Transcript Science of climate change

The Science of Climate Change
Why We Believe It and What Might Happen
Dave Stainforth,
University of Exeter
Tyndall Centre for Climate Change Research
London School of Economics
Environmental Change Institute, Oxford University.
Climate Change – The Basics
Atmospheric Greenhouse Gas Levels are
Increasing
Source: IPCC Fourth Assessment Report (SPM)
Climate Change – The Basics
Scenarios of Future Human Activity
Note different scale! Source: IPCC Third Assessment Report
In 2005 CO2 concentrations were about 380ppm but greenhouse gas
concentrations were about 430 ppme (ppm equivalent)
Climate Change – The Basics
Global Temperatures and Sea Levels are Rising
Source: IPCC Fourth Assessment Report (SPM)
Climate Change - Fundamentals
Commitment to Further Warming
 We are committed to further warming based on
past emissions alone.
Around 0.5°C - 1°C according to Wigley 2005
and Meehl, 2005.
Climate Change: Global Projections
By 2020s we can
expect global
temperatures to be
between 0.3°C and
1.3°C warmer than
the 1990s.
(Stott and Kettleborough,
2002)
Figure SPM.5
Source: IPCC Fourth Assessment Report (SPM)
"We need to treat climate change not as a long
term threat to our environment, but as an
immediate threat to our security and prosperity,"
John Ashton,
UK Climate Ambassador at the Foreign Office
2006
Terminology – Mitigation and Adaptation
 Mitigation: “A human intervention to reduce the
sources or enhance the sinks of greenhouse
gases.”
 Adaptation: “Adjustment in natural or human
systems in response to actual or expected
climatic stimuli or their effects, which moderates
harm or exploit beneficial opportunities”
Terminology – Mitigation and Adaptation
Mitigation
Adaptation
What is Climate Science?
Maths: non-linear systems, chaos, game theory…
Judd.pdf
What is Climate Science?
Physics: atmosphere, oceans, clouds …
cp
Du p


 2Ω x u  g   2u
Dt


Momentum equation
D
    u
Dt
Conservation of mass
DT 1 Dp

Q
Dt  Dt
Conservation of energy
p   RT
Ideal gas law (equation of state of an
“ideal” gas)
What is Climate Science?
 Maths, physics, statistics, hydrology, geomorphology,
ecology, agricultural science, economics, political
science, international development …
 Climate change science is a new science.
 Climate change science is a mixture of many different
disciplines; getting them to work together is itself a
challenge.
Climate Change: Why we believe it’s a
significant global problem
 Basic physics:
 Atmospheric GHGs increase
surface temperatures.
(The earth would be 30oC colder if
they didn’t.)
 GHGs should increase surface
temperatures.
(Just based on their basic
radiative properties.)
 Observations:
 Global mean temperatures are
increasing.
Some Sceptic Arguments:
news.bbc.co.uk/2/hi/science/nature/7081026.stm
1.
2.
3.
4.
5.
6.
7.
Evidence that the earth's temperature is getting warmer is unclear.
If the average temperature was rising, it has now stopped.
The earth has been warmer in the recent past.
Computer models are not reliable.
The atmosphere is not behaving as models would predict.
Climate is mainly influenced by the sun.
A carbon dioxide rise has always come after a temperature
increase not before.
8. Long-term data on hurricanes and arctic ice is too poor to assess
trends.
9. Water vapour is the major greenhouse gas; co2 is relatively
unimportant.
10. Problems such as hiv/aids and poverty are more pressing than
climate change.
Some Sceptic Arguments:
news.bbc.co.uk/2/hi/science/nature/7081026.stm
1.
2.
3.
4.
5.
6.
7.
Evidence that the earth's temperature is getting warmer is unclear.
If the average temperature was rising, it has now stopped.
The earth has been warmer in the recent past.
Computer models are not reliable.
The atmosphere is not behaving as models would predict.
Climate is mainly influenced by the sun.
A carbon dioxide rise has always come after a temperature
increase not before.
8. Long-term data on hurricanes and arctic ice is too poor to assess
trends.
9. Water vapour is the major greenhouse gas; co2 is relatively
unimportant.
10. Problems such as hiv/aids and poverty are more pressing than
climate change.
Feedbacks


Feedbacks: water vapour,
clouds, land surface, ice
sheets, methane hydrates
…
The sceptic view: Negative
feedbacks in the climate
system will counteract any
potential warming due to
increased atmospheric
GHGs.
(e.g. Richard Lindzen’s Iris
effect)
What happens next.
Figure SPM.5
UK Climate Impacts Programme Scenarios
“The UKCIPnext climate change scenarios
will be presented … as probability
distributions.” They will be available for
25km grid boxes.“Model outputs will
include changes in temperature,
precipitation, snowfall, wind speed,
humidity, cloud cover, solar radiation, air
pressure and soil moisture content.”
Source : UKCIPnext Consultation
Climateprediction.net, distributions and ranges
Mediterranean Basin
Northern Europe
Winter
Winter
Summer
Summer
Annual
Annual
Exploring Possibilities
Going Forward
 We all need to start debating how to respond to
climate change – not whether it is happening.
 To get the best out of the science, industry and
academia need to work together.
Climate change is happening, but is it man-made?
The Royal Society has a website which answers this.