GPHY 314 Quiz: Week 8

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29 Dec 2020
WEEK 8: Impacts of Climate Change
Climate Change and Heatwaves
Denial 101 video
o Why heat waves are happening more often
o Can cause droughts, wildfires, crop failures
o Human-induced GHG emissions made it approx. x4 more likely that a summer
like Europe 2003 would occur
o Bell curve of getting cold, average, hot weather
In normal climate, good odds for average weather but if global average
temperature goes up, whole bell curve will be shifted toward hot end
o Global warming = earth on steroids
Equating extreme temperatures to hitting homeruns in baseball
o Combine effects of increase in average temperature and increase in “weirdness”,
expect heatwaves to be both hotter and frequency
o Night warming faster than days = fingerprint of global warming
If nights hot, one more ingredient for extreme heat wave
o Will put more heat stress on people in some regions because heat index depends
on how humid the air is -> Hotter = more humid = more uncomfortable
o Myth that heat waves happened before so can’t say global warming causes them
now -> Non-sequitur fallacy
Representation of 90th percentile of warm days
o Comparing historical amount of days we were above 90th percentile threshold was
around 10% early on, but moving forward to current times is now at 20% of days
exceeding the threshold
o Clear evidence of more warmer days associated with climate change
o Extending into future, see pretty big range in potential alternatives in the future
Similar trend looking at cold days
o Early on in the record we have more cold days than the 10%, and have seen
coldest days decline approaching current times and for future projections
Used to be that cold extreme vs warm extreme ratio was around 1:1
o But warm extremes occurring x4 (4:1 ratio) starting into the 200s
o Could find itself approaching even 10:1 in the future
o Will always be cold records in the future, but becomes exceedingly unlikely as
century moves on and as we look at really extreme scenarios
Heat waves: period of marked unusual hot weather (maximum, minimum, daily average
temperature) over region persisting at least 3 consecutive days during warm
period of year based on local (station-based) climatological conditions, with
thermal conditions recorded above given thresholds
o Thresholds vary between regions
o ^World Meteorological Association definition requires it occur during the warm
part of the year i.e. not considered heat wave if occurring in mid-winter
o Matters for cardiovascular, respiratory, mental health perspective
o People most vulnerable are those with least resources to cool selves, considering
how climate change disproportionately significant on night temperatures
Clear anthropogenic signal, studies demonstrating where signal emerged from the noise
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o European summer heatwave had such a low probability of occurring,
wouldn’t have happened without anthropogenic influence
o 2010 summer averaged a lot above other anomalies, even 2003 summer
o France 2003 summer had 15,000 excess deaths due to event
Important to recognize not all risks are distributed evenly spatially
Global risk of deadly heat study (Mora et al., 2017)
o Series of more recent events that lead to large counts of excess mortality
o Looked at types of conditions present across the globe
o As you get to higher temperatures (upper 30s), if you combine with higher
relative humidity, more likely to have deadly heat event
o On annual basis, occur mostly in areas of lower latitude
o Using RCP 4.5, by end of century, projections of significant portion of year above
deadly threshold in key parts of world
Northwest Africa, South America, southeastern Asia
But also see some events in the United States, which hasn’t occurred in the
historical data
Prairie Climate Center Heat Waves and Health (special report on climate change)
o Definition of heat wave still using at least 3 days threshold, but using 30°C cut-off
o 2051-2080, admittedly with high carbon scenario (close to 8.5)
o Average number of heat waves per year across Canada
o Moving to the south (southeastern Ontario) see clusters that show lots of risk, also
moving into prairie regions
o If we look into northwestern Canada, see enhanced heat wave risk start to creep
up into territorial regions
o Shows that this risk not exclusive to southern Canada although higher risk along
the interior but can spread across the country
Even coastal regions like Halifax; expected to increase to maybe 10/year
Toronto and Ottawa; expected to not only increase in number of
heatwaves, but those that traditionally last 4/5 days may last 15-17 days
Prairie region important agricultural zone, so heat waves will impact
ecosystems and food systems
Lower water levels and flow -> Dry, dusty conditions -> Economic
losses -> Interrupted hydroelectricity
Northwestern Canada also at risk of forest fires; expect longer, drier fire
seasons from more evaporation, also potentially more storms/lightning
o Still some atmospheric components we don’t completely understand how they
will impact heat waves
Expecting increase in atmospheric blocking events -> Circulation patterns
that get stuck i.e. heat wave doesn’t break up
Climate Extremes
Definition of heat waves i.e. Meteorological one -> Doesn’t mean we don’t get extreme
events outside of warmer seasons
o February 2010 arctic winter heat extreme; more common last few decades
o Huge swath of eastern Canadian arctic was +10°C above normal for February
o Extreme event but wouldn’t be called heat wave since it didn’t occur in summer
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Doesn’t mean impacts weren’t extreme for residents
Mean temperature getting closer to 0°C which could lead to ice melt,
which can have profound impacts on remote communities
o Occurred during relatively cool conditions over Europe and the US
o Since major areas dominate the media outlet, people assume conditions were cold
How a warmer arctic could intensify winter Vox video
o Temperatures rising across world, with warming x2 fast in arctic
o Lost 3/4 of sea ice, covers 1/3 less of the ocean than it did 20 years ago
o Ice melts, turning reflective surface dark to absorb solar energy, warming up
Without ice, more water evaporates, contributing to GHGs
o Earth’s air tends to move from warm middle of the planet to the poles
Warm air takes more space so gravity pulls it toward Arctic, creating wind
Earth spinning, creating polar jet stream (river of air) moving west to east
Serves as boundary between cold air from Arctic and warm air
from tropics
Arctic atmosphere changing as temperatures rise there faster than
further south
Less gravitational pull on air towards North Pole, jet stream slows
o Less of flow, jet stream loses steam
When curvy, weather sticks around longer, causing bigger storms,
droughts, cold spells
Some think it’s supercharging extreme weather across world
How polar jet stream affected US past winter (Jennifer Francis)
Huge northward swing in jet stream over west coast, bringing lots
of warm air to Alaska -> Hottest December on record, with most
temperatures 20°F/30°F above average
Took southward dive over Rockies and dipped into Florida
o Hadn’t seen measurable snow in over 30 years, but
happened; alligators got frozen into swamps
Meteorologists called it a “bomb cycle”
Then resulted in 20°F increase above average, before it brought
cold temperatures to Asia
o Extreme weather in North America occurring more often
When Arctic very warm, very cold temperatures in eastern side of US
likely (“warm arctic, cold continents”)
Areas in world where signal of Arctic impact on mid-latitude sometimes very robust,
while other studies find minimal impacts
National security
o Hurricane Michael tore up hangars and buildings across Tyndall Air Force Base
in 2018; caused $5B in damage
o Series of reports from US context to assess potential risks/vulnerabilities across
bases, especially with sea level rise along coastal military installations
o Potential instabilities can impact intergovernmental interactions, and international
states with vulnerable groups
Climate Wars Syria video (Thomas Friedman)
o Link between climate change and immigration pattern of Syrians
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