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99 Cards in this Set
- Front
- Back
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Sources of Evidence for Anthropogenic Climate Change (Indirect)
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Paleoclimate Proxies
- dendochronology - ice and sediment cores - Stable isotope dating - sea level reconstruction |
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Sources of Evidence for Anthropogenic Climate Change (Direct)
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- Temperature measurements
- sea ice loss - Atmospheric tracer measurements |
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What is the "Hockey Stick" Graph? What does this imply?
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Graph of global temperature/ cO2 concentrations. Implies that there has been a discernable impact on the climate's temperature over the last recent history.
- warming is recent and quicklenly worsening |
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What is Residence Time (Tr)?
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Mass/flux
How long a substance stays in an area Short res. times are highly variable (think aerosols) - important for biosphere-atmosphere interaction Long res times do not vary much (think nitrogen) |
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What is the mean Tr of Carbon?
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5 years
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Flux
Flux density |
amount of material transferred from one reservoir to another per unit time
flux/ unit area |
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Source
Sink |
any process that releases material into the atmosphere
any process that removes material from the atmosphere |
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Reservoir
Stock Budget |
of material defined by certain physical, chemical, or biological characteristics
Mass of material in a reservoir Balance of all sinks/ sources in a reservoir |
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1. Methane is ____ x more powerful of a warmer
2. N2O is ____ x more powerful of a warmer than cO2 |
1. Methane is 25x more powerful of a warmer
2. N2O is 300x more powerful of a warmer than CO2 |
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Bretherton Diagram
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diagram of all forcings and feedbacks of climate
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What is the mean strength of incoming solar radiation?
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1366 W/m2
- varies by +/- 0.5 W/m2 on a cycle of about 11 y |
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What is the energy balance equation?
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Q*= Ki (1-a)-σ T^4 + Ko
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What are aerosols?
- How are they introduced into the atmosphere? - What effects can aerosols have on the atm? |
Suspensions of liquid droplets or solid particles in the air
Enter atm through: - Direct injection: injected into air by a source - Chemical rxns: transformation of atm. gases into aerosols (i.e, sulphur into sulphates) Effects: - aerosols can have a cooling effect on the atm when introduced in large amounts |
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What is insolation?
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measure of solar radiation on a given surface + recorded during a given time
- affected by latitude + orbital variation |
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T/F: Water vapour is less potent of a warmer than CO2
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False! It is 2-3x more potent of a GHG than CO2
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What is water vapour feedback?
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When CO2 increases in the atm, global temperature rises and the air can hold more water
Since H2O is 2-3x more potent of a warmer, warming increases and increases POSITIVE feedback |
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Evapotranspiration (ET)
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-returns 60% of land precipitation to atm
- Plant ET is closely related to CO2 uptake - Changes in ET can affect sensible heat flux (air temperature) - Soil moisture is important |
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Albedo
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- Affects radiation balance by controlling amount of outgoing radiation
- Altered by snow cover, vegetation type and health, soil moisture, aerosols, cloud cover - Soil moisture has a threefold impact on albedo High albedo: white coloured/ reflective Low albedo: dark surface, sink for heat |
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T/F: Climate warming will reduce the efficiency of CO2 removal
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True!
-Increased warming in ocean reduces export of carbon from surface of water to deep ocean (limits air-sea exchange) - Increased rate of soil carbon decomposition - Probably others |
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Physical Climate Feedbacks
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- Water vapour feedback (+)
- Ice albedo feedback (+) - Cloud feedback (*Complex, can either be + or - depending on type of cloud + height) - Lapse rate (vertical temperature profile takes longer to warm, negative feedback) |
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Climate sensitivity
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measurement of the responsiveness of a climate system to external forcing
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Why is methane a big problem?
