4.4 Climate change Flashcards
What are the 2 most significant (largest effect on the Earth) greenhouse gases?
Carbon dioxide and water vapour
What are the 2 most significant greenhouse gases?
Carbon dioxide and water vapour
What does gases do in the atmosphere?
They retain heat
How is carbon dioxide released in the atmosphere and how is it removed from the atmosphere?
- Released by cell respiration in living organisms and also by combustion of biomass and fossil fuels
- Removed by photosynthesis and by dissolving in the oceans
How is water vapour formed and how is it removed?
- Formed by evaporation from the oceans and also transpiration in plants
- Removed from the atmosphere by rainfall and snow
In what form does water continue to retain heat after it condenses?
After it condenses to form droplets of liquid water in clouds
Why does temperature drop so much more quickly at night in areas with clear skies than in areas with cloud cover?
- Water continues to retain heat after it condenses to form droplets of liquid water in clouds
- The water absorbs heat energy and radiates it back to the Earth’s surface and also reflects the heat energy back
What are the 2 greenhouse gases that have less impact than CO2 and water vapour?
Methane and nitrogen oxides
What are the two most significant greenhouse gases?
CO2 and water vapour
How is methane and nitrogen oxides compared to CO2 and water vapour?
CO2 and water vapour - most abundant
Methane and nitrogen oxides - have smaller but nontheless significant effect
What is methane emitted from?
- the 3rd most significant greenhouse gas
- emitted from marshes and other waterlogged habitats and from landfill sites where organic wastes have been dumped
- release during extraction of fossil fuels and from melting ice in polar regions
Where is nitrous oxide released from?
- released naturally by bacteria in some habitats and also by agriculture and vehicle exhausts
Why is oxygen and nitrogen, the two most abundant gases in the Earth’s atmosphere not greenhouse gases?
They do not absorb longer-wave radiation
How much does all the greenhouse gases together make up in the atmosphere?
Less than 1%
What does the impact of a gas depend on?
Its ability to absorb long-wave radiation as well as on its concentration in the atmosphere
Why is methane’s impact on global warming less than CO2?
Because it has a lower concentration than CO2
What does the concentration of a gas depend on?
- Rate at which it is released into the atmosphere
- How long on average it remains in the atmosphere
How quickly does water vapour enter the atmosphere and how long on average does it remain there?
It enters the atmosphere immensely rapid, but it remains there only 9 days on average, whereas methan remains in the atmosphere for 12 years and carbon dioxide even longer
What length wave does the Earth absorb?
The warmed surface of the Earth absorbs short-wave energy from the sun
What does the Earth do after absorbing short-wave energy from the sun?
It re-emits it at much longer wave-lengths
What does the Earth do after absorbing short-wave energy from the sun?
It re-emits it at much longer wave-lengths
What is the longer-wave radiation reabsorbed by?
Greenhouse gases
What is the longer-wave radiation reabsorbed by?
Greenhouse gases
What is the effect of longer-wave radiation being reabsorbed by greenhouse gases?
It retains the heat in the atmosphere
How does the greenhouse effect work?
- Approx 25% of solar radiation is absorbed by the atmosphere
- Approx 75% of solar radiation penetrates the atmosphere and eaches the Earth’s surface
- The surface of the Earth absorbs short-wave solar energy and re0emits at longer wavelengths (as heat)
- Up to 85% of re-emitted heat is captured by greenhouse gases in the atmosphere
- Heat passes back to the surface of the Earth, causing warming
What do water vapour, carbon dioxide, methane and nitrous oxide have in common?
- They all abosrb some of these wavelengths so each of them is a greenhouse gas
What can we expect if the concentration of any of the greenhouse gases in the atmosphere chnages?
- Size of its contribution to the greenhouse effect to change
- Global temperatures to rise or fall
How can we deduce carbon dioxide concentrations from the past?
- Using columns of ice
- Ice has built up over thousands of years, so ice from deper down is older than the ice near the surface
- Bubbles of air trapped in the ice can be extracted and analysed to find the CO2 concetntration
How do we deduce the global temperatures from the past?
- Using columns of ice
- Ice has built up over thousands of years, so ice from deper down is older than the ice near the surface
- Global temperatures can be deduced from ratios of hydrogen isotopes in the water molecules
What are global temperatures and lcimate patterns influenced by?
Concentration of greenhouse gases
What other factors have an influence on global average temperatures thats not greenhouse gases?
- Milankovitch cycles in the Earth’s orbit
- Variation in sunspot activity
What is the influence of higher air temperature on climate?
- Higher temperaturesi ncrease the evaporation of water from the oceans
- Periods of rain are likely to be more frequent and protracted
- The amount of rain delivered during thunderstorms and other intense burst is likely to increase very significantly
What is the influence of higher ocean temperature on climate?
- Higher ocean temperatures cause topical storms and hurricanes to be more frequent and more powerful, with faster wind speeds
Since when did atmpospheric concentrations of carbon dioxide begin to increase along with average global temperatures?
Since the start of the industrial revolution
What caused consequent increases in atmospheric carbon dioxide concentration in the second half of the 20th century?
When more countries became industrialized and combustion of coal, oil and natural gas increased ever more rapidly
What are recent incrases in atmospheric carbon dioxide largely due to?
Combustion of fossilized organic matter
What caused carbon dioxide emissions in the industrial revolution?
Mining and burning increasing quantities of coal
In addition to combustion of coal, what became increasingly widespsread?
Combustion of oil and natural gas
Why would some companies pay for reports to be written that minimizes the risks of climate change?
Because companies make huge profits from coal, oil and natural gas and it is in their interests for fossil fuel combustion to continue to grow
What happens to the ocean when carbon dioxide concentrations of the atmosphere continues to rise?
Ocean acidification
What do marine animals that deopsit calcium carbonate in their skeletons need?
Need to absorb carbonate ions from seawater
What do marine animals that deopsit calcium carbonate in their skeletons need?
Need to absorb carbonate ions from seawater
Why is the concentration of carbonate ions in seawater low?
Because they are not very soluble
What do dissolved carbon dioxide do to carbonate concentration in the ocean?
It makes the carbonate concentration even lower as a result of some interrelated chemical reactions
How does dissolved carbon dioxide make carbonate concentrations even lower?
- CO2 reacts with water to form carbonic acid
- Which dissociates into hydrogen and hydrogen carbonate ions
- Hydrogen ions react with dissolved carbonate ions, reducing their concentration
What happens when carbonate ion concentrations drop?
More difficult for reef-building corals to absorb them to make their skeletons
What happens if seawater ceases to be a saturated solution of carbonate ions?
Exisiting calcium carbonate tends to dissolve, so exisitng skeletons of reef-building corals are threatened
What would you expect in an area of acidified water?
No corals, no sea urchines or other animals thst make their skeletons from calcium carbonate
In their place other organisms flourish such as sea grasses and invsasive algae
