Md. Arafat Rahman
G lobal warming is a special phenomenon of climate change. This is one of the major environmental problems in the world today. It is approaching a climate change that is procedurally comparable to the greenhouse effect. It is very important to bring the problem under control because the chemical composition of the Earth’s atmosphere is already completely different from what it was hundred years ago, in fact it is not possible to reverse these change in the near future through current technological advances.
There was little net warming between the 18th century and the mid-19th century. Climate proxies, sources of climate information from natural archives such as trees and ice cores, show that natural variations offset the early effects of the Industrial Revolution. The Intergovernmental Panel on Climate Change (IPCC) has adopted the baseline reference period 1850–1900 as an approximation of pre-industrial global mean surface temperature, when thermometer records began to provide global coverage.
The reason for the recent global warming has been the gradual increase in the presence of certain greenhouse gases in the atmosphere. These atmospheric gases do not prevent short-wave solar rays from reaching the Earth, whereas prevents long-wave infrared radiation reaching the outer atmosphere from Earth and causing the Earth’s surface to warm up. The gases responsible for global warming are carbon dioxide, nitrous oxide, methane, chlorofluorocarbons and atmospheric water vapor. Industrialization, agricultural expansion, especially wet paddy cultivation, increase in the number of automotive vehicles, deforestation all play a significant role in increasing the amount of those gases.
Patterns of warming are independent where greenhouse gases are emitted, because the gases persist long enough to diffuse across the planet; however, localized black carbon deposits on snow and ice do contribute to Arctic warming. Since the pre-industrial period, global average land temperatures have increased almost twice as fast as global average surface temperatures. This is because of the larger heat capacity of oceans, and because oceans lose more heat by evaporation. Over 90% of the additional energy in the climate system over the last 50 years has been stored in the ocean, warming it. The remainder of the additional energy has melted ice and warmed the continents and the atmosphere.
The Northern Hemisphere and North Pole have warmed much faster than the South Pole and Southern Hemisphere. The Northern Hemisphere not only has much more land, but also more snow area and sea ice, because of how the land masses are arranged around the Arctic Ocean. As these surfaces flip from reflecting a lot of light to being dark after the ice has melted, they start absorbing more heat. The Southern Hemisphere already had little sea ice in summer before it started warming. Arctic temperatures have increased and are predicted to continue to increase during this century at over twice the rate of the rest of the world. Melting of glaciers and ice sheets in the Arctic disrupts ocean circulation, including a weakened Gulf Stream, causing increased warming in some areas.
Temperature rise on land is about twice the global average increase, leading to desert expansion and more common heat waves and wildfires. Increasing rates of evaporation cause more intense storms and weather extremes. Temperature rise is amplified in the Arctic, where it has contributed to melting permafrost, glacial retreat and sea ice loss. Additional warming also increases the risk of triggering critical thresholds called tipping points.
Scientists concern that global warming could lead to climate change, sea level rise and change in population density and distribution in Bangladesh.
Using common rotation models in the process of climate change, scientists predict that as the amount of carbon dioxide in the atmosphere doubles, the range of global temperature change will be 1.5 to 4.5 degree Celsius. However, a downward review by the Intergovernmental Panel on Climate Change has suggested that the range of these changes is 3.3 degree Celsius. This downward review takes into account the depletion of the ozone layer in the atmospheric stratosphere and the possibility of cooling the air layer as a result of the presence of sulfate aerosols in the atmosphere.
The climate model invented by the IPCC indicates that Bangladesh will experience 10 to 15 percent more rainfall by 2030. Bangladesh is often hit by devastating floods. The last two decades saw massive floods in 1987, 1987 and 1998. These floods caused extensive damage to the country’s infrastructure and destroyed crops. The increase in rainfall during this time makes the situation worse. Scientists also concern that global warming will increase the number and intensity of tropical storms. Sea surface temperatures above 27 degree Celsius are conducive to cyclones.
