Understandings:
● Carbon dioxide and water vapor are the most significant greenhouse gases.
● Other gases including methane and nitrogen oxides have less impact.
● The impact of a gas depends on its ability to absorb long-wave radiation as well as on its concentration in the atmosphere.
● The warmed Earth emits longer wavelength radiation (heat).
● Longer wave radiation is absorbed by greenhouse gases, which retain the heat in the atmosphere.
● Global temperatures and climate patterns are influenced by concentrations of greenhouse gases.
● There is a correlation between rising atmospheric concentrations of carbon dioxide since the start of the industrial revolution 200 years ago and average global temperatures.
● Recent increases in atmospheric carbon dioxide are largely due to increases in the combustion of fossilized organic matter.
Applications and skills:
● Application: Threats to coral reefs from increasing concentrations of dissolved carbon dioxide.
● Application: Correlations between global temperatures and carbon dioxide concentrations on Earth.
● Application: Evaluating claims that human activities are not causing climate change.
Guidance
● Carbon dioxide, methane, and water vapour should be included in discussions.
● The harmful consequences of ozone depletion do no need to be discussed and it should be made clear that ozone depletion is not the cause of the enhanced greenhouse effect.
International-mindedness:
Release of greenhouse gases occurs locally but has a global impact, so international cooperation to reduce emissions is essential.
The roles of carbon dioxide and water vapour in the greenhouse effect
The greenhouse effect refers to a planet’s ability to use its atmosphere to retain heat and keep warm even when no sunlight is hitting the surface. The walls and roof of a greenhouse are made of glass. Sunlight penetrates through the glass and warms up the plants inside. Sunlight itself, which is made up of short wavelengths, is not warm; the temperature of outer space between the Sun and Earth is hundreds of degrees below freezing. It is only when sunlight hits an object that some of its energy is transformed into heat. Heat energy, otherwise known as infrared radiation, has longer wavelengths than energy in the form of light. When sunlight goes through the glass of the greenhouse, it warms up the objects inside: the plants, the ground, and anything else inside. The objects inside radiate their heat to the air inside the greenhouse, but the glass of the greenhouse is not as transparent to heat energy as it is to light energy, so some of the heat is then trapped inside the greenhouse. The glass also plays a major role in preventing warm air from rising through convection to dissipate the heat. The result is that the temperature inside the greenhouse is warmer than outside. This helps plants to grow better when it is cold outside, which is one of the main reasons why farmers and gardeners use greenhouses.
The greenhouse effect on a planet is not caused by glass windows, but by its atmosphere’s ability to retain heat in a similar way to that of the glass of a greenhouse or car.
Greenhouse gases (GHGs), such as water vapour and carbon dioxide in Earth’s atmosphere, can be thought of as the glass of a greenhouse, although, like many models, this is not a very accurate representation of the natural phenomenon. GHGs have the ability to absorb and radiate infrared radiation (heat). When such gases are present, they keep the atmosphere near Earth’s surface warm by absorbing heat from the warmed surface and re-radiating it in all directions, including back down towards the surface. In addition to carbon dioxide and water vapour, methane and nitrogen oxides also contribute to Earth’s greenhouse effect, but to a lesser extent.
Different gases, different impacts
There are two main factors that determine how much of an influence a gas will have on the greenhouse effect:
• the ability of the gas to absorb long-wave radiation (heat)
• the concentration of that gas in the atmosphere.
Methane actually has a much greater potential to warm the planet than carbon dioxide, but methane has a relatively short lifetime in the atmosphere: approximately 12 years. Carbon dioxide has an estimated lifetime of 50–200 years in the atmosphere. This is because methane can be broken down into other molecules, whereas carbon dioxide is not very reactive and so can stay in the atmosphere for much longer.
Studies of increases in carbon dioxide and methane gases over time have revealed that carbon dioxide concentrations have increased by approximately 40% since 1750, while methane concentrations have increased by more than 150% in the same time period. However, methane concentrations in Earth’s atmosphere are about 1700 p.p.b. (parts per billion) whereas carbon dioxide concentrations are about 400 p.p.m. (parts per million), meaning that the concentration of carbon dioxide is more than 200 times greater than that of methane.
The warmed Earth emits longer wavelength radiation (heat)
When sunlight touches an object inside, some of the light energy is absorbed and converted into heat energy, also known as long-wave infrared radiation. On Earth, the mountains, forests, rivers, and oceans absorb some of the sunlight and are warmed. Most of the sunlight bounces off the surface and goes back into space.
