{"id":3146,"date":"2015-05-20T10:18:53","date_gmt":"2015-05-20T14:18:53","guid":{"rendered":"http:\/\/site.extension.uga.edu\/climate\/?p=3146"},"modified":"2015-05-20T10:19:10","modified_gmt":"2015-05-20T14:19:10","slug":"how-do-we-know-the-climate-of-the-past","status":"publish","type":"post","link":"https:\/\/site.extension.uga.edu\/climate\/2015\/05\/how-do-we-know-the-climate-of-the-past\/","title":{"rendered":"How do we know the climate of the past?"},"content":{"rendered":"

Historical records of climate have only been around for about 150 years, although there are a few earlier records. \u00a0Yet climatologists often talk about the climate hundreds and even millions of years ago? \u00a0How do they know what the climate was long before weather instruments were available? \u00a0The key is the use of what we call “proxy data”. \u00a0Proxy data are records of things that are affected by climate in such a way that we can deduce what the climate was like. \u00a0They include phenological data like the first flower of the year, cores from glacial ice and lake and ocean sediments, and landform evidence like glacial moraines.<\/p>\n

One example of the use of proxy data is “dendrochronology”, the study of tree rings. \u00a0Trees show alternations in ring width that are related to temperature and precipitation patterns. \u00a0We can look at the tree rings of modern trees and see how the ring pattern changes depending on the climate patterns during the tree’s lifetime. \u00a0Thin rings mean that growth was slow due to cold conditions \u00a0or drought, and thick rings mean the tree was growing well with good temperature and rainfall conditions.<\/p>\n

For longer time periods, cores from lakes, glaciers, and the Greenland and Antarctic ice caps can provide pictures of climate which go back hundreds of thousands of years. \u00a0The second figure below shows some of the time spans that can be studied using each type of proxy data. \u00a0Yahoo News had a story<\/a> this week about the record of carbon dioxide measured from bubbles in an ice core taken from Antarctica. \u00a0The story describes how the gas bubbles are measured to see how the atmospheric composition changed over time and how scientists use this information to determine past climates.<\/p>\n

\"tree<\/a>\u00a0\u00a0\"proxy<\/a>\u00a0\u00a0\"ice<\/a><\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

Historical records of climate have only been around for about 150 years, although there are a few earlier records. \u00a0Yet climatologists often talk about the climate hundreds and even millions of years ago? \u00a0How do they know what the climate was long before weather instruments were available? \u00a0The key is the use of what we […]<\/p>\n","protected":false},"author":58,"featured_media":3149,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5,16],"tags":[],"class_list":["post-3146","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-climate-and-ag-in-the-news","category-climate-science"],"_links":{"self":[{"href":"https:\/\/site.extension.uga.edu\/climate\/wp-json\/wp\/v2\/posts\/3146","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/site.extension.uga.edu\/climate\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/site.extension.uga.edu\/climate\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/site.extension.uga.edu\/climate\/wp-json\/wp\/v2\/users\/58"}],"replies":[{"embeddable":true,"href":"https:\/\/site.extension.uga.edu\/climate\/wp-json\/wp\/v2\/comments?post=3146"}],"version-history":[{"count":1,"href":"https:\/\/site.extension.uga.edu\/climate\/wp-json\/wp\/v2\/posts\/3146\/revisions"}],"predecessor-version":[{"id":3150,"href":"https:\/\/site.extension.uga.edu\/climate\/wp-json\/wp\/v2\/posts\/3146\/revisions\/3150"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/site.extension.uga.edu\/climate\/wp-json\/wp\/v2\/media\/3149"}],"wp:attachment":[{"href":"https:\/\/site.extension.uga.edu\/climate\/wp-json\/wp\/v2\/media?parent=3146"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/site.extension.uga.edu\/climate\/wp-json\/wp\/v2\/categories?post=3146"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/site.extension.uga.edu\/climate\/wp-json\/wp\/v2\/tags?post=3146"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}