Download Day 18

15
Global Climate Change
PowerPoint® Slides prepared by Stephen Turnbull
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© 2010 Pearson Education Canada
15-1
Housekeeping Items
• We will briefly go over the mid-term today.
• Just a reminder that the Weather Channel will be
having a teach-in on climate and environment issues
next Thursday from 7 p.m. on
• At some point today, I want to show a short video:
www.filmsforaction.org/watch/wake_up_freak_out_t
hen_get_a_grip/.
• Suggested resources: “White Water, Black Gold,”
which is owned by our library; see also the short
video: http://www.youtube.com/watch?v=HHP9Rhooh0.
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Upon successfully completing this chapter,
you will be able to
• Describe Earth’s climate system and explain the many
factors influencing global climate change
• Characterize human influences on the atmosphere and
global climate
• Summarize modern methods of climate research
• Outline current and future trends and impacts of global
climate change
• Suggest ways we can respond to climate change
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Central Case: The Retreat of The
Athabasca
“We’re in a giant car heading towards a brick wall and
everyone’s arguing over where they’re going to sit.”
– David Suzuki
• The Athabasca Glacier has been retreating since 1844
• Since then, it has lost half of its volume
• Currently retreating at a rate of 2-3 metres per year
• Is it retreating due to climate change or is it just a
natural continuation of the retreat of glacial ice that
began 12,000 years ago?
• The Rockies may be ice-free by the end of this century
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Our Dynamic Climate
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Our dynamic climate
• Climate influences everything around us
• The Fourth Assessment Report of the Intergovernmental
Panel on Climate Change (IPCC) made it clear that:
- Climate is changing, we are the cause, and this change
is already exerting impacts that will become
increasingly severe if we do not take action
• Climate change is the fastest-moving area of
environmental science today, and the Fifth Report is due
quite soon
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What is climate change?
• Climate = an area’s long-term atmospheric conditions
- Temperature, moisture content, wind, precipitation, etc.
• Weather = conditions at localized sites over hours or days
• Global climate change = describes trends and variations in
Earth’s climate
- Temperature, precipitation, storm frequency
• Global warming = an increase in Earth’s average
temperature
- Earth’s climate has varied naturally through time
- The rapid climatic changes taking place now are due to
human activity: fossil fuels, combustion, and deforestation
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The Sun and atmosphere keep Earth warm
• Four factors exert more influence on climate than
all others:
- The Sun (supplies planet’s energy)
- The atmosphere (absorb 70% of incoming solar
radiation)
- The oceans (shape climate by storing and
transporting heat and moisture)
- Albedo = reflectivity of a surface
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Our planet absorbs solar radiation
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Greenhouse gases warm the lower
atmosphere
• As Earth’s surface absorbs solar radiation, the surface
increases in temperature and emits infrared radiation
• Greenhouse gases = atmospheric gases that absorb
infrared radiation (radiatively active gases)
- Water vapor, ozone, carbon dioxide, nitrous oxide,
methane, chlorofluorocarbons (CFCs)
- Greenhouse gases differ in their ability to warm the
troposphere and surface
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Greenhouse gases warm the lower
atmosphere (cont’d)
• After absorbing radiation, greenhouse gases re-emit
infrared energy
- Some energy is lost to space
- Greenhouse effect = some energy travels back
downward, warming the troposphere and the planet’s
surface
• Global warming potential = the relative ability of one
molecule of a given greenhouse gas to contribute to
warming
- Expressed in relation to carbon dioxide (potential = 1)
- Nitrous oxide is 296 times as potent as carbon dioxide
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Carbon dioxide is the anthropogenic
greenhouse gas of primary concern
• Not the most potent greenhouse
gas, but it is extremely abundant
- The major contributor to
global warming
• Human activities have boosted
atmospheric concentrations from
280 parts per million (ppm) to
389 ppm in 2010
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Human activity has released carbon from
sequestration in long-term reservoirs
• Human activities accelerate the fluxes of material
from one reservoir to another in biogeochemical
cycles
- Burning fossil fuels transfers CO2 from
lithospheric reservoirs into the atmosphere
- Deforestation transfers CO2 from terrestrial
reservoirs into the atmosphere
- Sinks = reservoirs that accept more of the material
than they release
- Ocean
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Other greenhouse gases contribute to
warming
• Methane from fossil fuel deposits, livestock, landfills,
and crops such as rice
• Nitrous oxide from feedlots, chemical manufacturing
plants, auto emissions, and synthetic nitrogen fertilizers
• Ozone from photochemical smog
• Halocarbons (CFCs and HFCs)
• Water vapor = the most abundant greenhouse gas and
contributes most to the greenhouse effect
