ESS 21 Midterm 1 Study Guide
Elements are defined by
# protons in the nucleus
Eccentricity
(100,000 year cycle) - how elliptical Earth's orbit is
Precession
(23,000 year cycle) - position of equinoxes over time
Obliquity
(41,000 year cycle) - how tilted the Earth's axis is
Why Does Our Climate Change?
(Check lecture 5 for more details) 1. Changing amount and distribution of incoming energy - Variations in solar output - Changes in Earth's orbit (Milankovitch cycles) 2. Changing amount of incoming energy reflected - Surface characteristics - Aerosols 3. Changing amount of outgoing energy absorbed - Aerosols - Changes in greenhouse gas concentrations 4. Changes to internal components of the climate system - Distribution of continents, and atmosphere and ocean circulation - Feedback processes
Energy
- "The ability to do work, to move matter" - Energy is often measured in calories or joules (note, 1 calorie = 4 joules)
The Cryosphere: What is it?
- "The elements of the Earth system containing water in its frozen state, and includes: snow - lake and river ice - permafrost, and seasonally frozen ground sea ice - glaciers, ice caps, ice shelves and ice sheets"
Estimates of warming from IPCC AR5 2013 range from 1.5 - 4C (2.5-6F)
- 6c: global catastrophe - 5c: food prices double, billion refugees worldwide, mass extinctions - 4c: arctic Canada is new agricultural area, deserts expand - 3c: Amazon rainforest dries out and burns - 2c: Arctic becomes ice free in summer, coral reefs die - 1c: droughts in US, loss of snowpack, hurricanes start to hit South Atlantic - Warming will not be distributed evenly - much greater in the Arctic due to positive feedback processes
Hydrogen Bonds Between Water Molecules
- All substances have bonds between the molecules = Van Der Waal's forces - H is so small that electrons are shared more unequally in covalent bonds and molecule is more polar - Polar molecule results in stronger electrostatic forces between molecules = hydrogen bonds - Cause molecules to be more strongly attracted to each other
Last 2 Million Years (Climate)
- Alternating glacial (cold) and interglacial (warm) periods every 100,000 years or 40,000 years - Climate changes due to: - Milankovitch cycles - Amplifying climate feedbacks e.g. increased CO2
Middle Cretaceous - 100 million years ago
- Antarctica during Cretaceous (no ice, dinosaurs roaming) - Coral reefs grew closer to the poles Sea level was 100-200 meters high than today (no ice sheets) - Global average temperatures are estimated to be 6-14C warmer - Why? 1. Continent positions changed Earth's albedo and ocean circulation 2. CO2 levels were between 8-10 times that of today (3900 ppm)
Snowball Earth Hypothesis
- At one point (700 million years ago) Earth may have been almost entirely ice covered and much colder because of this feedback - So, why are we not a frozen ball of ice still? Volcanoes.
Why is it Colder in Highland Areas?
- Because in the troposphere temperature decreases with altitude - With increasing altitude - Air pressure and density decreases 1. Radiation from the sun travels through the atmosphere and heats the ground 2. Ground surface then emits infrared radiation which is absorbed by gases just above the ground 3. Further from Earth's surface the colder it is in the troposphere
How Humans Raise CO2 levels?
- Burning fossil fuels - Deforestation
Molecular Structure of Water
- Chemical formula = H20 - Each shared pair of electrons is called a covalent bond - Covalent bonds are strong - a lot of energy is needed to break them - Bend of molecule means that there is a more positive side and a more negative side of the molecule = polar - 105 degrees bend is cause of most of the weird properties of water
How Do Cloud Droplets Grow?
- Clouds at mid and high latitudes, contain a mixture of ice crystals and/or supercooled water - Supercooled water = water at or below 0C but remains liquid due to lack of ice nuclei - Clouds at mid and high latitudes, contain a mixture of ice crystals and/or supercooled water 1. Bergeron process 2. Riming (falling ice crystals collide with supercooled droplet that freeze onto them) 3. Aggregation (two ice crystals join together - works best close to 0C when there is a thin layer of water on surfaces)
Cloud Formation
- Clouds form when air becomes saturated and water droplets or ice crystals form - To saturate air we can: - Add water vapor (e.g. by more evaporation over lakes/ocean) - Cool down the air (e.g. by forcing the air to rise higher in the atmosphere)
Hydrogen Bonds: Density of H20
- Density = how heavy a substance is for its size Related to how closely packed together the atoms are - As temperature decreases, molecules have less energy so are slower and occupy less space = thermal contraction - So why does ice float? - Molecular structure controls the properties of ice e.g.. - Lower density than water due to its open structure so ice floats - Also results in 6-sided snowflakes due to hexagonal structure
The Koeppen System
- Distinguishes different climates by using boundaries in vegetation types associated with characteristic temperature and precipitation patterns - Regions important for the cryosphere 1. polar areas 2. Areas with cold winters (severe midlatitude) 3. Highland regions
History of Ice on Earth
- Earth is presently in a cool period - dark bands sow times when large ice sheets were present on continents. We are currently in an "Ice Age" - During much of Earth's history, there is no evidence for ice - much warmer atmosphere, warmer oceans and higher sea levels
Earth's mechanics: c) Tilt (23.5 degrees)
- Earth's tilt is the main cause of the seasons - The tilt affects the amount of solar energy reaching the top of Earth's atmosphere through the year by influencing: - Period of daylight - Beam spreading - Atmospheric beam depletion
Electromagnetic Energy
- Electromagnetic waves move together at the speed of light, no matter what the amplitude or wavelength - Wavelength = "distance between crests" - Higher energy waves have shorter wavelengths - Electromagnetic radiation can have any wavelength but we have created certain categories of radiation based on wavelength
What emits radiation (electromagnetic energy)?
