Transcript Studying Climate Change: Proxy Indicators

The Maldives:
Rising seas may flood the Maldives
• Island paradise
• Rising seas due to global climate change
could submerge them
– Erode beaches, cause
flooding
– Damage coral reefs
– Contaminate fresh water
• Residents have evacuated
the lowest-lying islands
What is climate change?
• Climate change is the fastest-developing area of
environmental science
• Climate = an area’s long-term atmospheric conditions
– Temperature, moisture, wind, precipitation, etc.
– Weather = short-term conditions at localized sites
• Global climate change = describes trends and variations in
Earth’s climate
– Temperature, precipitation, storm frequency
• Global warming and climate change are not the same
Global warming
• Global warming = an increase in Earth’s average
temperature
– Only one aspect of climate change
• Climate change and global warming refer to current
trends
– Earth’s climate has varied naturally through time
• The current rapid climatic changes are due to humans
– Fossil fuels and deforestation
The sun and atmosphere keep Earth warm
• Four factors exert most influence on climate:
• The sun = without it, Earth would be dark and frozen
– Supplies most of Earth’s energy
• The atmosphere = without it, Earth’s temperature would
be much colder
• The oceans = shape climate by storing and transporting
heat and moisture
• How Earth spins, tilts, and moves through space
influences how the climate varies over long periods of
time
The fate of solar radiation
• The atmosphere, land, ice, and water absorb 70% of
incoming solar radiation – 30% is reflected back
Greenhouse gases warm the lower
atmosphere
• Earth’s surface absorbs solar radiation, warms up, and emits
infrared radiation
• Greenhouse gases = atmospheric gases that absorb infrared
radiation
– Water vapor, ozone, carbon dioxide, nitrous oxide, methane,
halocarbons [chlorofluorocarbons (CFCs)]
• Greenhouse gases then re-emit infrared energy, to earth and
space
• Greenhouse effect = greenhouse gases keeping the surface
warm
The greenhouse effect is natural
• Greenhouse gases have always been in the
atmosphere
• We are not worried about the natural greenhouse
effect (we need it)
– Anthropogenic increase is worrisome
Carbon dioxide is of primary concern
• It is not the most potent greenhouse gas, but
there is a lot of it
– The major contributor to the greenhouse effect
• CO2 exerts six times more impact than methane,
nitrous oxide, and halocarbons combined
What caused levels of CO2 to increase?
• Burning fossil fuels moves CO2 from lithospheric
stores into the atmosphere
– The main reason for increased atmospheric CO2
• Deforestation contributes to rising atmospheric CO2
– Forests serve as reservoirs for carbon
– Removing trees reduces the carbon dioxide absorbed
from the atmosphere
• Humans have increased atmospheric CO2 from 280
parts per million (ppm) to 389 ppm
– The highest levels in more than 800,000 years
– OMG right?
Fluxes of carbon dioxide
Other greenhouse gases add to warming
• Methane = fossil fuels, livestock, landfills, crops (rice)
• Nitrous oxide = feedlots, chemical manufacturing plants,
auto emissions, and synthetic nitrogen fertilizers
• Ozone levels have risen 36% due to photochemical smog
• Halocarbon gases (CFCs) are declining due to the Montreal
Protocol
• Water vapor = the most abundant greenhouse gas
– Contributes most to the natural greenhouse effect
– Concentrations have not changed
U.S. emissions of major greenhouse
gases
Feedback complicates our predictions
• Tropospheric warming will transfer more water to the air
– But the effects are uncertain
• A positive feedback loop? = more water vapor … more
warming … more evaporation … more water vapor …
• A negative feedback loop? = more water vapor … more
clouds … shade and cool Earth
• Minor modifications of the atmosphere could lead to major
effects on climate
Most aerosols exert a cooling effect
• Aerosols = microscopic droplets and particles
– Can have either a warming or a cooling effect
• Soot (black carbon aerosols) causes warming by
absorbing solar energy
– Most tropospheric aerosols cool the atmosphere
by reflecting the sun’s rays
Milankovitch cycles influence climate
• Milankovitch cycles =
periodic changes in Earth’s
rotation and orbit around the
sun
– Alter the way solar radiation is
distributed over Earth
• Modify patterns of
atmospheric heating
– Triggering climate variation
– For example, periods of cold
glaciation and warm
interglacial times
Solar output and ocean absorption
influence climate
• Solar output = the sun varies in the radiation it emits
– Variation in solar energy (e.g., solar flares) has not been
great enough to change Earth’s temperature
• Ocean absorption = the ocean holds 50 times more
carbon than the atmosphere
– Slowing global warming but not preventing it
• Warmer oceans absorb less CO2
– A positive feedback effect that accelerates warming
Proxy indicators tell us about the past
• Proxy indicators = indirect evidence
• Ice caps, ice sheets, and glaciers:
- Trapped bubbles in ice cores provide a timescale of:
- Atmospheric composition, greenhouse gas
concentrations, temperature trends
- Snowfall, solar activity, and frequency of fires
Ice cores from Antarctica
• Ice cores let us go back in time 800,000 years
More proxy indicators
• Cores in sediment beds preserve pollen grains and other
plant remnants
• Tree rings indicate age, precipitation, droughts, and fire
history
• In arid regions, packrats carry seeds and plants to their
middens (dens)
– Plant parts can be preserved for centuries
• Researchers gather data on past ocean conditions from coral
reefs
• Scientists combine multiple records to get a global
perspective
Models help us predict the future
• Climate models = programs
combine what is known
about:
– Atmospheric and ocean
circulation
– Atmosphere–ocean
interactions
– Feedback mechanisms
– Etc...
Models simulate climate processes to predict
climate change
Global Climate Models
The State of the Art in Modeling the Climate (2005)
Results from three simulations
• Figure (a) shows natural
climate factors only
• Figure (b) shows only human
factors
– Greenhouse gas emissions
• Figure (c) shows both factors
• (Red line is observed climate data)
Current and future trends and impacts
• Evidence that climate conditions have changed since
industrialization is everywhere
– Fishermen in the Maldives, ranchers in Texas, homeowners in
Florida, etc.
• Scientific evidence that climate has changed is
overwhelming and indisputable
• Intergovernmental Panel on Climate Change (IPCC) was
established in 1988
– Composed of hundreds of international scientists and
government officials
The IPCC’s fourth assessment report (2007)
• The IPCC reports on the synthesis of scientific
information concerning climate change
• Global consensus of scientific climate research
• Summarized thousands of studies
• Evidence is overwhelming
Temperatures continue to increase
• Average surface temperatures increased 0.74 °C
since 1906
– Most of the increase occurred in the last few decades
– Number of extremely hot days have increased
– The 16 warmest years on record have been since 1990
The future will be hotter
• In the next 20 years, temperatures will rise 0.4°C
• At the end of the 21st century, temperatures will be 1.8–
4.0 °C higher than today’s
• We will have more unusually hot days and heat waves
• Polar areas will have the most intense warming
• Sea surface temperatures will rise
• Hurricanes and tropical storms will increase in power and
duration
Temperatures will rise globally
Projected increases in surface temperature
for 2090–2099 relative to 1980–1999
Precipitation is changing, too
• Some regions are receiving more precipitation
than usual, and others are receiving less
• Droughts have become more frequent and
severe
– Harming agriculture, increasing soil erosion,
reducing water supplies, and triggering fires
• Heavy rains contribute to flooding
– Killing people, destroying homes, and inflicting
billions of dollars in damage
Projected changes in precipitation
Precipitation will increase at high latitudes
and decrease at low and middle latitudes
Figure SPM.7
Relative changes in precipitation (in percent) for the period 2090–2099, relative to 1980–1999. Values
are multi-model averages based on the SRES A1B scenario for December to February (left) and June to
August (right). White areas are where less than 66% of the models agree in the sign of the change and
stippled areas are where more than 90% of the models agree in the sign of the change. {Figure 10.9}
Melting snow and ice
• Glaciers are disappearing
– Glaciers on tropical mountaintops have disappeared
– The remaining 26 of 150 glaciers in Glacier National Park will be
gone by 2020 or 2030
– Reducing summertime water supplies
• Melting of Greenland’s Arctic ice sheet is accelerating
• Warmer water is melting Antarctic coastal ice shelves
– Interior snow is increasing due to more precipitation
• Melting ice exposes darker, less-reflective surfaces, which
absorb more sunlight, causing more melting
2007 vs 2005
Melting ice...
• Nations are rushing to exploit underwater oil and mineral
resources made available by newly opened shipping lanes
• Permafrost (permanently frozen ground) is thawing
– Destabilizing soil, buildings, etc. and releasing methane
http://www.worldviewofglobalwarming.org/pages/glaciers.html
Rising sea levels
• Runoff from melting glaciers and ice will cause
sea levels to rise
• As oceans warm, they expand
– Leading to beach erosion, coastal floods, and
intrusion of salt water into aquifers
Coastal areas will flood
• Storm surge = temporary, localized rise in sea level
– Caused by the high tides and winds of storms
• Cities will be flooded
– 53% of people in the U.S. live in coastal areas
Rising sea levels will devastate coasts
• 1 million acres of Louisiana’s wetlands are gone
– Rising sea levels eat away vegetation
– Dams upriver decrease siltation
– Pollution from the Deepwater Horizon
• Millions of people will be displaced from coastal areas
Coral reefs are threatened
• Coral reefs are habitat for food fish
– Snorkeling and scuba diving sites for tourism
• Warmer waters contribute to coral bleaching
– Which kills coral
• Increased CO2 is acidifying the ocean
– Organisms can’t build their exoskeletons
• Oceans have already decreased by 0.1 pH unit
– Enough to kill most coral reefs
Climate change affects organisms and
ecosystems
• Organisms are adapted to their environments
• Global warming modifies temperature-dependent
phenomena (e.g., timing of migration, breeding)
• Animals and plants will move toward the poles or
upward in elevation
– 20–30% of species will be threatened with extinction
• Droughts, fire, and disease will decrease plant
growth
Animals and plants have nowhere to go
• Animals and plants adopted to montane environments will
be forced uphill until there is no place to go
Climate change affects people
• Societies are feeling the impacts of climate change
• Agriculture: shortened growing seasons, decreased
production, crops more susceptible to droughts
– Increasing hunger
• Forestry: increased fires, invasive species
– Insect and disease outbreaks
• Health: heat waves and stress can cause death
– Respiratory ailments, expansion of tropical diseases
– Disease and sanitation problems from flooding
– Drowning from storms
Climate change affects economics
• Costs will outweigh benefits of climate change
• It will widen the gap between rich and poor
– Those with less wealth and technology will suffer most
• External costs of damages will be $10–350/ton of carbon
• It will cost 1–5% GDP on average globally
– Poor nations will lose more than rich ones
• The Stern Review predicts it will cost 5–20% of GDP by 2200
– Investing 1% of GDP now could avoid these costs
Impacts will vary regionally
• Where we live will determine how we experience the
impacts of climate change
• Temperature changes have been greatest near the poles
– Melting ice sheets, thinning ice, increasing storms, etc.
