Figure 1. Characteristics of the proxies.
A) Map of the proxies used. B) Number of proxy series available as a function of the year, from 600 to 2007.
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.