PHYSICS ASSIGNMENT
TANU SHARMA
18BCE10278
Greenhouse gases are gases in Earth’s atmosphere that trap heat. They let
sunlight pass through the atmosphere, but they prevent the heat that the
sunlight brings from leaving the atmosphere. Where do greenhouse gases
come from? How do we know what is happening to concentrations of
greenhouse gases in the air?
Most of the increase in carbon dioxide comes from burning of fossil fuels such
as oil, coal and natural gas for energy, and from deforestation.
Cows, sheep and other ruminant animals ‘burp’ methane into the air. Rice
paddies also generate methane. Other sources of methane are landfills,
burning vegetation, coal mines and natural gas fields.
Nitrous oxide concentrations are increasing because of changes to the way in
which we use land, from fertiliser use, from some industrial processes, and
from burning vegetation.
Ozone is a component of photochemical smog, which, in turn, is the result of
emissions of hydrocarbons and nitrogen oxides from motor vehicles and
industry.
CFCs were made in the past for refrigerants, spray pack propellants, producing
foam plastics and as solvents for electronic components. All developed
countries, including Australia, have stopped producing CFCs.
Atmospheric CO₂ and CH₄ concentrations
While satellite data are used to monitor the atmospheric concentrations of
carbon dioxide (CO2) and methane (CH4), accurate satellite measurements of
nitrous oxide (N2O) are currently not possible. Although all three gases are
monitored through in situ measurements, here the focus is on satellite-derived
information.
Carbon dioxide
The atmospheric concentration of CO2 is increasing at an average rate of
approximately 0.6%/year. This increase is mainly due to CO2 emissions from
the burning of fossil fuels (oil, coal and natural gas). While CO2 concentrations
vary in space and time, they are increasing across all areas of the globe. Levels
fluctuate within each year, primarily due to regular seasonal uptake and
release by vegetation, through photosynthesis, respiration, and decay of
organic matter. The fluctuations are largest over the Northern Hemisphere,
where most of the planet’s terrestrial vegetation is located.
The largest value of XCO2 recorded until the end of 2019 was in May 2019 over
the Northern Hemisphere, at approximately 413 ppm. The increase across the
whole of 2019 was 2.7 ± 0.8 ppm. This was larger than the growth in 2018,
which was 2.1 ± 0.5 ppm, but less than the increase of 2.9 ± 0.3 ppm in 2015.
In 2015 there was a strong El Niño event that resulted in a larger growth rate
of atmospheric CO2 due to a weaker than normal uptake by terrestrial
vegetation; there were also large CO2 emissions from wildfires, for example in
Indonesia.
Methane
Like CO2 described above, levels of CH4 also vary in space and time. The value
of XCH4 was nearly constant between 2003 and 2006, but has been increasing
since 2007 at a rate of about 8 ppb/year (approximately 0.4%/year). The
reasons for this observed trend are not yet clear, but could be due to changing
CH4 emissions into the atmosphere, or due to changes in processes that
remove CH4 from the atmosphere. Emissions are either anthropogenic (e.g.
from the production and burning of fossil fuels, or from agricultural processes)
or natural (e.g. from wetlands). The main removal mechanism of CH 4 from the
atmosphere is the reaction with the atmospheric hydroxyl (OH) radical. The
changes in concentration of OH are difficult to measure outside of dedicated
field campaigns with advanced ground-based or airborne sensors, so it is
difficult to precisely quantify the chemical sink for methane.
A warming atmosphere affects more than just air temperatures: while heat
waves and droughts are becoming more common and intense, rainstorms are
also becoming more powerful, sometimes provoking dangerous floods.
Which sphere is contributing more toward climate change? Troposphere,
stratosphere, mesosphere or ionosphere? Explain it.
Troposphere
The troposphere is the layer of the atmosphere located closest to sea level,
only between 7 and 20 kilometres. It is the place where all meteorological
phenomena, climate and weather occur. It is important because it is in this
place where there are higher levels of oxygen needed to survive.
Troposphere characteristics
It is in this atmospheric layer that meteorological phenomena such
as wind, rain and snow occur. Every time the sun warms the ground, the hot
air rises. From this moment the water evaporates and rises with the hot air to
colder heights. Because the cold air cannot absorb all the water, it condenses
into clouds. When the Tropopause is reached, the water and air cease to rise
and rain, snow or hail form.
It is in the troposphere where we find the highest oxygen and water vapor
concentration that makes possible biosphere life, place in which all living
beings have the capacity to develop. It is a temperature regulator for earth.
