Bio 4 Flashcards
4.4 List some
examples, and
explain the
formation and
effect of
greenhouse gases.
Greenhouse gases absorb and emit long-wave
(infrared) radiation, thereby trapping and holding
heat within the atmosphere
• Carbon dioxide and water vapor are the most
significant greenhouse gases
• Other gases including methane and nitrogen
oxides have less impact
-CH4 is emitted from waterlogged habitats (like
marshes) and landfills - it is also a gaseous waste
produced by ruminants
-nitrogen oxides are released naturally by certain
bacteria and also is emitted in the exhaust by
certain vehicles
• The impact of a gas depends on its ability to
absorb long-wave radiation as well as its
concentration within
the atmosphere
-gases that have a greater capacity to absorb
long-wave radiation will have a greater warming
impact (per molecule)
-the greater the concentration of a gas, the
greater its warming impact will be within the
atmosphere
**methane has a larger capacity to absorb long-wave radiation than carbon dioxide, but is
significantly less abundant
• The warmed Earth emits longer wavelength
radiation (heat)
• Longer wave radiation is absorbed by
greenhouse gases that retain the heat in the
atmosphere
-incoming radiation from the sun is shorter wave
radiation (ultraviolet radiation and the visible
spectrum)
-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
4.4 Describe the
increase in
atmospheric [CO2]
and its effect.
• Recent increases in atmospheric CO2 are largely
due to increases in the combustion of fossilised
organic matter
While greenhouse gases occur naturally, man is
increasing greenhouse gas emission via a number
of activities, including:
-deforestation
-increased farming / agriculture
-combustion
The greenhouse gas that is increasing most
rapidly in the atmosphere is carbon dioxide and
the main cause is combustion
-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)
• Global temperatures and climate patterns are
influenced by concentration of greenhouse gases
-greenhouse gases can retain heat
-increases in greenhouse gas concentrations
should correlate with an increase in global
temperature
Scientists predict that increases in greenhouse gas concentrations will lead to an enhanced
greenhouse effect, resulting in:
-more frequent extreme weather conditions (e.g.
heat waves, cyclones, more powerful tropical
storms, etc.)
-some areas to become more drought affected,
while other areas become more prone to periods
of heavy rainfall
-changes to circulating ocean currents
• Threats to coral reefs from increasing
concentrations of dissolved carbon dioxide
4.4 Application:
Explain ocean
acidification.
• Threats to coral reefs from increasing
concentrations of dissolved carbon dioxide
-oceans are a major carbon sink and absorb
roughly a third of all human produced
(anthropomorphic) CO2 emissions
**CO2 solubility is temperature dependent (more
soluble when cooler), so less CO2 will be
absorbed as temperatures rise
When oceans absorb atmospheric CO2, some of it
will remain dissolved in a gaseous state but most will be chemically modified:
-CO2 combines with water to form carbonic acid
(H2CO3), which dissociates into H+ ions and
HCO3
-H+ ions 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
-increasing concentrations of dissolved carbon
dioxide threatens the viability of coral reefs and
certain molluscs
-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
Consequences of Ocean Acidification:
-disappearance of coral reefs -> loss of shoreline
protection and habitat, altering coastal
ecosystems
-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)
4.4 Application:
Evaluating claims
that human activities
are not causing
climate change.
Claim 1: Climate has
changed in the past
and current trends
merely reflect the
Earth’s natural
climatic cycle
Claim 2: Climate
change is being
caused by solar
activity and the
effect of
greenhouse gas
emissions is
negligible.
Claim 3: Certain
changes in climate
conditions (e.g.
rising sea levels)
cannot be linked to
greenhouse gas
emissions
Possible claims raised by septics of human-
induced climate change:
-counterarguments
Claim 1: Climate has changed in the past and
current trends merely reflect the Earth’s natural
climatic cycle
-they do occur naturally, but usually not as
abruptly as what is seen currently
-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 currentlv at
the highest levels ever recorded
Claim 2: Climate change is being caused by solar
activity and the effect of greenhouse gas
emissions is negligible.
-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
Claim 3: Certain changes in climate conditions
(e.g. rising sea levels) cannot be linked to
greenhouse gas emissions
-overall pattern of change in sea levels will be
influenced by the period of time over which the
data is collected
-sea levels did increase preceding the industrial
revolution, but 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
4.4 List greenhouse
gases found in the
atmosphere
The primary greenhouse gases in Earth’s
atmosphere are water vapor, carbon dioxide,
methane, nitrous oxide and ozone.
4.4 State the
sources of CO2 and
water in the
atmosphere
CO2:
-organisms respire
-organisms decompose
-carbonate rocks are weathered
-forest fires occur
-volcanoes erupt.
-human activities, such as the burning of fossil
fuels and forests and the production of cement
Water:
-evaporation of water during the water cycle. In
the atmosphere
-water exists as a gas (water vapor from
evaporation), as a liquid (droplets of rain), and as
a solid (snow and ice).
4.4 Define
“greenhouse effect.”
the natural process by which radiation (heat) is
trapped by a planet’s atmosphere, warming the
planet’s surface to a temperature above what it
would be without its atmosphere.
4.4 State the
sources of nitrous
oxide gas in the
atmosphere
Human activities such as:
-agriculture
-fuel combustion
-wastewater management
-industrial processes
are increasing the amount of nitrous oxide (N20)
gas in the atmosphere. Nitrous oxide is also
naturally present in the atmosphere as part of the
Earth’s nitrogen cycle, and has a variety of natural
sources.
4.4 State two
factors that
determine the
warming impact of a
greenhouse gas.
-ability to absorb longwave radiation (only certain
in the atmosphere have the ability to trap
long wave radiation and therefore act as a a greenhouse gas).
-abundance of the gas in the atmosphere (the
amount of a particular gas in the atmosphere).
4.4 State two
variables that
determine the
concentration of a
gas in the
atmosphere
- Rate of release of the gas into the atmosphere.
- How long the gas persists in the atmosphere
once it is there.
4.4 Define
“enhanced
greenhouse effect”
The disruption to Earth’s climate equilibrium
caused by the increased concentrations of
greenhouse gases has led to an increase in the
global average surface temperatures. This
process is called the enhanced greenhouse
effect.
4.4 Explain how
historical
temperature data
has been collected.
Direct measurements of atmospheric gases have
been made over the past 50 years.
-for historical data, analysis of air bubbles
trapped in ancient ice, show that levels of carbon
dioxide, methane, nitrous oxide and halocarbons
are increasing.
-the Vostok ice core (from Antarctica) is one of
the longest drilled, with ice dated to 420,000
years old
-by analyzing the gas bubbles trapped in ice,
historical CO2 levels and air temperatures can be
deduced.
4.4 Outline reasons
why there is
vigorous debate
around the claim
that human activities
are causing climate
change.
The causes and effects of climate change have
stirred vigorous debate because:
1. There is a degree of uncertainty in mathematical
models used to predict consequences.
2. Climate patterns are complex with many variables.
3. Possible solutions to climate change will cost
money and require government regulation.
4. Economic dependence on a fossil fuel based
economy.
5. Correlation does not imply causation
4.4 Suggest
measures that can
be taken to reduce
the emission of
methane.
drain swamps and marshes;
reduce cattle and sheep farming;
stop growing rice in paddies;
control releases of natural gas;
reduce burning of coal;
prevent forest fires/burning of biomass;
4.4 Explain the falls
of CO2
concentration from
May to October
and rises from
November to April.
CO2 falls due to photosynthesis;
photosynthesis exceeds respiration in summer;
respiration exceeds photosynthesis in winter;
May to October are summer in Northern
hemisphere
