Anthropogenic climate change

Question 1

Anthropogenic?

Answer 1

Caused by humans

Question 2

Radiative forcing?

Answer 2

Change in energy flux of atmosphere caused by climate change
-Amount of energy entering different to amount of energy leaving

Question 3

Positive feedback?

Answer 3

Loop where something occurs which causes effects which allows it to happen more.

Question 4

Causes of short term climate change?

Answer 4

-External
solar variability
volcanic activity
-Internal
atm. concs. of radiatively active gases,
albedos of surface and clouds
Effects of human activity match or exceed changes from natural processes

Question 5

Process of radiatively active gases increasing temperature?

Answer 5

-Radiatively active gases transparent to short wave radiation - let them in
-Opaque to long wave radiation - blocks
- Short waves converted to long wavs when reflected
-Traps reflecting long waves and so radiative energy in atmosphere - surface warms
- Called greenhouse effect

Question 6

Surface temp. of earth without greenhouse gases? (Mostly Co2 and water vapour)

Answer 6

-19 degrees instead of over 15 degrees

Question 7

What other gases impact climate change besides CO2?

Answer 7

Methane
Nitrous Oxide
Ozone/trioxygen
halocarbons
- May be responsible for half expected warming

Question 8

Indirect affects of non-radiatively gases?

Answer 8

-Oxidation of carbon monoxide (CO) to CO2
-Hydroxide (OH) concentration controls lifetime of carbon monoxide (CO) and methane (CH4)

Question 9

What does aerosol formation lead to?

Answer 9

Scattering or reflecting of incoming _ radiation.
E.g. sulfur to sulfate

Question 10

What causes thermal fragility of atmosphere?

Answer 10

Greenhouse gases make up less than 1% of the atmosphere’s mass.

Question 11

Atmospheric concentrations of greenhouse gases increasing due to?

Answer 11

-CO2 – fossil fuel combustion; land-use changes
-Methane (CH4) – fossil fuel extraction and use; sewage treatment; landfill; animal waste; rice paddies; biomass burning
-Nitrous oxide (N2O) – cultivated soils; industrial activities; biomass burning
-Halocarbons – refrigeration; air conditioning
- Sulfur dioxide (SO2) – coal combustion; smelting.

Question 12

What effects the contribution as gas makes to greenhouse effect (Radiative forcing)?

Answer 12

-Wavelength where gas absorbs infrared radiation
-Concentration of gas
-Whether other gases present absorb at same wavelength
-Atmospheric lifetime of the gas

Question 13

Earth’s radiation spectrum?

Answer 13

4-100 micrometres

Question 14

Absorption of infrared radiation at high concentrations of water vapour and co2?

Answer 14

-Almost complete absorption at numerous wavelengths.
-As absorption increases logarithmically with concentration

Question 15

Absorption of water vapour and Co2 at 7-13 micrometeres?

Answer 15

-Weak as radiation peaks at 10 micrometres.
- Called atmospheric window
- Most other greenhouse gases have absorption lines (weaker intensity) in this region.

Question 16

Response of greenhouses gases to radiation spectrum?

Answer 16

-CH4, N2O: absorption increases as square root of concentration.
-Halocarbons: little overlap with absorption lines (weaker intensity) of other gases present (absorption increases linearly with concentration)
-Comparable increases in concentration have greatly differing radiative forcing effects

Question 17

Define global warming potential?

Answer 17

-Comparative measure of how much heat is trapped by 1 kg of a gas relative to 1 kg of CO2 over a 100 y timescale.
-Considers radiative forcing and residence time.

Question 18

Global warming potential of Co2, Ch4, N2O, CF2CI2, SF6?

Answer 18

CO2 = 1
CH4 = 28
N2O = 298
CF2Cl2 = 10,900
SF6 = 22,800

Question 19

Why are we primarily concerned about increases in CO2 when its potency relative to other GHGs is so low?

Answer 19

-Emissions and increases in concentration of CO2 much greater than other GHGs
- Co2 - annual emissions = 36,800 - annual increase = 0.61.
- Next highest - ch4 - annual emissions = 16,000 - annual increase = 0.48.

Question 20

Optical depth of atmosphere? Features?

Answer 20

-Mean altitude where infrared rad. emitted to space to maintain Earth’s radiation balance.
-Occurs in the troposphere at altitude corresponding to 254 K (-19 degrees)
-Present altitude 6.5 km

Question 21

How does increased greenhouse gas concentration effect optical depth?

Answer 21

-Increases optical depth altitude
- By 23 metres per decade
- Consistent with Earth surface warming rates of 0.12 – 0.18 degrees per decade

Question 22

Historical progression of radiative forcing?