Without the troposphere, the thermal differences between day and night
would make life impossible. This characteristic is one of the most important for
living beings. This is the place where the well-known Greenhouse Effect occurs
thanks to the presence of gases such as carbon dioxide and water vapor, which
are responsible for absorbing infrared radiation from the sun and 88% of it but
is emitted by the earth. The solar rays pass through the troposphere and
become “trapped”, causing the earth’s temperatures to be suitable to inhabit
it.
Is in this layer where the airplanes fly. They have to pressurize their cabins due
to the lack of oxygen and the cold at the height of the flight. The troposphere is
the thinnest layer of the atmosphere, but at the same time it is where the
most turbulence is found.
Why troposphere is responsible for Climate change?
This layer extends between 5 to 9 miles (8 to 14 kilometres) depending
on which part of the Earth you are looking at. In colder regions, like the
north and south pole, the troposphere is thinner.
It contains three-quarters of the mass of the Earth’s atmosphere and is
composed of 78% nitrogen, 21% oxygen, and a 1% mixture of argon,
water vapor, and carbon dioxide.
Air at the bottom of the troposphere or near the Earth’s surface is
warmer, which means the higher the altitude, the colder it is.
Due to its composition of water vapor and dust particles, most clouds
form in this layer. Water vapor is greatest above the tropics and least in
the polar regions.
This layer is heated from the ground or ocean. Sunlight warms the
ground or ocean, which eventually radiates the heat into the air above
it.
Tropopause is the boundary separating troposphere and stratosphere.
Its height depends on the season, latitude, and whether it’s day or night.
During winter the poles’ tropopause is lower – about 7 km high – and it’s
about 20 km near the equator.
The vertical transport of heat in the troposphere is called convection,
while advection refers to the horizontal heat transfer.
In densely populated areas, smog in the troposphere is commonly
present. This feature is produced when pollutants accumulate close to
the surface, plus a series of chemical reactions.
The water cycle or exchange of water between the Earth and the
atmosphere also occurs in the troposphere.
The water cycle in the troposphere begins when the sun evaporates
water from the surface and gets transported to other regions by the
wind. Air rises, expands, cools, condenses, and develops clouds.
When liquid or solid particles collected are large enough in size, they fall
towards the surface of the Earth as rain, snow, or sleet as precipitation,
dependent on the air temperature.
Despite their fluffy and cotton-like appearance, clouds are not
weightless. A cloud is formed from a group of tiny water droplets in the
air during the process of condensation.
While most clouds form in the troposphere, some can be seen as high in
the stratosphere or mesosphere. Some of the main types of clouds
include stratus, cumulus, and nimbus. Stratus clouds are characterized
by their horizontal layered sheets and grey or white color. They are the
lowest lying cloud type, which are often seen as mist or fog. This type of
cloud is accompanied by light drizzle and snow if the temperature is cold
enough.
Cumulus clouds are like cotton floating in the sky, usually seen in fair and
sunny weather conditions. They can grow into towering cumulonimbus
thunder clouds which produce rain showers.
The high hair-like clouds are called cirrus clouds. They are the whitest
clouds during day time and are often associated with a change in
weather.
In the first 500 meters of height in the troposphere, vertical, upstream,
and downstream currents occur. These help in recycling air, dispersing
pollutants, and the suspension of dust which causes the reddish color of
the sky at dusk and dawn. It is commonly known as the dirty layer.
Due to a high concentration of oxygen and water vapor in this layer, all
living creatures can develop and survive.
Greenhouse effect also occurs in the troposphere. The solar rays from
the sun are trapped in this layer which warms the temperature and
makes life possible.
In addition to being the thinnest layer of the atmosphere, it is also the
most turbulent. This is the layer where planes can fly, but the cabins
must be pressurized due to lack of oxygen and extremely low
temperature. This is the same reason why mountain climbers carry
bottles of oxygen in high altitude courses.
The troposphere regulates temperature and produces weather. Weather
encompasses all short-term atmospheric phenomena on Earth, while
climate usually lasts significantly longer periods, like seasons that last a
quarter of a year.
Change in weather is generated by many factors including air, sunlight,
mountain, and clouds. Despite its dynamics, weather can be predicted
through forecasting. For average people, weather forecasting can be
done by observing the type of clouds and their movement. While
professional forecasters use a variety of tools, like balloons and radars
set up in weather stations.
All weather phenomena, including hurricanes, tornadoes, thunderstorms,
typhoons, cyclones, and snow occur in the troposphere.
