The biggest impactor of climate is, obviously, the sun. Changing the orbit of Earth, or the type of star Sol is, could vary temperatures by billions of degrees Celsius/Kelvin.
The second is water in the atmosphere. Without it, Earth would be a frozen wasteland. With too much, the equatorial regions would be uninhabitable, at best.
Somewhere further down the line is Carbon. It certainly has an impact, but not nearly as much of one. I'm going on old memory here, but I vaguely recall the average temperature of Earth can only swing by ten or so degrees Celsius/Kelvin on Carbon alone. Which is significant seeing as how an average requires major local shifts to alter, but isn't so severe that all of Earth is going to become a desert.
Weighing our impact is one of the most complex formulae to exist, in my experience. You have to factor in and measure all human sources, and all non-human sources of Carbon. Then you have to factor in the natural lifespan of Carbon in the atmosphere, and how the Earth absorbs it.

The planet is going to do what it does beyond our control. I think the temperature issue is a bad argument. Even if the planet's temperature wasn't affected by CO2 we collectively as a species are producing more and more waste at an increasing population. The waste will get into our resources, such as water and food and fish. Everything from dog poo, to discarded medicine to paint, to plastics to ink. Basically anything you put in your garbage can, multiply that by 7 billion people and a growing population. That IS going to have an affect regardless of whether the temperature changes.

A clogged toilet at the North pole isn't sanitary just because it is cold. Would you make a snow cone out of snow that had mercury or lead or oil in it? Temperature change doesn't mean we are not over polluting the planet. The earth is our home, it cannot be used as a giant landfill. But if our population keeps exploding and we keep increasing our waste, eventually we will end up living in a giant landfill.

CO2 works to amplify (or not, when not present) changes that are otherwise natural.

CO2 is a minor greenhouse gas, only in that it is present in very low concentrations.  But what we've done is raise the "baseline" for how much energy stays in the lower atmosphere -- incoming shortwave radiation (ultraviolet light, etc) is converted into =more= longwave radiation (infrareds) than before.  This causes the temperature to rise.

This small increase in temperature that's attributable to CO2 causes an exponentially larger increase in water vapor, which is then present in much higher concentrations.

The normal feedback cycle with HO2 (water ...) is that warm moist air eventually rains out and water vapor gets reset to a lower concentration, with fewer greenhouse implications.  But with elevated (and rising ...) CO2 levels, the atmosphere doesn't get "reset".

What is critical to understand about water vapor is that the amount of water vapor the atmosphere can hold increases exponentially with temperature.  Small increases in temperature result in ever larger increases in water vapor.  The net result is extreme droughts where the temperature doesn't drop below the point where rainfall would occur, or extreme rainfall where it does.  Hotter air is better able to absorb more moisture from land, plants, people, resulting in a more arid environment.  That moisture laden air then moves, through the usual circulatory systems to wherever it normally would rain out.  But since there is more of it, extreme flooding is the result.

So "Global Warming" isn't the only thing that happens, like "Gee, it's 2 degrees warmer, no big deal."  In regions where rainfall is less common, rainfall will generally become even more less common.  In regions where rainfall is more common, rainfall generally will become even more common, and in higher rates.

There will also be changes in the circulation patterns themselves -- the Hadley cells -- so that the locations where air generally rises, carrying moisture into the atmosphere shift, and the locations where air generally falls, carrying moisture back to the ground, shift as well.  Under global warming, these shifts are towards the polls.  And here's the problem there -- the regions where rainfall is needed for crops become smaller and smaller as the latitude increases.  This is the basis for the "global famine" problem.

Start here - http://www.realclimate.org/index.php/archives/2007/05/start-here/

I'm not as concerned about trash as I am about the climate.  Right now there are companies working on producing electricity from landfill gas, and other companies working to turn trash into useful products.

The huge amount of chemical waste is a major concern, and the more we pay China to pollute the environment, the worse things will be.  The United States, at least, needs to pass laws that say imports will be taxed to the extent the manufacturers of those products don't adhere to US environmental protection laws, to some reasonable degree or other.  Otherwise companies will just export manufacturing to countries that pollute the environment to save a buck.

Right now the greatest obstruction to cleaning up the environment is the stupid belief that someones god isn't going to allow us to destroy the planet.  How right-wing Christians came to believe this is a mystery, but that seems to be what they believe.