presentation boers - trends in cloudiness
DESCRIPTION
10/04/2013 TU Delft Climate Institute Symposium: Do clouds change in a warming climate?TRANSCRIPT
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Trends in cloudiness
1)What is a cloud?2)Accuracy and precision [targets and shots]3)Global trends in clouds [monitoring / precision]4)Trends in clouds over the Netherlands [lack of continuity]5)Trends in fogs over the Netherlands [understanding change]6)Reconstruction of aerosol concentrations from RH <> Visibility obs7)Climate change detection and the public8)Job qualification for a climate monitoring expert
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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What is a cloud?
A cloud consists of droplets or ice crystals.
A droplet is an activated haze particle.
An activated haze particle is a haze particle for which the equilibrium saturation vapor pressure at its water surface is not in equilibrium with the ambient vapor pressure.
Activation is unstable growth
Within the context of cloud physics very precise statements, but for
observation purposes practically meaningless
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Accuracy and Precision [Targets and Shots]The target is to say something about the existence of droplets and ice crystals
The shots we fire are interpretations of visual observations and of radiometer observations
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Accuracy
Precision
Shots at a target
Target
“Congratulations, you missed the target with great precision!”
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Accuracy and Precision
Precision (Monitoring)
Accuracy(Measurements)
Low High
Low
High
MonitoringChange
Understanding Processes
Understanding Change
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Often, Precision is the only attainable thing
Repeatibility, calibration, continuity, signal-to-noise issues
data
time
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Problems
Trends occur at time scales that may be larger than a life time.
During those times observation methods changed.
During those times recording methods changed.
During those times the location of the measurement changed.
During those times the instrument changed.
During those times the number of observations changed.
During those times the world changed.
Trend detection is one of the most challenging topics in data analysis
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Why are we interested in trends in cloudiness?
The single largest source of uncertainty in global climate models is the response of clouds to climate change.
What do we use for observations?
a) The Observer (1850 – 2000)b) Automatic surface observations (1995 – now)c) Satellites (1980’s – now)
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Black = AllRed = OceanGreen = Land[all satellite]
Black = Surface ObsRed = Satellite
Satellite: Regionaltrends
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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SurfaceObservations
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Global trends in cloudiness: Read it and weep…….
Global-average trends of cloud cover suggest a small decline in total cloud cover, on the order of 0.4% per decade. [Eastman et al. 2013, Surface Observer data]
High clouds show a small but statistically significant increase in the Tropics and the Northern Hemisphere. At other levels no change is detected [Wylie et al. 2005, IR satellite data]
The global average trend of total cloud cover over land is small, 0.7% decade, offsetting the small positive trend that had been found for the ocean, and resulting in no significant trend for the land–ocean average. [Warren et al, 2007; Surface observation data]
The International Satellite Cloud Climatology Project (ISCCP) shows a decrease in total global cloud cover during most of a 25 year period [Wylie et al., mostly Vis satellite data]
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Trends in cloudiness over the Netherlands
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
13The Observer died, the Ceilometer was born
The sad case of the lost Observer
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
14 Observer
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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A Ceilometer is a colourblind Observer with a telescope and a serious spinal injury
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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The Observer
The Ceilometer
With a ceilometer, it’s either Yes or No.The average of Yes and No does not exist.
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Goes back to 17 april 1849.
Where is it??
The lost Observer??Vienna Congress 1875
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Trends in fog
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Understanding change1) Good long record of relative humidity2) Good long record of visibility
The link between the two is: humidification of aerosols as relative humidity nears 100%.
So, try to reconstruct aerosol concentration using a model that links aerosols through relative humidity to visibility
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Reconstruction of aerosol concentration
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Free-data access and the public
Someone who is a little computer literate can compose the following graph by Googling some data from the Internet
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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A management decision
Climate change
Climatechange
true truetrue
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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So, the graph conveys two truths:
About climate changeAbout a management decision to change observations
The public is asked to discern between these two truths
Can they do that????
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Confirmation biasI believe that sudden climate change might happen. After all, it was in the news the other day.
I dont think the weather guys are doing a good job. After all, I read on the internet that the IPCC was wrong.
The graph looks very good. After all, I made it myself. It has nice fonts and nice colors and shows a sudden change.
The graph confirms what I believe.
“Contrary to the rules of philosophers of science, who advise testing hypotheses by trying to refute them, people (and scientists, quite often) seek data that are likely to be compatible with the beliefs they currently hold.”Daniel Kahneman, Nobel Prize Winner in Economics, 2002Required reading: ‘Thinking Fast and Slow’
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Job qualifications for climate monitoring expert
1) Start Young, Die Old2) Autistic /Myopic3) Asocial4) Micromanager5) Ultraconservative6) Ultrapersistent7) No ambition, no upward mobility8) No wish to publish anything9) Low pay not a problem10) No internet connection, no Twitter, 11) No Facebook
Be a nerd!!!
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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And the biggest of them all is……
R. Boers, KNMI, TUDelft Science Centre, 10-04-2013
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Required reading for anyone interested in pursuing a career in climate monitoring
Annu. Rev. Energy Environ. 1998. 23:25–82
Copyright @1998 by Annual Reviews.