10 - Climate change (part 1) Flashcards
What is climate change? E.g.
Long-term variations of the average weather conditions experienced in a particular region
e.g. Edmonton has milder winters than 30 years ago
What is global warming? E.g.
Increase over time in the average temperature across the entire planet
e.g. The planet as a whole is on average 1C warmer than it was in 1880
The IPCC definition of climate change makes a distinction between…
climate attributable to human activities altering the atmospheric composition and climate variability attributable to natural causes
“in addition to natural climate variability”
Six main drivers of climate change
- Aerosols
- Natural fluctuations in solar output
- Clouds
- Ozone
- Greenhouse gases and large aerosols
- Surface albedo changes
Slide 7
Examples of processes that warm the atmosphere? Cool it?
Warm:
- CO2 emissions from land clearing, fires
- warming from decreased ice and snow cover
- greenhouse gases
- heat and CO2 emissions from the ocean
Cool:
- CO2 removal by plants and soil orgs
- aerosols
- cooling from increase in snow and ice
- heat and CO2 removal by ocean
Factors that altered climate over the past ~3.5 billion years? How has climate fluctuated over the past 800-900k years?
Factors: large-scale volcanic eruptions, impacts by meteors and asteroids, changes in solar input
Fluctuations through glacial and interglacial periods
When was the last interglacial period? How long as temperature been stable?
Started 10k years ago (ongoing)
Temp fairly stable for past 1k years, but rising since 1975 (GHGs)
Slides 11, 12
Temperature changes/variation
How does the amount of solar output vary? Why? The amount of sun the earth receives is termed…
The amount of solar radiation we receive from the sun varies on daily, yearly, decadal, centennial and millennial basis
Changes in Total Solar Irradiance (TSI) are caused mostly by changes in activity of sunspots and faculae (more sunspots = increased TSI)
What are sunspots? Faculae?
Sunspots = dark spots on the surface of the sun in which magnetic forces are very strong and block the hot solar plasma; they are cooler and darker than their surroundings
Faculae = bright spots on the surface of the sun, that put out more radiation than normal; their numbers increase and decrease alongside sunspots
More sunspots = more faculae = increased TSI
Variation of total solar irradiance over time?
Peaks roughly every 11 years
Cyclic
Little change, not the main cause of climate change
Slide 16
When was the “Little Ice Age”? What was it
16th to mid 19th century
Europe: longer winters, famine from crop failure, sea ice isolated Iceland and Greenland
North America: longer winters, food shortages recorded by Indigenous communities
What is eccentricity? Two extremes? How does it affect solar radiation?
Our orbit around the sun is eccentric (changes over time)
Perihelion = closest to sun
Aphelion = farthest from sun
3% difference between them (5 million km)
This difference equates to a 6% difference in the solar radiation reaching the Earth in perihelion vs aphelion
How does the shape of the Earth’s orbit change?
Cycles between circular and elliptical about every 100,000 years
0 = circular
0.07 = slightly elliptical
What is the Earth’s obliquity? How does it change? Current? What effect does obliquity have on climate?
Tilt of the earth
Cycles every 40,000 years between 24.5 degrees to 22.1 degrees (currently we are at 23.5% and decreasing)
High angle = more extreme seasons
Low angle = less extreme seasons (ice sheets)
What is the Earth’s precession? It can alter…
Changes in the orientation of the Earth’s axis (cycle spans ~25,000 years)
Can alter
- the position of the Earth with respect to perihelion and aphelion
- which hemisphere is facing the sun at each point
Slide 21
Three types of variation in the Earth’s orbit
Eccentricity
Obliquity
Precession
Variations in the Earth’s orbit and glacial/interglacial periods? E.g.
Milankovitch cycles: regular cycling of the eccentricity, obliquity and precession of Earth’s orbit drives glacial and interglacial periods
e.g. Pleistocene glaciation
Volcanic eruptions produce… Which can cause what?
Sulfuric gas (sulfate aerosols)
Volcanic ash (small particles of rock and glass)
These compounds can cause cooling
Example of a Volcanic event and its effects on climate
Mt Pinatubo, Philippines
Sulfate aerosols and other compounds in the plume scattered incoming solar radiation, cooling the Earth by 0.5C for two years
How might volcanoes cause warming??
Through water vapor and carbon dioxide: both are GHGs and can aid in heat retention
Produce 0.11 Gt CO2 annually, while humans produce 40 Gt CO2 annually
How can meteorite events affect climate?
- similarly to volcanoes, they create dust upon impact
- this dust can sometimes block solar radiation for months at a time
- they also create a shock wave that can disrupt ecosystem structure
Example of a meteorite event? How did they identify it? What geological boundary is it?
Chicxulub crater
About 65-66 Ma, something hit the Yucatan Peninsula, Mexico
High concentrations of iridium in a layer of sandstone aged 65-66 Ma
Cretaceous-Paleogene boundary and mass extinction event
Slide 29
What is the greenhouse effect?
Some solar radiation is reflected by the Earth and the atmosphere
Most radiation is absorbed by the Earth’s surface and warms it
Some of the infrared radiation passes through the atmosphere. Some is absorbed and re-emitted in all directions by greenhouse gas molecules. The effect of this is to warm the Earth’s surface and the lower atmosphere.
Slide 38
Main components of our air
Nitrogen 78%
Carbon dioxide 0.41% (small changes have large effects)
Oxygen 21%
Water vapor varies: 0% to 5%
What is Global Warming Potential of GHGs? Values?
Potential to warm atmosphere compared to CO2
CO2 = 1
Water vapor = 0
Methane = 28 CO2
Nitrous oxide = 273 CO2
Ozone = 1,000 CO2
Chlorofluorocarbons = 10,2000 CO2
Slides 40, 41, 42
What is the Keeling Curve? Latest reading?
Measures atmospheric CO2 concentrations
Latest = 418. 64 ppm
Slides 43, 44
Slides 45-47
Look
What is a carbon footprint? What countries have the largest? Largest per capita?
Amount of CO2 generated by an individual, organization, country or other entity over a given period
China has the largest national carbon footprint, followed by the US
The US, followed by South Korea, have the largest per capita footprints
Slides 49-54
Look (graphs)
Slides 56, 57
Look
How has climate change affected agricultural yields
Temperate regions are more affects
Crops grown in temperate regions (corn, wheat) more affected
What are feedback loops? Two types?
Self-reinforcing processes that can either amplify or dampen the effects of climate change. They can have significant and sometimes unpredictable effects on global temperatures and environmental conditions.
Positive (amplifying) and negative (dampening)
Examples of positive and negative feedback loops
Positive:
- reduced albedo
- carbon cycle
- more water vapor in the atmosphere
- melting of permafrost
- deforestation
Negative:
- increased albedo (melting of ice/snow)
- clouds
- biological uptake of CO2
- ocean heat uptake
- ocean C sequestration
