Earth DAy 2016:Greenhouse Effect
Greenhouse Effect
- The sun emits shortwave radiation, which passes through Earth's atmosphere and is absorbed by Earth's surface.
- Some energy is re-emitted back into the atmosphere, as long wave radiation.
- 'Greenhouse' gases: carbon dioxide, nitrous oxide, methane, water vapour effectively prevent some of this longwave radiation from leaving the atmosphere.
- This warms Earth's atmosphere, making our planet habitable.
- Human activities have led to a build up of extra greenhouse gases in the atmsophere.
- As a result, average surface temperatures are rising.
- Temperatures will continue to rise if greenhouse gases keep building up in the atmosphere.
Without the greenhouse effect we would be living in a very chilly place
—the world's average temperature would be minus 18°C, instead of the 15°C we are used to. So what is the greenhouse effect, and how does it make Earth around 33°C warmer?The natural greenhouse effect:
The natural greenhouse effect is a phenomenon caused by gases naturally present in the atmosphere that affect the behaviour of the heat energy radiated by the sun. In simple terms, sunlight (shortwave radiation) passes through the atmosphere, and is absorbed by Earth’s surface. This warms Earth’s surface, and then Earth radiates some of this energy (as infrared, or longwave radiation) back towards space. As it passes through the atmosphere, gases such as (water vapour, carbon dioxide, methane and nitrous oxide absorb most of the energy. The energy is then re-emitted in all directions, so some energy escapes into space, but less than would have escaped if the atmosphere and its greenhouse gases weren’t there. The result is that some of the sun's energy becomes ‘trapped’—making the lower part of the atmosphere, and Earth, warmer than it would be otherwise.
This process is known as the greenhouse effect because it is similar to how a greenhouse works the sun’s energy passes through the glass (or similar) panes of the greenhouse, but not all of it is allowed to escape again, making the inside of the greenhouse a warmer and more hospitable environment for the plants inside.
Earth’s energy balance:The rate at which energy is absorbed by Earth is approximately balanced by the rate at which it is emitted back into space, keeping the Earth in what’s known as a state of equilibrium, and at a stable temperature. As long as the amount of greenhouse gases in the air stays the same, and the rate of energy arriving from the sun is constant, this equilibrium is maintained. In the state of equilibrium that existed during the centuries up until Industrial Revolution, which started in the late 1700s, the natural greenhouse effect maintained the average temperature of Earth’s surface at around 15°C.Greenhouse Gases:Scientists have been regularly measuring the atmosphere’s carbon dioxide (CO2) content since around 1960. Several stations around the world, including a number of Australian stations jointly operated by the Bureau of Meteorology and CSIRO, monitor CO2and other greenhouse gases and contribute data to the Global Atmosphere Watch.But how can we find out the CO2 concentrations that existed before this regular monitoring started?Evidence comes from a variety of sources, but one of the most straightforward involves taking ice samples from the polar ice caps. Ice sheets build up from the compression of each year's snowfalls. By drilling down into the ice (which is up to 4 kilometres thick), scientists can collect core samples of the annual snowfall going back over thousands of years. The deeper you go, the older the ice. This ice contains air bubbles, captured when the snow fell and sealed in ice since that time.The composition of the atmosphere is changing:
Earth's atmosphere is made up of 78 per cent nitrogen and 21 per cent oxygen. Only about 1 per cent is made up of natural greenhouse gases, but this comparatively small amount of gas makes a big difference. The Industrial Revolution brought new industrial processes, an increase in the burning of fossil fuels, more extensive agriculture, and a rapid increase in the world's population. This rapid increase in human activity led to the (still ongoing) emission of significant amounts of greenhouse gases into the atmosphere. We know this because of measurements made over the past 50 years and the analysis of air bubbles trapped in ancient ice, which show that levels of carbon dioxide, methane, nitrous oxide and halocarbons are increasing.
Although Earth’s atmosphere has changed significantly over geological time, and high concentrations of greenhouse gases have been present in Earth’s atmosphere in the past, never before has Earth been subjected to such a large increase in the amount of greenhouse gases in the atmosphere over such a short time. Although over a geological timeframe (thousands to millions of years), life on Earth would be able to gradually adapt to the increased concentrations of greenhouse gases, the comparative equilibrium that has existed for the past 10,000 years or so is being disturbed at such a rapid rate that adaptation might not be possible.
- The sun emits shortwave radiation, which passes through Earth's atmosphere and is absorbed by Earth's surface.
- Some energy is re-emitted back into the atmosphere, as long wave radiation.
- 'Greenhouse' gases: carbon dioxide, nitrous oxide, methane, water vapour effectively prevent some of this longwave radiation from leaving the atmosphere.
- This warms Earth's atmosphere, making our planet habitable.
