Geology

test 1

What is weather?

**Atmospheric changes with short timescales of days to a few week** 

* Limited Predictability 
* Can change rapidly and quickly based on location and time

What is climate?

**Atmospheric changes with long timescales of months or more** 

* Potentially predictable - more reliable to determine a place’s climate
* Climate varies naturally within statistical limits
* Climate change occurs when variation exceeds the statistical limits
* Does not change as quickly or rapidly

What is the climate system and what are the main components? 

an interactive system consisting of five major components:

the atmosphere, the hydrosphere, the cryosphere, the land surface and the biosphere, forced or influenced by various external forcing mechanisms

What is being exchanged between the different parts of the climate  system? 

Examples for these processes/exchanges?

Climate system is an exchange of energy, matter, momentum, and carbon

* Changes in the ocean: Circulation, sea level, biogeochemistry
* Changes in the land surface: land use, vegetation, 

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What is radiative forcing? What causes it? 

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Radiative Forcing - **Imbalance between Earth’s incoming and outgoing radiation**

•Measured at the top of the atmosphere

What causes radiative forcing?

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* The ultimate driver of climate forcing is the SUN 
* If there is an imbalance, then our climate is forced to react to it and change
* Currently happening 

What is a positive feedback process?

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* A positive feedback is an amplifying process and could cause both either increased cooling or warming
* EX: Ice-Albedo feedback - Changes in sea ice provide positive feedbacks 

What is a negative feedback process?

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* A negative feedback is a de-amplifying process and could cause both either decreased cooling or decreasing warming 

Since when do global temperature measurements existed?

Since 1880

What. is global temperatures and how are they measured globally?

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* Global temperatures are the average surface temp around the globe 
* Thermometers, Air balloons, satellites

What should be the minimum number of years used as a base period?

at least 30 years

Why are temperature anomaly records used, rather than absolute temperature values?

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* Temperature anomalies show the deviation relative to a long term average
* Anomalies more accurately describe climate variability over larger areas than absolute temperatures do, and they give a frame of reference that allows more meaningful comparisons between locations and more accurate calculations of temperature trends.

By how much has global temperature increased over the last century?

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* The global temperature has increased 1.2 degrees celsius

Which areas have heated up the most over the last century and why?

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* Heating is centered around the northern arctic region
* De-arctic amplification - the ice-albedo feedback is a good explanation for this heating
* Increase in temperature on continents as opposed to oceans
* mainly because of differences in how these areas reflect energy from the sun.

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What is Earth’s cryosphere? 

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* The frozen parts of our climate system - anything snow or ice

What are some recent trends in Arctic sea ice extent, thickness, volume?

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* Ice forming directly in the ocean 
* 2m thick
* Maximum extent is usually in march, covers 3% of earth’s surface
* Downwards trend in arctic sea ice
* Ice is becoming thinner and replaced with young ice
* Rapid decline of multiyear ice volume

By how much would global sea level approximately change if the Greenland Ice Sheet melted?

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* Contains 2.85 million km of ice
* Losing >200 Gt of ice per year
* Rapidly melting and warming
* Total melting would lead to a 7 m increase in sea level

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By how much would global sea level approximately change if the West Antarctic Ice Sheet melted? 

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* Contains 27 million km of ice
* Melting of the whole antarctic ice sheet would add 60 meters to the global sea level

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By how much would global sea level approximately change if all of the Antarctic ice melted? 

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* Melting of the WAI should raise sea level by \~6 meters
* Less stable than the East AIC
* Contains 13% of antarctic ice masses

Why might collapsing ice shelves accelerate ice sheet decline?

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* When an ice shelf disintegrates it speeds of the ice loss in the ice sheet
* There is nothing to stop the flow of water

What is permafrost?

Permafrost is soil with annual temp at or below the freezing point for two successive years

* Frozen ground 
* Snow covers permafrost much of the year

How does permafrost melting influence the climate system?

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* Permafrost melting releases greenhouse gasses
* Lakes and pools form as permafrost melts
* Bacteria release methane into the atmosphere 

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By how much has global sea level risen over the last century? 

3\.4 mm per year

25 cm

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How is the global sea level being monitored? 

Tide gauges- stations at the shoreline that measure the height of sea level

Satellite Altimetry 

What has been the rate of sea level rise during the past 2-3 decades?

