Lecture 5 + 6 Flashcards
True or False: A scientist is working on a study. They have the option to increase their sample size with minimal effort and cost. The scientist decides to not increase their sample size.
This scientist made a good decision.
False because a large sample size is almost always better because it makes the sample mean closer to the true population mean. Therefore, statistically, we can have more confidence in the results.
Two studies are conducted. The studies concern how much time gerbils spend looking for food when they are hungry vs. when they are not hungry. The scientists in both studies predict that animals that are hungry will spend more time looking for food.
The first study finds that animals that are hungry spend 5 hours looking for food, and animals that are not hungry spend 3 hours looking for food.
The second study finds that animals that are hungry spend 6 hours looking for food, and animals that are not hungry spend 3 hours looking for food.
If everything else is equal which study is more likely to have significant results?
The second study because there is a great difference in means. It has a larger effect size.
How would you determine if a graph is significant or not?
- consider sample size
- consider variance
- consider effect size
p value below 0.05
The spinning of the Earth affects the motion of air masses. This effect is referred to as the ________________.
Coriolis effect
Which of the following are responsible for how heat moves across Earth : (Select one or more answers)
- Hadley Cells
- Coreopsis Effect
- Ferrel Cells
- Polar Cells
Hadley cells
Ferrel cells
Polar cells
Which direction do prevailing surface winds blow in temperate latitudes?
West to East
Because of how sunlight hits the surface of Earth:
- Heating by sunlight is greater at the North and South Poles
- Heating by sunlight is greater at the Equator
- Temperatures are cooler at the Equator
- The earth is uniformly heated
Heating by sunlight is greater at the Equator
Is the greenhouse gas effect good or bad for life on Earth?
Good for the most part. Bad with human caused climate change.
- average temp on Earth = 13ºC
- without ghg would be -17ºC
Mars has far fewer ghg (-55ºC)
Venus has far more ghg (460ºC)
Which is the most important greenhouse gas?
Water vapour
- But carbon dioxide, methane, ozone, and nitrous oxide are important
-> they fill in “holes” in the infra red spectrum not
filled by water vapour
- And these are the gases human activity has changed the most
Variation in climate is driven by many factors, including:
Changes in sunlight intensity (solar flaring or “sun spots”
Volcanic eruptions
Changes in the tilt of the Earth
Changes in ocean circulation
Changes in greenhouse gases (from natural or human sources)
When did most warming occur?
Most has occurred since 1980
- human activity has warmed the climate to levels not seen on Earth in at least past 100,000 years, leading already to large climatic disruptions
The fact that carbon dioxide
is a greenhouse gas was first articulated in the scientific literature:
a) by a chemist in the US in in the 1850s
b) by a Swedish chemist in the 1890s
c) by an atmospheric physicist in Germany in the 1920s
d) by oceanographers in the US in the 1950s
e) by environmental scientists in Europe in the late 1960s, leading to the first Earth Day in 1970
a) by a chemist in the US in in the 1850s
- Eunice Foote was the first
scientist to note the role of
carbon dioxide in the
greenhouse gas effect,
in a paper delivered to the
American Association for the
Advancement of Science (AAAS) and published in 1856
(before the Civil War!)
- Eunice Foote lived in
Seneca Falls NY (40 miles
from Ithaca, at the
northern end of Cayuga
Lake) and was also a leader
in the women’s suffrage
struggle, including the
1848 Woman’s Rights
Convention.
- Other scientists, particularly the Irish physicist John Tyndall, followed up on the preliminary work of Eunice Foote, and the role of CO2 as a greenhouse gas was universally accepted by 1870.
Svante Arrhenius (1859-1927), a Swedish chemist,
wrote a book in 1896 on how the burning of fossil
fuels could contribute to global warming through
release of CO2, contributing to the greenhouse effect.
Predicted a doubling of CO2 would warm Earth by 1.6ºC to 6ºC
(IPCC 2013 says 2°to 4.5ºC)
Predicted it would take 3,000 years for fossil fuel burning to double CO2
(at current trends, it will take another 60 years)
-> could not have predicted the exploitation of fossil fuels
Rate of global warming
is 20-fold higher than ever before
COP 21 Paris Accord
- target: “well below 2ºC”
- clear recognition that warming beyond 1.5ºC is dangerous
- already at/slightly past 1.5ºC
Earth climate model
Earth’s climate is stable within certain limits. If global warming is small, climate will return to a stable balance. If it is large, there will be dangerous effects.
- Global warming over the next few decades may well be sufficient to push the Earth into a different climatic regime.
