… is the question people have been putting a lot of thought into since the IPCC AR4 report came out. We analysed what was in the report quite carefully at the time and pointed out that the allowance for dynamic ice sheet processes was very uncertain, and actually precluded setting a upper limit on what might be expected. The numbers that appeared in some headlines (up to 59 cm by 2100) did not take that uncertainty into account.
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Last week we proposed a bet against the “pause in global warming” forecast in Nature by Keenlyside et al. and we promised to present our scientific case later – so here it is.
By Stefan Rahmstorf, Michael Mann, Ray Bradley, William Connolley, David Archer, and Caspar Ammann
Global cooling appears to be the “flavour of the month”. First, a rather misguided media discussion erupted on whether global warming had stopped, based on the observed temperatures of the past 8 years or so (see our post). Now, an entirely new discussion is capturing the imagination, based on a group of scientists from Germany predicting a pause in global warming last week in the journal Nature (Keenlyside et al. 2008).
Specifically, they make two forecasts for global temperature, as discussed in the last paragraphs of their paper and shown in their Figure 4 (see below). The first forecast concerns the time interval 2000-2010, while the second concerns the interval 2005-2015 (*). For these two 10-year averages, the authors make the following prediction:
“… the initialised prediction indicates a slight cooling relative to 1994-2004 conditions”
Their graph shows this: temperatures in the two forecast intervals (green points shown at 2005 and 2010) are almost the same and are both lower than observed in 1994-2004 (the end of the red line in their graph).
New York Times, BBC News, Reuters, Bloomberg and so on), because of its seeming contradiction with global warming. The authors emphasise this aspect in their own media release, which was titled: Will Global Warming Take a Short Break?
That this cooling would just be a temporary blip and would change nothing about global warming goes without saying and has been amply discussed elsewhere (e.g. here). But another question has been rarely discussed: will this forecast turn out to be correct?
We think not – and we are prepared to bet serious money on this. We have double-checked with the authors: they say they really mean this as a serious forecast, not just as a methodological experiment. If the authors of the paper really believe that their forecast has a greater than 50% chance of being correct, then they should accept our offer of a bet; it should be easy money for them. If they do not accept our bet, then we must question how much faith they really have in their own forecast.
The bet we propose is very simple and concerns the specific global prediction in their Nature article. If the average temperature 2000-2010 (their first forecast) really turns out to be lower or equal to the average temperature 1994-2004 (*), we will pay them € 2500. If it turns out to be warmer, they pay us € 2500. This bet will be decided by the end of 2010. We offer the same for their second forecast: If 2005-2015 (*) turns out to be colder or equal compared to 1994-2004 (*), we will pay them € 2500 – if it turns out to be warmer, they pay us the same. The basis for the temperature comparison will be the HadCRUT3 global mean surface temperature data set used by the authors in their paper.
To be fair, the bet needs an escape clause in case a big volcano erupts or a big meteorite hits the Earth and causes cooling below the 1994-2004 level. In this eventuality, the forecast of Keenlyside et al. could not be verified any more, and the bet is off.
The bet would also need a neutral arbiter – we propose, for example, the director of the Hadley Centre, home of the data used by Keenlyside et al., or a committee of neutral colleagues. This neutral arbiter would also decide whether a volcano or meteorite impact event is large enough as to make the bet obsolete.
We will discuss the scientific reasons for our assessment here another time – first we want to hear from Keenlyside et al. whether they accept our bet. Our friendly challenge is out – we hope they will accept it in good sportsmanship.
(*) We adopt here the definition of the 10-year intervals as in their paper, which is from 1 November of the first year to 31 October of the last year. I.e.: 2000-2010 means 1 November 2000 until 31 October 2010.
Update: We have now published part 2 of this bet with our scientific arguments.
In January, we presented Lesson 1 in model-data comparison: if you are comparing noisy data to a model trend, make sure you have enough data for them to show a statistically significant trend. This was in response to a graph by Roger Pielke Jr. presented in the New York Times Tierney Lab Blog that compared observations to IPCC projections over an 8-year period. We showed that this period is too short for a meaningful trend comparison.