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2\.4 mm per year

What are the major causes for the rise of sea level over the past 2-3 decades?

Greenland ice sheet is contributing to this rise, land glaciers

Warming of the ocean is a big contribution to the rise

What are some observed trends over the past decades in ocean heat content, heat waves, precipitation extremes and distribution?

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* Ocean heat content is increasing and the ocean is absorbing it
* Heat waves are a period of two or more consecutive days when the daily minimum temperature exceeds the 85th percentile of historical july and august temperatures for that city
* Heat waves have increased in duration, frequency, and intensity
* Precipitation has a slight upward trend
* More extreme precipitation events across the country
* More intense rainfall
* Increased flooding
* West is droughting while east is raining 

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How has hurricane intensity changed in recent decades, and what is the likely cause for this change?

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* Intensity of hurricanes increased in the last 50 years
* Wind speed and pressure is the likely cause for this
* Frequency has no increase or trend therefore it cannot be considered effected by climate change

What are some characteristics of the Sun, the driver of Earth’s climate (e.g. TSI, temperature in Sun’s core and at the surface)?

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* Major source of all radiant energy receives on Earth
* Temperature at the core of the sun is 15 million degrees kelvin
* Surface temp is 6000 degrees kelvin

What are sunspots?

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* Sunspots are produced by magnetic field, cooler areas of the photosphere
* Disturbances of strong magnetic fields
* Dark spots surrounded by brighter areas (Faculae)
* Sun creates solar flares near sunspots

How do sunspots influence the TSI?

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* More sunspots = higher solar output and TSI
* Sunspots only modulate TSI by 0.1%

What is the sunspots cycle like?

* An 11-year rhythmic cycle of sunspots in called the Schwabe cycle
* Sunspots very active during the first half of the 20th century, but decrease since 1978

Solar activity can not be responsible for recent climate change

What are some characteristics of orbital cycles/orbital parameters, their effect on incoming radiation and Earth’s climate?

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* Orbit changes between circular and slightly elliptic
* Eccentricity of ellipse changes over time 
* The closer we are to the sun, the more incoming radiation and heat on Earth
* Obliquity - changes in the tilt of the earth’s rotation axis

Recent warming can not be explained by orbital cycles - current orbital positions should produce cooling trend

What is the Milankovitch Cycles?

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* Milankovitch Cycles (orbital cycles) have been connected to ice advances and retreats during the last ice age

Composition of Earth’s atmosphere?

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* 78 percent is Nitrogen, 21 percent is oxygen
* Greenhouse gasses - 0.0406 percent Carbon dioxide, Hydrogen, Neon

What are the layers of Earth’s atmosphere?

Troposphere, Stratosphere, mesosphere, thermosphere

What are the major greenhouse gasses?

* Water Vapor, Carbon Dioxide, Methane, Nitrous Oxide, Ozone, Halocarbons

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Carbon dioxide

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* Biggest source: Burning fossil fuels, deforestation
* Natural source: Volcanoes 
* Keeling curve: Longest running record of CO2 Level
* CO2 Concentration: 425 parts per million (ppm)
* Produce 10 Gigatonnes of Carbon Dioxide Per Year

Methane

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* Natural source: Wetlands, termites
* Anthropogenic source: Energy ruminants, landfills, biomass burning

Nitrous Oxide

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* Natural: Bacteria life in soils, microbial activity in the oceans
* Anthropogenic: Fertilization, combustion engines, medicine, rocket engine

Ozone

* Ozone in the lower atmosphere is a greenhouse gas
* Ozone formation by biomass burning
* Photochemical smog from car exhaust with high ozone concentration
* Good ozone in stratosphere, bad ozone in troposphere (where we are)

What is the ozone like in the troposphere?

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* Contains water vapor 
* Weather happens here
* Convection
* Temp decreases with higher altitude

What is the ozone like in the stratosphere?

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* Natural ozone layer increases temperature
* Protects us on earth from UV radiation
* Increasing temperature caps convection

What is the ozone hole?

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* damaged ozone layer in the stratosphere due to reactions of chlorofluorocarbons (CFCs) with ozone especially at the surface of stratospheric clouds over Antarctica 
* Sun radiates harmful radiation the hurts cells and ozone helps protect that
* Net effect: cooling