Answer 22

-Forcing will increase co2 to contribute 60% for all greenhouse gases.
-Forcing offset by aerosols and land use changes
-Improvements in urban air quality in developed nations could be accelerated warming
-Natural forces (solar and volcanic effects) have a minor influence on forcing

Question 23

Use Frankie and Shannon’s media for equations.

Answer 23

Yeah do that.

Question 24

Radiating temperature of earth?

Answer 24

-19 degrees.

Question 25

Range of temperature change from radiative forcing?

Answer 25

1.5-4.5 degrees at equilibrium.

Question 26

Feedback response by water vapour to radiative forcing?

Answer 26

-Warmer climate increases capacity of atmosphere to hold Water Vapour
-Water vapour increases
-Positive feedback – more water vapour to trap radiation.

Question 27

Feedback response by clouds to radiative forcing?

Answer 27

-Clouds reflect long wave solar radiation = cooling
- Clouds absorb Infrared radiation from surface which increases warming (cloud tops colder) = emission < absorption
-Feedback depends on cloud altitude
Thicker clouds cause warming - positive feedback
Lower altitude clouds cause cooling - negative feedback

Question 28

Feedback response by areal extent of ice and snow to radiative forcing?

Answer 28

-Lower Iceland snow cover means lower albedo
-Leads to positive feedback as ice and snow reflect more energy than they absorb so if they reduce that cant happen
-Called Polar amplification of global warming

Question 29

Feedback response by vegetation to radiative forcing?

Answer 29

Changes in distribution of biomes causes changes in albedo – so radiative forcing can inc. or dec.

Question 30

Feedback response by the carbon cycle to radiative forcing?

Answer 30

Changes in sources and sinks of CH4 and CO2 causes changes in atmospheric concentrations – so can inc. or dec.

Question 31

Feedback response times of water vapour, clouds, sea ice and snow, vegetation, carbon cycle, continental ice sheets?

Answer 31

Water Vapour, clouds: instantaneous
Sea ice and snow: years
Vegetation changes and some carbon cycle processes: decades
Changes to continental ice sheets: 103  104 y

Question 32

Effect of increased emissions on ocean sink of carbon?

Answer 32

-Increased atmospheric CO2 leads to diffusion into oceanic surface mixed layer driven by equilibrium.
-Mixing of high CO2 surface waters down through water column through turbulent diffusion and convective overturning leads to possible further absorption from atmosphere.
-Absorption further increased by dissolution of carbonate sediments.
Increased CO2 in surface waters leads to decreased CO32
CO32 depleted water mixing down to deep ocean leads to increased rate of dissolution of carbonate sediments
CO32 rich water mixed back to surface leads to increased capacity for surface waters to absorb atmospheric CO2.

Question 33

True or false? Oceans could absorb 75 to 80 % of CO2 added to atmosphere over 10^3 years.

Answer 33

True.

Question 34

Ocean acidification facts you know.

Answer 34

-By end of 20th century – over 1000 ppm
-CO2 bonds with H makes carbonate (carbonic acid) carbonate bonds with excess hydrogen to make bicarbonate ions, so less carbonate to make calcium carbonate

Question 35

True or false? Oceans could absorb 85 to 90 % of CO2 added to atmosphere over 103 to 104 years.

Answer 35

True.

Question 36

Effect of climate change on ocean sink?

Answer 36

-Warming of surface mixed layer leads to increased solubility of CO2.
-Weakening of thermohaline overturning leads to a decrease in rate of mixing of CO2 into deep ocean.

Question 37

Effect of increased emissions on terrestrial sink (plants) of carbon?

Answer 37

-Increased co2 leads to increased photosynthesis in C3 plants
So increases plant growth especially when under stress
Initial simulation declines by max 2 thirds - downregulation
-Higher temperatures leads to increased photosynthesis and respiration
Increased respiration leads to increased net remineralization leads to increased net photosynthesis.

Question 38

Effect of climate change from increased emissions on terrestrial sink (animals) of carbon?

Answer 38

-Climate changes may be too fast for species distributions to respond.
-Collapse of communities leads to decreased carbon storage leads to increased atmospheric CO2.
-Re-establishment of new species on 10^2 to 10^3 year timescales.
- Present magnitude of terrestrial sink appears to compensate for effect of land use changes.

Question 39

Impacts of changing climate from increased emissions on world?

Answer 39

-Changes in rainfall totals and increased frequency of extreme events (droughts/floods).
-Increased frequency of wild fires
-Sea level rise