Black carbon, or simply soot emitted by fires, poses a serious threat to the climate. The wind carries soot over great distances: it burns, say around Lake Baikal, and soot can settle on ice in the Arctic. The ice cap in the Arctic is a kind of planetary air conditioner that prevents it from overheating. When the ice is clean and white, the sun's rays are reflected from it, and it does not melt as quickly. When soot settles on ice, it blackens, this reduces its ability to reflect the sun's rays and accelerates melting.