Re: global warming and the lightweight lifestyle, the notion of Pascal's Wager comes to mind. To wit, that the expected value of believing (in god, as the wager goes) is always greater than the expected value of not believing.
If we choose to believe that global warming (and the net long-term negative impact of humanity on planet earth) is real and consequential, and if we, individually, take measures to address it (ie, by living a "lightweight lifestyle"), then the result is that we benefit both ourselves and the planet regardless of future outcomes had we chosen not to believe or to act.
But there's also a more sharply defined advantage to living simply, particularly as it relates to the skills we develop in order to, and as a result of, living with less. In Pascal's Wager, believing is at its least a harmless and contrived conviction, and at best it gets him to heaven. For us, today, believing in and following a simpler lifestyle is also a form of life insurance. It can increase our own individual odds of survival in the face of climate change and the "sudden" disasters it may spawn.
Planet Earth will almost certainly host life for a few more billion years. The life forms that hang around through and beyond humanity's growing crisis will be the Adapted Ones. And each of us, individually, has the power to adapt. Our power is our intelligence. On the grand scale, our collective power will always work both for us and against us, and chaos may rule. But individually, we have a choice in how we use our power. And so I say, choose wisely - for the planet, certainly, but also for you.