Climate change
Outline three reasons why there is vigorous debate around the claim that human activities are causing climate change: Application: Evaluating claims that human activities are not causing climate change.
- Challenges from critics: Climate change as a result of human activity is just a theory, not a fact - Responses from scientists: Evidence clearly shows temperature increase since the industrial revolution. Decades-old predictions of extreme weather events, record temperatures and receding glaciers are being confirmed day after day. Climate change is not a debate nor a controversy: it is well-supported by an increasing volume of data. - Challenges from critics: There is a disagreement within the scientific community about human-induced climate change. Many scientists disagree and have published research showing that climate change is not due to human activity. - Responses from scientists: The vast majority of recent publications from climatologists confirm anthropogenic climate change; there is a consensus in the scientific community. Often the dissenting scientists who are quoted critics are not climatologists.
State two factors that determine the warming impact of greenhouse gas: Understanding: The impact of a gas depends on its ability to absorb long wave radiation as well as on its concentration in the atmosphere.
- The ability of the gas to absorb long-wave radiation (heat): gases that have a greater capacity to absorb long-wave radiation will have a greater warming impact. - The concentration of that gas in the atmosphere: the greater the concentration of a gas, the greater its warming impact will be in the atmosphere
Outline the impact of the industrial revolution on atmospheric CO2 concentration: Understanding: 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.
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.
Outline the mechanism by which greenhouse gases trap heat in the atmosphere: Understanding: Carbon dioxide and water vapor are the most significant greenhouse gases.
Greenhouse effect refers to a planet's ability to use its atmosphere to retain heat and keep warm when no sunlight is hitting the surface. Greenhouse gases, such as water vapour and carbon dioxide, 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, thereby trapping and holding heat within the atmosphere.
Explain why atmospheric CO2 concentration would logically impact global temperatures: Understanding: Global temperatures and climate patterns are influenced by concentrations of greenhouse gases.
Greenhouse gases play a pivotal role in determining global temperatures due to their capacity to retain heat. Given that these gases retain and emit heat, an increase in greenhouse gas concentration should positively correlated with an increase in global temperature. Thus, it is clear that an increase in carbon dioxide concentration will lead to warming of the atmosphere because it would increase the greenhouse effect.
State the sources of methane and nitrogen oxide in the atmosphere: Understanding: Other gases including methane and nitrogen oxides have less impact.
In addition to carbon dioxide and water vapour, methane and nitrogen oxides also contributes to Earth's greenhouse effect, but to a lesser extent. Methane is emitted from waterlogged habitats and landfills whereas nitrogen oxides are released naturally by certain bacteria and also is emitted by certain vehicles.
State that the Earth absorbs short-wave energy from the sun and re-emits longer wavelengths: Understanding: The warmed Earth emits longer wavelength radiation (heat).
Incoming radiation from the sun is shorter wave radiation. The surface of the earth absorbs shortwave radiation and re-emits it at a longer wavelength. Greenhouse gases absorb and re-radiate this longer wave radiation and hence retain the heat within the atmosphere.
Outline the effect of atmospheric CO2 concentration on ocean pH: Application: Threats to coral reefs from increasing concentrations of dissolved carbon dioxide.
Increased carbon dioxide concentrations in the air lead to increased dissolved carbon dioxide in the oceans which lower the pH of seawater.
Compare the impact of atmospheric methane to CO2: Understanding: The impact of a gas depends on its ability to absorb long wave radiation as well as on its concentration in the atmosphere.
Methane has a much greater potential to warm the planet than carbon dioxide given that it has a larger capacity to absorb long-wave radiation than carbon dioxide. However, it is significantly less abundant.
Describe the correlation between atmospheric CO2 concentrations since the industrial revolution and global temperatures: Understanding: 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.
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.
State two variables that determine the concentration of a gas in the atmosphere: Understanding: The impact of a gas depends on its ability to absorb long wave radiation as well as on its concentration in the atmosphere.
The concentration of a gas will be determined by both its rate of release and persistence within the atmosphere.
Explain the greenhouse effect, with reference to short wave radiation from the sun, long wave radiation from the Earth and the effects of ozone and greenhouse gases: Understanding: Longer wave radiation is absorbed by greenhouse gases that retain the heat in the atmosphere.
The greenhouse effect is a natural process whereby the atmosphere behaves like a greenhouse to trap and retain heat. The incoming shortwave radiation from the sun are re-emitted into longwave radiation absorbed and retained by greenhouse gases. Then, the greenhouse gases can then radiate the heat in all directions. Some of this heat will be lost to space, but some of the longwave radiation will be redirected down to the surface. The rest will radiate within the atmosphere, preventing it from getting extremely cold at night.
Explain why industrial revolution would increase atmospheric CO2 concentrations: Understanding: Recent increases in atmospheric carbon dioxide are largely due to increases in the combustion of fossilized organic matter.
The number one source of carbon emissions as a result of human activity is transport that is based on fossil fuels: cars, airplanes. Other human activities that put carbon dioxide into the air include: deforestation, heating homes by burning fossil fuels, maintaining a diet high in meat, purchasing foreign goods. Human activities contribute to the production of other greenhouse gases. A heavy meat-based diet increases the production of methane. Lastly, oxides of nitrogen are produced by human activities such as: burning fossil fuels, using organic and commercial fertilizers to help crops grow better and industrial processes.
State the sources of CO2 and water vapor in the atmosphere: Understanding: Carbon dioxide and water vapor are the most significant greenhouse gases.
Water vapor is created via evaporation of water bodies and transpiration. Carbon dioxide is produced by cell respiration and burning of fossil fuels.
State how long water, methane and CO2 remain in the atmosphere, on average: Understanding: The impact of a gas depends on its ability to absorb long wave radiation as well as on its concentration in the atmosphere.
Water vapour has a very short atmospheric lifetime: 1 to 5 days. Methane has a relatively short lifetime in the atmosphere, about 12 years. Carbon dioxide has an estimated lifetime of 5-200 years
Describe the impact of lower ocean pH on animals that make skeletons from calcium carbonate: Application: Threats to coral reefs from increasing concentrations of dissolved carbon dioxide.
When it is intense, ocean acidification leads to the deaths of coral and algae, and when they die the reefs are not built up anymore. As a result, the colour of the reed goes from being richly multi-coloured to being as white as a bone. The coral reef death is called bleaching and it interrupts the food chain, causing many of the organisms that live there to seek food and shelter elsewhere.