Thirza:
If you want a world which reflects the value of life that we place on it, then the first place to start looking is in how you interact with the world. All responsibility starts with us.
With that in mind you should probably get accustomed to the idea that you are in some way responsible for everything. Anything that happens you shoulder some responsibility for its happening that way (whether for good or for ill). If you don't like the way something is going, then it is on you to go out there and make sure it is stopped or changed for the better. That is the biggest stumbling block. Most people are content to let things happen unopposed; because opposition would involve effort and conflict with other people.
The second thing you want to consider is what is important enough to you to fight over, then research it a great deal. You mentioned "Global Warming." If this is really a place where you want to do battle, then start looking over energy production methods, energy efficiency, insulation, heating and cooling, industrial processes, industrial waste production... basically anything which could be a contributing factor to anthropogenic change to the climate (me personally I am not convinced that our influence is a large factor in driving climate change, but I am convinced we are being almost criminally negligent in our application of technologies).
For instance: Did you know that we can build nuclear reactors now that have ZERO radioactive waste products? (on a related note check out how many people die each year due to coal and oil related accidents and illnesses) Did you know that we can create houses that are insulated so well that body heat is sufficient to heat the building in winter (and is so effective at keeping out heat in the summer that no AC is needed)? Did you know that we developed urban planning models for cities vastly more energy and water efficient decades ago (look up Buckminster Fuller if you are curious to see something "only" 40 years out of date), but have never been implemented?
Our world is full of innovations and technologies that are not implemented, but could potentially solve a lot of problems. Most people just don't know about these things, and amongst those that do, most don't care enough to want to try to implement them.
If what I have told you has scared you with the immensity of the size of the problem... well, then that means that I have probably given you a close to accurate projection of just how big that problem really is. But, if no one chooses to fight for what is right... if no one chooses to oppose those who would see things remain as they are (where we continue to waste resources unnecessarily), then nothing will change.
Even if you take nothing else away from this conversation; Remember: Change and Responsibility start with you.
MTF