With snow on the ground, many people will have been huddling around a wood fire, but researchers are questioning if wood burning is really climate neutral. Burning wood is not CO2 free; it releases carbon, stored over the previous decades, in one quick burst. For an equal amount of heat or electricity, it releases more CO2 than burning gas, oil and even coal, so straight away we have more CO2 in the air from burning wood. This should be reabsorbed as trees regrow. For logs from mature Canadian woodland, it could take more than 100 years before the atmospheric CO2 is less than the alternative scenario of burning a fossil fuel and leaving the trees in the forest.