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- It has a warming power 25x more powerful than CO2
- Positive feedback loop with warming: methane emissions will increase with warming due to melting permafrost |
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the Gross-Net Issue
- Net-Net accounting - Gross-Net accounting - Gross-Gross accounting |
N-N
- All emissions and sinks associated with fossil fuels, industrial activity + land use are taken into account G-G - LUCF excluded, removed incentives to improve land management, ignores important component of carbon cycle G-N - Ignored LUCF from baseline accounting (1990 emissions), but allows some LUCF emissions and sinks Gross-net' = total carbon flux in the commitment period. 'Net-net' = carbon flux in the commitment period minus carbon flux in the base year. |
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What is the CO2-equivalent?
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CO2-e: The concentration of CO2 that would cause the same level of radiative forcing as a given type and concentration of GHG
CO2-e= CO2 + 24(CH4)+ 300(N20) |
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How much carbon is in these ecosystems?
- Forest - Grassland - Cropland - Wetland |
Forest: 45% of terrestrial carbon (50% boreal, 37% tropical)
Grassland: 26% Cropland: 8-10% Wetland: 10-30% |
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What is the problem with Nitrous Oxide (N2O)?
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300x more powerful of a warmer than CO2
- Positive feedback - Emissions from soil increase with temperature, soil moisture, CO2 |
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Is it true that large fires can be both a negative and positive feedback?
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Yes!
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Forcing
Feedback |
Forcing: perturbations in climate
Feedback: the change produced by the forcing |
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Why is the term (1-α) so important in the radiation balance equation?
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Back-scattering reduces solar radiation absorbed in earth-atmosphere system
- Albedo mostly affects this (amount of radiation reflected from surface) |
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Infrared (IR) Radiation
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- All natural surfaces emit radiation (usually in the form of heat)
- If there is a change in the characteristic of the surface, the emission of radiation will change - this is dependent on temperature and σ (Stefan-Boltzman constant) |
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Radiative Forcing
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The difference between radiation received on Earth's surface and that reflected back into space
-positive forcing warms the system (more radiation absorbed than reflected) - negative forcing cools the system (more radiation leaving than staying absorbed) |
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What can affect radiative forcing?
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Anything that can act as an external agent to the absorption or reflection of radiation
- changes in GHG conc - Change in ice/cloud albedo - Variations in amt of solar radiation reaching Earth (orbital) |
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What are the steps of radiative forcing?
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1. Climate is in equilibrium
2. Forcing happens 3. Response to forcing 4. Equilibrium is temporarily upset 5. Discrepancy between incoming + outgoing radiation exists 6. Feedback loops alter climate by raising or lowering temperature to bring it back into EQ |
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What is LIA?
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Leaf area index
- area of leaves/area of ground Important to know because we can extrapolate NPP from this which is good to know to calculate carbon sequestration values |
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What is NPP?
ANPP BNPP |
Net Primary Productivity
-Annual accumulation of organic matter/unit of land (g/m2/y) - links photosynthesis to geochemical cycling (biogeochemical) - NPP varies with vegetation type + age ANPP: Above ground Net primary productivity - growth of leaves + branches BNPP: Below ground NPP - growth + overturn of roots - hard to measure, generally expressed as a ratio of ANPP/BNPP |
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From a carbon counting perspective: is old growth forest valuable?
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Not really; the NPP of old growth forest compared to younger forest is very low
- trees will reach a limit (asymptote) where is can no longer store more carbon - they are no longer sequestering carbon at useful rates - from a carbon accounting perspective it would be optimal to cut down stands of a certain age + then reforest them |
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Net global total productivity
Total NPP What is the Tr of carbon in the atm? |
60.2 pG/C a year is being removed
560 x 10^15 g C (560 pG/C) Tr= mass/flux = 560/60.2 pG/C = ~9, therefore CO2 resides in the atm for about 9 years before it is fully recycled |
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Environmental controls on NPP
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Photosynthesis
- stomatal aperture, conductance (rate at which water moves through stomata) - water, nutrient availability Water Use Efficiency - Loss of water relative to psynth - how much demand does the atm have for water? **WUE increases with increased CO2 Light Use Efficiency - Availability of PAR Nitrogen Use Efficiency |
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What is PAR?
