1.
Climate change and uncertainty: consequences for policy making on adaptive responses
Helge Drange

2. Some observations
Temperature
Precipitation
Sea level

4. 2008

5. 2009

6. 2010

7. 2011

8. 1911

9. Distribution of observed summer temperature 1960-2011
(1σ ~ 1/3; 2σ ~ 1/20; 3σ ~ 1/400; 4σ ~ 1/16000)
1/400
1/16.000
Hansen et al. (2012)

10. Relative humidity in air (%) (Clausius-Clapeyrons
Precipitation: Air's water vapour holding capacity increases with increasing temperature 90 80 70 60 50 40 20 10
Relative humidity in air (%)
Temperature (°C)
5-7 % increase
pr °C increase
(Clausius-Clapeyrons
expression)
Regions with high humidity get wetter  Incr´d precip
Regions with low humidity get incr problems forming clouds  Reduced precip
There is huge uncertainty in global precipitation projections, relating both to climate sensitivity and mitigation pathways. 10

11. Observed mean change in precipitation, 1951-2010
Winter (mm/decade)
Wetter
Dryer
van den Besselaar et al (2012)

12. Observed mean change in precipitation, 1951-2010 Summer (mm/decade)
Dryer summers
(but incr’d extreme precip)
van den Besselaar et al (2012)

13. Global sea level from tide gauges and satellite
( )
Present increase of
~3 mm pr year
Change in sea level (cm)
Church & White (2006) + AVISO

14. Earth´s climate is changing.
Summary:
Earth´s climate is changing.
Mainly caused by
human emissions of
greenhouse gasses.

15. uncertainty ≠ no certainty
What we are
heading at
uncertainty ≠ no certainty

16. Change in global temperature, 15 models
(relative to )

17. Change in global temperature, 15 models
(relative to )
+2 °C
For a global, mean warming of ~2 degrees C, which we may experience around 2050,
Earth's climate will be comparable to the climate ~3.2 mill years ago
Global emission top in 2040, 650 ppm CO2-eq in 2100

18. On local scale
Much harder to do local than continental/global climate projections
Random fluctuations in climate is particularly important on local scale and is, unfortunately, essentially unpredictable [May therefore experience periods without (apparent) climate change]
Fine-scale climate projections can be made, but added value beyond the visible aspect (“looking nice”) can and should be questioned
Harder to make projections of precipitation than temperature; very hard to make projections about local changes in extremes

24. Western Norway, 14 September 2005

26. 14 Sep 2005

27. Changes in observation-based precipitation intensity vs global warming
+100
Intensity category (bins of 10%)
Shiu et al (2012)

28. Changes in observation-based precipitation intensity vs global warming
+100
0 to -20
Intensity category (bins of 10%)
Shiu et al (2012)

29. Changes in modelled precipitation intensity vs global warming +10
Intensity category (bins of 10%)
Shiu et al (2012)

30. Uncertainty in global and regional temperature projections
Hawkins and Sutton (2009)
Global scale
Internal unc
Emsission uncertainty
Model uncertainty

31. Uncertainty in global and regional temperature projections
Hawkins and Sutton (2009)
Global scale
Great Britain
Internal unc
Emsission uncertainty
Model uncertainty

32. Uncertainty in global and regional temperature projections
Hawkins and Sutton (2009)
Global scale
Great Britain
Internal unc
Far future: Uncertainty from emissions & models
Emsission uncertainty
Model uncertainty
Near future: Random variations very important

33. Total: Warming of the ocean Glaciers melting Greenland and Antarctica
May contribute 20 cm in this century
Total:
cm in 2100
+1 (?) m in 2200
Glaciers melting
May contribute cm in this century
Greenland and Antarctica
May contribute cm in this century (large uncertainties)

34. Relative sea level rise caused by melting of land ice
Factor
Riva et al. (2010)

35. Summary – We are approaching a climate never experienced by modern man
– It is misleading to provide and use one number for a future change in one climate variable
– It can be very misleading to use input from one model run to characterise future climate
– Ideally, several models, scenarios and approaches should be used to get best estimate and likely range of changes in future climate
– Continuous communication and interaction between climate scientists and “end-users” are highly recommended, and possibly the single most important aspect regarding the handling of uncertainty

36. Observed wind

37. Observed wind speed trend, 1979-2008
(m/s per decade)
Vautard et al. (2010)

38. Observed storm activity over the British Isles, North Sea and Nordic Sea
Long-term decline, large variability, very hard (impossible) to predict variations on time scales shorter than ~30 years
KNMI, suppl. (2009) and IPCC (2007)