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There are many feedback cycles in the
climate system
• Positive feedback cycle
- Warming leads to water vapour which leads to further
warming causing still more evaporation, and so on
• Negative feedback cycle
- Warming leads to evaporation which leads to water
vapour causing increased cloudiness slowing global
warming
• Aerosols = microscopic droplets and particles that have
either a warming or cooling effect
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Radiative forcing expresses change in
energy input over time
• Radiative forcing = the
amount of change in energy
that a given factor causes
- Positive forcing warms the
surface; negative forcing
cools it
• Compared with the preindustrial Earth, Earth is
experiencing radiative forcing
of 1.6 watts/m2
- Enough to alter the climate
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The atmosphere is not the only factor that
influences climate
• Milankovitch cycles = periodic changes in Earth’s
rotation and orbit around the Sun
• Solar output = drives temperature change on Earth’s
surface
• Ocean absorption = the ocean holds 50 times more
carbon than the atmosphere and absorbs it from the
atmosphere (acts as a sink)
• Ocean circulation = ocean water exchanges
tremendous amounts of heat with the atmosphere,
and ocean currents move energy from place to place
- Thermohaline circulation
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Milankovitch cycles
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In Atlantic, warmer surface water flows north, cools and sinks, forming
the North Atlantic Deep Water (NADW)
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The Science of Climate Change
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Proxy indicators tell us about the past
• Proxy indicators = types of indirect evidence that
serve as substitutes for direct measurements
- Ice caps, ice sheets, and glaciers hold clues to past
climate
- Trapped bubbles in ice cores show atmospheric
composition, greenhouse gas concentration,
temperature trends, snowfall, solar activity, and
frequency of fires
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Stable isotope geochemistry is a powerful
tool for the study of paleoclimate
• Stable isotope geochemistry = studying stable
isotopes of elements
• Fractionation = separation and differential
concentration of isotopes of slightly different mass
• Proxy indicators like stable isotopes often give us
information about local or regional areas so scientists
combine multiple records from various areas
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Direct atmospheric sampling tells us about
the present
• Atmospheric carbon dioxide concentrations have
increased from 315 ppm in 1958 to 392 ppm in 2011
• There are seasonal variations in levels due to
photosynthetic uptake
- More carbon dioxide absorbed during northern
summer
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Models help us understand climate
• Climate models
simulate climate
processes
• Use information
about:
- atmospheric
circulation
- ocean
circulation
- interactions
- feedback
mechanisms
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Models help us understand climate (cont’d)
•
Effectiveness of models are
tested by entering data from
the past and running the model
toward the present
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Current and Future Trends and Impacts
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Current and future trends and impacts
• Evidence that climate conditions have changed since
industrialization is now overwhelming and
indisputable
• The way each of us experiences these impacts will
vary tremendously
• The impacts on Canada could be particularly severe,
depending on where we live
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The IPCC summarizes evidence of climate
change and predicts future impacts
• Trend = a pattern that persists within a data set, even
after short-term fluctuations and anomalies have been
accounted for
• Intergovernmental Panel on Climate Change (IPCC)
- 2007: Fourth Assessment Report
- Consensus of scientific climate research from
around the world
- Trends in surface temperature, precipitation
patterns, snow and ice cover, sea levels, storm
intensity, and other factors
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Temperature increases will continue
• The IPCC report concludes that average surface
temperatures on earth have been rising since 1906, with
most of the increase occurring in the last few decades
(0.74 ̊ C)
• Fifteen years from 1997-2011 among the 20 warmest
years on record
• Permafrost = perennially frozen ground
- Thawing in the Arctic
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Projected increases in surface temperature
• More frequent heat waves
• Temperature change will vary by region
• Stronger storms
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weighing
issues
the
Climate Change and
Human Rights
In December 2005, a group representing North America’s Inuit
sent a legal petition to the Inter-American Commission on
Human Rights, demanding that the United States restrict its
greenhouse gas emissions, which the Inuit maintained were
destroying their way of life in the Arctic . After a year, the
commission dismissed the petition with a terse three-sentence
letter.
• Do you think Arctic-living people deserve compensation from
industrialized nations whose emissions have caused climate
change that has disproportionately affected the Arctic?
