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An introduction to global climate change

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An introduction to global climate change On August 29, 2005, Hurricane Katrina landed east of New Orleans The costliest ($134 billion in damage) storm ever – PowerPoint PPT presentation

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Title: An introduction to global climate change


1
An introduction to global climate change
  • On August 29, 2005, Hurricane Katrina landed east
    of New Orleans
  • The costliest (134 billion in damage) storm ever
  • The deadliest storm (killing 1,800) since 1928
  • Leaving mountains of debris, ruined homes and
    lives
  • A month later, Hurricane Rita hit Louisiana and
    Texas
  • 2005 had a record 27 named storms
  • 2007 had 15 and 2008 had 18 named storms
  • There is a link between hurricanes and global
    warming
  • Warmer oceans create humid air, leading to
    hurricanes

2
Number of category 4 and 5 hurricanes
3
Structure and temperature of the atmosphere
4
Weather
  • Weather day-to-day variations in temperature,
    air pressure, wind, humidity, precipitation
  • Climate the result of long-term regional weather
    patterns
  • Meteorology the study of the atmosphere (weather
    and climate)
  • The atmosphere-ocean-land system is a huge
    weather engine
  • Driven by the Sun and affected by Earths
    rotation and tilt
  • Solar energy is reflected (29) or absorbed by
    Earth
  • Absorbed energy heats the ocean, land, and
    atmosphere

5
Solar-energy balance
6
Climate is
  • Climate the general patterns of weather that
    characterize different regions of the world
  • Climate results from all the combined elements of
  • General atmospheric circulation patterns and
    precipitation
  • Wind and weather systems
  • Rotation and tilt of Earth, which creates seasons

7
Synopsis of global climate change
  • In 2007, scientists from the Intergovernmental
    Panel on Climate Change (IPCC) sifted through
    thousands of studies and published the Fourth
    Assessment Report (AR4)
  • The report concluded that warming of the climate
    is unequivocal
  • The atmosphere and oceans are warmer
  • Sea levels are rising and glaciers are melting
  • There are more extreme weather events

8
Annual mean global surface temperature anomalies
9
The IPCCs report
  • The report concluded that it is very likely (90
    probability) that warming is caused by human
    factors
  • Increased greenhouse gases (GHGs) trap infrared
    radiation
  • GHGs come from burning fossil fuels
  • Along with deforestation
  • The major GHG CO2
  • Responses to climate change
  • Mitigation reducing GHG emissions
  • Adaptation adjusting to climate change

10
Atmospheric carbon dioxide concentrations
11
IPCC
  • Founded in 1988 by the UN Environmental Program
    and the World Meteorological Society to provide
    accurate and relevant information leading to
    understanding human-induced climate change
  • The AR4 report had over 2,000 experts from 154
    countries
  • Risk assessment is the climate changing?
  • Risk management how do we adapt and mitigate
    effects?

12
Third assessment
  • The IPCCs 2001 report showed
  • Increasing information shows a warming world
  • Humans are changing the atmosphere, which will
    affect climate
  • We have increased confidence in models of future
    climate change
  • Stronger evidence that most recent warming is
    human-caused
  • Human influences will continue to change the
    atmosphere
  • Temperature and sea levels are rising
  • We need more information and understanding

13
A Nobel Effort
  • The 2007 Nobel Peace Prize went to the IPCC and
    former Vice President Al Gore the leading
    advocate of the need to take action on climate
    change
  • For their efforts to disseminate knowledge about
    man-made climate change and to lay groundwork to
    counter it
  • Gore also was awarded the Academy Award for his
    film An Inconvenient Truth

14
Climates in the past
  • It is harder to find evidence of climate change
    the further into the past we search
  • Records of temperature, precipitation, storms
    have been kept for only 100 years
  • Since 1880, especially since 1976, our climate
    warmed
  • Proxies records providing information on climate
  • Using temperature, ice cover, precipitation, tree
    rings, pollen, landscapes, marine sediments,
    corals, etc.
  • Earth warmed from 1100 to 1300 A.D.
  • Little Ice Age 14001850

15
Ice cores
  • Analyzing ice cores from Greenland and the
    Antarctic shows global climate can change within
    decades
  • Uses CO2 and CH4 (methane) and isotopes of O and
    H
  • Climate oscillates between ice ages and warm
    periods
  • Ice ages tie up water in glaciers, lowering sea
    levels
  • 8 glacial periods occurred over the past 800,000
    years
  • Ice ages have lower GHGs and temperatures
  • CO2 levels ranged between 150 and 280 ppm
  • Milanovitch cycles climate oscillations due to
    Earths orbit
  • Periodic intervals of 100,000, 41,000, and 23,000
    years

