METR 12 Midterm Study Guide

[L5] What were the three orbital variations that Milankovitch proposed? (Variations in the earth's orbit)

1. Eccentricity: changes in shape of Earth's orbit around sun (100,000 years) 2. Precession: Wobbling of Earth's axis of rotation (21,000 years) 3. Obliquity: Changes in tilt of Earth's axis (41,000 years)

[L3] What are the five steps of the greenhouse effect?

1. Solar (shortwave) radiation is absorbed by Earth's surface. 2. Earth emits infrared (long wave) radiation. 3. Greenhouse gases absorb most of Earth's outgoing infrared radiation. 4. Greenhouse gases emit infrared radiation in all directions. 5. Earth absorbs downward directed infrared radiation. Result: Warmer surface temperature.

[L5] Name three examples of internal forcing factors.

1. Variations in solar output. 2. Orbital variations. 3. Meteors.

[L5] Name three examples of internal forcing factors.

1. Volcanoes. 2. Plate tectonics. 3. Changes in atmospheric composition.

[L3] What is Earth's actual surface temperature?

15 deg celsius (59 deg F)

[L1] Ice-core data shows us that before the early 1900's, atmospheric CO2 concentrations were never above ____ PPM.

400 ppm

[L4] How do the respective sizes if a CCN, cloud droplet, and raindrop differ?

A CCN is 0.0002 millimeters, cloud droplet is 0.02 millimeters and raindrop is 2 millimeters.

[L5] What is the different between an external and internal forcing factor?

An external forcing factor is the agent of change that is out of the Earth-atmosphere system. Internal forcing factor is the agent of change within the earth atmosphere system itself.

[L1] What are natural and anthropogenic sources of CO2?

Anthropogenic sources: Electric power generation, transportation, industry, commercial and residential usage, agriculture, land use change(deforestation) Natural sources: Volcanoes, Plants (respiration)

[L5] As the amount of sunspots increases, what happens to the amount of energy emitted by the sun?

As sunspots increase, the amount of solar energy increases.

[L1] How much have atmospheric CO2 concentrations changed by from 1958 to present? What are the predictions for concentrations in 2100?

Atmospheric CO2 concentrations have increased from 315.71 ppm in March 1958 to 407.18 ppm in March 2017, a 29.0% rise in 59 years. The increase will continue to 550-970 ppm by 2100, depending on emission scenarios.

[L1] How have atmospheric CO2 concentrations at Mauna Loa changed since observations began in 1958? What is the name of the curve showing changes from 1958 to present?

Atmospheric concentrations of CO2 at Mauna Loa have increased from 315.71 ppm in March 1958 to 407.18 ppm in March 2017, a 29.0% rise in 59 years. The curve showing changes is called the Keeling Curve.

[L4] What does CCN stand for? What are three examples of CCN?

CCN stands for cloud condensation nuclei. Three examples: Dust, salt, and smoke.

[L1] Who was the first person to note a warming trend during the 20th century and associate it with fossil fuel emissions? How large was the warming, and what time period was it over?

Callendar was the first to note of the warming trend and associate it with fossil fuel emissions. (1938) The warming was of 0.2 degrees celsius/ 0.36 fahrenheit from 1890 - 1935.

[L2] What percentage of incoming sunlight is reflected by each planet?

Earth reflects 30% of sunlight from the Sun. Venus reflects 70% of sunlight from the Sun.

[L2] What are the albedos of two planets? How about the abosrptivities?

Earth's albedo is 30%. Venus's albedo is 70%. Earth absorbs 70% of the sunlight that strikes it while Venus absorbs 30%.

[L5] What are glaciers? What causes glaciers to grow? What causes glaciers to decay?

Glaciers are composed of fallen snow. This is compressed into a large, thickened mass of ice over many years. Growth is due to when yearly snowfall is greater than snow melt and decay is when yearly snowfall is less than snowmelt.

[L1] How have global CO2 emissions changed over the past 68 years?

Global CO2 emissions have increased greatly over the past 68 years.

