"Climate Change and Southern Hemisphere Tropical Cyclones" International Initiative – Progress since the First International Conference on Indian Ocean Tropical Cyclones and Climate Change - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 28

borders. Analyses have been undertaken to understand the variability and change
in TCs across the SH, with a view to providing a better scientific basis for
understanding the current risks posed by TCs, and possible changes as a result
of climate change.
Since the First International Conference on Indian Ocean Tropical Cyclones
and Climate Change, considerable progress has been achieved in developing a
web-based information tool to visualise and analyse historical cyclone data,
further understanding spatial and temporal variability in TC activity due to El
Niño-Southern Oscillation, estimating long-term cyclone trends in the South
Indian and the South Pacific Oceans, and seasonal prediction of cyclone activity.
In this paper, some of the important achievements of the “Climate change and
Southern Hemisphere tropical cyclone” International Initiative over the past
two years are presented.
Data for the recent TC seasons have been added to the SHTC archive and
it now consists of TC best track data for the “satellite era” i.e. the TC seasons
from 1969-70 to 2009-10, covering name (and/or unique identification number),
position and intensity (in terms of central pressure). To provide a user-friendly
means for accessing detailed information and data on historical tropical cyclones
for the SH, a new design for the website has been developed at the National
Climate Centre, Australian Bureau of Meteorology (http://www.bom.gov.au/
cyclone/history/tracks/).
The statistical significance of trends in TCs in the South Indian Ocean and
the South Pacific Ocean has been examined. Calculation of significance was
based on non-parametric Monte Carlo methods, and additionally it was explored
whether a constant model, a linear model or a simple break-point model
represents a best fit to the data. For the 1981-82 to 2006-07 TC seasons, there
are no apparent trends in the total numbers of TCs (those tropical systems
attaining a minimum central pressure of 995 hPa or lower), nor in numbers of
970 hPa TCs (such TCs being called severe in the Southern Hemisphere).
Positive trends in the numbers of 945 hPa and 950 hPa TCs in the South Indian
Ocean are significant, but appear to be influenced to some extent by changes
in data quality. In the Australian region, no significant trends in the total numbers
of TCs, or in the proportion of the most intense TCs, have been found.
These findings are important as the data set used constitutes the official
best track data archive for the Southern Hemisphere, even though there are
uncertainties in TC intensity estimates (mainly prior to the 1990s). Despite all
this, the archive represents the current best estimate of recent SH TC
climatology. Attempts have been made to prepare consolidated global datasets
and there are plans to continue these efforts. However, consolidation of historical
data from various regions is currently limited by the inhomogeneity of TC
observation and analysis practice, and there is evidently a considerable need
for re-analysis of the historical TC data in order to obtain globally homogeneous
records. These homogeneity issues place limit on our ability at the present
time to answer the important question of how TC activity is changing and its
possible relationship to global climate change more generally.