EE107 Midterm 1

What is climate?

 A pattern of variation in temperature, humidity, atmospheric pressure, wind, precipitation, and other meteorological variables in a given region over long periods

Weather

not the same as climate

the present conditions in short amounts of time

Climate

represents the variations of weather events over time (the probability of a big rainfall occurring at a specific time or variations in temperature)

Earth's Four Spheres

Biosphere (living organisms), hydrosphere(water), geosphere(solid rock), atmosphere(gases)

Earth system science is the holistic approach to studying the Earth as a whole system of many interacting parts

What is a system?

• Any part of the universe that can be isolated from the rest for the purpose of observing and measuring changes

• Exchange of energy, matter, or both

• characterized by whether energy or mass is exchanged with surroundings across its boundaries

By observing and measuring changes

systems can be used to study complex problems

limits of the part define

limits of the system

Isolated system

No energy or matter enters or leaves

Closed system

Energy enters and leaves but matter does not

Open system

Both energy and matter enter and leave

Earth is a nearly

closed system, the exchange of matter is rare and hard

• Though helium and hydrogen escaped easily

The amount of matter in a closed system

• is fixed and finite, the mineral resources on this planet are finite and limited

• Can’t throw things out

• If changes are made in one part of a closed system, the results of those changes eventually will affect other parts of the system

Earth System

• Biosphere - Contains all of the planet’s living beings

• Lithosphere - Cold, hard, solid land of the planet’s crust

• Hydrosphere - solid, liquid, gaseous water of the land(including cryosphere)

• People use geosphere and lithosphere interchangeably
  Anthroposphere -  includes the total human presence throughout the Earth system including our culture, technology, built environment, and associated activities

El Nino makes conditions

wetter in the south of the US and drier and warmer in the north during the winter

How do we study complex systems?

• Identify the components of the system and how they interact

• Determine the residence time (how fast do the elements interact, and how fast will a change propagate through the system)

• Identify feedback loops - interactions between elements that tend to amplify (positive feedback) or damp (negative feedback) changes to the system

Reservoirs

places, where energy or matter is stored, are called reservoirs

Flux

Amount of energy or matter added to the source or removed from (sink) reservoir in a given period of time

Steady-state

sources = sinks, no net change in among of material (Can be energy or matter, specified)

Residence Time

Length of time energy or matter spends in a reservoir

• Residence time = amount inside reservoir/total sources or sinks

• Glaciers have the longest average residence time since the rate of water exchange is much slower(flux)

Equilibrium

doesn’t equal steady-state

Positive couplings

Coupled components change in the same direction

Negative couplings

Coupled components change in the opposite direction

Albedo

The proportion of the incident light or radiation that is reflected by a surface

Earth’s average temperature is determined by

• Sun’s energy

• CO₂ in the atmosphere (the greenhouse effect)

  • CO₂ is taken up by plants during their growth

    • Plants grow faster at warmer temperatures

Add together two or more couplings you get

Feeback loop (combination of positive and/or negative couplings  that connects part of the system back to itself

Negative feedback loop

• Stable system which resists change following a perturbation

• Stable or homeostatic

Positive feedback loop

• Unstable system which changes further following a perturbation

• Unstable or not homeostatic

• Amplificiation

Increase in temperature decreases

albedo since it melts ice and snow

• Increased in temperature with decreased albedo

Negative feedback isn’t

negative coupling

Balancing (negative) feedback loops

hold a system to an equilibrium state and make it more stable

• Contain odd number of negative couplings

Reinforcing (positive) feedback loops

• Tend to move a system away from equilibrium and make it more unstable

• Contain either: even number of negative couplings OR all positive couplings

Equilibrium

• Conditons under which the system will remain indefinitely if left unperturbed

• Equiliburum can be either stable or unstable

Stable equilibrium

Pushed by a perturbation, a stable equilibrium state, returns to (or near) the original state

Unstable equilibrium

• Created by a positive feedback loop

• Being pushed by a perturbation, an unstable equilibrium state shifts to a new, stable state

Tipping point

Transitions between different stable equilibrium states

Snowball Earth

Marinoan & Sturtian

Stone is carried and dropped by a

floating ice shelf or melting icebergs and when it plunked into seafloor sediment below, that sediment folded around it

Intense volcanic eruptions and release of sulfur dioxide

a whole area covering 5 million kilometers across Canada and Greenland

• Caused Snowball Earth

• Volcanic eruptions nonstop for 1 million years

Intense volcanic eruptions and rock weather

• CO2 in the atmosphere dissolves in rain and falls to the ground where it reacts with silicate minerals in the rocks. CO2 forms bicarbonate and ultimately becomes locked away in limestones and shale rock formations

Ice-Albedo Feedback

More ice decreases the temperature by reflecting energy away from the land

How did the snowball earth end?

