Tuesday, March 25, 2014

Why is the earth warming? Carbon footprints and impacts

Humans have extensively altered the global environment. Exponential growth in population and resource use has drastically changed the face of our home planet. Every year more forests, grasslands and wetlands disappear and the deserts grow larger. Burning fossil fuels, cutting down and burning forests raise the concentration of carbon dioxide and other heat trapping gases in the lower atmosphere. Fossil fuel consumption and deforestation have increased the concentration of atmospheric carbon dioxide by 30%. We have more than doubled the concentration of methane and increased the concentration of greenhouse gases (GHGs) that contribute to climate warming. Within next 40-50 years climate is warm enough to disrupt agricultural productivity, alter water distribution and drive countless species to extinction. Every hour, we drive as many as 4 wild species to extinction.

Global climate machine

Greenhouse gases (GHGs) have been essential to the survival life on planet earth. These atmospheric gases envelop the earth. The gases in the atmosphere are held in place by gravity. The gaseous envelope regulates Earth’s temperature. They trap heat and cause the earth to warm. This is called natural greenhouse effect. To make sure that the Earth's temperature remains constant, the balance of these gases in the atmosphere must not be upset.

Enhanced/amplified greenhouse effect

Human activities alter the proportion of GHGs in the atmosphere. The burning of fossil fuels - coal, oil and natural gas – releases more carbon dioxide into the atmosphere. Since 1990, yearly emissions of greenhouse gases have gone up by about 6 billion metric tons (6.61 billion tons) worldwide, an increase of more than 20 percent. The addition of  more GHGs induces more heat trapping by the atmosphere which results in enhanced greenhouse effect. The average surface temperature of the Earth has increased by 0.8 degrees Celsius in the last 130 years, since 1975. It will rise from 1.5 degrees C to 4.5 degrees C by 2060.

Mechanism of greenhouse warming

The energy from the sun that reaches the top of the earth’s atmosphere consists mainly of infrared (IR) and visible light, with a small amount of ultraviolet light (UV). Of  these solar radiation, about 50% is absorbed by the surface of the earth, 20% is absorbed by water droplets in the air and GHGs. The remaining incoming sunlight is reflected back into space. The energy emitted by the earth must equal the energy absorbed for the temperature to remain constant. Currently, the planet is absorbing more than it emits.  Water vapor acts as an amplifier of warming.

Carbon dioxide: the principal climate altering gas

Generally single element gas molecules like oxygen and nitrogen are transparent to heat and they constitute about 99 per cent of our atmosphere: 78 per cent nitrogen and 21 per cent oxygen. They do not really affect the climate regulation on the planet. The six trace gases that are blamed for global warming make up only 1 per cent of gases in the atmosphere. The gases created mainly by human activities are: carbon dioxide, methane, nitrous oxide, sulphur hexafluoride, hydrofluorocarbons and perfluorocarbons. The polyatomic  gases such as water vapor, methane and carbon dioxide trap heat in the atmosphere much like glass in a greenhouse traps heat. The atmospheric carbon dioxide is the principal climate –altering gas. An individual molecule of CO2 has a short residence time in the atmosphere. The warming potential of CO2 has very little to do with the residence time of CO2. What really governs the warming potential is how long the extra CO2 remains in the atmosphere. Around 20% of carbon dioxide which is emitted due to human activities can remain in the atmosphere for many thousands of years.
Global CO2 Level à1750: 280ppm à1958: 315PPM à2002: 372PPM à2008:384PPM à2100:650-700PPM
China tops the list of global cumulative energy-related CO2 emitting countries. In 2008, china produced 23.5 % of world CO2 emissions while the USA 18.27%, EU 13.98%, India 5.83%, Russia 5.72%, and Japan 4.04%.

Sources of heat – trapping gases (GHGs)

Non-greenhouse gases are nitrogen,N2, oxygen,O2 and argon, Ar. Greenhouse gases  (GHGs) include carbon dioxide (CO2), nitrous oxide (NO2), methane (CH4), chlorofluorocarbons (CFCs)- Freon (a refrigerant), halons ( fire extinguishers) and water vapor -clouds reradiate heat back to Earth. The heat retention capacity of methane is 25 times greater than carbon dioxide. Nitrous oxide is about 200 times more than carbon dioxide. Water vapor and ozone occur naturally in the atmosphere. Carbon dioxide produced also naturally when people and animals breathe. Increased amounts are produced when human beings burn more fossil fuels and wood.Volcanoes also produces this gas. Methane comes from cattle as they digest their food and from the paddy fields, sediments, swamps and landfills. Nitrous oxide is produced from fertilizer use and decomposition of animal wastes.

Global warming

Global warming is a function of increase in carbon dioxide level, increase in greenhouse effect and increase in global temperature. Global warming is caused by the emission of greenhouse gases. 72% of the emitted greenhouse gases are made up of carbon dioxide (CO2). Carbon dioxide emissions therefore are the main cause of global warming. CO2 is caused by burning fuels like oil, natural gas, diesel, petrol and ethanol. Emissions of CO2 have been increasing at a rate of approximately 3% yearly for the past 50 years. Once it is released into the atmosphere where it remains for 100 to 200 years. A warming of 2ºC corresponds to an amount of 250 ppm carbon dioxide concentration in environment. In February 2007, the United Nations Intergovernmental Panel on Climate Change (IPCC) released a report that said global warming was “very likely” – meaning an at least 90 per cent certainty – caused by human activity.

