Download Climate Change

IPCC Climate Change Report
Moving Towards Consensus
Based on real world data
IPCC Consensus process is
Conservative by Nature
The most Recent (2013) IPCC report is, by far.
The most comprehensive compared to the
previous 4
Climate Change
2013
observations
FAR 1990
SAR 1995
TAR 2001
AR4 2007
AR5 2013
11 Chapters
11 Chapters
14 Chapters
11 Chapters
14 Chapters
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paleoclimate
sea level
clouds
carbon cycle
regional change
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A Key Observation
Warming since 1850
c/o Gian-Kasper Plattner, 10-8-13
Preponderance of Evidence
Climate Modeling Evolution
We have the
Sun, some
Rain and
some CO2
pollution,
that’s it
Climate Modeling Evolution
Now we add in
Clouds, the
land surface,
and ice
reflectivity
Climate Modeling Evolution
In the First
Assessment Report
(FAR – 1990) the
Ocean as CO2 sink
was now added in
Climate Modeling Evolution
By the mid 1990s
sulfur emissions from
volcanoes and/or
industry were added
as cooling agents
(this is because of
Pinatubo)) and the
role of surface ocean
current transport was
more strongly
considered
Pinatubo Ash Eruption
Climate Modeling Evolution
By 2001 aerosol
scattering (very
complicated) is
now incorporated
as is deep ocean
transport, the
actual carbon
cycle and the role
that rivers play in
the hydrological
cycle
Climate Modeling Evolution
Finally
atmospheric
chemistry is
considered in the
2007 report along
with reflectivity
changes on the
Earth due to
changing
vegetation
patterns
Much better grid
resolution for climate
data is also achieved in
this process, but its still
not fine enough to even
include CLOUDS!
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Data-Model
Comparisons
Models constructed to simulate Modern circulation
• Changes based on Earth History inserted in model
• Climate output compared with observations
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One-Dimensional Models
Simplified representation
of of entire planet
• Model driven by global
mean incoming solar
radiation and albedo
Single vertical column of
air divided into layers
• Each layer contains
important constituents
(dust, greenhouse
gases, etc)
• Layers exchange only
vertically
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Two-Dimensional Models
Multi-layered
atmosphere coupled
with Earth’s physical
properties averaged
by latitude
Allows simulations of
climatic processes
that vary with latitude
• Angle of incoming
solar radiation
• Albedo of Earth’s
surface
• Heat capacity
changes
Three-Dimensional Models GCM
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3-D representation of Earth’s
surface and atmosphere
Most sophisticated attempt to
simulate the climate system
3-D model based on
fundamental laws of physics:
• Conservation of energy
• Conservation of
momentum
• Conservation of mass
• Ideal Gas Law
Model Resolution

Can’t image New Zealand, for example – (2°
lat x 3° long) – this deficiency matters!
Steady State Tub

If flux of tracer into and out of
reservoir are equal, the system is at
steady state
Residence Time

Time it takes for tracer to pass
through tub
• Residence time = reservoir size/flux
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Residence time of tracer typically >
mixing time of the ocean (1500 y)
In this way, the oceans are an
enormous buffer (on short time
scales)
Basic Approach double CO2 and
model planetary response
Convolution of positive and negative
forcings are what we observe.
 GHG produces the net positive here
An Inconvenient Coincidence
Equilibrium Temperature
 Planet radiates as a blackbody in TE with
incoming solar radiation:
A = Albedo; L = 1370 watts per sq meter
T = 278(1-A)4
T = 255K for A=0.32
This is not the right answer compared to
observations
The Role of the Atmosphere
Fo = incident flux
Ts = transmission % incoming
Tt = transmission % outgoing
Fg = Flux from ground
Fa = Flux from the atmosphere.
Fo = Fa + TtFg top of atmosphere equilibrium
Let Fa = Fo –TtFg
Fg = Fa + TsFo outgoing ground equilibrium
F g = Fo
https://www.youtube.com/watch?
v=otRPf3rRwZk