London scoping - ukcip

Final Report
130
2050s (DoH 2002). Although winter precipitation is predicted to rise by around 10-20% in the
London area, snowfall is expected to decrease by between 60% (Low Emissions scenario) and
about 95% (High Emissions scenario) by the 2080s, indicative of far less frequent wintry spells.
Effects on humidity and related health effects are less certain. External relative humidity falls
by 2-3% percent in winter under all scenarios and timescales, but absolute humidity rises since
warmer air can hold more water. Since absolute humidity determines internal relative humidity
in heated buildings, internal relative humidity could rise slightly. This, combined with higher
internal temperatures, could increase asthma, since both tend to increase asthma rates.
However, there will probably be less internal condensation and mould growth, because internal
surfaces on external walls and windows will be less cold and this is likely to be a stronger effect
than the slight rise in absolute humidity, with small beneficial effects on health. Predictions for
wind remain very uncertain; wind speeds are expected to stay about the same, possibly
increasingly slightly in winter, but the effects on infiltration rates and hence internal humidity
are likely to be commensurately small.
Hotter Summers
Projected climate change will be accompanied by an increase in hot spells, often exacerbated by
urban air pollution on still, hot days, which would cause an increase in heat related deaths and
illness episodes (see Section 5.3). The evidence indicates that the impact would be greatest in
urban populations, affecting particularly the elderly, sick and those without access to air
conditioning. The Department of Health’s recent review of the impacts of climate change
suggests that approximately 2000 extra deaths might result from higher summer temperatures in
the UK as a whole (DoH 2002).
Populations do, however, adapt to continued higher temperatures through behavioural change
and through autonomous physiological change. For this reason, populations are most often
vulnerable to unusually hot or cold weather, relative to what they are acclimatised to, rather than
hot or cold per se. Studies have shown, for instance, that the people of Athens suffer more from
a cold weather spell than people in Stockholm do to an equivalent cold spell. On the other hand,
the residents of Stockholm are more affected by a heat wave than those in Athens (Martens
1996, Gawith et al. 1999). If climate change results in greater variability and more extreme
events, then populations will, conceivably, become more vulnerable. Whether populations
adjust to a more variable pattern of weather from month to month, or from year to year, is an
interesting question. Adjustment to a certain level of variability is feasible, though thresholds
may occur in the adaptive capacity. A further impact of hotter weather is the greater risk of skin
cancer, especially for children who not only spend more time outside but are also the most
vulnerable. The Department of Health (DoH) suggests that 30,000 additional cases of skin
cancer could occur across the UK if ozone-depleting chemicals are emitted at current levels,
though full implementation of the Copenhagen Amendment would reduce this number to 5000
(DoH 2002). The DoH review stresses that the additional number of cases of skin cancer
depends greatly upon adjustments, such as use of sun creams, avoidance and wearing of widebrimmed
hats, and so on. An increase of up to 2000 more eye cataracts a year is also
anticipated by the DoH review.
The outbreak of Legionnaire’s disease in Barrow-in-Furness in August 2002 is widely expected
to have been related to a faulty or poorly maintained air conditioning unit. As of early August,
one man had died from the outbreak, whilst 117 people have been identified as having been
infected. This highlights the potential risk that more widespread use of air conditioning could
increase the incidence of Legionnaire’s, if units are not correctly operated and maintained. In