Typos in the 2nd Edition

Typos in Modeling the Environment

Please let me know if you see typographical errors in the book.
Alert readers have spotted the following errors:

Page
Typos (or Extra Explanations for Clarity)

25
extra Fig 2.17 show the interest rate in %/year. If you enter these six values into the graphical function for the interest rate, be sure to divide by 100 when you write the equation for the interest added. The instructions on page 25 suggest setting the graphical function scale to range from 0.00 to 0.08 and to enter the values as a fraction/year, ie, 0.04 for the first two entries, 0.05 for the next two entries, 0.06 for the final two entries.

32
typo The 7th line in the paragraph below Figure 3.2 has a sentence starting with "It we want to match.." It should be "If we want to match.."

67
units The units for water storage in Fig. 6.2 are described as cubic kilometers (ckm).
The units should be thousands of ckm. The flows would be in thousands of ckm/year.

84
typo Exercise 7.7 says Ao = 50, but Ao should = 10 (since the initial area is 10 acres, as explained
on the bottom of page 77).

87
extra The 2nd sentence under the first heading explains that the model is "called the S-I-R model because the affected people move from susceptible to infected to recovered." This can be confusing since I use "affected population" to represent the sum of the infected population and the recovered population. It would have been better to say "the model is called the S-I-R model because people who become sick are moved from susceptible to infected to recovered."

89
typo The 3rd line under Expanding the Model:
6 contacts per day, not 12 contacts per day.

90
extra The final sentence says that the S-shaped pattern persists across the wide range of conditions. The tests are summarized by comparing the "infected population."
To see the S-shaped patterns, use a compartive time graph of the "affected population."

95
an error
of omission Exercise 8.4 calls for a more agressive implementation of "contact avoidance." The contacts per day should be reduced from 6 to 2 after the infected population exceeds 1,000. This policy is more agressive than the 3rd simulation in Fig 8.9 where daily contacts are reduced by 6 to 3 after the infected population exceeds 1,000.
The exercise does not explain how rapidly the nonlinear graph (~) reduces the contacts. The results in Fig 8.9 assume that daily contacts would be reduced from 6 to 3 as the infected population changes from 1,000 to 1,500. To reproduce these results, you would ask for the horizontal axis in the nonlinear graph (~) to allow data entries at 500, 1000, 1,500 and 2,000. The same horizontal axis design can be used in exercise 8.4.

105
typo In the 3rd line under Creating Causal Loop Diagrams from Flow Diagrams,
(see table 1.2) not table 2.1

115
extra Exercise 9.17 asks for a causal loop diagram of the model in Fig 6.2. You are told to expect three positive feedback loops. Previous readers have followed the advice on page 106 -- they start with words and arrows for all the stocks and all the flows. They know from page 106 that no feedbacks will be in view at this early stage of the diagram. The next step is to add arrows to explain the flows. But Fig. 6.2 does not show the variables and the connections to explain the flows. (It simply gives numerical values of the flows.)
For the causal loop diagram to reveal the positive feedback loops, innovative readers think of a few additional variables and connections to add to Fig. 6.2. For example, some add an "evapotranspiration rate" to explain the "evapotranspiration" and an "over land precipitation rate" to explain "precipitation over land." Then one can expand the causal loop diagram, and a positive feedback loop will come into view. Adding similar rates to the oceanic side of the diagram will cause another positive feedback loop to come into view. Adding new rates to explain the "net transport to land" and the "river flow to oceans" will allow the third positive feedback to come into view. These loops describe the cycling of water through various stages of the global hydrologic cycle (similar to the cycling loops in exercises 9.15 and 9.16.)

134
image The image in Fig 11.9 is incorrect. Click here to see the correct image and an explanation.

135
typo Exercise 11.11 says your simulations should show the temperatures matching Fig 11.5 and the areas matching Fig. 11.6 The temperature results should match the results in Figs. 11.7.
The area results should match the results in Fig. 11.8.

136
typo Similar typos appear in exercise 11.12 at the top of page 136. The temperature results should match the temperatures at the low end of Fig. 11.7 (not Fig. 11.5). And the area results should match the areas at the low end of Fig. 11.8 (not Fig. 11.6).

204
typo Exercise 15.9, third line: "you situation" should be changed to "your situation"

206
extra Exercise 15.16, 10th line down: carrying capacity will be 232.5 thousand (not 233 thousand). 13th line down: "nearly all of the 50 miles are in the mature, restored status"
15th line down: "should be nearly 415 thousand at the end of this test."

216
typo The first coefficient on the Emission fraction in Table 16.5 is -2.080. The coefficient should be -3.080, the value shown in Table 16.4 and in the list of equations for Table 16.3.

