Atmosphere and change


Global Energy Budget


The energy balance is the balance between incoming energy from the sun and outgoing energy from the atmosphere. Energy released from the sun is in the form of shortwave light and ultraviolet energy. The earth releases long wave infrared energy.

When the sun's energy reaches the earth some is reflected back by clouds, some is absorbed or scattered by the atmosphere, some is reflected by the earth, but the majority is still absorbed by the earth.

The amount of energy reflected by the earth is affected by surfaces' albedo. We will look at the albedo of different surfaces below.

The earth-atmosphere energy balance is achieved as the energy received from the sun balances the energy lost from the earth back into space. By maintaining a balance we enjoy a stable climate.

However, by altering the balance of energy we can cause climate changes. At the moment the world is experiencing global warming which is believed to be caused by the increase amount of greenhouse gases in the atmosphere causing more reflected and released energy to be trapped in the earth's atmosphere.
external image trenberth-color-best.jpg
Below is a summary of some of the factors that can change the balance between incoming and outgoing radiation:

Desertification: The impact of desertification can be dependent upon the type of sand. Very white sands have quite a high albedo whereas darker sands have a much lower albedo. Desertification caused by deforestation normally leaves dark sands/soils and therefore a low albedo with lots of radiation absorbed. However, it must also be remembered that vegetation produces shade which reduces the amount of radiation reaching the ground and therefore reduces ground temperatures. The processes of evaporation and transpiration can also reduce temperatures.

Melting ice caps: Melting ice caps and glaciers could change the earth's albedo drastically and increase the amount of incoming solar radiation absorbed. Pure white snow has one of the highest albedos (95%), if this replaced by water or rock then albedo is reduced and more incoming radiation absorbed, raising temperatures.

Particulates (pollution) in atmosphere: Pollution in the atmosphere can increase the amount of incoming radiation reflected, scattered and absorbed, therefore reducing the amount reaching earth. However, pollution can also change the albedo of surfaces like white snow, increasing the amount of incoming solar radiation absorbed by the earth.

Global Dimming - BBC article

Volcanoes: Large volcanoes can release massive amounts of ash into the atmosphere, increasing the amount being absorbed, reflected and scattered in the atmosphere, therefore reducing the amount reaching earth. However, volcanoes can also release large amounts of sulphur dioxide which is a greenhouse gas, therefore trapping in more outgoing solar radiation.

Volcanic Climate Change - Unlikely say experts - BBC article

Cloud cover (artificial or natural): Like with volcanoes and particulates increased cloud cover does reflect, scatter and absorb more incoming solar radiation in the atmosphere and prevent as much from reaching the earth's surface. However, it can also act as a blanket keep some outgoing radiation in the atmosphere.

Solar flares: Although solar activity from the earth changes it has no noticeable impact on the amount of incoming radiation. More damaging impacts can be to transport and communications (read article below).

Solar Flare Eruptions Set to Reach Earth - BBC article

Greenhouse gases: Greenhouse gases allow solar radiation into the atmosphere, but stop some outgoing radiation being released from the atmosphere and reflect it back to earth. This is increases the amount of radiation being absorbed by the earth and is known as the greenhouse effect.

Deforestation: Like desertification, although soil may have a similar albedo to dark trees they do cool temperatures because they act as a source of shade and cool temperatures through evaporation and transpiration.

Albedo

Albedo means how reflective a surface is. If a surface has a high albedo then more of the sun's energy is reflected. Fresh snow has one of the world's highest albedos, reflecting up to 95% of the sun's energy. Darker surfaces like tarmac roads have a much lower albedo, only reflecting about 5% of the earth's energy.

Because snow and ice have relatively higher albedos it is important that we try and protect them. If snow or ice melts and is replaced by rock or dark vegetation then more of the earth's energy will be absorbed rather than reflected. These changes in the energy balance will cause even more warming and probably more melting creating a spiral of melting and warming. Not only is the melting of ice is bad, but also the polluting or dirtying of it is too. If snow gets dirty then it is darker and more likely to absorb rather than reflect.
Dity Snow Reduces its Albedo
Dity Snow Reduces its Albedo
Deforestation can also lead to changes in the albedo. Even though dark vegetation has a low albedo, it is still higher than rock or soil. Therefore if we deforest more of the sun's energy will be absorbed. The energy that is reflected also has a higher change of being trapped by the atmosphere because less photosynthesis will be taking place and there will be more carbon dioxide in the atmosphere enhancing the greenhouse effect.

external image ill_maps-Albedo-Effect.jpg
external image albedo.jpg

Can Painting A Mountain Restore A Glacier - BBC article

Global Warming and the Greenhouse Effect

The greenhouse effect is a natural process and one that is vital to the existence of humans. Without the greenhouse effect the earth will be significantly colder and unable to support large scale life. The greenhouse effect acts as a kind of blanket. As energy is reflected or released by the earth it moves into the atmosphere where it is trapped and reflected back by a layer of greenhouses gases. The reflected energy returns to earth and is absorbed warming global temperatures. The problem of global warming is caused by humans enhancing the greenhouse effect. We are releasing more greenhouse gases into the atmosphere which is trapping an ever increasing amount of reflected or released energy which returns to earth and warms us further.

Greenhouse gasses (GHG): Any gas that absorbs and emits radiation in the thermal infrared range. The gases include: Carbon monoxide, carbon dioxide, methane, sulphur dioxide, Nitrous Oxide, water vapour and ozone.

Sources of greenhouse gases include:
  • Transport (cars and planes)
  • Animals (cow release large amounts of methane)
  • Burning fossils fuels (especially oil and coal)
  • Melting Permafrost (methane is released when permafrost melts)
  • Industry
  • Domestic use (wood fires)
external image global-warming-4.gif
Everything you need to know about climate change - interactive - Guardian



Problems Caused By Global Warming


Rising Sea Levels: This is probably the best known impact of global warming, Rising sea levels itself will cause many impacts like loss of land, climate refugees and changes in ecosystems. Most of the related problems are looked at individually below.

Coastal Flooding (cost of defences): Protecting coastlines is an expensive business and one that needs continually to re-assessed. The sea is a powerful force and can destroy or breach even the strongest defences. In addition as sea levels rise, some defences become too small, it is believed that the Thames Flood Barrier designed to protect London will have to be enlarged in the future at enormous cost.

Ministers Plan New Thames Barrier as Flood Risk Rises - Independent article

Climate Refugees: As sea levels rise more and more people who live on the coast will lose their homes and have to be relocated. Some richer countries might be able to protect their populations, but low lying countries like the Maldives and poor countries like Bangladesh will see a rapid increase in climate refugees.



Climate fears for Bangladesh's future - BBC article

Climate change migration warning issued through report - BBC article

Loss of Biodiversity: As temperatures warm and sea levels rise, the habitats of many plants and animals will alter. Although some animals may be able to migrate to new areas, other plants and animals will lose their habitats forever and become extinct. The most talked about is probably the polar bear, but coral reefs will see some of the biggest changes and losses of biodiversity.

Global Warming Has Devastating Effect on Coral Reefs - National Geographic

Changes in the Gulf Stream: Much of NW Europe is currently warmer than areas at similar latitude. The reason that the NW of Europe (and in particular the UK) is warmer is because of the Gulf Stream (or conveyer belt) which moves warm water from the Gulf of Mexico to Europe. This warm water warms NW Europe and protects it from cold winters. However, one of the less well-known impacts of climate change is a mini ice age in NW Europe. The Gulf Stream works because just south of Iceland the warm water sinks and returns south. The reason the Gulf Stream sinks is because of the salinity (density) of the water. Permafrost melting in Northern Russia and ice shelf melting on Greenland is changing the salinity of the water in the area. Scientists believe that the salinity of the water might fall so much that the warm water stops sinking and therefore stops the Gulf Stream. If this happens then NW Europe will begin to cool as it stops receiving the warm waters of the Gulf Stream
external image q15.jpg

Desertification: Rising temperatures and reduced rainfall will mean that some areas of the world will see increased rates of desertification. Although much of the world's desertification is caused by human factors reduced rainfall and warmer temperatures will mean that some vegetation will find it harder to survive.

Loss of Industry: Coastal industries like tourism and fishing will be effected as sea level rise and destroy holiday resorts (or even whole islands) and engulf fishing ports and communities.

Flash Floods: Rising temperatures will not mean that everywhere gets drier and warmer. It might mean some places get cooler and it will certainly mean some place get wetter. Melting ice sheets, permafrost and glaciers will mean more water is released from its storage. Rising temperatures will in turn mean more water is evaporated into the atmosphere. The atmosphere can only hold so much water before it becomes saturated and rains. Because of the amount of evaporation rainfall (especially convectional) will become more intense and cause more flash floods.