-> At that point, reducing greenhouse gas emissions may no longer reverse global warming and climate disruption, on the time scale of 10,000 years or more.
Tipping points
Critical thresholds in a system that, when exceeded, can lead to a significant change in the state of the system, often with an understanding that the change is irreversible
- Uncertainty as to when tipping points will be hit, but increasing risk in yellow, high risk shown by red
Heat is distributed from the equator towards the
temperate zones and poles:
A) mostly through the atmosphere (winds)
B) mostly through the oceans (currents)
C) almost equally through the atmosphere and oceans
C) almost equally through the atmosphere and oceans (60% and 40% respectively)
- MUCH greater storage of heat in oceans (water has far greater capacity for storing heat than does air).
- (90% of global warming has occurred in oceans, only 10%
in atmosphere)
- But air masses move much more quickly than does water (less viscous)
Sun heat at equator
- The sun heats Earth’s surface most intensely at the equator
- This heating leads to uplift of the air
Globally, three sets of cells set up
- polar
- temperate
- tropics
- tropics
- temperate
- polar
Hadley cells
Driven by uplift of warm air at equator
- adiabatic cooling at equator creates rain
Polar cells
Driven by subsidence of cold air at poles
Ferrel cells
Driven by interaction of Hadley and polar cells
Adiabatic cooling
Temperature of a gas is directly proportional to its pressure (universal gas laws)
- as an air mass rises in the atmosphere, its pressure is less, so it cools
-> cool air cannot hold as much water vapour, so condensation, clouds, and precipitation
Hadley cell latitudes
30ºN: high pressure –subtropical highs
0º: low pressure, equatorial regions –tropical lows
30ºS: high pressure – subtropical highs
Air masses descending at 30º warm as pressure increases. This lowers relative humidity -> very dry air!
Climate controls vegetation
Precipitation
- uplifting and adiabatic cooling in tropics and temperate regions
- subsidence, adiabatic warming (drying) in desert and arctic
Vegetation
Soil
Precipitation at equator
Very wet along equator
Precipitation in temperate zone latitudes
Somewhat wet
Subsidence
The sinking, or downward movement, of air over a wide area within an area of high pressure
Relatively dry latitutdes
Poles and between equator/tropics and temperate latitudes
Coriolis effect
Air moving from high to low latitudes appears deflected (due to momentum)
- diverts winds (and currents) to right in the northern hemisphere and left in the southern hemisphere
Oceans transfer __% of the heat from the tropics to temperate and polar regions
40% –primarily through surface currents, and the “great conveyor belt”
Thermohaline circulation
- Very dense surface water in the North Atlantic Ocean sinks and new water moves northward to replenish it
- The warmer water moving into the Atlantic originates in the Indian and Pacific Oceans
- Cooler deep ocean water rises to the surface to replace that flowing to the Atlantic, completing the conveyor motion
Why does water primarily sink in the North Atlantic
It is more dense than surface waters elsewhere
Colder than most surface ocean waters, and saltier than North Pacific
Great conveyor belt not only ____ but also ____.
Not only distributes heat and therefore influences climates, but also helps mitigate global warming by taking CO2 out of the atmosphere
- the great conveyor belt is slowing, a feedback caused by global warming
Tipping point for the great ocean conveyor belt
Part of the Great Ocean Conveyor Belt, and is much more sensitive to global warming than thought in 2007, already slowing
- has not been this sluggish in 1,000 years
Why is the great conveyor belt slowing?
A) more winds across the North Atlantic are increasing
evaporation of the ocean water there
B) warmer ocean temperatures are increasing evaporation in the North Atlantic
C) melting of Greenland ice and Arctic Ocean ice contributing freshwater to the North Atlantic
D) “A” and “B”
E) “A” and “C”
C) melting of Greenland ice and Arctic Ocean ice contributing freshwater to the North Atlantic
Seasonal variation in “equatorial” low
Tropical rainy seasons vary spatially due to seasonal variation in “equatorial low”
- Tampico, Mexico: wet in June through October
- Vicosa, Brazil: Wet in October through March
Deviations from idealized climate patterns on land due to
- Oceans as a source of heat and moisture
- Topographical effects
Wetter on side of prevailing winds, more dry (rain shadows) on downwind side
- Moisture-laden westerlies, forced higher by a mountain range, rise, become cooler, and release the moisture as rain or snow
-> This leaves a drier rain shadow on the Eastern slopes
Topography
Temperature decreases with elevation (adiabatic cooling)
- global average lapse rate: 6.4ºC/1000m
Terrestrial biomes are structured by
Climatic patterns
Without the greenhouse effect the temperature of the earth in Celsius degrees would be…
-17ºC
Heated air at the equator: (Choose one or more answers)
- Rises and cools
- Rises and warms
- Moves towards the equator
- Moves away from the equator
Rises and cools
Moves away from the equator
What atmospheric effect is responsible for the desert conditions found in the southwestern United States?
