Climate Change and its Drivers

Despite its huge complexity Climate Change components can be broken down in to smaller constituent parts and more readily understood

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The climate system is often considered to consist of five main sections:

• the atmosphere
• the hydrosphere – oceans, rivers and lakes
• the cryosphere – snow and ice cover
• the biosphere – the global sum of all living things
• the geosphere – rock, soil and the land surface

Trees and other plants use carbon dioxide to live and grow. Hence they are important in removing carbon dioxide from the atmosphere, that is, they form a carbon sink. When areas of forest are removed (`deforestation'), this carbon sink is removed and amounts of atmospheric carbon dioxide will remain higher than they otherwise would have been

Essentailly the Earth receives more energy from the sun at low latitudes so that’s near the equatorand less at the cold Poles. So the atmosphere is heated differentially and gets warmer at the Equator and colder at the Poles. Associated with that are then changes in pressure between the Equator and the Poles and that drives the atmosphere to circulate for the air to move in the atmosphere, that drives thewhole atmospheric circulation. The atmosphere essentially behaves very broadly speaking as a giant heat pump which is continuously trying to move heat away from the Equator and towards the Poles.

The other climate forcing is volcanic activity because volcanic eruptions release large quantities of gases and particles into the atmosphere where they’re very good at backscattering the solar radiation that’s coming from the sun. So sunlight from the sun gets backscattered by the particles that volcanic eruptions put into the atmosphere. So generally speaking these lead to a cooling of the climate system although their effect is relatively short lived.

The most talked about way in which climate can be altered is the way that mankind is affecting the composition of the atmosphere by adding in particular the gas carbon dioxide to the atmosphere. Since we began to become industrialised in about 1750 we know that because we’ve been burning so many fossil fuels - that’s coal,oil and gas - to meet our energy needs for transport. So mankind has significantly increased the amount of carbon dioxide in the atmosphere since the onset of industrialisation and via the enhanced greenhouse effect

Water vapour is a strong greenhouse gas so as climate warms and we evaporate more water into water vapour we potentially warm the climate system even further because it’s a strong greenhouse gas. So there’s the, a sort of vicious circle threat what we call the positive feedback and warmer air can hold more water vapour than colder air as well. So there’s the potential for that to feed back on itself in a positive way. The other main thing to consider with the hydrological cycle is the changes to cloudiness along with this increased vigorousness of the hydrological cycle. We expect generally to see an increase in cloudiness with more water evaporated and recondensing to form clouds

Generally speaking high clouds are good at trapping long wave radiation that’s coming out from below so generally speaking high clouds tend to have a warming effect on the climate. On the other hand low clouds are better at reflecting the sun’s radiation back to space so they tend to have a cooling effect on climate

When we remove large areas of forest we remove what’s called a carbon sink because trees and plants use carbon dioxide from the atmosphere to live and grow. So they’re important in removing carbon dioxide from the atmosphere. Secondly when we clear the forest away we change what’s called the surface reflectance which as the name suggest is essentially just a measure of how reflective the surface is. Generally speaking dark-coloured surfaces such as evergreen forest absorb more solar radiation than light coloured surfaces such as desert or light coloured concrete. So if we remove areas of dark forest and replace them with lighter-coloured areas then we actually increase the reflectiveness of the surface and reflect more of the sun’s rays back to space.

And one other final influence of or effect of removing forest is that essentially we change what’s called the roughness length. That’s a measure of how the roughness of the very lowest level of the atmosphere lying on the surface that basically what that means is that basically affects turbulence and the way that weather systems form at very low levels

One of the ways in which that could be changed is that as climate alters and more rain falls in one place than another you could see a freshening of seawater which will ultimately lead to changes in the way the ocean circulates.

Changes in atmospheric temperature

• Melting of glaiciers that raise sea level

Changes in differential heating (latitudinal/longitudinal

• Changes in tracks of weather patterns such as the continental drift

Changes in solar output

• Increase snow melt reflects less heat back causing further warming

===Changes ibn land use- e.g deforestation

• impacts carbon sink
• impacts solar radiation and reflection
• changes habitat
• affects roughness length - which affects turbulence and weather patterns

Changes in solar and volanic activity

• Are Climate forcings that effect climate withour being affected by it. ash for instance can backscatter radiation back into the atmosphere

Changes in soil moisture

• affects biosphere

Changes in human influences

• Increased ozone which is a pollutant in the troposphere
• Suplate and aerosols can cause back scattering which cool atmosphere

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References

File:Componentsoftheclimatesystem.pdf