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3.1.1.4 Climate Change, Rising Temperatures, Fluctuating Temperatures…
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Deforestation, which increases the amount of CO2 in the atmosphere.
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Average global sea level has risen by 21-24cm since the 1800s, and a third of this rise has occurred in the last 25 years.
Sea level rise has been occurring because higher temperatures have caused glaciers and ice sheets to melt, and this freshwater then flows into the sea.
Water expands when it gets warmer, which is known as thermal expansion, so as the earth warms, sea level is expanding and rising.
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These orbital changes affect where the sun hits the earth, and how intense the sun is, which controls the seasons and affects the climate.
Volcanic eruptions have had an effect on the earths Climate in the past. The ash and gas that is erupted into the atmosphere can cause a cooling effect on the Climate.
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A variation in solar output is the sunspot cycle. The sunspot cycle is an 11-year cycle where the amount of them on the suns surface varies from a minimum to a maximum, then back to a minimum.
At the minimum, there is reduced solar output. At the maximum, there is enhanced solar output.
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The Greenhouse effect is a natural process where gases trap the solar energy from the sun inside the atmosphere, which heats the earth.
In a greenhouse, the Sun shines through the glass, which causes the greenhouse to heat up. This heat cannot escape as it is trapped by the glass which keeps it warm inside.
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Some of this heat is trapped by the greenhouse gases, which keeps our earth warm.
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Human activities release greenhouse gases into the atmosphere at a higher rate than natural processes, which resulted in the enhanced greenhouse effect.
As there are higher amounts of gases in the atmosphere, more heat is trapped and cannot escape into space. This heat is reradiated around the earth causing the air to heat up more and more. This process has lead to increased warming in recent years.
The main human activities that have caused an increase in greenhouse gas levels in the earth's atmosphere are outlined below
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Fossil fuels - such as coal, oil and gas - are fuels that are made up of the remains of organic material. We burn fossil fuels for energy, which produces electricity, fuel for our cars and heats our homes
When fossil fuels are burnt, greenhouse gases are released, such as carbon dioxide, nitrous oxides and methane. These greenhouse gases concentrate within the atmosphere, contributing to the enhanced greenhouse effect.
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Agricultural activities produce a lot of methane. Methane is a more effective greenhouse gas than carbon dioxide, so it is better at trapping heat. About 25% of global warming is thought to be caused by methane emissions, despite their being much less methane in the atmosphere than carbon dioxide.
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In a paddy field, a flooded field where they grow rice, has the right conditions to release a lot of methane. As rice is heavily cultivated across the world, rice farming is a large contributor to the levels of methane in the atmosphere.
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Some farm animals, such as cows and sheep, produce methane when they digest food. One of these animals on average produces 250 - 500 litres of methane a day.
Animals are kept all over the world as livestock to meet population's demand for meat and animal products, which contributes to huge methane emissions.
Agricultural fertilisers also produce nitrous oxides, which can be up to 300 times more effective in capturing heat than carbon dioxide.
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Deforestation is the process of cutting down trees. It occurs all over the world, mainly to make space for agriculture, or to collect wood to use for other means or to burn as fuel.
Trees take in carbon dioxide from the atmosphere and store it inside them as carbon. Deforestation removes large amounts of trees which means that the carbon stored inside them is released into the atmosphere.
Forested areas are burnt to make space quickly, and wood is also chopped and burnt for fuel causing further release of carbon dioxide.
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Emissions of greenhouse gases due to human activities is thought to be a bigger influence on current global warming than natural causes of climate change.
Average global temperatures are projected to increase by as much as 4 degrees by the ed of the century due to human activities.
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In order to live with the effects of climate change, society is finding new ways to manage these effects. In general, there are two approaches of managing climate change
- Mitigation - Reducing the causes of climate change, so that climate change slows or even stops. This management strategy is mainly coming up with ways to reduce greenhouse gas emissions.
- Adaptation - Responding to climate change by coming up with ways to live and cope with the effects. This is mainly by reducing the risks associated with climate change, like building flood defenses to manage sea level rise.
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Carbon capture and storage, CCS, is the process of capturing carbon dioxide that would usually be emitted from fossil fuel brining, and storing it underground in reservoirs
CCS is a developing technology, but has the potential to reduce greenhouse gas emission massively. Up to 90% of carbon dioxide from industry and electricity generation could be stored in this way.
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Furthermore, trees also release moisture into the atmosphere, producing clouds which reflect solar radiation.
However, planting trees alone would not absorb all of the carbon dioxide we emit, so although it is a helpful strategy it cannot be used as the only solution to reduce greenhouse gases
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Climate change is predicted to affect agricultural systems all over the world. Even if we reduce greenhouse gas emissions, it is likely that there will be changes in the climate.
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Rainfall/temperature patterns will change, which will make some areas more suitable for agriculture, but others less suitable.
Extreme weather events, such as droughts, floods and heatwaves are expected to become more frequent. This means farmland will be destroyed and crops might fail more frequently.
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With predicted changing patterns of rainfall and the projected increase in extreme weather, water supplies are under threat in many places around the world. Countries will need to manage their water supplies so that enough water is available for the population. Strategies are included below.
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By 2100, sea levels are expected to rise anywhere from 26-82cm. This sea level rise will have massive implications on coastal areas, and there is a severe risk of very significant coastal flooding. This also threatens freshwater supplies, as they may become contaminated by seawater.
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- Construction of flood defenses such as sea walls, or the use of sandbags to physically stop seawater.
- Housing built on stilts so they are raised off the ground, which will stop properties flooding.
- Designated areas are unsafe to live and redistributing populations to other areas.
- Constructing areas that are high above sea level.
- Restoration of mangroves - mangroves are shrubs that can trap sediment and slow water flows with their thick roots. Many countries are deciding to restore mangrove forests because they are natural flood defenses.