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
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Burntwood 2013 - Why climate models are the greatest feat of modern science, Julia Slingo
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
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’
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)
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.
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.
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
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
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
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
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
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
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)
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?
Editor's Notes
By the end of the century, the increase of global mean surface temperature above 1986-2005 levels is projected to be: 0.3-1.7˚C for a scenario with strong mitigation2.6-4.8˚C for a scenario with no mitigation
By the end of the century, the increase of global mean surface temperature above 1986-2005 levels is projected to be: 0.3-1.7˚C for a scenario with strong mitigation2.6-4.8˚C for a scenario with no mitigation