A rain shadow
The change in seasons on Earth is due to:
- Changes to Earth’s distance from the sun during an annual rotation
- The Earths rotation
- Changes to the tilt of Earth’s axis relative to the sun during an annual rotation
- Changes in the Earth’s core temperature during year, which changes as a result of Earth’s distance from the sun
Changes to the tilt of Earth’s axis relative to the sun during an annual rotation
When light from the sun hits Earth _____________, the intensity is greater relative to _______________.
- At an oblique angle; light that hits at an acute angle
- At a 90 degree angle; light that hits at an oblique or acute angle
- At a vertical angle; light at the Equator
- At a 90 degree angle; light at the Equator
At a 90 degree angle; light that hits at an oblique or acute angle
If you were standing in the tropics, which direction would the prevailing winds blow?
From the east
Where did the researchers find an area on earth that was cooling rather than warming?
In the North Atlantic
True or False: The great ocean conveyor belt is speeding up due to melting of glaciers and changing patterns of precipitation.
False: it is slowing down due to melting glaciers in the North Atlantic
Shifts in conveyor belt ocean circulation could be the cause of the “cool spot”. According to the video what is likely causing this to occur?
Addition of freshwater into the oceans – Glaciers are melting adding more freshwater into the oceans
True of False: According to the video the effects of global warming are occurring later than predicted by most models.
False: it is sooner than expected
Which biome has the least amount of precipitation and warmest temperatures?
Desert
Which biome has the greatest amount of precipitation and warmest temperatures?
Tropical rain forest
Which term describes the number of species found in a particular area?
Species richness
What term describes the total amount of photosynthesis per area for a defined length of time?
Primary production
Terrestrial biomes
Large regions of the Earth characterized by readily recognizable patterns of life (usually vegetation)
- tropical rainforests
- deserts
- tundra
- temperate grasslands
- etc.
For a given biome, similar form and function in vegetation across the planet as a result of
Convergent evolution
- selective pressure of climate leading to similar evolutionary outcomes
- not necessarily any common taxonomic or genetic background
Convergent evolution
Evolution of similar growth forms among unrelated species
Whittaker diagram
Biomes fall out along gradients of precipitation and temperature
- the range of precipitation is far greater in warm than in cool regions
Tundra
Polar air masses year round, very short growing season
The current and predicted rate of increase in temperatures in polar regions is greater than elsewhere on Earth, so tundra biome is particularly threatened
Tundra characteristics
Climate
- cold and often dry
Vegetation
- moss, lichen, grasses, sedges
Soils
- frozen or wet
- PERMAFROST: soil frozen year-round
- slow decomposition: organic-rich
Boreal forest
Polar air in winter, some temperate air masses in summer
Boreal forest characteristics
Climate
- warmer summers than tundra
- more precipitation
Vegetation
- usually evergreen conifers
Soils
- often frozen or wet, organic-rich
Temperate forest characteristics
Evergreen conifers
- climate: summers often dry
Deciduous broadleaves
- climate: need summer rainfall
Temperate grasslands
Continental interiors and mountain rain shadows
The most modified by humans of any biome
- the rich soils make for great agriculture (at least for the first many hundred to a thousand years after conversion)
Temperate grasslands (prairie, steppe) characteristics
Climate
- cold winters, wet summers
Vegetation
- dominated by grasses
Soils
- nutrient-rich, fertile
Desert characteristics (remember subsiding air of Hadley cells and rain shadows)
Climate
- very dry
- occasional flash-flood
Vegetation: various drought adaptations
- CAM photosynthesis
- ephemerals
- often, very deep roots
Soil
- thin; little organic matter
- “islands of fertility” under shrubs
Savannah and tropical seasonal forest
Pronounced wet-dry seasons, as the Hadley cells move North and South over the year
- mostly grasses with some trees
- dry deciduous, with largely closed tree canopy
Savannah and tropical seasonal forest characteristics
Seasonal climate
- temp > 20ºC
- precipitation: STRONGLY SEASONAL, typically summer rains, monsoon
Vegetation
- mix of trees and grass
- as rainfall increases: desert -> savannah -> dry forest
Tropical rain forests
Equatorial, very little seasonality (Hadley cells)
Tropical rainforest characteristics
Climate
- solar input: nearly constant
- temp: warm (>20ºC)
- precipitation: lots (>2m/year), evenly distributed
Vegetation
- broad-leaved evergreens
Soils
- often highly leached, acidic, and nutrient-poor
Ithaca on Whittaker diagram
Top left of temperate forest, probs move down as climate warms
Biomes occur where they do because of
Climate
Climate has always changed, and biomes have responded and changed…but this takes time, and climate change in the past has been very gradual.
