Biology Unit 4 Climate Change

• When radiation from the sun hits the earth, it is radiated back from the earth's surface 
• A greenhouse gas is a gas that absorbs this re-radiated radiation, trapping it in the earth's atmosphere so that it is not lost to space
• The greenhouse effect is important to ensure that Earth is warm enough for life
• If it were not for the insulating effect of greenhouse gases, Earth would see similar dramatic temperature fluctuations to its neighbouring planets
• here are many greenhouse gases including carbo dioxide and methane
• Increasing levels of carbon dioxide and methane are entering the atmosphere as a result of human activities, leading to increased rates of atmospheric warming
• The atmospheric warming, and therefore the changing climate, for which humans are thought to be responsible is known as anthropogenic climate change
• Atmospheric carbon dioxide levels have fluctuated throughout Earth's history due to events such as volcanic eruptions and the weathering of limestone rocks
• In addition to the burning of fossil fuels, carbon dioxide is also released into the atmosphere when natural stores of carbon are damaged or destroyed by human activities
• Carbon stores are known as carbon sinks
• Carbon sinks include trees, soils, peat bogs, and the oceans
• Deforestation, soil degradation, peat harvesting, and ocean warming all contribute to the addition of carbon dioxide to the atmosphere
• Methane (CH4) is a simple hydrocarbon
• Methane is present as a gas in the atmosphere, and underground, and is the main component of natural gas fossil fuel
• Methane can be produced by naturally occurring processes in some types of bacteria and several human activities
• Landfill sites release methane when organic matter such as food waste decomposes
• Extraction of fossil fuels from underground releases methane
• Anaerobic bacteria in waterlogged rice paddy fields release methane
• The warming of the poles that results from global warming also leads to the release of methane from natural stores such as permafrost
• Permafrost is ground that remains frozen all year round
• Global warming refers to the rise in global temperatures mainly due to the increasing concentrations of greenhouse gases in the atmosphere
• Climate change refers to the increasing changes in the measures of climate over a long period of time – including precipitation, temperature, and wind patterns. These are often a consequence of global warming
• The greenhouse effect is a naturally occurring event, constantly occurring due to the atmosphere and sunlight
• Positive feedback is any mechanism in a system that leads to additional and increased change away from the equilibrium
• Positive feedback loops occur when the output of a process feeds back into the system in a way that moves the system increasingly away from the average state
• Positive feedback is destabilising; it amplifies deviation from the equilibrium and drives systems towards a tipping point where the state of the system suddenly shifts to a new equilibrium
• Global warming has a positive feedback effect on the earth and its atmosphere
• The extent to which a surface reflects light is known as its albedo; the higher the albedo, the more light is reflected
• As the polar ice caps melt due to global warming, the earth's overall albedo decreases, and more of the sun's energy is absorbed by exposed rock, soil, and the dark surface of the oceans; this increases global warming
• Decomposition is carried out by living organisms such as bacteria and fungi
• Bacteria and fungi break down dead matter and waste in a series of enzyme-controlled reactions
• The enzyme-controlled reactions of decomposition occur faster at higher temperatures, meaning that as global warming increases, rates of decomposition increase 
• The respiration of decay microorganisms releases carbon dioxide into the atmosphere
• Increased decomposition in peat bogs releases huge volumes of carbon dioxide
• Peat bogs function as carbon sinks when they are stable
• Increased decomposition in permafrost releases carbon dioxide
• Permafrost is a huge carbon sink because it contains organic material that cannot decompose at low temperatures
• Decay organisms are inactive at low temperatures
• Increased atmospheric carbon dioxide further contributes to the greenhouse effect, increasing global warming
• Melting permafrost can also lead to the release of methane (CH4), a potent greenhouse gas