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Photosynthetically active radiation
- the kind of light that plants can use to make plants |
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What happens to GPP when CO2 is doubled?
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30-40% increase in productivity
- only been tested in lab settings, hard to test in real life (try to test using the crop circle fences that inject CO2--FACE) |
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Paleoclimate Proxies
Direct Climate Observation |
- tree rings
- ice cores - sediment samples - global mean temperature - global average sea level - N. Hemi snow cover |
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Decay pools
1yr decay pool 10yr decay pool 100yr decay pool 1000 yr |
1: paper products
10: medium term products 100: furniture, housing 1000: not much |
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Concentration-carbon-cycle feedback
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negative feedback
warming causes fertilization effect in plants - causes them to increase psynth + take up more CO2 |
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Climate-carbon cycle feedback
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positive feedback
warming will cause a reduction in CO2 removal from land + ocean systems |
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Distribution of organisms along environmental gradients
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- Each species has a distribution on an ecosystem according to it's limits
- Species with a more narrow distribution will be easily and heavily affected by ecosystem change - Species with a higher tolerance (wider distribution) will be able to adapt more easily |
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Bioclimatic variables for environmental gradients
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- Growing degree days (annual sum of daily temperatures over 0)
- Moisture index (annual precip/ annual ET) - mean temp of coldest month |
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fAPAR
- why is it important? |
fraction of Absorbed Photosynthetically Active Radiation
- basically shows how much PAR has been absorbed, which we can use to extrapolate greeness - good tool to link ecosystems to climate fAPAR is greatest in ecosystems with high rainfall |
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Management practices that could reduce/ reverse current emissions of carbon from land
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- Halt deforestation
- Expand forest area - Increase C stocks in existing forests - More efficient forest harvest - Use more wood products - Substitute wood fuels for fossil fuels (carbon neutral) - Use forests to sequester carbon |
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What is the greenhouse effect?
What is it controlled by? |
The greenhouse effect is the warming that the atmosphere experiences due to the backscattering of IR radiation from Earth
GHE is controlled by cloud albedo, surface temperature, and H2O and GHG concentration |
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How many years does it take for a sunspot to grow/ shrink? (how long is the cycle)
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~ 11y
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Which biome holds the most carbon?
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Deciduous forest (15000 g C/m2)
- NPP = 600 G/C/m2/y |
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Why do peatlands have so much organic matter in them?
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Peatlands occur in areas where there is more precipitation than evapotranspiration.
- soil is waterlogged + anoxic - anoxic conditions are not the best for decomposition, so years and years and layers of organic matter accumulates up in the soil - eventually turns to coal |
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Flux Footprint
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Provide measurements + integrate over a large area
Footprint varies with: - Wind speed/ direction - Turbulence/ mixing - Height above surface |
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Inventory based methods for C accounting
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Estimate mass over a unit area
Involves destructive sampling + allometry for measurements - look at the chest height diameter - Weigh tree, find how much C - Use algorithm to find C content of any tree (need diameter at chest height) |
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T/F: Deciduous forests can sequester 25% more carbon than coniferous
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True!
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Is the growing season in N latitudes increasing? By how much?
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Is growing by 1.2-3.6 days
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What are some changes seen in the N. Hem due to climate change?
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- Increase growing season (1.2-3.6 days)
- Increase in summer photosynthetic activity - Increase stomatal density of woodland plants - Change in community composition - Biosphere becoming more active - Poleward shift of treeline - |
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What is the threshold of an ecosystem?
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The point at which there is an abrupt change in ecosystem quality, property or phenomenon, or when small changes in forcing can create big responses
Ecological thresholds occur when external factors, positive feedbacks, or nonlinear instabilities of a system cause irreversible changes to occur |
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What is a disturbance for an ecosystem?
