N. Hemisphere climate may oscillate in future says climate scientist
PAGES Open Science Conference, 10-12 August, Beijing
www.pages2005.org/mediaroom
Beijing, 10 August - The North Atlantic Thermohaline Circulation (THC), the ocean current responsible for the relatively warm climate of much of the Northern Hemisphere, may be in for an oscillating future, says climate scientist Michael Schulz speaking at the PAGES Open Science Conference (www.pages2005.org/) in Beijing this week.
Many scientists are concerned that the THC could slow down or even collapse as a result of future climate change. A slowing of the THC could reduce average temperatures in large parts of the Northern Hemisphere by as much as 10C.
Professor Schulz, from the University of Bremen’s Research Center Ocean Margins in Germany, who has studied the past 50,000 years of THC behaviour, presented data from recent model studies at the PAGES conference today.
“We know that changes in climate in the past have coincided with changes in the strength of the THC and that the THC can oscillate between weaker and stronger states,” he said. “Our model suggests that future climate change may push the THC into an oscillating state that would cause N. hemisphere climate to switch between warmer and cooler conditions over prolonged periods”.
The good news is that a weakened THC may well have the potential to recover. The bad news is that the period of time between weaker and stronger states may be as much as a few thousand years.
Notes for editors and reporters
Michael Schulz spoke on Wednesday 10 August at a conference organised by the Past Global Changes Project (PAGES) of the International Geosphere-Biosphere Programme (IGBP, www.igbp.net).
The mandate of PAGES (www.pages-igbp.org) is to facilitate and support international and interdisciplinary research aimed at understanding the Earth’s past environment in order to make predictions for the future.
To arrange an interview with Professor Schulz, contact Leah Christen (christen@pages.unibe.ch), phone: (+41 31) 312 3133. During the conference: +41 76 307 4474.
More information is available from the conference media room:
www.pages2005.org/mediaroom
“Hockey team” gets together for a friendly game of climate reconstruction
Summary of Panel Discussion
PAGES Open Science Conference, 10-12 August, Beijing
http://www.pages2005.org/mediaroom
World-renowned scientists speaking at a panel discussion at the Past Global Changes (PAGES) conference in Beijing today discussed what is known about climate change over the last 2000 years. Despite debate on the details of the temperature reconstructions, the panel agreed that the increase in temperature in the late 20th century is anomalous in the context of the past 1000-2000 years.
Michael Mann of Pennsylvania State University, Gavin Schmidt of the NASA Goddard Institute for Space Studies, and Dmitry Sonechkin of the Hydro-Meteorological Research Centre of Russia, today went over the state-of-the-art of reconstructing last millennia temperature trends. These reconstructions have often been labelled with the term “hockey stick” and been the subject of heated debate.
The hockey stick term was coined because of the shape of reconstructed mean Northern Hemisphere temperature changes over the past millennium. These curves show cooling from medieval times to the 18th century minimum and then relatively rapid warming since the 19th century.
“This pattern is clearly common to every single proxy and model reconstruction produced, a fact that is often overlooked or ignored by people discussing climate change in the last millennium,” said Heinz Wanner, moderator of the discussion and head of the Swiss Climate Research Center.
Panel members engaged in debate about the advantages and limitations of different scientific methodologies and the varying approaches they each used in their research. Ed Cook of Lamont Doherty Earth Observatory, USA described advances in the analysis of tree ring records that have improved the decadal and centennial accuracy of the reconstructions. Schmidt described the lack of long-term instrumental records as a fundamental problem in calibrating proxy records (e.g. corals, ice cores, lake sediments) of long-term climate variability.
Heinz summed up, “the details may differ but all published reconstructions, not just the curve by Mann et. al, share the basic hockey stick shape,” he said.
See figure appended.
Does this imply that no further effort is needed on improving the temperature reconstructions? Clearly not, say the panel. Climate modeller, Gavin Schmidt, explained that if we want to learn about future climate change in the absence of similar scenarios in the past, we will have to rely on climate model predictions. And the climate models are only as good as their validation. “Validation is best done using paleoclimate reconstructions, especially spatial reconstructions showing global changes, particularly in the southern hemisphere, and not just hemispheric averages,” he said. “The challenge now is to refine the reconstructions and improve the accuracy of models so that we will know with greater certainty what to expect in the future.”
A final suggestion made by Patrick De Deckker, Australian National University, and received with applause was that the scientific community should also focus on more societally relevant reconstructions such as rainfall and regional climate changes.
“The recent debate has been a distraction from more interesting scientific issues,” Schmidt said.
Notes for editors
The panel discussion was organised by the Past Global Changes Project (PAGES) of the International Geosphere-Biosphere Programme (IGBP, www.igbp.net) as part of the PAGES Open Science Conference in Beijing (10-12 August). The panel discussion was held on Wednesday 10 August.
The mandate of PAGES (www.pages-igbp.org) is to facilitate and support international and interdisciplinary research aimed at understanding the Earth’s past environment in order to make predictions for the future.
More information is available from the conference media room:
www.pages2005.org/mediaroom. Contact Leah Christen (christen@pages.unibe.ch), phone: +41 76 307 4474 (text messages only), after 14 August (+41 31) 312 3133.
Images
Comparison of 10 different published reconstructions of mean temperature changes during the last 2000 years. Source Wikipedia (http://en.wikipedia.org/wiki/Image:1000_Year_Temperature_Comparison.png) provided under the GNU Free Documentation License.
