lecture 17: weather and climate

Question 1

global atmospheric circulation

Answer 1

polar cell: rising warm moist air, low pressure
farrel cell: descending cool, dry air, high pressure
hadley cell: rising warm moist air, low pressure

Question 2

weather vs climate

Answer 2

weather: meteorological condition at a given location and time, short term and localized
climate: meteroological condition that prevails in a region, long term and regional “statistics of weather” averaged over time

Question 3

3 causes of natural climate variations (1: plate tectonics)

Answer 3

continents near poles increases snow accumulation and glacier formaiton which increases albedo and reflects solar energy back to space
- ocean current brings warm water and increased precipitation to high lattitudes (ocean conveyer belt)

Question 4

3 causes of natural climate variations (2: solar irridance)

Answer 4

amount of solar energy received per unit on Earth
depends on:
1. total solar irridance produced at sun
2. orientation and distance of earth with respect to sun
- changes occur due to solar cycle

Question 5

sun spots (solar irridance)

Answer 5

storms on the surface of sun which mark 11 year peaks in solar output

• during periods, sun heats earth more
• sun and climate going in opposite directions (total irridance over last 400 years increased but last 50 years decrease)

Question 6

milankovitch cycles (solar irridance)

Answer 6

variations in earths astronomical movements (orbital Eccentricity, axial Tilt, and axial Precession) that influence solar irradiance on time scales of 1,000s to 100,000s of years
- explain large scale warming or cooling trends on geological time scales

Question 7

1. orbital eccentricity

Answer 7

changes in the earths orbit between nearly circular and more eliptical, averaging 100,000 years
- today cycle is nearly circular

Question 8

2. axial tilt (obliquity)

Answer 8

changes in earths axial tilt b/w 21.5-24.5
cycle of 41,000 years
greater tilt = greater extremes which results in decreased glaciation and warmer temperatures
tilt today is 23.5 which is large seasonal variations

Question 9

3. axial precession (wobble)

Answer 9

changes in earths wobble around its tilt axis
- from pointing at polaris (North star) to star vega
timespan of 19,000-23,000 years
today earth is closest to sun during northern hemisphere winter

Question 10

3 causes of natural climate variations (3: greenhouse gases)

Answer 10

climate is kept stable by natural emissions of greenhouse gases in atmosphere, feedback system keeps Earth at average of +15 degrees rather than -18 degrees

Question 11

what 4 things modulate atmospheric CO2

Answer 11

1. weathering of silicate rocks
2. volcanism
3. biology (marine organisms of CaCO3 shells
4. burial and subduction of carbon rich sediments

Question 12

how do we measure CO2 concentrations

Answer 12

air bubbles trapped in ice cores

- variations from 180-300ppm over 400,000 years

Question 13

anthropogenic sources of greenhouse gases

Answer 13

CO2- burning of fossil fuels and forests
CH4- decomposition of vegetation in absence of O2
N2O- chemical fertilizers and automotive combustion
O3- automotive/industrial gases (smog)
CFC- coolants and solvents (now banned)

Question 14

current rate of warming

Answer 14

0.7 degrees in 100 years
natural global warming occurs at most 1,000 years/C
10x faster and accelerating
models predict earth will warm between 2-6 degrees in the next century (20x faster)

Question 15

sea level rise

Answer 15

90% of heat absorbed by oceans which increases volume (thermal expansion) melting ice adds water to oceans
suggest 0.3-1.2m (30-120cm) by the end of century

Question 16

climate change impact: northern canada

Answer 16

• northwestern passage opened up for commercial maritime traffic
• potential for more arctic natural resource development
• melting permafrost weakens and undermines infrastructure
• wildlife adapted to cold climate shift northward by 150km for every degree of warming

Question 17

climate change impact: british columbia

Answer 17

• pacific waters too warm for sockeye salmon
• increased likelihood of more wildfires and longer fire seasons
• increased winter precipitation raises risk for spring snowmelt flooding
• higher winter precipitation also increases the risk for landslide and avalanches in mountanoious regions

Question 18

climate change impact: atlantic canada

Answer 18

• rising sea levels and greater storm activity will generate more powerful storm surges
• increased flooding, coastal erosion and property damage
• little chance for cod and salmon recovery, possibility for new invader species to take over

Question 19

climate change impact: ontario and quebec

Answer 19

• reduced water levels in the great lakes and St Lawrence river affects shipping and hydroelectric power generation
• reduced risk from snowmelt and ice jam flooding but higher of flash flooding
• longer and more severe heat waves
• potential for worse air pollution in the form of smog, airborne dust and ground level ozone

Question 20

climate change impact: prarie provinces

Answer 20

• longer growing season (longer frost-free period)
• reduced soil moisture and irrigation waters
• shrinking wetlands
• increased in drought frequency and severity
• crops more at risk to pests and disease

Question 21

climate change and hurricanes

Answer 21

rising ocean heat content provides more energy for tropical storms
- number of storms is increasing

Question 22

climate change and storm surges

Answer 22

sea level rise will also increase coastal vulnerability to storm surges

Question 23

climate change and wildfires

Answer 23

increase wildfire events

Question 24

climate change and earthquakes

Answer 24

Parvie fault scarp in sweden: Mw earthquake due to isostatic rebound
- melting of glacial ice