• Do you think climate change can be viewed as a human rights
issue?
• What ethical issues, if any, do you think climate change
presents? How could these best be resolved?
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Changes in precipitation will vary by region
• Some regions are receiving more precipitation than
usual, and others are receiving less
• Droughts have become more frequent and severe
- Harming agriculture, promoting soil erosion,
reducing drinking water supplies, and encouraging
forest fires
• Heavy rains have contributed to flooding
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Projected changes in June-August precipitation, 2090-2099
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Melting ice and snow have far-reaching
effects
• Mountaintop glaciers are disappearing
- Have lost an average of 14 m since 1980
- Risks of sudden floods as ice dams burst
- Reducing summertime water supplies
• As ice melts, darker, less-reflective surfaces are exposed
and absorb more sunlight, causing more melting
• Melting permafrost makes slopes unstable and could
release soil gases leading to further warming
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The Arctic is changing dramatically
• Less snow cover
• Melting immense ice sheets (Greenland ice sheet)
• Canada’s ice shelves have shrunk by 90% over the past
100 years (Ayles Ice Shelf)
• Warming is accelerating
- as snow and ice melt, darker, less-reflective surfaces
are exposed
- Earth’s capacity to reflect light decreases
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Rising sea levels will affect hundreds of
millions of people and coastal zones
• As glaciers and ice
melt, increased water
will flow into the
oceans
• As oceans warm, they
expand
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weighing
issues
the
An Ice-Free Northwest Passage
and Canada’s Arctic Sovereignty
Now that the Northwest Passage – the long-coveted sea route from the Atlantic
to the Pacific via the Arctic Ocean – may soon be ice-free, northern nations are
anxious to confirm its sovereignty over Arctic waters at an international
conference held in Greenland recently, and Prime Minister Stephen Harper
pledged to spend billions of dollars defending Canada’s interests in the Arctic
if necessary. In addition to the sea route, the Arctic subsurface may hold as
much as 25% of the world’s undiscovered oil and gas reserves.
• The U.S. argues that the High Arctic does not belong to Canada, or to anyone
else. What do you think?
• Who should control Arctic Ocean waters, and for what purposes?
• How much of Canadian taxpayers’ money should be spent to assert and
maintain Canada’s sovereignty in the Arctic?
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Climate change affects organisms and
ecosystems
• Global warming modifies temperature-dependent
phenomena
- Timing of migration, breeding
• Spatial shifts in the range of organisms
- Animals and plants will move towards the poles or
upward in elevation
- 20-30% of all species will be threatened with extinction
• Plants act as carbon sinks; fewer plants means more CO2 in
the atmosphere
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weighing
issues
the
Environmental Refugees?
The Pacific island nation of Tuvalu has been losing 9 cm of elevation per
decade to rising seas. Appeals from Tuvalu’s 11,000 citizens were heard by
New Zealand, which began accepting them in small numbers as of 2003,
although the government has not officially categorized them as environmental
refugees – people driven from their homelands as a result of environmental
change or natural disaster. Tuvaluans have been particularly vocal about global
warming, but several other small Pacific island nations have joined in voicing
their concerns.
• Will there come a time when neighbouring countries should begin to treat
people who leave small island nations as environmental refugees?
• Should they be doing it now?
• What will happen to these people after relocation – do you think a national
culture can survive if its entire population is relocated?
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Climate change exerts societal impacts –
and vice versa
• Agriculture:
- growing seasons shortened, crops more susceptible;
crop production will decrease, worsening hunger
• Forestry:
- increased insect and disease outbreaks, increased
chance of forest fires
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Climate change exerts societal impacts –
and vice versa (cont’d)
• Health:
- heat waves can cause death, respiratory ailments,
expansion of tropical diseases, increased chance of
drowning if storms become intense, hunger-related
ailments
• Economics:
- some costs and some benefits; costs will outweigh
the benefits, widen the gap between rich and poor,
will cost roughly 5-20% of world GDP
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Are we responsible for climate change?
• The IPCC concluded:
- It is more than 90% likely that most of the global
warming recorded over the past 50 years is due to the
well-documented increase in greenhouse gas
concentrations in our atmosphere
• Today the debate concerning the human role in climate
change is largely over
• Shift in public perception
• Al Gore’s 2006 “An Inconvenient Truth”
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Responding to Climate Change
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Responding to climate change
• We will likely either keeping on pursuing economic
growth at all costs, which will require more and more
resources to fix the damage (what ecological
economists call ‘dis-economies of scale’), and will
eventually lead to social, economic, and population
crash, or
• We will make sustainability our first priority, aim for a
‘soft landing’ and create a steady-state economy.