16
Rapid changes
  • Rapid climatic fluctuations during glaciation and
    warmer times
  • The Younger Dryas event 11,700 years ago
  • Dryas a genus of arctic flower
  • Arctic temperatures rose 7ºC in 50 years
  • Caused enormous impact on living systems
  • Warming was not caused by changing solar output

17
Oceans and climate
  • Oceans play a dominant role in determining
    climate
  • They are a major source of water and heat
  • Evaporation supplies water vapor to the
    atmosphere
  • Condensation supplies heat to the atmosphere
  • Heat capacity oceans absorb energy with heated
    water
  • Oceans convey heat through currents
  • Thermohaline circulation pattern the effects of
    temperature and salinity on the density of
    seawater
  • This giant, complex conveyor belt moves water
    from the surface to deep oceans and back

18
The oceanic conveyor system
19
Thermohaline circulation affects climate
  • The movement of warm water toward the North
    Atlantic transfers enormous amounts of heat
    toward Europe, providing a much warmer than
    expected climate
  • The circulation pattern cycles over 1,000 years
  • It is vital to maintaining current climate
    conditions
  • In the past, the conveyor system has been
    interrupted
  • Abruptly changing the climate
  • Large amounts of fresh water lower waters
    density
  • Preventing the sinking of surface waters
  • Slowing the northern movement of warmer, saltier
    water

20
Heinrich events
  • Heinrich events fresh water from melting
    icebergs from the polar ice cap dilutes salt
    water
  • Six times in the past 75,000 years
  • Diluted water doesnt sink
  • The conveyor system is shifted southward to
    Bermuda (instead of Greenland)
  • The climate cools in a few decades
  • Return of the normal pattern abruptly warms the
    climate
  • The Younger Dryas event involved dammed-up water
    from glacial Lake Agassiz entering the St.
    Lawrence

21
What if ?
  • Extended global warming will
  • Increase precipitation over the North Atlantic
  • Melt sea ice and ice caps
  • The conveyor will decrease over the 21st century
  • The Achilles heel of our climate system
    weakening of the conveyor and a changed climate
  • Especially in the northern latitudes

22
The Earth as a greenhouse
  • Factors that influence climate
  • Internal components oceans, atmosphere, snow,
    ice
  • External factors solar radiation, Earths
    rotation and orbit, gaseous makeup of the
    atmosphere
  • Radiative forcing the influence of any factor on
    the energy balance of the atmosphere-ocean-land
    system
  • Positive (negative) forcing leads to warming
    (cooling)
  • Forcing is measured in Watts/m2
  • Solar radiation entering the atmosphere 340
    W/m2
  • Radiation is acted on by forcing factors

23
Warming processes
  • Greenhouse gases (GHGs) water vapor, CO2, other
    gases
  • Light energy goes through the atmosphere to Earth
  • Earth absorbs and converts energy to heat
  • Infrared heat energy radiates back to space
  • GHGs (but not N2 and O2) in the troposphere
    absorb some infrared radiation
  • Direct it back to Earths surface
  • The greenhouse effect was first recognized in
    1827
  • It is now firmly established

24
GHGs insulate Earth
  • GHGs delay the loss of infrared heat (energy)
  • Without insulation, Earth would be -19C instead
    of 14C
  • Life would be impossible
  • Earths global climate depends on the
    concentration of GHGs
  • Changing amounts of GHGs change positive forcing
    agents, which would change the climate
  • Tropospheric ozone has a positive forcing effect
  • Varying with time and location

25
The greenhouse effect
26
Cooling processes
  • Planetary albedo sunlight reflected by clouds
  • Contributes to overall cooling by preventing
    warming
  • Low-flying clouds have a negative forcing effect
  • High-flying, wispy clouds have a positive forcing
    effect
  • Absorb solar radiation and emit infrared
    radiation
  • Snow and ice contribute to albedo by reflecting
    sunlight

27
Volcanoes and aerosols
  • Volcanic activity can lead to planetary cooling
  • Reflects radiation from particles and aerosols
  • Aerosols microscopic liquid or solid particles
    from land or water
  • Industrial aerosols (pollution) cancel some GHG
    warming
  • Sulfates, nitrates, dust, soot from industry and
    forest fires
  • Sooty aerosols (from fires) warming effect
  • Reduced pollution in the U.S. and Europe
    decreased aerosols
  • Chinas and Indias pollution has increased
    aerosols