[L2] What is the difference between the terms "greenhouse effect" and "global warming?"

Global Warming is the enhancement of the greenhouse effects. The greenhouse effect is a good thing because it keeps our planet warm.

[L1] How do the terms global warming and climate change differ?

Global Warming is the the warming of the 20th & the 21st centuries associated with anthropogenic activities while Climate Change is changes in the climate of the past, present, and future associated with natural or anthropogenic factors.

[L3] How might global albedo change in the future, overall? Why?

Global albedo is on the decline because of the melting ice caps.

[L5] What is happening to atmospheric concentrations of carbon dioxide and other anthropogenic greenhouse gases over time?

Global carbon dioxide emissions and others have increased greatly over the past 150 years.

[L1] How much did global temperatures increase by from 1917 to 2017? When has most of this warming occurred?

Global temperatures increased by 1.33 degrees celsius (2.39 fahrenheit) from 1917 - 2017. Most of the warming has occurred since the mid 1970's.

[L1] What is the difference between a hypothesis and a theory? (in science)

Hypothesis is a proposed explanation for a phenomenon or some observation. A theory is a logically self-consistent explanation describing the behavior of natural phenomenon.

[L5] How might changing the times of Perihelion and Aphelion affect the strength of the seasons?

If Perihelion occurrence gets pushed up to a later date, the northern hemisphere will have to cope with slightly hotter and shorter summers. (They both could occur during the opposite of the seasons)

[L5] As the earth's tilt increases, what happens to the strength of the seasons? How about as it decreases?

If it decreases - cooler summer, warmer winters. If it increases - warmer summer, colder winters.

[L4] If the number of low clouds increased, how would surface temperatures respond? What about for high clouds? Why?

Low clouds will cool the surface by reflecting incoming sunlight. High clouds will warm the surface by absorbing infrared radiation emitted from the surface and reradiating it back down.

[L4] Understand how sun angle affects brightness and size of beam at the surface.

Lower sun angle, less incoming energy per area. Higher sun angle, more incoming energy per area.

[L1] What are examples of other anthropogenic greenhouse gases?

Methane (CH4), Nitrous Oxide (N2O), and Chlorofluorocarbons (CFC).

[L1] What English and Metric units are used for length? How about temperature?

Miles and Kilometers. Celsius and Fahrenheit.

[L1] What natural occurrence resulted in a global average temperature decrease of 0.2 Celsius from 1991 - 1992?

Mount Pinatubo's eruption resulted in a global average temperature decrease of 0.2 degrees celsius.

[L3] What has to be true for an object or substance to emit radiation? What are examples of objects that emit radiation?

Must have a temperature greater than 0 K emit some type of radiation. Examples are humans, the sun, and the Earth.

[L4] What is the main reason for the astronomical seasons?

Our Earth is tiled and due to the days of the year, the sun shines at either a lower sun angle (less energy) or high sun angle (more energy). Thus, giving us a summer season with more sun hours and winter season with less sun hours. Astronomical seasons are the reasons why we still function up to this day.

[L1] What is proxy data, and what are three examples of it?

Proxy data is reconstruction of temperatures prior to direct measurements. Three examples are ice core isotope data, coral reef isotope data, and tree ring width.

[L3] If there was a sudden removal of all greenhouse gases in the atmosphere, what would happen to Earth's average surface temperature?

Removal of greenhouse gases would decrease downward directed energy; now upward energy lost from surface is greater than downward energy absorbed by surface. As surface cools, radiation emitted by surface (upward) decreases until balance is restored. At this point, cooling stops. It would be very cold planet! -18°C (0°F)

[L1] How are ice core measurements made?

Scientists can reconstruct record of past temperatures by analyzing trapped air bubbles in ice as there is a strong correlation between temperature and isotopic ratio. Snowfall in Antartica falls on previous year's snowfall without melting b/c its so cold. By drilling down from surface of ice sheet, history of chemicals in ice can be obtained.

