OK, how did the acts of humans cause the climate changes that occured millions of years ago?
First. You seem to be under the impression that there is either natural climate change or man made climate change, not both.
Natural climate change happens for a lot of reasons. Solar radiation, plate tectonics, Volcanic eruptions, things like this.
However at present we're not seeing an increase in these.
Here's sunspot activity in red, there is a decrease which would have a negative impact on warming.
Major volcanic eruptions are on the slide too.
As for plate tectonics, the Earth seems to be stabilising much more. Temperatures have been quite consistent within the last 400,000 years.
Here you can see, more or less, a 100,000 year cycle of warming and cooling, there are mini events as the Earth cools, then it flares up, gets much warmer and then goes down again over the next 100,00 years or so. Where we are now looks like the peak has happened and we should be getting colder. We're not.
So while natural climate change has always been happening, and in recent times it has become more stable, I would expect, right now, to be seeing temperatures cooling, and cooling quite dramatically too. Here's the point I'm seeing. Humans have put stuff into the air which we know is a greenhouse gas, we know, more or less, what it does, but we keep putting it there.
We knew we were destroying the ozone with CFCs and we stopped producing them. Are you denying we had a big impact there? The loss of the ozone layer can help with an increase in temperatures.
CO2 is a greenhouse gas that is no where near as strong as others, but it's the time it spends in the atmosphere that is the problem.
Methane is 72 times stronger than CO2 as a greenhouse gas after 20 years in the atmosphere, but after 500 it is only 7.6 times stronger. So you pump a lot of methane in the atmosphere and the effects will be less strong in the future than if you pump 10 times more CO2 in the atmosphere which in the immediate future won't be a problem, but after a while the build up WILL be a problem.
The climate of our planet has been changing for millions of years and will be changing millions of years after man leaves it.
there is no such thing as "natural temperature". The sun's variations coupled with the tilt of the planet on its axis cause climate change, not some soccer mom driving an SUV.
Yes, I'm not saying the climate won't change. This isn't the debate, and if you think it is then you're going to have problems.
There is such a thing as "natural temperature", it's like there is a natural tropic of Capricorn and Cancer. They move as the Earth changes position, doesn't mean it's not natural where it is. Natural being the effects it has based on what it should do if left alone. We can't be 100% sure of what the temperature should be. However it's not the issue.
The issue is one of a change that is going to happen that A) we can't control and B) will cause serious problems for humans and other species on the planet.
So we know CO2 is a greenhouse gas. We know it helps to trap heat in. We know temperatures and CO2 go hand in hand, which comes first it doesn't necessarily matter. We also know that CO2 stays a long time. Now, if you put sand on top of sand it usually spreads out. When it can't spread out any more it starts to rise. If we put too much in and it changes what is supposed to happen and temperatures go through the roof. Then what? We don't know. But I really don't want to risk it being the sort of thing you wouldn't want to live through.