Lecture 17 - Introduction to Weather and Climate

Question 1

What does weather refer to?

Answer 1

Weather refers to meteorological conditions (e.g. temperature, wind, precipitation), at a given location and time. It is short term and localized.

Question 2

Why does weather change over short time scales?

Answer 2

Due to changing meteorological conditions (moving air masses), daily heating/cooling, natural seasonal variations, as well as long-term changes in climate.

Question 3

What does climate refer to?

Answer 3

Climate refers to meteorological conditions that prevail in a region. It is long term and regional. Climate can be thought of as “the statistics of weather”, or the regional weather averaged over time (e.g. >30 years).

Question 4

How much of the solar radiation with short wavelengths (visible light) that heats land and ocean is absorbed?

Answer 4

∼50%

Question 5

What do heated objects radiate?

Answer 5

They radiate energy at long wavelengths (infrared radiation).

Question 6

What is the role of greenhouse gases in the atmosphere?

Answer 6

They absorb outgoing infrared radiation as heat, preventing loss to space.

Question 7

What temperature do greenhouse gases keep earth at?

Answer 7

This feedback system keeps the Earth at an average temperature of +15℃ (rather than -18℃).

Question 8

What is the impact of tectonic placement of continents at or near either pole?

Answer 8

increases snow accumulation and the prospect for glacier formation

Question 9

Why does the Great Ocean Conveyor Belt exist?

Answer 9

North-South alignment of continents allows for ocean circulation bringing warmer water and increased precipitation to higher latitudes.

Question 10

What do Milankovitch cycles describe?

Answer 10

Milankovitch cycles describes variations in the Earths astronomical movements that influences the climate on a time scale of 1000–100,000 years.

Question 11

What are the three main variations making up the Milankovitch cycles?

Answer 11

eccentricity
tilt (obliquity)
precession

Question 12

What is eccentricity?

Answer 12

Changes in the Earths orbit between nearly circular and slightly more elliptical.

Question 13

What are the different cycle lengths of eccentricity? What do they average to?

Answer 13

Different cycles of 95,000, 125,000 and 400,000 years, averaging to ∼100,000 years.

Question 14

What does the eccentricity of Earth coincide with?

Answer 14

The eccentricity coincides with broad glacial cycles over the past million years.

Question 15

What is the cycle of eccentricity at today?

Answer 15

Its minimum

Question 16

What is tilt (obliquity)?

Answer 16

changes in the Earths axial tilt

Question 17

What is the cycle for the change of Earths axial tilt?

Answer 17

between 21.5° and 24.5° in a cycle of ∼41,000 years

Question 18

What does greater tilt mean for Earth?

Answer 18

greater seasonal extremes

Question 19

What does precession describe?

Answer 19

changes in the Earths wobble around its tilt axis

Question 20

What does precession correspond to?

Answer 20

lesser or greater seasonal contrasts

Question 21

What is the timespan of precession?

Answer 21

19–23,000 years

Question 22

What can the Milankovitch cycles explain?

Answer 22

large-scale warming or cooling trends on geological time-scales

Question 23

Why does Earth’s climate change?

Answer 23

• variations in the distribution and shape of continents and ocean basins
• variation in solar irradiance
• changes in atmospheric greenhouse gas concentrations

Question 24

Why do variations in the distribution and shape of continents and ocean basins occur?

Answer 24

due to plate tectonics, acting over time scales of millions of years

Question 25

What is solar irradiance?

Answer 25

the amount of solar energy received per unit area of Earth’s surface

Question 26

Why does variation in solar irradiance occur?

Answer 26

mostly due to Milankovitch cycles over time scales of tens to hundreds of thousands of years

Question 27

What do changes in atmospheric greenhouse gas concentrations reflect?

Answer 27

a variety of geological, geochemical and biological processes also acting over long time scales

Question 28

What are the main greenhouse gases?

Answer 28

CO₂, CH₄, N₂O, O₃, CFCs

Question 29

How are humans releasing CO₂ into the atmosphere?

Answer 29

from burning of fossil fuels and forests

Question 30

How are humans releasing CH₄ into the atmosphere?

