climate change and society midterm

what does the climate depend on?

how much energy goes in vs out

conduction

heat transfer through two surfaces

convection

heat transfer through fluid

radiation

electromagnetic waves travel through empty space

what is the main source of the earth energy

the suns radiation

how does electromagnetic radiation exist?

it exists along the elctromagnetic spectrum

what is the spectrum of radiation on earth

ultraviolet, visable, and infrared

how is the radiation emitted by an object controlled?

temperture

what temperture emits radiation

anything above 0 Kelvin

Stefan Bozeman Law

The highter temperture, the more radiation it emits, and the shorter the radiation wavelengths are

how much energy do we get from the sun

3.9× 10²6 spread over 150 million km (1368 W/m²) , spread over the entire earths surface is 342 W/M²

why is there an energy reduction from 1368 to 342?

sun only shines on the disk, which rotates, dilluting it by 4

albedo

reflectivity

what is the albedo mean annual average of earth

30%

how warm should the earth be in a stable climate

240 in/240 out = 0 F

why is the stavility 0 F when the actual temp is 59 F

atmosphere (greenhouse effect!)

who discovered the greenhouse effect

Joseph Fourier in 1842

what provides evidence that the atmosphere warms the earth

the moon! has no atmosphere and is -9 F

greenhouse effect

transparent to solar radiation, opaque to earths radiation

what causes the greenhouse effect

a small raction of the atmoshpere, greenhouse gases

why does earths atmosphere treat sun and earth radiation differently

sun (short wave/ hot) while earth (long wave/cool)

why did the airforce map which wavelengths are absorbed by different GHGs?

GHG can block the visibility of missles through certain wavelengths

why does the earth emit 239.9 while aborsbing 240.5

ocean intake (0.6)

why does adding ghg warm the earth?

higher ghg makes the atmosphere more opaque reducing energy loss, but there is the same amount of shortwave radiation coming in from the sun, so the planet warms to emit more energy

how do we know that earth has an +0.6 energy balance

space sattelites measure more energy going in than out,

floats in ocean measure heat build up

what are the global temperture knobs

1. the sun

2. albedo

3. the greenhouse effect

why are the poles cold

they recieve weaker sunlight (longer distance to get there)

what causes the seasons

earths axis is at an angle, as it rotates certain areas get more/less sunlight

how is radiation distributed through the earth

loss at poles, gain at tropics

why does weather exist

oceans and atmosphere transfers energy from the tropics to the poles to balance

local temperture knobs

1. solar outputs

2. albedo

3. greenhouse effect

4. wind

5. current

what drives the wind and rains

the sun drives the winds, which drives the rain

is the atmosphere thin or thick

thin

what is the structure of the atmosphere

aranged by layers defined by temperture within altitude

5 rules of the atmosphere

1. warm air is less dense than cold air (the ideal gas law)

2. air flows from high to low pressure at the same height

3. warm air can hold more water vapor than cold air

4. decreasing air pressure cuases it to condense and cool, while increased pressure warms the air

5. 
   

ideal gas law

relative humidity equation

amount of water vapor in the air/ amount of water vapor the air can hold

when the maount exceeds, rain droplets form and fall

how are clouds supressed

1. sinking air contracts and warms

2. relative humidity decreases

3. clouds are supressed

how does rain happen

1. rising air expands and cools

2. humidity increases

3. water droplets form

why are some areas wet and some areas dry

determined by where air rises vs sinks

why is there a rainy band near the equator

hot air rises on the ascending limb of the hadley cells

why are there dry subtropic bands

deserts where air sinks on the descending limbs of the hadley cells

why are there wet mid latitutude bands

warm air collides with and rises over cold polar air fronts underneath to produce storms

why are there dry polar bands

cold air sinks in the polar areas

order of dry/wet zones

dry poles — wet midlatitude fronts— dry subtropics— wet intertropical convergence zone— dry subtropics— wet midlatitude fronts— dry poles

can the wet dry zone bands change?

yes: climate change

circulation is driven by temperture (strong difference, strong circulation, weak difference, week circulation)

the tropics are expanding

is the idea that climate change causes the cold spells proven?

no, probably natural fluxations of the system

5 rules of the atmosphere

1. coriolis force

coriolis force

invisble force from earths rotation that makes winds/current curve

how does the coriolis force impact wind movement

winds are controlled by the air flow between the pressure belts, steered by the coriolis force

where is it generally rainy and dry

rainy where air rises and dry where air sinks

wind belt order

polar easterlies, mid latitude westerlies, tropical easterlies x2, mid latitude westerlies, polar easterlies

what carries heat around the world?

currents

what are the two components of ocean circulation?