Climate change over the last 2000 years—what do we (really) know?
Panel Discussion
PAGES Open Science Conference, 10-12 August, Beijing
In a “warts and all” panel discussion, a group of influential scientists will battle out the myths and realities of what we really know about temperature records since the time of Christ.
The so-called “hockey stick” curve by Michael Mann and others shows global temperature over the past millennium reconstructed from a variety of “proxy” records such as tree rings, ice core samples and corals. The curve underpinned the IPCC’s (Intergovernmental Panel on Climate Change) 2001 Scientific Assessment that formed the basis of the Kyoto Protocol.
Now the curve is the subject of considerable debate and controversy and has been scrutinised by scientists, politicians and sceptics.
Sceptics of human-induced climate change argue that such reconstructions and models can only roughly reproduce the temperature amplitudes and trends of the last two millennia, and thus cannot be relied on for predictions of future climate change.
“This round table will provide an overview on the current state of the discussion in the scientific community and will attempt to assess whether the statements in the IPCC 2001 Scientific Assessment should be modified or not,” says Heinz Wanner, head of the Swiss Climate Research Center and the moderator of the discussion.
“It will also provide an important basis for the ongoing discussions on the future of the Kyoto Protocol, especially regarding the involvement of countries such as the United States, Australia and India,” he said.
The Panel:
Mike Mann (Pennsylvania State University, USA) can be called the father of the "hockey stick". His reconstructions and complementary modelling of the Earth's temperature evolution over the last millennium provided the context for the view that the recent decades' climate change was exceptional and man-made.
Gavin Schmidt (NASA Goddard Institute for Space Studies, New York) is a leading modeller of modern as well as past climate change. He is also very active in disseminating the scientific climate change debate to the public, e.g. via the realclimate.org web blog.
Dmitry Sonechkin (HydroMeteorological Research Centre of Russia, Moscow) is a mathematical climatologist and co-author of the Moberg, et al. 2005 Nature paper that challenged Mann et al.'s low amplitude of climate variability in the pre-industrial millennia.
The moderator:
Heinz Wanner (University of Bern and Swiss Climate Research Center) is a palaeo-meteorologist who uses climatic evidence for the last centuries from historical documents, natural archives, and model simulations to understand the detailed functioning of climate dynamics on hemispheric to regional scales.
The discussion will also involve plenary participants, including many distinguished palaeoscientists from all over the world.
Notes for Editors:
The panel discussion is being organised by the Past Global Changes Project (PAGES) of the International Geosphere-Biosphere Programme (IGBP) as part of the PAGES Open Science Conference in Beijing (10-12 August). The panel discussion will run from 2 pm to 3 pm (local time) on Wednesday 10 August.
The mandate of PAGES is to facilitate and support international and interdisciplinary research aimed at understanding the Earth’s past environment in order to make predictions for the future.
To arrange an interview with Prof. Heinz Wanner or to register your interest in receiving press releases arising from the conference, contact Leah Christen.
Phone until 6 August: (+41 31) 312 3133. From 6-14 August: to be advised.
Past Climates, Environmental Sustainability and Our Future
A Past Global Changes (PAGES) conference
Beijing, China, 10-12 August 2005
“It is only by unravelling the events of the past that we will be able to predict the future, and our place in it, with any confidence,” IGBP Science No. 3.
Evidence is now overwhelming that recent global warming is a consequence of human activities. But these changes are superimposed on natural variations. How can we tell natural change from true contemporary human impact, now and into the future? What can the study of ancient civilizations tell us about our own vulnerability to future environmental change?
At this unique international event, highly regarded Earth scientists from all over the world will meet to discuss the dramatic changes occurring to our home planet and how studying historical times and the recent geologic past can make sense of the present and help predict the future.
“The issues to be raised at the conference are highly relevant to society, as they impact how we perceive environmental change and plan for the future,” said Julie Brigham-Grette, Professor at the University of Massachusetts and Chair of the PAGES project organizing the conference. “Future change will certainly require adaptation and hopefully drive shared political as well as technological innovation across international boundaries. The choices we make now will have long-term implications. We expect the conference to be of great interest to journalists and policy makers, as well as scientists.”
“If we want to comprehend and finally predict future change there is really no alternative but to build on the experiences from past times. That is why this meeting will help shape the global change debate,” added Thorsten Kiefer, Executive Director of PAGES.
Topics will include:
· Is the warming seen in the last decade exceptional or not?
· Climate models: Can they really predict the future?
· How likely is it that the Gulf Stream extension will collapse and freeze Europe?
· Past civilizations and environmental change—fatal mismanagement and far-sighted decisions.
· The Asian Monsoon—what can we expect in the future?
Speakers will include:
· Michael Mann, University of Virginia, USA
· Zhisheng An, Chinese Academy of Sciences, China
· James Shulmeister, University of Canterbury, New Zealand
· Rick Battarbee, University College London, UK
· Gavin Schmidt, NASA Goddard Institute, USA
To arrange an interview with Prof. Brigham-Grette or Dr. Kiefer, or to register your interest in receiving press releases arising from the conference, contact Leah Christen.
Notes for Editors:
PAGES, a core project of the International Geosphere-Biosphere Programme (IGBP), facilitates and supports international and interdisciplinary research aimed at understanding the Earth’s past environment in order to make predictions for the future.
