EUropean CLimate and weather Events: Interpretation and Attribution

Fraser Lott Met Office Hadley Centre fraser.lott@metoffice.gov.uk SPECS 4th General Assembly Norrköping, Tuesday 15th September 2015

EUCLEIA is a 3 year project under the FP7-SPACE Call, that

brings together 11 European partners with an outstanding

scientific profile in climate research:

The project aims to develop a quasi-operational attribution

system, well calibrated on a set of test cases for European

extreme weather, that will provide to targeted groups of

users, well verified, well understood assessments on the

extent to which certain weather-related risks have changed

due to human influences on climate.

Objectives

1. Derive user requirements

2. Develop methods for event attribution (experimental design, framing)

3. Identify key processes, represent level of confidence

4. Demonstrate on a set of test cases of European extremes

5. Deliver quasi-operational attribution assessments on a range of timescales in the aftermath of extreme events

Principles

• Event attribution aims to give the probability that an event was caused by climate change (when it is positive).

P0 or PNAT: Probability of exceeding a threshold in a “natural world” (no human influence on climate forcings).

P1 or PALL: Probability of exceeding a threshold in the real (all-forcings) world.

𝐹𝐴𝑅 = 1−𝑃𝑁𝐴𝑇𝑃𝐴𝐿𝐿

20 50 100 200 500

3.8

4

4.2

4.4

4.6

4.8

5

5.2

5.4

Return period [years]

Ja

nu

ary

me

an

pre

cip

ita

tio

n [

mm

/da

y]

Actual Conditions

pooled Natural

individual Natural

Example study

Human

influence on

climate in the

2014 Southern

England

winter floods

and their

impacts

(Massey et al)

Increase in risk of precipitation: 40% [0%:160%]

© Crown copyright Met Office

ETHZ

Edinburgh

IC3

DMI

Reading HZG

KNMI

CNRS UVSQ

Oxford

WP3 (Pete Walton, Oxford) Stakeholder User Panel

WP4 (Hans von Storch, HZG) Stakeholder Engagement WP5 (Myles Allen, Oxford) Methodologies / Framing Issues WP6 (Robert Vautard, CNRS CEA) Evaluation & Diagnostics WP7 (Geert Jan van Oldenborgh, KNMI) Targeted Test Cases WP8 (Nikos Christidis, Met Office)

Near-real time attribution service

Working Groups

Met Office

© Crown copyright Met Office

Heat waves

Cold spells

Droughts

Floods

Storm surges

TEST CASES

The 1st BAMS attribution supplement was the most read paper on the BAMS website

Contributions from 20 groups that looked at 16 events

The editors of the 2nd BAMS report were selected as Leading Global Thinkers by Foreign Policy

BAMS Attribution Studies

Stakeholder engagement

a specific event is an extreme event…

if …it is identified as such

The adjective “extreme” is given by stakeholders

to an event… if

according to this stakeholder it is rare and/or high on a scale

that has interest to the

stakeholder

What gets an extreme to be an extreme?

a) The choice of the reference

threshold on the scale

beyond which an event is

seen as rare. b) The scale chosen

a) Is it associated with the

cause (temperature,

duration etc.)

b) Is it associated with the consequence (impacts

on something deemed

important to the

stakeholder.

defines dynamically the

choice of

reference

threshold and

the nature of the scale chosen

- Focus of the stakeholder’s

interest…

- Timing…

…a

re t

he

d

ete

rmin

an

ts

as to

wh

eth

er…

In g

ene

ral te

rms

In m

ore

pre

cis

e te

rms

How do stakeholders conceptualize extremes?

While for our community it seems obvious that the the « extreme » is a meteorological extreme, many stakeholder communities identify extremes because of their « extreme » consequences.

• Survey of mayors on the German Baltic Sea coast

Stakeholder engagement

Response rate: 15% (165 answers)

What priority has climate change in your region?

Where would you find our data useful?

Framing the question

Otto et al., 2015

Uhe et al., submitted

Framing makes a huge difference, even if you use the same modelling approach, in some parts of the world

FAR for high European temperatures (Uhe et al., submitted)

Methodology

a) Observations

b) Statistical

modelling

c) 2014

d) Climatology

Some methods are

better for some things than others...

Extreme precipitation in the Danube and Elbe catchment May/June 2013

weather@home simulations observations (both Schaller et al., 2014)

Use multiple lines of evidence for attribution statements

Methodology

•Reliability diagrams do indicate the accuracy of event attribution •Two reliability diagrams (one pre-change, one post-change) are better than one •Additional climatological FAR calculations (e.g. using KNMI Climate Explorer) should support modelled FAR

Validation

Response on media timescales (fast-track attribution)

KNMI, CNRS: A fast response system has been set up by KNMI that updates datasets to the very recent past and fits extreme value distributions with time varying parameters.

Met Office: Pre-computed tables of the change in the risk of temperature extremes. Paper published in Climate Dynamics (Christidis et al., 2015)

Operational prototypes

Paris heatwave case study

Fast-track attribution can be produced from observations using KNMI Climate Explorer (e.g. for events during the previous Eucleia meeting). Now some crossover with World Weather Attribution project by ClimateCentral.

Pre-computed tables of the FAR Record global and UK temperatures

20

14

20

14

The global mean 2014 temperature is highly unlikely in a world without human influence on the climate

Human influence has also made breaking the current UK temperature record about ten times more likely (FAR = 0.9)

Met Office press release, January 2015 WMO Annual Statement, No 1152, March 2015

2014 temperatures

Upgrade our model to higher resolution

HadGEM3-A N96 L38 N216 L85 ~135km ~60km , better representation of the atmospheric vertical structure

Model development

Produced: 15 simulations over period 1960-2013 of the real world 15 simulations over period 1960-2013 of the natural world

Evaluation Attribution

Ensembles we plan to generate:

500 high-resolution simulations with ALL forcings 500 high-resolution simulations with NAT forcings

Period: 2013-2015?

• BAMS report on 2014 events release (September 2015) – 10 submissions by EUCLEIA scientists out of 34 submitted articles

• Delivery of the latest high-resolution HadGEM3-A operational attribution system (December 2015)

• Meeting at KNMI (March 2016) to coordinate test cases for: – Heat waves

– Cold spells

– Droughts

– Floods

– Storm surges

• Further stakeholder engagement

• Further development of methodologies

Still to come...