Microscopic charcoal preserved in sediments from ten wetlands in the Indonesian and Papua New Guinea region provide a proxy record of regional fire events during the last 20,000 years. Two periods of high regional charcoal frequency are encountered during the last glacial transition (17,000-9000 years B.P.) and the middle to late Holocene (5000 years B.P. to the present). Despite the presence of humans in the region throughout the last 20,000 years, there is no suggestion that, on a regional spatial scale, fire frequencies were solely related to changing subsistence patterns of the human population. Pollen data from these same sites suggest that during times of high charcoal the rate at which vegetation changes, represented by the fossil pollen spectra, also increases. High climate variability may promote a greater community turnover rate and in turn a more fire susceptible forest community. Rapid climate change and high variability during the last glacial transition and intensification of El Niño-related climate variability during the middle to late Holocene, may have been important mechanisms for promoting fire in rainforest environments and maintaining diversity of tropical rain forests.