The ability of a surface to reflect light is called its albedo. Light-coloured objects, such as ice and white sand, have a high albedo, so very little light is absorbed and such objects do not heat up as much as dark objects such as dark-coloured rocks and black sand. Dark-coloured substances such as the asphalt have a low albedo, and absorb lots of light and convert it into heat.
● Carbon dioxide and water vapor are the most significant greenhouse gases.
● Other gases including methane and nitrogen oxides have less impact.
● The impact of a gas depends on its ability to absorb long-wave radiation as well as on its concentration in the atmosphere.
● The warmed Earth emits longer wavelength radiation (heat).
● Longer wave radiation is absorbed by greenhouse gases, which retain the heat in the atmosphere.
● Global temperatures and climate patterns are influenced by concentrations of greenhouse gases.
● There is a correlation between rising atmospheric concentrations of carbon dioxide since the start of the industrial revolution 200 years ago and average global temperatures.
● Recent increases in atmospheric carbon dioxide are largely due to increases in the combustion of fossilized organic matter.
Applications and skills:
● Application: Threats to coral reefs from increasing concentrations of dissolved carbon dioxide.
● Application: Correlations between global temperatures and carbon dioxide concentrations on Earth.
● Application: Evaluating claims that human activities are not causing climate change.
Guidance
● Carbon dioxide, methane, and water vapour should be included in discussions.
● The harmful consequences of ozone depletion do no need to be discussed and it should be made clear that ozone depletion is not the cause of the enhanced greenhouse effect.
International-mindedness:
Release of greenhouse gases occurs locally but has a global impact, so international cooperation to reduce emissions is essential.
The roles of carbon dioxide and water vapour in the greenhouse effect
The greenhouse effect refers to a planet’s ability to use its atmosphere to retain heat and keep warm even when no sunlight is hitting the surface. The walls and roof of a greenhouse are made of glass. Sunlight penetrates through the glass and warms up the plants inside. Sunlight itself, which is made up of short wavelengths, is not warm; the temperature of outer space between the Sun and Earth is hundreds of degrees below freezing. It is only when sunlight hits an object that some of its energy is transformed into heat. Heat energy, otherwise known as infrared radiation, has longer wavelengths than energy in the form of light. When sunlight goes through the glass of the greenhouse, it warms up the objects inside: the plants, the ground, and anything else inside. The objects inside radiate their heat to the air inside the greenhouse, but the glass of the greenhouse is not as transparent to heat energy as it is to light energy, so some of the heat is then trapped inside the greenhouse. The glass also plays a major role in preventing warm air from rising through convection to dissipate the heat. The result is that the temperature inside the greenhouse is warmer than outside. This helps plants to grow better when it is cold outside, which is one of the main reasons why farmers and gardeners use greenhouses.
The greenhouse effect on a planet is not caused by glass windows, but by its atmosphere’s ability to retain heat in a similar way to that of the glass of a greenhouse or car.
Greenhouse gases (GHGs), such as water vapour and carbon dioxide in Earth’s atmosphere, can be thought of as the glass of a greenhouse, although, like many models, this is not a very accurate representation of the natural phenomenon. GHGs have the ability to absorb and radiate infrared radiation (heat). When such gases are present, they keep the atmosphere near Earth’s surface warm by absorbing heat from the warmed surface and re-radiating it in all directions, including back down towards the surface. In addition to carbon dioxide and water vapour, methane and nitrogen oxides also contribute to Earth’s greenhouse effect, but to a lesser extent.
Different gases, different impacts
There are two main factors that determine how much of an influence a gas will have on the greenhouse effect:
• the ability of the gas to absorb long-wave radiation (heat)
• the concentration of that gas in the atmosphere.
Methane actually has a much greater potential to warm the planet than carbon dioxide, but methane has a relatively short lifetime in the atmosphere: approximately 12 years. Carbon dioxide has an estimated lifetime of 50–200 years in the atmosphere. This is because methane can be broken down into other molecules, whereas carbon dioxide is not very reactive and so can stay in the atmosphere for much longer.
Studies of increases in carbon dioxide and methane gases over time have revealed that carbon dioxide concentrations have increased by approximately 40% since 1750, while methane concentrations have increased by more than 150% in the same time period. However, methane concentrations in Earth’s atmosphere are about 1700 p.p.b. (parts per billion) whereas carbon dioxide concentrations are about 400 p.p.m. (parts per million), meaning that the concentration of carbon dioxide is more than 200 times greater than that of methane.