28
Global warming and cooling
29
Solar variability
  • Variation in the Suns radiation influences the
    climate
  • Changes in solar radiation occur on 11-year
    cycles
  • Solar radiation increases during high sunspot
    activity
  • Sunspots block cosmic ray intensity
  • Solar output declined in 1985 and continued for
    20 years
  • But global temperatures rose rapidly
  • The IPCC AR4 concluded that GHGs were 13 times
    more responsible for warming temperatures than
    solar changes

30
Thus
  • Global atmospheric temperatures are a balance
    between positive and negative forcing from
    natural causes (volcanoes, clouds, natural GHGs,
    solar irradiance) and forcing from anthropogenic
    causes (sulfate aerosols, soot, ozone, increased
    GHGs)
  • Forcing agents result in climate fluctuations
  • It is hard to say any one event or extreme season
    is due to humans
  • But climate has shifted enough to generate
    international attention

31
Evidence of climate change
  • Weather varies naturally year to year
  • Local temperatures may not follow global averages
  • But the 10 warmest years on record were 19972008
  • 2005 set a record highthe warmest since the late
    1800s
  • The average global temperature has risen 0.6C
    since the mid-1970s (0.2C/decade)
  • Warming is happening everywhere
  • Most rapidly at high latitudes of the Northern
    Hemisphere
  • The warming is a consequence of an enhanced
    greenhouse effect

32
Ocean warming
  • Recently, the upper 3,000 meters of the ocean
    have warmed
  • Dwarfing warming of the atmosphere
  • 90 of the heat increase of Earths systems
  • Over the last decade, oceans have absorbed most
    of the non-atmospheric heat
  • A long-term consequence the impact of this
    stored heat as it comes into equilibrium with the
    atmosphere
  • It will increase atmospheric and land heat even
    more
  • A short-term consequence unprecedented rising
    sea levels
  • Thermal expansion and melting glaciers and ice
    caps

33
The rise in global mean sea level
34
Other observed changes by the IPCC AR4
  • Changes are consistent with GHG-caused climate
    change
  • Increased warm temperature extremes
  • Decreased cold temperature extremes
  • Spring comes earlier, fall later, in the Northern
    Hemisphere
  • Ecosystems are out of sync
  • Tree deaths and insect damage
  • Heat waves are increasing in intensity and
    frequency
  • Droughts are increasing in intensity and
    frequency
  • 60 of the U.S. is in a drought that started in
    the 1990s

35
More changes reported by the IPCC
  • Rising Arctic temperatures have caused major
    shrinkage of Arctic sea ice (11.7 in 10 years)
  • Alaska, Siberia, Canada have warmed 5F in
    summer, 10F in winter
  • Spring comes 2 weeks earlier than 10 years ago
  • The polar ice cap has lost 20 of its volume in
    20 years
  • Permafrost is melting
  • Unprecedented melting of the Greenland Ice Sheet
    can raise ocean levels 23 feet

36
Decline of Arctic sea ice
37
Other changes reported by the IPCC
  • Antarctica temperatures have risen 0.50.85C
  • The West Antarctic Ice Sheet (WAIS) is shrinking
    and can raise sea levels by 1620 feet
  • Accelerating glacier melting since 1990
  • Changing patterns of precipitation and flooding
  • Greater amounts from 30 N and S poleward
  • More intense and frequent tropical hurricanes
  • Marine fish populations have shifted northward
  • Ocean acidification decreased pH due to CO2
    absorption
  • The surface oceans chemistry is actually changing

38
Carbon dioxide levels
  • CO2 levels oscillate 57 ppm, reflecting
    seasonal changes in photosynthesis and
    respiration
  • Fall through spring respiration increases CO2
    levels
  • Spring through fall photosynthesis decreases CO2
  • By 2009, atmospheric CO2 levels 338 ppm
  • 39 higher than before the Industrial Revolution
  • Higher than in the past 800,000 years
  • Fossil fuels increase CO2 levels
  • 1 kg of fossil fuel burned releases 3 kg CO2
  • Eight billion tons (gigatons, Gt) of fossil fuel
    carbon/year

39
Sources of carbon dioxide
  • Half of fossil fuel carbon comes from
    industrialized nations
  • Burning forests
  • Over the past 50 years, release of carbon has
    tripled
  • Half of the carbon is removed by sinks
  • Sinks burning fossil fuels should add 8 GtC/year
    to the air
  • But only 3.3 GtC/year are actually added
  • Carbon sinks (the ocean, biota) absorb CO2
  • Oceans take up CO2 by phytoplankton or
    undersaturation
  • But there are limitations to uptake
  • Forests are valuable for their ability to
    sequester carbon

