GLOBAL WARMING

- diotima hazra

INTRODUCTION

Climate change is any long-term change in the statistics of weather over durations ranging from decades to millions of years. It can be manifest in changes to averages, extremes, or other statistical measures, and may occur in a specific region or for the Earth as a whole.In recent usage, especially in the context of environmental policy, climate change usually refers to changes in modern climate.

Global warming is the increase in the average temperature of the Earth's near-surface air and oceans since the mid-20th century and its projected continuation.

The greenhouse effect is the process by which absorption and emission of infrared radiation by gases in the atmosphere warm a planet's lower atmosphere and surface.

GREENHOUSE GASES AND EFFECT

Greenhouse gases are gases in an atmosphere that absorb and emit radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect.[1] Common greenhouse gases in the Earth's atmosphere include water vapor, carbon dioxide, methane, nitrous oxide, and ozoneGreenhouse gases greatly affect the temperature of the Earth; without them, Earth's surface would be on average about 33°C (59°F) colder than at present.[2][3][4]Human activities since the start of the industrial era around 1750 have increased the levels of greenhouse gases in the atmosphere. It is observed that changes in atmospheric concentrations of greenhouse gases and aerosols, land cover and solar radiation alter the energy balance of the climate system. In order, Earth's most abundant greenhouse gases are:

water vapor - 36–72% carbon dioxide - 9–26% methane - 4–9% nitrous oxide - (not specified)

ozone - 3–7% CFCs – (not specified)

Other greenhouse gases include sulphur hexafluoride, hydrofluorocarbons and perfluorocarbons. The major non-gas contributor to the Earth's greenhouse effect, clouds, also absorb and emit infrared radiation and thus have an effect on radiative properties of the greenhouse gases. This increase in the greenhouse gases leads to a global phenomenon known as global warming.

GLOBAL WARMING

Research work has concluded that increasing greenhouse gas concentrations resulting from human activity such as fossil fuel burning and deforestation are responsible for most of the observed temperature increase since the middle of the 20th century. However, warming is expected to continue beyond 2100 even if greenhouse emissions stop, because of the large heat capacity of the oceans and the long lifetime of carbon dioxide in the atmosphere. The most commonly cited indication of global warming is the trend in globally averaged temperature near the Earth's surface. It usually is impossible to connect specific weather events to global warming. Broader effects are expected to include glacial retreat, Arctic shrinkage, and worldwide sea level rise. Other effects may include changes in crop yields, addition of new trade routes,[62]

species extinctions,[63] and changes in the range of disease vectors.

Increased atmospheric CO2 increases the amount of CO2 dissolved in the oceans.[75] CO2 dissolved in the ocean reacts with water to form carbonic acid, resulting in ocean acidification. Since organisms and ecosystems are adapted to a narrow range of pH, this raises extinction concerns, directly driven by increased atmospheric CO2, that could disrupt food webs and impact human societies that depend on marine ecosystem services. Ocean temperatures increase more slowly than land temperatures because of the larger effective heat capacity of the oceans and because the ocean loses more heat by evaporation.

Effects on the Environment

Increasing global temperature will cause sea levels to rise and will change the amount and pattern of precipitation, probably including expansion of subtropical deserts.[7] The continuing retreat of glaciers, permafrost and sea ice is expected, with the Arctic region being particularly affected. Other likely effects include shrinkage of the Amazon rainforest and Boreal forests, increases in the intensity of extreme weather events, species extinctions and changes in agricultural yields. Some effects on both the natural environment and human life are, at least in part, already being attributed to global warming. These effects include water scarcity in some regions and increased precipitation in others, changes in mountain snowpack, and adverse health effects from warmer temperatures.

The effects of global warming are of concern both for the environment and human life. Scenarios predict that global warming will continue and get worse much faster than was expected even in their last report. Research works indicate that the effects of global warming are already largely irreversible.[2] Reports attribute many specific natural phenomena to human causes. It is suggested that glacier retreat, ice shelf disruption such as that of the Larsen Ice Shelf, sea level rise, changes in rainfall patterns, and increased intensity and frequency of extreme weather events are attributable in part to global warming.