Outgoing longwave radiation

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Spectral intensity of sunlight (average at top of atmosphere) and thermal radiation emitted by Earth's surface. Sun-Earth Logarithmic Spectrums with Accurate Scaling.svg
Spectral intensity of sunlight (average at top of atmosphere) and thermal radiation emitted by Earth's surface.

In climate science, longwave radiation (LWR) is electromagnetic thermal radiation emitted by Earth's surface, atmosphere, and clouds. It may also be referred to as terrestrial radiation. This radiation is in the infrared portion of the spectrum, but is distinct from the shortwave (SW) near-infrared radiation found in sunlight. [1] :2251

Contents

Outgoing longwave radiation (OLR) is the longwave radiation emitted to space from the top of Earth's atmosphere. [1] :2241 It may also be referred to as emitted terrestrial radiation. Outgoing longwave radiation plays an important role in planetary cooling.

Longwave radiation generally spans wavelengths ranging from 3–100 micrometres (μm). A cutoff of 4 μm is sometimes used to differentiate sunlight from longwave radiation. Less than 1% of sunlight has wavelengths greater than 4 μm. Over 99% of outgoing longwave radiation has wavelengths between 4 μm and 100 μm. [2]

The flux of energy transported by outgoing longwave radiation is typically measured in units of watts per metre squared (W⋅m−2). In the case of global energy flux, the W/m2 value is obtained by dividing the total energy flow over the surface of the globe (measured in watts) by the surface area of the Earth, 5.1×1014 m2 (5.1×108 km2; 2.0×108 sq mi). [3]

Emitting outgoing longwave radiation is the only way Earth loses energy to space, i.e., the only way the planet cools itself. [4] Radiative heating from absorbed sunlight, and radiative cooling to space via OLR power the heat engine that drives atmospheric dynamics. [5]

The balance between OLR (energy lost) and incoming solar shortwave radiation (energy gained) determines whether the Earth is experiencing global heating or cooling (see Earth's energy budget). [6]

Planetary energy balance

The growth in Earth's energy imbalance from satellite and in situ measurements (2005-2019). A rate of +1.0 W/m summed over the planet's surface equates to a continuous heat uptake of about 500 terawatts (~0.3% of the incident solar radiation). Earth's heating rate since 2005.jpg
The growth in Earth's energy imbalance from satellite and in situ measurements (2005–2019). A rate of +1.0 W/m summed over the planet's surface equates to a continuous heat uptake of about 500  terawatts (~0.3% of the incident solar radiation).

Outgoing longwave radiation (OLR) constitutes a critical component of Earth's energy budget. [9]

The principle of conservation of energy says that energy cannot appear or disappear. Thus, any energy that enters a system but does not leave must be retained within the system. So, the amount of energy retained on Earth (in Earth's climate system) is governed by an equation:

[change in Earth's energy] = [energy arriving][energy leaving].

Energy arrives in the form of absorbed solar radiation (ASR). Energy leaves as outgoing longwave radiation (OLR). Thus, the rate of change in the energy in Earth's climate system is given by Earth's energy imbalance (EEI):

.

When energy is arriving at a higher rate than it leaves (i.e., ASR > OLR, so that EEI is positive), the amount of energy in Earth's climate increases. Temperature is a measure of the amount of thermal energy in matter. So, under these circumstances, temperatures tend to increase overall (though temperatures might decrease in some places as the distribution of energy changes). As temperatures increase, the amount of thermal radiation emitted also increases, leading to more outgoing longwave radiation (OLR), and a smaller energy imbalance (EEI). [10]

Similarly, if energy arrives at a lower rate than it leaves (i.e., ASR < OLR, so than EEI is negative), the amount of energy in Earth's climate decreases, and temperatures tend to decrease overall. As temperatures decrease, OLR decreases, making the imbalance closer to zero. [10]

In this fashion, a planet naturally constantly adjusts its temperature so as to keep the energy imbalance small. If there is more solar radiation absorbed than OLR emitted, the planet will heat up. If there is more OLR than absorbed solar radiation the planet will cool. In both cases, the temperature change works to shift the energy imbalance towards zero. When the energy imbalance is zero, a planet is said to be in radiative equilibrium . Planets natural tend to a state of approximate radiative equilibrium. [10]

In recent decades, energy has been measured to be arriving on Earth at a higher rate than it leaves, corresponding to planetary warming. The energy imbalance has been increasing. [7] [8] It can take decades to centuries for oceans to warm and planetary temperature to shift sufficiently to compensate for an energy imbalance. [11]

Emission

Thermal radiation is emitted by nearly all matter, in proportion to the fourth power of its absolute temperature.