1. surface circulation driven by winds

2. deep circulation driven by density

how does the wind push surface currents?

1. top layer deflects to the right due to the coriolis force, which pulls the lower layers with it. the avergae layer rotation is 90 degrees in the NH, 90 degrees to the left SH

2. subtropicle gyres circulate between the mid latitude westerlies and the tropical easterlies

3. equitorial upwellings: cold water from teh depths replaces surface water parted by the wind

4. coastal upwellings: cool water comes from the depths to replace surface water blown away by winds

what do surface currents do?

Move heat around: subtropical gyers pull warm water poleward and cold water equatorward, while cool water upwells along the equator and some coasts

where does the deep ocean overturn?

1. deep ocean is cold, the poles are the only place where deep water and top water is of similar temperture so there can be overturns, everywhere else there is an impenatrable layer of warm water

2. water sinks where it is densest and saltiest

3. deep ocean conveyer belt

4. antartica

why is some of the ocean saltier than others

1. depends on a balance between evaporation and percipitation

2. mountains: wind runs into mountians, rain goes back into the water, making it fresher

3. flat continents: wind blows over, evaporating, making it saltier

4. North Pacific (too fresh to sink) South Pacific( too salty to sink)

what is the deep ocean conveyer belt

sinking causes the deep ocean conveyer belt, where cold water goes north and warm water goes south cuminating in the indian ocean and northeast pacific

why does water overturn around antartica

westerly winds push water offshore, leading to upwelling

why does deep water ocean circulation matter?

1. the deep ocean can take in lots of heat and co2 slwoing down the pace of global warming

2. ocean conveyer belt moves heat northward (without this, north atlantic would get colder which is happening)

3. 
   

why is a glacier a flowing body of ice (it moves)?

1. basal sliding: ice slides over the ground

2. internal deformation: ice crystals flow under the weight of the ice

why do glaciers from?

ice and snow build up faster than it can melt in the summer, compresses into ice under its own weight

how can ice be lost?

1. melting

2. calving icebergs into the ocean

how are ice glaciers size controlled?

mass balance: excess ice flows from accumularion area (cooler) to the ablation area (warmer) to melt

in balance with the cllimate? ice added to the ablation zone offsets mass added in the accumulatuon zone

cool: expands, warm: looses mass and shrinks

what affects sea level?

melting glaciers (add water), warming oceans (expand water) NOT sea ice (already floating)

how much has the sea level rien in the past century?

8 inches: largely due to thermal expansion (inches per century) and melting glaciers (1 foot total) ice sheets (hold 200 feet total of sea level)

how fast can ice sheets melt?

could take over 1,000 years, probably 2-3 feet in this century, up to 6

ice sheet climate feedback loops

1. precipitation: warmer air could bring more snowfall, which could make the antartic ice sheet bigger

2. albedo feedback loop: ice melts, less reflected out, more absorbed by ocean, water temp increases, more ice melts

3. temperture elevation: ice melts, shrinks down, exposed to warmer air, more ice melts

4. basal sliding: melted ice can lubricate sliding and speec up ice flow into the sea

5. ice shelf collapse: ice melts more into the ocean after ice shelf collapses

6. marine ice sheet instability: once melts, retreats indefinitly on ice on land below sea level because discahrge is sped up

why is sea level not uniform around the world/ how it tilts relative to land?

the ocean is not flat, sea level is different around the world

1. ice age: northern landmasses still rebounding from the removal of ice sheets from the ice age

2. gravitational tug: ice sheets exert a gravitational tug because theya re so alrge, when they melt they lose the tug, sea levels fall nearby and rise else where

3. deep ocean conveyer belt

4. wind/ temp: hills on the surface where wind piles up and taller because temperture expands it

what are the sizes of the differnt carbon reservoirs?

1. deep ocean = 40,000

2. coal = 10,000

3. plants = 2,000

4. atmosphere = 820

5. oceans =800

6. volcanoes =0.2

(deep cats always observe volcanoes)

how does carbon flux between carbon reservoirs?

plants soil and oceans: back and forth into the atmosphere

coal and gas: into the atmosphere

deep ocean: out of the atmosphere

how has anthropogenic climate change impacted our system?

relativly small, but has imbalanced the system, half has been taken up by oceans and plants, but other half is buiding up in the atmosphere

when will co2 concentrations stop rising?

when emissions = 0

what are the feedbacks that will further change the climate cycle?