- Everything - Temperature > 0 Kelvin <-- absolute zero/starting point - 1 Kelvin = 1 degree Celsius
Some major impacts of melting cryosphere on the Earth system:
- Feedbacks on climate system e.g. less reflected sunlight, release of methane/CO2 - Changes in ocean and atmospheric circulation - Changes in ecosystem that depend on snow and ice
What Can Be Done to Prevent Climate Change?
- Geoenineering - alter the climate system deliberately - Reduce our emissions
Last 50 Million Years (Climate)
- Gradual cooling over last 50 Myrs - Climate changes due to: - Redistribution of continents - Changes in ocean and wind currents - Gradual fall in CO2 levels
How 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?
Why Do We Experience Seasons?
- If the amount of energy coming from the sun is more or less constant...why do we experience seasons? Because... 1. The Earth is spherical 2. of the mechanics of earth's orbit about the sun - Tilt
In a Warmer World
- In mid latitudes: - More precipitation will fall as rain rather than snow - Snow will be more likely to melt or sublimate, shortening the length of time with snow cover and decreasing average snow depth - In high latitudes: - More water vapor in atmosphere so more snow - Positive snow-albedo
Work
- Lifting anything - Pushing or pulling anything - Doing just about anything - Kinetic vs. potential energy
Snow On The Ground: Insulation
- Low density of snowpack insulates the ground from very cold air temperatures above the snowpack - Ground emits heat that it has stored from the summer - Heat (and moisture) is trapped within the air pockets and keeps temperature near soil surface close to 0C - Protects animals and vegetation (e.g. roots)beneath snowpack - Snow cover and duration will also affect permafrost and melting of sea ice and glaciers
Changes of State
- Molecules are held together by hydrogen bonds. As the molecules gain more energy these can be more easily broken apart and are overcome entirely as water evaporates to form a gas - You put ice cubes in your drink to cool it down. This is because: - The ice absorbs heat from the liquid as it melts
Why Has Our Climate Been Changing?
- Natural forcings include: solar variability, volcanic eruptions, changes in Earth's orbit - Anthropogenic forcings include: greenhouse gases, aerosols, surface changes
Faint Young Sun Paradox
- Over 4.5 billion years, the luminosity of the sun has gradually increased by 30% - But...there is evidence for liquid water on Earth for most of Earth's history which has allowed life to exist
Current Interglacial - Last 10,000 Years (Climate)
- Relatively very stable" interglacial" climate - Has allowed development of agriculture and civilization
Climate Changes by 2100: Uncertainties
- Response of clouds/precipitation - Potential for sudden shifts in climate state that involve ocean circulation/sea ice changes/biosphere changes - Ice sheet volume loss - will the flow of the big ice sheets change enough to significantly affect the amount of sea-level rise expected in a warming world? - But...by far the biggest uncertainty going forward are human factors
Snow On The Ground: SWE
- SWE = "snow water equivalent" - Snow on the ground (snowpack) contains a lot of air - New snow has a density of 5% to 20% of liquid water - "snow water equivalent" therefore used in place of snow depth
Hydrogen Bonds: H20 Temperature vs. Heat
- Temperature = average kinetic energy of molecules (how fast they move) - Amount of heat = total kinetic energy of molecules
The Solar Spectrum
- The sun emits a range of wavelengths - called a spectrum - Flux: amount of radiation coming out (y-axis) - Wavelength (x-axis)
Blackbody Radiation
- The sun's spectrum is very similar to a blackbody - What is a "blackbody"? Anything that: 1. Absorbs all light shined upon it 2. Emits a spectrum of light that depends upon its temperature
Intergovernmental panel on Climate Change
- This should always be the first place you look for information related to climate change - Latest report came out in 2013/3014 - Openly peer-reviewed by scientific community and the summaries must be approved by all participating governments (over 120 countries) - This is not simply an earth system science issue
Weather vs. Climate
- Weather: the state of the atmosphere at a given time & place (what you get) Temperature Air pressure Humidity Cloudiness Wind speed & direction - Climate: average weather over a long period of time (30 years or more) in a given place (what you expect)
Water Vapor Content
- What happens if temperature increases? - undersaturated (more evaporation can take place if water is available) - What happens if temperature decreases? - Supersaturated (condensation/deposition will take place) - What happens if you add more water vapor? - Supersaturated (condensation/deposition will take place)
Snow On The Ground: Avalanches
- When snow piles up on a slope an avalanche can form - rapid flow of snow down a slope resulting from a mechanical failure in the snowpack - Triggers include snowstorms, melting, earthquakes, rockfalls, skiers, or explosives.
