4.4 climate change Flashcards
how do greenhouse gases trap heat?
greenhouse gases absorbs and emit long-wave (infrared) radiation, thereby trapping and holding heat within the atmosphere.
greenhouse gases make up ________of atmosphere
less than 1% collectively
greenhouse gases which have the largest warming effect within the atmosphere are
water vapour (clouds) and carbon dioxide.
how is carbon dioxide removed from the environment (2)
photosynthesis and absorption by oceans
where does methane come from (2)
from waterlogged habitats (like marshes) and landfills – it is also a gaseous waste produced by ruminants
where do nitrogen oxides come from (2)
are released naturally by certain bacteria and also is emitted in the exhaust by certain vehicles
composition of greenhouse gases
95% water vapour
3.6% CO2
1.4 others (nitrogen oxides, methane)
methane as a greenhouse gas
Methane has a larger capacity to absorb long-wave radiation than carbon dioxide, but is significantly less abundant
2 factors that determine the extent of impact greenhouse gases have in warming atmosphere
- ability to absorb long-wave radiation - gases w greater capacity to absorb = greater impact
- concentration within atmosphere (determined by rate of release and persistence within atmosphere)
water vapour as a greenhouse gas
Water vapour enters the atmosphere rapidly but only remains for short periods, while carbon dioxide persists for years
greenhouse effect
is a natural process whereby the atmosphere behaves like a greenhouse to trap and retain heat
purpose of greenhouse effect
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
how greenhouse effect works
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
how do man increase greenhouse gas emissions(3)
- deforestation
- increased farming/agri
- combustion
enhance greenhouse effect leads to (3)
- more frequent extreme weather conditions
- some areas become more drought affected while others more prone to periods of heavy rainfall
- chances to circulating ocean currents - cause longer El Nino(warming) and La Nina events (cooling)
what does Vostok ice core tell us
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
ocean acidification
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
impacts of increasing temperature CO2 solubility
CO2 solubility is temperature dependent (more soluble when cooler), so less CO2 will be absorbed as temperatures rise
oceans as a carbon sink
The oceans are a major carbon sink and absorb roughly a third of all human produced (anthropomorphic) CO2 emissions
what happens to atmospheric CO2 absorbed by oceans
When oceans absorb atmospheric CO2, some of it will remain dissolved in a gaseous state but most will be chemically modified:
- Carbon dioxide will combine with water to form carbonic acid, which dissociates into hydrogen ions and hydrogen carbonate
- H+ ions will lower the ocean pH (acidification) and will also combine with free carbonate ions to form more hydrogen carbonate
- 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
- Hence increasing concentrations of dissolved carbon dioxide threatens the viability of coral reefs and certain molluscs
impact of ocean acidification on marine organisms
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)
consequences of ocean acidification
- The disappearance of coral reefs could result in a loss of shoreline protection and habitat, altering coastal ecosystems
- The loss in revenue from tourism and food industries is predicted to cost economies upwards of $1 trillion by 2100
- Increasing the dissolved CO2 levels in oceans would cause invasive species of algae to flourish (more photosynthesis)
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
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
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)
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
