School of something
FACULTY OF OTHER
National climate scenarios
Suraje Dessai
Sustainability Research Institute and ESRC Centre for Climate Change
Economics and Policy, School of Earth and Environment, University of
Leeds, UK
Climate Change Impacts, Adaptation and Mitigation (CC-IAM) Research
Group, Faculty of Sciences, University of Lisbon, Portugal
Outline
• Rationale for climate scenario construction
• The UK experience of national climate scenarios
• Re-thinking national climate scenarios workshop
Scenario and climate
scenarios
1950s – usage in military strategy and planning
1970s – usage in the energy business (Royal Dutch/Shell;
Van der Heijden, 1997).
1980 – first climate scenario (Wigley et al. 1980)
Scenarios and climate
scenarios
1950s – usage in military strategy and planning
1970s – usage in the energy business (Royal Dutch/Shell;
Van der Heijden, 1997).
1980 – first climate scenario paper (Wigley et al. 1980)
1980s-90s – scientific papers and policy documents use and
develop climate scenarios
1990s – first national climate scenarios published (UK)
2001 – IPCC TAR WG1 devotes a chapter to the science of
climate scenario construction (Mearns et al., 2001)
2009 – first probabilistic climate change projections published
(UK)
Climate scenario definition
A plausible and often simplified representation of the
future climate, based on an internally consistent set of
climatological relationships that has been constructed
for explicit use in investigating the potential
consequences of anthropogenic climate change, often
serving as input to impact models. Climate projections
often serve as the raw material for constructing climate
scenarios, but climate scenarios usually require
additional information such as the observed current
climate. A climate change scenario is the difference
between a climate scenario and the current climate
(IPCC AR5 WG1)
Climate scenarios
• Types: synthetic (arbitrary), analogues (temporal and
spatial), model based (GCMs, RCMs, statistical, etc.) and
hybrids.
Climate
‘relocation’ of
European cities
CNRM ARPEGE-Climat model
Hadley Centre HadRM3H model
2080s under SRES A2 scenario
Hallegatte et al.(2007) Using
climate analogues for assessing
climate change economic
impacts in urban areas. Climatic
Change 82:47–60
National climate scenarios
• Climate scenarios are
negotiated amongst
various actors (Hulme
and Dessai, 2008)
• Multiple functions:
pedagogic, motivational
or practical
• Often endowed with
governmental authority
to inform decisionmaking
• Increasingly used to
inform adaptation
A chronology of UK climate
scenarios
Climate change act
UKCP09 projections 2009
COP-15 fails to agree a post 2012 regime
A chronology of UK climate
scenarios
CCIRG91
CCIRG96
UKCP09
UKCIP98
UKCIP02
UK climate scenarios
(Hulme and Dessai, 2008)
Chronology of estimates of summer
precipitation change (%) for the
southeast of England
UKCIP02
UKCP09 projections
• First projections designed to
treat uncertainties explicitly
(Murphy et al. 2009)
• More informative but also more
complex than previous
scenarios (Murphy et al. 2009)
• Designed to inform adaptation
decisions
• Cost £11 million
• User Interface
• Reviewed by Steering and User
group and 5 experts
From UKCIP02 to UKCP09
UKCP09: sampled uncertainties
UKCP09
UKCP09 uncertainties
• Modelling uncertainty – arising from incomplete
understanding of the climate system, and our inability to
model it perfectly (PPE: model parameters, the sulphur and
carbon cycles)
• Natural climate variability – arising from both internal and
external factors on the climate system
• Emissions uncertainty – arising from not knowing the
amount of future global greenhouse gas emissions
• Contributions to uncertainty from downscaling
UKCP09 map
Contributions to the
uncertainty in winter
precipitation changes for
2070-2099 relative to 19611990, at selected 25 km
grid squares.
Figure 4.4: 10, 50
and 90% probability
levels of changes to
the average daily
mean temperature
(ºC) of the winter
(upper) and summer
(lower) by the 2080s,
under Medium
emissions scenario.
Figure 4.10: Changes
in annual (top), winter
(middle) and summer
(bottom) mean
precipitation (%) at the
10, 50 and 90%
probability levels, for
the 2080s under the
Medium emissions
scenario.
The greatest difference between
UKCIP02 and UKCP09
Demand for climate scenarios
• Early mainstreaming into planning (e.g., water resources in
late 1990s) now more diverse
• Success of UKCIP (1997-)
• Research demand (e.g., ARCC programme, 2007-17)
• Climate Change Act (2008)
• Adaptation Reporting Power (2009): “The UKCP09 Projections are
likely to be a useful tool for some organisations in undertaking
assessments of their risks from climate change. They will allow
decision makers to consider a range of possible future climates, as
well as an estimate of the uncertainties surrounding those changes.”
