conditions is not always easy. The strong drought of 2007 described above, happened unexpectedly
in a very strong LN year (Yumul et al., 2010), which even exacerbated the devastation of the event.
Lyon et al. (2006) analyzed this connection between rainfall and ENSO by looking at rainfall data from
40 observing stations across the Philippines and showed that the seasonal rainfall response to ENSO
reverses between boreal summer (July–September) and fall (October–December) for both El Niño
and La Niña. On a seasonal basis, Villafuerte II et al. (2014b) found in another publication that ENSO
is correlated to the precipitation in OND (October to December) in the way that El Niño leads to
dryer and La Niña to wetter conditions. In contrast, the season JAS is more influenced by the
monsoonal activity, in particular in the western part of the country.
The trends in extreme heat events, e.g. in hot days and warm nights, have been analyzed by Manton
et al. (2001), who showed significant increases and further a decrease in cool days and cold nights in
the period 1961 to 1998.
Projected changes of the EWEs
To analyze the future changes in drought occurrence, Dai (2012) used global models, but could not
find clear significant results for SEA. In contrast to that, Taylor et al. (2012) found a consistent
increase in drought risk in a global assessment, which he indicates with the Palmer Drought Index
(PDSI). Sillmann et al. (2013) showed that heavy precipitation events in SEA will increase in
magnitude and frequency in the future. The share of heavy precipitation on the total amount of
precipitation could increase to more than 50% in RCP8.5. They also found signs for a stronger
drought risk as they showed that the maximum number of consecutive dry days is increasing.
Looking at the superregional level of SEA, the strongest increases for frequency and intensity of
temperature extremes are found to be in Indonesia and southern Philippines by the World Bank
(2013). Sillmann et al. (2013) found similar results and further argued that SEA is one of the two
regions in the world that face strong increases in heat extremes even under a low-emissions
scenario. In the RCP8.5 scenario, today’s warm spells (above the 90th percentile of the base time
period) would occur at most times of the year (~300 days) and today’s warm nights (above the 90th
percentile of the base time period) would occur in 95% of all nights in the future (Sillmann et al.,
2013)
For the projected changes in TCs, one has to look separately for the frequency and the intensity of
the storm events. As the World Bank (2013a) stated, there are no studies dealing with projections for
a temperature change of only 2°C – so they all analyze future projections of TCs for a 4°c warmer
world (RCP8.5). Atmospheric model results show an overall decrease in frequency in the area of the
Philippines – with some exceptions (Sugi et al., 2009; Knutson et al., 2010; Held and Zhao, 2011;
Murakami et al., 2012). Sugi et al. (2009) used a mesh AGCM (Atmospheric General Circulation
Model) and showed also robust decreases in global TC frequency due to climate change. However,
they stated that the regional characteristics can be different as they depend strongly on the SST
projections used.
Other working groups (Caron and Jones, 2007; Emanual et al., 2008) analyzed the likelihood of a TC
to develop – which is called cyclogenesis and can be used as an indicator for frequency (World Bank,
2013a) – and found increasing trends. In contradiction, Zhao and Held (2011) proved that the
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