In this essay we will discuss about the geological factors causing climate change. The factors are: 1. Continental Drifting 2. Volcanic Dust Impact 3. Anthropogenic Factors.
1. Continental Drifting:
It suggests that glaciations are linked to continental drifting.
The Ewing-Donn theory proposes that Pleistocene glaciation was initiated when, the North Pole reached its present position in the middle of the Arctic Ocean, and Antarctica became coincident with the South Polar Region.
These theories are based on the presumption that some 300 million years ago all the continents were joined together to form the super-continent ‘Pangaea’ which was located at high latitudes far to the south of their present positions.
Although Pangaea was centered on the equator, its southern-most part included the South Pole.
There was a rift in the Pangaea, and it gradually broke up into the separate continents. These continents drifted apart to occupy their present position.
This revolutionary theory emerging from geology explains how large fragments of glaciated terrain reached their scattered subtropical locations.
Since the plates move at a very slow rate of only a few centimeters per year, significant changes in the positions of continents occur over large scales of geological time. Therefore large-scale climatic changes also happen in millions of years.
2. Volcanic Dust Impact:
Volcanic dust particles, deflects light of short wavelengths coming from the sun. But long wave terrestrial radiation can easily pass through volcanic dust without any loss and large-scale volcanic dust may lower down the earth’s temperature to a certain extent.
The large amount of volcanic dust present in the atmosphere is possibly one of the causes of the ‘Little Ice Age’. Accordingly the ice ages are supposed to be initiated during time period of frequent volcanic eruptions.
3. Anthropogenic Factors:
The united Nations framework convention on climate change (UNFCCC) defines ‘climate change’ as a change of climate which is attributed directly or indirectly to human activity that alerts the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods.
Human activities are considered largely responsible in enhancing the greenhouse effect.
i. Increase in Air Temperature:
Earth has warmed at an unprecedented rate over the last hundred years and particularly over the last two decades. Since 1992, each year has been one of the 20 warmest years on record. 2010 was the hottest year on record, worldwide.
The air temperatures are the highest since recordings were begun in earnest more than 100 years ago.
This is the result of emission of carbon dioxide and greenhouse gases from human activity including industrial processes, fossil fuel combustion, deforestation and change, in the land use patterns.
The world is warming, Climatic zones are shifting, Glaciers are melting, Sea-levels rising and we expect them to accelerate over the next years as the amounts of carbon dioxide, methane, and other trace gases accumulated in the atmosphere through human activities increase.
It is observed that the increase in the air temperature in the 20th Century has been about 0.5°C. In fact, the last five decades of the 20th Century and first decade of the 21st Century (1950-2010) have been the warmest years since the systematic recording of temperature began in 1878.
The earth temperature was about 14°C in 1950 which rose to about 15°C in 2000.
ii. Black Carbon:
Black carbon (BC) is an aerosol contributing to warming of the atmosphere.
Black carbon, commonly known as soot, is a form of particulate air pollutant, produced from incomplete combustion of biomass burning, cooking with solid fuels, diesel exhaust etc.
It consists of pure carbon in several linked forms.
Black Carbon influences the climate in the following two ways:
(i) When suspended in air, Black Carbon absorbs sunlight and generates heat in the atmosphere, which warms the air and can affect regional cloud formation and precipitation patterns.
(ii) When deposited on snow and ice, it reduces the albedo and increases the absorption of sunlight, generating heat, which warms both the air above and the snow and ice below accelerating melting.
The black carbon remains in the atmosphere for one to four weeks affecting the climate regionally. Its short life time also means that its climate effects would dissipate quickly if black carbon emission were reduced.
The black carbon may be responsible for more than 30 per cent of recent warming in the Arctic contributing to the accelerated melting of ice.
Loss of ice of the Arctic Ocean would lead to more rapid warming and possibly irreversible climate change.
Black Carbon may also be driving some of the observed reduction of the snowpack in the Pacific Northwest of North America.
Different types of soot have different amounts of black carbon generally the blacker the soot, the more warming agent it is.
Fossil fuel and bio-fuel soot is much blacker than soot from biomass burning, which is generally brownish in colour. Controlling emissions of soot from fuel sources is an effective way of reducing atmospheric temperatures in the short term.