In particular, the emitted energy flux, (measured in W/m2) is given by the Stefan–Boltzmann law for non-blackbody matter: [12]

where is the absolute temperature, is the Stefan–Boltzmann constant, and is the emissivity. The emissivity is a value between zero and one which indicates how much less radiation is emitted compared to what a perfect blackbody would emit.

Surface

The emissivity of Earth's surface has been measured to be in the range 0.65 to 0.99 (based on observations in the 8-13 micron wavelength range) with the lowest values being for barren desert regions. The emissivity is mostly above 0.9, and the global average surface emissivity is estimated to be around 0.95. [13] [14]

Atmosphere

The most common gases in air (i.e., nitrogen, oxygen, and argon) have a negligible ability to absorb or emit longwave thermal radiation. Consequently, the ability of air to absorb and emit longwave radiation is determined by the concentration of trace gases like water vapor and carbon dioxide. [15]

According to Kirchhoff's law of thermal radiation, the emissivity of matter is always equal to its absorptivity, at a given wavelength. [12] At some wavelengths, greenhouse gases absorb 100% of the longwave radiation emitted by the surface. [16] So, at those wavelengths, the emissivity of the atmosphere is 1 and the atmosphere emits thermal radiation much like an ideal blackbody would. However, this applies only at wavelengths where the atmosphere fully absorbs longwave radiation.[ citation needed ]

Although greenhouse gases in air have a high emissivity at some wavelengths, this does not necessarily correspond to a high rate of thermal radiation being emitted to space. This is because the atmosphere is generally much colder than the surface, and the rate at which longwave radiation is emitted scales as the fourth power of temperature. Thus, the higher the altitude at which longwave radiation is emitted, the lower its intensity. [17]

Atmospheric absorption

The atmosphere is relatively transparent to solar radiation, but it is nearly opaque to longwave radiation. [18] The atmosphere typically absorbs most of the longwave radiation emitted by the surface. [19] Absorption of longwave radiation prevents that radiation from reaching space.

At wavelengths where the atmosphere absorbs surface radiation, some portion of the radiation that was absorbed is replaced by a lesser amount of thermal radiation emitted by the atmosphere at a higher altitude. [17]

When absorbed, the energy transmitted by this radiation is transferred to the substance that absorbed it. [18] However, overall, greenhouse gases in the troposphere emit more thermal radiation than they absorb, so longwave radiative heat transfer has a net cooling effect on air. [20] [21] :139

Atmospheric window

Assuming no cloud cover, most of the surface emissions that reach space do so through the atmospheric window. The atmospheric window is a region of the electromagnetic wavelength spectrum between 8 and 11 μm where the atmosphere does not absorb longwave radiation (except for the ozone band between 9.6 and 9.8 μm). [19]

Gases

Greenhouse gases in the atmosphere are responsible for a majority of the absorption of longwave radiation in the atmosphere. The most important of these gases are water vapor, carbon dioxide, methane, and ozone. [22]

The absorption of longwave radiation by gases depends on the specific absorption bands of the gases in the atmosphere. [19] The specific absorption bands are determined by their molecular structure and energy levels. Each type of greenhouse gas has a unique group of absorption bands that correspond to particular wavelengths of radiation that the gas can absorb.[ citation needed ]

Clouds

The OLR balance is affected by clouds, dust, and aerosols in the atmosphere. Clouds tend to block penetration of upwelling longwave radiation, causing a lower flux of long-wave radiation penetrating to higher altitudes. [23] Clouds are effective at absorbing and scattering longwave radiation, and therefore reduce the amount of outgoing longwave radiation.

