On June 14, 2019 ICLR conducted a Friday Forum webinar led by Dr. Nathan Gillett and Dr. Xuebin Zhang. This report is about how and why Canada’s climate has changed and what changes are projected for the future. Led by Environment and Climate Change Canada, this document is the first of a series to be released as part of Canada in a Changing Climate: Advancing our Knowledge for Action. It documents changes across Canada in temperature, precipitation, snow, ice, and permafrost, freshwater availability as well as in Canada’s three oceans. It can be viewed at www.changingclimate.ca/CCCR2019 Dr. Nathan Gillett is a Research Scientist at the Canadian Centre for Climate Modelling and Analysis in Environment and Climate Change Canada’s Climate Research Division. His research is focused on understanding and attribution of climate change. He is a Coordinating Lead Author of the chapter “Human influence on the climate system” of the upcoming IPCC Working Group I Sixth Assessment Report, and he served as a Lead Author of the IPCC Fourth and Fifth Assessment Reports. Dr. Gillett has a PhD in atmospheric physics from the University of Oxford. Dr. Xuebin Zhang is a senior research scientist with Environment and Climate Change Canada’s Climate Research Division. His main research focus is past and future changes in weather and climate extremes. He was a lead author for the IPCC Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation and IPCC Working Group I Fifth Assessment Report. He is a Coordinating Lead Author of the climate extremes chapter in the IPCC Working Group I Sixth Assessment Report. Dr. Zhang has a background in engineering hydrology. He received a PhD degree in Physics (Climatology) from University of Lisbon, Portugal.

1. A collaborative effort:
Environment and Climate Change Canada
Fisheries and Oceans Canada
Natural Resources Canada
University experts
Wearable technology, developed with funding
from the NSERC Discovery Grants program
Source: Western University
Overview of the report
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2. Canada’s National Assessment on Climate Change
Canada in a Changing Climate: Advancing our Knowledge for Action
Interactive Website
(ChangingClimate.ca/CCCR2019)
Health Assessment
Canada’s
Changing Climate
Report
Canada in a Changing
Climate - Regional
Perspectives
Enhanced
Synthesis
Canada in a Changing
Climate- National
Issues
Phase 1:
2016-2018
Phase 2: 2017-2021
Phase 3:
2020-2021
Indigenous Resilience
Laying a climate science foundation for the forthcoming reports of the national assessment.
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3. • Global emissions of carbon dioxide
from human activity will largely
determine how much warming
Canada and the world will
experience in the future.
• This warming is effectively irreversible.
3
Canada’s climate has warmed and will warm further in
the future, driven by human influence.

4. 4
• Human emissions of CO2 are the main
determinant of future warming
• Different temperature limits have
different ‘carbon budgets’ – total
remaining cumulative CO2 emissions
• A finite carbon budget implies CO2
emissions must achieve ‘net zero’
• Global warming will persist for
centuries to millennia after emissions
are zeroed
Human influence on global climate
Hypothetical scenario in which CO2 emissions are zeroed
instantaneously
Global CO2 emissions zeroed
in 2010, and 2100
IPCC, 2013 Year

5. Canada has warmed, faster than the global average
• Annual average temperature in Canada has increased by 1.7◦C between 1948
and 2016.
• Canada has warmed about two times the global rate.
• Warming is not uniform across Canada. Northern Canada has warmed by 2.3◦C,
about three times global warming.
• Most of the observed increase in annual average temperature in Canada can be
attributed to human influence
5
Annual

6. The effects of widespread warming are evident across
many indicators.
6
Changes in annual precipitation
1948-2012
• Annual precipitation has increased in many regions since 1948.
• Averaged over the country, normalized precipitation has increased by about
20% from 1948 to 2012.
• An increase in growing season length of about 15 days between 1948 and 2016
has been observed.
Length of growing season (days)

7. 7
More extreme heat and less extreme cold have been
observed in Canada
• The annual highest daily maximum temperature, averaged over Canada,
increased by 0.61◦C between 1948 and 2016
• The annual lowest daily minimum temperature, averaged over Canada, increased
by 3.3◦C between 1948 and 2016
• Most of the observed increase in the coldest and warmest daily temperatures in
Canada can be attributed to human influence

8. 8
• Over the past three decades, the proportion of Canadian land
and marine areas covered by snow and ice have decreased,
permafrost temperatures have risen, and Arctic and alpine
glaciers have thinned at rates unprecedented for several millennia
SNOW COVER
DURATION
ICE COVER
DURATION
GLACIER CUMULATIVE
THICKNESS
PERMAFROST
TEMPERATURE
CANADA
GREENLAND
RUSSIA
ALASKA
A warmer world - declines in snow, ice and permafrost

9. • Canadian Arctic marine areas are
projected to have extensive ice-free
periods during summer by mid-
century.
• The last area with summer sea ice is
projected to be within and north of
the Canadian Arctic Archipelago.
• This area will be an important refuge
for ice-dependent species and an
ongoing source of potentially
hazardous ice which will drift into
Canadian waters.
9
Canadian areas of the Arctic and Atlantic Oceans will
experience longer and more widespread sea ice-free
conditions.
Schematic of the last ice area of the Arctic Ocean

10. The seasonal availability of freshwater is changing
with an increased risk of water supply shortages in
summer.
• Warmer winters and earlier
snowmelt will combine to produce
higher winter streamflows
• Smaller snowpacks and loss of
glacier ice this century will combine
to produce lower summer
streamflows.
• Warmer summers will increase
evaporation of surface water and
contribute to reduced summer
water availability in the future
despite more precipitation in some
places.
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Spring freshet at Eakin Creek in BC