History of global warming

In 1824, French mathematician and scientist Lean Baptiste Fourier described earth as a giant greenhouse with an atmosphere that traps heat from the sun, making life on earth possible. In 1860, John Tyndall, a British scientist postulated that a reduction in the amount of carbon dioxide in the atmosphere decrease the greenhouse effect. After 36 years, Svante Arrhenius, a Swedish chemist hypothesized that doubling the concentration of carbon dioxide would increase the temperature by 5-60C.  In 1938, G.S. Callender, a British meteorologist had gathered information from 200 weather stations around the world and demonstrated that the average surface temperatures had increased between the 1880s and the 1930s.

Ecological effects

Global warming could lead to natural disasters, large-scale food and water shortages and devastating outcomes for wildlife. According to the Intergovernmental Panel on Climate Change, the sea level could rise between 7 and 23 inches (17.8 and 58.4 centimeters) by the end of the century. Rise of just 4 inches (0.9 meters) of sea level would submerge much of the world’s population living near coastal areas. According to research published in Nature, by 2050, rising temperatures could lead to the extinction of more than a million species.
More than a million species face extinction from disappearing habitat, changing ecosystems and acid rain. Scientists have come up with the firmest evidence so far that global warming will significantly increase the intensity of the most extreme storms worldwide. The maximum wind speeds of the strongest tropical cyclones have increased significantly since 1981, according to research published in Nature. Global warming causes more violent swings between floods and droughts. Climate change is expected to have the most severe impact on water supplies. Shortages in future are likely to threaten food production, reduce sanitation, and hinder economic development and damage ecosystems.
 The International Panel on Climate Change estimates that the sea level will rise between 0.6 and 2 feet in the next century. This poses a great threat to coastal wetland ecosystems. Wetlands are a thriving habitat for thousands of species and also serve to protect nearby areas from flooding. The EPA has estimated that a two foot rise in sea level would result in the loss of 17-43 percent of wetlands in the United States. Scientists believe that global warming will cause an increase in global hunger since plant crops become inefficient to produce. Studies show a rise in wild fires due to the slight increase in temperature. Wildfires have the potential to demolish dozens of square miles of both agricultural land and natural habitat of thousands of species of wildlife.

Biological effects

Global warming is currently a critical problem for many species of plants and animals around the globe. Global warming directly affects the metabolic and developmental rates in many animals and processes such as photosynthesis, respiration and growth in plants. Plants and animals are adapted to a specific climate, and can only survive in that particular climate. As the temperature changes, animals must migrate to adapt. The migration of species to more suitable climates upsets the balance of interdependence among species in their ecosystems. Global warming increases the invasion of opportunistic, weedy and/or highly mobile animal species.

Human health effects

A major health risk is the migration of disease carrying insects throughout the world. Mosquitoes carry many major health science related problems like malaria. Extreme high air temperatures contribute directly to deaths from cardiovascular and respiratory disease, particularly among elderly people. The heat waves of summer 2003 in Europe for example, more than 70 000 excess deaths were recorded. High temperatures also raise the levels of ozone and other pollutants in the air that exacerbate cardiovascular and respiratory disease. Urban air pollution causes about 1.2 million deaths every year. Pollen and other aeroallergen levels are also higher in extreme heat. These can trigger asthma, which affects around 300 million people.

Carbon Footprint (CF)

The term describes the total set of greenhouse gas emissions caused by one individual. A measure of the amount of carbon dioxide emitted through fossil fuel combustion. The carbon footprint has become a popular tool to estimate GHG emissions related to human activities (Moss et al 2008,Wiedmann 2009). Carbon footprint (CF) – also named Carbon profile - is the overall amount of carbon dioxide (CO2) and other greenhouse gas (GHG) emissions associated with a product.). An average Carbon footprint of a British citizen is about 10 tonnes of CO2. An average Carbon footprint of an Indian citizen is round about 1.5 tonnes of CO2. The primary footprint is a measure of our direct emissions of carbon dioxide e.g.the burning of fossil fuels for domestic energy consumption and transportation. The secondary footprint is a measure of the indirect carbon dioxide emissions from the whole lifecycle of the products.

Types of  carbon emissions

 Different types of carbon emissions are designated as “colors of carbon
  1.   Brown carbon – industrial emissions of GHGs.
  2.  Black carbon – carbon from incomplete combustion of fossil fuels.
  3.  Green carbon – carbon stored in terrestrial ecosystems-e.g. plants, soils, wetlands grazing lands.
  4. ·Blue carbon – carbon stored in ocean ecosystems- e.g. mangroves, marshes, sea grasses, coral reefs, macro-algae.

The Kyoto Protocol

The Kyoto protocol (Kyoto, Japan) to the United Nations Framework Convention on Climate Change (UNFCCC) is an international treaty that sets binding obligations on industrialized countries to reduce emissions of greenhouse gases(GHGs). The protocol was adopted by parties to the UNFCCC in 1997 and entered into force in 2005.Six greenhouse gases are regulated by the Kyoto Protocol, as they are emitted in significant quantities by human activities and contribute to climate change. The six regulated gases are Carbon dioxide (CO2), Methane (CH4), Nitrous oxide (N2O), Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs) and Sulphur hexafluoride (SF6).

No comments:

Post a Comment