The EPA and Met Eireann in association with the National Dialogue on Climate Action hosted this public lecture on 20 November 2019. After decades of denial, the global community has now accepted the reality of human-induced climate change and the imperative of tackling it. So is the climate science done, and all we need now are technological solutions? This talk will argue that the role for climate science is greater than ever before, as we face the challenges of how to mitigate global warming, how to adapt to a changing climate, and how to make ourselves more resilient to weather and climate hazards. Dame Julia Slingo served as Chief Scientist of the UK Met Office from 2009 until her retirement in 2016. Through her career, she has worked at the European Centre for Medium-range Weather Forecasts (ECMWF), the US National Center for Atmospheric Research (NCAR) and Reading University. Dame Julia was elected a Fellow of the Royal Society in 2015 and Foreign Member of the US National Academy of Engineering in 2016.

1. Facing up to Climate Change:
Where next for Climate Science?
Dame Julia Slingo FRS Dublin 2019

2. • Global surface temperature rise is halfway to 20C.
• Global sea level rise is only a third of what is likely by
2100.
• Already used two thirds of total global carbon emissions
to have a 66% or greater chance of staying within 20C.
Paris 2015: The ‘end of the beginning’ for Climate Science
The Earth is warming and it’s due to us
The Paris Agreement set a long-term goal of keeping the
increase in global average surface temperature to well
below 2 °C above pre-industrial levels, and to strive to
limit the increase to 1.5 °C.

3. Where does all the heat go?
Where does all the carbon go?
Where does all the fresh water go?
BUT SOME BIG SCIENCE QUESTIONS REMAIN
UNANSWERED THAT HAVE PROFOUND
CONSEQUENCES FOR OUR FUTURE ACTIONS

4. Global Mean Surface Temperature Record
WHERE DOES ALL THE HEAT GO?
The ‘Pause’

5. Rising Sea Levels
Oceans take up 90% of
additional energy
trapped in the planet
Increase in Mass from
melting glaciers
Water expands as it
warms

6. FACTORS INFLUENCING FUTURE SEA LEVEL RISE

7. Global carbon
cycle currently
absorbs about
half of our
emissions
Will it
continue to
do so?
WHERE DOES ALL THE CARBON GO?

8. Climate Feedbacks on the Carbon Cycle:
Impact of 2015/16 El Nino on ability of the
terrestrial biosphere to take up carbon
Liu et al, 2017

9. WHERE DOES ALL THE FRESH WATER GO?

10. Cloud feedbacks and changes in rainfall remain very uncertain

11. How does water move through the land system?
From the sky to the sea – what happens below the surface……
Linking Hydrology and Meteorology

12. GRACE Groundwater storage annual trends for
Earth's 37 largest aquifers (2003 - 2013):
One third of the largest
aquifers are being
depleted while
receiving little to no
recharge.
Exploiting ancient water
Water will become
Earth’s most precious
resource

13. Climate Sensitivity is all about knowing where heat,
carbon and water go
?
˚C
0 1 2 3 4 5 6
? AR4 : “Values
substantially higher than
4.5°C cannot be excluded
but model agreement with
observations not as good
for those values”
Likely range (>66%)
AR4
Very unlikely beyond
end of line (<10%)
Extremely unlikely
beyond end of line
(<5%)
Range
(no likelihood given)
AR5
AR3
AR2
AR1
Best estimate
Long term equilibrium response to CO2 doubling

14. • How well do we know today’s physical climate baseline risk from extreme
weather and climate hazards, due to natural variability?
• How will our physical climate risk baseline evolve, in terms of changes in
frequency and/or intensity of hazards?
• What are the longer-term risks of dangerous climate change, including
potential tipping points?
• How might new knowledge of Climate and Earth system feedbacks affect
the pace and depth of mitigation actions to stay within 1.5/2oC target?
Taking the planet into uncharted territory

15. How well do we know today’s physical climate baseline risk?
Ex-Hurricane Ophelia

16. “This Monument was erected by Mr
THOMAS MANSEL of this Towne in
Remembrance of a Great Hailstorme
May 16 AD 1709 between the hours of
one and four in the afternoon; which
stopping the course of a small River
West of this Church caus’d of a sudden
and Extraordinary Flood in the Abbey-
garden and Green, running with so
Rapid a stream that it forc’d open the
North-door of the Church, displac’d
and remov’d about 7222 foot of the
Pavement and was 2 foot and 10
Inches high as it pass’d out of the South
Door. “ Sherborne Abbey, Dorset

17. Thames 2014 Lake District 2015
“How much rain could we get? What is a plausible worst case for UK
flooding in the next 10 years?” – UK Government
A FLOOD RISK STORY FOR THE UK

18. Observational
record is too short
to characterise
extremes
Rain-rich/flood-rich, rain-
poor/flood-poor periods
from natural variability
England/Wales Winter Rainfall
River Severn Flow Rates
Is this Climate
Change?

