1. detection, attribution and projections
Climate Change:
detection, attribution and projections
Alessio Bellucci
Centro Euro-Mediterraneo sui Cambiamenti Climatici

2. IPCC WG1 AR5 Climate Change 2013: The Physical Science Basis
The IPCC has released its WG1 AR5 Climate Change 2013: The Physical Science Basis on 27 Sept 2013 in Stockholm, Sweden.
The Summary for Policymakers (SPM) can be downloaded from the IPCC website:

3. The observations (Phenomenology of Climate Change)

4. The main indicator: Global Mean Surface T (GMST)

5. The main indicator: Global Mean Surface T (GMST)

6. 1901 – 2012: Observed change in surface temperature

7. Warming of the climate system is unequivocal
Snow cover (declining)
Since the 1950s, many of the observed changes are unprecedented over decades to millennia.
The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.
(declining)
Arctic sea-ice
Oceans
(warming)
Sea level
(rising)

8. GHG Concentrations: 800,000 years BP-present
The atmospheric concentrations of CO2, methane and nitrous
oxide have increased to levels unprecedented in the last
800,000 years.
N2O
380
CO2
CH4
GHG Concentrations: 800,000 years BP-present

9. The atmospheric concentrations of CO2, methane and nitrous
oxide have increased to levels unprecedented in at least the
last 800,000 years.

11. Impact of climate change on extreme events

12. Impact of climate change on extreme events

13. Understanding the causes (Beyond detection)

14. Climate Models
Climate models are a very powerful tool to understand the causes behind
climate change

15. Climate Change Attribution Observations Models (Anthropogenic
+Natural forcing)
The consistency between
models and observations
is obtained only after both
anthropogenic
(GHG+Aerosols) and
natural (volcanoes, solar
irradiance) forcings are
considered
Observations
Models
(Only natural
forcing included)

16. The observed warming 1951−2010 is approximately 0.6°C to 0.7°C.

17. The observed warming 1951−2010 is approximately 0.6°C to 0.7°C.
It is extremely likely that human influence has been the dominant cause of observed warming since the mid-20th century

18. Human influence on the climate system is clear.
The observed warming 1951−2010 is approximately 0.6°C to 0.7°C.
Human influence on the climate system is clear.

19. The future

20. Future Climate Projections
For future climate projections, climate models requires Emission Scenarios. Models in AR5 use Representative Concentration Pathway (RCP)
very high GHG
emissions
stabilization
mitigation (peak and decline)
RCPs represent a range of 21st Century climate policy scenarios

21. Projected Global Average Temperature Change by end of 21st Century
The temperature increase during the last 100 years was only about 0.8oC.
Global surface temperature change for the end of the 21st century is likely to exceed 1.5°C relative to
1850−1900 for all scenarios except RCP2.6.

22. Uncertainty in projected climate change
Even only 1oC increase will be a serious change ? ?

23. Global mean sea level will continue to rise during the 21st century and virtually certain beyond 2100
RCP2.6 ( ): likely range: 26 to 55 cm
RCP8.5 ( ): likely range: 45 to 82 cm

24. 2100: surface temperature (2 scenarios)
1 – 1,5 oC Increase
4 – 7 oC Increase

25. Expected changes for precipitations over Europe (2080-2100 vs 1986-2005)
SUMMER (JJA)
drier climate
in summer
over the Med
region
WINTER (DJF)
Small changes are expected over the Central and Northern Europe but
a notable reduction (dry conditions) over the Mediterranean region

26. 2100: moving towards a warmer and drier climate
10% Decrease
10-20% Decrease
1 – 1,5 oC Increase
4 – 7 oC Increase

27. MITIGATION: Limiting climate change will require substantial and sustained reductions of GHG emissions
RCP2.6 would be the Emission Scenario to follow if we were to cap warming at 2oC
To limit warming to likely less than 2oC as in RCP2.6, requires total emissions since preindustrial to be limited to less than about 790 PgC.
515 PgC were emitted by

28. Summarizing…. Climate Change is unequivocal.
Even if policies and efforts to reduce emissions prove effective, some climate change is inevitable.
Therefore, strategies and actions to adapt to its impacts are needed.

29. Summarizing…. THANK YOU Climate Change is unequivocal.
Even if policies and efforts to reduce emissions prove effective, some climate change is inevitable.
Therefore, strategies and actions to adapt to its impacts are needed.
THANK YOU

30. Additional Slides

31. 2100: mean precipitation (2 scenarios)
10% Decrease
10-20% Decrease

32. Cumulative emissions of CO2 largely determine global mean surface warming by the late 21st century and beyond
Warming is largely independent of the emission profile. Only the total matters.
More emissions early imply stronger reductions later.
Every ton of CO2 causes about the same amount of warming, no matter when and where it is emitted
Any temperature target implies a maximum in cumulative CO2 emissions. This is purely a physical and carbon cycle problem.
Allocation over time is a economic and policy question.
Overshooting the budget will overshoot the target.

33. 1. Causes of climate change,
In 1988 IPCC was established under WMO and UNEP to provide independent, objective, fair and transparent assessment of the state of global climate system.
IPCC provides such assessment and is the source of information particularly to policy makers and UNFCCC on
1. Causes of climate change,
2. Potential impacts on built and natural systems and socio-economic,
3. Possible response options.
IPCC had published 5 assessment reports and various other reports.

34. IPCC Reports:

35. The four Elements of the Fifth WGI Assessment Report
14 Chapters
Atlas: Regional Projections
ca Pages,
1250 Figures und Diagrams,
Timeseries und Maps for 35
Regions of the World,
2 Milion Gbytes.
Summary for Policymakers
22 Pages, 10 Figures
4. Technical Summary
ca. 90 Pages

36. Observed climate trends over Europe: surface temperature
Recent trends in annual mean temperature
exceed the global mean land trend [IPCC AR5 Chapter 14]

37. The double challenge: CHALLENGE 1:
In order to stabilize GHGs concentrations in the atmosphere, emissions would need to peak and decline thereafter.
Mitigation efforts over the next decade will have a large impact on opportunities to achieve lower stabilization levels.
CHALLENGE 2:
Even if policies and efforts to reduce emissions prove effective, some climate change is inevitable; therefore, strategies and actions to adapt to its impacts are also needed.

38. Uncertainties in projections
Internal variability – an important source of climate variability
Future climate change is a sum of:
an externally forced response, due to changes in radiative forcing arising from human activity, variations in the sun and major volcanic eruptions
Internal variability, e.g. the El Niño-Southern Oscillation (ENSO) and other patterns, and year-to-year and decade-to-decade fluctuations in winds, precipitation, temperature, …

39. Impact of climate change on extreme events over Europe
Very likely increase of the number of warm days and nights and decrease of the number of cold days and nights, since 1950 in Europe.
Heat waves can be amplified by drier soil conditions resulting from warming
General increases in the intensity and frequency of extreme precipitation especially in winter