(Defra, 2009, p. 8).
• Climate change risk assessment (2012)
Prevalence of UK national climate
scenarios in the academic literature
45
40
35
30
25
UKCIP98
UKCIP02
20
UKCP09
15
10
5
0
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
Number of peer-reviews papers that include a UK national
climate scenario in the topic (includes title, abstract and
keywords). Searched in Scopus (24 July 2014).
(Re)Thinking National Climate
Scenarios Workshop – Dec 2013
• Some research on the construction of UK climate scenarios
(Hulme & Dessai, 2008) and its use (Tang & Dessai, 2012)
but much remains unclear or undocumented
• An international comparison has never been done (to my
knowledge)
• Aims and objectives of the workshop:
• Reflect on the process of national climate scenario
construction
• Understand what lessons can be learnt about the social,
political and technical issues that shaped the construction of
national climate scenarios
• Think and discuss the next generation of national climate
scenarios
A chronology of selected
national climate scenarios
National climate projections in
Europe
Slide by Stefan Fronzek: adopted from Füssel (2014), in Capela et al. (eds.) Adapting to
an Uncertain Climate – Lessons from Practice
Some reflections
•
Tension: “Keep the methodology understandable” vs “Take full advantage of
new science and tools”
•
Separate development and delivery as far as possible (publishing
methodology/external review)
•
Plan strategically for product support and development (It’s a Climate Service)
•
Keep the rigour on uncertainties, but provide a more flexible set of storylines as
a front-line product
•
Tension: Balance user needs against what science can credibly provide
•
Keep things simple: unless additional complexity adds value
•
Fitness-for-purpose
•
•
“credibility”: are the scenarios plausible, authoritative and consistent?
•
“relevance”: do the scenarios fulfill the user needs?
•
“legitimacy”: are the scenarios constructed in a transparent way?
XXXX does not (yet) provide actionable climate information
Treatment of uncertainty
Variety of approaches: PPE, MME, statistical emulators,
scenarios
Relevant Dominant Uncertainty (RDU): is the source of
uncertainty or error that is the primary limit on the fidelity of
our probability forecasts
Communicating Immature Probability forecasts will carry less
risk to the credibility all science-based decision support when
the RDU is discussed and your Probability of a Big Surprise is
provided, explicitly. Why communicate an immature PDF at
all? (Lenny Smith)
Volunteer computing: almost limitless computer power
(weather@home)
Hierarchy of approaches needed, but connected
Use of scenarios/projections in
decision-making
Various UK examples of use: water resources planning,
Climate Change Risk Assessment (CCRA), energy, etc.
User: “we need national climate scenarios less than we think
we do”; vulnerability-led approach.
Normal range
Possible changes
outside of the
range considered
in the CCRA
Natural variability
Sea Level Rise
Increasing uncertainty
Climate change*
LE(p10)
8 mm
Lower
ME(p50) HE(p90)
43 mm
Central
H++ ~ 2m
Upper
Risk magnitude
Decrease
No change
Increase
Where Are We Headed?
Generic scenarios are inherently limited – shouldn’t expect too
much – modesty/humility
Focus more on process and insight rather than model and
predictions
National Centre for Climate Services – tailoring; where is the
boundary between public and private?
Early days for decadal predictions (experimental – need to be
skilful and reliable)
Define a climate science agenda that begins with national
vulnerabilities (narrative will help)
Are PDFs inherently dangerous?
Extras
Answers to the questions by
one participant
• What kind of uncertainty can or should be quantified?
• Identify what uncertainty becomes important at what scales
but
• Internal variability, structural, parameter, inadequacy,
predictability, implementation
• Does the representation of uncertainty in climate models
encounter unique epistemic/technical challenges?
• Not unique, potentially most important
• Epistemic – need to increase awareness that this is
unavoidable (does Gödel’s incompleteness theorem apply
here?)
• Technical – no, but just about the hugest out there
Answers to the questions by
one participant
• What are the limits to modelling uncertainty?
• Can’t do anything about models being wrong
• More important are the technical limits
• But may not need “the works” depending on
application
• Data!
• Were (are?) simpler approaches possible?
• Identify the plausible & the potentially important
• Refuse to be precise / design to fail?
• Is consistency across scenarios needed?
• Some would help
• More important is compatibility and comparability