1. plant growth: plants breath co2 and warmer tempertures

2. more wildfires

3. thaw artic soils, releasing co2

4. oceans: warmer (more stratified and less co2 mixing) and more acidic (wont be able to absorb as much co2) = ocean life may change

how long will our co2 take to be absorbed into the atmosphere?

a lot will be absorbed in the next 1,000 years by ocean, some others will be by seashells, the remaining 20% will take hundreds of thousands of years by weathering rock

what is the long term carbon cycle?

acid rain weathers rocks from the atmoshphere , makes shells and erupts as volcanoes, negative feedback loop aas earths thermostat that happens over millions of years

this happens more when its warmer

why is methane important?

fast acting knob, carbon will take forever to leave atmosphere unlike methane (more potent warmer, only stays in the air for a decade

what is forcings?

something outside the climate that pushes it by changing the energy balance, turns one of the knobs (suns energy, albedo, green house affect)

what are the agents of forcing

1. solar ouput

2. changing land cover

3. greenhouse gases

4. volcanic haze

5. pollution

how can you compare different types of forcing

put them into w/m² to measure impact of energy balance

how much direct warming from 2xco2 forcing?

4 w/m² or 1.2 degrees

what are feedbacks?

the initial warming can spark feebacks, which can amplify or dampen the the warming

what are fast feebacks

1. snow ice albedo: (sea ice melts, more heat absorbed by the ocean, temps rise, more sea ice melts)

2. water vapor feedback: human climate change cause - (stronger ghg affect, warmer temps, more water vapor) repeat

3. cloud coverage: high clouds warm because they are cool, reflect little long wave, short clouds cool because they are warm, reflect long wave, middle clouds do little

what are slow feedbacks?

1. vegetation: affects albedo and artic trees (absorb more sunlight than snow)

2. carbon cycle: changing temp/biology/circulation takes centuries

3. ice sheet albedo: melting sheets change albedo but take centuries

which knobs do feeback impact

albedo and greenhouse gas affect

why is water vapor important

green house gas that is not forcing, but feeback, amplifies

how much final warming from 2x co2?

2.5 to 4 degrees

what is climate sensitivity and how do we estimate it?

the final warming from 2 co2, estimated by past climate change, computer models, short term climate change that can be scaled, quantify feedback loops

why is estimated climate change uncertain?

clouds: difficult to simulate in models

why will it take so long for the climate to warm 2.5-4 degrees?

the oceans keep soaking heat up

how does past climate chang impact future climate change?

the more likely it happened in the past, the more likely it will happen in the future

what is a tipping point?

threshold between two stable states, a nudge past teh threshold makes the system jump states abrubtly or slowly depending on time scale of system,

might not be clear until after its passed because world is noisy and tipping points are so finely tuned

when is the tipping point irreversible/ reversible

reversable: when slow change, can reverse if forcing is not turned back enough

irreversable: when fast

deep ocean conveyer belt as a tipping point

cold salty water sinks in the ocean

overturns only if the North Atlantic water is salty enough to sink

freshwater could turn the conveyer belt off

would need to become very salty to turn back on

thus, irreversable and abrupt

greenland ice sheet as a tipping point

snow that has accumulated on the high cold center of the ice sheet

slow and irreversable: takes a long time to melt, bur would need to regrow ice from warmer temps

uncertainty with what the tipping point would be

west antartica ice sheet as a tipping point

an ice sheet resting on land under the water will retreat indefinitly becasue ice grows thicker across the grounding line as it grows thicker

uncertain but probably slow

irreversable, would have to regrow from warmer tempertures

may be already at the tipping point, ice shelf is cracking

artic sea ice as a tipping point

sea ice keeps the artic cool, if it melts would accelerate warming, abrubt but reversable, could regrow if cold enough

half has dissapeared, unsure if it will tip or just be gradual

amazon rainforest as a tipping point

still open to research

heat kills of trees, fewer trees to send water goes back into atmosphere, more trees die, loss of a carbon sink

maybe abrupt maybe reversable

lots of frorest has already been lost, debated how much more is needed to cross the threshold

artic permafrost as a tipping point

contains 2x as much carbon as the atmosphere

warming thaws it, causes it to rot, releasing co2, warming more

uncertain how abrupt, but irreversable