[L3] What are the respective albedos of various surfaces on Earth, such as snow, water, forest, and desert?

Snow has high albedo. Water, forest, and deserts have low albedos.

[L3] What is solar radiation composed of? In what spectrum does the sun emit most of its radiation?

Solar radiation is composed of shorter wavelengths with higher intensity. Solar radiation is composed of 44% of visible light, 37% of infrared, and 7% ultraviolet. Most of its radiation is in the spectrum of visible light.

[L4] What is a solstice? How many are there per year? When do they occur?

Solstice is days of the year when the sun shines directly overhead 23.5 degrees south or 23.5 deg north at noon. There are two per year: June Solstice (6/21) and December Solstice (12/21)

[L5] What is eccentricity?

The extent to which the Earth's orbit around the sun departs from a perfect circle. It's a dimensionless quantity describing the elliptical shape of a planet's orbit. (The degree)

[L4] On a set day in Northern Hemisphere summer, as one travels farther north, what happens to length of daylight?

The length of daylight increases.

[L5] What is plate tectonics? How can this geologic process affect climate?

The moving of plate tectonics can form mountains which can result to more snowfall and/or volcanoes. This also causes a change in the ocean currents and in turn generates more heat. When these tectonic plates shift, the creation of volcanic eruptions increases the degree of CO2 and sulfur dioxide in the atmosphere.

[L4] What is the net effect of all clouds on climate?

The net effect of clouds on climate is to cool the earth.

[L1] What is the relationship between atmospheric temperature and carbon dioxide (CO2) concentrations over the past 400,000 years?

The relationship between atmospheric temperature and carbon dioxide concentrations are very similar, judging by the similarities in increases and decreases with CO2 concentrations and temperature change.

[L2] What could account for the difference between the actual planetary temperatures and those predicted based on absorption of sunlight from outer space?

The respective atmospheres of the Earth and Venus.

[L1] How has the sea level changed over the 20th century? What are the two main causes of the change?

The sea level is rising. The two main causes are melting of continental ice and thermal expansion.

[L1] What is happening to snow at the top of Mt. Kilimanjaro, the only place on the continent of Africa covered by snow year round?

The snow cover is declining.

[L5] What is the solar cycle? How long of a period is it over? What is meant by solar maximum and solar minimum?

The solar cycle is the amount of magnetic flux that rises up to the sun's surface varies with time in a cycle. The period is an 11-year cycle. At maximum, the sun is full of sunspots and solar flares erupt. Whereas minimum it is rare to see sunspots.

[L4] On an equinox, how does incoming solar radiation per area at the equator differ from that at the poles?

The solar radiation is more concentrated at the equator than the poles due to the sun angle.

[L4] What two factors influence incoming solar energy per area each day?

The sun's angle of incidence & length of time the sun shines each day.

[L1] When did the warmest year of the modern meteorological (instrumental) record occur? When have the 10 warmest years occurred?

The warmest year was 2016. The past 9/10 warmest years occurred in the last 15 years.

[L4] What would happen to length of daylight and the sun's path across the sky each day of the year if the Earth had no tilt on its axis?

There would be 12 hours of daylight and 12 hours of night. The sun's path would remain the same.

[L5] What climatic event did the Maunder Minimum coincide with?term-97

This coincided with a cool climatic period in Europe and North America called, "Little Ice Age."

[L1] Which two countries emit the most CO2 globally? What are the recent emission trends?

USA and China. In 2006, China overtook the USA as the world's largest emitter of CO2, however the US is still much higher in emissions per capita. (person)

[L2] Based solely on position from sun, which planet would be warmer? Why? What would the average temperatures be if the planets absorbed all incoming sunlight?

Venus because the sunlight striking Venus is 93% stronger than the sunlight striking Earth.

[L2] How do Earth and Venus' atmospheres differ, both in concentration and total mass?

Venus has a much more massive atmosphere and is mostly CO2. The mass of CO2 in Venus's atmosphere is almost 100 times as great as the TOTAL mass of Earth's atmosphere.

