Complex sentence: Notwithstanding the uncertainty as to the climate science analysis of sea level change relative to the islands of Tuvalu, there are observable changes that have occurred over the last ten to fifteen years that show Tuvaluans that there have been changes to sea levels.
Split into simpler sentences: Notwithstanding the uncertainty as to the climate science analysis of sea level change relative to the islands of Tuvalu. There are observable changes that have occurred over the last ten to fifteen years that show Tuvaluans that there have been changes to sea levels.