Lomborg-errors: "Cool it!"

Water shortages
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  Comments to pages 148 - 157 in Cool it.


    A main issue of this paragraph is the effect of global warming on the number of people living under water stress. Nearly all climate computer models project increased precipitation in the future, because global warming will lead to evaporation of more water, which then will rain down again somewhere on the globe. The crucial question is: Where will the extra rain fall - will it fall e.g. over the sea or in land areas with dense populations that can prosper from the rain?
    One may consult the latest IPCC report (2007), WG II, and read on this subject in its section 3.5.1. That section presents two forecasts of the projected number of people that will live under water stress. One is produced by Arnell et al. (2004), and is cited by Lomborg. The other is produced by Alcamo et al. (2007) and is not cited by Lomborg, even though it was published before Lomborg finished his work on the water shortage chapter (cf. his note 812). The reference is: J. Alcamo et al. (2007): Hydrological Sciences Journal 52(2): 247-275.
The IPCC report presents estimates from the two papers. Alcamo et al. predict much higher numbers of people under water stress than do Arnell et al. This is so for the number of people under water stress in the 2050s, but the same is true when looking further into the future (Alcamo: 2070s, Arnell: 2080s).
    In Lomborg´s book, Figure 45 on page 153 presents the results from Arnell et al. for the 2080s. We see that no matter what climate scenario we choose, global warming will mean that fewer people live under water stress. Thus, concerning water supplies, global warming will have a net positive effect in all cases. But this is so only with the projections of Arnell et al. The projections of Alcamo et al. (for the 2070s) is that the A2 column with global warming should be at 7.97 billions, with a rising trend, and the B2 column with global warming should be at 5.03 billions, with a slightly rising trend. Thus for those scenarios investigated by Alcamo et al., global warming will mean more people under water stress.
The explanation why the Arnell et al. study leads to fewer water-stressed people is evident from Lomborg´s figure 46. Here "South Asia" stands out. The reason is that all models show greatly increased precipitation in northern India and easternmost Pakistan. Some models - but not all - also show increased precipitation in southern India. What figure 46 shows is that the extra precipitation in India and Pakistand lifts more than 1 billion people out of water stress. That is a lot - it is nearly all inhabitants of the Indian subcontinent. In contrast, Alcamo et al. project that although there will be a greatly increased precipitation in north India, this will not be sufficient to lift the inhabitants out of water stress. Here, the same definition of water stress is applied in both cases, viz. less than 1,000 m³ per person per year.
    How come that the two studies lead to different results? It is not because of different estimates of population growth - both studies use the same IPCC scenarios regarding population growth.
    The study of Arnell et al. has some shortcomings. For instance, it does not include changes in glacier melt, and it does not clearly indicate the seasonality of the precipitation. The study of Alcamo et al. also has some shortcomings, but seems more advanced in some respects. Thus, it includes the effect of rising temperatures on evapotranspiration - i.e., when it is warmer, crops use more water, and therefore need more irrigation, and it is more specific concerning water use efficiency.
    Some important caveats should be mentioned. Arnell et al. have this imprtant caveat (p. 50): ". . the increases in runoff generally occur during high flow seasons, and may not alleviate dry season problems if this estra water is not stored: the extra water may lead to increased flooding, rather than reduced water resources stress." Alcamo et al. are more specific on this point. They state clearly that the extra precipitation in north India will fall in the rainy season - i.e. when it rains, it will rain more heavily than before. Not only will average rainfall increase, there will also be an increase in extremely strong and damaging rain showers, especially in western India. This will lead to more frequent events like the flooding in Mumbai in 2005, and to more floodings of river valleys like the huge floodings in Pakistan in 2010. Also, Nohara et al. (2006), cited by Lomborg, show that all extra river flow in the Ganges will be in the already wet season. According to that study, total river flow at the end of the 21st century will increase by about 18 % - that is not very much relative to population growth during the century.
    Remember that during the latter half of the 21st century, Himalayan glaciers will be much reduced, and give less water flow in the large rivers during the dry season (see Lomborg-errors on glaciers here). As stated above, this effect is not included in the study by Arnell et al. So the situation in north India will be that there will be less water than before in the dry season, and more water than before in the wet season. It will require a very large effort to build sufficiently large water reservoirs to have sufficient water all year round. These reservoirs will have to be very strongly built and extremely large if they shall prevent floodings due to catastrophic rain events.
    Arnell et al. remember to mention the caveat that although there will be much more water for the many people in north India, this may possibly be a curse rather than a blessing, with crops being destroyed by floods. Lomborg, on the other hand, forgets to mention this caveat. He also forgets to mention that some of the models in Arnell et al. indicate reduced rainfall in south India, and he especially forgets to mention that there are two studies - one indicating a net advantage overall, and the other indicating a net disadvantage overall. He only mentions the former.
   There exists a later article by Arnell (pp. 167-175 in a book which Lomborg has seen, viz. H. J. Schellnhuber et al. (2006): Avoiding dangerous climate change. This article mainly repeats data from Arnell´s 2004 paper. However, it has an important comment on p. 171: "It also appears from Figure 17.5 that some watersheds would see a decrease in water stress due to climate change, because river flows increase with climate change. However, increasing river flows does not necessarily mean that water-related problems would reduce, because in most cases these higher flows occur during the high flow season. The risk of flooding would therefore increase, and without extra reservoir storage or changes to operating rules water would not be available during the dry season. It is therefore not appropriate to calculate the net effect of apparaent decreases and increases in water stress." The meaning of this text has becomes more clear today when we have seen the consequences of the floodings in Pakistan in 2010. Unfortunately, it seems up to now that the Pakistanian society is unable to utilize the increased water flow by investments in infrastructure (reservoirs etc.). As long as this is the case, some of the `improvements´ referred to by Lomborg may unfortunately be catastrophes to the people that are affected by them.


