The following is a graph showing temperture changes during the last 450,000 years. The data was derived from ice cores taken from the Antarctic Ice Sheet. The data is considered reliable because it correlates with temperature calculations from other sources, such as ocean and lake sediments, tree growth rings, and fossil evidence. What is immediately obvious is the Earth's climate is continually changing, in ways comparable to what we are seeing today. Long, long before we began burning fossil fuels.
Global temperature variation for the past 425,000 years. The present is at the right. The horizontal 0 line represents the 1961-1990 average global temperature. The numbers on the left show the variation from that baseline in °C.
The data were derived from an analysis of ice cores taken at the Vostok station in Antarctica. Find out more about how temperature estimates are made from proxy data.
Image based on data from the National Oceanographic and Atmospheric Administration.
The present day is at the far right of the chart. What do we see? First of all, there’s quite a bit of fluctuation. There are long periods of time when the average global temperature was as much as 9°C colder than now. These were Ice Ages. Much of the northern part of the world was covered with thick sheets of ice, much like we see today in Greenland and Antarctica. The most recent Ice Age ended about 12,000 years ago. There were also times when it was warmer than today. On the whole, we are in a relatively warm period. What causes these changes in climate? There are many factors. Find out more…