“Greenhouse Gases” is the term we give to those gases that have the ability to retain heat in the atmosphere. The most common ones are water vapour, carbon dioxide, methane and nitrous oxide, there are thousands of others but these four account for more than 99% of all warming.
Without getting too technical, these molecules of gas vibrate at their own specific frequencies (as does everything). It just so happens that these frequencies correspond to the wavelength of certain types of heat energy and it’s this corresponding frequency that enables the molecules of greenhouse gas to effectively grab hold of the photons of heat energy and retain them in our atmosphere.
If the frequencies didn’t match then the heat energy would simply be lost into space and the entire greenhouse effect would collapse. Were that to happen there would be no warming (natural or manmade) and Earth would be nothing more than a frozen ball of ice, devoid of all lifeforms.
It’s important to know that greenhouse gases only absorb at specific frequencies. The heat we receive from the Sun is at the wrong frequency and so passes through the atmosphere without interacting with the greenhouse gases (the Sun is very hot, the radiation it emits is highly energetic shortwave solar radiation). After the Sun has warmed the ground, roads, buildings etc they re-emit that heat back outwards but this time it’s at a frequency that does correspond to the greenhouse gases (it’s longwave thermal or infrared radiation).
That’s the basics of how the greenhouse effect works, so how does changing the amount of greenhouse gas cause changes in the climate?
Until about 100 years ago the amount of greenhouse gas in the atmosphere has varied very little. For more than 20 million years it stayed within the range of 180 to 290 parts per million by volume. In the last century we’ve added so much greenhouse gas that it’s now reached the 400 ppmv mark. Roughly, this means that there was 2 trillion tonnes of greenhouse gas in the atmosphere, now there’s 3 trillion tonnes.
More greenhouse gas means that more heat can be trapped by the gas molecules. This is what we would expect to see happening, and indeed it is. The heat content of the atmosphere is at record levels and average global temperatures are now higher than at any time since at least the last but one ice-age.
Because the atmosphere is warming it means that more heat is flowing from the atmosphere into cooler bodies such as the ground and the oceans (heat always flows from warm to cool – 2nd law of thermodynamics). Not only is the atmosphere warming, the whole planet is.
The next concept to grasp is that all aspects of the weather and climates are driven by the presence (or absence) of heat energy. It’s heat energy and the way it’s distributed and moves around the planet that causes the weather, even the coldest of weather events is a consequence of the presence of heat energy.
As more heat builds up in the oceans and atmosphere it impacts on the way they weather is formed. In general it means that extreme events become more common and it’s no surprise therefore that the frequency and intensity of floods, droughts, heatwaves, storms etc have all increased.
This pattern won’t be repeated everywhere around the world, there are some places where warmer conditions will moderate the weather and reduce the probability of extreme weather events.
In general, the prevailing conditions will be exacerbated. Areas that are already prone to drought will see an intensification of drought conditions, whereas areas where rain is a common feature will see more rain overall and more extreme rainfall events.
This is just some of the very basics, there’s a lot more to it than this.
The mean surface temperature of the planet is determined by an equilibrium between the energy that's coming in and the energy that's going out. Without greenhouse gases that's simply the incoming solar energy (minus what's reflected directly back into space) and the blackbody radiation of the surface of the planet.
When you add greenhouse gases, the surface of the Earth now also has infrared energy that's being emitted by the greenhouse gases of the atmosphere. This changes the equilibrium of the planet and increases the surface temperature, since some of the energy that would have gone directly back into space.
if you increase the greenhouse gases, you will increase the mean surface temperature. This is fairly straightforward physics, although there are some people that try to get around it in various ways, such as increasing the cloudiness of the planet. Note that such an argument STILL is telling us that the climate is changing, since the cloudiness will have increased.
EDIT: Dr Jello's statement about "We have only added at best 0.012% more carbon into the atmosphere..." is false. The amount of carbon in the atmosphere has increased by about 40%.
He normally just tries to mislead, instead of saying something that could blatantly be considered false, but this time he slipped up and phrased his statement so that he could not rely on an ambiguous interpretation.
Doubling of CO2 levels according to basic physics increases temperatures by 1.2C. Nature will moderate this through various mechanisms, for example changes in cloudiness caused by warming. This would serve to reduce the overall amount of global warming to be smaller, and in line with the natural warming that has been happening for centuries as the planet recovers from a Little Ice Age.
Supposedly, Smog and other industrial polluting gases get trapped in our atmosphere and block the heat from the sun from escaping once it is absorbed into the atmosphere. This serves to cause rises in the earth's temperature / climate above normal expected levels. A warmer earth overall promotes the ice caps melting, the sea levels around the world to rise, and for biological life to become endangered due to climate changes that regional animals are not capable to adapt to.
In short, Heat from Sun absorbed, blocked from dispersing back out into space, heats earth, causes unstable weather patterns and ice cap melting - affects all life and climates on earth. There ya go.
http://www.rkm.com.au/ANIMATIONS/carbon-... <== here's the physics.
For both water and CO2. You really want to understand what it's saying.
The more water and CO2 there is in the atmosphere, the more heat the earth retains.
This is the basic science behind global warming.
Without the relatively small amount of water and CO2 in our atmosphere, the earth would be 60 degrees colder than it is.
Far below freezing.
http://en.wikipedia.org/wiki/Global_warm...
Wikipedia probably has the most complete description in one place.
We have only added at best 0.012% more carbon into the atmosphere in the last 100 years. This isn't enough to cause any change in the climate.
temprature will increase and the environmental climate will not be stable.