This week, the story has taken a curious new twist. In a letter published in Nature Geoscience, Pielke presents such a comparison for a longer period, 1990-2007 (see Figure). Lesson 1 learned – 17 years is sufficient. In fact, the very first figure of last year’s IPCC report presents almost the same comparison (see second Figure).
[Read more…] about Model-data-comparison, Lesson 2
Knud Jahnke and Rasmus Benestad
After having watched a new documentary called the ‘Cloud Mystery’ – and especially the bit about the galaxy (approximately 2 – 4 minutes into the linked video clip) – we realised that a very interesting point has been missed in earlier discussions about ‘climate, galactic cosmic rays and the evolution of the Milky Way galaxy.
It is claimed in ‘The Cloud Mystery’, the book ‘The Chilling Stars’, and related articles that our solar system takes about 250 million years to circle the Milky Way galaxy and that our solar system crosses one of the spiral arms about every ~150 million years (Shaviv 2003).
But is this true? Most likely not. As we will discuss below, this claim is seriously at odds with astrophysical data.
[Read more…] about A Galactic glitch
Gavin Schmidt and Stefan Rahmstorf
John Tierney and Roger Pielke Jr. have recently discussed attempts to validate (or falsify) IPCC projections of global temperature change over the period 2000-2007. Others have attempted to show that last year’s numbers imply that ‘Global Warming has stopped’ or that it is ‘taking a break’ (Uli Kulke, Die Welt)). However, as most of our readers will realise, these comparisons are flawed since they basically compare long term climate change to short term weather variability.
This becomes immediately clear when looking at the following graph:
This post is a list of books since 2005 (in reverse chronological order) that we have been involved in, accompanied by the publisher’s official description, and some comments of independent reviewers of the work. We will try and keep this list up to date as and when new books appear. We have also added links to the sidebar with the latest offerings.
- The Hockey Stick and the Climate Wars: Dispatches from the Front Lines, Michael Mann, Columbia University Press.
- Global warming: Understanding the Forecast, Second Edition, David Archer, Wiley (2011).
- Global Warming and Political Intimidation, by Raymond Bradley, University of Massachusetts Press (2011).
- The Warming Papers: The Scientific Foundation for the Climate Change Forecast, by David Archer and Ray Pierrehumbert, Blackwell / Wiley (2010).
- The Global Carbon Cycle: Princeton Primers in Climate, by David Archer, Princeton University Press (2010).
- Principles of Planetary Climate by Ray Pierrehumbert. (Cambridge University Press, 2010)
- The Climate Crisis: An Introductory Guide to Climate Change. David Archer and Stefan Rahmstorf, Cambridge University Press (2010). An unofficial guidebook to the IPCC Fourth Assessment Report.
- Our Threatened Oceans Stefan Rahmstorf and K. Richardson (2008)
- Climate Change: Picturing the Science. Gavin Schmidt and Joshua Wolfe, W.W. Norton (2009)
- The Long Thaw: How Humans are Changing the Next 100,000 Years of Earth’s Climate. David Archer, Princeton University Press (2009)
- Dire Predictions: Understanding Global Warming Michael Mann and Lee Kump, DK/Pearson (2008)
- Wie bedroht sind die Ozeane? Stefan Rahmstorf and K. Richardson (2007, in German)
- Global warming: Understanding the Forecast, David Archer (2006)
- Der Klimawandel Diagnose, Prognose, Therapie, Stefan Rahmstorf and H. J. Schellnhuber (2006, in German, Korean, Vietnamese; Arabic version forthcoming)
- Solar Activity and Earth’s Climate, Rasmus Benestad (2006, 2nd Edition)
- Paleoclimatology: Reconstructing Climates of the Quaternary, Ray Bradley (2005, 2nd Edition)
In its 2001 report on global climate, the Intergovernmental Panel on Climate Change of the United Nations prominently featured the “Hockey Stick,” a chart showing global temperature data over the past one thousand years. The Hockey Stick demonstrated that temperature had risen with the increase in industrialization and use of fossil fuels. The inescapable conclusion was that worldwide human activity since the industrial age had raised CO2 levels, trapping greenhouse gases in the atmosphere and warming the planet.
