GREEN HOUSE EFFECT

GREEN HOUSE EFFECT

The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by

atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface and the lower atmosphere, it results in an elevation of the average surface temperature above what it would be in the absence of the gases.

Solar radiation at the frequencies of visible light largely passes through the atmosphere to warm the planetary surface, which

then emits this energy at the lower frequencies of infrared thermal radiation. Infrared radiation is absorbed by greenhouse gases, which in turn re-radiate much of the energy to the surface and

lower atmosphere

The mechanism of Green house effect

The mechanism is named after the effect of solar radiation passing through glass and warming a greenhouse.

Idealised green house model

The absorbed energy warms the surface. Simple presentations of the greenhouse effect, such as

the idealized greenhouse model, show this heat being lost as thermal radiation. The reality is more complex: the

atmosphere near the surface is largely opaque to thermal radiation, and most heat loss from the surface is by sensible

heat and latent heat transport. Radiative energy losses become increasingly important higher in the atmosphere largely because of the decreasing concentration of water

vapor, an important greenhouse gas.

Greenhouse gasses

• By their percentage contribution to the greenhouse effect on Earth the four major gases are:

• water vapour, 36–70%• carbon dioxide, 9–26%• methane, 4–9%• ozone, 3–7%• 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 atmosphere.

Atmospheric gases only absorb some wavelengths of energy but are transparent to others. The absorption patterns of water vapour (blue peaks) and carbon dioxide (pink peaks) overlap in some wavelengths. Carbon dioxide is not as strong a greenhouse gas as water vapour, but it absorbs energy in wavelengths (12-15 micrometers) that water vapour does not, partially closing the “window” through which heat radiated by the

surface would normally escape to space.

EFFECTS OF GLOBAL WARMING

The effects of global warming are the environmental and social changes caused (directly or indirectly) by human emissions

of greenhouse gases. There is a scientific consensus that climate change is occurring, and that human activities are the primary driver. ]

Many impacts of climate change have already been observed, including glacier retreat, changes in the timing of seasonal events (e.g.,

earlier flowering of plants),[ and changes in agricultural productivity.Future effects of climate change will vary depending on climate change

policies and social development.]The two main policies to address climate change are reducing human greenhouse gas emissions

(climate change mitigation) and adapting to the impacts of climate change.[Geoengineering is another policy option.

PHYSICAL IMPACTS

• A broad range of evidence shows that the climate system has warmed. Evidence of global warming is shown in the graphs opposite. Some of the

graphs show a positive trend, e.g., increasing temperature over land and the ocean, and sea level rise. Other graphs show a negative trend, e.g.,

decreased snow cover in the Northern Hemisphere, and declining Arctic sea ice extent. Evidence of warming is also apparent in living (biological) systems.• Human activities have contributed to a number of the observed changes in climate.[This contribution has principally been through the burning of fossil

fuels, which has led to an increase in the concentration of GHGs in the atmosphere.[4Another human influence on the climate are sulphur

dioxide emissions, which are a precursor to the formation of sulfate aerosols in the atmosphere.

EFFECTS ON WEATHER

•Changes have been observed in the amount, intensity, frequency, and type of precipitation.

Widespread increases in heavy precipitation have occurred, even in places where total rain amounts

have decreased. With medium confidence, concluded that human influences had

contributed to an increase in heavy precipitation events at the global scale.

Projected change in annual average precipitation by the end of the 21st century, based on a medium emissions scenario

EFFECT ON WATER BODIES/OCEANS

The role of the oceans in global warming is complex. The oceans serve as a sink for carbon dioxide, taking up much that would

otherwise remain in the atmosphere, but increased levels of CO2 have led to ocean acidification. Furthermore, as the temperature

of the oceans increases, they become less able to absorb excess CO

2. The ocean have also acted as a sink in absorbing extra heat from the atmosphere.[ The increase in ocean heat content is much

larger than any other store of energy in the Earth’s heat balance over the two periods 1961 to 2003 and 1993 to 2003, and

accounts for more than 90% of the possible increase in heat content of the Earth system during these periods.[

Global warming is projected to have a number of effects on the oceans

SEA LEVEL RISE

•There are two main factors that have contributed to observed sea level rise. The first is thermal

expansion: as ocean water warms, it expands. The second is from the contribution of land-based ice

due to increased melting. The major store of water on land is found in glaciers and ice sheets.

Anthropogenic forces very likely (greater than 90% probability, based on expert

judgement)contributed to sea level rise during the latter half of the 20th century.

Effect on natural systems

Global warming has been detected in a number of natural systems. Some of these changes are described

in the section on observed temperature changes, e.g., sea level rise and widespread decreases in snow

and ice extent. Anthropogenic forcing has likely contributed to some of the observed changes, including sea level rise, changes in climate extremes (such as the number of warm and cold days), declines in Arctic sea

ice extent, glacier retreat, and greening o

Observed and expected effects on social systems

• Food: Crop production will probably be negatively affected in low latitude countries, while effects at northern latitudes may be positive or negative.[ Global warming of around 4.6 °C relative to pre-industrial levels could pose a large risk to global and regional food security.

• Health: Generally impacts will be more negative than positive.Impacts include: the effects of extreme weather, leading to injury and loss of life and indirect effects, such as undernutrition brought on by crop failures.

Solutions to stop global warming

Change a light : Replace regular bulbs with compact fluorescent light (CFL) bulbs. They consume less power then

ordinary bulbs and have longer lifetime.Drive less : By driving less you are not only saving fuel but also

helping in reducing global warming. Also, look out for other possibilities, for e.g.: car pooling. If you have colleagues who live in the same area then you can combine trips. If you need to go to a

local market then either walk or go by cycle. Both of them are great form of exercise.

Use less hot water : Buy energy saving geysers and dishwasher for your home. Avoid washing clothes in hot water. Just wash them in cold or warm water. Avoid taking frequent showers and

use less hot water. Avoid products with lot of packaging : Just don’t buy products with lot of packaging. When you buy such products you will end up in throwing the waste material in the garbage, which then will help in fillinglandfill sites and pollute the environment. Also, discourage others from buying such

productsTurn off electronic devices : Turn off electronic devices when you are moving out for a couple of

days or more. Unnecessary usage of electronic appliances will not only save fuel i.e. coal by which we getelectricity but also increase the lifetime of your gadgets.

Plant a tree : Planting trees can help much in reducing global warming then any other method. They not only give oxygen but also take in carbon dioxide, during the process of photosynthesis,

which is the main source of global warming. Spread the awareness : Always try your best to educate people about global warming and it’s causes and after affects. Tell them how they can contribute their part by saving energy that will be good for the environment. Gather opportunities and establish programs that will help you to

share information with friends, relatives and neighbors.