Increased Tropical Storms: Some scientists believe that warming temperatures are increasing the magnitude and frequency of tropical storms. Tropical storms receive their energy from the sea. For a tropical storm to develop and strengthen it needs warm seas so with global warming causing sea temperatures to rise it might be increasing the number of tropical storms.

Warming Link to Big Hurricanes? - BBC article

Heatwaves and Forest Fires: Increasing temperatures will cause heatwaves in an increasing number of countries, including countries that are not prepared for the heat e.g. France where an estimated 14,800 died in the 2003 heat wave. Also Hot temperatures can dry out vegetation and increase the risk of forest fires (both natural and man made).

Over 11,000 dead in French Heat - BBC article

Melting Permafrost: Permafrost is ground that contains permanently frozen water. As global temperatures rise permafrost can begin to melt. The melting permafrost not only releases large amounts of methane in the atmosphere increasing the greenhouse effect, but also releases freshwater into the seas which may affect some of its ocean currents.

Methane Release Looks Stronger - BBC article

Arctic melt releasing ancient methane - BBC article

Droughts and Famines (crop failure): As global temperatures rise some areas of the planet will become more arid (drier). As areas become more arid there will be increasing water shortages and crop failures leading to drought and famine. Areas that will be badly affected include the Sahel (the area south of the Sahara Desert), where growing populations are putting ever increasing pressure on existing resources.

Warming to leave tropics hungry - BBC article

Amazon drought severe in 2010 raising warming fears - BBC article

Skin Cancer (diseases): Exposure to the sun's UV rays can cause increases in skin cancers and other diseases like eye cataracts. Areas that are particular badly hit are countries like Australia that have also seen damage to the Ozone Layer.

Cricketers get Skin Cancer Tests - BBC article

Is Global Warming a Natural Event?


Some scientists believe that humans are not causing the current period of global warming and that the earth naturally goes through periods of warmer and cooler conditions. Three theories put forward to support this are below:

Earth's Orbit (Milankovitch Cycle)


Milankovitch Theory describes the collective effects of changes in the Earth's movements upon its climate, named after Serbian civil engineer and mathematician Milutin Milanković. Milanković mathematically theorised that variations in eccentricity, axial tilt, and precession of the Earth's orbit determined climatic patterns on Earth.

The Earth's axis completes one full cycle of precession approximately every 26,000 years. At the same time the elliptical orbit rotates more slowly. The combined effect of the two precessions leads to a 21,000-year period between the seasons and the orbit. In addition, the angle between Earth's rotational axis and the normal to the plane of its orbit, obliquity, moves from 22.1 degrees to 24.5 degrees and back again on a 41,000-year cycle; currently, this angle is 23.44 degrees and is decreasing.

external image 620px-MilankovitchCycles.jpg
external image Cycles2.jpg

Solar Output


Solar variation refers to changes in the amount of total solar radiation. There are periodic components to these variations, the principal one being the 11-year solar cycle (or sunspot cycle). Solar activity has been measured by satellites during recent decades and estimated using 'proxy' variables in prior times. Scientists studying climate change are interested in understanding the effects of variations in the total and spectral solar irradiance on the Earth and its climate.

Solar flare eruptions set to reach earth - BBC article
external image normPage-19.jpg

Meteors and Volcanoes


Volcanic eruptions can alter the climate of the Earth for both short and long periods of time. For example, average global temperatures dropped about a degree Fahrenheit for about two years after the eruption of Mount Pinatubo in 1991, and very cold temperatures caused crop failures and famine in North America and Europe for two years following the eruption of Tambora in 1815. Volcanologists believe that the balance of the Earth's mild climate over periods of millions of years is maintained by ongoing volcanism. Volcanoes affect the climate through the gases and dust particles thrown into the atmosphere during eruptions. The effect of the volcanic gases and dust may warm or cool the earth's surface, depending on how sunlight interacts with the volcanic material.

Meteors can have very similar effects to volcanoes. Large meteor strikes can throw large amounts of ash into the atmosphere altering the amount of incoming radiation. A meteor strike in the Yucatan Peninsula is blamed for the extinction of the dinosaurs.
external image halleyscomet.jpg
Some of the above explanations are courtesy of : www.wikipedia.com

Possible Solutions to Global Warming


Mitigation: Trying to reduce the effects of something happening.

Adaptation: Changing lifestyles to suit new conditions.

