Energy and Human Ambitions on a Finite Planet, 2021a

9 Climate Change 160
skeptic” who names many natural sources of CO 2 <strong>and</strong> says we
should not be too quick to label the CO 2 rise as anthropogenic? 79
79: ...ofhuman origin
11. What letter grade would you give to the performance of the red
curve in Figure 9.4 for its faithful tracking of the measured CO 2
blue curve? Describe reasons why you might deduct any points.
12. The allocation of CO 2 emissions among countries in Figure 9.5
differs pretty markedly from the distribution in Table 9.3. What
does this tell us about past <strong>and</strong> present activity among countries?
13. Use a modified version of Eq. 9.2 to compute what the earth’s
80: . . . i.e., dark <strong>and</strong> no bright clouds/snow
temperature would be if it had no greenhouse gases <strong>and</strong> absorbed
100% of incident solar energy. 80 81: Hint: the fourth root can be obtained by
Is this warmer or cooler than
taking two square roots one after the other,
the actual average surface temperature (given GHG <strong>and</strong> ∼30% or raising to the 0.25 power using the y x
reflection)? 81
button.
14. Based on Figures 9.7 <strong>and</strong> 9.8, is the atmosphere transparent or
opaque at a wavelength of 1.0 μm? What about at 6 μm? And how
would you characterize the situation at 2 μm?
15. If enough ice on Earth melted <strong>and</strong> resulted in 25% reflectance
instead of 29.3%, what would the equilibrium temperature become,
still applying the nominal 33 K GHG contribution? How much
temperature rise is this compared to the equilibrium temperature
at 29.3% reflection?
16. Table 9.4 has H 2 O as the leading greenhouse gas, <strong>and</strong> all of them
adding to 33 ◦ C of warming effect on Earth. Should it be our goal
to reduce all of these effects to the lowest numbers possible? 82
Why or why not? How would you characterize the greenhouse
effect <strong>and</strong> why it is of concern to us?
17. Treating Figure 9.9 somewhat literally, in which one out of every
four infrared photons escapes without being absorbed by a greenhouse
gas molecule, what would the effective upward radiation
be if 400 W/m 2 left the ground, <strong>and</strong> re-radiation of the absorbed
fraction was split equally between upward radiation <strong>and</strong> radiation
returning to the ground? 83
82: For instance, if we could cut them all in
half, would that be good?
83: Hint: Figure 9.15 offers clues.
18. If the “bad” news that we are about halfway through the fossil fuels
is wrong, <strong>and</strong> we are only one-quarter of the way through, <strong>and</strong> we
end up using all of it, what would the ultimate CO 2 concentration
be in ppm v , extrapolating the increase so far? How many degrees
would this turn into based on our underst<strong>and</strong>ing of radiative
forcing <strong>and</strong> the climate sensitivity parameter?
19. Using Eq. 9.5 <strong>and</strong> CO 2,orig 280 ppm v , together with a climate
sensitivity parameter of 0.8 ◦ C per W/m 2 , how much would you
predict Earth’s temperature to rise for CO 2 levels of 330, 380, 430, 84: A table would make sense, including
480, 530, <strong>and</strong> 580 ppm v ? 84 The inputs increase by steps of 50 the radiative forcing as one column.
© 2021 T. W. Murphy, Jr.; Creative Commons Attribution-NonCommercial 4.0 International Lic.;
Freely available at: https://escholarship.org/uc/energy_ambitions.