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Shall we pursue mitigation or adaptation, or
intervention?
• Mitigation = pursue actions that reduce greenhouse
gas emissions, in order to lessen severity of future
climate change
- Renewable energy sources, farm practices to
protect soil integrity, preventing deforestation
• Adaptation = accept climate change is happening and
pursue strategies to minimize its impacts on us
- Criticized as sidestepping
• Both are necessary
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Shall we pursue mitigation or adaptation, or
intervention?
• Intervention = set of possible large-scale
technological modifications to the global climate
system
• Causes of concern:
- Interfering with global-scale Earth’s systems
- Abandon mitigation efforts
• Geo-engineering – grand scale intervention
- Increase fluxes of greenhouse gases
- Reduce incoming solar radiation
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We can look more closely at our lifestyle
• Conservation and efficiency
- High-efficiency light bulbs and appliances
- Reduce electricity consumption
- Life-style choices
• Sources of electricity
- Alter types of energy we use
- Natural gas cleaner than oil; oil cleaner than coal
• Carbon capture and storage = remove CO2 from
power plant emissions
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Transportation is a significant source of
greenhouse gases; likewise buildings
• Automotive technology
• make vehicles more fuel-efficient, hybrid cars
• Driving less and using public transportation
- Public transportation is the most effective way to
conserve energy, reduce pollution
- Live nearer your workplace, so you can bike or
walk
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Conventional cars are extremely inefficient
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We can reduce emissions in other ways as
well
• Use advances in agriculture, forestry, and waste
management
- Grow renewable biofuels
- Rapid reforestation of deforested areas
- Recovering methane from landfills
- Recycling, composting, and reduction or reuse of
materials
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We will need to follow multiple strategies to
reduce emissions
• There is no single magic bullet for mitigating climate
change
• Most reductions can be achieved using current
technology so we can begin right away
• How quickly and successfully we translate science and
technology into practical solutions for reducing emissions
depends on policies and the market economy
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We began tackling climate change by
international treaty
• UN Framework Convention on Climate Change
(FCCC) = outlines a plan for reducing greenhouse gas
emissions to 1990 levels by the year 2000 through a
voluntary, nation-by-nation approach
- By the late 1990s, it was clear that the voluntary
approach would not succeed
• Developing nations created a binding international treaty
that would require all signatory nations to reduce their
emissions
• However, subsequent rounds of talks have proven
relatively fruitless
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We began tackling climate change by international
treaty (cont’d)
• The Kyoto Protocol
- by 2012 nations must reduce emissions of six
greenhouse gases to levels below those of 1990
- took effect in 2005, after Russia became the 127th
nation to ratify it, Canada withdrew in 2011
• The United States will not ratify the Kyoto Protocol
- Did not require same on countries of China and India
• Businesses in industrialized nations feel they have more
to lose economically from restrictions
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Market mechanisms are being used to
address climate change
• Carbon taxes (e.g., B.C.)
• Permit trading programs
- harness the economic efficiency of the free market to
achieve policy goals
- The Chicago Climate Change is the world’s first
emissions trading program for greenhouse gas
reduction
• Cap-and-trade programs
- European Union Emission Trading Scheme
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Carbon offsets are in vogue
• Carbon offset = a voluntary payment to another entity
intended to enable that entity to reduce the greenhouse
emissions that one is unable or unwilling to reduce oneself
- Popular among utilities, businesses, universities,
governments, and individuals trying to achieve carbon
neutrality
• Carbon-neutrality = no net carbon is emitted
• Carbon offsets fall short
- A lack of oversight to make sure that the offset money
accomplishes what it is intended for
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You can reduce your own carbon footprint
• Carbon footprint = expresses the amount of carbon
we are responsible for emitting (see How Bad Are
Bananas? The Carbon Footprint of Everything by
Mike Berners-Lee)
• What do you think you can do to make a difference?
• What about in relation to politicians and corporations?
• Global climate change may be the biggest challenge
facing us and our children
- Taking immediate action is the most important
thing we can do
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Conclusion
• Many factors influence Earth’s climate
- Human activities play a major role
• Climate change is well underway
- Further emissions will cause severe and diverse
impacts
• More and more scientists are urging immediate action
- Reducing emissions
- Mitigating and adapting to a changing climate
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