– Harder for people and polar bears to hunt
• U.S. temperatures will continue rising
– Plant and animal communities will shift north and upward
– More intense extreme weather events
• The southern U.S. will get drier, the northern wetter
– Sea levels will rise and may be worse in the East
Impacts of climate change
The Arctic has suffered
the most so far
U.S. temperatures will continue to rise
Impacts of climate change will vary
Are we responsible for climate change?
• Scientists agree that increased greenhouse gases are
causing global warming
– Burning fossil fuels is increasing greenhouse gases
• In 2005, scientists from 11 nations issued a joint
statement urging political leaders to take action
• There is a broad and clear scientific consensus that
climate change is a pressing issue
– But many people deny what is happening
• People will admit the climate is changing
– But doubt we are the cause
The debate over climate change is over
• Conservative think tanks and industry-sponsored
scientists cast doubt on the scientific consensus
• The news media tries to present two sides to an
issue
– But the sides’ arguments are not equally supported
by evidence
• Most Americans accept that fossil fuel
consumption is changing the planet
Electricity generation
A coal-fired,
electricity-generating
power plant
• The largest source of U.S. CO2 emissions
– 70% of electricity comes from fossil fuels
– Coal causes 50% of emissions
• To reduce fossil fuel use:
– Encourage conservation and efficiency
– Switch to cleaner and renewable energy sources
Conservation and efficiency
• We can make lifestyle choices to reduce
electricity use
– Use fewer greenhouse-gas-producing appliances
– Use electricity more efficiently
Sources of electricity
• We need to switch to clean energy sources
– Nuclear power, biomass energy, solar, wind, etc.
• We need to consider how we use fossil fuels
– Switching from coal to natural gas cuts emissions 50%
– Cogeneration produces fewer emissions
• Carbon capture = removes CO2 from power plant
emissions
• Carbon sequestration (storage) = storing carbon
underground where it will not seep out
– We can’t store enough CO2 to make a difference
Transportation
• 2nd largest source of
U.S. greenhouse gases
– Cars are inefficient
• Ways to help:
– More efficient cars
– Drive less and use
public transportation
– Ride a bike!
U.S. public transportation
saves 4.2 billion gallons
of gasoline and 37 million
metric tons of CO2
emissions per year
Conventional cars are inefficient
We can reduce emissions in other ways
• Agriculture: sustainable land management lets soil store more
carbon
• Reduce methane emissions from rice and cattle
• Grow renewable biofuels
• Forestry: reforest cleared land, preserve existing forests
• Store carbon in trees and soil
• Waste management: treating wastewater
• Generating electricity by incinerating waste
• Using the methane from landfills
• Individuals can recycle, compost, reduce, or reuse goods
We need to follow multiple strategies
• There is no magic bullet for mitigating climate
change
Kyoto Protocol
• International agreement to reduce
greenhouse gas emissions
• NOT ratified by: USA, Afghanistan, Andorra,
and S. Sudan (Canada backed out)
States and cities are advancing policies
• The U.S. federal government is not taking
action
– State and local governments are
• By 2010, 1,000 mayors signed the U.S.
Mayors Climate Protection Agreement
– To meet or beat Kyoto Protocol guidelines
• California passed the Global Warming Solutions Act
- To cut emissions 25% by 2020
• Regional Greenhouse Gas Initiative
(RGGI) in 2007
- 10 northeastern states
- Set up a cap-and-trade program
You can reduce your carbon footprint
• People may apply many strategies to decrease
their footprint
• YOU must help drive personal and societal
changes needed to mitigate climate change
• Global climate change may be the biggest
challenge facing us and our children
– We can make a difference, remember the ozone!