Download Lecture 8

Current Climate Change
Ch. 17, Bush
Outline
 Evidence
 Are
for recent climate change
humans the cause?
 Potential
change
ecological effects of climate
Outline
 Evidence
 Are
for recent climate change
humans the cause?
 Potential
effects of climate change
Evidence of Temperature Changes
 Three
main sources of data:
– Direct measurements of temperature
– Location of ice caps and tropical glaciers
– Thickness of ice caps
Temperature records

We have accurate
records only for the
past 120 years

Most temperature
readings taken at
cities which are
“heat islands”
Whaling and Polar Ice caps
Changes in extent of sea ice
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
Tropical Glaciers are melting
Kilimanjaro

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
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
Albedo = brightness
Ice caps have high albedo
Outline
 Evidence
 Are
for recent climate change
humans the cause?
 Potential
effects of climate change
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
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
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
Greenhouse effect

Light energy enters the
atmosphere

Changes to heat energy

Light energy exits
atmosphere but heat
energy is trapped
The Greenhouse effect

The greenhouse
effect is not all bad

Without the
greenhouse effect,
the earth would be,
on average, -18 C
Creation of greenhouse gases

The burning of fossil
fuels is increasing the
greenhouse effect

Important greenhouse
gases:
–
–
–
–
HCF’s, CFC’s
Methane
CO2
Water vapour
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
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
Carbon cycle

In the natural carbon
cycle, respiration and
decomposition increase
CO2

Photosynthesis
decreases CO2

Burning fossil fuels now
contributes to CO2 gain
Fossil fuels
Fossil fuels are ancient organisms that
did not decompose
The major culprits…
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
Outline
 Evidence
 Are
for recent climate change
humans the cause?
 Potential
effects of climate change
Potential effects of CO2 increase
 Predicted
changes in temperature
 Changes
to the natural world
 Changes
to human life
Recent increases in CO2

Jagged line is
caused by seasonal
changes in
photosynthesis; in
summer N.
Hemisphere plants
use up more CO2
Pollution can mitigate increases in
temperature

Pollutants such as
those from car
exhaust are causing
increases in cloud
cover

Cloud cover
increases albedo
Air pollution increases albedo
CO2 and temperature changes

Simulations of
temperature
changes are
becoming
increasingly
accurate
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
Increased photosynthesis
Planting trees to decrease temp

Deforestation
causes decreases in
CO2 absorption

Planting trees will
have the opposite
effect ->decreases
CO2
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
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.
Temperature and precipitation
Climate affects ecology
Deserts will spread
N. Hemi. plants will migrate north
Predicted migration of beech and maple trees
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
Cold-adapted species
Implications to Conservation
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
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
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
Summary
 The
Earth is becoming increasingly
warm
 Recently,
humans have contributed to
this phenomenon
 Temperature
increases will have severe
effects to the natural world