Climate Change Other Factors

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• Climate Change Other Factors
• Sunspots
• May affect amount of incoming radiation
• Solar output varies sunspots, solar flares
• Sunspots are magnetic storms that appear as dark
  patches on suns surface
• Number and size are maximal every 11 years
• Solar output ca. 0.1 higher than normal during
  maxima

2
http//calspace.ucsd.edu/virtualmuseum/climatechan
ge2/06_3.shtml
3

• Climate Change Other Factors
• Sunspots
• May affect amount of incoming radiation
• Solar output varies sunspots, solar flares
• Researchers have correlated minima with Little
  Ice Age in Europe during 17th and early 18th
  centuries when sun was 0.25 dimmer than normal
• 20th century dominated by sunspot maxima
• Some predictions that 21st century will see
  minima
• Estimated that sunspot variability may have
  contributed to half of 0.55 oC warming since 1860
  and one third of warming since 1970 (Lean et al.)

4
http//calspace.ucsd.edu/virtualmuseum/climatechan
ge2/06_3.shtml
5

• Climate Change Other Factors
• Volcanism
• Affects water vapor, particles, sulfides,
  nitrates
• Generally leads to planetary cooling
• Theory about extinctions at P/T K/T boundaries
• Mt. St. Helens and Mt. Pinatubo eruptions caused
  planetary cooling, and those were small eruptions
• Photosynthesis Transpiration
• Affect CO2, water vapor
• As CO2 rises, some plants
• Photosynthesize more rapidly
• Grow faster
• Incorporate more CO2 into biomass
• Keep their stomata open less
• Transpiration releases water vapor into
  atmosphere
• Less transpiration when CO2 is higher (stomata)

6

• Climate Change Other Factors
• Soil Characteristics
• Affect heat capacity and retention
• More hydrated soil leads to
• Darker color (less reflective)
• More heat capacity (high heat capacity of water)
• Albedo (Reflectivity)
• Earths surface varies considerably (mean
  0.30-0.36)
• Ice/Snow highly reflective (0.9)
• Clouds vary in reflectivity
• Land generally less reflective
• Changes in land use affect albedo
• Desertification increases albedo
• Forest 0.12
• Grassland 0.19
• Desert 0.30

7

• Climate Change Other Factors
• Wind Patterns
• Affect atmospheric circulation and heat flux
• Affect circulation of oceans and lakes
• Wind mixes warm water down and brings cooler,
  nutrient-rich water to surface
• May affect photosynthesis removal of CO2 from
  atmosphere
• Ex El Niño results from changes in wind
  patterns
• Spectral Shifts in Incoming Radiation
• Particles and gases in atmosphere
• Scatter higher-energy blue light
• Allow lower-energy red light to pass
• Affect light available for photosynthesis

8

• Climate Change Other Factors
• Astronomical Factors
• Earths axis precesses on a 26,000 year cycle
• Axial tilt varies on a 41,000 year cycle
• Orbital eccentricity has a 100,000 year cycle
• Correlated with glacial periods over past 750,000
  years

9
http//www.clearlight.com/mhieb/WVFossils/ice_age
s.html
10

• Climate Change Other Factors
• Astronomical Factors
• Earths axis precesses on a 26,000 year cycle
• Axial tilt varies on a 41,000 year cycle
• Orbital eccentricity has a 100,000 year cycle
• Correlated with glacial periods over past 750,000
  years
• Geological Factors
• Plate movement may affect ocean circulation
  patterns
• Ex Antarctica
• Changes in basin morphology alter weather
  patterns
• Changes in plate positions and relative heights
  of land masses can confound measurements of sea
  level (satellite data only since 1993)

11

• Climate Change Other Factors
• Many factors affect global climate in multiple
  ways
• Ex Clouds absorb re-radiated long-wavelength
  radiation but also may reflect incoming
  short-wavelength radiation
• Net effect is cooling
• Ex Particles in the atmosphere reduce the
  re-radiation of long-wavelength radiation but
  also reflect incoming short-wavelength radiation
• Net effect is probably warming at low levels but
  cooling at high levels (e.g. following a large
  volcanic eruption)
• Uncertainty about impact of many factors

12
IPCC AR4
13

• Climate Change Effects
• Climate change may have positive and negative
  effects for humans and ecosystems
• Media typically portrays climate change as
  negative
• Periods of warming and cooling are part of
  earths climate history
• Earth has experienced at least 20 glacial periods
  in the last several million years
• Transitions between glacial and interglacial
  periods may be abrupt
• Ice core data from South Greenland suggest a
  temperature rise of 7 oC in 50 years at end of
  last glacial period (10,700 years ago),
  accompanied by
• Reduction in storms
• 50 increase in precipitation
• Decrease in atmospheric dust

14

• Climate Change Effects
• Negative
• Sea Level
• Warming should lead to melting of glaciers and
  ice caps, causing sea level to rise
• Warming also causes thermal expansion of water,
  leading to additional sea level rise
• Melting of all ice should lead to sea level rise
  of 70 m

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South Cascade Glacier - Washington
http//eces.org/ec/globalwarming/sealevel.shtml
16
http//www.grida.no/climate/vital/19.htm
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• Climate Change Effects
• Negative
• Sea Level
• Since 1880, sea level has been rising at a rate
  of 15 cm century-1
• Accelerating since 1940s
• Rates at ends of glacial periods 40 cm century-1
• Sizes of polar ice sheets have been fairly
  constant over last century
• Temperate glaciers have shrunk visibly
• Warming should lead to increased atmospheric
  moisture and precipitation, which should cause a
  net growth of polar ice caps

18

• Climate Change Effects
• Negative
• Sea Level
• Examples
• Estimated that sea level rise of 1 m would
  displace 15 million people in UK
• Estimated that measures to protect low lying land
  in US from damage would cost gt 100 billion
• Bangladesh More than 17 million people live
  less than 1 m above sea level
• 38 of food production tied to flood plains
• Maldives Highest elevation 24 m
• Japan Fishing rights around pinnacle
• AOSIS (Alliance of Small Island States) Strong
  concerns about sea level rise