Clouds have both cooling and warming effects. They have a cooling effect insofar as they reflect sunlight (as measured by cloud albedo), and a warming effect, insofar as they absorb longwave radiation. For low clouds, the reflection of solar radiation is the larger effect; so, these clouds cool the Earth. In contrast, for high thin clouds in cold air, the absorption of longwave radiation is the more significant effect; so these clouds warm the planet. [24]

Details

The interaction between emitted longwave radiation and the atmosphere is complicated due to the factors that affect absorption. The path of the radiation in the atmosphere also determines radiative absorption: longer paths through the atmosphere result in greater absorption because of the cumulative absorption by many layers of gas. Lastly, the temperature and altitude of the absorbing gas also affect its absorption of longwave radiation.[ citation needed ]

OLR is affected by Earth's surface skin temperature (i.e, the temperature of the top layer of the surface), skin surface emissivity, atmospheric temperature, water vapor profile, and cloud cover. [9]

Day and night

The net all-wave radiation is dominated by longwave radiation during the night and in the polar regions. [25] While there is no absorbed solar radiation during the night, terrestrial radiation continues to be emitted, primarily as a result of solar energy absorbed during the day.

Relationship to greenhouse effect

Outgoing radiation and greenhouse effect as a function of frequency. The greenhouse effect is visible as the area of the upper red area, and the greenhouse effect associated with CO2 is directly visible as the large dip near the center of the OLR spectrum. Spectral Greenhouse Effect.png
Outgoing radiation and greenhouse effect as a function of frequency. The greenhouse effect is visible as the area of the upper red area, and the greenhouse effect associated with CO2 is directly visible as the large dip near the center of the OLR spectrum.

The reduction of the outgoing longwave radiation (OLR), relative to longwave radiation emitted by the surface, is at the heart of the greenhouse effect. [27]

More specifically, the greenhouse effect may be defined quantitatively as the amount of longwave radiation emitted by the surface that does not reach space. On Earth as of 2015, about 398 W/m2 of longwave radiation was emitted by the surface, while OLR, the amount reaching space, was 239 W/m2. Thus, the greenhouse effect was 398−239 = 159 W/m2, or 159/398 = 40% of surface emissions, not reaching space. [28] :968,934 [29] [30]

Effect of increasing greenhouse gases

When the concentration of a greenhouse gas (such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and water vapor (H2O) and is increased, this has a number of effects. At a given wavelength

The size of the reduction in OLR will vary by wavelength. Even if OLR does not decrease at certain wavelengths (e.g., because 100% of surface emissions are absorbed and the emission altitude is in the stratosphere), increased greenhouse gas concentration can still lead to significant reductions in OLR at other wavelengths where absorption is weaker. [31]

When OLR decreases, this leads to an energy imbalance, with energy received being greater than energy lost, causing a warming effect. Therefore, an increase in the concentrations of greenhouse gases causes energy to accumulate in Earth's climate system, contributing to global warming. [31]

Surface budget fallacy

If the absorptivity of the gas is high and the gas is present in a high enough concentration, the absorption at certain wavelengths becomes saturated. [18] This means there is enough gas present to completely absorb the radiated energy at that wavelength before the upper atmosphere is reached.[ citation needed ]

It is sometimes incorrectly argued that this means an increase in the concentration of this gas will have no additional effect on the planet's energy budget. This argument neglects the fact that outgoing longwave radiation is determined not only by the amount of surface radiation that is absorbed, but also by the altitude (and temperature) at which longwave radiation is emitted to space. Even if 100% of surface emissions are absorbed at a given wavelength, the OLR at that wavelength can still be reduced by increased greenhouse gas concentration, since the increased concentration leads to the atmosphere emitting longwave radiation to space from a higher altitude. If the air at that higher altitude is colder (as is true throughout the troposphere), then thermal emissions to space will be reduced, decreasing OLR. [31] :413

False conclusions about the implications of absorption being "saturated" are examples of the surface budget fallacy, i.e., erroneous reasoning that results from focusing on energy exchange at the surface, instead of focusing on the top-of-atmosphere (TOA) energy balance. [31] :413

Measurements

Example wavenumber spectrum of Earth's infrared emissions (400-1600 cm ) measured by IRIS on Nimbus 4 in year 1970. Nimbus 4 IRIS OLR 1970.png
Example wavenumber spectrum of Earth's infrared emissions (400-1600 cm ) measured by IRIS on Nimbus 4 in year 1970.

