A team of scientists headed by Professor Johan Rockstrom, a leading scientist on global sustainability, proposed the framework of 9 planetary boundaries. This defines safe operating zones for humanity to safeguard our planet’s diverse ecosystems. These boundaries mark the threshold between sustainable and unsustainable use of natural processes. Today 6 of these boundaries have already been exceeded, with catastrophic effects. Furthermore, there is the possibility of reaching a number of climate tipping points when these boundaries are exceeded. The first is expected to be the bleaching of the tropical coral reefs, and consequently the devastation of many ecosystems. This chapter outlines the effect of global warming and highlights the primary sources of greenhouse gases.