An official website of the United States government. Here's how you know
Official websites use .gov

A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS

A lock () or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Federal Bureau of Investigation Federal Bureau of Investigation

Figure 2

Figure 2: Average annual atmospheric 14CO2 record for the Northern Hemisphere. Annual averaging smoothes the curve and reduces the 1963 peak.

Figure 2 shows the average annual atmospheric <sup>14</sup>CO<sub>2</sub> record for the Northern Hemisphere14CO2 record for the Northern Hemisphere">
Source: Adapted from Levin and Kromer 2004 and Stuiver et al. 1998a.