The IES 2013 Burntwood Lecture given by Julia Slingo from the Met Office on the topic: Why Climate Models are the greatest feat of modern science. #BWL13

1. Why Climate Models are the
Greatest Feat of Modern Science
Julia Slingo, Met Office

2. 28th October 2013:
St Jude Storm
 17 fatalities (6 in UK)
 London transport shut down during peak of storm (130 Heathrow flights
cancelled)
 850,000 homes lost power
 Dungeness B Nuclear Power station shut down
 Landslip and 100+ trees uprooted over rail lines resulting in long delays
 Ferries badly affected; Port of Dover closed 06:00 to 09:30

3. 5 day forecast – before the
storm even existed!
The same model which produced this forecast is used to simulate
© Crown copyright Met Office
the atmosphere in the climate model

4. ‘Riding on the back’ of 40 years of
improvements in forecast skill
Error in Mean Sea Level Pressure (mb) for the Euro-Atlantic Region
Tomorrow’s weather is the same as today’s!
Day 2
Day 3
Day 5
Day 4
Day 1
‘1 Day per Decade’

5. Content Divider
How does the
work?
climate system

6. Global Mean Climate System
From Trenberth et al., 2009

7. Role of atmosphere and ocean
dynamics in energy transports
Total radiative heating (Wm-2)
Poleward transports
(PetaWatts) required to
balance radiative
heating/cooling
Total
Atmosphere
Oceans

8. Atmospheric Energy Transport
Energy transports achieved
through planetary
circulations, waves and
weather systems
• Fluid on a rotating sphere –
conservation of angular
momentum
• Heated differentially between
the equator and poles
• Effects of land masses and
mountains
• Phase changes of water –
moving heat around the
system

9. Ocean Energy Transport
From S. Rahmstorf: Thermohaline Ocean Circulation. In: Encyclopedia of QuaternarySciences, Edited by
S. A. Elias. Elsevier, Amsterdam 2006 (see www.pik-potsdam.de/~stefan/thc_fact_sheet.html)

10. Global Water Cycle:
Phase changes of water move heat around
the system
Units 1012 m3/year

11. Global Water Cycle:
Phase changes of water move heat around
the system
Annual Mean Precipitation (Rain and Snow: mm/day)

12. Global Water Cycle:
Phase changes of water move heat around
the planet
Annual Mean Precipitation minus Evaporation (mm/day)
Precipitation = Surface Evaporation + Atmospheric Transport

13. Annual Mean Sea Surface Salinity
reflects the global water cycle

14. How much of this did we know when I
began my career in 1972?
X
X
None of the global budgets, none of the hydrological cycle
?
?
A little bit about the oceans and a little bit about global weather

15. Climate Model
simulation of Net
Radiation and
Atmospheric
Transports. Ocean
transports are inferred
as a residual.
Climate models were beginning to tell us things
about the climate system that we couldn’t
observe.

16. Content Divider
What is Climate Modelling?

17. Building a Climate Model:
Where to Start?
Climate Models are based on fundamental equations of
motion (Newton’s 2nd Law of Motion), mass continuity, moist
thermodynamics and radiative transfer
These govern:
• Flow of air and water - winds in the atmosphere, currents in the
ocean.
• Exchange of heat (sensible and latent) and momentum between the
atmosphere and the earth’s surface
• Release of latent heat by condensation during the formation of clouds
and raindrops
• Absorption of solar radiation and emission of thermal (infra-red)
radiation

18. Fundamentals of climate
(and weather) modelling
 Represent the earth by a grid of squares, typically of length 100 km or smaller.
 Atmosphere and oceans are divided into vertical slices of varying depths, typically
70 or more.
 3-dimensional picture of the state of the atmosphere and oceans.
 Integrate equations of motion and thermodynamics forward in time.

19. Representing Unresolved
Processes: Parametrization
Boundary layer
turbulence and mixing
Radiation
Cumulus convection
Precipitation
Clouds and
microphysics
Effects of mountains
Atmospheric
composition

20. Evolution of climate models
over time: Resolution
1990
1996
© Crown copyright Met Office
2001
2007

21. Evolution of climate models
over time: Complexity

22. Earth Observation – giving the
planet a ‘health check’!
We know an immense amount about what is happening to the
planet – but we don’t necessarily know why

23. Climate Models as the
Content Divider
‘Laboratories’ of Climate Science

24. Does soil moisture affect the
behaviour of the West
African Monsoon?
Climate models were beginning to tell us things
about how the climate system works and what’s
important
Wet Soil
Dry Soil

25. Predicting Winter Climate:
Understanding the drivers of the
North Atlantic Oscillation

26. Understanding WHY the
world is warming
‘Extremely likely (95-100%) that most of observed increase in global surface
© Crown copyright Met Office
temperature since 1951 has been caused by human influence.’ – IPCC 2013