221
typo Exercise 16.11, second line: "both the EV and the EV" should be changed to
"both the CV and the EV"

239
typo first line: "use first-order smoothing with a 2-year lag time" (not a 1-year lag time)

245
typo In the 6th line from the top: "business system" should be changed to "business systems"

248, 249,
251
typo The rent and the levelized cost for commerical real estate are said to be measured in $ per square foot per month. The correct units are $ per square foot per year. This error in explaining the units does not change the simulation results because these units cancel when the forecasted rent is divided by the levelized cost to get the forecasted profitability fraction.

275,
276
extra The feedback loop symbol in Vensim can point in the clockwise or the counter clockwise direction. It's best to select the direction to match the path around the loop (as in Figs 21.3 and 21.5). But I should have been more carefull in the next two diagrams: Fig 21.7: biodecay loop symbol should be clockwise
Fig 21.9: both of the biomass control loops should be in the counter clockwise direction

279
typo On the left edge of the Vensim diagram in Fig. 21.15, replace the variable "fr of new biomass within reach" with the "fr of added forage req consumed." This variable is then connected to the "equivalent fr of forage needs met." This typo is also explained in the information buttons in the Vensim and Stella models posted to the "Selected Models" page of the Instructors' Section of the book's website.

281, 282
typo The 2nd line from bottom of page 281 should read "from 40% to 95% (not from 55% to 90%).
The 55% result in Fig. 21.19 should be labeled as the 40% result.

301
delete DELETE the words "embedded in the clathrate sediments" (9 lines from the bottom of the page.) The methane under discussion in this paragraph is embedded in the permafrost, not in clathrate sediments. (The "clathrates" are methane hydrates, icelike substances found in the muck of seabeds around the world. They are kept solid only by the pressure and cold of the overlying water. Like the methane in the permafrost, these "clathrates" can be released to the atmosphere during a period of rapid warming (see p. 125 of Spencer Weart's 2008 edition of The Discovery of Global Warming.)

309
typo Two of the variables in Fig. 24.2 are spelled incorrectly. The correct spellings are:
forecasted need for capacity and construction completions.

319
typo 3rd line under Automatic or Manual Checking?: If we have used friendly algebra, the units will be easy to check. (The word "be" was missing.)

321
typo The variable "H" (2nd from bottom) in Table A.1 is misnamed; it should be "T"