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Any relatively discrete event in time that disrupts ecosystem community or population structure, and changes resources, substrate availability and general ecosystem characteristics
Damage, displacement or mortality of one or more individuals caused by physical agents or incidentally biotic agents |
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Give an example of:
- Exogenous disturbance - Endogenous disturbance - Direct disturbance - Indirect disturbance - Abiotic disturbance - Biotic |
Exo: Comes from outside of the ecosystem (i.e, a hurricane)
Endo: Comes from within the ecosystem (i.e, a shift in food chain) Direct: Kills individuals Indirect: Does not kill individuals but alters resource levels influencing them Abiotic: Not living (i.e, pollution) Biotic: Living (i.e, bugs, viruses) |
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Roughness Length
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A measure of the roughness of a surface
- Afforestation increases roughness while afforestation reduces it - Height at which theoretical wind speed = 0 Increase in roughness promotes rainfall |
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Factors that can lead to wildfire
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- Fuel (Loading, moisture, structure)
- Ignition (human/ lightning) - Weather (temp, moisture) - Human impact (land use, fragmentation, fire supressing) - |
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Codes for forest fires (3)
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- FFMC (fine fuels)
- DMC (7 cm below surface, OM) - DC (farther down into OM + soil) - |
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How does flame tilt determine how much soil is ignited in a forest fire?
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- Smaller the angle, the closer the fire will be to the ground
- Slow moving fire |
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How can wildfires cause regime shifts in wetlands?
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If the wetland is just burned, native species will be able to recolonize
If it is drained and burned, peat will burn much deeper (no buffers) and will likely not be recolonized by native species - this can become a problem when invasive species are able to take over |
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Temperatures above ____ for several days will kill the Mountain Pine Beetle
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-35 to -40
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What is the net affect of the Mountain Pine Beetle on radiative forcing?
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MPB stops psynth (reducing albedo)
- Dead trees + leaves now decomposing + releasing C instead of sequestering - Predicted to **** **** up across the country due to increased warming + fragmentation |
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How does the Mountain Pine Beetle affect snow cover (albedo)?
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Kills trees = fewer pine needles for interception
= increase albedo, increase insolation to ground, increase snow cover on ground - Rise in albedo = negative feedback |
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Why are the insect infestations of forests getting worse?
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Increase in temperature reduces health of forests, bird populations
- trees, birds move north - More trees/ less predators for BURGS |
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How can we identify ecosystem disturbances in tree rings?
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Looking at tree rings + comparing growth between them
- much smaller rings when disturbed by MPB, water scarcity, temperature, ect |
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What are the effects of reduced canopy cover?
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- Reduced herbaceous cover
- increase in soil temp - increase in evaporation - Increase in erosion |
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What are thermokarst wetlands? What happens?
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Thermokarst wetlands = permafrosty wetlands that are actively thawing.
- When they thaw, the large chunks of ice that used to be in the soil melt and causes the overlying soil + veg to collapse ("drunken trees") - This creates pockets of wetlands in between permafrost ecosystems |
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Is microbial decomposition a positive feedback? What affects it? Why?
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Positive feedback, increased warming = increased micro decomp, increased decomp= more net source of CO2/ CH4, which increases warming farther and so on
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Vegetation response to warming (what is the shift in tundra ecosystems as they warm?)
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1. Tundra
2. Low shrub 3. Shrub 4. Woodland/ treeline 5. Forest |
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If permafrost warms (over many years) and is taken over by a forest, is it at all possible to regain the permafrost? How?
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Yes!
Natural succession = a negative feedback! Transition from tundra to shrub/ forest will sequester more C - trees reduce albedo + protect permafrost |
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Is there a critical peat thickness to maintain permafrost degradation resiliency?
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YES!
With thick peat deposits, pfrost has higher resiliency - Synergistic system -- Ice provides water, stability, drainage -- OM provides thermal protection of ice |
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How much land surface do wetlands cover?
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14-18%
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T/F: Wetlands represent the ecosystems of last contact between terrestrial + aquatic ecosystems
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True!
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What are the five wetland classes?
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Bogs
Fens Swamps Marshes Shallow open waters |
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What are the categories/ gradients along which wetlands form?
