Global warming

Not cool anymore

Thorsten Kiefer on how the world turned cooler, then suddenly warmer again

Global temperatures have increased over the last decades. Instrumental temperature measurements leave no room for qualified doubt about this observation, but reach back no more than a century and half. This length of time is insufficient to assess, for example, how Earth's climate varied in pre-industrial times. Yet, long-term records are essential if we are to understand climate variability and to isolate the effects of natural and human drivers.

With this in mind, a global network of scientists have reconstructed and analyzed the climate of the last two millennia at a regional scale. A first set of temperature reconstructions based on more than 500 sites worldwide reveals substantial variability through time, but also between regions.

Accordingly, the data showed no globally synchronous warm or cold intervals that would define a worldwide Medieval Climate Anomaly or Little Ice Age. On the other hand, robust features include a millennial-scale cooling trend across almost all regions, reversed by the warming measured over the last few decades.

The seminar discussed in detail the regional temperature histories and their implications, and demonstrate the virtues of concerted data syntheses by international communities.

About Thorsten Kiefer
Thorsten Kiefer is the Executive Director of IGBP's Past Global Changes project (PAGES), located at the University of Berne in Switzerland. The scope of PAGES covers science that uses pre-instrumental evidence to investigate environmental and climatic changes, natural and anthropogenic, over the past hundreds to millions of years.

Thorsten Kiefer's roots as a researcher were at the Universities of Kiel, Germany, and Cambridge, UK, where he analyzed deep-sea sediments for information on past changes in ocean circulation and hydrology. Kiefer is also currently serving as the co-chief-editor of Climate of the Past, an open-access and open-review journal of the European Geosciences Union.

Stockholm seminars

Share

Stockholm Resilience Centre is a collaboration between Stockholm University and the Beijer Institute of Ecological Economics at the Royal Swedish Academy of Sciences

Stockholm Resilience Centre
Stockholm University, Kräftriket 2B
SE-10691
Phone: +46 8 674 70 70
info@stockholmresilience.su.se

Organisation number: 202100-3062
VAT No: SE202100306201