Topic 04 Greenhouse Effect

On average, most of insolation is___________________

transmitted through to the surface of the Earth; 54% of insolation is transmitted through the atmosphere, although 7%, again on average, is then reflected off the Earth's surface.

Feeling sunburn?

ultraviolet light

What type of ultraviolet radiation penetrate surface

minute amounts of UVB and UVA oxygen and ozone absorb the rest

When did size of earth's heat reservoir change

Until 1700 the reservoir size stayed the same since the last ice age. We have been able to track net energy imbalance since 2005, which has gradually increased with some oscillations due to climate trends.

The highest intensity of solar radiation is reached in this range of wavelengths

Visible Light; Spectral irradiance reaches values of almost 2.0 Watts per square meter in the blue range of visible wavelengths

A beam of solar radiation moves through an atmospheric gas molecule completely unimpeded and hits the Earth's surface. The beam is said to have been ____________________

. transmitted

What is the percent breakdown of our atmosphere

21 oxygen, 78 nitrogen, .9 argon

When it comes to insolation, three important numbers are 30%, 47%, and 23%. What do they measure?

30% of insolation is reflected 23% of insolation is absorbed by the atmosphere 47% of insolation is absorbed by the Earth's surface; Keep in mind, and this is important, that these percentages are AVERAGED across the atmosphere and surface of the planet.

What percent of heat in atmosphere is held onto by BIG 6 gases

99.9%

Define radiation

Heat emitted from the Earth's surface in the form of wave energy

This type of radiation makes up the largest range of wavelengths in sunlight

Infrared

define solar spectral irradiance

Solar irradiance is the power per unit area received from the Sun in the form of electromagnetic radiation as measured in the wavelength range of the measuring instrument.

What 4 things can happen to insolation, which account for why the amount of radiation that arrives at top of atmosphere differs from what arrives at surface of earth?

TRAS: Transmission, Reflection, Absorption, Scattering

The energy absorbed by the Earth's surface is returned as heat to the atmosphere via what three things?

evaporation, conduction, and radiation

The Earth of today gains on average around 0.87 Watts of heat per square meter MORE than it is losing back to space. This observable and measurable phenomenon is known as.....

global warming

Define evaporation

heat absorbed by water molecules causes them to turn into a gaseous phase and rise into atmosphere

Wavelengths of visible light?

~380nm to ~740nm

There are ____ major greenhouse gases, responsible for absorbing and trapping heat in our atmosphere.

6; they are methane, carbon dioxide, water vapor, nitrous oxides, tropospheric ozone, and chlorofluorocarbons

Insolation that is reflected by the surface of the Earth essentially travels out through the atmosphere back to space without being absorbed by the atmosphere. Why?

All insolation that reaches the Earth's surface has already been "stripped" of most of the wavelengths readily absorbed by atmmospheric gas molecules, so the outgoing reflected insolation is essentially invisible to gas molecules. However, the details are complicated because aerosols, for one, also block reflected sunlight, and some short infrared wavelengths are only partially absorbed by the atmosphere on their way through it. Nevertheless, on average 7% of sunlight leaves into space because of reflection from the Earth's surface.

True or False? UV radiation that is absorbed by the Earth's surface is, in part, reradiated back to the atmosphere as UV radiation.

FALSE The only way that absorbed heat is transferred AS RADIATION to the atmosphere is via infrared. Any insolation in the UV and Visible Range that is absorbed by the Earth is converted into infrared radiation.

True or False? Hot springs, geysers, and volcanic eruptions have a significant direct effect on the heat content of our atmosphere.

FALSE; Without the sun, our planet would be in perpetual deep freeze because overall the Earth does not produce enough heat "to keep itself warm".

The following three gases make up 99.9% of the air in the Earth's atmosphere (click all that apply)

argon, nitrogen, oxygen; All other gases are present as parts per million or parts per billion, rather than percentages.