Human-caused global warming is occurring much more quickly than past climate change, and poses unprecedented challenges to the integrity of biomes.
The greatest biodiversity is found in
Tropical forests
- also highest average rate of photosynthesis per area followed by temperate then boreal forest
The lowest biodiversity is found in
Boreal forests
- makes them vulnerable to widespread disturbances such as insect outbreaks (ex. pine beetle outbreak in BC)
Terrestrial biomes are a very large part of the global carbon cycle
Amount of organic carbon stored in a system is not simply a function of rate of photosynthesis. Loss terms (decomposition, fire) are also important.
Carbon is stored both in living biomass (mostly vegetation, so trees, grasses, etc.) and as organic matter in soils.
Which is correct:
a) Tropical rain forest area is roughly the same as boreal forest area
b) Boreal forest area is 2X that of tropical rain forest area
c) Tropical rain forest area is 2X that of boreal forest area
Tropical rain forest area is 2X that of boreal forest area
- remember that Mercator-projection maps exaggerate areas further away from the equator
How much of the total biomass in terrestrial biomes occurs in tropical forests?
a) Less than 20%
b) 20-30 %
c) 30-50%
d) More than 50%
More than 50% – with regard to biomass, trees matter! Followed by temperate forest and boreal forest.
- soil is the largest repository of organic matter on land, storing more carbon than all vegetation
Importance of fire as a disturbance in some types of biomes
Periodic, large-scale fires in Boreal forests
ex. Krueger National Park, South Africa: Tropical savannah
-> regular fires help maintain the vegetation structure
Experimental suppression of fire for 35 years resulted in more trees
True or false: Fires are more important in structuring hot
deserts than grasslands and savannahs
False: not much to burn in the desert where as fire shapes the landscape in grasslands and savannahs (ex. Krueger National Park fire suppression experiment for 35 years)
Fire is an important form of disturbance in
tundra systems:
A) yes, but with burns only every 100 years or so
B) no, the tundra is too wet for fires
C) no, the tundra is too cold for fires
D) not historically, but with global climate change, fires are becoming more common in the tundra
D) not historically, but with global climate change, fires are becoming more common in the tundra
- The Alaskan tundra burns (Anaktuvuk River Fire of 2007)
-> warmer summers in recent decade or two
-> more evapo-transpiration, dryer soils, more easily burned
-> plus thunderstorms (lightning!)
Could we expect similar characteristics to evolve in species that are found in regions of the world where environmental conditions are similar?
Yes –convergent evolution
Ithaca, NY is located in which biome?
Temperate forest
Rank the following from high to low relative biodiversity (1= high, 4 = low)
- boreal forest
- tropical forest
- temperate grasslands
- tundra
- tropical forest
- temperate grasslands
- tundra
- boreal forest
Rank the biomes according to the relative amount of biomass (carbon) that they store (1= the most, 5 = the least)
- boreal forest
- tropical savannah
- tropical forest
- temperate forest
- temperate grassland
- tropical forest
- temperate forest
- boreal forest
- tropical savannah
- temperate grassland
Globally, why does Tundra have little relative biomass but high relative soil biomass?
- Tundra has more land cover than most biomes, so due to more area it stores more carbon in the soil
- The premise of the question is false. Tundra has large amounts of biomass, and low amounts of soil biomass because of the permafrost
- The harsh climate means very little grows, but permafrost and cold temperatures stops organic matter from decomposing in the soil, so the carbon is stored there
- Weather patterns cause by the strong Coriolis effect sweep above ground biomass off of the tundra, leaving behind the large proportion of soil biomass
The harsh climate means very little grows, but permafrost and cold temperatures stops organic matter from decomposing in the soil, so the carbon is stored there
Of the following biomes, in which 3 did fire historically play a regular and important role?
- temperate forest
- temperate grasslands
- tropical savannah
- tropical forests
- deserts
- tundra
Temperate forest
Temperate grasslands
Tropical savannah
