Ozon = different kinds of oxygen .. ozon absorbs UV radiation, cause ozone hole = greenhouse gases,
but there isn’t getting more sunlight through the hole and they don’t cause the greenhouse warming,
Natural greenhouse gases:
Water vapor, carbon dioxide, methane, force fires .. they are good, because they keep the earth
about 6 degrees, without them earth would be frozen,
Carbon dioxide :
 Is the main human made greenhouse gas, by burning, oil and coal
 Too much of the gas, is causing a significant warming,
Level of co2 : measure  in Greenland and drill down thousands of feet down in the ice, they have a
lot of dates about co2, when co2 was high-> temperature was high,
Climate models :
A model is a reproduction of reality, the computer calculate a climate model and this shows what will
happen in the future
Greenhouse gases trap infrared radiation (invisible heat)
Methane: it is underground, has a big greenhouse effect and traps infrared radiation,
Ozone And Greenhouse Gases
What is the "ozone layer"?
Ozone is a form of oxygen that has three atoms in it instead of the two atoms which is the form we are used to
breathing. Most of the ozone in the atmosphere lies in a layer that is centered around 2 miles above earth's
surface. The ozone layer absorbs ultra-violet radiation. Were ultra-violet radiation to penetrate fully to earth's
surface, it would destroy life at the surface and, in fact, a precondition for life existing was the development of the
ozone layer hundreds of millions of years ago.
How is global warming related to the hole in the ozone layer?
People often confuse global warming with the hole in the ozone layer. The most important connection is that, the
gases that used to cause the ozone hole are also greenhouse gases, and contribute to the warming of the earth.
Some people are under the delusion that ozone hole opens up, allows more sunlight in, and warms the earth -this is not true.
What are "natural greenhouse gases"?
Natural greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide. These natural
greenhouse gases are emitted by natural processes. For instance, when trees die and decay, because they're
made of carbon, the natural greenhouse gas carbon dioxide goes up in the atmosphere. When forest fires destroy
forests, they produce carbon dioxide, a natural greenhouse gas. And many forest fires are a natural phenomenon,
caused, say, by lightning. Those natural greenhouse gases are a good thing, because they keep Earth about 6°F
warmer than it would otherwise be. In other words, without the natural greenhouse gases, Earth would be a
frozen desert. Unfortunately, humans are pumping up the levels of greenhouse gases beyond their natural level,
and that's causing an unnatural warming of the Earth. And that spells real trouble for the future.
What is "carbon dioxide" or "CO2" and how does it contribute to global warming?
Carbon dioxide is the main human made greenhouse gas and it's the result of burning coal, oil and natural gas
which are the major power sources in our society. The other major source of carbon dioxide is the cutting and
burning of forests -- particularly to clear land for agriculture and that's an important phenomenon in developing
countries like Brazil and part of Africa. The trouble is that all those carbon dioxide emissions have raised the
amounts carbon dioxide in the atmosphere about 30% above what they were in pre-industrial times a couple of
hundred years ago. That extra thickening of the greenhouse blanket is causing a significant warming of earth that
is only going to get worse in the future if we don't stem the increase in carbon dioxide and the other greenhouse
gases.
How far back in time can scientists measure CO2 levels?
The level of CO2 was measured directly by a monitor on top of a volcano in Hawaii starting in 1957 but we have
other, very clever ways of measuring it from a hundred, a thousand, and 100,000 and 700,000 years ago.
Scientists go to the centre of Greenland and Antarctica, and drill with a machine that looks like an oil rig. They drill
down thousands of feet, pull up huge sections of ice, and segment that ice in laboratories. Ice from these cores
looks just like ice in an ice cube in your refrigerator. It has air bubbles trapped in it, which are samples of the
atmosphere as it was when the ice formed, as I said, as many as 700,000 years ago. So, we have a very, very
solid record of carbon dioxide levels going back a very long time. Over that period, the Earth moved in and out of
ice ages. We have other ways of measuring what the Earth's temperature was at the time, and there's a very,
very close correlation. Every time that carbon dioxide was high for a sustained period, the Earth's temperature
was high. When carbon dioxide was low for a sustained period, the Earth's temperature was low throughout that
whole 700,000 years. That's very strong evidence that, as we continue to pump up carbon dioxide and the other
greenhouse gases, the Earth's temperatures are going to warm significantly.
What is the "Medieval Warm Period"?
About a thousand years ago, parts of the North Atlantic Basin - Greenland, the UK, parts of Northern Europe,
perhaps parts of Canada - were a little bit warmer than today. The warming was magnified around Greenland, so
that areas became ice-free and could be settled. And as a result, the dominance of the Norse people spread into
that area. When Earth cooled again, Greenland cooled, and the settlers were driven out. It's often argued, "if
Earth was warm during the Medieval Warm Period, what are we worried about in the future?". Well, that warming
was apparently restricted to a very small spot on Earth, and it was modest warming. If you look back in the
indirect records we have of Earth's temperature, it turns out that the warming we saw in the last 50 years, due to
the build-up of the greenhouse gases, was bigger than anything that happened in the Medieval Warm Period; the
fact that Earth went through minor climate cycles in individual spots in the past really is not much of a reason to
not worry about the future.
What are "climate models"?
A "climate model" is a reproduction of reality. If you collect, and combine, a number of equations, you can create
a rough representation of how the world operates. If you then feed data into these equations, then you can obtain
a reasonable forecast of what the future holds, with regard to climate.
What is "infrared radiation" and how does it contribute to global warming?
Infrared radiation is essentially invisible heat that radiates or comes up from hot bodies and tries to go out into
space. The greenhouse gases have the property of trapping infrared radiation and it's because of that infrared
trapping property that the build-up of greenhouse gases causes global warming. They act like an invisible blanket
in that they trap infrared radiation near a surface.
What is "methane" and how does it contribute to global warming?
Methane is the major component of natural gas, and it is found underground. Methane is a powerful trapping
agent, and contributes to global warming by holding infrared radiation near Earth's surface. The way humans add
to the buildup of methane include: leaks in the methane pipeline, the decay of landfill material and certain farming
methods, namely rice growing. There are many different human activities that contribute to the buildup of
methane, and contribute to the buildup of the greenhouse effect.
What is "sulfur hexafluoride" and how is it created?
Sulfur hexafluoride is one of the most powerful greenhouse gases, and is created in several industrial processes,
from the electronic industry. Sulfur hexafluoride is very strong, and the industry has taken various steps to limit its
release.
What is "water vapor" and why is it considered a greenhouse gas?
Water vapor exists naturally in the atmosphere, because water evaporates from the oceans, forms clouds, and
clouds form precipitation. In the interim stage, when it's vapor in the atmosphere, it can trap infrared radiation,
heat and is a very dangerous greenhouse gas. While human beings don't have the ability to add significantly to
the amount of water vapor in the atmosphere by direct emissions, there is an amplified level due to increased
warming from high CO2 levels. That's called a positive feedback, "positive" because it makes the initial effect of
the warming worse.
How are humans contributing to the amount of greenhouse gases and global
warming?
Human beings are contributing to greenhouse gas levels, and to global warming, through the burning of fossil
fuels; the cutting and burning of forests; through various agricultural processes, that lead to the build-up of
methane and nitrous oxide; through some of the chemicals which are substitutes for Freons, which are now used
in air conditioners and refrigerators; and through the production of smog, because smog contains ozone, which
itself is a greenhouse gas.