1. Why historical climate and weather observations matter.
Philip Brohan
ACRE Exeter meeting 15th September 2009
© Crown copyright 2009

2. Observed surface temperature
© Crown copyright 2007

3. 2ºC above pre-industrial
Scenario independent
2ºC above pre-industrial
Figure SPM.5. Solid lines are multi-model global averages of surface warming (relative to 1980–1999) for the scenarios A2, A1B and B1, shown as continuations of the 20th century simulations. Shading denotes the ±1 standard deviation range of individual model annual averages. The orange line is for the experiment where concentrations were held constant at year 2000 values. The grey bars at right indicate the best estimate (solid line within each bar) and the likely range assessed for the six SRES marker scenarios. The assessment of the best estimate and likely ranges in the grey bars includes the AOGCMs in the left part of the figure, as well as results from a hierarchy of independent models and observational constraints. {Figures 10.4 and 10.29}
© Crown copyright 2007

4. Global and local impacts
Mitigaton
Adaptation
Global impacts
years & beyond
Local impacts
10-40 years
Simple climate models
Regional climate models
Global climate models
© Crown copyright 2007

5. Observed climate at the moment.
© Crown copyright Met Office
© Crown copyright 2007

6. Observed climate after ACRE
© Crown copyright Met Office
© Crown copyright 2007

7. The big questions Evidence base: What climate change has occurred?
What caused it?
Impacts
Drought, floods, storms, ecosystem changes.
Adaptation
What changes are now inevitable?
Mitigation
What present actions will constrain future change?
© Crown copyright 2007

8. Europe significant input to IPCC
“Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic GHG concentrations.”
IPCC 2007
© Crown copyright 2007

9. European Summer Temperatures
Observed temperatures
Simulated temperatures
2060s
2040s
2003
Observed Summer temperatures over land for Europe from CRUTEM3 (Western Europe west of 20E)
Model Simulations, HadGEM1. 3 Ensembles of Anthropogenic+natural forced simulations. From ensembles forced with A2 and A1B scenario.
Summer 2003:
normal by 2040s, cool by 2060s
Stott Nature 2004 – updated to 2007 – HadGEM1
© Crown copyright 2007

10. © Crown copyright 2007

11. The last 1000 years
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12. With C19 constraint – low variability
© Crown copyright 2007

13. With C19 constraint – High variability
© Crown copyright 2007

14. Leveraging ACRE to the past and the future
If we knew which models were accurate we could predict the future precisely.
If we knew the climate in the last 1000 years we would know which models were accurate.
If we knew the climate of the past 200 years we would know the climate of the last 1000 years.
Historical weather observations constrain the past and the future
© Crown copyright 2007