Global warming will increase sea surface temperatures more than at present, resulting in a significant increase in the number and intensity of cyclones. One such cyclone struck Bangladesh in 1991, killed 150,000 people and caused severe damage to livestock and other resources.
“A warmer climate will further increase the incidence of such catastrophes by increasing the number of natural disasters such as floods and cyclones and will severely hamper the country’s development efforts.”
Tidal fluctuations, atmospheric pressure, and wind speeds in each area cause endless sea level changes, but in the long run sea level changes are the only global climate change. Global warming will cause a thermal swelling of the sea water. Rising temperatures will also contribute to the melting of polar and mountain ice caps and ice cubes. As a deltaic land, a large area of Bangladesh will be submerged due to rising sea level. How much of the country will lost to the oceans will depend on sea level changes. A task force report says that if the sea level rises by one meter, about 22,889 sq km of land will be lost to the sea, which is about 15.8% of the total area of Bangladesh.
As a lowland and high population density country, Bangladesh will be severely affected by rising sea levels. Increasing tidal intensity will cause landslides and floods in coastal areas. Sea level rise will help the brackish water to penetrate further inland during high tide. Agricultural land and animals and plants will be destroyed. The entry of the coastline into the mainland will result in a change in the shape of the coastal boundary. This will shrink the territory of Bangladesh.
It is estimated that by 2100 the Earth’s surface temperature will rise by 1.8 to 6.3 degree Celsius. This will increase sea level by 0.5 meters and threaten massive flooding in coastal and deltaic areas with high levels of population from Mississippi to Bangladesh. Climate disasters such as hurricanes, cyclones and droughts will occur frequently and increase in intensity. Tropical diseases such as malaria and cholera can spread north and south of the equatorial region due to global warming.
Global warming may result in more rainfall, massive floods, severe cyclones, etc. in Bangladesh. According to estimates by NASA’s Goddard Institute for Space Studies, 2005 was the warmest year. The World Meteorological Organization and the UK’s Climate Research Unit estimate 2005 to be the second warmest year.
Greenhouse gases such as carbon dioxide, carbon monoxide, sulfur dioxide and other oxides of sulfur, nitric oxide, chlorofluorocarbons, etc., radiate heat from the earth’s atmosphere. This heat, in the form of infrared radiation, is absorbed and emitted by these gases into the planet’s atmosphere, warming the lower atmosphere and the surface. An increase in carbon dioxide in the atmosphere increases the rate of dissolution in the oceans. Dissolved carbon dioxide reacts with water to produce carbonic acid, resulting in ocean acidification. The same process that causes carbon dioxide radiation to cause warming near the earth’s surface cools the stratosphere much unexpectedly. And this cooling increases the depletion of the ozone layer and the number of ozone cracks. Depletion of the ozone layer creates radiation stress on the climate system.
As the ozone layer depletes, more solar radiation can come to Earth, heating the troposphere instead of the stratosphere. Again this results in the cooled stratosphere sending long wave radiation down to the troposphere, which cools the troposphere. All in all, it has been seen that the effect of cooling action is more. Scientists have concluded that significant erosion of the stratosphere over the past two decades has had a negative impact on the subterranean troposphere.
Long-term scenarios point to rapid and significant investment in renewable energy and energy efficiency as key to reducing green house gas emissions. Renewable energy technologies include solar and wind power, bioenergy, geothermal energy, and hydropower.
Fossil fuels accounted for 80% of the world’s energy in 2018, while the remaining share was split between nuclear power and renewables; that mix is projected to change significantly over the next 30 years. Photovoltaic solar and wind, in particular, have seen substantial growth and progress over the last few years, such that they are currently among the cheapest sources of new power generation.
To tackle global warming, people need to be aware, reduce the use of cars, factory fumes, etc., reduce the use of CFC-emitting equipment, and control the use of fossil fuels. Environmental protection and sustainable development strategies can save the world and its environment and countries like Bangladesh from the catastrophe caused by global warming.
Author is a Columnist, and Asst. Officer of Career & Professional Development Services Department at Southeast University, Dhaka, Bangladesh