19. Worlds that might have been….
‘One flap of a seagull’s wings may forever change the
course of the weather’
Ed Lorenz and ‘The Essence of Chaos’
• All regional and local extreme events are tied to specific
synoptic weather or climate patterns.
• Chaos Theory tells us that there are many paths that the
world’s weather could have taken – observations are just
one plausible realisation.
• Can we use multiple realisations of our weather from
simulations to find unprecedented extremes even for the
current climate?
New approaches to estimating risks from extremes

20. Looking for ‘black swan’ events for today
South East England monthly rainfall totals
35 observed Winters
1400 simulated Winters
40 x more samples
Thompson et al. 2017
January 2014
Thames Flooding

21. On average, 5-10% risk of
unprecedented rainfall in
any winter
1% risk of exceeding the
observed monthly
maximum rainfall by 20 -
25% for each winter
Risk of an unprecedented month of rainfall occurring in a
UK region during a given winter
Example: South East
England monthly rainfall
totals

22. Carlisle case study – observed December 2015 flood extent and modelled stress test scenario.
Note that due to the
shape of the flood plain,
the differences in extent
are very small
Results combined with
knowledge of key
infrastructure to assess
potential impacts
Observed
Observed + 20%
From global to local: what does more rain look like?

23. How will our physical climate risk baseline evolve?
UKCP18
• New Global
Projections
• New Land
Projections at
12km
• First Local
Projections at
2.2km

24. Latest Met Office
Global Model
(HadGEM3) has a
higher Equilibrium
Climate Sensitivity of
5.20C, in line with
other models being
submitted to IPCC AR6
UKCP18
Global Mean Surface Temperature Change:
High Emission Scenario

25. Leads to stronger climate
change response over
the UK
We will need to assess
this new evidence,
decide how credible it is,
and consider its impact
on risks
UKCP18
England Summer Temps
England Winter Temps
England Summer Rainfall
England Winter Rainfall

26. Nested km-scale grid model over the UK
From Today’s Local Weather to Future Local Climate Risk
Red Alert for
Wales Extreme
Winds: February
2014
Red Alert for
Severe South-
West Flooding:
July 2012
UKCP18: New evidence from 2.2km regional climate scenarios may substantially
alter flood risk, storm surge and wind damage assessments

27. There are many
potential tipping
points and
irreversible changes
in the Earth system –
very few of them are
properly understood
and quantified
What are the longer-term risks of dangerous climate
change, including potential tipping points?

28. Okjökull Remembered
Okjökull (Ok glacier) was
a glacier in western
Iceland on top of the
volcanic mountain, Ok.

29. CCS: CARBON CAPTURE
AND STORAGE
AGRICULTURE, FOREST &
LAND USE CARBON
DIOXIDE REMOVAL
TECHNOLOGICAL
CARBON DIOXIDE
REMOVAL: BIO-ENERGY
OPTIONS FOR
MANAGING CARBON
EMISSIONS TO STAY
WITHIN 1.5OC
How might new knowledge of
Climate and Earth system
feedbacks affect the pace and
depth of mitigation actions to
stay within 1.5/2oC target?

30. 2ºC Budget
4ºC Budget
~550GtC
Already emitted
From IPCC AR5 WG1, 2013
790GtC
Allowable budget

31. New Insights: Additional Earth System feedbacks may limit
our allowable carbon budget
Nitrogen cycle may limit the
efficacy of the carbon cycle.
Carbon emissions
from permafrost

32. 4ºC Budget
From IPCC AR5 WG1, 2013
2ºC Budget

33. Piers Sellers (1955 – 2016): British Climate
Scientist and NASA Astronaut

37. CLIMATE SCIENCE: HELPING US TO LIVE SAFELY AND
SUSTAINABLY ON OUR PLANET