Environmental Science topic

1. GREEN HOUSE EFFECT

2. 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

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

5. 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.

6. 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.

7. 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.

8. 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.

10. 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.

11. 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.

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

13. 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 CO
2 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

14. 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.

15. 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

16. 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.

17. 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.

18. 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
products
Turn 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.