Comments to pages 148 - 157 in Cool it.
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
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
The explanation why the Arnell et al. study leads to fewer
water-stressed people is evident from Lomborg´s figure 46. Here
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
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
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
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.
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".
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
(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.
152, note 817: " . . .but this ignores that increased economic ability
probably more than compensate for the lower amount of water
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."
152 bottom and Figure 45: "What this shows is that global warming
actually reduces the number of people living in water stressed
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
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.