Download Climate, Climate Change Nuclear Power and the Alternatives

Climate, Climate Change
Nuclear Power and the
Alternatives
Climate, Climate Change
Nuclear Power and the
Alternatives
PHYC 40050
Peter Lynch
Meteorology & Climate Centre
School of Mathematical Sciences
University College Dublin
Introduction to Meteorology & Climate
Lecture 7
Introduction to Meteorology & Climate
What controls surface
temperature on Earth?
Paleoclimate
insolation
Based on lectures prepared by
Dr Rodrigo Caballero
UCD Meteorology & Climate Centre
thermal
radiation
some
reflection
Introduction to Meteorology & Climate
Black body radiation
Introduction to Meteorology & Climate
The “bare rock” temperature
In steady state,
Ein = Eout
Ein = π R2 S (1–α
α)
A black body:
1) absorbs all radiation falling on it (i.e. no reflection)
2) emits radiation according to the Planck function:
Total emission per unit area is
Eout= 4π R2 σ T4
Putting it all together:
R =radius α=albedo
I = σ T4
Introduction to Meteorology & Climate
Introduction to Meteorology & Climate
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Greenhouse effect: how it works
Does it work?
z
Well, sort of …
Bare rock
temp (K)
Observed
surface temp
255
232
440
210
288
740
440
210
Earth
Venus
Mercury
Mars
thermal radiation
can escape to
space only from
the emission level
(~6 km high)
Nitrogen (N2)
Oxygen (O2)
Argon (Ar)
78.08
20.95
0.93
temp
Greenhouse effect: good or bad?
But ongoing anthropogenic emission of
“greenhouse gases” is increasing the strength of
the greenhouse, and this can be bad:
bad: humanity is
vulnerable to changes in climate.
only these interact
with thermal radiation
But how does increasing greenhouse gas
concentration affect surface temperature?
temperature?
Introduction to Meteorology & Climate
Introduction to Meteorology & Climate
Enhanced greenhouse effect
σ (Te–∆ T)4
z
σ Te4
ze
Ts
Greenhouse effect per se is a good thing: without
it, surface temperature would be too low to
support life.
Carbon dioxide (CO2)
0.038
Methane (CH4)
0.0002
0.00001
Ozone (O3)
Water vapor (H2O)
0 – 5 (variable!!)
increased
greenhouse
gases cause
emission level
to rise, throwing
planet out of
balance
Te
Introduction to Meteorology & Climate
Which are the greenhouse gases?
Fraction (%)
S (1–α)/4
sunlight goes
all the way down
and heats surface
temperature decreases with height
lapse rate is controlled by thermodynamics
and turbulent heat transport
Introduction to Meteorology & Climate
Constituent
σ Te4
Surface temperature over the past 1000 years
S (1–α)/4
sunlight goes
all the way down
and heats surface
Te
temperature
increases to re-establish
equilibrium
temp
Ts Ts+∆ T
Introduction to Meteorology & Climate
Introduction to Meteorology & Climate
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Carbon dioxide (CO2) over the last 1000 years
Predictions of future
warming
big problems
problems
OK, maybe
Introduction to Meteorology & Climate
Introduction to Meteorology & Climate
Feedback: the general idea
Increase
CO2
Increase
temp
Increase
X
positive
feedback
Introduction to Meteorology & Climate
Ice albedo feedback
As surface temperature increases, some of the ice in the
polar ice caps melts, exposing ocean or boreal forest
Ice is much more reflective to sunlight than ocean or
forest
So the feedback goes like this:
Increased CO2
—› raises T
—› melts some ice
—› decreases reflectivity
—› more insolation is absorbed
—› raises T even further
Introduction to Meteorology & Climate
Important feedbacks
Ice albedo feedback
Water vapour feedback
Cloud feedback
(there are more, but these are the biggest)
Introduction to Meteorology & Climate
Water vapour feedback
Relative humidity stays roughly constant as climate warms
Since RH = w/ws(T)
(T) and ws(T)
(T) increases exponentially
with T, then humidity increases rapidly with T
So the feedback goes like this:
Increased CO2
—› raises emission level
—› raises T
—› raises humidity
—› raises emission level even further
—› raises T even further
Introduction to Meteorology & Climate
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σ Te4
z
Cloud feedback
Climate change in the past
S (1–α)/4
HIGH CLOUD:
higher albedo => cooling
higher emission level => warming
net effect = ?
