What Caused the Ice Ages and Other Important Climate Changes Before the Industrial Era?

FAQ 6.1

Please note that this material is from the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), published in 2007. The latest climate science can be found inthe IPCC’s 6th Assessment Report, published in August 2021. For other reports and further updates, please refer to theIPCC website.

This material is extracted from the Frequently Asked Questions (FAQs) section of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), Working Group 1 (see full reference below).

Climate on Earth has changed on all time scales, including long before human activity could have played a role. Great progress has been made in understanding the causes and mechanisms of these climate changes. Changes in Earth’s radiation balance were the principal driver of past climate changes, but the causes of such changes are varied. For each case – be it the Ice Ages, the warmth at the time of the dinosaurs or the fluctuations of the past millennium – the specific causes must be established individually. In many cases, this can now be done with good confidence, and many past climate changes can be reproduced with quantitative models.

FAQ 6.1, Figure 1. Schematic of the Earth’s orbital changes (Milankovitch cycles) that drive the ice age cycles. ‘T’ denotes changes in the tilt (or obliquity) of the Earth’s axis, ‘E’ denotes changes in the eccentricity of the orbit (due to variations in the minor axis of the ellipse), and ‘P’ denotes precession, that is, changes in the direction of the axis tilt at a given point of the orbit. Source: Rahmstorf and Schellnhuber (2006).

Reference

IPCC, 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment, Report of the Intergovernment Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

For a more detailed explanation of the answer please see the original IPCC FAQ document at:http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-faqs.pdf

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