The Earth is covered in oceans and atmosphere and as such reflects about 30% of of all electromagnetic radiation; therefore the Earth should in theory have an average surface temperature of about -18.6°C... but it doesn't...
The Earth's atmosphere absorbs radiation, and along with the thermal re-emission of heat due to both the land and the heat being trapped by the atmosphere itself, the Earth actually has an average surface temperature of 14.4°C... and rising.
A French fellow called Joseph Fourier was looking into describing the laws of heat conduction as early as 1824. Fourier's Law (also known as the Law of Heat Conduction) had predicted that the Earth should be much cooler than it actually was. He assumed that either there must be something in interstellar space or that the Earth's own atmosphere was causing the heat to be trapped. His proposal of a "Greenhouse Effect" was made in 1827.
In the 1860s John Tyndall was the first to quantitatively prove that various gases had differing abilities to absorb radiant heat. He was also able to prove using a thermopile, that not only did people breathe out CO2 but that the biggest single factor in the Greenhouse Effect was in fact water vapour.
In 1896 Svante Arrhenius came up with the theory that by altering CO2 levels, the planet would heat up and therefore become more productive.
"If the quantity of carbonic acid in the air should sink to one-half its present percentage, the temperature would fall by about 4°; a diminution to one-quarter would reduce the temperature by 8°. On the other hand, any doubling of the percentage of carbon dioxide in the air would raise the temperature of the earth's surface by 4°C; and if the carbon dioxide were increased fourfold, the temperature would rise by 8°C."
"We often hear lamentations that the coal stored up in the earth is wasted by the present generation without any thought of the future, and we are terrified by the awful destruction of life and property which has followed the volcanic eruptions of our days. We may find a kind of consolation in the consideration that here, as in every other case, there is good mixed with the evil. By the influence of the increasing percentage of carbonic acid in the atmosphere, we may hope to enjoy ages with more equable and better climates, especially as regards the colder regions of the earth, ages when the earth will bring forth much more abundant crops than at present, for the benefit of rapidly propagating mankind."
So given that the idea of The Greenhouse Effect has been around now and more or less provable for about 120 years, why then do people think that it's other trendy name "Global Warming" doesn't exist?
The most obvious example which should have served as a warning of the effects of CO2 is that of Venus. Venus is a planet which is about 90% the size Earth but which has a highly relective atmosphere which reflects rough 80% of all electromagnetic radiation; therefore Venus should in theory have an average surface temperature of about -29.5°C... but it doesn't...
Venus has not only has a very dense atmosphere but one which is rich in CO2. The atmosphere of Venus is roughly 96% CO2 and at the surface the temperatures are something like 500°C. The poor Soviet Venera 4 probe lasted 93 minutes before being crushed to death by the atmosphere.
The four gases which contribute most to the Greenhouse Effect on Earth are Water Vapour, Carbon Dioxide, Methane and Ozone.
Admittedly we can't do much about water vapour, but if the planet heats up then the volume of water which exists will expand, which might have nasty consequences. Ozone and Methane together count for about 3% of the atmosphere but CO2 is something which we're actually adding to.
It has been said that in the time of Shakespeare a squirrel could leap from treetop to treetop and cover the very length and breadth of England. Whether or not this was true or merely poetic (ie a fib) is moot, but the point is that England which once had great stands of Oak trees, is now a broadly pastoral or urban country. The once mighty Oaks now lie rotting at the bottom of the ocean, having been cut down, turned into ships and sunk during the times of Elizabeth I to Charles II.
Even in my lifetime, the Amazon rainforest has shrunk by 20% and it is expected that by 2030 more than half of the Amazon will be gone. Interestingly the soils left behind after the rainforest have been cut down are good for farming for about 10 years, and then they take on a character resembling that of sub-Saharan African soils.
The point being that with 200 years of solid industrialisation with no signs of abaiting, and with forests being cleared, I find it really difficult to believe that CO2 emissions increases are purely the result of natural factors. To suggest that humans have little control over the weather and environment is mind-numbingly stupid.
Now think what you will about all of this, but if there was an event which you were warned about which might or might not happen, wouldn't it make sense to prepare for that event occuring even if it didn't take place? Some people might even call that taking out an insurance policy.
Insurance by definition is a form of risk management which is used as a hedge against an uncertain loss. If we're being told about an uncertain loss of life as we know it due to Global Warming or the Greenhouse Effect, isn't it prudent to take out insurance against it?
As yet, no-one to my mind has come up with a satisfying answer as to why exactly that isn't the case, other than the immediate economic disadvantage. Except that just like in Queensland with the floods recently, if you don't think about adequate insurance, you're likely to lose everything.