The Hockey Stick became a central icon in the “climate wars,” and well-funded science deniers immediately attacked the chart and the scientists responsible for it. Yet the controversy has had little to do with the depicted temperature rise and much more with the perceived threat the graph posed to those who oppose governmental regulation and other restraints to protect our environment and planet. Michael E. Mann, lead author of the original paper in which the Hockey Stick first appeared, shares the real story of the science and politics behind this controversy. He introduces key figures in the oil and energy industries, and the media front groups who do their bidding in sometimes slick, bare-knuckled ways to cast doubt on the science. Mann concludes with an account of the “Climategate” scandal, the 2009 hacking of climate scientists’ emails. Throughout, Mann reveals the role of science deniers, abetted by an uninformed media, in once again diverting attention away from one of the central scientific and policy issues of our time.
The Climate Crisis: An Introductory Guide to Climate Change. David Archer and Stefan Rahmstorf, Cambridge University Press, 2010.
This book provides a concise and accessible overview of what we know about ongoing climate change and its impacts, and what we can do to confront the climate crisis. Highly illustrated in full colour, it lucidly presents information contained in the Intergovernmental Panel on Climate Change reports, making essential scientific information on this critical topic available to a broad audience.
David Archer and Stefan Rahmstorf – two outstanding scientists – bring us up-to-date on climate science in this remarkable and very readable book. This book deserves to be read by anyone interested in climate change.
–Paul Crutzen, Max Plank Institute for Chemistry, winner of the Nobel Prize for Chemistry for explaining the ozone hole
The key findings of the IPCC, written in plain and simple terms. Great value in informing the public at large about the science underlying the growing challenge of climate change.
-Rajendra Pachauri, Chairman of the IPCC and Director-General of The Energy Resources Institute
They are excellent communicators of the science to the general reader… One hopes for a wide readership for this measured book which clearly and thoughtfully sets out the results of the work of a great many scientists.
– Bryan Walker, Hot Topic, 19 January 2010
“Climate Change: Picturing the Science is a tour de force of public education. It is simply the best available collection of essays by climate scientists on the nature of human-induced climate change, the ways scientists have come to understand and measure the risks that it poses, and the options that we face….The editors, climatologist Gavin Schmidt and photographer Joshua Wolfe, have produced a collection of essays of uniformly outstanding quality, supported by photographs of beauty and insight.”
-Jeffrey D. Sachs
Director, Earth Institute at
An unprecedented union of scientific analysis and stunning photography illustrating the effects of climate change on the global ecosystem.
In this groundbreaking book, published by W.W. Norton & Company in April 2009 NASA climate scientist Gavin Schmidt and photographer Joshua Wolfe illustrate as never before the ramifications of shifting weather patterns for human society. Photographic spreads show us retreating glaciers, sinking villages in Alaska’s tundra, drying lakes. The text follows adventurous scientists through the ice caps at the poles to the coral reefs of the tropical seas. Marshalling data spanning centuries and continents, the book affirms the headlines with cutting-edge research and visual records, including contributions from experts on atmospheric science, oceanography, paleoclimatology, technology, politics, and the polar regions.
Global warming is usually represented as a hundred-year problem, say to the year 2100. In The Long Thaw, David Archer, one of the world’s leading climatologists, shows how a few centuries of fossil-fuel use will change the climate of the Earth dramatically for hundreds of thousands of years into the future. The great ice sheets in Antarctica and Greenland will take more than a century to melt, we think, but the climate impact from fossil fuel CO2 will last long enough for the ice sheets to respond fully to the warmer climate, changing sea level one hundred times more than the forecast for the year 2100. A planet-wide thaw driven by humans has already begun, but Archer argues that it is still not too late to avert dangerous climate change—if humans can find a way to cooperate as never before.
In this short book, David Archer gives us the latest on climate change research, and skillfully tells the climate story that he helped to discover: generations beyond our grandchildren’s grandchildren will inherit atmospheric changes and an altered climate as a result of our current decisions about fossil-fuel burning. Not only are massive climate changes coming if we humans continue on our current path, but many of these changes will last for millennia. To make predictions about the future, we rely on research into the deep past, and Archer is at the forefront of this field: paleoclimatology. This is the book for anyone who wishes to really understand what cutting-edge science tells us about the effects we are having, and will have, on our future climate.
