioned to provide expert advice to Canadians on the science of climate change. Many of its members are internationally recognized scientific experts who are extensively involved in comprehensive assessments of the current state of knowledge with respect to this complex issue.

This position statement is intended to summarize and reflect CMOS’s views on the IPCC Special Report entitled ‘Global Warming of 1.5°’, which was approved by IPCC in October 2018.  The report was prepared in response to the invitation by the Conference of the Parties to the United Nations Framework Convention on Climate Change (UNFCCC) articulated in its decision to adopt the Paris Agreement in December 2015. Under the Paris Agreement, 195 nations committed to “holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels”. While several studies had explored the avoided impacts and emission reduction implications of limiting warming to 2°C, little was known about the 1.5°C limit.

The special report assesses the available scientific, technical and socio-economic literature relevant to global warming of 1.5°C. It presents findings about the current state of the climate system relative to 1.5°C, the impacts that would be avoided by limiting warming to 1.5°C compared to 2°C, the greenhouse gas emission pathways and systems transitions required to keep warming below 1.5°C, and implications for sustainable development and poverty eradication.

Where do we stand now?

Human activities are estimated to have caused approximately 1.0°C of global warming above pre-industrial levels in 2017. This means that anthropogenic global warming caused by greenhouse gases and other forms of pollution has brought us to within 0.5°C of the 1.5°C limit. At the current warming rate, global warming is likely to reach 1.5°C between 2030 and 2052, with a best estimate of 2040. Current global warming will persist from centuries to millennia and will continue to cause further long-term changes in the climate system, such as sea level rise. However, past emissions alone are unlikely to cause global warming of 1.5°C.

The observed warming is not evenly distributed. In particular, land regions like Canada have experienced warming greater than the global mean, including two to three times higher in the Arctic.

Why stay at the 1.5°C global warming limit?

Human-induced warming has already caused detectable changes in the climate system with impacts on ecosystems, as well as human systems and well-being. Many of these impacts and associated risks will be exacerbated at the 1.5°C limit. Projected climate changes at 1.5°C include an increase in hot extremes in most inhabited regions, and increased frequency and intensity of both heavy rainfall events and drought in several regions.

Climate model simulations show stark differences in impacts and associated risks between 1.5°C and 2°C. If we avoid the 2°C limit and stay below the 1.5°C limit, we expect to see a wide range of benefits, including:

  • Reduced risks from droughts and heavy rainfall events
  • 10 cm less global mean sea level rise by 2100, with up to 10 million fewer people exposed to sea level rise-related risks
  • Reduced impacts on biodiversity and ecosystems, including species loss and extinction
  • Reduced increase in ocean temperature and ocean acidity and reduced decrease in ocean oxygen levels, implying reduced risks to marine biodiversity, fisheries and ecosystems and their services to humans
  • Substantially lower probability of a sea-ice-free Arctic Ocean in the summer
  • Higher probability of saving some coral reefs
  • Lower risks for heat-related and ozone-related mortality
  • Smaller net reductions in yields of maize, rice, wheat and potentially other cereal crops, and in the nutritional quality of rice and wheat
  • Up to 50% fewer people around the world exposed to a climate change-induced increase in water stress


What can we do to stay below the 1.5°C global warming limit?

Limiting global warming requires staying within a carbon emissions budget. The current global emission rate of carbon dioxide (CO2) is about 40 billion metric tonnes per year (more precisely, 42 GtCO 2 per year). The report estimates that we only have 10-15 years of emissions at the current rates before we burn through this budget. In order to avoid exceeding the 1.5°C limit, net CO2 emissions must be cut by about half by 2030, reaching effectively zero (accounting for anthropogenic CO 2 removals) around 2050. Furthermore, emissions of methane and black carbon need to be cut. 

Achieving these reductions – which is known as mitigation - requires rapid and far-reaching transitions in energy systems, land use, urban planning, infrastructure (including transport and buildings), and industry. The scale of these systems transitions is unprecedented, and implies deep emissions reductions in all sectors. It will open up a wide range of choices for how to invest in different mitigation options.

The report argues that staying within the 1.5°C limit requires, along with emissions reductions, carbon dioxide removal (CDR) from the atmosphere through human interventions such as afforestation. Large-scale CDR is highly challenging and potentially unsustainable, and will have to be increasingly relied on if emissions reductions are delayed.

The benefits of limiting warming to 1.5°C for sustainable development 

Limiting warming to 1.5°C benefits efforts towards sustainable development and poverty eradication, for example through benefits towards food production, availability of clean water and human health. Limiting warming to 1.5°C can have benefits for sustainable development and poverty eradication if adaptation and mitigation measures are carefully chosen. For instance, widespread bioenergy plantations to mitigate global warming can  compete for land with food production, potentially affecting food security.


The Canadian picture and the view of CMOS

The impacts of climate change will be felt differently around the world. For Canada, the impacts are determined by its location in the northern middle to high latitudes and its long coastlines bordering the Atlantic, Arctic and Pacific oceans. Because warming is amplified at high northern latitudes, parts of Canada have experienced twice the warming observed globally, with many detectable impacts on ecosystems and human systems. Along with other countries, Canada would see significant benefits from limiting warming to 1.5°C. If we avoid the 2°C limit and stay below the 1.5°C limit, we expect to see a wide range of benefits, including fewer and less intense heat waves, less intense heavy rainfall events, fewer wildfires, reduced sea level rise, lower probability of a sea ice-free Arctic in the summer, with reduced associated risks for Arctic ecosystems and communities, reduced risk of climate-induced degradation and loss of high latitude tundra and boreal forest, and a smaller permafrost area subject to thaw.

The report suggests that Canada’s emission reduction targets are insufficient to limit warming to 1.5°C and will need to be strengthened if Canada is to do its fair share in reducing global carbon emissions.

Beyond our borders, it is, in the view of CMOS, important for Canada, as an internationally engaged nation, to be fully aware of the stakes and take action on carbon emissions reductions to limit global warming to 1.5°C and avoiding the risks associated with the 2°C limit. This needs to apply to CMOS’s own practice as a professional organization, which is a topic we will be focusing on in the coming year.

CMOS strongly endorses this Special Report, and furthermore recognizes and appreciates the time investment of the Canadian researchers who contributed their expertise to lead it; it provides critical scientific input to climate policy at the highest international level.