- Human activities have led to a build up of extra greenhouse gases in the atmsophere.
- As a result, average surface temperatures are rising.
- Temperatures will continue to rise if greenhouse gases keep building up in the atmosphere.
The natural greenhouse effect is a phenomenon caused by gases naturally present in the atmosphere that affect the behaviour of the heat energy radiated by the sun. In simple terms, sunlight (shortwave radiation) passes through the atmosphere, and is absorbed by Earth’s surface. This warms Earth’s surface, and then Earth radiates some of this energy (as infrared, or longwave radiation) back towards space. As it passes through the atmosphere, gases such as (water vapour, carbon dioxide, methane and nitrous oxide absorb most of the energy. The energy is then re-emitted in all directions, so some energy escapes into space, but less than would have escaped if the atmosphere and its greenhouse gases weren’t there. The result is that some of the sun's energy becomes ‘trapped’—making the lower part of the atmosphere, and Earth, warmer than it would be otherwise.
This process is known as the greenhouse effect because it is similar to how a greenhouse works the sun’s energy passes through the glass (or similar) panes of the greenhouse, but not all of it is allowed to escape again, making the inside of the greenhouse a warmer and more hospitable environment for the plants inside.
Earth’s energy balance:The rate at which energy is absorbed by Earth is approximately balanced by the rate at which it is emitted back into space, keeping the Earth in what’s known as a state of equilibrium, and at a stable temperature. As long as the amount of greenhouse gases in the air stays the same, and the rate of energy arriving from the sun is constant, this equilibrium is maintained. In the state of equilibrium that existed during the centuries up until Industrial Revolution, which started in the late 1700s, the natural greenhouse effect maintained the average temperature of Earth’s surface at around 15°C.Greenhouse Gases:Scientists have been regularly measuring the atmosphere’s carbon dioxide (CO2) content since around 1960. Several stations around the world, including a number of Australian stations jointly operated by the Bureau of Meteorology and CSIRO, monitor CO2and other greenhouse gases and contribute data to the Global Atmosphere Watch.But how can we find out the CO2 concentrations that existed before this regular monitoring started?Evidence comes from a variety of sources, but one of the most straightforward involves taking ice samples from the polar ice caps. Ice sheets build up from the compression of each year's snowfalls. By drilling down into the ice (which is up to 4 kilometres thick), scientists can collect core samples of the annual snowfall going back over thousands of years. The deeper you go, the older the ice. This ice contains air bubbles, captured when the snow fell and sealed in ice since that time.The composition of the atmosphere is changing:
Earth’s energy balance:The rate at which energy is absorbed by Earth is approximately balanced by the rate at which it is emitted back into space, keeping the Earth in what’s known as a state of equilibrium, and at a stable temperature. As long as the amount of greenhouse gases in the air stays the same, and the rate of energy arriving from the sun is constant, this equilibrium is maintained. In the state of equilibrium that existed during the centuries up until Industrial Revolution, which started in the late 1700s, the natural greenhouse effect maintained the average temperature of Earth’s surface at around 15°C.Greenhouse Gases:Scientists have been regularly measuring the atmosphere’s carbon dioxide (CO2) content since around 1960. Several stations around the world, including a number of Australian stations jointly operated by the Bureau of Meteorology and CSIRO, monitor CO2and other greenhouse gases and contribute data to the Global Atmosphere Watch.But how can we find out the CO2 concentrations that existed before this regular monitoring started?Evidence comes from a variety of sources, but one of the most straightforward involves taking ice samples from the polar ice caps. Ice sheets build up from the compression of each year's snowfalls. By drilling down into the ice (which is up to 4 kilometres thick), scientists can collect core samples of the annual snowfall going back over thousands of years. The deeper you go, the older the ice. This ice contains air bubbles, captured when the snow fell and sealed in ice since that time.The composition of the atmosphere is changing:
Earth's atmosphere is made up of 78 per cent nitrogen and 21 per cent oxygen. Only about 1 per cent is made up of natural greenhouse gases, but this comparatively small amount of gas makes a big difference. The Industrial Revolution brought new industrial processes, an increase in the burning of fossil fuels, more extensive agriculture, and a rapid increase in the world's population. This rapid increase in human activity led to the (still ongoing) emission of significant amounts of greenhouse gases into the atmosphere. We know this because of measurements made over the past 50 years and the analysis of air bubbles trapped in ancient ice, which show that levels of carbon dioxide, methane, nitrous oxide and halocarbons are increasing.
Reference:
- Most of the matter is collected from Google and www.nova.org.au
- videos is taken from https://youtu.be/ffjIyms1BX4
Reference:
- Most of the matter is collected from Google and www.nova.org.au
- videos is taken from https://youtu.be/ffjIyms1BX4
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