[L2] How do the greenhouse effects of each planet's atmosphere differ?

Venus's atmosphere has 25,000 times as much ass of greenhouse gases as Earth's.

[L5] What are three internal factors on climate?

Volcanoes, global warming, human activities that affect albedo and atmospheric composition. Melting of ice and snow decreases earth's albedo leading to less amount of solar energy absorbed by the planet.

[L3] As an object warms, what happens to the general wavelength of radiation it emits?

Warmer objects emit a higher proportion of their energy at short wavelengths than colder objects.

[L3] As an object warms, what happens to the total amount of radiation it emits?

Warmer objects emit more intensely than colder objects.

[L3] What happens to most shortwave radiation after it enters the atmosphere?

most absorption of shortwave radiation occurs at the Earth's surface.

[L2] What is the source of all energy for these two planets?

the Sun.

[L1] What is the physical meaning of temperature?

the measure of the average kinetic energy in a substance. (how fast the atoms/molecules are moving)

[L2] What are three factors that might be considered in determining average surface temperatures of Earth and Venus?

which planet is closer to the Sun, which planet is more reflective, and which planet has a larger ability to absorb and retain solar energy.

[L5] What is obliquity?

The angle at which the Earth tilts varies. These axial variations are referred to as a planet's obliquity.

[L4] What are the two ways in which clouds can interact with climate? Understand the mechanisms.

1. Albedo effect-cooling. Clouds reflect incoming solar radiation. Cloud droplet size and total water content determine overall reflection. 2. Greenhouse effect-warming. Clouds are good absorbers (& emitters) of long wave (infrared) radiation.

[L5] Can evidence of orbital variations be found when examining ice core temperature data?

Yes.

[L3] Do greenhouse gases interact strongly with UV and visible radiation? What about certain wavelengths of infrared (long wave) radiation?

Absorption of shortwave radiation by atmospheric gas molecules is fairly weak. Most absorption of shortwave radiation occurs at the Earth's surface. Most atmospheric gases do not interact strongly with long wave radiation. However, greenhouse gas molecules absorb certain wavelengths of Earth's emitted long wave (infrared) radiation.

[L2] What is albedo? How is it different for a light object compared to a dark object?

Albedo is the fraction of light reflected by an object or surface. Light objects have higher albedos than darker objects.

[L1] What is the most anthropogenic greenhouse gas? What makes it so important?

Carbon Dioxide (CO2). It is the most important because it has the highest concentration and largest impact on climate. It has an approximate lifetime of 120 years thus current emissions will affect climate far into the future.

[L3] In 2005 (12 years ago), the majority of global greenhouse emissions came from what gas?

Carbon Dioxide.

[L3] What are the 4 most abundant anthropogenic greenhouse gases? How do they differ in terms of concentration, atmospheric lifetime, and warming potential?

Carbon dioxide, Methane, Nitrous Oxide, and Carbon monoxide. -CO2 has the concentration of 380,000 parts per billion, 120 years in Earth's atmosphere, and warming potential of 1. -CH4 has the concentration of 1,850 parts per billion, 12 years, and warming potential of 25. -N2O has the concentration of 324 parts per billion, 114 years, and warming potential of 298. -CO has the concentration of 130, .25 years, and warming potential of 2.

[L4] Over the course of one year, when is Earth closest to the sun? What is the name of this point in Earth's orbit/revolution around the sun?

Closest annual distance to the sun occurs at Perihelion on January 2-5 at 147 million km (91.5 million miles)

[L4] In terms of temperature, how do cloudy days differ from clear days? What about for cloudy nights versus clear nights?

Cloudy days are colder during the day and have warmer evenings, whereas clear days are warmer during the day, but have colder evenings.

[L3] What are three methods of heat transfer in the atmosphere? Be able to differentiate between each one. Which one is the dominant way energy is transferred from the Sun to the Earth?

