Upgrade to access all content for this subject
"The Proof Is in the Atmosphere." The Proof Is in the Atmosphere. U.S. EPA, n.d. Web. 28 Mar. 2016. https://www3.epa.gov/climatechange/kids/scientists/proof.html.
According to the graph above, current atmospheric carbon dioxide levels are now ____% higher than any time period in the last 700,000 years.