Answer 30

from decomposition of vegetation in absence of O₂

Question 31

How are humans releasing N₂O into the atmosphere?

Answer 31

from chemical fertilisers and automotive combustion

Question 32

How are humans releasing O₃ into the atmosphere?

Answer 32

from automotive and industrial gases

Question 33

How are humans releasing CFCs into the atmosphere?

Answer 33

from coolants and solvents

Question 34

How much higher are CO₂ concentrations today compared to before the industrial revolution?

Answer 34

∼50% higher (the highest they have been for perhaps∼20 million years)

Question 35

How much has earth’s global average temperature increased by?

Answer 35

about ∼0.7°

Question 36

What do models predict about Earth’s temperature in the next century?

Answer 36

Its warm an additional 2–6℃ in the next century.

Question 37

Historically, how long has it taken the planet to warm 1℃?

Answer 37

∼1,000 years

Question 38

How much faster is the projected rate of warming than ‘natural’?

Answer 38

at least 20 times faster

Question 39

Are rising temperatures distributed evenly across the globe?

Answer 39

no - polar regions absorbing far more of the excess heat than low latitude areas

Question 40

Why has there been rapid melting of the Greenland and Antarctic ice sheets and of mountain glaciers and ice caps worldwide?

Answer 40

Polar regions absorb far more of the excess heat than low latitude areas.

Question 41

Where is 90% of the energy from anthropogenic global warming stored?

Answer 41

in the oceans - leading to thermal expansion of seawater

Question 42

What is causing sea levels to rise?

Answer 42

the melting of continental ice and the thermal expansion of seawater

Question 43

How much has global mean sea-level has risen since 1900 CE?

Answer 43

∼25 cm

Question 44

How much are global mean sea-levels rising by?

Answer 44

3.5 mm/yr

Question 45

What do most climate models forecast about future sea-level rise?

Answer 45

a further 0.3–1.2 m rise by the end of this century

Question 46

How many people living in low-lying coastal areas would be directly impacted by a rise of 0.3–1.2 m?

Answer 46

an estimated 1–2 billion people

Question 47

What is driving upward trends in weather-related hazards?

Answer 47

rising temperatures

rising sea-levels

Question 48

What is responsible for the recent rise in the number, size and intensity of North Atlantic hurricanes?

Answer 48

Increasing ocean heat content provides more energy for tropical storms and cyclones.

Question 49

What increases the reach of storm surges?

Answer 49

higher sea-levels

Question 50

Why are wildfires increasing in number, size, and duration (specifically in North America)?

Answer 50

higher temperatures
increase in forest fuels (due to forest management)
beetle kill (due to warmer temperatures)

Question 51

What is the uneven nature of climate change likely to lead to?

Answer 51

a higher frequency of extreme weather events, increasing the severity of droughts and floods

Question 52

What is atmospheric CO₂ naturally modulated by?

Answer 52

weathering of silicate rocks
volcanism
biology (eg. marine organisms that secrete CaCO₃ shells)
burial and subduction of carbon-rich sediments

Question 53

What do CO₂ concentrations measured from air bubbles trapped in ice cores show?

Answer 53

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

Question 54

What are some of the effects of climate change in the North of Canada?

Answer 54

The Northwestern passage was opened for commercial maritime passage.
Potential for more Arctic natural resource development.
Melting permafrost weakens and undermines infrastructure.
Wildlife adapted to cold climates shift northward by 150km for every degree of warming.

Question 55

What are some of the effects of climate change in Atlantic Canada?

Answer 55

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 56

What are some of the effects of climate change in Ontario and Quebec?

Answer 56

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 risk 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 57

What are some of the effects of climate change in the Prairie Provinces of Canada?

Answer 57

Longer growing season, longer frost-free period.
Reduced soil moisture and irrigation waters.
Shrinking wetlands.
Increase in drought frequency & severity.
Crops more at risk to pests and disease.

Question 58

What are some of the effects of climate change in British Columbia?

Answer 58

Pacific waters too warm for sockeye salmon.
Increased likelihood of more wildfires and a longer fire season.
Increased winter precipitation raises the risk for spring snowmelt flooding.
Higher winter precipitation also increases the risk for landslides and avalanches in mountainous regions.