The warmed Earth emits longer wavelength radiation (heat)
When sunlight touches an object inside, some of the light energy is absorbed and converted into heat energy, also known as long-wave infrared radiation. On Earth, the mountains, forests, rivers, and oceans absorb some of the sunlight and are warmed. Most of the sunlight bounces off the surface and goes back into space.
The ability of a surface to reflect light is called its albedo. Light-coloured objects, such as ice and white sand, have a high albedo, so very little light is absorbed and such objects do not heat up as much as dark objects such as dark-coloured rocks and black sand. Dark-coloured substances such as the asphalt have a low albedo, and absorb lots of light and convert it into heat.
How greenhouse gases heat the atmosphere
he greenhouse gases absorb and retain the infrared radiation coming from the surface. The greenhouse gases can then re-radiate the heat in all directions, the way a radiator does in a cold room. Some of this heat will be lost to space, but some of the long-wave radiation will be directed down to the surface, keeping it warm. The rest will radiate within the atmosphere, preventing it from getting extremely cold at night when no more sunlight is present. When the Sun rises again in the morning, the surface will heat up and the whole process starts again.
During the winter season, the days are shorter and the angle of sunlight is less direct, so Earth’s surface cannot warm up as much. This is why it is colder in the winter. In the summer, days are longer and the sunlight hits Earth’s surface more directly and intensely. Earth’s surface can get very hot, and, during heat waves, the nights are not cool enough to cause the daytime temperatures to lower.
Global climate change is affected by greenhouse gases
Climate refers to the patterns of temperature and precipitation, such as rainfall, that occur over long periods of time. Whereas weather can change from hour to hour, climates usually do not change within a human’s lifetime: climate changes generally occur over thousands or millions of years.
he greenhouse gases absorb and retain the infrared radiation coming from the surface. The greenhouse gases can then re-radiate the heat in all directions, the way a radiator does in a cold room. Some of this heat will be lost to space, but some of the long-wave radiation will be directed down to the surface, keeping it warm. The rest will radiate within the atmosphere, preventing it from getting extremely cold at night when no more sunlight is present. When the Sun rises again in the morning, the surface will heat up and the whole process starts again.
During the winter season, the days are shorter and the angle of sunlight is less direct, so Earth’s surface cannot warm up as much. This is why it is colder in the winter. In the summer, days are longer and the sunlight hits Earth’s surface more directly and intensely. Earth’s surface can get very hot, and, during heat waves, the nights are not cool enough to cause the daytime temperatures to lower.
Global climate change is affected by greenhouse gases
Climate refers to the patterns of temperature and precipitation, such as rainfall, that occur over long periods of time. Whereas weather can change from hour to hour, climates usually do not change within a human’s lifetime: climate changes generally occur over thousands or millions of years.
here appears to be a strong correlation between temperature increase and carbon dioxide increase. Knowing the properties of greenhouse gases, it is clear that an increase in carbon dioxide levels will lead to warming of the atmosphere, because it would increase the greenhouse effect. Having said this, closer inspection of the data shows that the increase in temperature (in blue) happens first and then the carbon dioxide concentration (in red) rises. This lag time is partly explained by the fact that, as oceans warm up, they release carbon dioxide, because gases dissolve less well in warm water than in cold water. A positive feedback loop leads to further increases in temperatures over time: warmer temperatures → more carbon dioxide → even warmer temperatures → even more carbon dioxide, and so on.
The industrial revolution
Ever since machines started replacing hand tools in Europe in the 1800s, humans have produced increasing quantities of carbon dioxide from factories, transport, and other processes using fossil fuels, notably coal and oil. In addition, burning forests to make way for farmland and burning wood for cooking and heating has contributed to this increase.
Over the decades, human activities have produced enough carbon dioxide to considerably raise the percentage of this gas in the planet’s atmosphere. Estimates suggest that the level of carbon dioxide in the atmosphere has increased by more than 35% compared with its pre-industrial revolution levels.
- Recent increases in atmospheric carbon dioxide are largely due to increases in the combustion of fossilized organic matter
The gases produced by human activity that retain the most heat are among the ones we have already identified as greenhouse gases: carbon dioxide, methane, and oxides of nitrogen. The concentrations of these gases in the atmosphere are naturally low, which normally prevents too much heat retention.
