Rem sleep ends when there is an increase in the level of serotonin and norepinephrine secreted.<span />
Fossil fuels are NONRENEWABLE resources !!
The ice-covered polar regions are colder than other places on earth, due in part to the high albedo of the snow and ice cover. The dark particles land on snow and ice, and decrease albedo. The darkened snow and ice absorb more radiation than pure snow and ice.