teacher said:
Since no one has put this out there yet. Consider the greatest influencer of the Earths temperature. The sun. And we have no control over that.
It has been "Put out there" already. Global mean temperatures have been increasing in recent decades, but there has been no increasing solar activity trend.
New: The Sun puts out 10% percent more energy every 1 billion years. For those of you in this thread: That means the Earth is getting hotter. No matter what we do.
This issue is about trends in recent years and whether those trends are natural. It's irrelevant what the sun will be doing in one billion years time unless that affects recent climate trends.
For the question of how many cycles of cooling/warming in the Earths history. Might want to go search the boys in Greenland taking core samples of the ice. Goes back like hundreds of thousands of years.
But can recent trends be explained as natural cycles? It's a fallacy to suggest that because natural cycles exist that therefore recent trends must be down to natural cycles.
For the ozone question that will surely pop up. With the cry, "The hole in the ozone is growing". Consider this (it's been a while). Artic animals have a very high tolerance to UV light. Indicating that the ozone at the poles is variable given that evolution has taken that into account.
But the issue is global warming, not ozone depletion.
The greatest particle polluter yearly on Earth? Volcanoes. Mount Pinatubo put out more matter in it's eruption than three years worth of what we do.
Again the issue is global warming, not pollution. So it isn't really particle pollutants that is the issue - it is greenhouse gases.
To the hacks a while back that said that because of the measured decrease in atmospheric particulate matter would end in the increased temperature of the earth due to more sunlight striking the ground. Consider whether that matter is on the ground or in the air the sunlight is still hitting something. No change. Again the deciding factor is how much energy from the sun hits us.
No it is very different indeed. Clouds also block the sun and they have a negative warming effect. If the light does not reach the ground then longwave radiation will be emitted higher up, meaning less will be trapped and so less of a warming effect.
The greatest producer (Beside the Earth her self I think) of Methane? Cow flatulence.
This isn't actually the case:
http://www.epa.gov/methane/sources.html
But even so how much a producer emits is irrelevent to global warming. What is relevant is the variation in production in recent times. When it comes to most natural methane emitters, such as termites, the production there is massive but it hasn't increased. So that would not cause a warming effect.
Cows are a case of increasing emissions of methane as the cow population has risen out of our doing.
Here's a new thought.
What if our human experience just happened to be during a normal global cool down. You know, like when the US was covered with glaciers, over and over. Would all you chicken littles then be yelling, "Oh my friggin god, we are cooling the earth". To bad this isn't in the basement. But hey, you guys are fun to watch.
There is a mechanism for the warming. Increased greenhouse gases, specifically co2 (which is the main greenhouse forcing), will cause a warming effect. How much is not known, but it is estimated that the temperature will increase by about 2.5C over this century given projected trends of greenhouse gas emissions. Calculations based on the same warming factor per doubling of co2 also suggest most of the recent warming can be attributed to greenhouse gas emissions.
Given that the physics says there should be warming, therefore to be recording warming seems a little too coincidental for some people.
The Earth is getting warmer. It's a fact. Just like it has over and over before.
Except this time there is also a huge spike in co2. It isn't "just like before". The situation is different and therefore it bears examination to see if the cause is different.
