ATOC 1060 Study Guide EXAM #1 -Giglio

What are obliquity, eccentricity, precession?

obliquity: Angle of tilt of the Earth's axis of rotation. Eccentricity: Shape precession: Direction of axis

What is the current CO2 level in the atmosphere?

~408 ppm

Permafrost

20% of landmass is affected by seasonal and permanent permafrost Permafrost is cooled at surface and heated from below (geothermal) Def: a thick subsurface layer of soil that remains frozen throughout the year, occurring chiefly in polar regions.

Explain Wien's law. Why is it important?

Law states that the black body radiation curve for different temps peaks at a wavelength is inversely proportional to the temperature.

What causes the equilibrium temperature of a planet to decrease or increase?

Occurs when variation exceeds statistical limits and there is a change in long term stats of temperature over decades or longer.

What is the difference between a positive and a negative feedback loop? What characteristics does a positive feedback loop have, what about a negative feedback loop?

(+) a response that reinforces the change detected. (-) a response that is the reverse of the change detected, functions to reduce the change.

How hot is the sun's surface?

5,778 K

What are RCPs?

A Representative Concentration Pathway (RCP) is a greenhouse gas concentration (not emissions) trajectory adopted by the IPCC for its fifth Assessment Report (AR5) in 2014. It supersedes Special Report on Emissions Scenarios (SRES) projections published in 2000. Four pathways have been selected for climate modeling and research, which describe different climate futures, all of which are considered possible depending on how much greenhouse gases are emitted in the years to come. The four RCPs, namely RCP2.6, RCP4.5, RCP6, and RCP8.5,

Blackbody

A blackbody refers to an object that absorbs all incoming electromagnetic radiation and does not reflect any. A blackbody also emits radiation: this emission is temperature-dependent §Peak wavelength is determined by Wien's displacement law

Greenhouse gas

A greenhouse gas is a gas that absorbs and emits radiant energy within the thermal infrared range. Greenhouse gases cause the greenhouse effect.[1] The primary greenhouse gases in Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide and ozone. Without greenhouse gases, the average temperature of Earth's surface would be about −18 °C (0 °F),[2] rather than the present average of 15 °C (59 °F). LIST:•Water vapor (H2O) •Carbon Dioxide (CO2) •Methane (CH4) •Nitrous Oxide (N2O) •Ozone (O3) •Halocarbons, e.g. chlorofluorocarbons (CFC), hydrofluorocarbons (HFC)

Positive/Negative feedback loops

A simple feedback loop: the effect of an initial process causes changes in a second process, which then influences the initial one. A positive feedback loop reinforces the original process.

What are sunspots?

A spot appearing from time to time on the sun's surface, appearing dark by contrast with its surroundings.

What is a blackbody?

A theoretical object that absorbs 100% of the radiation that hits it.

How does atmospheric CO2 change seasonally and over decades, on the Northern and Southern Hemisphere?

After the leaves on the trees drop in the fall, the leaf litter and other dead plant material break downthroughout the winter thanks to microbes: microbes respire and produce CO2•In the spring, leaves return to the trees and photosynthesis increases dramatically, hence CO2 in the atmosphere decreases •There is a much larger amount of land in NH (with huge forested areas in Siberia); SH is dominated by ocean •About a year for the air to mix between NH and SH (weeks to months to mix within each hemisphere)

How is sea ice cover different in the Northern and Southern Hemisphere?

Arctic ocean sea ice is surrounded by land, which limits its maximum extent Seasons in NH & SH are opposite

How do scientists know what carbon dioxide (CO2) concentrations were over the last 800,000 years?

Atmospheric carbon dioxide concentrations in parts per million (ppm) for the past 800,000 years, based on EPICA (ice core) data.

How have temperature and carbon dioxide concentrations changed over the last 100 years?

Averaged over all land and ocean surfaces, temperatures have warmed roughly 1.33°F (0.74ºC) over the last century, CO2 has increased by nearly 100 PPM

Why do we have seasons?

Because of the tilt of the earth's axis.

How do greenhouse gases trap heat?

By allowing visible light and shorter wave radiation to pass through it, but not heat.

How do you know at which wavelength the sun emits its peak radiation?

By looking at radiation levels on the electromagnetic spectrum (ESADK)

Why are some molecules greenhouse gases while others aren't?

Can be called a greenhouse gas if it absorbs heat.