Asphalt and water share almost the same albedo (5-6%). In other words, they absorb roughly the same amount of insolation and reflect only very little insolation. Yet, after a day in the hot sun, asphalt gets really hot, whereas a similarly thick layer of water does not. Why?

asphalt has a lower heat capacity than water - its temperature rapidly rises with increased heat absorption, whereas that of water does not. Water is an excellent absorber of heat and has the almost uncanny ability to absorb a LOT of it without also raising its overall temperature

On average, most reflection of insolation takes place....

at the top of the atmosphere; Again, this is an average, the percentage will be low nearest the equator and highest at higher latitudes (can you explain why?).

Historically, the atmosphere has lost the same amount of heat that it also gained at any moment in time. This is called heat equilibrium. Why then has the atmosphere not stayed freezing cold?

because after the last Ice Age, the Earth reached a certain stable level of greenhouse gases in its atmosphere. Until about 1750, these gases were at full heat capacity. Any heat added to them, would also immediately be lost to space, however, they always hold on to heat in the process; During the time when GHGs concentration were increasing, following the Ice Age, the Earth would have been losing less heat to space than it was gaining - but only until ALL of the GHGs were at full heat capacity.

what is committed warming

describes how even if we cut all GHG our planet would still heat by 1C because there are GHG in atmosphere that are not at full capacity.

The radiation absorbed by the Earth's heat is effectively converted into.......

higher wavelengths, notably long-wave infrared; The Earth's "Outgoing Window of Radiation" consists entirely of long-wave infrared radiation.

Feeling heat?

infrared

In general, greenhouse gases are collectively most effective at absorbing which wavelengths?

infrared; Only ozone and oxygen effectively absorb UV radiation, and visible light only experiences slight absorption in the red bands by water vapor, oxygen, and ozone. MOST of the absorption of GHGs takes place in the infrared

Heat emitted by atmospheric gas molecules (after they absorbed it) is solely in the __________________ range of the spectrum

infrared; The only absorbed radiation that escapes the top of the atmosphere is in the form of infrared wavelengths

The sunlight that arrives at the top of the atmosphere is referred to as ________________________ by atmospheric scientists.

insolation. stands for INcoming SOLar radIATION.

What are the big 6 gases?

methane, water vapor, co2, ozone, nitrous oxide, CFC (chloroflourocarbon)

Which of the following gases most effectively absorb infrared wavelength of around 10 microns?

oxygen and ozone

Which of the following gases most effectively absorb incoming solar radiation in the UV range of the spectrum? (Look at the graph labelled "Absorption of Radiation by Atmospheric Gases" in your lecture slides)

ozone and oxygen; Most of this absorption takes place by stratospheric ozone and oxygen (rather than by the same molecules in the troposphere).

Although some aerosols are able to absorb heat for short periods of time, the main role aerosols play in the greenhouse effect is as __________________________

reflectors of incoming solar radiation; Many aerosols "block" sunlight and therefore have a cooling effect (albeit short-lived as most particles fall out of the atmosphere rather quickly). Aerosols DO play an important role as raindrop precipitators BUT this has little to do with the greenhouse effect.

A beam of sunlight hits an atmospheric gas molecule and the radiation splits, sending some rays back to space, and others towards the surface. The beam of sunlight is said to have been__________________

scattered

Define conduction

some of the Earth's absorbed heat is directly transferred to air molecules in contact with the surface

Which aerosols absorb heat?

sulfate, organic carbon

List major 7 aerosols

volcanic ash, sea salt crystals, pollen and spores, soot, mineral dust, sulfates, organic carbon (from burning fossil fuels)

The albedo of a surface is a measure of its reflectivity. Which of the following surface has a low albedo and therefore ABSORBS most of the insolation.

water

Which greenhouse gas effectively absorbs the greatest range of sunlight's wavelengths?

water vapor; Water vapor is an effective absorber of infrared radiation throughout much of the sun's spectrum

Carbon dioxide effectively absorbs the following wavelengths?

wavelengths between approximately 14 and 19 microns; You do not need to know or memorize these specific ranges BUT you should know how to read the graph provided in lecture to answer such questions.

Wavelengths between 0.3 and 2.3 microns are collectively known as......

wavelengths that make up the "window of incoming solar radiation"; These wavelengths of insolation experience the least total amount of absorption by the atmosphere and make up a significant portion of wavelengths that travel all the way to the Earth's surface.