Measurements of outgoing longwave radiation at the top of the atmosphere and of longwave radiation back towards the surface are important to understand how much energy is retained in Earth's climate system: for example, how thermal radiation cools and warms the surface, and how this energy is distributed to affect the development of clouds. Observing this radiative flux from a surface also provides a practical way of assessing surface temperatures on both local and global scales. [33] This energy distribution is what drives atmospheric thermodynamics.

OLR

Outgoing long-wave radiation (OLR) has been monitored and reported since 1970 by a progression of satellite missions and instruments.

Surface LW radiation

Longwave radiation at the surface (both outward and inward) is mainly measured by pyrgeometers. A most notable ground-based network for monitoring surface long-wave radiation is the Baseline Surface Radiation Network (BSRN), which provides crucial well-calibrated measurements for studying global dimming and brightening. [38]

Data

Data on surface longwave radiation and OLR is available from a number of sources including:

OLR calculation and simulation

Simulated wavenumber spectrum of the Earth's outgoing longwave radiation (OLR) using ARTS. In addition the black-body radiation for a body at surface temperature Ts and at tropopause temperature Tmin is shown. Spectral OLR.png
Simulated wavenumber spectrum of the Earth's outgoing longwave radiation (OLR) using ARTS. In addition the black-body radiation for a body at surface temperature Ts and at tropopause temperature Tmin is shown.
Simulated wavelength spectrum of Earth's OLR under clear-sky conditions using MODTRAN. IR emission in current greenhouse levels.png
Simulated wavelength spectrum of Earth's OLR under clear-sky conditions using MODTRAN.

Many applications call for calculation of long-wave radiation quantities. Local radiative cooling by outgoing longwave radiation, suppression of radiative cooling (by downwelling longwave radiation cancelling out energy transfer by upwelling longwave radiation), and radiative heating through incoming solar radiation drive the temperature and dynamics of different parts of the atmosphere.[ citation needed ]

By using the radiance measured from a particular direction by an instrument, atmospheric properties (like temperature or humidity) can be inversely inferred. Calculations of these quantities solve the radiative transfer equations that describe radiation in the atmosphere. Usually the solution is done numerically by atmospheric radiative transfer codes adapted to the specific problem.

Another common approach is to estimate values using surface temperature and emissivity, then compare to satellite top-of-atmosphere radiance or brightness temperature. [25]

There are online interactive tools that allow one to see the spectrum of outgoing longwave radiation that is predicted to reach space under various atmospheric conditions. [41]

See also

Related Research Articles

<span class="mw-page-title-main">Greenhouse effect</span> Atmospheric phenomenon causing planetary warming

The greenhouse effect occurs when greenhouse gases in a planet's atmosphere insulate the planet from losing heat to space, raising its surface temperature. Surface heating can happen from an internal heat source as in the case of Jupiter, or from its host star as in the case of the Earth. In the case of Earth, the Sun emits shortwave radiation (sunlight) that passes through greenhouse gases to heat the Earth's surface. In response, the Earth's surface emits longwave radiation that is mostly absorbed by greenhouse gases. The absorption of longwave radiation prevents it from reaching space, reducing the rate at which the Earth can cool off.

<span class="mw-page-title-main">Global warming potential</span> Potential heat absorbed by a greenhouse gas

Global warming potential (GWP) is an index to measure how much infrared thermal radiation a greenhouse gas would absorb over a given time frame after it has been added to the atmosphere. The GWP makes different greenhouse gases comparable with regard to their "effectiveness in causing radiative forcing". It is expressed as a multiple of the radiation that would be absorbed by the same mass of added carbon dioxide, which is taken as a reference gas. Therefore, the GWP has a value of 1 for CO2. For other gases it depends on how strongly the gas absorbs infrared thermal radiation, how quickly the gas leaves the atmosphere, and the time frame being considered.

<span class="mw-page-title-main">Climate model</span> Quantitative methods used to simulate climate

Numerical climate models are mathematical models that can simulate the interactions of important drivers of climate. These drivers are the atmosphere, oceans, land surface and ice. Scientists use climate models to study the dynamics of the climate system and to make projections of future climate and of climate change. Climate models can also be qualitative models and contain narratives, largely descriptive, of possible futures.

<span class="mw-page-title-main">Radiative cooling</span> Loss of heat by thermal radiation

In the study of heat transfer, radiative cooling is the process by which a body loses heat by thermal radiation. As Planck's law describes, every physical body spontaneously and continuously emits electromagnetic radiation.

<span class="mw-page-title-main">Thermal radiation</span> Electromagnetic radiation generated by the thermal motion of particles

Thermal radiation is electromagnetic radiation emitted by the thermal motion of particles in matter. Thermal radiation transmits as an electromagnetic wave through both matter and vacuum. When matter absorbs thermal radiation its temperature will tend to rise. All matter with a temperature greater than absolute zero emits thermal radiation. The emission of energy arises from a combination of electronic, molecular, and lattice oscillations in a material. Kinetic energy is converted to electromagnetism due to charge-acceleration or dipole oscillation. At room temperature, most of the emission is in the infrared (IR) spectrum. Thermal radiation is one of the fundamental mechanisms of heat transfer, along with conduction and convection.

<span class="mw-page-title-main">Microwave radiometer</span> Tool measuring EM radiation at 0.3–300-GHz frequency

A microwave radiometer (MWR) is a radiometer that measures energy emitted at one millimeter-to-metre wavelengths (frequencies of 0.3–300 GHz) known as microwaves. Microwave radiometers are very sensitive receivers designed to measure thermally-emitted electromagnetic radiation. They are usually equipped with multiple receiving channels to derive the characteristic emission spectrum of planetary atmospheres, surfaces or extraterrestrial objects. Microwave radiometers are utilized in a variety of environmental and engineering applications, including remote sensing, weather forecasting, climate monitoring, radio astronomy and radio propagation studies.

<span class="mw-page-title-main">Radiative forcing</span> Difference between solar irradiance absorbed by the Earth and energy radiated back to space

Radiative forcing is a concept used in climate science to quantify the change in energy balance in Earth's atmosphere. Various factors contribute to this change in energy balance, such as concentrations of greenhouse gases and aerosols, and changes in surface albedo and solar irradiance. In more technical terms, it is defined as "the change in the net, downward minus upward, radiative flux due to a change in an external driver of climate change." These external drivers are distinguished from feedbacks and variability that are internal to the climate system, and that further influence the direction and magnitude of imbalance. Radiative forcing on Earth is meaningfully evaluated at the tropopause and at the top of the stratosphere. It is quantified in units of watts per square meter, and often summarized as an average over the total surface area of the globe.

<span class="mw-page-title-main">Black-body radiation</span> Thermal electromagnetic radiation

Black-body radiation is the thermal electromagnetic radiation within, or surrounding, a body in thermodynamic equilibrium with its environment, emitted by a black body. It has a specific, continuous spectrum of wavelengths, inversely related to intensity, that depend only on the body's temperature, which is assumed, for the sake of calculations and theory, to be uniform and constant.

<span class="mw-page-title-main">Emissivity</span> Capacity of an object to radiate electromagnetic energy

The emissivity of the surface of a material is its effectiveness in emitting energy as thermal radiation. Thermal radiation is electromagnetic radiation that most commonly includes both visible radiation (light) and infrared radiation, which is not visible to human eyes. A portion of the thermal radiation from very hot objects is easily visible to the eye.

<span class="mw-page-title-main">Earth's energy budget</span> Accounting of the energy flows which determine Earths surface temperature and drive its climate

Earth's energy budget accounts for the balance between the energy that Earth receives from the Sun and the energy the Earth loses back into outer space. Smaller energy sources, such as Earth's internal heat, are taken into consideration, but make a tiny contribution compared to solar energy. The energy budget also accounts for how energy moves through the climate system. The Sun heats the equatorial tropics more than the polar regions. Therefore, the amount of solar irradiance received by a certain region is unevenly distributed. As the energy seeks equilibrium across the planet, it drives interactions in Earth's climate system, i.e., Earth's water, ice, atmosphere, rocky crust, and all living things. The result is Earth's climate.

The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature when the body's emissivity curve is not known.

<span class="mw-page-title-main">Infrared window</span> Atmospheric window

The infrared atmospheric window refers to a region of the infrared spectrum where there is relatively little absorption of terrestrial thermal radiation by atmospheric gases. The window plays an important role in the atmospheric greenhouse effect by maintaining the balance between incoming solar radiation and outgoing IR to space. In the Earth's atmosphere this window is roughly the region between 8 and 14 μm although it can be narrowed or closed at times and places of high humidity because of the strong absorption in the water vapor continuum or because of blocking by clouds. It covers a substantial part of the spectrum from surface thermal emission which starts at roughly 5 μm. Principally it is a large gap in the absorption spectrum of water vapor. Carbon dioxide plays an important role in setting the boundary at the long wavelength end. Ozone partly blocks transmission in the middle of the window.

A runaway greenhouse effect will occur when a planet's atmosphere contains greenhouse gas in an amount sufficient to block thermal radiation from leaving the planet, preventing the planet from cooling and from having liquid water on its surface. A runaway version of the greenhouse effect can be defined by a limit on a planet's outgoing longwave radiation which is asymptotically reached due to higher surface temperatures evaporating water into the atmosphere, increasing its optical depth. This positive feedback means the planet cannot cool down through longwave radiation and continues to heat up until it can radiate outside of the absorption bands of the water vapour.

The anti-greenhouse effect is a process that occurs when energy from a celestial object's sun is absorbed or scattered by the object's upper atmosphere, preventing that energy from reaching the surface, which results in surface cooling – the opposite of the greenhouse effect. In an ideal case where the upper atmosphere absorbs all sunlight and is nearly transparent to infrared (heat) energy from the surface, the surface temperature would be reduced by 16%, which is a significant amount of cooling.

<span class="mw-page-title-main">Atmospheric window</span> Range of EM wavelengths that can pass through Earths atmosphere

An atmospheric window is a region of the electromagnetic spectrum that can pass through the atmosphere of Earth. The optical, infrared and radio windows comprise the three main atmospheric windows. The windows provide direct channels for Earth's surface to receive electromagnetic energy from the Sun, and for thermal radiation from the surface to leave to space. Atmospheric windows are useful for astronomy, remote sensing, telecommunications and other science and technology applications.

<span class="mw-page-title-main">Idealized greenhouse model</span> Mathematical estimate of planetary temperatures

The temperatures of a planet's surface and atmosphere are governed by a delicate balancing of their energy flows. The idealized greenhouse model is based on the fact that certain gases in the Earth's atmosphere, including carbon dioxide and water vapour, are transparent to the high-frequency solar radiation, but are much more opaque to the lower frequency infrared radiation leaving Earth's surface. Thus heat is easily let in, but is partially trapped by these gases as it tries to leave. Rather than get hotter and hotter, Kirchhoff's law of thermal radiation says that the gases of the atmosphere also have to re-emit the infrared energy that they absorb, and they do so, also at long infrared wavelengths, both upwards into space as well as downwards back towards the Earth's surface. In the long-term, the planet's thermal inertia is surmounted and a new thermal equilibrium is reached when all energy arriving on the planet is leaving again at the same rate. In this steady-state model, the greenhouse gases cause the surface of the planet to be warmer than it would be without them, in order for a balanced amount of heat energy to finally be radiated out into space from the top of the atmosphere.

<span class="mw-page-title-main">Greenhouse gas</span> Gas in an atmosphere that absorbs and emits radiation at thermal infrared wavelengths

Greenhouse gases (GHGs) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. What distinguishes them from other gases is that they absorb the wavelengths of radiation that a planet emits, resulting in the greenhouse effect. The Earth is warmed by sunlight, causing its surface to radiate heat, which is then mostly absorbed by greenhouse gases. Without greenhouse gases in the atmosphere, the average temperature of Earth's surface would be about −18 °C (0 °F), rather than the present average of 15 °C (59 °F).

The planetary equilibrium temperature is a theoretical temperature that a planet would be if it were in radiative equilibrium, typically under the assumption that it radiates as a black body being heated only by its parent star. In this model, the presence or absence of an atmosphere is irrelevant, as the equilibrium temperature is calculated purely from a balance with incident stellar energy.

<span class="mw-page-title-main">Water vapor windows</span>

Water vapor windows are wavelengths of infrared light that have little absorption by water vapor in Earth's atmosphere. Because of this weak absorption, these wavelengths are allowed to reach the Earth's surface barring effects from other atmospheric components. This process is highly impacted by greenhouse gases because of the effective emission temperature. The water vapor continuum and greenhouse gases are significantly linked due to water vapor's benefits on climate change.

In the study of heat transfer, Schwarzschild's equation is used to calculate radiative transfer through a medium in local thermodynamic equilibrium that both absorbs and emits radiation.

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