lecture 17: weather and climate Flashcards
global atmospheric circulation
polar cell: rising warm moist air, low pressure
farrel cell: descending cool, dry air, high pressure
hadley cell: rising warm moist air, low pressure
weather vs climate
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
3 causes of natural climate variations (1: plate tectonics)
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)
3 causes of natural climate variations (2: solar irridance)
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
sun spots (solar irridance)
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)
milankovitch cycles (solar irridance)
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
- orbital eccentricity
changes in the earths orbit between nearly circular and more eliptical, averaging 100,000 years
- today cycle is nearly circular
- axial tilt (obliquity)
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
- axial precession (wobble)
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
3 causes of natural climate variations (3: greenhouse gases)
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
what 4 things modulate atmospheric CO2
- weathering of silicate rocks
- volcanism
- biology (marine organisms of CaCO3 shells
- burial and subduction of carbon rich sediments
how do we measure CO2 concentrations
air bubbles trapped in ice cores
- variations from 180-300ppm over 400,000 years
anthropogenic sources of greenhouse gases
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)
current rate of warming
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)
sea level rise
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
climate change impact: northern canada
- 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
climate change impact: british columbia
- 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
climate change impact: atlantic canada
- 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
climate change impact: ontario and quebec
- 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
climate change impact: prarie provinces
- 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
climate change and hurricanes
rising ocean heat content provides more energy for tropical storms
- number of storms is increasing
climate change and storm surges
sea level rise will also increase coastal vulnerability to storm surges
climate change and wildfires
increase wildfire events
climate change and earthquakes
Parvie fault scarp in sweden: Mw earthquake due to isostatic rebound
- melting of glacial ice
