4.4 Climate Change

State the sources of CO2 and water vapor in the atmosphere

CO2: 1. Deforestation - the removal of trees means that less carbon dioxide is removed from the atmosphere via photosynthesis 2. combustion: When fossil fuels (e.g. coal, oil, gas) are combusted to release energy, carbon dioxide gas is released as a by-product - The increased reliance on fossil fuels following the industrial revolution has resulted in ~38% increase in CO2 levels - There are now efforts to reduce our reliance on fossil fuels by exploiting alternative energy sources (e.g. solar power) Water vapor: respiration

What are greenhouse gases?

The gases responsible for trapping the heat from the sun include carbon dioxide, water vapor, and to a lesser extent, methane and nitrogen oxides

Compare the impact of atmospheric methane to CO2

The impact of a gas depends on its ability to absorb long wave radiation as well as on its concentration in the atmosphere.

Explain how historical temperature data has been collected

1. A carbon footprint is defined as the total amount of greenhouse gases produced to directly and indirectly support human activity - It is usually expressed in equivalent tonnes of carbon dioxide (CO2) - A carbon footprint is therefore the sum of all CO2 emissions that were induced by a person's activity within a given timeframe: - All fossil fuel consumption (including petrol, electricity, natural gas) - All transportation (besides human-powered activities like walking and cycling) - All emissions associated with consumables (e.g. the production of a cheesburger can result in ~ 3 kg of CO2 emissions)

State two factors that determine the warming impact of a greenhouse gas

1. Ability to absorb long-wave radiation: Gases that have a greater capacity to absorb long-wave radiation will have a greater warming impact (per molecule) 2. Concentration within the atmosphere: The greater the concentration of a gas, the greater its warming impact. - The concentration of a gas will be determined by both its rate of release and persistence within the atmosphere

Explain why atmospheric CO2 concentration would logically impact global temperatures

1. As these gases trap heat, increases in greenhouse gas concentrations should correlate with an increase in global temperature 2. Long term weather patterns (climate) may also be influenced by greenhouse gas concentrations

Outline the effect of atmospheric CO2 concentration on ocean pH

1. Carbon dioxide will combine with water to form carbonic acid, which dissociates into hydrogen ions and hydrogen carbonate 2. H+ ions will lower the ocean pH (acidification) and will also combine with free carbonate ions to form more hydrogen carbonate 3. Rising levels of atmospheric carbon dioxide are causing a decrease in the pH of ocean water (ocean acidification)

Outline three reasons why there is vigorous debate around the claim that human activities are causing climate change.

1. Climate has changed in the past and current trends merely reflect the Earth's natural climatic cycle BUT Climate changes do occur naturally, but usually not as abruptly as what is seen currently 2.Climate change is being caused by solar activity and the effect of greenhouse gas emissions is negligible BUT Over the last 35 years the sun has shown a slight cooling trend, however average global temperatures have increased 3.Certain changes in climate conditions cannot be linked to greenhouse gas emissions BUT The rate at which sea levels have risen in the past 30 years is greater than that seen in the last 200 years

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

1. Incoming radiation from the sun is shorter wave radiation (ultraviolet radiation and the visible spectrum) 2. The surface of the Earth absorbs short wave radiation and re-emits it at a longer wavelength (i.e. infra-red / heat) 3. Greenhouse gases absorb and re-radiate this longer wave radiation and hence retain the heat within the atmosphere

Outline the effect of global temperature on climate, specifically location and frequency of of rain and frequency of severe storms

1. More frequent extreme weather conditions (e.g. heat waves, cyclones, more powerful tropical storms, etc.) 2. Some areas to become more drought affected, while other areas become more prone to periods of heavy rainfall 3. Changes to circulating ocean currents - which may cause longer El Nino (warming) and La Nina (cooling) events

Outline the mechanism by which greenhouse gases trap heat in the atmosphere

1. The greenhouse effect is the tendency of the atmosphere to retain heat that originally came from the Sun. 2. When sunlight comes to Earth, it is in shortwave radiation. As it comes into contact with the surface of the planet, it's transformed into another form of energy, heat. 3.Heat has a much longer wavelength than light energy, and it becomes trapped by the atmosphere. This warms the planet, and is a natural phenomenon.

Describe the impact of lower ocean pH on animals that make skeletons from calcium carbonate

1. Threats to coral reefs from increasing concentrations of dissolved carbon dioxide. - An increase in the concentration of H+ ions means there are less free carbonate ions available for calcification - Shells and coral exoskeletons are also likely to begin to dissolve when ocean conditions are more acidic - Corals, sea urchins and shelled molluscs do not exist in regions with high levels of dissolved CO2 (e.g. near hydrothermal vents)

Compare wavelengths of UV, visible and infrared radiation

1. UV: 10 nm to 380 nm 2. visible: 380 nm to 750 nm 3. infrared: 750 nm to 1 mm

Explain why water vapor, CO2, methane and NO are greenhouse gases

1. Water vapour is created via evaporation of water bodies (e.g. oceans) and transpiration - it is removed via precipitation (rain) 2. Carbon dioxide is made by cell respiration and burning fossil fuels - it is removed via photosynthesis and absorption by oceans 3. Methane is emitted from waterlogged habitats (like marshes) and landfills - it is also a gaseous waste produced by ruminants 4. Nitrogen oxides are released naturally by certain bacteria and also is emitted in the exhaust by certain vehicles They all absorb and emit long-wave (infrared) radiation, thereby trapping and holding heat within the atmosphere

The Earth absorbs _______-wave energy from the_____ and ____________ longer___________

1. short 2. sun 3. re-emits 4. longer 5. wavelengths

Outline ways by which claims can be evaluated for truth

1. supported by evidence - Many arguments are not backed by reliable scientific data or are made by entities with vested interests (e.g. oil companies) 2.

State how long water, methane and CO2 remain in the atmosphere, on average

1. water: 1 day 2. methane: 12 years 3. CO2: 20 years