The Greenhouse Effect?

Question

Can Someone Please explain the greenhouse effect using the big idea of engery and describe some of the causes of the greenhouse effect. also describe some of the effects.
Thanks :)
Katiee x

Answer 1

The greenhouse effect, first discovered by Joseph Fourier in 1824, and first investigated quantitatively by Svante Arrhenius in 1896, is the process in which the emission of infrared radiation by an atmosphere warms a planet's surface. In the case of the Earth, without these greenhouse gases its surface would be up to 30°C cooler. The name comes from an incorrect analogy with the way in which greenhouses are heated by the sun in order to facilitate plant growth. In addition to the Earth, Mars, and especially Venus have greenhouse effects.

In common parlance, the term "greenhouse effect" may be used to refer either to the natural greenhouse effect, due to naturally occurring greenhouse gases, or to the enhanced (anthropogenic) greenhouse effect, which results from gases emitted as a result of human activities (see also global warming, scientific opinion on climate change and attribution of recent climate change).


The basic mechanism

The Earth receives energy from the Sun in the form of radiation. The Earth reflects about 30% of the incident solar flux; the remaining 70% is absorbed, warming the land, atmosphere and oceans, and powering life on this planet.

To the extent that the Earth is in a steady state, the energy stored in the atmosphere and ocean does not change in time, so energy equal to the absorbed solar radiation must be radiated back to space. Earth radiates energy into space as black-body radiation, which maintains a thermal equilibrium. This thermal, infrared radiation increases with increasing temperature. One can think of the Earth's temperature as being determined by the infrared flux needed to balance the absorbed solar flux.
Solar radiation at top of atmosphere and at Earth's surface.
Solar radiation at top of atmosphere and at Earth's surface.

The visible solar radiation heats the surface, not the atmosphere, whereas most of the infrared radiation escaping to space is emitted from the upper atmosphere, not the surface. The infrared photons emitted by the surface are mostly absorbed by the atmosphere and do not escape directly to space.
Atmospheric transmittance of various wavelengths of electromagnetic radiation (measured along sea level).
Atmospheric transmittance of various wavelengths of electromagnetic radiation (measured along sea level).

The reason why this results in a warming of the surface is most easily understood by starting with a model of a purely radiative greenhouse effect, in which one ignores the fact that a large part of the energy transfer in the atmosphere is not in fact radiative, but associated with convection (sensible heat transport) and the evaporation and condensation of water vapor, or latent heat transport. In this purely radiative case, one can think of the atmosphere as emitting infrared radiation both upwards and downwards. The upward infrared flux emitted by the surface must balance not only the absorbed solar flux but also this downward infrared flux emitted by the atmosphere. The surface temperature will rise until it generates thermal radiation equivalent to the sum of these two incident radiation streams.

A more realistic picture taking into account the convective and latent heat fluxes is somewhat more complex. But the following simple model captures the essence. The starting point is to note that the opacity of the atmosphere to infrared radiation determines the height in the atmosphere from which most of the photons emitted to space are emitted. If the atmosphere is more opaque, the typical photon escaping to space will be emitted from higher in the atmosphere, because one then has to go to higher altitudes to see out to space in the infrared. Since the emission of infrared radiation is a function of temperature, it is the temperature of the atmosphere at this emission level that is effectively determined by the requirement that the emitted flux balance the absorbed solar flux.

But the temperature of the atmosphere generally decreases with height above the surface, at a rate of roughly 6.5 °C per kilometer on average, until one reaches the stratosphere 10-15 km above the surface. (Most infrared photons escaping to space are emitted by the troposphere, the region bounded by the surface and the stratosphere, so we can ignore the stratosphere in this simple picture.) A very simple model, but one that proves to be remarkably useful, involves the assumption that this temperature profile is simply fixed, by the non-radiative energy fluxes. Given the temperature at the emission level of the infrared flux escaping to space, one then computes the surface temperature by increasing temperature at the rate of 6.5 °C per kilometer, the environmental lapse rate, until one reaches the surface. The more opaque the atmosphere, and the higher the emission level of the escaping infrared radiation, the warmer the surface, since one then needs to follow this lapse rate over a larger distance in the vertical. While less intuitive than the purely radiative greenhouse effect, this less familiar radiative-convective picture is the starting point for most discussions of the greenhouse effect in the climate modeling literature.

The term "greenhouse effect" is a source of confusion in that actual greenhouses do not warm by this same mechanism (e.g. [1]).

Answer 2

The concept is simple: Some materials like glass, clear plastic, certain gases (CO2, methane, water vapor) readily allow the transmission of visible light and reflect longer wave length light like infrared. This keeps what's inside warmer just like a greenhouse keeps the inside warmer than the outside and holds heat during the night.

When applied on a massive scale to the Earth's atmosphere it keeps the Earth from becoming an ice ball. Theoretically, excessive amounts of greenhouse gases released into the atmosphere would cause the temperature of the Earth to rise. This temperature rise has been postulated through computer models along with proposed catastrophic results but has not been proved scientifically at this time.

Many have offered anecdotal evidence supporting man caused global warming and the entire subject is now so politicized that any solution coming out of this controversy will probably be very costly and ineffective.

Answer 3

The Greenhouse effect is caused by greenhouse gases, such as carbon dioxide and methane building up in the atmosphere. It acts like a greenhouse heating up the globe.

I don't think many would dispute there is global warming. What causes this is more the area of dispute, i.e. is it natural fluctuations, is it 100% caused by man, or is it a combination of the two. I think probably the 100% caused by man is the least likely.

If global warming continues it will melt the ice at the poles, and Greenland causing massive sea level rises destroying many cities. Increased temperatures will cause climate changes, creating new deserts and water shortages. Also, the permafrost in Siberia may melt releasing enormous amounts of methane, thus feeding the Greenhouse effect and possibly leading to the worst nightmare THE RUNAWAY GREENHOUSE EFFECT, such as is on Venus.

Answer 4

The greenhouse effect is the ability of the earth to absorb and reflect infrared radiation. Gasses such as water vapor and methane, from clouds and cows respectively, are the greatest sources of greenhouse gasses. Radiation energy from the sun goes through space, where the gasses absorb some of the energy and it is turned into heat. some energy is reflected back outwards. the earth would be 40 degrees or so warmer if it werent for the cooling effects of clouds and weather.

Answer 5

ok imagine your in a green house, the sun is shining through the windows. some of it reflects off the ground and goes back up, some of THAT energy is reflected back off the windows and stays in the greenhouse...thus the greenhouse gets hot

Answer 6

its when co2 which has been given off by pollution surrounds the earth, making heat energy struggle to escape from the earth's atmosphere so it bounces back to earth instead, which heats the place up.