http://www.grida.no/publications/vg/climate/page/3057.aspx http://www.grida.no/publications/vg/climate/page/3057.aspx http://www.grida.no/publications/vg/climate/page/3057.aspx http://www.grida.no/publications/vg/climate/page/3057.aspx Introduction to Climate Change 40000 years of ice core samples and their carbon emissions http://www.grida.no/publications/vg/climate/page/3057.aspx http://www.grida.no/publications/vg/climate/page/3057.aspx CO2 concentration Introduction to Climate Change