Current Climate Change

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Current Climate Change
Ch. 17, Bush
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Outline

• Evidence for recent climate change
• Are humans the cause?
• Potential ecological effects of climate change

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Outline

• Evidence for recent climate change
• Are humans the cause?
• Potential effects of climate change

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Evidence of Temperature Changes

• Three main sources of data
• Direct measurements of temperature
• Location of ice caps and tropical glaciers
• Thickness of ice caps

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Temperature records

• We have accurate records only for the past 120
  years
• Most temperature readings taken at cities which
  are heat islands

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Whaling and Polar Ice caps
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Changes in extent of sea ice
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Thickness of Ice Caps

• Submarines make careful measurements of the
  distance between the ice and the bottom of the
  sea
• Have estimated that the thickness of the ice caps
  have decreased from 3.1m to 1.8m

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Tropical Glaciers are melting

• All tropical glaciers are above 4800 m
• At the current rate of temperature change, it is
  estimated that all will be gone in 50 years

Kilimanjaro
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The effect of melting ice caps

• There is not enough water trapped in the ice caps
  to create Waterworld
• The biggest effect of ice caps melting comes from
  the decrease in ALBEDO

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Albedo brightness
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Ice caps have high albedo
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Outline

• Evidence for recent climate change
• Are humans the cause?
• Potential effects of climate change

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Last glacial period ended 11,000 years ago

• 90 of last 2 million years has been glacial
• For the last 10,000 years, plants and animals
  have been living in an unusually warm environment

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Temperature changes over the years

• The rate of climate change we are currently
  experiencing is only matched by the rapid warming
  at the end of the last ice age

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Temperature changes in history

• Between 1400-1700 the earth was a few degrees
  colder
• Called The Little Ice Age
• Influenced history
• Outcome of battles
• Crops failing causing famine

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Greenhouse effect

• Light energy enters the atmosphere
• Changes to heat energy
• Light energy exits atmosphere but heat energy is
  trapped

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The Greenhouse effect

• The greenhouse effect is not all bad
• Without the greenhouse effect, the earth would
  be, on average, -18 ?C

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Creation of greenhouse gases

• The burning of fossil fuels is increasing the
  greenhouse effect
• Important greenhouse gases
• HCFs, CFCs
• Methane
• CO2
• Water vapour

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Relative contribution of greenhouse gases to
predicted warming

• Other chemicals are actually better at trapping
  heat but CO2 contributes more to the greenhouse
  effect due to the fact that it is way more
  abundant

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CO2 and water vapour

• CO2 causes minor increase in temperature
• Increase in temperature causes more water vapour
  via evaporation
• Water vapour leads to further greenhouse effect
  and higher temperature

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Carbon cycle

• In the natural carbon cycle, respiration and
  decomposition increase CO2
• Photosynthesis decreases CO2
• Burning fossil fuels now contributes to CO2 gain

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Fossil fuels
Fossil fuels are ancient organisms that did not
decompose
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The major culprits
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Carbon sinks

• Each year humanity dumps roughly 8 billion metric
  tons of carbon into the atmosphere
• 6.5 billion tons from fossil fuels and 1.5
  billion from deforestation
• But less than half that total, 3.2 billion tons,
  remains in the atmosphere to warm the planet
• Forests, grasslands, and the waters of the oceans
  are acting as carbon sinks

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Outline

• Evidence for recent climate change
• Are humans the cause?
• Potential effects of climate change

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Potential effects of CO2 increase

• Predicted changes in temperature
• Changes to the natural world
• Changes to human life

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Recent increases in CO2

• Jagged line is caused by seasonal changes in
  photosynthesis in summer N. Hemisphere plants
  use up more CO2

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Pollution can mitigate increases in temperature

• Pollutants such as those from car exhaust are
  causing increases in cloud cover
• Cloud cover increases albedo

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Air pollution increases albedo
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CO2 and temperature changes

• Simulations of temperature changes are becoming
  increasingly accurate

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Predicted temperature change

• Five principal research groups all produce
  climate models
• Differences arise in the predictions made about
  social and political change
• Medium estimate is that the average temperature
  on Earth will rise 3.5 ?C

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Increased photosynthesis
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Planting trees to decrease temp

• Deforestation causes decreases in CO2 absorption
• Planting trees will have the opposite effect
  -gtdecreases CO2

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C4 evolution changing atmospheres

• C4 photosynthesis appears to have evolved at a
  time when O2 was high and CO2 was low and
  temperatures were high

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The global distribution of C4 plants in today's
world

• C4 grasslands (orange) have evolved in the
  tropics and warm temperate regions where C3
  forests (green) are excluded by seasonal drought
  and fire.
• C3 grasses (yellow) remain dominant in cool
  temperate grasslands because C4 grasses are less
  productive at low temperatures.

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Temperature and precipitation
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Climate affects ecology
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Deserts will spread
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N. Hemi. plants will migrate north
Predicted migration of beech and maple trees
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Migration of species

• Industrialization may impede the migration of
  many species
• Temperate species (and island species) may have
  nowhere to migrate to
• If migration can not occur then extinction will
  likely take place

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Cold-adapted species
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Implications to Conservation
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Extinction and global warming

• One study indicated that, by 2050, current
  warming trends could bring about extinction of 15
  to 37 percent of the 1,103 species they studied
• A mere 6 degrees of global warming was enough to
  wipe out up to 95 per cent of the species which
  were alive on earth at the end of the Permian
  period, 250 million years ago

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Arable land will have new locations

• Best conditions for farming will move towards
  poles
• Will be at the latitude of the Canadian Shield
• More irrigation needed as crop land will be drier
• Expected 20 decrease in cultivatable land

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Other reasons why global warming a threat to life
on Earth?

• Incidences of heat attacks, respiratory disease
  and stroke will increase
• Disease and pests are more likely to spread
• Tropical storms, tornadoes, landslides, heatwaves
  and droughts will both increase in number and
  intensity
• Air quality will become poorer
• coastal cities like Miami, New Orleans, Los
  Angeles and Bangkok will be flooded as ocean
  level rises due to melting glaciers
• ocean levels rise, some inland drinking water
  sources will become contaminated by saltwater

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Summary

• The Earth is becoming increasingly warm
• Recently, humans have contributed to this
  phenomenon
• Temperature increases will have severe effects to
  the natural world

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