Week 12 Flashcards
1
Q
What is climate change
A
- a change in global or regional climate patterns
- Climate: weather across a broad area averaged over a long period of time (usually at least 30 years)
2
Q
What naturally changes the climate? pt 1
A
- Earth is warmed by solar energy from the sun
- Amount of solar energy to reach a point on earth’s surface depends on time of day, time of year and position relative to equator
3
Q
Earth’s climate system
A
- Climate: long term atmospheric conditions in a region
- Earth’s climate includes interactions of:
1. Atmosphere: includes a mixture of gases that surround the planet
2. Geosphere: includes the crust, mantle, and inner and outer core
3. Hydrosphere: planet’s water system
4. Biosphere: all living things
5. Cryosphere - Climate system: exchanges of energy and moisture between these spheres
- Energy is mainly stored and sequestered in the atmosphere, ocean, land and ice
4
Q
Earth’s atmosphere
A
- atmospheric layers:
1. ionosphere: above these layers
2. mesosphere: up to 90 km
3. stratosphere: up to 50 km
4. troposphere: 10 to 18 km - atmospheric content: 78% N, 21% O, less than 1% Ar, CO2 and other trace gases; water vapor 1-4% on average
5
Q
Intro to Greenhouse gases
A
- the earth would be -19 degrees without atmosphere
- 99% of the atmosphere is nitrogen and oxygen, which are transparent to radiation
- Greenhouse gases include
1. water vapor 60%
2 carbon dioxide 26%
3. ozone 8%
4. methane 6%
6
Q
What naturally changes the climate? pt 2
A
- Earth’s surface temperature is influenced by how much sunlight is reflected and absorbed
- Studies of greenland and antarcitc glaciers show ice ages, alternating with warmer periods, over last two million years
- possible explanation for ice ages: variation in earth’s orbit and rotation- orbital changes called Milankovitch cycles. These correspond well with at least 20 ice ages
7
Q
What naturally changes the climate? pt 3
A
- Variations in earth’s orbit
- Milankovitch theories
1. Eccentricity of earth’s orbit - High eccentricity: more elliptical
- Low eccentricity: more circular
2. Obliquity of earth’s axis - more tilt: more sun in summer, less in winter
3. Precession of earth’s axis - due to wobble of the axis
- impact due to elliptical nature of orbit
8
Q
Sulfur dioxide
A
- Volcanic eruptions
- Volcanic ejecta may block sunlight
- Need many eruptions in short time period
- Not observed in recent history
9
Q
Earth’s energy balance
A
- energy from the sun must be balanced by energy lost back into space
- if not have radiative forcing: difference in energy between top of troposphere and energy below it
- +ve RF (more incoming than outgoing radiation) warms earth
- -ve RF cools earth
10
Q
Physical processes: the carbon cycle
A
- CO2 from human activities greater than CO2 plants and oceans can uptake
- Greenhouse gases prevent long-wave heat radiation escaping, and also reflect short wave radiation back to space
11
Q
Greenhouse gases
A
- Natural greenhouse gases:
- Water vapor mostly evaporated from oceans
- CO2 and Ch4 emitted by erupting volcanoes, animals, decaying vegetation, and forest fires
- NOx generated during lightning storms - Greenhouse gases are also by products of human activites such as burning fossil fuels
- Pollution: major source of atmospheric particles, particularly affecting developing countries
- A 3-km thick cloud of smoke, soot, and dust found over Indian ocean (caused by using cow dung as cooking fuel): cools ocean’s surface, reducing evaporation and causing drought
12
Q
Positive feedback loop
A
- even if human-caused CO2 emissions stopped today. amount added to oceans would slowly release back, preventing significant atmospheric temperature drop for at least 1000 years
1. more CO2 generated warms atmosphere and oceans
2. Warmed ocean releases more CO2 into atmosphere
3. More Co2 in atmosphere causes more warming, a positive feedback effect
13
Q
Consequences of climate change: sea level rise
A
- Coastal areas flood
- salt water contaminates freshwater aquifers
- low levees overtopped during floods
- Coastal populations displaced
Example: Bangladesh would lose more than 17 percent of its land with 1 m sea-level rise: - annual floods affect around 20 percent of land today
- raising levees would be cost prohibitive
14
Q
Consequence of climate change: changes to global oceanic circulation
A
- Ocean salinity changes (from melting glaciers and ice sheets) could alter path and strength of Gulf stream
- resulting in cooling in western europe
15
Q
Consequence of climate change: more extreme and severe weather
A
- most of earth’s near surface heat is concentrated in the oceans
- warmer oceans lead to greater evaporation and more rainfall - Ocean heat contributes significantly to the energy that drives storms
- Warmer seas will cause stronger, more frequent storms
- Changes in circulation patterns may mean storms extend further to the N and S
