Lecture 17 - Introduction to Weather and Climate Flashcards
What does weather refer to?
Weather refers to meteorological conditions (e.g. temperature, wind, precipitation), at a given location and time. It is short term and localized.
Why does weather change over short time scales?
Due to changing meteorological conditions (moving air masses), daily heating/cooling, natural seasonal variations, as well as long-term changes in climate.
What does climate refer to?
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).
How much of the solar radiation with short wavelengths (visible light) that heats land and ocean is absorbed?
∼50%
What do heated objects radiate?
They radiate energy at long wavelengths (infrared radiation).
What is the role of greenhouse gases in the atmosphere?
They absorb outgoing infrared radiation as heat, preventing loss to space.
What temperature do greenhouse gases keep earth at?
This feedback system keeps the Earth at an average temperature of +15℃ (rather than -18℃).
What is the impact of tectonic placement of continents at or near either pole?
increases snow accumulation and the prospect for glacier formation
Why does the Great Ocean Conveyor Belt exist?
North-South alignment of continents allows for ocean circulation bringing warmer water and increased precipitation to higher latitudes.
What do Milankovitch cycles describe?
Milankovitch cycles describes variations in the Earths astronomical movements that influences the climate on a time scale of 1000–100,000 years.
What are the three main variations making up the Milankovitch cycles?
eccentricity
tilt (obliquity)
precession
What is eccentricity?
Changes in the Earths orbit between nearly circular and slightly more elliptical.
What are the different cycle lengths of eccentricity? What do they average to?
Different cycles of 95,000, 125,000 and 400,000 years, averaging to ∼100,000 years.
What does the eccentricity of Earth coincide with?
The eccentricity coincides with broad glacial cycles over the past million years.
What is the cycle of eccentricity at today?
Its minimum
What is tilt (obliquity)?
changes in the Earths axial tilt
What is the cycle for the change of Earths axial tilt?
between 21.5° and 24.5° in a cycle of ∼41,000 years
What does greater tilt mean for Earth?
greater seasonal extremes
What does precession describe?
changes in the Earths wobble around its tilt axis
What does precession correspond to?
lesser or greater seasonal contrasts
What is the timespan of precession?
19–23,000 years
What can the Milankovitch cycles explain?
large-scale warming or cooling trends on geological time-scales
Why does Earth’s climate change?
- variations in the distribution and shape of continents and ocean basins
- variation in solar irradiance
- changes in atmospheric greenhouse gas concentrations
Why do variations in the distribution and shape of continents and ocean basins occur?
due to plate tectonics, acting over time scales of millions of years
What is solar irradiance?
the amount of solar energy received per unit area of Earth’s surface
Why does variation in solar irradiance occur?
mostly due to Milankovitch cycles over time scales of tens to hundreds of thousands of years
What do changes in atmospheric greenhouse gas concentrations reflect?
a variety of geological, geochemical and biological processes also acting over long time scales
What are the main greenhouse gases?
CO₂, CH₄, N₂O, O₃, CFCs
How are humans releasing CO₂ into the atmosphere?
from burning of fossil fuels and forests
How are humans releasing CH₄ into the atmosphere?
from decomposition of vegetation in absence of O₂
How are humans releasing N₂O into the atmosphere?
from chemical fertilisers and automotive combustion
How are humans releasing O₃ into the atmosphere?
from automotive and industrial gases
How are humans releasing CFCs into the atmosphere?
from coolants and solvents
How much higher are CO₂ concentrations today compared to before the industrial revolution?
∼50% higher (the highest they have been for perhaps∼20 million years)
How much has earth’s global average temperature increased by?
about ∼0.7°
What do models predict about Earth’s temperature in the next century?
Its warm an additional 2–6℃ in the next century.
Historically, how long has it taken the planet to warm 1℃?
∼1,000 years
How much faster is the projected rate of warming than ‘natural’?
at least 20 times faster
Are rising temperatures distributed evenly across the globe?
no - polar regions absorbing far more of the excess heat than low latitude areas
Why has there been rapid melting of the Greenland and Antarctic ice sheets and of mountain glaciers and ice caps worldwide?
Polar regions absorb far more of the excess heat than low latitude areas.
Where is 90% of the energy from anthropogenic global warming stored?
in the oceans - leading to thermal expansion of seawater
What is causing sea levels to rise?
the melting of continental ice and the thermal expansion of seawater
How much has global mean sea-level has risen since 1900 CE?
∼25 cm
How much are global mean sea-levels rising by?
3.5 mm/yr
What do most climate models forecast about future sea-level rise?
a further 0.3–1.2 m rise by the end of this century
How many people living in low-lying coastal areas would be directly impacted by a rise of 0.3–1.2 m?
an estimated 1–2 billion people
What is driving upward trends in weather-related hazards?
rising temperatures
rising sea-levels
What is responsible for the recent rise in the number, size and intensity of North Atlantic hurricanes?
Increasing ocean heat content provides more energy for tropical storms and cyclones.
What increases the reach of storm surges?
higher sea-levels
Why are wildfires increasing in number, size, and duration (specifically in North America)?
higher temperatures
increase in forest fuels (due to forest management)
beetle kill (due to warmer temperatures)
What is the uneven nature of climate change likely to lead to?
a higher frequency of extreme weather events, increasing the severity of droughts and floods
What is atmospheric CO₂ naturally modulated by?
weathering of silicate rocks
volcanism
biology (eg. marine organisms that secrete CaCO₃ shells)
burial and subduction of carbon-rich sediments
What do CO₂ concentrations measured from air bubbles trapped in ice cores show?
variations from 180-300 ppm over the past 400,000 years
What are some of the effects of climate change in the North of Canada?
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.
What are some of the effects of climate change in 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.
What are some of the effects of climate change in 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 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.
What are some of the effects of climate change in the Prairie Provinces of Canada?
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.
What are some of the effects of climate change in British Columbia?
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.
