The Impact of Climate Change on Natural Disasters - Reducing Disaster: Early Warning Systems for Climate Change - page 34

weaker storms. Long-term planning under projected warming scenarios should then
account for these potential increases in severe tropical cyclones, as well as a likely
increase in rainfall rates and associated coastal and inland fresh-water fl ooding.
Based on idealized numerical simulations, Knutson and Tuleya ( 2004 ) suggested
that increases in tropical cyclone intensity forced by CO 2 -induced tropical warming
would not be clearly detectable for multiple decades. However, as discussed above,
regional forcing by particulate pollution can bring about more rapid changes. Thus,
numerical projections based on future scenarios are highly dependent on projections
of both CO 2 concentrations and particulate concentrations, particularly on decadal
time-scales. But there is greater uncertainty in projections of particulate pollution
than CO 2 (e.g., Forster et al. 2007 ; Haerter et al. 2009 ). At present, regional projec-
tions of tropical cyclone activity on time-scales relevant to EWS design remain
somewhat uncertain, but this is an area of active research.

2.3 Event Attribution

The SREX (IPCC 2012a , b ) confi rms that extreme events have been and are pro-
jected to be on the rise. Major extreme event databases and insurance companies'
numbers corroborate this (EM-DAT 2011 ; Munich 2012 ). There is also increasing
scientifi c evidence that the changing likelihood of extreme events is linked to
human-induced climate change (IPCC 2012a ). The working group I of the IPCC
fi fth Assessment Report ( 2013 ) concludes that the probability of heat waves in some
areas has more than doubled due to human infl uence.
In the aftermath of major disasters, scientists are usually confronted with the ques-
tion of whether individual extreme events (i.e., fl oods and hurricanes) can be attributed
to climate change. There is disagreement among climate scientists about the proper
response to such inquiries. In the past, climate scientists were generally cautious linking
a single extreme event to climate change because of the statistical difference between
weather and the long-term averaged climate and would only conclude that climate
change increases the possibility for extreme events to occur. Recently, however, the idea
of event attribution has become more realistic, although the possible outcomes of event
attribution studies are still limited to statistical probabilities. This section explains the
science of event attribution and its challenges. It also raises the question of liability in
general: Does event attribution bolster the case of lawsuits and damage claims?

2.3.1 What Is Event Attribution?

Event attribution tries to understand and quantify the human and natural infl uences
on individual extreme events (such as a drought or fl ood events) (Stott et al. 2011 ).
In general, it tries to answer the following question:
Is a particular extreme event more or less likely with or without human infl uence
on the climate?