Debate over: Human-induced climate change under way

A study led by PIK scientist Stefan Rahmstorf, published on the same day in the journal Science, indicates that the observed increase of temperatures in the period 1990-2006 is in the upper part of the range projected in the previous IPCC report. The observed increase of sea level even is at the uppermost margin of what IPCC projected.

The new IPCC report was welcomed by Hans Joachim Schellnhuber, Director of PIK and climate advisor of the Federal Government. "With this report, any last doubts should be dispelled that humans are ‘overturning the climate screw’. Hence, we have a responsibility to correct this dangerous development by drastically reducing greenhouse gas emissions."

The IPCC, founded in 1988 by the United Nations and the World Meteorological Organization (WMO), is responsible for compiling the knowledge on climate change documented in thousands of scientific publications worldwide in an objective and transparent way. The IPCC assessments are the result of intensive, carefully conducted review processes and discussions and are internationally acknowledged as the most important and most comprehensive source of information on human-induced climate change. IPCC relies on the research work of more than 600 scientists worldwide. Several scientists from the Potsdam Institute for Climate Impact Research (PIK) have participated as authors, contributors, or expert reviewers.

Schellnhuber, when asked, how the IPCC scenarios can be appraised: "The delinquent is convicted but the 'degree of penalty' is still open." Impor­tant environmental parameters like the development of precipitation and the sea level would still be subject to considerable uncertainties, he reasons.

Stefan Rahmstorf, climate expert at PIK and one of the authors of both the IPCC report and the analysis of latest observational data published concurrently, is particularly con­cerned about the unexpectedly rapid rise of sea level. "Satellite data show that since 1993, sea level has risen by over 4 cm, faster than projected by climate model calculations." Rahmstorf, however, cautioned against premature conclusions. "Whether this observed trend will continue cannot yet be estimated on the basis of the new data." Beside Rahmstorf, the study involved scientists from Australia, France, the United Kingdom, and the United States and has just been published in the online issue of Science.


More information:

IPCC (Intergovernmental Panel on Climate Change) unter

Article: Stefan Rahmstorf, Anny Cazenave, John A. Church, James E. Hansen, Ralph F. Keeling, David E. Parker and Richard C. J. Somerville: Recent Climate Observations Compared to Projections. Science express, 02 Feb. 2007.


Stefan Rahmstorf, Potsdam Institute for Climate Impact Research (PIK), Germany
phone: ++49 331 288 26 24, e-mail:

Press Office at PIK:
Uta Pohlmann
phone: ++49 331 288 25 07, e-mail: