1kg of water vapors condenses is 2.25*106jkg-1
1kg of water vapors condenses is 2.25*106jkg-1
rarefy--to thin out
The denialist lobby (i.e. those uninformed or willfully ignorant 'skeptics'--not that scientists themselves aren't skeptics--who deny the reality, impact or cause of global climate change) have embraced a position that can only be supported by science fiction, like Michael Crichton's State of Fear. As a result, their arguments are woefully inadequate to convince. They must deny so much evidence and data that they will accept any contrary argument instantly without thinking. For example, all hardcore global warming skeptics take issue with the computer models, of course. These models have lent huge support to the idea that anthropogenic greenhouse gases have contributed to climate warming over the last 60 years and have predicted dangerous warming under likely emissions scenarios for the remainder of this century, indicating the need to mitigate or avoid such warming by reducing our global carbon footprint. Skeptics need to refute these models, because they already "know" that global warming is a religious fantasy. One of their knock-down arguments has to do with clouds. The Australian climate denier Ian Plimer, for example, said that since clouds have such a huge impact on global climate, the uncertainty related to cloud cover over this century calls into questions many of the computer models' projections (these models, by the way, were the basis of the IPCC's four assessments, which laid the basis for two major treaties). Plimer believes that nature is the main driver of climate change, and that humans have almost nothing to do with shifting temperatures on a global scale. He thinks clouds could cancel out our activities or overwhelm any contribution to climate change. However, because clouds contribute to the greenhouse effect, they are not going to cancel human-induced climate change unless they shrink globally, which is not likely given that evaporation is increasing worldwide, causing more moisture in the air and speeding up cloud formation. Actually, what the denialists need to learn is that clouds are a positive feedback, i.e. they will amplify the warming humans initially cause by at least one degree Celsius globally. We know this to be true from purely physical reasons. So even if the models can't predict cloud patterns well, it doesn't matter. That doesn't cast the slightest doubt on the premise that humans are triggering climate warming.
It seems the higher you go the cooler it becomes does not apply to the stratospere.
"That is why the highest temperatures are found at the top of the stratosphere, but at the bottom of the troposphere." I am thinking that the word 'but' is an error, and should be 'and' based on the foregoing paragraph.
Please clarify the following: About 80% of the total mass of the atmosphere is within some 10 km of the surface; 99.9% lies below 50 km.
Muy buen tema
en esta sección hemos revisado las propiedades del ozono, atmósfera y demás. Que buen articulo
What is Empirical finding?
Energy flow follows the second law of thermodynamics.
The atmosphere is not a simple, uniform slab of absorbing material. On the contrary, it gets progressively ‘thinner’ or less dense with increasing altitude (height above mean sea level); i.e. the total number of molecules in a given volume of air is lower, and so is the pressure.
About 80% of the total mass of the atmosphere is within some 10 km of the surface; 99.9% lies below 50 km.
The key greenhouse gas molecules (H2O and CO2) are also more abundant close to ground level, and increasingly scarce at higher altitudes. So a better picture of radiation trapping in the real atmosphere is to imagine it happening in a series of stages.
Outgoing longwave radiation is repeatedly absorbed and re-emitted as it ‘works up’ through the atmosphere; it is re-radiated to space only from levels high enough (i.e. thin enough) for absorption to have become weak. This suggests that the atmosphere should be warmer at ground level - close to the source of the outgoing radiation, and where the absorbing molecules are more abundant. Everyday experience confirms this expectation; it generally gets colder as you walk up a mountain, for example.
The temperature profile of the atmosphere shows that air temperature does indeed fall with increasing altitude throughout the lower atmosphere or troposphere, reaching a minimum value (of about -55°C) at the tropopause. This lies 8-15 km above the ground, depending mainly on latitude: it is higher (and colder) at the Equator than at the poles.
No mountains rise above the troposphere; it is where we live and where almost all weather phenomena (rain, clouds, winds, etc.) occur.
However, if you could travel higher up (without the protection of a jet aircraft), you would find that the temperature soon starts to increase again - and continues to do so up to the stratopause at the top of the stratosphere.
Effect of ozone
Like water vapour and CO2, the ozone in the troposphere acts as a greenhouse gas. Unlike those two gases, however, very little of the Earth's ozone is, in fact, in the lower atmosphere; the bulk of it (some 90%) is in the stratosphere, where it forms the so-called ozone layer.
In this more-rarefied region, ozone plays a different role because it also absorbs the shorter ultraviolet wavelengths in the solar spectrum - radiation that is lethal to many micro-organisms and can damage important biological molecules, leading to conditions such as skin cancer in humans.
The absorption of incoming solar energy by stratospheric ozone heats this region of the atmosphere directly. In effect, the stratosphere is heated from above, whereas the troposphere is heated from below.
This is why the highest temperatures are found at the top of the stratosphere, but at the bottom of the troposphere.
Effect of clouds
We have already identified one role that clouds play in the Earth's climate: they are highly reflective. At any given time, about half of our planet is covered by clouds; the sunlight they reflect back to space accounts for about 55% of the total planetary albedo.
However, clouds also absorb and re-emit outgoing longwave radiation; i.e. they contribute to the back radiation from the atmosphere, and hence to the natural greenhouse effect. This is why temperatures tend to be lower under clear night skies than on nights with extensive cloud cover.
Effect of convection
The troposphere is heated from below, with temperature then falling with increasing altitude. This situation sets the scene for the onset of convection - the bulk flow or circulation of a fluid driven by differences in temperature.
Convection in the atmosphere plays a vital role in two further mechanisms - quite apart from the emission of longwave radiation - whereby energy is transferred from the Earth's surface to the atmosphere.
The first is the transfer of thermal energy (often referred to rather loosely as ‘heat’) by a combination of conduction and convection. This is essentially the same mechanism that heats a saucepan of water on the stove. The situation in the atmosphere is more complicated, but the basic principle is the same.
Warm air, heated by contact with the ground or a warm sea, rises upwards carrying heat transferred from the surface aloft. This allows more cool air to come into contact with the surface and be heated in its turn. Working together, conduction/convection drive a significant flow of heat across the boundary between the surface and the air.
The second form of energy transfer is indirect, but even more important on a global scale. It involves the evaporation of water - mainly from the oceans, but also from lakes and rivers, soils, rocks and vegetation on land. Evaporation requires energy, known as the latent heat of vaporisation, which is extracted from the surface involved. This is why the evaporation of sweat acts to cool the body.
The latent heat of vaporisation of water, (i.e. the amount of heat needed to convert 1 kg of liquid water to water vapour at the same temperature (and the amount of heat released to the surrounding environment when 1 kg of water vapour condenses)) is 2.25 × 106 J kg -1 - higher than the value for any other substance.