Based on current information, most of the black carbon emissions come from the developed countries in which the share of United States of America is over 6%. China and India account for some 25 to 35% of the total black carbon emissions of the world.
Indian Government Initiative:
Project Surya has been launched to reduce black carbon in atmosphere by introducing efficient stove technologies, solar cookers, solar lamps and biogas plants.
Brown carbon is a ubiquitous and unidentified component of organic aerosol. Light- absorbing organic matters (other than soot) in atmospheric aerosols is of various origins, e.g., soil humics, humic-like substances (HULIS), tarry materials from combustion, bio-aerosols, etc.
Biomass burning (domestic wood burning) is shown to be a major source of brown carbon. Smoke from agricultural fires is an additional source.
“Brown carbon” is generally referred for greenhouse gases and “black carbon” for particles resulting from impure combustion, such as soot and dust.
iii. Green House Gases:
Greenhouse effect is the retention of heat in the lower atmosphere due to absorption and re-radiation by clouds and certain gases. It is a naturally occurring phenomenon that blankets the earth’s lower atmosphere and warms it, maintaining the temperature suitable for living organisms to survive.
According to one estimate, in the absence of naturally occurring greenhouse effect, the average temperature of the earth surface would be -19°C instead of present value of 15°C and the earth would be a frozen lifeless planet.
It is a building made of glass chambers in which plants are grown in cold countries or in cold climate areas. There is a continued increase in temperature in green house even when the outside temperature remained low. It protects plants from frost. Just as greenhouses, that keep the air warm inside its chamber, the water vapor and greenhouse gases keep the earth warm.
Greenhouse gases play an important role in the balance of Earth’s cooling and warming.
They are added to the atmosphere either by the natural or by anthropogenic process, the carbon dioxide, methane, chlorofluorocarbon, Nitrous Oxide, Ozone, Water Vapour are the main gases responsible for the global warming.
1. Carbon-Dioxide (CO2):
Carbon dioxide and water vapour are the most important greenhouse gases. They stop long-wave radiation from escaping there by, trapping heat and raising Earth’s temperature.
The Industrial Revolution in Europe in the mid-17th Century, burning of fossils fuels, destruction and inadequate replacement rate of forest is causing atmospheric CO2 levels to increase about 8 billion metric tons to 10 billion metric tons per year constituting 60% of the global warming.
The CO2 concentration which was 180 parts per million in 1800 A.D is expected to increase to 600 parts per million by the end of 21st Century.
The global temperatures are increasing fast leading to catastrophic global warming, which would melt the polar caps, resulting into sea-level rise, stormy weather, droughts and floods in turn effecting agriculture and other primary, secondary, tertiary activities
Atomic level simulation studies suggest that increased concentrations of carbon dioxide (CO2) in the atmosphere can cause ice to become more brittle, not unlike the breaking up or cracking of materials due to corrosion. Thus CO2 can play the role of a corroding agent and lead to destabilization of the structures.
2. Methane (CH4):
Since the beginning of the Industrial Revolution in Britain and Europe (1779), apart from the atmospheric concentration of carbon dioxide, methane concentrations have more than doubled, and nitrous oxide concentrations have risen by about 15 per cent enhancing the trapping capability of the Earth’s atmosphere
Methane is another radiatively active gas contributing to the overall greenhouse effect. It is increasing in concentration at about 1 per cent per year.
Methane is generated by organic processes, such as digestion and rotting in the absence of oxygen (anaerobic processes).
About 50 per cent of the excess methane being produced comes as a by-product during microbial fermentation in the four-chambered stomach of livestock and from underwater bacteria in rice fields.
Methane is now believed responsible for at least 12 per cent of the total atmospheric warming, complementing the warming caused by the buildup of CO2 and equaling about one half the contribution of CFCs.
3. Water Vapour (H2O):
Water vapour is the biggest overall contributor to the greenhouse effect and humans are not directly responsible for emitting this gas in quantities sufficient to change its concentration in the atmosphere.
However, CO2 and other greenhouse gases are increasing the amount of water vapour in the air by boosting the rate of evaporation.
Unlike CO2, which can persist in the air for centuries, water vapour cycles through the atmosphere, quickly evaporating from the oceans and elsewhere before precipitating as rain or snow.
