20130615 - Horton

The climate science behind
the numbers in the news
Clare Bryden
15 June 2013
400 ppm
Source: http://www.esrl.noaa.gov/gmd/ccgg/trends/mlo.html
Carbon dioxide concentrations
Business as usual
700 ppm in 2100?
350 ppm
400 ppm in 2013
ource: http://www.carbonvisuals.com/blog/400-ppm
CO2 emissions since 1850 (red)
Exponential growth (blue)
Source: http://www.guardian.co.uk/environment/2013/apr/17/why-cant-we-give-up-fossil-fuels
Carbon dioxide emissions from fossil fuel combustion
million tonnes carbon dioxide
International aviation bunkers
International marine bunkers
Middle East
Non-OECD Americas
Non-OECD Europe and Eurasia
OECD Europe
OECD Asia Oceania
OECD Americas
1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010
1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009
Source: International Energy Agency 2012
Climate science
Taking observations
 Concentrations
Understanding earth
 Temperatures &
other climate
 Human and other
 Feedback loops
Future projections
Attribution of events to
climate change
Impact of mitigation
Need for adaptation
1961-90 average
Climate models
have improved
over time
Natural influences are not enough to explain
changes in temperature
Earth’s orbital
too slow
Solar heating
too small
cool climate
Including both human and natural influence
that climate change is happening
“Very likely”
that it is caused by human activity
i.e. more than 90% probability
or at least 9 to 1 on
IPCC Fourth Assessment Report, 2007
Arctic Sea Ice
Source: Met Office presentation to COP18, Doha
Age of Arctic sea
ice at the end of
the melt season
European summer temperatures
Source: Met Office
Every year climate change leaves
over 300,000 people dead,
325 million people seriously affected,
and economic losses of US$125 billion.
2.8 billion people are vulnerable to the
physical effects, and 4 billion people if
socio-economic effects are included.
500 million people are at extreme risk.
Source: http://www.ghf-ge.org/human-impact-report.pdf
80% by
Two facts on climate science and politics
For all the uncertainty about the detail, every
science academy in the world accepts the
mainstream view of man-made global warming.
Virtually every government has agreed the world
must limit the global temperature increase to 2°C –
a level which isn't by any means "safe" but may be
enough to avoid the worst impacts.
Source: http://www.skepticalscience.com/97-percent-consensus-cook-et-al-2013.html
One of the most disturbing things about listening to
scientists studying climate change, then, is the fear in
the voices and words of people not accustomed to be
fearful, and the sense that generally speaking, scientists
are far more worried than most of us are.
We can either believe they are worried because they
are foolish, easily frightened and scaremongering, or we
can believe they are afraid because they are seeing
things they have never seen before with implications
that are terrifying, and do not understand why the rest of
us are so unafraid.
Sharon Astyk, 2007
The media largely consists of humanities graduates. They may
be able to argue the toss about Rousseau or Goethe, but they
almost glory in ignorance over the most basic principles of
scientific research. Also, many of them suspect that “It’s just a
bunch of people in lab coats who never agree anyway.”
What’s the point of scrupulous research? The specialist
correspondent is sidelined in favour of a simplistic ‘big story’. It
matters not whether the truth may be more complex, there are
papers to be sold.
Ben Goldacre, Bad Science column
UK Climate Change Act 2008
Cut in emissions of 60% by 2050
Stabilisation at 550 ppm
But very likely that 2ºC exceeded
Cut in emissions of 80% by 2050
Stabilisation at 450 ppm
Cuts required for a 50% chance
of not exceeding 2°C
Each 10-year delay adds 0.5ºC to
the most likely temperature rise
Source: Met Office presentation to COP18, Doha
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