• CO₂ consumption by silicate weather is slowed by the low temperature and ice coverage, while volcanic and metamorphic CO₂ emissions continue unabated

• Conditions of Snowball Earth changed life in the oceans - rise of more complex algae(large cells) over cyanobacteria(small cells)

  • Might have sparked the evolution of multicellular life

Fast feedbacks

Ice albedo - melts all ice

Slow feedbacks

Vegetation feedback - trees migrate northward amplifies warming by absorbing more sunlight than snow

Energy balance

• Rule 1: If Rate In > Rate Out, reservoir volume increases

• Rule 2: If Rate Out > Rate In, reservoir volume decreases

• Rule 3: If Rate in = Rate Out, reservoir volume is constant

Earth energy’s balance

Energy flux from the sun → Earth’s temperature → Energy flux out(reflection and re-radiation

Energy flux

the amount of energy (measured in photons) that passes through a given unit area (perpendicular to the travel direction) per unit time

Joule / second = Watt

Joule = force x Distance

Earth’s energy comes from:

• Internal to the earth (heat from formation of the earth and radioactive decay)

• The sun

• Gravity and Tides

Earth’s temperature depends on

balance between energy entering and leaving the planet

Kinetic energy

measure of the energy of a substance due to motion

Temperature

At a macroscopic scale, a measure of the average kinetic energy of molecules in a particular substance

Absolute zero is hard to reach

when no particles are moving

Conduction

Transfer of heat from one substance to another by direct contact

Convection

• Transfer of energy by the movement of a mass or substance from one place to another (liquid or gas)

• Convection cells

  • lumes of hot and cold liquid which circulate in a fluid

• Heating and cooling is a great example

• Moves heat in the atmosphere and ocean from the equator toward poles

  • Also moves heat around in the interior of the Earth(in the mantle)

Radiation

• Energy transferred by electromagnetic waves

  • X-rays

  • Radio waves

  • Visible light

  • Microwaves

All electromagnetic waves travel

at the same speed(speed of light 300,000 Km/s)

Wavelength

the length of one complete cycle, from crest to crest

Amplitude

½ height between trough to crest

Frequency

number of cycles per second

Energy (E) is proportional to

requency (n), and inversely proportional to wavelength (1/λ)

Electromagnetic spectrum

describes the range of all forms of electromagnetic radiation

Infrared Radiation

Can’t see, but can feel as heat

• Lower energy than visible light

Ionizing radiation

harmful for the body

• Non-ionizing radiation is not harmful and has longer wavelength

Rate out = rate in

• Assume Earth is in a steady state

• Volume of reservoir does not change(system is at steady state or equilibrium)

Solar energy per unit area at any distance

determined by the total amount of energy, (in this case sun’s luminescence, L) divided by the area of a sphere defined by that distance

Solar constant for Earth

1370 W/m2

Solar constant is actually not constant

• But the energy is not exactly constant over time: varies about 1 W/m2 due to sunspot activity on the surface of the sun

• Average radiation intercepted at the top of the atmosphere is approximately 1370 watts/m2

Liquid water is the most essential

ingredient for life, existence of life confirms the presence of liquid water and a warm Earth

UVA and UVB are

harmful for the skin

• UVA causes aging

  • Unlikely for UAC to reach the Earth

• UVB has more energy

SPF only tells you

how many percentage of UVB rays can it block

Broad spectrum

means it has some protection from UVA

Solor constant

how much energy reaches that far (changes based on the planet)

Solar luminosity

how many wattage the sun emits (brightness) (reamins the same)

All normal matter emits

electromagnetic radiation when it has a temperature above absolute zero (K)

Radiation

represents a conversion of a body's internal energy into electromagnetic energy, and is therefore called thermal radiation

Black Body

an idealized physical body that absorbs all incident electromagnetic radiation

If in thermal equilibrium (constant temperature)

• emits blackbody radiation according to Planck’s law

  • Absorbs all lights shined upon it

  • Emits a spectrum of light that can be described by Planck’s law

  • Hypothetical

  • Tells you the amount of radiation as a function of temperature

When temperature decreases

intensity also decreases and peak moves to longer wavelengths

Integrating Planck law over all wavelength

• We get Stefan-Boltzmann law

• Says how much energy will be emitted as a function of temperature

• This results in w/m^2 w=watts

Energy emitted by an object is

• proportional to the fourth power of temperature (in kelvin)

  • Grows very fast as objects grow warmer 

• Plug in the temperature and then also find the SA of the sun

Earth’s energy sink is

the energy escaped (albedo is 0.3A)

Earth’s expected temperature is

-18 C only without an atmosphere

The greenhouse effect makes it

33 C warmer than expected

Greenhouse effect

• Result of warming of the Earth’s surface by the absorption of radiation by molecules in the atmosphere

• Heat absorbed or trapped by gases in the atmosphere. Earth naturally has a greenhouse effect of +33 C

Greenhouse gases

are efficient at absorbing infrared energy

• Absorb energy by temporarily increasing the rate at which they spin or the rate at which they vibrate

• CO2 and water are examples of greenhouse gases

• Energy absorbed by greenhouse gases are emitted back out again

• If there are a lot of greenhouse molecules around, the energy will be reabsorbed by an adjacent molecule

• Greenhouse gases blocks infrared energy from being emitted back into space

The vast amounts of asteroid impacts during the first billion years released

carbon and sulfur gases into the atmosphere which assisted the early Earth life’s surviva

Inside of the Earth

is hot

• Loss of heat through convection drives Plate Tectonics

Plate tectonics sets the stage

for ocean and atmospheric circulation, evolution of life, earthquake, and volcano hazards etc

Primary source of energy internal to the solid earth is

Heat

Primordia heat

• heat left over from Earth forming

  • Heat follow at the core is left over from Earth formation(4.6 Ga)

Radiogenic Heat

• heat produced in Earth by radioactive decay

  • Largely Uranium and Potassium, mostly in mantle

Three major compositional layers in the Earth

• Core - metallic iron solid inner core and liquid oyster core

• Mantle - dense rocky matter

• Crust - thin, less dense rocky matter

Core and mantle have nearly

constant thicknesses

Crust varies by a factor of

9

Average oceanic crust is

8 km thick

Average continental crust is 45 km thick but ranges from

30-70 km

Two crusts differ fundamentally in composition

(Granite vs Basalt)