27. ‘Hiatus’ in global surface warming

28. Spatial Pattern of the ‘Hiatus’
hints at the oceans
Sea Surface Temperature
2000-2012 minus 1990-1999

29. Pacific Ocean implicated in the
‘hiatus’ in models
From Meehl et al. 2013

30. Models suggest that heat is
sequestered into the deep ocean
during a ‘hiatus’
From Meehl et al. 2013

31. Content Divider
Climate modelling:
A modern
Renaissance Science?

32. Mathematics
c pd v 
Dr u uv tan 
 uw


 2 sin  v 
    2 cos  w   S u
Dt
r
r cos  
 r

c pd 
Dr v u 2 tan 
 vw 

 2 sin  u 
 
 Sv

Dt
r
r 
r 

 
 u 2  v 2   2 cos  u  S w
Dr w
 
 c pd v


Dt
r
r
r

g
   u    v  w 
Dr
2
2
  y r cos    y r cos    r cos     r   r   0
Dt
 

 

Dr 
S
Dt
Met Office Unified Model makes neither hydrostatic or
shallow atmosphere approximations

33. Mathematics
How to solve these equations numerically on a grid:
 Accuracy and Conservation of fundamental properties
 Efficient and Scalable code
 Robust and Stable code
v
Icosahedral-triangles
Icosahedral-hexagons
Cubed Sphere

34. Mathematics, Computer Science
Some of the Machines that I’ve worked on!
1980s: NCAR Cray 1
2000s: Japanese Earth Simulator
Original weather forecasts so simple that
they can run on a mobile phone in fractions
of a second
2010s: Met Office IBM Power 7
Met Office’s current IBM Power7 machine
has peak speed of ≈ 1Petaflop
(1,000,000,000,000,000 sums per second)

35. Mathematics, Computer Science, Newtonian Physics
Geophysical flows:
Newton’s Laws of
Motion on a
Rotating Sphere
Ocean surface
temperatures simulated
by 2km ocean model.
Image courtesy of the Mercator Ocean Project, France

36. Mathematics, Computer Science, Newtonian Physics, Moist
Thermodynamics
Climate Model (HADGEM2-ES) precipitation

37. Mathematics, Computer Science, Newtonian Physics, Moist
Thermodynamics, Radiative Transfer
Gases absorb and emit infrared radiation in distinct spectral bands

38. Mathematics, Computer Science, Newtonian Physics, Moist
Thermodynamics, Radiative Transfer, Particle Microphysics
Source: Tollefson, Nature News, 2012

39. Mathematics, Computer Science, Newtonian Physics, Moist
Thermodynamics, Radiative Transfer, Particle
Microphysics, Chemistry
© Crown copyright Met Office

40. Mathematics, Computer Science, Newtonian Physics, Moist
Thermodynamics, Radiative Transfer, Particle
Microphysics, Chemistry, Biology
How water moves through a tree
Microbial structuring of marine ecosystems

41. Mathematics, Computer Science, Newtonian Physics, Moist
Thermodynamics, Radiative Transfer, Particle
Microphysics, Chemistry, Biology, Meteorology
Screenshot from a Met Office Climate Model simulation at 12km
THE VIDEO HAS BEEN REMOVED FROM THIS SLIDE IN ORDER TO MAKE
THE PRESENTATION AVAILABLE ONLINE.
© Crown copyright Met Office

42. Mathematics, Computer Science, Newtonian Physics, Moist
Thermodynamics, Radiative Transfer, Particle
Microphysics, Chemistry, Biology, Meteorology, Oceanography
Gulf Stream meanders in 1/40 ocean model
Met Office Climate Model
Met Office Ocean Model with no
ocean-atmosphere interaction

43. Mathematics, Computer Science, Newtonian Physics, Moist
Thermodynamics, Radiative Transfer, Particle
Microphysics, Chemistry, Biology, Meteorology, Oceanography, Terrestrial
Ecosystems
Modelling the Carbon Cycle
From O’Connor et al. 2011
(Met Office Hadley Centre)
Future
Methane
Emissions

44. Mathematics, Computer Science, Newtonian Physics, Moist
Thermodynamics, Radiative Transfer, Particle
Microphysics, Chemistry, Biology, Meteorology, Oceanography, Terrestrial
Ecosystems, Marine Ecosystems
Chlorophyll (April 2008)
Phytoplankton (algal) blooms around
the UK
Image from Western Channel Observatory
Chlorophyll from the Met Office’s NEMOShelfERSEM operational model. The yellow and orange
regions show areas of algal blooms.

