Memorandum for the Petitioners \ 40
5.31. Extreme event attribution can assess the increased likelihood of
a specific extreme weather event occurring. Attribution studies for cyclones,
including typhoons and hurricanes, link additional flooding from rising sea
levels to human-induced climate change, as well as how warmer ocean
temperatures sustain and intensify a hurricane and assess increases in the
precipitation.135 Tropical storms have also been the subject of extreme event
attribution studies. Studies attempt to determine whether human GHGs have
made an extreme event more intense (i.e., caused more rainfall or made
temperatures hotter), or more likely to occur { i.e., increased the chance or
likelihood of the extreme event ).136
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5.32. The results are expressed probabilistically in the same way that
risk factors in health are measured because, in theory, any extreme event is
possible in the counterfactual world. Scientists have, therefore, said that it is
not possible to give a simple yes or no answer to the question of whether a
particular event was caused by climate change; rather, what can be measured
is how global wanning made the event more intense, or more likely to occur.
This methodology, however, does not imply that there is no relationship
between cause and effect; it simply expresses the relationship in a
statistical form .137
5.33. In the case of super typhoon Haiyan, as stated in the Joint
Summary of the Amicus Curiae:
The ocean heat content (OHC) and sea level in the
region had increased a great deal since 1993 and especially
since 1998. Consequently, as the typhoon approached the
Philippines, it was riding on very high sea surface
temperatures (SSTs) with very deep support through the high
OHC, and the strong winds and ocean mixing did not cause
as much cooling as would normally be experienced, probably
helping the storm to maintain its tremendous strength.
Moreover, the storm surge was without a doubt exacerbated
considerably by the sea levels, which were some 30 cm
above 1993 values. Although natural variability played a
major role, there was also a global component through
increased OHC from the Earth’s energy imbalance. 138
(Emphasis supplied)
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5.34. As explained by amicus expert Dr. Kevin Trenberth,
Distinguished Senior Scientist at the National Center for Atmospheric
Research, “ the changes in extremes have huge impacts on society and on
ecosystems and the environment ( . . . . ) In one sense, the extreme event
135
3.
136
See Exhibit “EEEEEEE” to “EEEEEEE-3,” Statement of Brenda Etavnrzel, dated 20 September 2018, p.
See Exhibit “ DDDDDD” to “DDDDDD- 15,” Statement of Sophie Marjanac, dated 03 August 2018, pp.
4-5, par. 14, ( in -text citations omitted ).
137
Ibid., pp. 5-6, para. 17 ( in-text citations omitted ).
138
Joint Summary of the Amicus Curiae, supra note 50, p. 38 (in-text citations omitted).
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