1. Arctic climate Valérie Masson-Delmotte
LSCE (CEA-CNRS-UVSQ/IPSL), Gif-sur-Yvette, France
Helge Drange
Univ. of Bergen and the Bjerknes Centre, Norway
V Possible title page. Drawing from In Northern Mists by Fridtjof Nansen (1911)
In Northern Mists, by Fridtjof Nansen (1911)

2. Observed temperature
( )
and Arctic sea ice
( ) V

3. Temperature animation here
H Animation of GISS annual mean surface temperature for relative to (3 yr averages)

4. H Mean temperature anomaly for the decade 1905-1914.

5. Polar amplification
H Mean temperature anomaly for the last decade ( ): Polar amplification

6. Extent of Arctic sea ice, September Reduced with more than ⅓ since 1978, halved since the 1950s
Satellite
Reconstructed
Extent (106 km2)
H The standard figure … Sep sea ice extent in the Arctic: 36% reduction over the time span of satellite obs
and

7. Extent of Arctic sea ice, September Reduced with more than ⅓ since 1978, halved since the 1950s
Satellite
Reconstructed
Extent (106 km2)
H …Increasing to about 50 % reduction if reconstructed sea ice is included
and

8. Mean ice cover, September 2012
H How things looked like in Sep 2012

9. Modelled change in Arctic surface temperature
( )
Global temperature: +0.6 °C −
V “Another view of the polar amplification…”. Surface temperature change between 1979 – 2012 from renalaysis; highlighting the polar amplification
Bader (2014), Ding et al. (2014)

10. Central questions: How unusual? Naturally occurring variations?
Degree of human influence?
What about the future? − V
Bader (2014), Ding et al. (2014)

11. From a paleoclimatologist’s
point of view… V

12. (i) How unusual are these recent changes?
Toolbox: proxy records from natural archives V

13. (ii) How unusual are these recent changes?
Temperature change (°C)
Year V
Arctic warming, and sea ice retreat unprecedented in more than 1400 years
Similar conclusions for sea level rise and global warming
PAGES2k, 2013

14. (iii) How unusual are these recent changes?
1800 ppb
400 ppm
Atmospheric composition V
EPICA and Vostok ice core data

15. (iv) How unusual are these recent changes?
Past sustained polar warming over thousands of years has led to deglaciation of ice sheets and sea level rise by several meters
Threshold for Greenland ice sheet deglaciation between 1 and 4°C global warming above pre-industrial level V
IPCC AR5, Climatechange2013.org

16. From a climate modellers' point of view…H

17. Conservation water vapour motion and growth/melting sea ice
+ Human-made greenhouse gases and aerosol particles
Equation
of motion
Conservation water vapour
Conservation heat
Radiation/clouds/
Particles/etc.
Atmosphere
Surface friction
Exchange
of heat
of water
Water budget
Snow and ice
budget
Heat
Land
Runoff
H Schematic of a climate model
Conservation
of salt
Equations for
motion and growth/melting sea ice
Conservation of heat
Equation
of motion
Ocean & sea ice
After Manabe & Stouffer (2000)

18. Conservation water vapour motion and growth/melting sea ice
Equation
of motion
Conservation water vapour
Conservation heat
Radiation/clouds/
Particles/etc.
Atmosphere
Surface friction
Exchange
of heat
of water
Water budget
Snow and ice
budget
Heat
Land
Runoff
H Schematic of a climate model, highlighting the interaction between atm and the ocean
Conservation
of salt
Equations for
motion and growth/melting sea ice
Conservation of heat
Equation
of motion
Ocean & sea ice
After Manabe & Stouffer (2000)

19. uncertainty ≠ no certainty
Possible future
uncertainty ≠ no certainty H

20. Global population (billion) Global CO2-emissions (Gt-C/yr)
2006
Global population (billion)
Global CO2-emissions (Gt-C/yr)
V. Blue colour: Global population (actual until 2014, estimated thereafter).
Black line: Total CO2-emissions to atmosphere (human+natural) up to 2006, the starting point for the AR5-scenarios

21. Global population (billion) Global CO2-emissions (Gt-C/yr)
2006
Global population (billion)
Global CO2-emissions (Gt-C/yr)
V. Business-as-usual scenario (high-end scenario; almost tripling of global co2-emissions)

22. Global population (billion) Global CO2-emissions (Gt-C/yr)
2006
Global population (billion)
Global CO2-emissions (Gt-C/yr)
V. Two intermediate scenarios, one with max emissions in 2080, another with max emissions in 2040

23. Global population (billion) Global CO2-emissions (Gt-C/yr)
RCP8.5
RCP6.0
RCP4.5
RCP2.6
2006
Global population (billion)
Global CO2-emissions (Gt-C/yr)
V. A scenario constructed to be consistent with 2C warming (note possibility for negative emissions towards 2100)

24. Global population (billion) Global CO2-emissions (Gt-C/yr)
RCP8.5
RCP6.0
RCP4.5
RCP2.6
2006
2014
Global population (billion)
Global CO2-emissions (Gt-C/yr)
V. What about the actual co2-emissions between 2006 and 2014?

25. Global population (billion) Global CO2-emissions (Gt-C/yr)
RCP8.5
RCP6.0
RCP4.5
RCP2.6
2006
2014
Global population (billion)
Global CO2-emissions (Gt-C/yr)
V. …they have been increasing, closely following RCP8.5.
In the following, results from RCP8.5 and RCP2.6 will be shown

26. Modelled change in annual mean temperature, Arctic
( relative to )
RCP8.5
RCP2.6
+9 to +11 °C
+2 to +3 °C
Arctic amplification occurred during the past and is expected in the future
Climate models are tested against past climate data
Global warming by more than 2°C would be outside of the range of variations of the past million years
For comparison, modern woman and man has been on Earth for some years H

27. Modelled change in annual mean precipitation, Arctic
( relative to )
RCP8.5
RCP2.6
~ 50 %
~ 10 % H

28. Modelled change in heavy (>97,5 %) precipitation
( relative to )
RCP8.5
RCP2.6
> 50 %
30-50 %
Approaching unknown territory for ecosystems and societies H

29. Arctic sea ice in September, 1900-2100 Observed 1953-2014 | Model simulations 1900-2100
Extent (106 km2)
Large differences between the scenarios (solid lines)
Large model uncertainty (shadings)
H (or V)
Virtually no sea ice
Stroeve et al. (2012), updated

30. NB: Poorly modelled sea ice thickness (Sep)
Observed
(ICESat)
Defference
Models – Obs
Multi-model mean
H (or V)
Stroeve, NSIDC

31. Future sea level change
For the next decades, dominant role of ocean warming and glacier retreat
For the long term, key uncertainty
associated with the response of the Greenland and Antarctic ice sheet
Large warming would lead to up to 1 m sea level rise in 2100, 3 m by 2300 V

32. Concluding remarks
For the Arctic, amplifying mechanisms acting at the regional scale but also at the global scale
Arctic climate change leads to a complex mixture of opportunities and vulnerabilities
Risks of irreversible loss: biodiversity, cultural heritages
Thawing of the vast permafrost regions in the Arctic is ongoing, with poorly known climate implications
Based on current understanding, rapidly reduced greenhouse gas emissions will strongly limit climate changes in the Arctic V