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Chapter 6:
Weather & Climate
Midterm Exam
9:33
8: 22335778
7 : 5788
6:2335778
Average Score = 77
2 Topics before Chapter 6 Material
1. Keeling Curve
2. How scientists approach Climate
Change
Keeling Curve
+400 ppm
Keeling Curve
Keeling Curve
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Shows atm. CO2 rising at unprecedented rates
Driven by burning of fossil fuels past 200 yrs.
Pioneered in 1958 by scientist Charles Keeling.
Longest-running tally of carbon dioxide levels in atm.
Maintained by Scripps Institution of Oceanography.
Up 22 points from a decade ago.
 Many scientists have warned that carbon dioxide
readings must be brought down to 350 ppm to
avoid severe climate impacts and stall "feedback
loops" that will exacerbate the rise.
Keeling Curve
 Previous 800,000 years, CO2 levels never exceeded 300 ppm
 There is no known geologic period in which rates of increase
have been so sharp.
 Was about 280 ppm at the advent of Industrial Revolution
 “I wish it weren't true, but it looks like the world is going to
blow through the 400-ppm level without losing a beat," said
Scripps geochemist Ralph Keeling, who has taken over the
Keeling curve measurements from his late father. "At this
pace we'll hit 450 ppm within a few decades."
Large body of evidence supports
conclusion that human activity is primary
driver of recent warming.
1. Our understanding of how gh gases trap heat,
how climate system responds to increases, and
how other human and natural factors influence
climate.
2. Many indirect estimates of climate changes over
the last 1,000 to 2,000 years. Ice cores, tree rings
and corals - show recent T rise is unusual
Large body of evidence…
3. Comparisons of actual climate with computer
models. When models are run with historical inc. in
gh gases show gradual warming of Earth, increases
in ocean heat content, rise in sea level, retreat of sea
ice and snow cover. In agreement with observations.
Climate Model Indications & the Observed Climate
 Global climate models clearly show effect
of human-induced changes on global T.
 blue band shows how global T would have
changed due to natural forces only .
 pink band shows model projections of effects
of human and natural forces combined.
 black line shows actual observed global
average temperatures.
 Global climate models clearly show effect
of human-induced changes on global T.
 Close match between black line and the
pink band indicates that observed warming
over last half-century cannot be explained
by natural factors alone, and is instead
caused primarily by human factors.
800,000 Year Record of CO2 Concentrations
Measured from
trapped air bubbles in
Antarctic ice core
Energy from the Sun Has Not Increased
Solar energy
has been
measured by
satellites
since 1978.
Now, Chapter 6
 Our layer model to date assumes that
that surface temperature is the same
everywhere on Earth!
 But, we know this is not true.
 So, we have to add yet more complexity
to our climate change model!
1. Daily & Seasonal cycles - drive surface
temperatures above and below average
values.
2. Energy budgets DO NOT balance locally.
– net heat input at low latitudes, transport
to high latitudes.
 turbulent flows of air and water.
 requires complex computer climate models.
Daily Variability:
Simplified Surface Energy Balance
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NET R =
+SW (insolation)
–SW (reflection)
+LW (infrared)
–LW (infrared)
Figure 6.2
Radiation Budgets
El Mirage, CA
Pitt Meadows, BC
Seasonal Variability
Earth’s tilt is responsible for seasons.
Earth’s tilt determines how much heat the surface
receives from the Sun each day as a function of latitude
(y axis) and time of year (x axis).
net heat input at low latitudes, transport to
high latitudes
Global Latent Heat
Figure 4.19
Global Sensible Heat
Figure 4.20
So we have to simulate the weather.
 In order to forecast global warming we have to
simulate the time and space variations and
imbalances in the energy budget.
 And the way the Earth’s climate responds by
storing or transporting heat around.
 Our original layer model can’t do this.
 Physics that simulate flows of air/water is
complex and difficult to simulate.
Global Circulation without Rotation
Coriolis effect - an inertial
force described by 19thcentury French engineermathematician GustaveGaspard Coriolis in 1835.
Effect is an apparent
deflection of the path of an
object that moves within a
rotating coordinate system.
The object does not actually
deviate from its path, but it
appears to do so because of
the motion of the coordinate
system.
Global Circulation With Rotation
With
Coriolis
Effect
1. Energy Budget of the Earth fluctuates on daily
& seasonal timescales (in contrast to the layer
model).
2. Annual Energy Budget doesn’t balance locally
because excess heat is carried to higher
latitudes by winds and ocean currents.
3. Global warming forecast requires
simulation the weather – computational
challenge.