LOW CLOUD:
higher albedo => cooling
Introduction to Meteorology & Climate
The Greenland ice sheet
Introduction to Meteorology & Climate
Introduction to Meteorology & Climate
Ice sheets as climate archives
Introduction to Meteorology & Climate
Ice core
GISP2 drill site
Introduction to Meteorology & Climate
Introduction to Meteorology & Climate
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Ice core closeclose-up showing
annual layers
Layer-by-layer analysis of isotopic
composition yields temperature history
Ice core
warehouse
Introduction to Meteorology & Climate
Introduction to Meteorology & Climate
A similar trick, in the ocean
Introduction to Meteorology & Climate
Introduction to Meteorology & Climate
Ocean sediment core
Introduction to Meteorology & Climate
Introduction to Meteorology & Climate
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Snowball Earth
Foraminifera
The Super
Greenhouse
The Ice Ages
Introduction to Meteorology & Climate
Introduction to Meteorology & Climate
Snowball Earth
Earth is thought to have
fallen into the ice-covered
state around 750 million
years ago.
At that time, insolation was
about 6% lower than today.
Introduction to Meteorology & Climate
What it might have
looked like:
Ice punctured by volcanos
(Vatnajokull, Iceland)
Photosynthetic life may
have survived in areas
with frequent cracks in
the ice
Introduction to Meteorology & Climate
Ice Ages
Introduction to Meteorology & Climate
Introduction to Meteorology & Climate
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The MilankovitchIntroduction
hypothesis
to Meteorology & Climate
The thermohaline conveyor belt
Introduction to Meteorology & Climate
Introduction to Meteorology & Climate
Effects of conveyor belt
shutdown … ?????
Introduction to Meteorology & Climate
The SuperSuper-Greenhouse
Introduction to Meteorology & Climate
Introduction to Meteorology & Climate
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Eocene surface temperature
(50 million years ago)
Northern Canada today
surface temperature (oC)
latitude
Then
Now
Introduction to Meteorology & Climate
Northern Canada
50 million years ago
Introduction to Meteorology & Climate
How did things get so hot?
CO2 history over the past 60 million years
modern
Introduction to Meteorology & Climate
The lowlow-gradient paradox
Introduction to Meteorology & Climate
The Paleocene-Eocene Thermal Maximum
Deep ocean and polar
temperatures rise by
about 5oC
Climate model simulations
of the Eocene climate
with CO2 at
2000 ppm
1000 ppm
500 ppm
(today’s value is 380 ppm)
Introduction to Meteorology & Climate
Introduction to Meteorology & Climate
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Methane Hydrate
Natural methane hydrate deposits
Introduction to Meteorology & Climate
Modern distribution of methane
hydrates (about 5 GT in total)
Introduction to Meteorology & Climate
The great climate experiment:
A PETMPETM-like event within a glacial climate
future CO2 if we burn all known fossil
fuel reserves at current rates
atmospheric
pCO2
(ppm)
Introduction to Meteorology & Climate
past CO2
record from
ice cores
future if we stop at 1/5 of known
reserves
time (kyr)
Introduction to Meteorology & Climate
Conclusion
Due to many and complex feedback
mechanisms, climate can be quite sensitive to
external perturbation
Through Earth history, climate variability has
been large and often fast
We still struggle to explain much of this
variability
We’re creating a climate state with no known
analog in the past
Introduction to Meteorology & Climate
End of Lecture 7
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