Is the Current Climate Change Unusual Compared to Earlier Changes in Earth’s History?
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 has changed on all time scales throughout Earth’s history. Some aspects of the current climate change are not unusual, but others are. The concentration of CO2 in the atmosphere has reached a record high relative to more than the past half-million years, and has done so at an exceptionally fast rate. Current global temperatures are warmer than they have ever been during at least the past five centuries, probably even for more than a millennium. If warming continues unabated, the resulting climate change within this century would be extremely unusual in geological terms. Another unusual aspect of recent climate change is its cause: past climate changes were natural in origin (see FAQ 6.1), whereas most of the warming of the past 50 years is attributable to human activities.
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