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- Hydrology
-- seasonal water fluctuation important - Chemistry -- Nutrient (N, P) availability -- acidity, alkalinity -- Base cation content (Ca, Mg, Na, K) - Biology -- types of vegetation, development of mosses |
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What is terrestrialization? How does it happen?
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The changing of lakes into peatlands
- literally changes water surfaces to land (..sort of land) |
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What is paludification?
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OM accumulates in areas + chokes out trees, turns it into a wetland system
- never reaches a steady state (keeps growing) |
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What is the difference between methanogenic bacteria and methanotrophic bacterica?
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Methanogenic: produces CH4 by consuming C
Methanotrophic: consumes CH4 |
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Resilience
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the capacity of an ecosystem to absorb a disturbance and reorganize while undergoing change so as to still retain essentially the same function
(the capacity to change in order to remain the same identity) |
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Regime Shift
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A change in system state from one regime/ stability to another
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Emission =
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Emission = Burn area x Fuel load x Carbon Content x Emission factor
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What kind of tree growth do high severity fires produce? Why is this an issue?
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High severity fires promote hardwood dominance
- Problem because hardwood trees both sequester different amounts of carbon and have a higher albedo |
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Are wetland systems sensitive or resilient to climate change?
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Wetland systems are resilient!
- They have a lot of natural feedbacks built in #1 is when the water table lowers (which can result in disaster... lots of decomp and CH4/C)2 emission), the peat also lowers proportionally - this is because peat is 90% porous and will move with the water table (reducing aerobic zone) - changes in vegetation also help to keep the ecosystem resilient + stable ** however these systems can be tipped very quickly (become very sensitive) when drained |
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What are some CH4 transfer pathways in wetlands?
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Ebullition (bubbling from muck)
Production by methanogenic bacteria Air-water exchange Plants (through roots + stomata) |
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Why does increase in temp/ C fertilization increase CH4 release from plants?
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Increase temp = increase decomposition
Increase temp + CO2 = more efficient respiration |
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What is WTD? Why is it important for wetland ecosystems?
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Water Table Drawdown.
- Important because when the water table lowers, microbial decomposition will release more GHG into the atm... or so we think! |
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What happens to CH4 flux in peatlands when the productivity of vegetation is increased?
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- CH4 flux rises
B/C of: - increased C quality, stock - increased transport through root + stomata (bypassing oxic zone) Therefore CC impact on the CH4 flux will be largely determined by the fate of plants |
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Why does the variability of topography in peatlands help resiliency to climate forcings?
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Some areas (such as hummocks) will act as net warmers while others (lawns) will act as net coolers. The microtopographies are able to balance out ecosystem effects
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Why is hydraulic conductivity important for resiliency of peatland ecosystems?
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When a peatland is stressed and the water table lowers, the peat will lower accordingly as well (90% porosity), and something (don't remember what.. may not be important) lowers the hydraulic conductivity of the area and causes less water to escape through the surface (minimizing further drought)
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Ecosystem responses:
Ecosystem Movement |
Ecosystems migrate relatively intact to new location which is similar to current climate + environment
-Can be used to project new ecosystems ranges under climate change based on established relationships - However it is a gross simplification, and unlikely to actually happen due to different climatic |
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Ecosystem responses:
Ecosystem Modification |
In situ changes in species composition and dominance in response to changes in climate and other environmental variables
- Paleoecological data suggests this happened in the past -However it is difficult to use in practical predictions of trends |
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What is FFMC?
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Relative indicator of the relative ease of ignition and sustainability of flaming fire fuel sources
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What is DMC?
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Tracks moisture in the top of the organic layer (loosely compacted + moderately deep)
- Weather inputs: Temp, RH, rain - Rainfall threshold: 1.5 mm |
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What is DC?
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Drought code
- tracks moisture content in a deep compact organic layer - indicator of seasonal drought effects on fuel's amount of smouldering in deep duff layers, large logs |
