Background
The authors write that "the variability of TC [tropical cyclone] activity (including the frequency of occurrence and intensity) has become a great concern because it may be affected by global warming," and it is this hypothesis that provides the impetus for their study.

What was done
Kubota and Chan created a unique dataset of TLP (tropical cyclone landfall numbers in the Philippines) based on historical observations of TC tracks during the period 1901-1940 that were obtained from Monthly Bulletins of the Philippine Weather Bureau and combined with TLP data obtained from the Joint Typhoon Warning Center for the period 1945-2005, which they then used to investigate the TC-global warming hypothesis.

What was learned
The two Asian researchers report that "the TLP has an apparent oscillation of about 32 years before 1939 and an oscillation of about 10-22 years after 1945," but that "no long-term trend is found." In addition, they determined that "natural variability related to ENSO [El Niņo-Southern Oscillation] and PDO [Pacific Decadal Oscillation] phases appears to prevail in the interdecadal variability of TLP."

What it means
In response to what climate alarmists call the unprecedented global warming of the 20th century -- and about which they express the gravest concern -- the number of tropical cyclones annually making landfall in the Philippines did not experience any net change. All variability was merely oscillatory activity around a mean trend of zero slope.