Transcript Slides - Agenda INFN

Climate Change:
detection, attribution and projections
Alessio Bellucci
Centro Euro-Mediterraneo sui Cambiamenti Climatici
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:
http://www.ipcc.ch
The observations
(Phenomenology of Climate Change)
The main indicator:
Global Mean Surface T (GMST)
The main indicator:
Global Mean Surface T (GMST)
1901 – 2012: Observed change in surface
temperature
Warming of the climate system is unequivocal
Snow cover (declining)
(declining)
Arctic sea-ice
Oceans
(warming)
Sea level
(rising)
 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.
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
The atmospheric concentrations of CO2, methane and nitrous
oxide have increased to levels unprecedented in at least the
last 800,000 years.
Impact of climate change
on extreme events
Impact of climate change
on extreme events
Understanding
the causes
(Beyond detection)
Climate Models
Climate models are a very powerful tool to
understand the causes behind
climate change
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)
The observed warming 1951−2010 is
approximately 0.6°C to 0.7°C.
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
The observed warming 1951−2010 is
approximately 0.6°C to 0.7°C.
Human influence on the climate system
is clear.
The future
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
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.
Uncertainty in projected
climate change
Even only 1oC increase
will be a serious change
?
?
Global mean sea level will continue to rise during
the 21st century and virtually certain beyond 2100
RCP2.6 (2081-2100): likely range: 26 to 55 cm
RCP8.5 (2081-2100): likely range: 45 to 82 cm
2100: surface temperature
(2 scenarios)
1 – 1,5 oC Increase
4 – 7 oC Increase
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
2100: moving towards
a warmer and drier climate
10% Decrease
1 – 1,5 oC Increase
10-20% Decrease
4 – 7 oC Increase
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 2011.
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.
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.
THANK YOU
Additional Slides
2100: mean precipitation
(2 scenarios)
10% Decrease
10-20% Decrease
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.
 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 socioeconomic,
3. Possible response options.
 IPCC had published 5 assessment reports and various other
reports.
IPCC Reports:
The four Elements of the
Fifth WGI Assessment Report
1. 14 Chapters
2. Atlas: Regional Projections
o ca. 2000 Pages,
o 1250 Figures und Diagrams,
o
Timeseries und Maps for 35
Regions of the World,
o
2 Milion Gbytes.
3. Summary for Policymakers
o 22 Pages, 10 Figures
4. Technical Summary
o
ca. 90 Pages
Observed climate trends over
Europe: surface temperature
Recent 1981-2012 trends in annual mean temperature
exceed the global mean land trend [IPCC AR5 Chapter 14]
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.
Uncertainties in projections
 Internal variability – an important source of
climate variability
• Future climate change is a sum of:
o an externally forced response, due to changes in
radiative forcing arising from human activity,
variations in the sun and major volcanic eruptions
o Internal variability, e.g. the El Niño-Southern
Oscillation (ENSO) and other patterns, and year-toyear and decade-to-decade fluctuations in winds,
precipitation, temperature, …
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