Lecture 9 and 10

Question 1

Anthropogenic influences on climate change, including time and spatial scale

Answer 1

Land use change - instantaneous, regional, comtinental
Aerosols - instantaneous + constant, regional
Ozone depletion - decades, mostly at poles but minor global affect too
Fossil fuels - decades/centuries, global

Question 2

What is Radiative forcing?

Answer 2

Most commonly used climate change metrics
Measures how the energy balance of the earth-atmosphere system is influenced when factors that affect climate are altered (IPCC)

Question 3

Concentration of a gas/pollutant is measured…

Answer 3

Molecules per cubic centimetre cm-3

Question 4

Gas/pollutant densities are measured…

Answer 4

Microgram per cubic metre

Question 5

What is the history of CO2 on earth?

Answer 5

40% increase from pre industrial
Atmospheric concentration of co2 in 2013 exceeds the natural range over last 650,000 yrs
2000-2010 average growth = 1.9ppm/yr
Primary source is fossil fuels and small contribution of land use change

Question 6

Methane

Answer 6

Principal component of natural gas
GH effect higher than CO2
Chemically active + has important role forming the tropospheric ozone
Emissions more uncertain than CO2
Principal loss process = chemical destruction (oxidation), inc. sunlight, oxygen, ozone and water vapour
Atmospheric Lifetime = approx 9 years

Question 7

Methane concentrations

Answer 7

More than doubled since 1800
Rate of increase recently smaller due to leakage control/ changes to oxidising capacity of the atmosphere
Stored in hydrates beneath sediments of ocean floor, if ocean temps increase could be released into atmosphere
Economic interest as new source of power
Methane plumes found in arctic waters from Sonar images

Question 8

Methane feedback mechanisms

Answer 8

Warming wetland peat
Subsea floor methane hydrate
Melting permafrost

Question 9

What do methane feedback mechanisms lead to?

Answer 9

Increase of global temperature

Question 10

How it the tropospheric ozone formed?

Answer 10

Sunlight + nitrogen oxide + volatile organic compounds + water vapour = ozone

Enhanced globally after industrial phase

Question 11

How does the stratospheric ozone form? (20-50km altitude)

Answer 11

Photodissociation of the oxygen molecule

Require SW radiation

Question 12

How is the ozone measured?

Answer 12

Satellites, laser beams, high-altitude aircraft, balloon sondes, large air craft, ground base systems

TOMS: total ozone mapping spectrometer
OMI: ozone measuring instrument

Question 13

What are Dobson units (DU) used to measure?

Answer 13

Total content of ozone in atmosphere (a vertical ‘ozone column’)

If you compress vertical ozone column to standard temp + pressure then a 1 mm thick ozone layer would correspond to 100 DU

Question 14

Principal steps in ozone depletion

Answer 14

Emissions
Accumulation 
Transport
Conversion 
Chemical reaction 
Removal

Question 15

How is stratospheric ozone destroyed?

Answer 15

Catalytic cycles

Question 16

In the stratosphere, how are reactive halogen gases and ‘reservoir gases’ formed?

Answer 16

CFCs (chemically inert at lower altitudes) broken up by UV light (photolysed) and the halogen atoms react

Question 17

Where is ozone depletion strongest?

Answer 17

Polar stratosphere - formation of reactive halogens is particularly effective

Question 18

Conditions for ozone depletion (at the poles)

Answer 18

Low temperatures (formation of PSC) 
Isolated conditions (chemical processes) 
Polar stratospheric clouds (reaction on surface of cloud crystals increases destruction efficiency by 100x)

Question 19

Ozone destruction - at higher latitudes there is…

Answer 19

Lower temperatures which mean less depletion due to slower reactions

Question 20

At which summit, did the monitoring by TOMs show that the ozone hole was stabilised because of emission reduction?

Answer 20

Rio 1992

Question 21

The decrease in the stratospheric ozone layer has what effects?

Answer 21

Small cooling effect on global temperatures

Increase in UV radiation - particularly in Southern Hemisphere, caused more skin cancer cases

Question 22

When is full recovery expected for the ozone?

Answer 22

By 2050 in mid latitudes, Antarctica will occur later

Question 23

Direct effects of aerosols

E.g.

Answer 23

Eruption of mount Pinatubo 1991
Approx 10km3 material ejected
Noticeable drop in temperatures, called ‘volcanic winter’
Impressive sunsets worldwide

Question 24

Indirect aerosol effects

Answer 24

Not related to direct interface of the particle with radiation
Important effect = impact on cloud droplet size which affects clouds albedo and amount of precipitation
Further effects = impacts on heterogenous chemistry, cloud condensation processes etc

Question 25

Polluted cloud =

Answer 25

Higher albedo
Smaller cloud particles –> Less precipitation
Higher optical depth = less radiation at surface

Question 26

Ozone photosmog (LA type smog)

Answer 26

High NOx emissions
Large concentration of vocs
Lots of sunlight 
Low wind speed and atmospheric stable conditions (inversion) 
Can last several days
Respiratory problems 
Affects plants and crop yields
Oxidation of materials

Question 27

Atmospheric brown clouds example

Answer 27

East Asia - thick 200km wide and 600 km long covers a part of E.China sea on March 4 1996
Haze = mix of industrial air pollution, dust and smoke

Question 28

Regional hotspots for atmospheric brown clouds

Answer 28

E. Asia
Indo-Gangetic Plain in S. Asia
S.E Asia
S. Africa 
Amazon basin

Question 29

Radiative impacts of atmospheric brown clouds

Answer 29

Dimming of solar irradiance at surface (about 6% in China and India)
Increase in atmospheric solar heating (black carbon, soot)
Black carbon = responsible for 15% increase of average annual mean absorption in troposphere

Question 30

Atmospheric brown cloud meteorological impacts

Answer 30

Changes in rainfall patterns (patterns shifted in China, due to dimming)
Increased receding and thinning of glaciers - albedo changes and temperature increases

Question 31

Atmospheric brown cloud consequences/impacts

Answer 31

Changes in monsoon rainfall and glacier extent will affect water levels required for irrigation of crops
Ground level ozone increases will affect crop yields
Health from indoor and outdoor pollutions

Question 32

Land use change impacts

Answer 32

Affects albedo

Global temperature increased by 0.76 degrees c since pre-industrial times

Question 33

IPCC 2013 summary of global change

Answer 33

Ocean temps increased until 3000m depth and absorb 80% of heat added to system
20th c sea level rise = 0.17m
Change in sea ice cover, polar ice caps, snow cover
Arctic temp increase approx twice that of global increase

Question 34

What is Global warming?

Answer 34

Increase in globally and annually averaged air temperature near the surface. This warming is also observed e.g. In ocean and soil temperatures

Question 35

What is ‘climate change’?

Answer 35

A significant and persistent change in the mean state of the climate/it’s variability. As such it’s not exclusively tied to temperature change.

Question 36

Global warming is mainly due to…

Answer 36

Human activity

Not every place will increase/decrease in temp/rainfall at the same rate

Question 37

what are the natural influences on climate change and their time + spatial scale?

Answer 37

Plate tectonics - mil of yrs, regional
Volcanic activity - years, longer if ‘mega’ and regional + global
Solar irradiance - 11 yrs/much longer, global
Outgassing from volcanoes + oceans - millennia, global