Past Climate Summary
- World has been warmer and colder than today in Earth's history - But...human civilization is very much "adapted" to the current, very stable climate - The RATE of climate change over the next 100 years is greatest threat-likely 10 times faster than any other change in the last 65 million years
A system
- an isolated portion of the universe under consideration (examples - this room, UCI, the atmosphere, the Earth) - The boundaries of the portion define the limits of the system - A system is characterized by whether it exchanges energy or mass with surroundings across its boundaries
Power
- how quickly energy is used - example: how many "calories burned per minute" - or: "joules per second" = 1 watt
Terminal velocity
- speed at which gravity = drag - Droplet will fall to Earth when: speed of falling > speed of winds (updrafts) - Drag: force depends on rate of fall and surface area of droplet (proportional to r^2) - Gravity: force depends on mass (proportional to r^3) - What will happen to terminal velocity as the radius of the droplet increases? - Increase
Past Climate: How Do We Know?
1. Instrumental Record (recent, 1800s to present) 2. Geological Record - Fossils - Landscape features (sand dunes, dry lakes/ rivers, glacial valleys etc.) 3. Proxy Records - "Records of natural events that are controlled by, and closely mimic, climate" - Natural "layered" records - What created Yosemite valley? erosion by ice
Hydrogen Bonds: H20 Thermal Properties
1. Specific Heat a. Specific heat = energy needed to raise 1 kg of a substance by 1 degree celsius b. Causes water to have a high heat capacity - it can absorb or lose large amounts of heat with changing temperature very much so moderates Earth's climate, especially along coastlines 2. High melting and boiling temperatures - Water has much higher melting and boiling points than compounds of similar mass Why? Hydrogen bonds 3. High latent heat of vaporization - Latent heat = energy required to change state of substance - Temperature does not change, energy is 'stored' - Water has highest latent heat of vaporization of any substance (2,500,000 J/kg) - Large latent heat exchanges during evaporation and condensation transfer energy around the Earth, keeps Poles warmer
Factors That Control Earth's Temperature
1. Sun's luminosity (power) 2. Distance from the sun: combine to create "solar constant/solar flux density" - Solar flux density: amount of solar power per unit area on the surface of a sphere centered at the sun - The solar constant of mars is less than the Earth's 3. The Atmosphere and albedo - What happens to incoming solar radiation? - Albedo: percentage of solar energy reflected away, fraction of solar energy reflected away - Planetary albedo = 30% (or 0.30) - Why doesn't the Earth get hotter and hotter? - because of Stefan-Boltzmann's law 4. Earth's temperature (blackbody and feedback) - Earth's Energy Balance - Solar energy absorbed = terrestrial energy emitted 5. Greenhouse effect - Sun's peak output is visible (shortwave) light Earth's atmosphere transmits visible light. The light that reaches Earth's surface is absorbed and warms the surface - Earth's surface is much colder than the sun so - Earth emits radiation with a longer wavelength - infrared radiation - Greenhouse gases in atmosphere absorb infrared radiation which warms the atmosphere Atmosphere therefore also emits infrared radiation - some goes out to space but some is emitted towards Earth again
What is the climate "forcing" that has the greatest uncertainties associated with it (i.e. biggest error bars)?
Aerosols
Why do some clouds cause precipitation and some don't?
Because cloud droplets/crystals must grow big enough to fall
Why are the Poles Cold?
Because the Earth is spherical resulting in beam spreading
Earth's mechanics: b) Rotation
Earth spins completely once per day (24 hours) around its axis - reason why we have day and night
Snow On The Ground: Life
Life has made amazing adaptations to cold temperature and snow (e.g. fur, hibernation, bacteria, etc.)
Earth's mechanics: a) revolution
Only very small influence on seasonal heating
Saturation
amount of water in gaseous phases is maximized
Feedback loops
When the output of a system contributes to the input....very important to cyrosphere and climate system
Biosphere
all of Earth's organisms + any organic matter which has not decomposed
Hydrosphere
all of earth's water (e.g. oceans, lakes, underground water, and includes the CRYOSPHERE)
Residence time
amount inside reservoir/total source OR sinks
Flux
amount of material added to (source), or removed from (sink) reservoir, in a given period of time
Reservoir
amount of material of interest is a given form
Positive feedback
amplifying; increasing leads to increase, decrease leads to decrease - For example: the interaction between sunlight global temperature, and ice
Negative feedback
damping; change in output leads to opposite change in input
Saturation Vapor Pressure
maximum vapor pressure at a given temp
Atmosphere
mixture of gases (N, O, Ar, CO2, H20 vapor) that surrounds the Earth
Vapor pressure
pressure of a gas above a liquid
Geosphere
solid Earth (rock and regolith)
Steady state
sources = sinks, no net change in amount of material