Climate Change | NOTES | ECETOTAL

Table of Contents

• Climate Change
• Greenhouse Effect and the Carbon Cycle
• Current Evidence of Climatic Change
• Future Effects

Climate Change

Human activities, particularly the combustion of fossil fuels have made the blanket of greenhouse gases (water vapour, carbon dioxide, methane, ozone etc.) around the earth thicker. The resulting increase in global temperature is altering the complex web of systems that allow life to thrive on earth such as rainfall, wind patterns, ocean currents and distribution of plant and animal species.

Greenhouse Effect and the Carbon Cycle

Life on earth is made possible by energy from the sun, which arrives mainly in the form of visible light. About 30% of the sunlight is scattered back into space by the outer atmosphere and the balance 70% reaches the earth's surface, which reflects it in form of infrared radiation. The escape of slow-moving infrared radiation is delayed by greenhouse gases. A thicker blanket of greenhouse gases traps more infrared radiation and increase the earth's temperature.

Greenhouse gases make up only 1% of the atmosphere, but they act as a blanket around the earth, or like a glass roof of a greenhouse and keep the earth 30 degrees warmer than it would be otherwise - without greenhouse gases, the earth would be too cold to live in. Human activities that are responsible for making the greenhouse layer thicker are emissions of carbon dioxide from the combustion of coal, oil and natural gas; by additional methane and nitrous oxide from farming activities and changes in land use; and by several man-made gases that have a long life in the atmosphere. 

The increase in greenhouse gases is happening at an alarming rate. If greenhouse gases emissions continue to grow at current rates, it is almost certain that the atmospheric levels of carbon dioxide will increase twice or thrice from pre-industrial levels during the 21st century. Even a small increase in the earth's temperature will be accompanied by changes in climate such as cloud cover, precipitation, wind patterns and duration of seasons. In already highly crowded and stressed earth, millions of people depend on weather patterns, such as monsoon rains, to continue as they have in the past. Even minimum changes will be disruptive and difficult. Carbon dioxide is responsible for 60% of the "enhanced greenhouse effect.

Humans are burning coal, oil and natural gas at a rate that is much faster than the rate at which these fossil fuels were created. This is releasing the carbon stored in the fuels into the atmosphere and upsetting the co_speechnotes_plugin_fab_id:38,447carbon cycle (a precisely balanced system by which carbon is exchanged between the air, the oceans and land vegetation taking place over millions of years). Currently, carbon dioxide levels in the atmosphere are rising by over 10% every 20 years.

Current Evidence of Climatic Change

Cyclones, storms, hurricanes are occurring more frequently and floods and droughts are more intense than before. This increase in extreme weather events cannot be explained away as random events. This trend toward more powerful storms and hotter, longer dry periods is predicted by computer models. Warmer temperatures mean greater evaporation, and a warmer atmosphere can hold more moisture and hence there is more water aloft that can fall as precipitation. Similarly, dry regions are prone to lose still more moisture if the weather is hotter and hence this leads to more severe droughts and desertification.

Future Effects

Even the minimum predicted shifts in climate for the 21st century are likely to be significant and disruptive. Predictions of future climatic changes are wide-ranging. The global temperature may climb from 1.4 to 5.8 degrees C; the sea level may rise from 9 to 88 cm. Thus, increases in sea level this century are expected to range from significant to catastrophic. This uncertainty reflects the complexity, interrelatedness, and sensitivity of the natural systems that make up the climate.

Severe Storms and Flooding

The minimum warming forecast for the next 100 years is more than twice the 0.6 degrees C increase that has occurred since 1900 and that earlier increase is already having marked consequences. Extreme weather events, as predicted by computer models, are striking more often and can be expected to intensify and become still more frequent. A future of more severe storms and floods along the world's increasingly crowded coastlines is likely.

Food Shortages

Although regional and local effects may differ widely, a general reduction is expected in potential crop yields in most tropical and sub-tropical regions. Mid-continental areas such as the United States "grain belt" and vast areas of Asia are likely to become dry. Sub-Saharan Africa where dryland agriculture relies solely on rain, yields would decrease dramatically even with a minimum increase in temperature. Such changes could cause disruptions in the food supply in a world that is already afflicted with food shortages and famines.

Dwindling Freshwater supply

Salt-water intrusion from rising sea levels will reduce the quality and quantity of freshwater supplies. This is a major concern since billions of people on earth already lack access to fresh water. Higher ocean levels already are contaminating underground water sources in many parts of the world.

Loss of Biodiversity

Most of the world's endangered species (some 25 per cent of mammals and 12 per cent of birds) may become extinct over the next few decades as warmer conditions alter the forests, wetlands, and rangelands they depend on, and human development blocks them from migrating elsewhere.

Increased Diseases

Higher temperatures are expected to expand the range of some dangerous "vector-borne" diseases, such as malaria, which already kills 1 million people annually, most of them children.

A World Under Stress

Ongoing environmentally damaging activities such as overgrazing, deforestation and denuded agricultural soils mean that nature will be more vulnerable than previously to changes in climate.

Similarly, the world's vast human population, much of it poor, is vulnerable to climate stress. Millions live in dangerous places such as floodplains or slums around the big cities of the developing world. Often there is nowhere else for the population to move. In the distant past, man and his ancestors migrated in response to changes in habitat. There will be much less room for migration in future. 

Global warming almost certainly will be unfair. The industrialized countries of North America and Western Europe, and other countries such as Japan, are responsible for the vast amount of past and current greenhouse-gas emissions. These emissions are incurred for the high standards of living enjoyed by the people in those countries. Yet those to suffer most from climate change will be in the developing world. They have fewer resources for coping with storms, floods, droughts, disease outbreaks, and disruptions to food and water supplies.

They are eager for economic development themselves but may find that this already difficult process has become more difficult because of climate change. The poorer nations of the world have done almost nothing to cause global warming yet is most exposed to its effects.

Acid Rain

Acid rain is caused by the release of SOX and NOX from the combustion of fossil fuels, which then mix with water vapour in the atmosphere to form sulphuric and nitric acids respectively.

The effects of acid rain are as follows

• Acidification of lakes, streams, and soils
• Direct and indirect effects (release of metals, For example, Aluminum which washes away plant nutrients) The killing of wildlife (trees, crops, aquatic plants, and animals).
• Decay of building materials and paints, statues, and sculptures.Health problems (respiratory, burning- skin and eyes).

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