4.4 climate change

Question 1

how do greenhouse gases trap heat?

Answer 1

greenhouse gases absorbs and emit long-wave (infrared) radiation, thereby trapping and holding heat within the atmosphere.

Question 2

greenhouse gases make up ________of atmosphere

Answer 2

less than 1% collectively

Question 3

greenhouse gases which have the largest warming effect within the atmosphere are

Answer 3

water vapour (clouds) and carbon dioxide.

Question 4

how is carbon dioxide removed from the environment (2)

Answer 4

photosynthesis and absorption by oceans

Question 5

where does methane come from (2)

Answer 5

from waterlogged habitats (like marshes) and landfills – it is also a gaseous waste produced by ruminants

Question 6

where do nitrogen oxides come from (2)

Answer 6

are released naturally by certain bacteria and also is emitted in the exhaust by certain vehicles

Question 7

composition of greenhouse gases

Answer 7

95% water vapour
3.6% CO2
1.4 others (nitrogen oxides, methane)

Question 8

methane as a greenhouse gas

Answer 8

Methane has a larger capacity to absorb long-wave radiation than carbon dioxide, but is significantly less abundant

Question 9

2 factors that determine the extent of impact greenhouse gases have in warming atmosphere

Answer 9

1. ability to absorb long-wave radiation - gases w greater capacity to absorb = greater impact
2. concentration within atmosphere (determined by rate of release and persistence within atmosphere)

Question 10

water vapour as a greenhouse gas

Answer 10

Water vapour enters the atmosphere rapidly but only remains for short periods, while carbon dioxide persists for years

Question 11

greenhouse effect

Answer 11

is a natural process whereby the atmosphere behaves like a greenhouse to trap and retain heat

Question 12

purpose of greenhouse effect

Answer 12

This ensures the Earth maintains the moderate temperatures needed by organisms to maintain life processes (homeostasis)
Without a greenhouse effect, Earth’s temperatures would drop significantly at night in the absence of direct sunlight

Question 12

how greenhouse effect works

Answer 12

The greenhouse effect functions to trap heat within the atmosphere and hence prevent rapid temperature fluctuations

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

Question 13

how do man increase greenhouse gas emissions(3)

Answer 13

1. deforestation
2. increased farming/agri
3. combustion

Question 14

enhance greenhouse effect leads to (3)

Answer 14

1. more frequent extreme weather conditions
2. some areas become more drought affected while others more prone to periods of heavy rainfall
3. chances to circulating ocean currents - cause longer El Nino(warming) and La Nina events (cooling)

Question 15

what does Vostok ice core tell us

Answer 15

Ice cores taken from the Vostok station in Antarctica provide evidence of the environmental conditions at the time of freezing
The Vostok ice core is one of the longest drilled, reaching back 420,000 years and covering the past four glacial cycles
By analysing the gas bubbles trapped in ice, historical CO2 levels and air temperatures (via oxygen isotopes) can be deduced

Data collected from the Vostok ice core demonstrates that:

There is a strong positive correlation between carbon dioxide concentrations and temperature (↑ CO2 levels ∝ ↑ temperature)
There have been fluctuating cycles of CO2 concentrations which appear to correlate with global warm ages and ice ages
Current concentrations of CO2 are higher than at any time recorded in the last 400,000 years

Question 16

ocean acidification

Answer 16

refers to a reduction in the pH of the ocean over an extended period of time, caused primarily by uptake of CO2 from the atmosphere

Question 17

impacts of increasing temperature CO2 solubility

Answer 17

CO2 solubility is temperature dependent (more soluble when cooler), so less CO2 will be absorbed as temperatures rise

Question 18

oceans as a carbon sink

Answer 18

The oceans are a major carbon sink and absorb roughly a third of all human produced (anthropomorphic) CO2 emissions

Question 19

what happens to atmospheric CO2 absorbed by oceans

Answer 19

When oceans absorb atmospheric CO2, some of it will remain dissolved in a gaseous state but most will be chemically modified:

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. With less free carbonate ions in the water, marine organisms are less able to produce calcium carbonate (via calcification) Calcium carbonate is used to form the hard exoskeleton of coral and is also present in the shells of certain molluscs
4. Hence increasing concentrations of dissolved carbon dioxide threatens the viability of coral reefs and certain molluscs

Question 20

impact of ocean acidification on marine organisms

Answer 20

the decrease in ocean pH is predicted to threaten the survival of marine organisms that require calcium carbonate

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
Experiments have shown that increasing water acidity correlates with the significant thinning of shells over several weeks
Corals, sea urchins and shelled molluscs do not exist in regions with high levels of dissolved CO2 (e.g. near hydrothermal vents)

Question 21

consequences of ocean acidification

Answer 21

1. The disappearance of coral reefs could result in a loss of shoreline protection and habitat, altering coastal ecosystems
2. The loss in revenue from tourism and food industries is predicted to cost economies upwards of $1 trillion by 2100
3. Increasing the dissolved CO2 levels in oceans would cause invasive species of algae to flourish (more photosynthesis)

Question 22

refute climate change Claim 1: Climate has changed in the past and current trends merely reflect the Earth’s natural climatic cycle

Data collected from the Vostok ice core shows several changes in climate over the last 400,000 years (Figure 1)
At several points in history, global average temperatures have been warmer than those currently observed

Answer 22

Climate changes do occur naturally, but usually not as abruptly as what is seen currently
When global warming occurred abruptly in the past, it was always highly destructive to life (e.g. Permian mass extinction)
Atmospheric CO2 levels positively correlate to average global temperatures and are currently at the highest levels ever recorded

Question 23

refute climate change denier claim

Claim 2: Climate change is being caused by solar activity and the effect of greenhouse gas emissions is negligible

Temperatures on Earth are influenced by the amount of solar radiation from the sun (more radiation = warmer temperatures)
Warmer temperatures may be caused by an increase in solar irradiance by the sun (as determined by the number of sunspots)

Answer 23

Counter Argument:

Over the last 35 years the sun has shown a slight cooling trend, however average global temperatures have increased (Figure 2)
There is no evidence to support a correlation between solar irradiance and current global temperature trends

Question 24

refute climate change denier claim

Claim 4: Variability between predicted climate change models means that such models are unreliable

Three different models of predicted climate change commissioned by the IPCC show variation of more than 5ºC (Figure 4)
Climate change models are based on assumptions and if those assumptions are false, the predictions will be incorrect

Answer 24

Counter Argument:

The assumptions made by the different models relate to the extent of human activity predicted over the next 100 years
Model A1B predicts a continued reliance on fossil fuels while model B1 predicts a reduction in the current use of raw materials
All three models still predict an increase in average global temperatures over the next 100 years

Question 25

refute climate change denier claim

Claim 3: Certain changes in climate conditions cannot be linked to greenhouse gas emissions

Global sea levels began to increase before greenhouse gas emissions significantly increased following the industrial revolution
Therefore climate changes like rising sea levels are unrelated to greenhouse gas emissions (Figure 3)

Answer 25

Counter Argument:

The overall pattern of change in sea levels will be influenced by the period of time over which the data is collected
While sea levels did increase preceding the industrial revolution, this rise in sea levels followed a preceding period of decrease
The rate at which sea levels have risen in the past 30 years is greater than that seen in the last 200 years

Question 26

refute climate change denier claim

Claim 5: Increases in greenhouse gas concentrations in the atmosphere will not be enough to cause significant climate change

As of 2009, there were only ~39 molecules of carbon dioxide per 100,000 molecules in the atmosphere
At our current rate of CO2 emission, it will take mankind another 5 years to raise that level by 1 molecule (to 40 per 100,000)
While we may double atmospheric CO2 levels by the end of the century, doubling a small number still produces a small number

Answer 26

Counter Argument:

The reason why carbon dioxide is so important to the environment is because there is so little of it
Living things require constant internal environments (homeostasis) – small external changes can have big impacts on viability