# Unit 4: Earth And Space

`Weather`: describes the actual conditions in the atmosphere of a specifc time and space.
    - temp, humidity, precipitation, cloud cover, pressure etc.

`Climate`: 

## Balance Of Energy On earth: 

Em Radiation from the sun reaches the earth in many forms
- Most harmful rays (X & UV) are absorbed and blocked by the ozone layer in the upper atmopshere
- Visiible light, infrared and UV (some) light reaches Earth

## Energy Budget Summary

~ 30% is reflected back into space
- 20% clouds
- 10% by air & surfaces like land, water, ice and snow

~70% is abosrbed
- 50% ground (land + oceans)
- 20% air (atmopshere + clouds)
- Eventually, ALL 70% escapes back into space


## Green House Effect

6 Major GHGs:
- CO2
- Water vapour
- Methane
- Nitrous oxides
- Ozone
- CPC (chlorofluoro carbons) -> only man-made sources

## Energy Transfer Within The CLimate System

Major air current: The prevailing winds: west to east
- Rising hot air at the equator & falling cool air at the poles
- pull in nearby air to create horizontal motions from the poles to the equator

Convection Current:
- Clockwise
- Going up drops rain (rising warm air)
- Going down brings drought (Air cools & sinks)

**Note** Due to earth's large size, the maor convection patterns are broken into 3 currents
- Fast to slow the wind is moving faster than earth
- Slow to fast the wind is moving slower, falling behind
- This is called the cariolis Effect

Surface Ocean Currents -> Pushed by the prevaling winds
- Hit land: bend south/north & carry heat from equator to poles

1. Warm currents 
- reach land: warm moist air -> rain

2. Cool Current: cool air
- reach land: old dry air -> desert areas


## Climate Change

Is the global climate changing? How?
- rising sea levels (comparaed past to now)
- changing eco systems / ecosystems dying out due to climate change
- avg temp in other parts of the word (compare past to now)
- melting ice caps
- change in migration patterns due to temp changes

### Evidence Of Recent Climate Change
- Atmospheric temp over land & water
- Water temp
- Size of glaciers (ancient ice)
- amount of sea-ice & snow-cover on land
- humidity

#### Temp of Lower Atmosphere
- fluctuates year to year but is shown to have a clear upward trend in 7 of the 10 decades since 1910
- since 1970, global avg has increased 0.7 C above the long term avg
- The last decade has been the warmest ever recorded
- land heats up faster & more than water
- more land in NH so hotter
- some ocean regions in the antartic have cooled up to 0.8 C 
    - melting of glaciers -> coller water

#### Water Temperature
- Have increased upward trend, recall graph

#### Glacier Size
- Avg size decreased

#### Amount Of Snow & Ice Cover
- Decreasing

#### Sea Level
- rising (thermal expansion & melting ice)
- thermal expansion is when more heat means more energy, particles move around more and such that cover more space (more area and volume)

#### Humidity
- increases

#### Other Indicators
1. Animals disapperaring from/migrating into different territories
    - lyme diease
2. Earlier growth of plants in the spring
3. changes in extreme weather (droguths, floods, hurricanes, tornados)


## Evidence For Climate Change In The Past

### Weather Records 

Mostly temp & precipitation data from

1. direct measurements - equipment that goes back ~ 150 years
2. Anecdotal evicence - goes back ~2000 years (eye witness stories)

Q: How do we know if the climate we're seeing is normal?
- Older data: obtained using indirect measures of climate change ("proxy records")
    - found in deposits of materials found in nature

### Proxy Records

#### Ice corrs
- From galciers & polar ice caps
- Provides data from ~ 800,000 years ago
- produces a new layer every year
- air is trapped when it froms
    - we can directly measure volcanic activity (amount 7 type of dust trapped inside)
    - directly meausre levels of GHG trapped
    - accurately infer avg temp
    - the 2 above has a realtionship, high temp = high CO2
    
#### Tree Rings
- Provides data from ~10,000 years ago
- Can infer atmopsheric temp & precipitation from thickness & annual growth rings
    - thick ring -> warm mosit year
    - thin ring -> cool, dry year

#### Coral Reff Rings
- provides inferred data fro 100s of years of ocean temp

#### Cave rock formation 
- growth rings provide inferred precipitation data for 25,000 - 100,000 + years

#### Sedimentary rocks
- provides fossils of plants animal pollen
- infer temp based of type/spieces of organisms (eg tolerance range)
- lake sediment layer thickness can infer precipitation (more rain = more sediments in lake as rain washes sediments on to the layers)
- provides data for millions of year, but not precise

#### Summary Of Past Climate Trends
- recurring ice ages every 100,000 years for the last ~million years
- each ice age is followed by an "interglacial" period of rapid warming, then gradual colling until the next ice age
- last ice age was 10, 000 years a go, so the earth should be cooling

## Earth's Climate

### Change Of Earth's Orbit Around The Sun
- Caused by gravity of large planets like jupiter and saturn
- causes the ice ages

### Tilt Of the Earth's Axis
- Shifts between 22.1 to 24.5 degrees
- currently at 23.5 and decreasing
- happens rougly every 41, 000 years
- More tilt Bigger seasonal differences
- Less Titl: less seasonal differences
    - midler winters & cooler summer promotes cooling

### Precession or "wobble" of Earth's axis
- happens every ~23,000 years
- changes timing of seasons
- in ~11,500 years, june will be in middle of the winder


**Note:** Combination of alll 3 factors cause the patterns we see in the ice core temp records for the last million years

**Note:** Other Factor: Continetal Drift (over the course of millions of years)
- shfting of tectonic plates alter shape of land mass, mountinas & volcanaos
- tem, precipitation, ocean currents changes

## Short Term Change
- Impaces climate for months/years

Volcanic activity: more ash in air -> reflects more sunlight -> cooler

Changes in Sun's activity: burst of extra energy by solar flares - sunspots

Large glacial melts: changes direction & flow of ocean currents

El Nino / La Nina: equational ocean currents normally flow west in the Pacific ocean
- these currents reverse (En) or magnify (LN) their normal flow in a 2-7 year cycle
- extremes can last up to 9 months
- El Nino: causes droughts in Aisa & Australia & stroms/floods in western Americas (Reversal)
- La Nina: causses monssons in Aisa & Austraia & droughts in western Americas (Enhancement)

## Anthroprogenic Greenhouse Effect
- Human actions that contirbute to the greenhouse effect through premature relase of GHG

#### Burning Fossils fuels
#### Deforestation 
- carbon sink (CO2 -> wood)
#### Agriculture
- Cows speed up decomposition of grass and release of CO2
- Cow farts release methane
- food pyramid -> more meat to eat in weight than grass for same energy
- cattle ranching, clearing large lots of land (60% of amazon for food, deforestation)

#### Household use 
- eg heating, transportation, lighting, gabage in land fills

#### CO2
- natural sources ovlcanic activity, burning organic matter, cellular respiration
- antrhoprogenic sources: combustion of fossil fuels, deforestation
- largest emiiter of CO2 - the oceans
    - But they absorb more than they emit

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