The other day, I saw, "The Nature of Things" narrated by David Suzuki.
It was an interesting episode.
This episode talked about, our own planet Earth. How, the Earth evolved over time and what were we made of. It had a lot of information about what creatures are there and how life works.
Anyways, there was a section of the show that really interested me. There was this part about microbes that didn't need oxygen to survive. They lived by taking the nutrients from rocks and minerals. This was the supposed first life. Evolution occurred when certain cells were exposed to sunlight, they began to change and adapt to more plant like cells that use photosynthesis. From there everything expanded and what not. Then there was this blue-green algae stuff that was sort of derived from the microbes. It was an algae that would live without oxygen. If this algae were exposed to oxygen, it would almost instantly die. This algae would grow in warmer waters because warmer waters have less oxygen. The way they would grow is if the water became still. With no movement of the water, less oxygen and cool air would be in the water. When this happens, the algae begins to grow, and it covers everything, and everything alive instantly, killing anything.
Okay, so your probably wondering, "What the heck does this have to do with anything?". Well, you know how the ice caps are melting? If this happens, less cool water is there. Waters will warm up, and the natural wave circulation that prevents the algae growth will stop. If the waters become warm and the currents stop, the algae will grow, wiping out everything. That means, we won't be able to survive because there would be no safe water.
Therefore blue-green algae = end of world.