Conduction is the transfer of energy by collisions between neighboring molecules without any net external motion. Convection is the transfer of energy by mass motions within a fluid (water,air), resulting in actual transport of energy. Radiation is the propagation of electromagnetic waves through space. The main way energy is transferred from the Sun to the Earth is electromagnetic radiation.

[L2] Which planet absorbs more total sunlight: Earth or Venus? Which should be warmer, taking into account distance from sun and albedo?

Earth absorbs more energy than Venus, thus if a planet's surface temperature was determined by the amount of solar radiation absorbed, Earth would be warmer than Venus.

[L1] When did direct measurements of temperature throughout the world become available?

Direct measures of temperature from weather stations around the globe have only been available since the late 1800's.

[L4] Over the course of one year, when is Earth farthest from the sun? What is the name of this point in Earth's orbit/revolution around the sun?

During summer, July 3-6. This occurs at Aphelion at 152 million km(94.5 million miles)

[L4] At what angle is the Earth tilted on its axis, with respect to a vertical line through the plane of its orbit around the sun?

Earth has seasons because it is tilted 23.5 deg relative to our orbital plane. (called obliquity)

[L2] What are the actual average surface temperatures of the two planets?

Earth's mean surface temperature is about 15 degrees celsius / 59 degrees fahrenheit while Venus's mean surface temperature is about 480 degrees celsius / 896 degrees fahrenheit.

[L3] What is electromagnetic radiation composed of? How fast does it travel?

Electromagnetic radiation composed of mainly photons, meaning packets of energy. They travel through space at the speed of light in a vacuum.

[L4] What is meant by evaporation, condensation, and precipitation?

Evaporation is the process where a liquid changes into a gas, condensation is where a gas changes into a liquid, and precipitation is any liquid or solid water that falls from the atmosphere to the ground (ex: rain).

[L3] Why are greenhouse gases important, with respect to long wave radiation?

Greenhouse gas molecules absorb certain wavelengths of Earth's emitted long wave (infrared) radiation. Removal of GHG would decrease downward directed energy; now upward energy lost from surface is greater than downward energy absorbed by surface.

[L2] How does the strength of the greenhouse effect affect climate?

Greenhouse gases play an important role in determining surface temperatures and changes in the gases can increase/decrease surface temperatures.

[L4] Familiarize yourself with cloud names and appearances.

HIGH CLOUDS: Cirrocumulus - mackerel sky Cirrostratus- Halo around sun Cirrus- Thin and whispy strands MIDDLE CLOUDS: Altocumulus: rolls in layers or many patches Altostratus: Sun dimly visible LOW CLOUDS: Stratus: horizontal layering Stratocumulus: large dark round masses VERTICAL DEVELOPMENT: Cumulus: puffy and flat base Cumulonimbus: dense, towering vertical cloud associated with thunderstorms(heavier rain, doesn't last very long) Nimbostratus: Darker thicker stratus looking clouds (lasts awhile and covers entire sky)

[L4] What are the four main categories of clouds? What two clouds produce rainfall? What are clouds made of, and how does the category tell you about composition?

High (cirr-), Middle (alto-), Low (Strat-), and Vertical development (Cumu-). The Nimbostratus (lasts awhile) and Cumulonimbus (heavier, doesn't last) produce rainfall. Clouds are made of cloud droplets(strat-), ice crystals (cirr-), and both (alto-,cumu-).

[L4] What are the relative strengths of the albedo and greenhouse effects for high clouds? What about for low clouds?

High clouds are fair/poor reflector of solar radiation and warms the surface. Low clouds (dark, thick) are excellent reflector of solar radiation and they're good absorber/emitter of infrared radiation (cools surface.)

[L4] What does insolation stand for?

Incoming solar radiation.

[L1] How did the average Northern Hemisphere temperatures change over the 20th century, according to the work of Mann et. al?

Increase of 0.6 degrees celsius (1.1 degrees fahrenheit) from 1900 - 1998.

[L3] What type of radiation are you emitting right now?

Infrared Radiation.

[L1] What does IPCC stand for? How does this inter-governmental organization interpret the observed increase in global temperatures, and what do they say about the future?

