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