Page	Typos (or Extra Explanations for Clarity)
25 extra	Fig 2.17 show the interest rate in %/year. If you enter these six values into the graphical function for the interest rate, be sure to divide by 100 when you write the equation for the interest added. The instructions on page 25 suggest setting the graphical function scale to range from 0.00 to 0.08 and to enter the values as a fraction/year, ie, 0.04 for the first two entries, 0.05 for the next two entries, 0.06 for the final two entries.
32 typo	The 7th line in the paragraph below Figure 3.2 has a sentence starting with "It we want to match.." It should be "If we want to match.."
67 units	The units for water storage in Fig. 6.2 are described as cubic kilometers (ckm). The units should be thousands of ckm. The flows would be in thousands of ckm/year.
84 typo	Exercise 7.7 says Ao = 50, but Ao should = 10 (since the initial area is 10 acres, as explained on the bottom of page 77).
87 extra	The 2nd sentence under the first heading explains that the model is "called the S-I-R model because the affected people move from susceptible to infected to recovered." This can be confusing since I use "affected population" to represent the sum of the infected population and the recovered population. It would have been better to say "the model is called the S-I-R model because people who become sick are moved from susceptible to infected to recovered."
89 typo	The 3rd line under Expanding the Model: 6 contacts per day, not 12 contacts per day.
90 extra	The final sentence says that the S-shaped pattern persists across the wide range of conditions. The tests are summarized by comparing the "infected population." To see the S-shaped patterns, use a compartive time graph of the "affected population."
95 an error of omission	Exercise 8.4 calls for a more agressive implementation of "contact avoidance." The contacts per day should be reduced from 6 to 2 after the infected population exceeds 1,000. This policy is more agressive than the 3rd simulation in Fig 8.9 where daily contacts are reduced by 6 to 3 after the infected population exceeds 1,000. The exercise does not explain how rapidly the nonlinear graph (~) reduces the contacts. The results in Fig 8.9 assume that daily contacts would be reduced from 6 to 3 as the infected population changes from 1,000 to 1,500. To reproduce these results, you would ask for the horizontal axis in the nonlinear graph (~) to allow data entries at 500, 1000, 1,500 and 2,000. The same horizontal axis design can be used in exercise 8.4.
105 typo	In the 3rd line under Creating Causal Loop Diagrams from Flow Diagrams, (see table 1.2) not table 2.1
115 extra	Exercise 9.17 asks for a causal loop diagram of the model in Fig 6.2. You are told to expect three positive feedback loops. Previous readers have followed the advice on page 106 -- they start with words and arrows for all the stocks and all the flows. They know from page 106 that no feedbacks will be in view at this early stage of the diagram. The next step is to add arrows to explain the flows. But Fig. 6.2 does not show the variables and the connections to explain the flows. (It simply gives numerical values of the flows.) For the causal loop diagram to reveal the positive feedback loops, innovative readers think of a few additional variables and connections to add to Fig. 6.2. For example, some add an "evapotranspiration rate" to explain the "evapotranspiration" and an "over land precipitation rate" to explain "precipitation over land." Then one can expand the causal loop diagram, and a positive feedback loop will come into view. Adding similar rates to the oceanic side of the diagram will cause another positive feedback loop to come into view. Adding new rates to explain the "net transport to land" and the "river flow to oceans" will allow the third positive feedback to come into view. These loops describe the cycling of water through various stages of the global hydrologic cycle (similar to the cycling loops in exercises 9.15 and 9.16.)
134 image	The image in Fig 11.9 is incorrect. Click here to see the correct image and an explanation.
135 typo	Exercise 11.11 says your simulations should show the temperatures matching Fig 11.5 and the areas matching Fig. 11.6 The temperature results should match the results in Figs. 11.7. The area results should match the results in Fig. 11.8.
136 typo	Similar typos appear in exercise 11.12 at the top of page 136. The temperature results should match the temperatures at the low end of Fig. 11.7 (not Fig. 11.5). And the area results should match the areas at the low end of Fig. 11.8 (not Fig. 11.6).
204 typo	Exercise 15.9, third line: "you situation" should be changed to "your situation"
206 extra	Exercise 15.16, 10th line down: carrying capacity will be 232.5 thousand (not 233 thousand). 13th line down: "nearly all of the 50 miles are in the mature, restored status" 15th line down: "should be nearly 415 thousand at the end of this test."
216 typo	The first coefficient on the Emission fraction in Table 16.5 is -2.080. The coefficient should be -3.080, the value shown in Table 16.4 and in the list of equations for Table 16.3.
221 typo	Exercise 16.11, second line: "both the EV and the EV" should be changed to "both the CV and the EV"
239 typo	first line: "use first-order smoothing with a 2-year lag time" (not a 1-year lag time)
245 typo	In the 6th line from the top: "business system" should be changed to "business systems"
248, 249, 251 typo	The rent and the levelized cost for commerical real estate are said to be measured in $ per square foot per month. The correct units are $ per square foot per year. This error in explaining the units does not change the simulation results because these units cancel when the forecasted rent is divided by the levelized cost to get the forecasted profitability fraction.
275, 276 extra	The feedback loop symbol in Vensim can point in the clockwise or the counter clockwise direction. It's best to select the direction to match the path around the loop (as in Figs 21.3 and 21.5). But I should have been more carefull in the next two diagrams: Fig 21.7: biodecay loop symbol should be clockwise Fig 21.9: both of the biomass control loops should be in the counter clockwise direction
279 typo	On the left edge of the Vensim diagram in Fig. 21.15, replace the variable "fr of new biomass within reach" with the "fr of added forage req consumed." This variable is then connected to the "equivalent fr of forage needs met." This typo is also explained in the information buttons in the Vensim and Stella models posted to the "Selected Models" page of the Instructors' Section of the book's website.
281, 282 typo	The 2nd line from bottom of page 281 should read "from 40% to 95% (not from 55% to 90%). The 55% result in Fig. 21.19 should be labeled as the 40% result.
301 delete	DELETE the words "embedded in the clathrate sediments" (9 lines from the bottom of the page.) The methane under discussion in this paragraph is embedded in the permafrost, not in clathrate sediments. (The "clathrates" are methane hydrates, icelike substances found in the muck of seabeds around the world. They are kept solid only by the pressure and cold of the overlying water. Like the methane in the permafrost, these "clathrates" can be released to the atmosphere during a period of rapid warming (see p. 125 of Spencer Weart's 2008 edition of The Discovery of Global Warming.)
309 typo	Two of the variables in Fig. 24.2 are spelled incorrectly. The correct spellings are: forecasted need for capacity and construction completions.
319 typo	3rd line under Automatic or Manual Checking?: If we have used friendly algebra, the units will be easy to check. (The word "be" was missing.)
321 typo	The variable "H" (2nd from bottom) in Table A.1 is misnamed; it should be "T"