  • Renewable Energy: By using more renewable energy like HEP, wind, geothermal and solar and less fossil fuels (especially coal and oil) the amount of greenhouse gases should reduced. Renewable energy can be on a house to house basis with houses either been fitted with solar panels or wind turbines, or larger scale renewable sites could be developed. Nuclear energy also releases minimal greenhouse gases, but there are other safety issues associated with this type of power e.g. Chernobyl and Fukushima
  • Hybrid Cars: Car manufacturers are increasingly making cars that are more environmentally friendly. The Toyota Yaris is a hybrid car which runs of a combination of conventional fuel and electricity. As charging becomes quicker and charge points more widespread, the amount of hybrid and electric cars should increase, reducing the amount of greenhouse gases released. However, it must be remembered that too make electric cars sustainable, the energy to charge the cars must come from a sustainable source.
  • Reduce, Reuse, Recycle: If we started to use less electricity (energy saving light bulbs, power saving devices), reduce the amount of packaging and recycle, less energy will be used and therefore less greenhouse gases will be released into the atmosphere.
  • Afforestation and Reforestation: By replanting trees and reducing the rate of deforestation we can maintain and hopefully increase the rate of photosynthesis removing carbon dioxide from the atmosphere.
  • Carbon Sequestration: This is the capture of carbon dioxide from the atmosphere or emission chimneys. Different methods of carbon capture and storage have been suggested including the use of algae in the oceans and empty aquifers underground. Will Carbon Capture Work - BBC article
  • International Agreements: International agreements like the Kyoto Protocol that came into force in 2005 (minus a US ratification) should help limit the amount of greenhouse gases being released into the atmosphere.
  • Build More Sea Defences: Build bigger and better sea defences to cope with rising sea levels. It might be necessary to allow managed retreat on some sections of the coast, but sea walls, rip-rap, breakwaters, etc. can be built along more high value sections.
  • Air con and/or Heating: As countries get either hotter or colder houses can be built with either air-con to cool inhabitants or heaters to warm inhabitants. However, it must be noted that this form of adaptation will probably require even more adaptation in the future because using air con and/or heating can release large amounts of greenhouse gases in the atmosphere.
  • Improved Meteorology: Global warming will increase the frequency and severity of flooding, heatwaves and tropical storms. Therefore it will be necessary to predict and track these events so that populations can be warned and therefore prepare.
  • Disease Treatment: If the strength of the sun's rays intensify diseases like skin cancer and eye cataracts will increase. We will have to improve prevention (slip, slap, slosh) and improve treatment.
  • Desalination: Rising sea levels will reduce the amount of freshwater as glaciers and permafrost melt and saltwater intrusion pollutes aquifers. Therefore it will be necessary to source alternative water sources like desalinating saltwater.
  • Resettlement: Rising sea levels will create climate refugees in countries like the Maldives and Bangladesh. It will either be necessary to move these people to other countries or to higher/safer locations within the country.
Climate Talks End With Late Deal - BBC article

Farming needs 'climate-smart' revolution, says report - BBC article

Are there any Positive Impacts of Global Warming?


Improved Arctic Navigation: Global warming will mean that the amount of Arctic ice steadily decreases. As the ice melts navigation across the North Pole will become safer and quicker. Trade between Scandinavia, Russia, Canada and US will all be a lot easier.

Increased Agricultural Land: As permafrost melts and temperatures start to rise it will be possible to grow more crops on more land. With a rising global population this might be vital in the fight to reduce global famine.

Reduction in Cold Deaths: Old, young and sick people are very vulnerable to the cold. If global temperatures start to rise then latitudes further north and south will become more hospitable and less people will die from the cold.

Release of Freshwater: Currently a lot the world's freshwater is held in glaciers or as permafrost. As global temperatures rise, we might be able to capture and use some of this freshwater to reduce the effects of drought.

Accessibility of Resources: It is believed that places like Greenland, Alaska, Siberia and Antarctica contain a lot of resources (oil, gas, etc.). As global warming causes large areas of ice to melt they will become more accessible for human exploitation.

Arctic seabed 'belongs to Russia' - BBC article

Reduced Heating: If global temperatures rise people will have to heat their properties less. Not only will this save money but it will also reduce the demand for gas and electricity and therefore reduce the amount of greenhouse gases being released.

Recommended Wider Reading and Viewing


Carbon capture 'viable with long-term support' - BBC article