Climate change : Scientific basis, observed changes, projection and impacts

Climate change has been singled out as the most important environmental problem that humanity is facing and will face in decades to come. With mean surface temperatures expected to rise by 1-3°C by the middle of the 21st century, the climate pattern is expected to shift and extreme climatic events such as droughts, floods, storms and heat waves will become more frequent and intense (IPCC WGI 2007). The Intergovernmental Panel on Climate Change (IPCC), a scientific body established in 1988 under the WorldMeteorological Organization (WMO) and United Nations Environmental Program (UNEP), has warned of these dire consequences in its Fourth Assessment Report (AR4) released in 2007. Continued warming of the oceans and melting of ice glaciers are projected to cause the sea level to rise, resulting in increased coastal erosion and coastalinundation. Climate change also poses a greater threat to the terrestrial and marine ecosystems. The functioning of ecosystems may be disrupted due to higher temperatures and shifting rainfall distribution. This could result in species migration or even speciesextinction. Meanwhile, increasing ocean temperatures and acidification due to increased absorption of carbon dioxide have a negative impact on the marine ecosystems, fisheries and marine parks. Climate change is also an important factor in the food security issue., A shifted climate pattern and altered water cycles would have detrimental impacts on the agriculture and plantation sectors with floods and droughts destroying crops. As bothagriculture and plantations are important sectors in Malaysia, climate change will have greater implications and consequences for Malaysia.Instrumental records of temperature show that global surface air temperatures have been rising since the pre-industrial period. For a 100-year period from 1906 to 2005, the average global surface temperature increased at a rate of 0.74°C per century. However, since the mid-20th century, warming has accelerated at a rate of 1.3°C per century. The warming rate for the last two decades was even higher. Eleven of the 12 years (1995-2006) ranked among the 12 warmest years in instrumental records of global surfacetemperature since 1850 (IPCC WGI 2007). Due to various regional and local processes,the warming rate varies spatially. Based on observed air temperature records in various recording stations around the country, the warming rates in Malaysia for the last 40 yearsfrom 1961 to 2002 were between 1.0 and 4.0oC per century (Tangang et al. 2007). Changes and extremes in precipitation were also recorded in many parts of the globe. From 1900 to 2005, precipitation increased significantly in eastern parts of North andSouth America, northern Europe and northern and central Asia. However in the Sahel,Mediterranean, southern Africa and parts of southern Asia precipitation decreased significantly. However, globally the area affected by drought has most probably increasedsince 1970. It is very likely since the mid-20th century that cold days, cold nights and frosts have become less frequent whereas heat waves have become more frequent. It is also likely that the frequency of extreme precipitation events has increased in most areas. Consistent with warming, the sea level has been rising since 1961 at an average rate of 1.8 mm per year, and the rising sea level has accelerated since 1993 at a rate of 3.1 mm per year. The causes of these rises include thermal expansion, and the melting of glaciers, icecaps and the polar ice-sheets.The main finding of the IPCC AR4 was that the observed increase in average global temperatures since the mid-20th century may be attributed to the observed increase in anthropogenic greenhouse gas (GHG) concentrations. Global GHG emissions due to human activities have increased since the pre-industrial periods with an increase of 70% between 1970 and 2004. Carbon dioxide (C02) is the most important GHG with annual emissions having increased between 1970 and 2004 by about 80%, from 21 to 28 gigatonnes (Gt). Based on ice-core data spanning many thousands of years, the concentrations of CO2 (379 ppm) and CH4 (1774 ppb) in 2005 exceed the natural rangeover the last 650,000 years (IPCC WGI 2007; Petit et al. 1999). Global increases in C02 concentrations are mainly due to fossil fuel use, with land-use change providing a significant but smaller contribution. It is very likely that the observed increase in CH4concentrations is due to agriculture and fossil fuel use, while the increase in N20 is primarily due to agriculture. The radiative force due to the increment of the concentrations of these GHGs is +2.3 [+2.1 to + 2.5] Wm-2 and its rate of increase during the industrialera is very likely to have been unprecedented in more than 10,000 years (IPCCWGI 2007). Based on 2004 data, the United Nations Framework Convention on Climate Change (UNFCC) Annex I countries held a 20% share in world population, produced 57% of theworld's GDP and accounted for 46% of global GHG emissions (IPCC WGm 2007).There is strong agreement and much evidence that, with the current climate change, mitigation policies and related sustainable development practices, global GHG emissions will continue to increase over the next few decades. The IPCC Special Reporton Emissions Scenarios (SRES) projected an increase in baseline global GHG emissions by a range of 9.7 to 36.6 GtC02-eq (25 to 95%) between 2000 and 2030. For the next two decades a temperature rise of about 0.2°C per decade is projected for a range of SRESscenarios. With continued GHG emissions at or above the present rates, further warming is projected and this would induce many changes in global climate during the 21st century that would likely be larger than those observed during the 20th century. Depending on the scenarios, by the end of 2151 century, the projected average temperature change would be in the range of 1-6°C. For the A1B scenario, the best estimate is 2.8°C with a likely rangeof 1.7-4.4°C. A regional climate downscaling based on the Handley Centre Coupled