The encyclical letter Laudato Si is available here on the Vatican website.
212. We must not think that these efforts are not going to change the world. They benefit society, often unbeknown to us, for they call forth a goodness which, albeit unseen, inevitably tends to spread. Furthermore, such actions can restore our sense of self-esteem; they can enable us to live more fully and to feel that life on earth is worthwhile.
Modern rationalism would inform us that one person turning off the lights doesn’t impact much when seven billion others leave theirs on. But this brief section is typically Ignatian. It implies a start. It trusts in the power of good example. It also inspires self-confidence to continue the program. The convert one needs to make is oneself, not seven billion.