11. • Over the last several decades, spring peak streamflow following snowmelt has
occurred earlier, with higher winter and early spring flows. In some areas,
reduced summer flows have been observed.
• Seasonal changes projected to continue, with shifts from more snowmelt-
dominated regimes toward rainfall-dominated regimes.
The seasonal timing of peak streamflow has shifted,
driven by warming temperatures.
11

12. • Anthropogenic (human) activities
explain most of the historical warming
trend in annual average temperature,
as well as for the hottest and coldest
temperatures of the year
12
Most of the observed temperature increase can be
attributed to human influence
• Natural external
factors (solar and
volcanic activity)
play a very minor
role

13. Anthropogenic climate change has increased the
likelihood of some types of extreme events.
13
• Canada is already seeing
the impacts of human-
caused climate change in
extreme events
• The 2013 Alberta floods:
increased likelihood of
extreme rainfall
• The 2016 Alberta wildfire:
increased likelihood of
extreme wildfire risk and
length of the fire season
Schematic illustration of event attribution

14. 14
low
emissions
high
emissions
(⁰C)
Future warming in Canada depends directly on global
emissions
• Low emission scenario: an additional annual
warming of about 2⁰C is projected by mid-
century, with temperatures steady after that
• High emission scenario: temperature
increases will continue, reaching more than
6 ⁰C by late century
• Consistent with observed warming, future
warming will be strongest in winter and in
northern Canada
• Changes shown are for the late 21st century,
under a high emission scenario, relative to
the 1986-2005 reference period

15. 15
• Canada is projected to warm at twice the global rate, regardless
of the emissions scenario
• Many impacts-relevant metrics, such as growing season length,
scale with temperature
Regional climate changes, such as for Canada,
are closely related to change in the global mean.

16. 16
• Annual and winter precipitation is
projected to increase everywhere in
Canada over the 21st century, with
larger changes under a high emission
scenario
• Larger percent changes are
projected for northern Canada
• Unlike for temperature, which is projected to
increase everywhere in every season,
precipitation has patterns of increase and
decrease
• Summer precipitation is projected to decrease
in southern Canada under a high emission
scenario toward the end of the century
High emissions
Low emissions
Winter
(%)
A warmer climate will bring more precipitation
on average

17. • Extreme hot temperatures will become
more frequent and more intense. This will
increase the severity of heatwaves, and
contribute to increased drought and
wildfire risks.
• Future droughts and soil moisture deficits
are projected to be more frequent and
intense across the southern Canadian
Prairies and interior British Columbia
during summer, and to be more
prominent at the end of the century
under a high emission scenario.
HEAT WAVES
WILDLAND
FIRES
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A warmer climate will intensify some weather extremes
in the future.

18. More intense rainfalls will increase urban flood risks
• Projected increases in extreme
precipitation are expected to increase
the potential for future urban flooding.
• Projected higher temperatures will result
in a shift toward earlier floods
associated with spring snowmelt, ice
jams, and rain-on-snow events.
• It is uncertain how projected higher
temperatures and reductions in snow
cover will combine to affect the
frequency and magnitude of future
snowmelt-related flooding.
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19. 19
Change in temperature extremes
High emission scenario
Future increases in the frequency and intensity of
extreme temperature and precipitation events
• A current 1 in 20-yr hot extreme will
become a once in 2-year event by
mid-century under a high emission
scenario (a ten-fold increase in
frequency)
Change in precipitation extremes
High emission scenario
• A current 1 in 20-yr rainfall extreme will
become a once in 10-yr event by mid-
century under the high emission scenario
(a two-fold increase in frequency)

20. • Changes in local sea-level
are a combination of global
sea level rise and local land
subsidence or uplift.
• Local sea level is projected to
rise, and increase flooding,
along most of the Atlantic
and Pacific coasts of
Canada and the Beaufort
coast in the Arctic where the
land is subsiding or slowly
uplifting.
20
Coastal flooding is expected to increase in many areas
of Canada due to local sea level rise.
• The loss of sea ice in Arctic and Atlantic Canada further increases
the risk of damage to coastal infrastructure and ecosystem due to
larger storm surges and waves.
End-of-century projected relative (local) sea-level change
under a high emission scenario, relative to 1986-2005

21. • Scenarios with large and
rapid warming illustrate the
profound effects on
Canadian climate of
continued growth in
greenhouse gas emissions.
• Scenarios with limited
warming require Canada
and the rest of the world
to reduce carbon
emissions to near zero
early in the second half of
the century.
High global
emissions
large warming
Low global
emissions
limited warming
The rate and magnitude of climate change under high
versus low emission scenarios project two very different
futures for Canada.
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22. Take home messages on extremes…..
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• The magnitude of future warming will be determined by the extent
of future GHG (principally, CO2) emissions or mitigation
• Across Canada, we have already observed increases in the
hottest temperatures and larger increases in the coldest
temperatures.
• Substantial future changes are projected in temperature extremes.
There will be more hot and fewer cold temperature extremes.
• Warmer temperatures are accompanied by an increase in
atmospheric moisture, which increases extreme precipitation.
• Although we cannot focus on individual locations, we can use
robust large-scale projections and theoretical understanding to
understand future changes in locally-relevant climate extremes.