Transcript No Slide Title

Climate change – why bother
David Archer
Green Ovingham
Outline of slide show
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The scientific basis of climate change
Evidence from global observations
– The rise in temperature
– The rise in sea level
– The loss of Arctic sea ice
– Retreat of glaciers
– Droughts and floods
Local evidence of climate change
Global and local risks
A response to sceptics
The greenhouse effect
We live in a Goldilocks world: neither too hot, too cold but just right.
The normal greenhouse effect keeps it that way
(otherwise the worlds average temperature would be -18C)
Adding CO2 and other greenhouse gases pumps up the temperature
The scientific basis of climate change 1
Where better to start
than in our back garden
– in the greenhouse.
Glass in the greenhouse
allows incoming solar
radiation (light) to pass
through but holds back
the outgoing heat
radiation - so the inside
temperature gets
warmer.
Plants thriving in winter in the
greenhouse
The scientific basis of climate change 2
Carbon dioxide (CO2),
methane and several
other ‘greenhouse’ gases
work in the same way.
The main source of CO2
is the burning of fossil
fuels in heating, lighting
transport and industry.
The main source of
methane is the belching
of cows! But otherwise
also from fossil fuel
production and landfill.
The scientific basis of climate change 3
Carbon dioxide (CO2) in
the atmosphere has risen
from a pre-industrial
average of 280 parts per
million to 380 parts per
million
Methane (CH4) has more
than doubled since preindustrial age. It is 20
times more effective than
carbon dioxide as a
greenhouse gas but at a
much lower concentration
The scientific basis of climate change 4
How long have we known about the effects of CO2?
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The principle of the effect of CO2 on global climate was
first established by the Swedish scientist Arrhenius in
the 1890s.
• He calculated that doubling of CO2 in the atmosphere
would cause global temperature to rise by 5 to 6oC.
• Present computer models suggest rather less but also
include variations in the sun’s activity, absorption of CO2
by the oceans and loss of polar ice.
Evidence from global observations
The rise in air temperature 1
Global temperature has been rising steadily since 1960
The highest year for global temperature was 1998;
In spite of our cold winters 2010 was second highest globally
Evidence from global observations
The rise in air temperature 2
Global temperature
is now at its
highest for more
than 1000 years
This is the Mann
Hockey Stick graph
disputed
but still gives a
reasonable
general picture
Evidence from global observations
The rise in ocean surface temperature
Red shows an increase
Evidence from global observations
The rise in sea level
Sea level is rising
both as a result of
melting of glaciers
and with the water
expanding at a
higher temperature.
Satellites show
recent global
average sea-level
rise (3.4 mm/yr over
the past 15 years)to
be 80% above past
IPCC predictions
Sea level change during
1970-2010.
Evidence from global observations
The decline of Arctic Sea ice 1
The change in Arctic sea ice between
September 1979 and September 2005.
Melting of Arctic sea-ice has accelerated far beyond the expectations
of climate models; during 2007-2009 was about 40% less than
earlier predictions from IPCC climate models.
Evidence from global observations
The decline of Arctic Sea ice 2
Inuit struggling
to move their
boat through
broken ice floes
Arctic sea ice freeze is occurring 3.5 weeks later than it did in the
1960s while the break up is occurring 2.5 weeks earlier.
Changes threaten Arctic ecosystems including the polar bear and
livelihoods of Inuit.
Evidence from global observations
The melting of glaciers 1
The total melt area of the Greenland ice sheet increased by 30%
between 1979 and 2008 with the most extreme melt in 2007.
Evidence from global observations
The melting of glaciers 2
Glacier retreat in the Alps over more than a century. Retreat has
accelerated in the last 20 years
Evidence from global observations
The melting of glaciers 3
The glaciers on
Kilimanjaro have
almost gone
(These views in
1969)
With a few exceptions glaciers elsewhere are also retreating.
This includes the Alps, the Andes, the Rockies and most of the
Himalaya. (Glaciers in the central Himalaya are predominantly
retreating but not at the rate stated by IPCC)
Evidence from local observations 1
Annual temperature at Durham (1961-2005)
y = 0.0309x + 8.0889
R2 = 0.4791
9.5
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8.5
8
7.5
2003
2000
1997
1994
1991
1988
1985
1982
1979
1976
1973
1970
1967
1964
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1961
Mean annual temperature
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Steady upward rise of 0.3°C per decade (1.4°C in 45 years)
Evidence from local observations 2
Seasonal and annual temperature rise °C/decade
Durham
1961 - 2005
1982 - 2005
Annual
0.31
0.50
Dec-Feb
0.40
0.69
Mar-May
0.31
0.56
Jun-Aug
0.32
0.44
Sep-Nov
0.18
0.37
The biggest seasonal rise is in winter (in spite of this
year’s frost)
Do you remember the snow
of 1979 and the frost of 1982?
Much worse than 2010!
Pennine snow 1979
Frozen peat 1972
Tees at Broken Scar,
Darlington, Jan 1982
Risks - Some local implications of temperature rise
Not all local effects are negative!
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Decreasing frequency of snow
Evapotranspiration and drying soil in summer
Shifting storm tracks, more passing to the north?
Rainfall intensities increasing
Increase in flood risk
Upward altitudinal and latitudinal shift in climate zones
Agricultural operations – more frequent summer drought
Hill farming – animals remain outdoors for longer in winter
But serious changes in moorland ecology
Warmer summers – more tourism?
Global risks
Sea level rise
By 2100 more than 1 m
(possibly 2 m) rise is
expected.
160 million people worldwide
live less than 1 metre above
sea level.
Large parts of Bangladesh will
be affected.
Flat island states like the
Maldives and Tuvalu will
disappear.
Mass migration will affect us
all.
Risks - Floods and droughts
. Warmer air is more energetic and can hold more moisture. In many places
droughts and floods have become more extreme and more frequent.
Risks - climate change and flooding
There can be no doubt that climate
is changing and changing in a way
that will increase flood risk
Purnell, 2002
From the
Christian Aid
Magazine
Increasing flood risk is now
recognised as the most
important sectoral threat from
climate change in most parts of
the world
Fowler and Kilsby 2003
The autumn 2000 floods
are a ‘wake-up call’
to the impacts of climate change
John Prescott
Former Deputy Prime Minister
Response to Sceptics
There can be no denying the basic physics that increasing greenhouse gases cause
global warming.
We are likely to pay a heavy price
if we keep emitting them.
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Climate has always
changed and this is no
different!
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This is a half truth. Climate
has always changed but
we are now warmer than
at any time during the last
1000 years.
The recent increase in
temperature cannot be
explained by changes in
solar output - but solar
output has had severe past
effects on global climate
Can we believe the IPCC after the
so-called ‘scandals’?
Yes we can with very limited
exceptions. But climate campaigners
have to be very careful not to
exaggerate.
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Sustainability – the global dimension
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Local sustainability requires global sustainability – and
vice versa
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Most vulnerable to climate change are impoverished
populations in marginal environments
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Western lifestyle and demands influence Third World
actions (Our demands are fuelling Chinese and Indian
industrialisation and growth in greenhouse gases).
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Ethics and morality (as well as self interest) require
that we take action to reduce impacts on the most
vulnerable
The Limits to Growth
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The Earth is not infinite and cannot provide resources indefinitely
for growing consumption.
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Exponential growth of population, consumption, resource and
energy use, waste production is unsustainable.
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Unconstrained exponential growth is a cancer of the natural
environment
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New technologies extend but do not alter the tendency of the world
system to grow and collapse
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Anyone wishing to have a quiet life made a mistake being born in
the late twentieth century.
Is this
The End?