evidence: Antarctic ice cores show us that the concentration of CO2 was stable over the last millennium until the early 19th century. It then started to rise, and its concentration is now nearly 50% higher than it was before the industrial revolution (Fig. 2). Other measurements that can fingerprint the source of this CO2 (e.g. isotopic data) confirm that the increase must be due to emissions from fossil fuel usage and human-induced changes vegetation and soils. Measurements from older ice cores (discussed below) confirm that both the magnitude and rate of the recent increase are almost certainly unprecedented over the last 800,000 years (Fig. 2). The fastest natural increase measured in older ice cores is around 15ppm (parts per million) over about 200 years. For comparison, atmospheric CO2 is now rising 15ppm every 6 years. Methane (CH4), another important greenhouse gas, also shows an unprecedented increase in concentration over the last two centuries. Its concentration is now much more than double its pre-industrial level. This is mainly due to emissions from agricultural sources and fossil fuel production, that comes on top of natural emissions from wetlands and other sources. [...] - Atmospheric carbon dioxide levels are now 50% higher than before the industrial revolution. This increase is due to fossil fuel usage and changes in land-use. - The magnitude and rate of the recent increase are almost certainly unprecedented over the last 800,000 years.