Richard B. Alley, Penn State University
This is the best book about carbon dioxide and climate change that I have read. David Archer knows what he is talking about
James Hansen, NASA
Books on climate change tend to focus on what is expected to happen this century, which will certainly be large, but they often neglect the even larger changes expected to take place over many centuries. The Long Thaw looks at climate effects beyond the twenty-first century, and its focus on the long-term carbon cycle, rather than just climate change, is unique.
Jeffrey T. Kiehl, NCAR
A great book. What sets it apart is that it expands the discussion of the impacts of global warming beyond the next century and convincingly describes the effects that are projected for the next few thousand years. What also sets it apart is how deeply it takes general readers into the scientific issues of global warming by using straightforward explanations of often complex ideas.
Peter J. Fawcett, University of New Mexico
Archer has perfectly pitched answers to the most basic questions about global warming while providing a sound basis for understanding the complex issues frequently misrepresented by global warming skeptics. With a breezy, conversational style, he . . . provides a complete picture of climate change.
[An] enjoyable and fast-paced treatise. . . . Archer leads the reader to a simple yet accurate picture of climate changes, ranging from geological time scales to current warming, ice ages and prospects for the future.
—Susan Solomon, Nature
The Intergovernmental Panel on Climate Change (IPCC) has been issuing the essential facts and figures on climate change for nearly two decades. But the hundreds of pages of scientific evidence quoted for accuracy by the media and scientists alike, remain inscrutable to the general public who may still question the validity of climate change.
Esteemed climate scientists Michael E. Mann and Lee R. Kump, have partnered with DK Publishing to present Dire Predictions–an important book in this time of global need. Dire Predictions presents the information documented by the IPCC in an illustrated, visually-stunning, and undeniably powerful way to the lay reader. The scientific findings that provide validity to the implications of climate change are presented in clear-cut graphic elements, striking images, and understandable analogies.
Readers will be able to understand the IPCC reports’ key concepts such as scientific uncertainty. They will also learn how to build a climate model and use it to predict future climates. Geoforensics is presented as a way to learn from the past by piecing together clues from prior climates.
Here’s a powerful, straight-forward guide to how scientists, economists, and engineers really understand the problem of global warming. It makes 20 years of research and consensus-building completely accessible to anyone who cares to know the truth–and to do something about it.
Bill McKibben, author of “The End of Nature”
With its eye-grabbing graphics and reader-friendly prose, “Dire Predictions” walks us through the findings of the world’s leading climate scientists – and places the ultimately responsibility for the human future directly at our feet.
Ross Gelbspan, author of “The Heat Is On” and “Boiling Point”
Dire Predictions is a must read for anyone who wants the straight facts on global warming. It cuts to the heart of the massive 2007 IPCC report, presenting major scientific findings in easy to understand language and graphics. Written by two of the scientific community’s most thoughtful researchers, Dire Predictions’ unbiased message about global warming arrives at a time when people need it most!
Dr. Heidi Cullen, Climate Expert at “The Weather Channel”
Wie bedroht sind die Ozeane?, Stefan Rahmstorf and K. Richardson, (Fischer 2007, in German, English version published 2008)
Die Meere sind eine Grundlage unseres Lebens — sie regulieren unser Klima und sind ein wichtiger Nahrungslieferant. Doch wir zerstören sie durch globale Erwärmung, Überfischung und Verschmutzung. Das wird verheerende Folgen haben, wenn wir nicht rasch umdenken und handeln. Dieser Band zeigt Ansätze auf, wie wir unsere ozeanischen Ökosysteme wirkungsvoll schützen können.
Global Warming: Understanding the Forecast is a comprehensive introduction to all aspects of global warming. Written in an accessible way, this important book examines the processes of climate change and climate stability, from the distant past to the distant future. Examining the greenhouse effect, the carbon cycle, and what the future may hold for global climate, this text draws from a wide range of disciplines, and not only summarizes scientific evidence, but also economic and policy issues, related to global warming. A companion website provides access to interactive computer models of the physics and chemistry behind the global warming forecast, which can be used to support suggested student projects included at the end of each chapter. Global Warming: Understanding the Forecast provides an essential introduction to this vital issue for both students and general readers, with or without a science background.
Rigorous but rewarding, David Archer’s book takes us through the science of global warming so that we can more effectively assess where the world may be heading.