Intergovernmental Panel on Climate Change. The warming of the climate system is unequivocal. Further global warming is already unavoidable due to past human activity and a major international effort is required to mitigate the impact. Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.

[L5] How can volcanic eruptions cool the Earth's surface? How can they warm the Earth's surface? On average, is the net effect of volcanic eruptions a cooling or warming?

It forms aerosols, sulfur dioxide, and fine particles that reflect sunlight, contributing to global cooling. Volcanoes also release CO2 which can contribute to warming the Earth. The net effect of volcanic eruptions is a cooling.

[L3] What is meant by "Earth's energy balance?"

It is conservation of energy, basically what comes in must come out. Energy entering top of atmosphere = Energy leaving top of atmosphere. Energy gained by atmosphere = Energy lost by atmosphere. Energy gained by Earth's surface = Energy lost by Earth's surface.

[L4] What is an equinox? How many are there per year? When do they occur?

It is days of the year when the sun shines directly overhead the equator at noon. There are two: the vernal equinox (spring) and autumnal equinox. (In March & September)

[L5] What was the Maunder Minimum? When did it occur?

It was an absence of sunspots and they became exceedingly rare. This was well observed from 1645 to 1715.

[L3] What are the three fates of solar radiation when it enters the top of the atmosphere? Where an how can each of these processes occur?

It will either scatter(reflected away), absorbed, or be transmitted. -Scattering happens when solar radiation is reflected by gases, aerosols, or clouds in the atmosphere (earth's surface). -Absorption of solar radiation occurs by gases and clouds in the atmosphere (earth's surface). -Transmittance happens when solar radiation passes through atmosphere to surface, where it will be absorbed or reflected.

[L4] What is the sub solar point?

Latitude at which the sun is directly overhead at noon on a particular day.

[L3] What kind of radiation do planets emit? How is this radiation different from solar radiation?

Planets mainly emit infrared radiation. Radiation emitted by planets occur mainly at wavelengths longer than those contained in solar radiation.

[L5] What is precession? How does it affect the times of the calendar year when Perihelion and Aphelion occur?

Precession is the wobbling of the earth's axis of rotation. It pushes perihelion to occur at a later date and can cause a profound difference in the severity of the seasons.

[L5] What causes sunspots? Why do they appear darker than their surroundings?

Sunspots are caused by intense fluctuations in the magnetic field of sun. They appear darker due to lower intensity of radiation emitted.

[L3] Be able to name different types of radiation, and understand how they differ in terms of wavelength?

Terrestrial/longwave radiation. Planets emit mainly infrared radiation that occurs at wavelengths longer than solar radiation. Solar radiation shortwave.

[L4] In which Hemisphere is most of the world's land located?

The Northern hemisphere currently has about 65% of Earth's landmass.

[L4] How might the effect of changing distance to the sun affect the strength of the seasons in Southern Hemisphere, compared to the Northern Hemisphere?

The Southern Hemisphere has less amount of land area than the Northern Hemisphere, so greater seasonality is negated.

[L1] How has the extent of Arctic sea ice at the end of summer changed from 1979 to present? When have the years with the 10 lowest extents occurred?

The Summer Sea Ice extent has been on a decline since 1979. The 10 lowest years have occurred in the past decade.

[L3] Which emits more intense radiation: Earth or Sun? Why?

The Sun because warmer objects emit more intensely and at a higher proportion of their energy in short wavelengths.

[L1] How does water vapor (H2Ov) differ from the anthropogenic greenhouse gases? Is it responsible for the observed global warming? Can it enhance the warming once it's happened?

Water vapor is a natural greenhouse and is highly variable in concentration. It is not directly responsible for global warming but can amplify it's effects through feedback loops.

[L1] What is the difference between weather and climate?

Weather is the state of the atmosphere at a particular time & place, being highly variable and changing day-to-day. Climate is the accumulation of daily or seasonal weather events over a longer time period. It represents a long-term average of weather, but must include extremes