Since the rate of evaporation rises with temperature, the amount of water vapour in the air at any one time is strongly related to the amount of other greenhouse gases in the air.
4. Nitrous Oxide (N2O):
Nitrous oxide is naturally present in the atmosphere as part of the Earth’s nitrogen cycle, and has a variety of natural sources but mainly from bacteria breaking down nitrogen in soils.
However, human activities such as agriculture, fossil fuel combustion, waste water management, and industrial processes are increasing the amount of N2O in the atmosphere.
Nitrous oxide is removed from the atmosphere when it is absorbed by certain types of bacteria or destroyed by ultraviolet radiation or chemical reactions.
Nitrous oxide is the greenhouse gas and simultaneously destroys ozone also. It has a twin damaging effect on the atmosphere or climate change.
The global warming capacity of nitrous oxide is 270 times higher than that of carbon dioxide.
5. Chlorofluorocarbon (CFCs):
Chlorofluorocarbon gases are large manufactured molecules (polymers) containing chlorine, fluorine, and carbon possessing remarkable heat properties.
Many fluorinated gases have very high global warming potential (GWPs) relative to other greenhouse gases. Fluorinated gases are well mixed in the atmosphere, spreading around after their emission.
Fluorinated gases are removed from the atmosphere only when they are destroyed by sunlight in the far upper atmosphere. These fluorinated gases are the most potential and lasts longer compared to other GHG’s.
Main categories of fluorinated gases:
1. Hydro-fluorocarbons (HFCs)
2. Hydro-chlorofluorocarbons (HCFCs)
3. Chlorofluorocarbons (CFCs)
4. Per-fluorocarbons (PFCs)
5. Sulfur hexafluoride (SF6)
After slow transport to the stratosphere ozone layer CFCs react with ultraviolet radiation freeing chlorine atoms that act as a catalyst to produce reactions that destroy ozone.
Chlorofluorocarbons (CFCs) are thought to contribute about 25% of the global warming.
CFCs absorb infrared in wavelength missed by carbon dioxide and water vapour in the lower troposphere. As relatively active gases, CFCs enhance the greenhouse effect, and also play negative role in stratospheric ozone depletion.
C.F. Schonbein discovered ozone. It is an unstable gaseous triatomic isotope of oxygen occurring naturally in the atmosphere. It is pale blue in colour at room temperature having a fresh and slightly sharp smell, similar to chlorine.
In the atmosphere the ozone is formed due to photochemical process that occurs in the presence of UV radiation. UV light breaks up oxygen molecules into atoms. The resulting oxygen atoms combine with two oxygen molecules to form two molecules of ozone.
It is a reactive gas that is heavy and gives rise to irritability even in low concentrations. It plays a dual role in nature-one is protective and the other is destructive.
It is found in the troposphere and stratosphere. In the troposphere, it is found in the upper layers and increases in volume after thunder and lightning storms.
In the upper layers of the atmosphere, ozone gives an umbrella-like protection, but if it is closer to the earth’s surface, it causes respiratory diseases.
The ozone layer forms a natural protective layer in the stratosphere. In the stratosphere, most of it is found at a height of 15-35 km called as ozonosphere. It absorbs the harmful ultraviolet radiation (UV-B) and protects life forms. UV-B can penetrate skin and alter the DNA molecules in plants and animals. In humans, it causes sunburns and may even cause basal cell and squamous cell cancers. It also causes cataracts and weakens the immune system. Closer to the surface of the earth, ozone is produced due to human activities and natural processes.
It reduces crop yields and ocean plankton.
Ozone Layer Depletion:
In 1970s scientists discovered that human activities release gases that deplete ozone. Soon it was established that halons, halogenated gases, chlorofluorocarbons are the cause for ozone destruction. Such substances are called as ozone depleting substances (ODS)
Ozone depletion had seasonality and highest depletion occurs in spring time over Antarctica. Ozone holes are also formed over the arctic region.
The reason for the ozone hole formation is both atmospheric and chemical. The extreme winter temperatures lead the formation of Polar Stratospheric Clouds (PSCs). This is an associated phenomenon that increased the relative abundance of reactive chlorine gas.
