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Timeline of Climate Modeling
Transcript of Timeline of Climate Modeling
John Tyndall measures infrared
absorption of Greenhouse Gases
Svante Arrhenius calculates effect of
doubling (& trebling) CO2 concentration
Primitive Equations Isolated
Vilhelm Bjerknes identifies the equations for atmosphere dynamics
Charles Keeling begins detailed measurements of CO2 at Mauna Loa
The Charney Report
Jule Charney chairs a National Academy review; concludes equilibrium sensitivity is +3°C (±1.5)
Ed Lorenz discovers the chaotic
behaviour of meteorological processes
Lewis Fry Richardson computes a 6 hour forecast (2 years work by hand)
The history of Climate Modeling: a Timeline
Steve Easterbrook, Dept of Computer Science, U of T
1850 - 1900:
How does the "Green-
house Effect" work?
1900 - 1949
Can we calculate the
How much warmer will it get?
Where will the impacts occur?
What are our policy choices?
John Von Neumann designs ENIAC,
applies it to weather forecasting
First Coupled Model Intercomparison Project (CMIP)
First GCMs - Global Circulation Models
Bert Bolin appointed first chair;
goal is to assess the science
International Treaty signed at the
'92 Earth Summit in Rio de Janeiro
Fifth Coupled Model Intercomparison Project (CMIP)
Earth System Models
GFDL: Smagorinsky & Manabe
UCLA: Mintz & Arakawa
NCAR: Kasahara & Washington
source: Manabe & Wetherald, 1975
9-layer model (most others 2 layer)
Overcame numerical instability with
Used height rather than pressure
for vertical coordinate system
2008: Peter Lynch's PHONIAC
Donner et al
"The Development of
Cambridge U. Press, 2010
"Fixing the Sky"
Columbia U Press 2010
Paul N. Edwards
"A Vast Machine"
MIT Press 2011
The Era of Theoretical Meteorology (before electronic computers)
The Era of General Circulation Models
The Era of the IPCC
19th Century Atmospheric Science
Colour Palette by joy_of_summer
of ocean mixing
Roger Revelle discovers ocean layers
limit absorption of CO2 from atmosphere
First measurement of Global Warming
Guy Stewart Callendar - first empirical measurements of link between CO2 emissions and temperature change
we'll start in ...
the Charney report provides the first unequivocal warning to the US government - climate change is a serious threat
In the 1970's, there was some uncertainty on whether cooling caused by industrial pollution (e.g. sulphate particles) would be more or less than warming caused by greenhouse gases. By 1979, this debate was over - warming is bigger
and so by...
global climate modeling was well underway, with four major modeling efforts...
The models used in the Charney report trace back to...
...when the first digital computers were applied to computing atmospheric dynamics
but to understand von Neumann's forecast,
we have to go back further in time...
scientists already understood that the atmosphere keeps the earth warm; Tyndall's experiments demonstrated which gases were responsible...
it was possible to quantify the greenhouse effect more precisely, and to calculate the effect of varying the concentration of CO2
meanwhile, by the...
great progress was being made in theoretical meteorology (although it would have to await the birth of digital computers before it could be used)
the first attempt to calculate the weather using these equations had been made
Richardson imagined a 'forecast factory' with 64,000 computers (people!) on balconies in a hollow sphere, each calculating the weather at their own gridpoint, passing on their results to each neighbour. A conductor kept them to the same speed with a beam of light.
and then, in...
a paper appeared that demonstrated a relationship between the temperature record and rising GHG emissions from burning fossil fuels...
but Callendar's work was largely ignored until...
when new research in oceanography cast doubt on the ability of the oceans to absorb all of the greenhouse gases we were emitting...
and as part of the international geophysical year in...
new detailed data of many aspects of global climate were collected, including, for the first time, a detailed record of rising greenhouse gas concentrations
So, back to...
and that very first computational weather forecast on ENIAC, the first programmable digital computer...
The ENIAC forecast covered only N. America, using a 15 x 13 grid. It took 24 hours to compute a 24 hour forecast
In 2008, Peter Lynch re-implemented the original ENIAC forecast on a Nokia cellphone. The forecast took less than a second to compute
Which is a demonstration of the power of Moore's Law: Since the 1950's computer speeds have doubled roughly every 1.5 years
Moore's law had turned atmospheric circulation models into practical tools, both for research and for operational weather forecasting.
But in that year...
Chaos theory means weather forecasts are limited by the accuracy of the initial conditions. Any errors grow rapidly (e.g. doubling every 1-2 days of forecast), so beyond a week or two the forecast is useless. Nowadays, forecasters do many runs to give probabilistic forecasts.
Climate models don't have this problem, as they simulate
typical weather (i.e. climate) rather than actual weather.
The climate settles into different stable regimes, depending on the boundary conditions. Models can simulate these stable regimes fairly easily, but it's harder to determine precisely the tipping points that flip the climate from one regime to another.
As we get more and more physical processes into the climate models, they get better at reproducing observed climate changes, both in the recent past and in prehistoric times.
which brings us back to
and the presentation of the Charney report to the US National Academies
a few years later, and after a particularly hot summer in the US in...
The United Nations assembled an international body to assess the science for the benefit of policy-makers.
and four years later, in
To respond to the IPCC's needs, by...
16 modeling centres around the world got together to compare their models' projections of future climate change
The models had evolved to encompass more than just the dynamics of atmosphere and oceans. They had become...
So how do today's climate models work?
This 4 minute movie from IPSL explains...
...and as an example of what the models can do,
watch this simulation of ocean temperatures from GFDL
And in the last few years...
In preparation for the 5th IPCC report, 24 modeling centres, with 45 different models, have run their models on up to 110 different experiments
Projections of future climate are based on four "Representative Concentration Pathways", to capture the spread of likely economic and technological developments over the 21st Century.
However, Chaos theory matters in another way...
Image Source: Peterson et al, 2008. http://dx.doi.org/10.1175/2008BAMS2370.1
image source: http://www.bbc.com/news/science-environment-15093234
image source: Arrhenius, 1896, http://rsclive3.rsc.org/images/Arrhenius1896_tcm18-173546.pdf
Image credit: F. Schuiten
source: Callendar, 1938. http://dx.doi.org/10.1002/qj.49706427503
image source: http://earthobservatory.nasa.gov/Features/OceanCarbon/
Two months of simulated weather on a 12 variable model.
Starting value of
Kyoto 1997 - COP3
Source: IPCC AR4 WG1 Fig 10.1 http://www.ipcc.ch/publications_and_data/ar4/wg1/en/figure-10-1.html
source: Alexander & Easterbrook, 2015. http://dx.doi.org/10.5194/gmdd-8-351-2015