Sven-Erik writes "Due to subtle variations in the Earth's orbit, researchers have calculated that the next Ice Age is due within 1,500 years. However, a new study suggests greenhouse gas emissions mean it will not happen that soon (abstract). 'Dr Skinner's group ... calculates that the atmospheric concentration of CO2 would have to fall below about 240 parts per million (ppm) before the glaciation could begin. The current level is around 390ppm. Other research groups have shown that even if emissions were shut off instantly, concentrations would remain elevated for at least 1,000 years, with enough heat stored in the oceans potentially to cause significant melting of polar ice and sea level rise.'"