Climate Change Midterm

why is the earth warm

ozone, greenhouse gases, sun, albedo, orbital pattern, geothermal flux

Albedo

the light that a surface reflects

Scale of 0-1 - if it is all reflected, the albedo is equal to 1

Earth is about 0.2

Albedo values:

Ocean: 0.05

Forest: 0.1

Ice: 0.8

low albedo

dark-colored surfaces absorb more incoming solar radiation- warmer

Greenhouse gases

Allow thermal energy to escape

Absorb infrared light, re-emit, sending some to surface

Increase in CO2 by decomposition

Decrease in CO2 by photosynthesis

Insolation

Incoming solar energy

IN- UV and visible light

OUT - infrared light

Increase in insolation - increase in plant growth (decrease Co2)

Energy Balance

Outgoing = incoming

Ts = [S/(4σ) *(1-A)] 0.25

Amplifying loops

Enhance a problem

Temp increase causes decrease in sea ice which causes decrease is albedo- leds to more increase of temp

Stabilizing loops

Balance a problem

Increased decomposition leads to more CO2 which then has more photosynthesis which traps CO2

Residence Time

Duration of time something spends somewhere - volume/flux

Carbon Reservoirs

Photosynthesis, respiration, combustion, erosion and weathering, diffusion, and ocean mixing and sedimentation

Steady-state equilibrium

he point at which the flow of different ions inside and outside are equal and opposite, but no single ion is at equilibrium

Stable/unstable equilibrium

Stable equilibrium occurs if after a body has been displaced slightly it returns to its original position when the displacing force has been taken away

Unstable equilibrium occurs if after a body has been displaced slightly it moves farther away from its original position

Infrared radiation

type of radiant energy that is invisible to the eyes; we can only feel it in the form of heat

Sun or fire

Daisyworld

Three main phases- minimum, optimal, maximum

period of rapid growth, reaches temperature limits (stable feedback loop), rapid decrease

• white daisy albedo is decreased - temperature of the planet becomes much more similar to that of the dead planet.

• soil albedo was increased the planet would also have a longer lifespan - opposite effect of decreased daisy albedo

• When the optimal temperature is decreased the lifespan of the planet also decreases- similar to what happens when daisy albedo is changed

Thermohaline circulation

deep-ocean currents driven by differences in the water's density

controlled by temperature (thermo) and salinity (haline)

About a 1000 year process

Example: polar regions ocean water gets cold, forming sea ice. - surrounding seawater gets saltier, because when sea ice forms, the salt is left behind. As the seawater gets saltier, its density increases, and it starts to sink

Oxygen isotopes

O16, O17, O18 - O16 is most common (99.76%)

O16 is lightest

O16 more likely to evaporate while )18 more likely to precipitate

Colder - more fractionation of O16

Lighter (O16) - more positive (colder)

Darker (O18) - more negative (warmer)

Glacial flow

Flow downslope- middle has least deformation

Outward and downward flow

Ice rafted debris

Iceberg calving events (heinrich - cold then warm) creating iceberg armadas

Ice isotope records

Snow - temp 18O

Firn- small circulation

Ice - closed to atmosphere

18O - ice age

CO2 - gas age

CH4- gas age

Lower 18O values indicate colder temperatures.

Higher 18O values indicate warmer temperatures.

Milankovitch cycles

Milankovitch cycles predict a slow cooling trend over the next several thousand years, but human-induced warming is overriding this natural cycle

These cycles are responsible for the timing of ice ages over the past 2.5 million years

Eccentricity

100,000 year cycle

ranging from more circular to more elliptical

When the orbit is more elliptical, Earth receives varying solar energy throughout the year, intensifying seasonal contrasts.

When the orbit is nearly circular, seasonal differences are less extreme.

Tilt

41,000 year cycle

greater tilt increases the intensity of seasons—warmer summers and colder winters.

A smaller tilt results in milder seasons, favoring ice sheet growth in high latitudes.

Precision

20,000 year cycle

Wobble of earth axis

Affects the timing of the seasons relative to Earth's position in its orbit.

Can amplify or weaken seasonal differences depending on whether winter occurs when Earth is closer to or farther from the Sun

Greenhouse Effect

process through which heat is trapped near Earth's surface by substances known as greenhouse gases

fractionation

O16 is more likely to be evaporated over O18 which makes ocean ‘heavier’

Glacial mass balance (acc vs. ablation)

Accumulation - net gain- addition of snow and ice

Ablation - net loss - melt and iceberg calving, and sublimation

Greater accumulation- glacier advances

Great ablation - glacier retreats

Control on glacier size

Temperature decrease - bigger glacier

Precipitation decrease - smaller glacier

Moraine

Lateral - side of glacier

Terminal - toe of glacier

Medial - two lateral moraines join together - different from esker because it is unsorted

ICE RETREAT - last moraine has to be youngest

Younger Dryas (signatures & mechanisms)

Paleotemperature proxies

Oxygen isotope ratios (δ¹⁸O) in Greenland ice cores show a rapid cooling of ~10°C over just a few decades.

Glacial evidence

Re-advancing or slowing retreat of glaciers in the Northern Hemisphere

Mechanism: A large influx of freshwater from glacial Lake Agassiz into the North Atlantic disrupted the Atlantic Meridional Overturning Circulation (AMOC).

Effect: This disruption shut down or weakened the Gulf Stream, reducing northward heat transport and plunging the North Atlantic region into a cold phase.

Heinrich events (signs and mechanisms)

Ice rafted debris

Iceberg calving events (heinrich - cold then warm) creating iceberg armadas

Little Ice Age

period of regionally cooler climate occurring roughly between 1300 and 1850

Warming began in the mid-19th century, well before modern industrial CO₂ emissions surged

Possible weakening of the Atlantic Meridional Overturning Circulation (AMOC) may have reduced northward heat transport

Sea-level rise

Thermal Expansion

Melting of Ice

Threatens ecosystems and humans

Adaptation, mitigation

two main strategies for addressing climate change

Mitigations - Actions that reduce or prevent the emission of greenhouse gases (GHGs) to slow down global warming.

Adaptations - adjustments to natural or human systems in response to actual or expected climate impacts

Climate skepticism

doubt or denial regarding the reality, causes, severity, or consequences of climate change—particularly the role of human activities in driving global warming

Why is there more warming projected for the arctic?

Arctic amplification, which results from several interlinked feedback mechanisms that make this region particularly sensitive to climate change.

Snow and ice reflect most sunlight (high albedo), but as they melt, darker ocean or land surfaces are exposed, absorbing more heat.

Effect: Warmer temperatures → more melting → more heat absorption → even warmer temperatures.

Why will the temperature continue to increase even if we are able to implement mitigation strategies now? Consider feedbacks, residence time.

The oceans absorb over 90% of the heat from global warming.

Oceans have a high heat capacity and respond slowly, meaning the warming from past emissions is still "in the pipeline" and will gradually be released into the atmosphere.

CO₂ stays in the atmosphere for hundreds to thousands of years.

Even if emissions drop to zero, existing CO₂ will continue trapping heat

Positive Feedback Loops

Once triggered, these can reinforce and prolong warming even without new emissions:

Ice-albedo feedback: Less snow/ice → more heat absorbed → more melting.

Permafrost thaw: Releases methane and CO₂, amplifying warming.

Water vapor feedback: Warming → more evaporation → more water vapor (a greenhouse gas) → more warming.

Forest dieback: Heat and drought stress ecosystems, reducing carbon uptake and potentially releasing stored CO₂.