Global Temperature â¦ In between ice ages, some lesser peaks of temperature have occurred a number of times, especially around 125,000 years ago. 80 records span â¦ 6,000 years of climate history: An ancient lake has yielded its secrets ... refers to the past 11,700 years or so of Earth's history. The above chart shows the relative changes in global average temperature, CO2 (carbon dioxide), and sea level over the last 420,000 years. The shortest record covers just 50 years, but, the longest record provided data that covers the last 2,000 years. But as the Pleistocene era drew to a close 10,000 to 15,000 years ago, megafauna like mammoths and saber-toothed cats began to go extinct. Global temperatures reconstructed by averaging well-dated, calibrated proxy temperature records from around the world, mostly from ocean margin sediment cores, in addition to lake and ice cores on land. Many estimates of past temperatures have been made over Earth's history.The field of paleoclimatology includes ancient temperature records. These climate changes have often had profound effects on human cultures and societies. In the last 600 million years of Earthâs history only the Carboniferous Period and our present age, the Quaternary Period, have witnessed CO2 levels less than 400 ppm.. A new study paints a picture of an Earth that is warmer than it has been in about 120,000 years, and is locked into eventually hitting its hottest mark in more than 2 million years. This article was first published in August 2014, and it has been updated to include new research published since then. 20,000 years ago - 2,000 years ago. In the last millions years Earth's climate has alternated between ice ages lasting about 100,000 years and interglacial periods of 10,000 to 15,000 years. This article is one of a two-part series on past temperatures, including how warm the Earth has been âlately.â. Human societies have experienced climate change since the development of agriculture some 10,000 years ago. Climate change since the emergence of civilization. Graphs of global temperature data over the last 2,000 years. At the bottom of this page, there is a link to download a PDF of this graph â which may be used on the condition that it is presented as is, WITHOUT MODIFICATION.