How can we project climate change?

Climate Models are a virtual laboratory and allow us to: §investigate multiple scenarios §study feedback mechanisms and test our understanding §project climate change. Global Climate models §model the flow of mass and energy based on the laws of physics §are highly complex computer programs. §use cells to model oceans and the atmosphere. §currently lack regional resolution, but resolution is increasing rapidly

What is the inverse square law? Why is it important for climate?

Describes the intensity of light at different distances from a light source. Every light source source is different, but the intensity changes in the same way.

Planck feedback

Due to the Stefan-Boltzman law (E=σT4), when Earth warms, the emission of outgoing longwaveradiation increases. Additional longwave emission cools the Earth and hence reduces the warming (a negative, and stabilizing, feedback).

How do the orbital cycles influence climate?

Each of the cycles has a different effect on how much of the sun's energy reaches the earth and when the strongest sunlight occurs.

What happens to the total emissions and the peak of the radiation if the temperature of an object doubles/triples/is reduced by 50%?

Even a small temperature of around 2 degrees C would effect economies, agriculture, infrastructure, and weather patterns.

Wavelength

Forms of electromagnetic radiation like radio waves, light waves or infrared (heat) waves make characteristic patterns as they travel through space. Each wave has a certain shape and length. The distance between peaks (high points) is called wavelength.

What is the difference between the cloud greenhouse effect and the cloud albedo effect?

Greenhouse cloud effect: clouds warm the planet by trapping heat beneath them. Albedo cloud effect: thick clouds have high albedo, thin clouds have low albedo

What type of radiation do greenhouse gases absorb?

Greenhouse gases in the atmosphere (such as water vapor and carbon dioxide) absorb most of the Earth's emitted longwave infrared radiation, which heats the lower atmosphere.

Why is it generally colder on a clear night?

Heat emitted from the earth's surface freely escapes into space resulting in colder temps, if there are clouds, they trap in heat during the night.

What is the difference between low and high clouds?

High clouds are colder, because they are thin and do not reflect very much.

How does albedo affect equilibrium temperature?

Higher albedo = lower eq temperature, lower albedo = warmer temperature

IPCC

Intergovernmental Panel on Climate Change, dedicated to providing the world with an objective view of climate change.

What contributes to sea level change (and what does not)?

Melting Arctic sea ice does NOT contribute to sea rise because it actually has a warming effect due to the lower albedo of ocean water compared to ice. The following things DO affect sea level change: Land ice melting changes to the ocean topography (mid-ocean ridges, etc) Warming of the ocean

Why could melting permafrost increase the greenhouse effect?

Melting can lead to unstable ground §Lakes and pools form as permafrost melts §The cold pools that remain as permafrost melts are starved of oxygen and an ideal home for methanogenic bacteria which release methane (powerful GHG) into the atmosphere

What is the difference between the natural greenhouse effect and the anthropogenic (enhanced) greenhouse effect?

Natural greenhouse effect is due to a number of gases in the atmosphere absorbing heat from the suns surface, anthropogenic greenhouse gases come from human activity

What are the major gaseous components of our atmosphere?

Nitrogen, and Oxygen

What is the difference between "good" stratospheric ozone and "bad" tropospheric ozone?

Ozone occurs in two layers of the atmosphere. The layer closest to the Earth's surface is the troposphere. Here, ground-level or "bad" ozone(troposphic) is an air pollutant that is harmful to breathe and it damages crops, trees and other vegetation. It is a main ingredient of urban smog. The troposphere generally extends to a level about 6 miles up, where it meets the second layer, the stratosphere. The stratosphere or "good" ozone layer extends upward from about 6 to 30 miles and protects life on Earth from the sun's harmful ultraviolet (UV) rays.

CFC, HCFC

Produced by human activities, they are compounds containing chlorine, fluorine, and carbon. Also have been implicated in the destruction of the stratospheric ozone

RCPs

Representative Concentration Pathway is a greenhouse gas concentration trajectory(graph) adopted by the IPCC

What is permafrost?

Rock or soil material that remains below freezing (0ºC) for 2+ years. 20% of landmass is affected by seasonal and permanent permafrost

How can sea level change? How has it changed in the past? How is it changing now?

