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Global Warming Causes Sea-Level Rise And Flooding
Changes in mean temperatures and rainfall, and rising sea levels will affect the suitability of land for different types of crops and pasture, the health and productivity of forests, increase the incidences of pests and diseases, affect biodiversity and ecosystems; raise socio economic and resource insecurities.
1. Glacial melting
2. Higher sea
temperature
4. Heavier rainfalls
According to IPCC report,
global sea level rose by about 120 m during the several millennia
that followed the end of the last ice age (about 21 000 years ago), stabilized between
Sea level rise has caused more frequent and severe coastal
flooding Shanghai, a rapidly
urbanized city in the mega delta, has reported a sea level rise of
120 millimeters since 1977 - a level higher than the national
average of 90mm, and fastest in history. Many scientists believe rising sea
levels are caused by global warming but the city's continuous
land subsidence exacerbates the problem. At the same time, the
city is sinking by about seven millimeters every year, partly
due to the overuse of underground water and the rapid urban
construction. (Shanghai Daily Dec 4, 2007)
China is recently very much affected by this rise of sea-water level mainly aggravated by heavy rainfall. In East China's Fujian province, rains lasted more than 10 consecutive days. In Southwest China's Yunnan province, a torrential rain lasted seven-hours. In Guangdong province's Huilai county, 603.5 mm of rain fell over a six-hour period, setting a record in about half a millennium. These had caused the collapse of reservoirs and rivers banks, landslides, power failures, and damage to highways. (Many of the same areas until several months ago had endured the worst drought in a century.) The Xinhua Press reported that, as at June the floods in China in year 2010 have affected 70 million people in 22 regions with death toll of 379 and 141 missing. 4.45 million hectares of farmland had been inundated, causing direct economic losses of USD 17 billion.
Cyclone Sidr hit Bangladesh on November 15, 2007, causing widespread flooding and massive destruction in coastal communities, with the Red Crescent Society estimating 10,000 of death toll. International groups pledged US$95 million to repair the damage. The flooding has been declared a national calamity by the government. ''Floods in Bangladesh can't be controlled even with all the resources of the world put together,'' President Ershad told the press. ''Even partial protection requires a lot of money, and Bangladesh is a poor country.'' Contrasting a poverty stricken Bangladesh, we now turn to the Netherlands, a developed industrialized country, more than half of which consists of coastal lowlands below sea level. It is one of the most densely populated areas in the world; with more than 55% of the 14 million inhabitants found along coastal mega cities such as Rotterdam, the Hague and Amsterdam. The country has over the years established an elaborate system comprising about 400 km of dykes and coastal dunes to protect it from the sea. Further reinforcement would just require use of the effects of various forces (tides, currents, waves, wind and gravity) on the sands and sediments so as to create a stable barrier. No new technology will be required against sea level rise next century. Dykes and sand dunes will just need to be raised; though additional pumping will be necessary to combat the intrusion of saline water into freshwater aquifers. An estimate of about USD 12 billion would be required for protection against a sea level rise of 1 m, which is probably within the reach of the country. The smaller islands are also most exposed to multiple risks which threaten islanders' livelihood. Risks are coastal erosion, coral bleaching, and reduction in fresh water resources. The rising sea water causes intrusion of salt water into fresh water resources, aggravating the existing water-stress problems. Examples are the Maldives in the Indian Ocean, consisting of 1190 individual islands, and the Marshall Islands in the Pacific, which lie almost entirely within 3 m of sea level. In the US, rare and deadly flash flooding events are not uncommon, with recent (mid 2010) line-ups of extreme precipitation in Arkansas, Tennessee and Oklahoma. The rainfall was extremely unusual, as most of it fell in just a few hours. The Tennessee event, in which 13 -19 inches of rain fell during a two-day period, flooding much of the state including downtown Nashville, was around a 1-in-1,000-year event. And the Oklahoma City floods were a 1-in-100-year event. In Brazil, in its capital of Rio de Janeiro, a record 11.3 inches rain fell within 24 hours in mid April 2010, causing severe flooding and mudslides. Thousands of people have been left homeless, with reports of at least 154 deaths and many missing. Two months later, in late June, heavy rainfall resulted in severe flooding and mudslides in Alagoas and Pernambuco states.
Many scientists warned that the IPCC probably made a far too conservative estimate of sea level rise of 1.7mm per year in the 20th century when it explicitly left out the ice effect. With the earlier than anticipated melting of ice and the shrinking of ice sheets, scientists warned of far greater and much earlier rise of sea level ahead.
Alarmingly, these extreme events are becoming more
common, with high probabilities of increased frequency and severity
in decades to come, as more water vapor is added to the atmosphere
in response to a warming climate.
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