Model version 3 (HadCM3) conducted by the Malaysian Meteorological Department (MMD) shows that the model projection for the Malaysian region is about 3.0-4.0°C (MMD 2009). For the 2020-2029 and 2050-2059 periods, the projected temperature risesfor the Malaysian region are around 1.5°C and 2.0C, respectively. For precipitation, the amount is very likely to increase in high latitudes and to decrease in most sub-tropical land regions by as much as 20% in the A1B scenario. It is very likely that hot extremes, heat waves and heavy precipitation events will become more frequent. It is also likely that the future tropical cyclones will become more intense. For the Malaysian region, the MMD'sprojection shows a decrease in precipitation by 9-20% for the 2020-2029 period from that of the 1990-1999 mean. For the 2050-2059 period, the projections are rather variable with +6% in some regions to -13% in other regions. In general the MMD's projection shows anincrease in precipitation for the 2090-2099 period by as much as 15% in some regions. However, caution must be exercised when interpreting these results as only one model was employed. This is especially so considering any general circulation model (GCM) usually performs rather poorly in the Maritime Continent region. The future projection of extreme events in Malaysia has yet to be documented. However, extreme events such as droughts and floods are likely to change as these events are associated with monsoon circulation and various climate phenomena such as the El Nino-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD) and the Madden-Julian Oscillation (MJO) that result from atmosphere-ocean interaction in the Indian-Pacific sector (e.g. Tangang and Juneng 2004; Juneng and Tangang 2005; Tangang et al. 2008; Juneng and Tangang 2009). These phenomena are expected to change as both the atmosphere and ocean continue to warm up. For sea level rises, the projections vary with the emission scenario, but the upper limitis 0.59 m by the 21st century. However, recent observations and studies seem to indicate that the IPCC's models are underestimating the sea level rise projection as ice-sheet and glacier melting is occurring at much faster rate than previously understood, especially the Greenland glacier. Some studies projected the rise to be around 1 m or even higher by 2100 (e.g. Meier et al. 2007). The IPCC Fifth Assessment Report (AR5), which is scheduled to be released by 2013, should provide a new thorough assessment of the sealevel rise projections.Changes in the climate systems have brought about many impacts to the physical and biological systems and to many socio-economic sectors. Observational evidence from all continents and most oceans shows that many natural systems are being affected byregional climate change, especially temperature increases. Of more than 29,000 observational data series from 75 studies, that show significant changes in many physical and biological systems, more than 89% are consistent with the direction of change expected as a response to warming (IPCC WGII, 2007). As warming continues somesystems, sectors and regions are likely to be affected. These include various ecosystems, agriculture, coastal systems and human health. Climate change is also projected to impact water resources (Bates et al. 2008). Malaysia will likely to be affected in most sectors by further warming. For the palm oil industry, for which Malaysia is one of world's largest producers, climate change could affect it in many ways. Coastal inundation due to sea level rise and storm surges could destroy the plantations located in coastal areas. Oil palm trees can be affected by higher temperatures. An increase of temperature by more than 1°C as projected by the mid-21st century could reduce oil palm yield as the closure of stomata would occur during midday when temperature is at its highest. Furthermore, the occurrence of an El Nino phenomenon in such a warmer environment would increase the temperature by another 12°C, and hence could further reduce yield. In addition to heat stress, oil palm productivity can also be affected by water-related stresses, especially when the consumptive use of rainfall of 120 mm per month is not met. Prolonged droughts or shifts in rainfall patternthat have been projected in decades to come could have an impact on oil palm. This includes the physiology of sex differentiation of the inflorescences that will manifest in three concurrent impacts. At the time of formation of the floral primordia at 24 monthsbefore harvest, with a dry spell there will be predominance towards male floral differentiation. At 10 months prior to harvest, there will be abortion of the female flowers as a water deficit will prevent the female inflorescence from emerging resulting inabortion, while the male inflorescence will still emerge giving rise to what is known as the male phase of trough period when the number of fruit bunches harvested is low. At the time of harvest, water deficit causes the ripe fruit to crack due to high temperature and low rainfall. Cracked ripe red fruit will dehydrate and turn black giving the impression that the fruit are not ripe, and the whole bunch is not harvested as there is no detached fruit. At theonset of rain, these bunches will start to decay and the Maramuis fungal disease will set in. Thus, a prolonged drought would cause poor female sex differentiation and subsequently poor yield. On the other hand, heavy rain would prevent the male inflorescence fromanthesising and also impede the flight of the pollinating weevils from doing the job of pollinating the anthesising female inflorescences. Heavy rainfall would also cause soil erosion and miring of road transportation of fresh fruit bunches (FFB) and disrupt the harvesting rounds. Too much rain also disrupts fertilizer application and causes fertilizer washout leading to increased leaching of fertilizer nutrients. In general, other oil palm operations will be affected such as herbicide application and collection of loose fruits, while more moisture in the fruit bunches will reduce the oil extraction rate.