The number one source of carbon emissions as a result of human activity is transport that is based on fossil fuels: cars, lorries, diesel trains and airplanes. Other human activities that put carbon dioxide into the air include the following: deforestation, heating homes by burning fossil fuels, maintaining a diet high in meat (the meat industry is highly dependent on fossil fuels), purchasing goods that have to be transported long distances from where they are produced to where they will be used, travelling long distances between work and home, purchasing foods that are grown out of season in greenhouses heated by fossil fuels.
Human activities contribute to the production of other greenhouse gases. Again, diet has an impact here, this time with the production of methane since it is produced by anaerobic microorganisms present in the guts of animals. Mass consumption of meat, has led to an increase in the number of cattle being raised. Cattle are responsible for producing large amounts of methane that escape into the atmosphere.
Oxides of nitrogen (NOx) are produced by human activities such as:
• burning fossil fuels (e.g. gasoline in cars) and using catalytic converters in exhaust systems
• using organic and commercial fertilizers to help crops grow better
• industrial processes (e.g. the production of nitric acid).
The industrial revolution
Ever since machines started replacing hand tools in Europe in the 1800s, humans have produced increasing quantities of carbon dioxide from factories, transport, and other processes using fossil fuels, notably coal and oil. In addition, burning forests to make way for farmland and burning wood for cooking and heating has contributed to this increase.
Over the decades, human activities have produced enough carbon dioxide to considerably raise the percentage of this gas in the planet’s atmosphere. Estimates suggest that the level of carbon dioxide in the atmosphere has increased by more than 35% compared with its pre-industrial revolution levels.
- Recent increases in atmospheric carbon dioxide are largely due to increases in the combustion of fossilized organic matter
The gases produced by human activity that retain the most heat are among the ones we have already identified as greenhouse gases: carbon dioxide, methane, and oxides of nitrogen. The concentrations of these gases in the atmosphere are naturally low, which normally prevents too much heat retention.
The number one source of carbon emissions as a result of human activity is transport that is based on fossil fuels: cars, lorries, diesel trains and airplanes. Other human activities that put carbon dioxide into the air include the following: deforestation, heating homes by burning fossil fuels, maintaining a diet high in meat (the meat industry is highly dependent on fossil fuels), purchasing goods that have to be transported long distances from where they are produced to where they will be used, travelling long distances between work and home, purchasing foods that are grown out of season in greenhouses heated by fossil fuels.
Human activities contribute to the production of other greenhouse gases. Again, diet has an impact here, this time with the production of methane since it is produced by anaerobic microorganisms present in the guts of animals. Mass consumption of meat, has led to an increase in the number of cattle being raised. Cattle are responsible for producing large amounts of methane that escape into the atmosphere.
Oxides of nitrogen (NOx) are produced by human activities such as:
• burning fossil fuels (e.g. gasoline in cars) and using catalytic converters in exhaust systems
• using organic and commercial fertilizers to help crops grow better
• industrial processes (e.g. the production of nitric acid).
Theory of Knowledge
The precautionary principle is meant to guide decision-making in conditions where a lack of certainty exists. Is certainty ever possible in the natural sciences?
One steady subject is that there is no assurance in science, just degrees of likelihood (probability), and potential for change. Scientific comprehension can simply be tested, and even changed, with better approaches for watching, and with distinctive understandings. The same is valid for scientific facts. New instruments and procedures have brought about new perceptions, sometimes compelling modification of what had been taken as certainty previously. Consequently,in science nothing is ever demonstrated (in the feeling of certainty or assurance).
Since we can't demonstrate anything with 100% sureness in the natural world, the reason for science should not be to demonstrate that things are genuine, rather that things are false. In the event that a speculation confronts testing more than a drawn out stretch of time, it is given the term hypothesis or theory. This implies that we are less inspired by hypotheses that are valid as we are speculations that are not false.
The precautionary principle is meant to guide decision-making in conditions where a lack of certainty exists. Is certainty ever possible in the natural sciences?
One steady subject is that there is no assurance in science, just degrees of likelihood (probability), and potential for change. Scientific comprehension can simply be tested, and even changed, with better approaches for watching, and with distinctive understandings. The same is valid for scientific facts. New instruments and procedures have brought about new perceptions, sometimes compelling modification of what had been taken as certainty previously. Consequently,in science nothing is ever demonstrated (in the feeling of certainty or assurance).
Since we can't demonstrate anything with 100% sureness in the natural world, the reason for science should not be to demonstrate that things are genuine, rather that things are false. In the event that a speculation confronts testing more than a drawn out stretch of time, it is given the term hypothesis or theory. This implies that we are less inspired by hypotheses that are valid as we are speculations that are not false.