40
Sources of carbon dioxide emissions from fossil
fuels
41
Other gases
  • Other gases absorb infrared radiation
  • Adding to the insulating effect of carbon dioxide
  • Most are anthropogenic sources and are increasing
  • Water vapor the most abundant GHG
  • Its tropospheric concentration varies, but is
    rising
  • Higher temperatures increase evaporation and
    water vapor (humidity)
  • Higher humidity traps more heat, causing more
    warming (positive feedback)

42
Other GHGs
  • Methane 20 times more effective than CO2 in
    heating
  • From microbial fermentation (in wetlands), green
    plants
  • Two-thirds of emissions are from human sources
    livestock, landfills, coal mines, natural gas,
    rice cultivation, manure
  • Rising at 0.8 ppb/year, it is more abundant than
    in the past 800,000 years
  • Nitrous oxide has increased 18 over the last
    200 years
  • From agriculture, oceans, biomass burning, fossil
    fuel burning, industry, anaerobic denitrification
    (fertilizers)
  • Warms the troposphere and destroys stratospheric
    ozone

43
Ozone and CFCs
  • Ozone a short-lived but potent GHG in the
    troposphere
  • From sunlight acting on pollutants
  • Has increased 36 since 1750
  • From traffic, forest fires, agricultural wastes
  • CFC and other halocarbons
  • Long-lived GHGs causing warming and ozone
    destruction
  • From refrigerants, solvents, fire retardants
  • They absorb 10,000 times more infrared energy
    than CO2
  • Levels are slowly declining but will remain for
    decades

44
Future changes in climate
  • Happening now higher temperatures, rising seas,
    heat waves, droughts, intense storms, season
    shifts, melting ice
  • GHG levels are rising
  • Along with fossil fuel demand and population
  • Emissions will rise 35 (2030) and 100 (2050)
  • Modeling global climate computing power has
    increased
  • Can explore the potential future impacts of
    rising GHGs
  • Atmospheric-ocean general circulation models
    (AOGCMs)
  • Simulate long-term climatic conditions

45
Significant findings of climate models
  • Equilibrium climate sensitivity if atmospheric
    CO2 stays at 550 ppm (double preindustrial
    values), temperature will rise 3C (24.5C) by
    2050
  • Higher latitudes and continental interiors will
    warm most
  • But it will be warmer everywhere
  • Snow cover and sea ice will decrease, opening up
    the Arctic Ocean by 2100
  • Shrinking glaciers and ice caps will increase sea
    levels
  • 90 of upper permafrost will thaw

46
More findings
  • Warmer, dilute upper layers of the North Atlantic
    Ocean will lead to decreased (but not collapsed)
    thermohaline circulation
  • Increased storm intensities, higher wind speeds
    and waves, more intense precipitation
  • More frequent, longer-lasting heat waves
  • Longer growing seasons, shorter frost days
  • Dry areas will get dryer, wet areas will get
    wetter
  • Extreme droughts will affect up to 30 of the
    world
  • Ecosystems (polar ecosystems, coral reefs,
    rainforests) will be profoundly affected,
    increasing species extinctions

47
What about the Antarctic?
  • The Antarctic could be a huge factor in rising
    sea levels
  • Greenland and Antarctic ice sheets hold enough
    water to raise sea levels 230 feet
  • Snowfall has not changed in the past 50 years
  • 87 of the 244 glaciers are melting
  • The melting ice sheet is raising sea levels 0.4
    mm/year
  • Higher continental temperatures (3C)
  • Models project a 5 snowfall increase for each
    1C temperature rise

48
Climate change in the U.S.
  • All impacts are expected to continue and/or
    increase
  • Impacts are greater in Alaska than any other U.S.
    region
  • Changes in the U.S. over the past 50100 years
    include
  • Average temperature has risen 2F
  • Wetter areas are wetter, dryer areas are dryer
  • Heavy downpours and storms have increased
  • More extreme and frequent weather events
  • Stronger Atlantic hurricanes
  • Arctic sea ice is declining rapidly

49
Response to climate change
  • Industries and transportation network are locked
    into using fossil fuels
  • Massive emissions of GHGs will continue
  • Adaptation anticipate harm and plan adaptive
    responses to decrease vulnerability of people,
    property, and the biosphere
  • Mitigation take action to prevent emissions
  • Skeptics about global warming exist
  • Fossil fuel industry, Rush Limbaugh, conservative
    think tanks, some scientists
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