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Climate Change : The ScienceThe Science Impacts of a Changing Climate a) Sea Level Rise (SLR) – Based on conservative measures, global sea level has been rising rapidly at a rate of 1.5 to 2.0 mm/yr (Rahmstorf, 2007) which implies a possible SLR of up to 1.4m by 2100. SLR will not be uniform because of regional currents and the different rigidity of the continental shelves. In particular, many areas with large population centre’s will experience higher SLR, i.e. 40% of Shanghai will be submerged as a result. (Inconvenient Truth, 2006). b) Floods – As warm air carry more moisture, we would expect heavier precipitation in certain parts of the globe, and less in others. Specifically, areas with heavier rainfall will be accompanied by higher frequencies as well. This would result in massive flood for the affected area. c) Drought – In the absence of significant mitigation of greenhouse gases emissions, higher disparity in rainfall distribution can be a possible consequence. Coupled with enhanced evaporation in a warmer global climate, possible effects such as drought prone areas may double in extent from 25% to 50% by 2100 (Hadley Centre, 2006). The drought events are also expected to last longer. d) ENSO (El Nino Southern Oscillation) – For the time being, the warm (i.e. El Nino) phase has shown a tendency to be more frequent, longer lasting and has higher intensity. If this persists, it can trigger less frequent but stronger Atlantic hurricanes which entail widening of rainfall distribution disparity. e) NAO (North Atlantic Oscillation) – Similarly, a positive NAO which means low winter precipitation in some area and above average in others also implies non-uniform rainfall distribution. Positive NAO will also raise sea levels over Northern Europe and lowering them over some parts of the Mediterranean. f) Tropical storm – Although there is little variation in the frequencies of tropical cyclones, researches have shown stronger tropical storms. Global sea surface temperature (SST) has risen strongly over last 35 years in almost every hurricane-forming basin. This is an expected feature of climate change and is strongly correlated with storm formation and intensity. In particular, the Atlantic hurricane season in 2005 (Emanuel, 2005; Webster et al., 2005) has shown the most storm (27), most hurricane (13), most strong US-landing hurricane (4), costliest in total ($200billion+), single most expensive (Katrina), and strongest ever (Wilma). The above trend is likely to worsen due to factors like global warming which will make tropical storms more intense (i.e. stronger winds, heavier rain, and higher sea surges). g) Ice cover – With the cryosphere greatly altered by climate change, Artic sea-ice has shrunk since industrialization. The reduction in the Artic sea-ice area is expected to continue as long as greenhouse gases emissions are not stopped. h) Heatwaves – Heatwave will replace cold spells in most regions, in particular to hit the tropical region. A doubling of carbon dioxide will cause a change of 5-11oC in global temperature (Hadley Centre, 2004). This will greatly endanger the ecosystems and economic activities. i) Extreme climate change – At the current rate of global emission, climatic change is expected to accelerate. On the backdrop of the above scenario, the ice sheet will collapse and lead to a SLR of 4.6-7m. This should suffice in flooding 30-40% of the world’s land area (Rahmstorf, 2007). With SLR rising, uneven rainfall distribution and deadlier heatwaves, destruction of the Amazonia rainforest by 2060 would be highly possible. In the absence of the rainforest we can expect the global carbon recycling system to fail and further catalyze global warming and climate change! As the ocean water gets warmer, it will be able to hold higher level of carbon dioxide. This translates to higher acidity of the water, and is damaging for organisms (i.e. shellfish) which are major sink for carbon dioxide. Likewise, it can accelerate climate change. Reference
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