Sea Level Rise around 0.2 cm per decade last few millennia. 1.7 cm per decade 1901-2010 (tide gauges) . 3.2 cm per decade 1993-2010 WHY: §Ice sheet collapse §Rapid sea level rise §Large meltwater pulses §Sea level rise of over 120 m since Last Glacial Maximum at 21,000 years ago

What is sea ice? How is itdifferent than a glacier?

Sea ice is frozen ocean water, whereas glacial ice is formed on land by the slow accumulation of snow. Sea ice can be up to a few metres thick, although when we are next to it we only see 50cm or so, whereas glacial ice is several kilometres thick in central Antarctica.

Sea ice

Simply frozen ocean water. Forms, grows, and melts in the ocean. Whereas icebergs, glaciers and ice sheets originate on land.

What is the impact of snow cover on albedo?

Since snow is white it has a high albedo meaning it reflects most energy, without the snow the land below has a much lower albedo and will lead to warming of the surface.

Total solar irradiance (also know its value)

The amount of radiation received at the top of the atmosphere from the Sun Value: we receive on average only ~342 W/m2 of radiation

Is the angle of incoming solar radiation important?

The angle of incoming solar radiation influences seasonal temperatures of locations at different latitudes.

What examples of feedback loops did we discuss? How do they work?

The effect of an initial process causes changes in a second process, which then influences the initial one. A positive feedback loop reinforces the original process. Insomnia loop (+)

What is radiation?

The emission of energy as electromagnetic waves or as moving subatomic particles, especially high energy particles which cause ionization.

Greenhouse effect (natural and enhanced)

The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without its atmosphere.[1][2] If a planet's atmosphere contains radiatively active gases (i.e., greenhouse gases) they will radiate energy in all directions. Part of this radiation is directed towards the surface, warming it.[3] The intensity of the downward radiation - that is, the strength of the greenhouse effect - will depend on the atmosphere's temperature and on the amount of greenhouse gases that the atmosphere contains.

Why is there an ozone hole?

The main cause of ozone depletion and the ozone hole is manufactured chemicals, especially manufactured halocarbon refrigerants, solvents, propellants and foam-blowing agents (chlorofluorocarbons (CFCs), HCFCs, halons), referred to as ozone-depleting substances (ODS)

What is the total solar irradiance?

The power per unit area received from the sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument.

What wavelength does the Earth emit radiation at? What about the sun? Why are their radiation spectra different?

The sun has a higher energy output of wavelength but a shorter wavelength (microns). While the earth has a longer wavelength with a shorter energy output.

What is a planet's equilibrium temperature? How do you find it?

Theoretical temperature that a planet would be at when considered simply as if it were a black body being heated only by its parent star. (Earth's is 255 K) EARTH: Earth's average temperature would be near 0°F (or -18°C) instead of the much warmer 59°F (15°C).

Why is sea level change predicted to change over the 21st century?

Thermal expansion and the melting cryosphere will contribute to sea level rise over the 21stcentury

How do seasons change as the orbital cycles change?

Today, the Earth's axis is tilted 23.5 degrees from the plane of its orbit around the sun. But this tilt changes. During a cycle that averages about 40,000 years, the tilt of the axis varies between 22.1 and 24.5 degrees. Because this tilt changes, the seasons as we know them can become exaggerated.

Explain Stefan Boltzmann's law. Why is it important?

Total radiant heat energy emitted from a surge is proportional to the fourth power of its absolute temperature.

What is the greenhouse effect?

Trapping of the sun's warmth in a planet's lower atmosphere, due to the greater transparency of the atmosphere to visible radiation from the sun.

What are the main greenhouse gases in our atmosphere?

Water vapor, Carbox dioxide

What is the atmospheric window?

Wavelengths of the electromagnetic spectrum that can be transmitted through the earth's atmosphere.

How did climate change over the last 12,000 years? The last 1000 years?

average global temperature rose by about 3°C to 8°C, over a period of about 10,000 years. We can link the rises in temperature over the last 200 years to rises in atmospheric CO2 levels. Rises in temperature are now well above the natural cycle of the last 800,000 years.

How much has temperature changed since 1900?

the average global temperature on Earth has increased by about 0.8° Celsius (1.4° Fahrenheit) since 1880. Two-thirds of the warming has occurred since 1975, at a rate of roughly 0.15-0.20°C per decade

Albedo

total fraction of total radiation that is reflected by a given surface high albedo = reflective low albedo = absorbs