Global Cooling

Maybe one day warming will cause as many deaths as cooling - the last ice age killed off 70 genera, 7 families and one entire order of life (15,000-8000 BC. Shortly after which, civilization exploded. I guess the only humans left were smart ones). Apart from that, temperature goes up and down all the time on earth. Extinctions are not so bad - they have been happening all the time since the dawn of time. Life will just make new life forms to replace them. It's all part of evolution. Not even really that sad when you think that all of the life forms we try to protect today will be gone in a few million years anyway.