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TUC, 21st October 2013
Climate change – the scientific evidence and its implications
Why climate change matters to us all
Julia Slingo, Met Office Chief Scientist
TUC Green Growth conference 21 October 2013
Atmospheric Concentrations of
Carbon Dioxide:
Crossing 400ppmv for the first time
Why 400ppmv is a big deal
400
Ice Core Records of Past Climate
Change
280
© Crown copyright Met Office
IPCC 4th and 5th Assessment Reports:
Warming is unequivocal
‘Pauses’ in warming are expected and understood
Changes across the
climate system are
consistent with a
warming world
Inter-Governmental Panel on Climate Change (2013)
Extremely likely (95100%) that most of
observed increase in
global surface
temperature since 1951
caused by human
influence (IPCC 2013).
Assertion that we survived
the Medieval Warm Period
and Little Ice Age ignores
the rapid increases in the
world’s population and in the
sophistication of our current
civilisation.
Global Interdependencies:
Circle of Securities
• Changing Exposure
Water
– where we live
Health
Climate
Variability and
Change
• Changing Vulnerability
– how we live
• Changing Climate
Economic
Urbanisation
Population
growth
Political
Food
Energy
Increasing confidence that human emissions
are increasing the risk of some types of
extreme events
• Report by UK and US scientists looking at extreme events in 2012
• Half of the extreme events studied displayed some evidence that human
induced climate change was a contributing factor.
USA heatwave, spring 2012
Australian rainfall, summer 2012
Iberian drought, winter 2011/12
New Zealand rainfall, winter 2011
Arctic sea ice minimum, autumn 2012
Inundation from Hurricane Sandy, autumn
2012
Projections of future global warming
• Global warming >2˚C is likely for scenarios with little mitigation of
emissions. No mitigation leads to a world more than 4˚C warmer
than pre-industrial times
Inter-Governmental Panel on Climate Change (2013)
Projections of future sea level rise
Long Term Commitment to Climate Change
• Global average sea level will rise during the 21st century; it is very
likely that it will rise faster than it has during the last 40 years.
Inter-Governmental Panel on Climate Change (2013)
‘Moving to
the right’
National Risk
Register
A number of key
national risks can be
expected to increase
in likelihood and
impact as a result of
climate change
Total CO2 emissions are strongly
linked to total warming
If warming is to be limited to 2˚C, total CO2 emissions need to be
limited to ~1000 Gigatonnes of Carbon (‘Trillionth Tonne’).
In conclusion...
• Climate change is unequivocal. It is extremely likely that
human influences have been the dominant cause of the
observed warming since 1951.
• There is already evidence that climate change is leading to
more extreme weather events that affect a world that is
increasingly exposed, vulnerable and interdependent
• Current trajectories of carbon emissions take us towards a
world 4˚C warmer than the present by the end of the
century
• If warming due to human emissions is to be limited to 2˚C,
total emissions need to be limited to 1000 Gigatonnes of
Carbon. About half of this has already been emitted.