We are not that powerful and we have very little impact on the planet. On people yes, one the environment that we need to survive yes, so it is good that you do your part. I don't really understand your distinction - either you have the impact or you don't.
No middle ground here the only two options are either you have the impact or you don't. That is a classic false dilemma. Then the dribble turns to appeal to emotion.
You tend to forget how small we are. The Sun is gigantic and getting hotter. The Earth core temperature is also heating which in turn would cause the oceans to heat up (think of a pot of water the most effective way to heat up water is when heat is applied in close proximity and heating up the air would take forever and have very little impact).
Here are a few scholarly journals:
http://www.griffith.edu.au/conference/ics2007/pdf/ICS176.pdf
"“According to the findings reviewed in this paper, the variable output of the sun, the sun’s gravitational relationship between the earth (and the moon) and earth’s variable orbital relationship with the sun, regulate the earth’s climate. The processes by which the sun affects the earth show periodicities on many time scales; each process is stochastic and immensely complex."
One can be lead to postulate that the same thing is happening on mars, venus, and other planets.
http://www.agu.org/pubs/crossref/2007/2007GL030207.shtml
The study found that times of high solar activity are on average 0.2 degrees C warmer than times of low solar activity, and that there is a polar amplification of the warming. This result is the first to document a statistically significant globally coherent temperature response to the solar cycle"
http://cat.inist.fr/?aModele=afficheN&cpsidt=4048902
"Recent results have indicated strong correlations between climate parameters and solar activity. Upper troposphere and stratosphere temperatures have been found to vary in phase with the 10- to 12-year solar activity cycle. On a longer time scale, the global temperature, particularly the Northern Hemisphere land air temperature, has been found to be nearly perfectly correlated with the long-term variation of solar activity."
http://adsabs.harvard.edu/abs/2007P&SS...55..158R
This article was a fantastically interesting read because they used tree rings (yes, tree rings!) and they believe that the impact is from solar activity and there's a cycle! Yet, another articles that says the earth's climate goes in a cycle!
Here's an article about neptune for you (we can't be having an affect on neptune (if you feel some how we are I think you're giving too much credit to humans. This shows that its has to do with the sun/solar system) http://www.agu.org/pubs/crossref/2007/2006GL028764.shtml
"If changing brightnesses and temperatures of two different planets are correlated, then some planetary climate changes may be due to variations in the solar system environment." The fact with mars leads me to believe that it has something to do with the solar system.
It seems that people put a lot of faith in that man is causing this whole GW thing. If man is (which I don't believe. Again I'm not saying we shouldn't take care of earth. We should) causing GW India and China have given the finger to all of this.
India and China populations are way bigger than the U.S and E.U. combined. The line of agrument is that they're ONLY developing countries. Yeah developing both are developing fast. Both are using more coal. Both have auto sales that have exploded (maybe we should export some of our cars to them). Both having more people don't they have a great potential of messing up the environment?
Oh wait, we're suppose to lead by example. I'm sure that's going to make a difference with China and India, for they're going to do what's best for their country.