EASC 2919 Part 3: Earth Systems and Climate

How are the Lithosphere - Atmosphere - Ocean - Biosphere connected?

How are the first 3 connected?

Fluxes of matter

Fluxes of heat

What timescale does direct atmospheric sampling give us climate info on?

1850s to present

What do we use for climate info prior to 1850s?

Proxies

What are proxies?

indirect measurements that serve as substitutes for direct measurements

What is the most important proxy?

Stable isotope analysis

What is fractionation?

Process of separation and differential concentration of different isotopes.

How do climate processes relate to fractionation?

Climate processes often cause fractionation, allowing us to use isotope concentrations as climate proxies

How far back do ice cores go?

800kya

What information do layers in ice cores provide?

Past annual snowfall

What information do bubbles in ice cores provide?

Samples of past atmosphere composition and greenhouse gas levels

What information do particles in the ice of ice cores provide (O isotopes, cosmogenic isotopes, ash)?

O isotopes provide past temperature

Cosmogenic isotopes provide past solar activity

Ash provides record of fires and volcanoes

What information does sediment type in sediment cores provide?

Climate processes affecting weathering/transport

What information does pollen in sediment cores provide?

Local climate based on type of plants

What information do microfossils in sediment cores provide?

Species type and isotope ratios in shells indicate ocean conditions

What information do tree rings provide?

Width provides growth conditions (temp, precipitation)

Scars provide fire information

Isotopes

What information do coral rings provide?

Width provides growth conditions (temp, nutrients, pH)

O-18 and Mg/Ca ratio

What is energy in?

Shortwave (UV and visible) from sun

What is energy out?

Longwave (infrared) from earth

What happens to the 342 W/m^2 that comes in?

107 reflected by atmosphere, cloud, and land

67 absorbed by atm

168 absorbed by earth

What is the energy flux into the earth?

168 (absorbed from sun)

324 (GHG)

= 492 total

Why is energy from atmosphere down (324) so much bigger than the one going up (195)?

Greenhouse gases

The sun emits 7.4*10^7 W/m^2, how come the earth only receives 1361 W/m^2?

Because the suns energy spreads out in all directions

If "solar constant" is 1361 W/m2, why in our heat budget is the incoming solar radiation only 342 W/m^2

Because 342 is an average over 24hrs. Energy rarely comes in perpendicular, and half the Earth does not receive energy during the night

How does solar output vary on short time scales?

The number of sun spots changes the amount of energy released per m^2

How does solar output vary on the geological time scale?

The temperature of the sun didnt change but it grew in size which increases luminosity

According to the faint sun paradox, the early sun was 70% as strong as now. How come earth's temperature did not change?

There were much more greenhouse gases back then

Explain orbital forcing

The amount of solar energy Earth receives changes based on its distance and angle from the sun. These changes are called milankovic cycles

What 3 processes compose the Milankovic cycle?

Axial wobble, tilt variation, and orbit variation

Is there a correlation between climate and orbital forcing?

Yes, higher orbital forcing tends to lead to warming

Why doesnt orbital forcing sufficiently account large changes in global heat?

Milankovic cycles act as triggers, which are then amplified by several positive feedback systems

How much solar radiation is reflected by albedo? Be able to find this from the image.

(77 + 30) / 342 = 30%

Explain the ice-albedo feedback

Higher temperatures (initiated by Milankovic) causes ice to melt which reduces albedo causing higher temperatures

Why is the climate most sensitive to the Arctic summer conditions, rather than winter or antarctica?

In summer, a few degree change causes more melting.

In winter, a few degrees doesnt matter

Antarctica is too cold

How do greenhouse gases work?

They let shortwave through, but absorb and re-radiate longwave

How much heat does the greenhouse effect account for? How much has been added due to humans?

30C

Humans have added 1.5

Explain greenhouse gas concentration in early atmosphere

Much more CH4 and CO2

How did oxygen change greenhouse gas concentration in the atmosphere?

CH4 became CO2, and CO2 became organic C

What 4 feedbacks drive climate change?

T and Ice albedo

T and CO2

T and CH4

T and H2O

Explain the CO2 positive feedback

At higher T, CO2 outgasses from water

Explain the CH4 positive feedback

At higher T, permafrost melts and releases CH4

How much of the preindustrial greenhouse effect is water vapor responsible for?

66-85%

Does water vapor trigger or amplify climate change?

Water vapor only amplifies it already-happening changes

Explain the T and water vapor positive feedback

Higher T means water evaporates more, and air can hold more water before forming clouds

How do clouds at different altitudes affect climate?

Low clouds cool the earth, high clouds heat the earth.

Influence of clouds depends on lots of factors

What 2 factors affect cloudiness?

Temperature

Particulates

How does temperature affect cloudiness? How does this affect earth's energy budget?

Higher temp causes more water vapor in air, while simultaneously forming less clouds.

More GHG and less cloud cooling => warming

How does presence of particles affect cloudiness?

Particles act as cloud condensation nuclei (CCN)

Will a cloud over land or ocean have a larger cooling affect?

Over ocean, because ocean has lower albedo than land

Why is DMS from plankton particularly important as a CCN?

Because clouds over ocean are limited by CCNs rather than amount of water vapor, and ocean has lower albedo

Where do CCNs come from?

Volcanoes, dust storms, biology, humans

What effect do human emissions have?

Emissions actually increase clouds, causing cooling

Explain the direct and indirect effects of aerosols on radiative balance

Direct: Reflected (sulphates) or absorbed (soot)

Indirect: serve as CCN

What are 2 major geological sources of aerosols?

Volcanoes

Wildfires

What 3 ways does ocean impact climate?

Absorb and redistribute heat from equator

Ice albedo

Absorb CO2

Source of water vapor and CCN

What happens if THC shuts down?

No more Carbon will be brought to the bottom

How does lithosphere directly impact climate?

Volcanoes (GHG heat, aerosols cool)

How does lithosphere indirectly impact climate?

Ocean circulation

Recycling Carbon through subduction

Weathering and transport brings Si and micronutrients, causing plankton blooms

How does biology impact climate?

Oxygen lowered CO2

Albedo and evaporation

Calcareous shells remove CO2