The atmospheric carbon dioxide concentration has risen from about 280 parts per million by volume (ppmv) to about 360 ppmv in the period from before the Industrial Revolution to the present. This rise of nearly 30% in the atmospheric concentration is a result of emissions of carbon dioxide from human activities, both from combustion of fossil fuels and from the clearing of forested land for agriculture and other uses. Emissions now total about 6 billion tons of carbon per year (GtC/yr). That the rise in concentrations is occurring is confirmed by many types of measurements, including those of the carbon dioxide concentration in the air over the past 40 years and in air bubbles trapped in glacial ice over the past 1,000 years. The figure is from the Working Group I contribution to the IPCC Second Assessment Report (1995).