Climate change projections for the Torres Strait region

Abstract

The Torres Strait Island region extends from the Cape York Peninsula to within 5 km of the Papua New Guinea (PNG) coastline. The specific objectives of this paper are to provide a brief discussion on observed climate of the region and also to provide future climate change projections for a number of variables using CMIP3 models. Due to the location, the region experiences high solar radiation, air and sea surface temperatures and relative humidity throughout the year and high rainfall during the wet season associated with the monsoon. The annual average temperature increased by 0.25°C per decade from 1960 to mid 1990s and by 0.51°C per decade from mid 1990s to 2009. The annual apparent temperature is 38.4°C compared to the annual air temperature of 26.8°C. The rainfall variability of the region is influenced by El Nino-Southern Oscillation on the interannual time scale and Madden-Julian oscillation on the intra-seasonal time scale. Extreme rainfall events tend to occur during the monsoon season and drier conditions associated with southeast trade winds. Best estimates of annual changes and ranges of uncertainty in climate variables are given for 2030, 2050 and 2070 for SRES A2 and A1FI emission scenarios using CMIP3 simulations and changes in seasonal values are given in Suppiah et al. (2010). The best estimate for annual average temperature increase by 2030 is 0.9 oC, with a range of uncertainty of 0.6 to 1.1 oC for the A2 emission scenario. For the A1FI emission scenario the annual increase by 2030 is 1.0 oC with the range of uncertainty of 0.7 to 1.3 oC. The projected increase in the average annual apparent temperature for the A2 emission scenario by 2030 is 1.3 oC with a range of uncertainty of 0.9 to 1.7 oC, and for the A1FI emission scenario is 1.6 oC with a range of uncertainty of 1.0 to 2.0oC. Best annual estimates are 2.3 and 3.2 oC for the A2 emission scenario and 2.7 and 3.8 oC for the A1FI emission scenario for 2050 and 2070. Projected rainfall changes show a slight increase. The best estimate of regional average annual rainfall change for the A2 emission scenario for 2030 is +1.2% with a range of uncertainty of -3.0 to + 5.3%. For the A1FI emission scenario the best estimate for 2030 is +1.5% with the range of uncertainty of -3.5 to +6.3%. Larger ranges and slight increases in means are projected for 2050 and 2070. An increase in potential evaporation is projected. The best estimate of annual increase by 2030 for the A2 emission scenario is 2.6% with an uncertainty range between 1.9 and 4.7%. For the A1FI emission scenario, the annual increase by 2030 is 3.7% with an uncertainty range between 2.3 and 5.9%. Small changes are projected for solar radiation, relative humidity and winds speed. Of the climate variables investigated in this study those expected to show the most significant changes due to climate change are rainfall (increase in the wet season), apparent and atmospheric temperature and potential evaporation. Sea level rise due to climate change is expected to pose the greatest threat to island communities. Tide gauge data from the region suggest sea level rise of 6 mm per year between 1993 and 2010, twice the global average. It is likely that increases in sea level will not be linear. Current warming of the oceans and atmosphere are likely to drive an increase in global sea level for at least several centuries, even if we drastically reduce the greenhouse gases emissions at present. The practical implications of these projections suggest possible widespread impact across the region. Such impact can significantly affect marine and terrestrial ecosystem health, agricultural productivity, water resources, fisheries, human health, human migration, tourism, and pest abundance and distribution in the region.