Page 149 and Figure 43: " However, this still only constitutes about 17% of the available water."
The lay reader will think that if we use only 17 % of what is available, there is still 83% waiting to be used. This is not so, however. One cannot use 100 % of what is "available", at lest not on a long term. Actually, as may be read in Alcamo et al (2007) (reference, see above), when people use more than 40 % of what is "available", this is designated as "severe water stress". Withdrawal of 20 - 40 % of what is "available" is called "medium water stress". Thus, the situation now (2010) is a global overall situation bordering at "medium water stress".

Page 152: " . . .but this ignores that increased economic ability will probably more than compensate for the lower amount of water available. "
This is contradicted by Lomborg´s own text. In the legend to figure 45 (note 821) we read that the number of people living under water stress in 1995 was 1.368 billion. This is lower than even the most optimistic scenario for the year 2085 in that figure.

Page 152, note 817: " . . .but this ignores that increased economic ability will probably more than compensate for the lower amount of water available.817. "
Lomborg´s reference, Cairncross (2003), does not say that. It speaks of the irony that international agancy officials from Europe and North America are so enthusiastic for private enterprise and market mechanisms, because experience from these now developed countries was that market failures prevented a good service of water supplies, and public intervention was necessary. It is added: "!The South African Government has accepted that while many are willing to pay for water supplies, the poor cannot. Public finance has therefore been employed to end the apartheid in water services."

Page 152 bottom and Figure 45: "What this shows is that global warming actually reduces the number of people living in water stressed watersheds."
As explained above under "Main issue", this presentation is flawed because i relies exclusively on a study that produces a positive trend with global warming, whereas another study which produces a negative trend is ignored by Lomborg. Moreover, Lomborg omits the caveat that the extra precipitation may actually be damaging, because it will fall in the already wet season and may cause catastrophic floods.

Page 155 top and note 825: " . . .for an annual cost from 2007 to 2015 of about $10 billion, or the equivalent of less than $4 billion forever."
Lomborg refers to a study which says that one could supply low-cost water services to all people who are not currently supplied within the period 2007 to 2015 at an annual cost during these years of $10 billion. But then he recalculates this as an expenditure of $4 billion annually forever. This means that a relatively objective measure ($10 billion) is transformed into a measure that is completely dependent on the choice of discount rate (less than $4 billion annually at a subjectively chosen discount rate of 5 % per year). The discount rate used by Lomborg here is differetn from that used in his Copenhagen Consensus conferences, and thus his recalculations do not make the costs comparable to other costs presented by him. Furthermore, it is irrelevant in this context to calculate the amount as an annuity, i.e. a yearly payment every year from now to infinity. The task was to supply water services to everybody no later than 2015. But if most of the payment were deferred to after 2015, and continued into infinity, some of these people would not be served within their lifetime, nor would their children or grandchildren be served. The usual procedure to make expenditures comparable is to calculate the present value, which in this case, at a discount rate of 5 %, is about $80 billion.Lomborg does that in many other cases.