45. Mathematics, Computer Science, Newtonian Physics, Moist
Thermodynamics, Radiative Transfer, Particle
Microphysics, Chemistry, Biology, Meteorology, Oceanography, Terrestrial
Ecosystems, Marine Ecosystems, Cryosphere.......
2012
1980
Loss of Arctic Summer Sea Ice
Met Office Climate Model:
Understanding the Arctic energy budget

46. Putting it all together: Holistic Earth System
Basic Constraints: Energy Input from the Sun, Rotation
Rate of the Planet, (Atmospheric Composition)
It works! Fundamental constraints. AR5 model biases or HadGEM2-ES results?
© Crown copyright Met Office

47. It Works!
Sea Surface Temperature
biases in Met Office Earth
System Model
(HadGEM2-ES)
Observations
HadGEM2-ES
Storm Tracks in
observations and
HadGEM2-ES

48. Climate modelling: A Predictive
Science

49. Taking the Earth into uncharted
territory?

50. Human Perturbations to the
Carbon Cycle

51. Results from my first study on CO2:
The effects of doubling CO2 concentration on
Radiative-Convective equilibrium
Effect of doubling CO2 based on
two cumulus convection schemes
NO CLOUDS
T(K)
270
280
290
300
DT(PC)
1.52
1.57
1.65
1.70
DT(CA)
1.56
1.68
1.92
2.46
WITH CLOUDS
T(K)
270
280
290
300
DT(PC)
1.40
1.44
1.40
1.40
DT(CA)
-
1.64
1.88
2.20
© Crown copyright Met Office

52. Projections of future temperature rise
• Global warming >2˚C is likely for scenarios with little mitigation of
emissions. No mitigation leads to a world more than 4˚C warmer
than pre-industrial times
Inter-Governmental Panel on Climate Change (2013)

53. Projections of future sea level rise
Long Term Commitment to Climate Change
• Global average sea level will rise during the 21st century; it is very
likely that it will rise faster than it has during the last 40 years.
Inter-Governmental Panel on Climate Change (2013)

54. There will be large geographical variations
Inter-Governmental Panel on Climate Change (2013)

55. So if climate models are such an
achievement, why are we still uncertain?
Relative importance of each source of uncertainty in
decadal mean surface air temperature predictions
VARIABILITY
Uncertainty comes
from:
• Natural variability
• Model uncertainty
• Scenario uncertainty
SCENARIO
MODEL
© Crown copyright Met Office
From Hawkins and Sutton (2009)

56. Representing Unresolved
Processes: Parametrization
Boundary layer
turbulence and mixing
Radiation
Cumulus convection
Precipitation
Clouds and
microphysics
Effects of mountains
Atmospheric
composition

57. Climate modelling: Helping us
Plan for a Safe and Sustainable
Future

58. „Circle of Securities‟
Water
Migration
Economic
Climate
Variability
and Change
Health
Urbanisation
Population growth
Political
Energy
Food

59. Climate Service UK
Working together to prepare for tomorrow
• Saving lives and livelihoods
• Delivering resilience and preparedness
• Making wise choices for future adaptation
• Avoiding dangerous climate change
• Supporting growth and the green economy
© Crown copyright Met Office
© Crown copyright Met Office

60. • 1953 East coast storm surge killed 307 in the UK and
flooded 32,000 industrial facilities
• Estimated £200bn value of property in Thames
floodplain, 1.1 million employees, 55,000 properties
• TE2100 science avoided up to £20bn capital expenditure
through more robust predictions and scenarios
© Crown copyright Met Office

61. To Recap
• Based on fundamental and immutable laws
• Include many science disciplines – ‘renaissance’ science
• Arguably the largest and most complex codes ever
written
• Simulate the wealth of processes and phenomena in the
climate system
• Enable us to understand how the climate system works
• Enable us understand why climate is changing
• Enable us to ‘see into the future’ and take action
Scale of the Enterprise to match the Scale of

62. ‘For the Relief of Man’s Estate’
“For men have entered into a desire of learning and
knowledge, sometimes upon a natural curiosity and inquisitive
appetite; sometimes to entertain their minds with variety and
delight; sometimes for ornament and reputation; and sometimes
to enable them to victory of wit and contradiction; and most times
for lucre and profession; and seldom sincerely to give a true
account of their gift of reason, to the benefit and use of men: ……
a rich storehouse, for the glory of the Creator and the relief of
man's estate. “
Francis Bacon, The Advancement of Learning (1605)

63. “I do not know what I may appear to the world, but to myself I
seem to have been only like a boy playing on the seashore, and diverting myself in now and then finding a
smoother pebble or a prettier shell than ordinary, whilst the
great ocean of truth lay all undiscovered before me.” Isaac
Newton
Climate
Modelling
– Work in
Progress

64. Why Climate Models are the
Greatest Feat of Modern Science
Have I convinced you?