Download Global Climate Change

Global Climate Change
OUR CHANGING CLIMATE
What is Climate Change?
• Climate = long-term weather patterns (what
you expect; weather is what you get!)
• GCC = changes in long-term pattern of
atmospheric conditions involving ∆T,
precipitation, storm frequency & intensity
• Global warming is one aspect
Greenhouse Effect
• Short-wave radiation absorbed by earth
• Earth warms up, releases IR radiation
• Tropospheric greenhouse gases (CO2, CH4,
H20) absorb IR
Greenhouse Effect
• Due to abundance, CO2 is of primary concern
• Current levels at their highest in 650,000 –
2,000,000 years
• Fossil fuel burning, forest clearing and burning
are the two main anthropogenic sources of
increased CO2 levels
Greenhouse Gases
• Methane (from fossil fuel extraction, cattle,
landfills, certain crops like rice)
• N2O from feedlots, automobiles, agriculture
• Tropospheric O3
• Halocarbons have decreased due to Montreal
Protocol of 1987
• Aerosols may have short-term cooling effect
Other Factors
• Milankovitch cycles = changes in the earth’s
rotation and orbit around the sun
• Solar output and solar cycle
• Ocean absorption of CO2
Other Factors
El Niño =
• Equatorial winds weaken and allow warm water
from western Pacific to move eastward
• Prevents cold water from upwelling in eastern
Pacific
La Niña =
• Cold surface waters extend far westward
Other Factors
• Thermohaline circulation = worldwide current
system in which warmer fresher water moves
along the surface; colder, saltier water moves
down
• North Atlantic Deep Water = warm surface
water moves northward toward Europe; cooler
water sinks and returns in other direction
STUDYING CLIMATE CHANGE
Proxy Indicators
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Preserved gas bubbles in ice
Sediment beds beneath bodies of water
Coral reefs and tree rings
All are forms of indirect evidence
Atmospheric Sampling
• Started in 1958 – Charles Keeling of Scripps
Institution of Oceanography – trends of CO2
concentrations
• His data showed shows an increase of CO2
concentrations from 315 to 383 ppm
Modeling
• Coupled general circulation models (CGCMs)
• Combine what is known about weather
patterns, atmospheric circulation, atmosphereocean interactions, and feedback mechanisms
to simulate climate processes
• Over a dozen research labs world wide
• A good approximation of relative effects of
natural and anthropogenic influences
CURRENT & FUTURE
IMPACTS
IPCC Report
2007 – summarized 1000s of reports
Includes trends in sfc temp, rainfall patterns, snow
& ice cover, sea levels, storm intensity, etc
Included a series of possible climate change
scenarios, including:
• Temp increases (1.33oF in last century)
• Increases in power and duration of storms
• Changes in precipitation
Muir Glacier: 1948 and Now
IPCC Report
• Polar ice melt
• Glaciers disappearing (Since 1980 – glaciers
have lost an average of 9.6 m vertical
• This changes earth’s albedo
• Rising sea levels (3.1 mm/y from 1993 – 2003)
• A several inch vertical rise = many feet of
horizontal incursion into coastal lands
IPCC Report
• Storm surges present a great risk to island
nations
• Rising sea levels will force people to choose
between relocating or investing in costly
protections
• Ecosystems also affected
• Timing of seasonal events are creating complex
effects in ecosystems
IPCC Report
Societal impacts will also occur
• Agriculture – cuts in productivity (drought &
flood)
• Forestry – insects, disease outbreaks, , invasive
species, fires
• Health – heat stress, tropical diseases,
respiratory ailments, hunger
• Economics – est. of 1 – 5% of GDP
RESPONDING TO CLIMATE
CHANGE
Our Response
Mitigation or adaptation?
• Mitigation = actions that would reduce
emissions of GHG
• Adaptation = search for ways to soften the blow
(building sea walls is an ex.)
• Electricity generation is largest source of GHG in
US
• Conservation & efficiency
Our Response
• Natural gas has less impact
• Carbon sequestration would allow current
practices to continue
• Transportation is 2nd largest source
• Cars are highly inefficient (15%)
• Alternative engines, driving less, public
transportation are possibilities
Our Response
• Sustainable agriculture & land management
• Reduce methane emissions from rice fields,
cattle
• Preserving forests; increase reforestation
• Recovering methane from landfills, treating
wastewater, energy from solid waste
Our Response
Kyoto Protocol
• Began as the UN Framework Convention on
Climate Change
• Binding international treaty to reduce GHG
emissions (US refused to sign)
• In the 10 years after Rio conference (1992) – US
increased GHG by 13%; Germany & UK
decreased by 13 – 18%
Our Response
• Market mechanics – cap and trade
• A carbon offset represents a reduction in
emissions somewhere else - like a renewable
energy or a reforestation project - to balance
out the emissions you cannot reduce.
• Reduce your own carbon footprint
OZONE DEPLETION
•UVA: λ = 320-400nm
Causes tanning
•UVB: 290-320nm;
burns, skin cancer
•UVC: 10-290nm
formation of ozone
Research
CFCs are persistent in the atmosphere
• Rise into the stratosphere over 11-20
years
• Break down under high-energy UV
radiation
–Halogens produced accelerate the
breakdown of O3 to O2
• Each CFC molecule can last 65-385 years
Reducing Effects
• Stop producing all ozone-depleting
chemicals
• 60–100 years of recovery of the O3 layer
• 1987: Montreal Protocol; 1992:
Copenhagen Protocol
• Ozone protocols: prevention is the key
• Substitutes for CFCs are available
Conclusion
• Many factors, including human activities, can
shape atmospheric composition and global
climate.
• Scientists and policymakers are beginning to
understand anthropogenic climate change and
its environmental impacts more fully.
• Reducing greenhouse gas emissions and taking
other actions to mitigate and adapt to climate
change represents the foremost challenge for
our society in the coming years.