Extreme winter temperatures have duration of about 5-6 months over Antarctica and 1-2 months over Arctic Circle. Temperatures fall below -78°C. The air is also isolated due to the low temperatures. This creates conditions that are amenable for chemical reactions involving chlorine and bromine that destroy the natural ozone. By early spring, the ozone layer is completely destroyed leaving a gaping hole.
Ozone depleting substances (ODS) have variety of combination of chemical elements chlorine, fluorine, bromine, carbon and hydrogen.
Ozone depleting substances have two advantages that work in their favour.
They have long life span from 20-120 years and do not break down in the lower layers of the atmosphere. They float up in the atmosphere and reach the stratosphere. CFCs do not dissolve in rain, so cannot be washed out of the atmosphere.
Secondly they contain either chlorine or bromine that essentially break up ozone. Once they are in the stratosphere, the UV radiation breaks up these molecules into chlorine from CFCs or Carbon tetrachloride (CCI4) and bromines from halons or methyl bromide. The free chlorine and bromine react with 03 and break it up.
Initiatives to Protect Ozone Layer:
1. Vienna Convention for the Protection of the Ozone Layer:
It is a Multilateral Environmental Agreement agreed upon at the Vienna Conference of 1985 and entered into force in 1988.
It has been ratified by 197 states (all United Nations members as well as the Holy See, Niue and the Cook Islands) as well as the European Union.
It acts as a framework for the international efforts to protect the ozone layer.
It does not include legally binding reduction goals for the use of CFCs, the main chemical agents causing ozone depletion. These are laid out in the accompanying Montreal Protocol.
2. Montreal Protocol on Substances that Deplete the Ozone Layer:
It is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion. It was agreed on 16 September 1987, and entered into force on 1 January 1989.
Major Causes of increases in Green House Gases:
The increase in the production of greenhouse gases is mainly due to the anthropogenic activities of human beings like:
1. Land use Change:
By clearing out forests in various parts of the world to set industries and other developmental projects, man contributes to one-third of total anthropogenic CO2 emission.
2. Burning Fossil Fuels:
Burning fossil fuels to generate heat for industrial purposes release large volumes of CO2.
3. Rise of Cattle and Dairy Farming:
Enteric fermentation of carbohydrates leads to the release of methane. Methane is belched out or let out as flatulence by these animals. Cattle manure is also a source of methane gas that can be harnessed to make biogas.
Industrial revolution was a turning point in the history of climate change. The reduction in the area of forest land led to fall in area of carbon sink.
4. Use of Fertilizers in Agriculture:
Increased use of fertilizers has led to the higher concentration of nitrous oxide.
5. Burning Natural Gas and Petroleum Products:
About 36% of the GHG’s emissions come from combustion of liquid fuels, gasoline and fuel oils. Natural gas combustion contributes about 20% of emissions.
Steps to Reduce Emission of Greenhouse Gases:
(i) Alternative Sources of Energy:
The renewable and non-conventional energy sources like solar, wind, and tidal provides only about 18 per cent of the total electricity generated in the world and there should be efforts to reduce the use of thermal power and increase the use of alternate sources of energy.
(ii) Generation of Nuclear Power:
Measures should be taken to increase the production of nuclear power as it accounts for about 14 per cent of the world’s electricity produced and consumed.
Planting instead of felling more trees
(iv) Urban Planning:
Encroachment of agricultural land for non-agricultural purposes should be avoided. The urban areas should implement environmentally protective measures like multiple transport choices, green areas and ‘green belts.
(v) Building Designing:
It is to use the solar heat and light resources in the construction design and also to use insulation and high efficiency appliances.
(vi) Controlled Burning of Biomass:
Promoting biomass fuelled power plants to reduce the emission of greenhouse gases.
(vii) Reduction in the Growth of Population:
Used in the framing of measures and policies to control population growth.
(viii) Reduction in Consumerism:
With consumerism, the judicious use of goods has come down resulting in more and more of wastage of resources.
(ix) Mass Education about Ecology and Environment:
Proactive use of media, holding workshops, conferences and seminars can train and tune the general public into cultivating habits to Conserve resources and protect the environment.
(x) Developing appropriate technologies so as to adapt and mitigate the adverse impact of the emission of greenhouse gases, like the diesel vehicles being fitted with filters to capture black carbon and replacing inefficient cooking stoves with cleaner alternatives.