Andrew S. Goudie, University of Oxford
David Archer’s book is an accessible, entertaining, but detailed account of how scientists are trying to predict future climate change. It is an excellent book and should be the first port of call for anyone wanting to delve deeper into exactly what goes into those global warming forecasts.
Mark Maslin, University College London, author of Global Warming: A Very Short Introduction
This is a wonderful book. Between the covers of a surprisingly slim paperback, David Archer has distilled nearly everything a concerned undergraduate student could wish to know about the workings of the climate system…overall, this book perfectly hits its target audience.
Keith Alverson, Intergovernmental Oceanographic Commission of UNESCO, Environmental Conservation
The main purpose of this book is to introduce the reader to the subject of solar activity and the connection with Earth’s climate. It commences with a brief review of the historical progress on the understanding of the solar-terrestrial connection and moves on to an objective scrutiny of the various hypothesis. The text focuses on how knowledge about the solar cycle and Earth’s climate is obtained. It includes discussion of observations, methods and the physics involved, with the necessary statistics and analysis also provided, including an examination of empirical relations between sunspots and the Earth’s climate. The author reviews plausible physical mechanisms involved in any links between the solar cycle and the Earth’s climate, emphasizing the use of established scientific methods for testing hypothesized relationships.
Der Klimawandel Diagnose, Prognose, Therapie, S. Rahmstorf and H. J. Schellnhuber (2006) (in German, Korean, Vietnamese; Arabic version forthcoming)
“In dem Buch “Klimawandel” in der Reihe “Wissen” des C.H. Beck Verlages melden sich zwei ausgewiesene Fachleute zu Wort: Hans-Joachim Schellnhuber ist Gründer und Direktor des Potsdam-Instituts für Klimafolgenforschung und Professor für Theoretische Physik an der Universität Potsdam. Stefan Rahmstorf forscht am Potsdam-Institut für Klimafolgenforschung und ist Professor für Physik der Ozeane an der Universität Potsdam. Auf 144 Seiten geht es einmal quer durch das Fachgebiet, das die Autoren in fünf Abschnitte aufgeteilt haben: Die Klimageschichte der Erde; die derzeitige globale Erwärmung und ihre Ursachen, die Folgen des Klimawandels; die öffentliche Diskussion um den Klimawandel und schließlich die möglichen Lösungswege. Viele ihrer Aussagen und Analysen zum Klimawandel sind bekannt – doch man hat sie selten so kompakt, übersichtlich und kompetent auf so wenig Raum zusammengefasst gefunden.”
Susanne Billig, Deutschlandradio Kultur, 23. März 2006
“Stefan Rahmstorf und Hans-Joachim Schellnhuber haben ein Buch geschrieben, das einen hervorragenden Überblick über Erforschung, Folgen und Lösungsmöglichkeiten des Klimaproblems gibt.”
RBB-Inforadio, 8. April 2006
Raymond S. Bradley provides his readers with a comprehensive and up-to-date review of all of the important methods used in paleoclimatic reconstruction, dating and paleoclimate modeling. Two comprehensive chapters on dating methods provide the foundation for all paleoclimatic studies and are followed by up-to-date coverage of ice core research, continental geological and biological records, pollen analysis, radiocarbon dating, tree rings and historical records. New methods using alkenones in marine sediments and coral studies are also described. Paleoclimatology, Second Edition, is an essential textbook for advanced undergraduate and postgraduate students studying climatology, paleoclimatology and paleoceanography worldwide, as well as a valuable reference for lecturers and researchers, appealing to archaeologists and scientists interested in environmental change.
Paleoclimatology is a definite “must-have” for anyone working in climate studies and highly recommended for anyone seriously interested in our climate.
William R. Green, The Leading Edge
This thorough, well referenced text will prove to be indispensable to anyone involved in the study of past and current climate change and modeling.
The past few weeks and years have seen a bushel of papers finding that the natural world, in particular perhaps the ocean, is getting fed up with absorbing our CO2. There are uncertainties and caveats associated with each study, but taken as a whole, they provide convincing evidence that the hypothesized carbon cycle positive feedback has begun. [Read more…] about Is the ocean carbon sink sinking?
Two weeks ago, we published the first lesson in curve manipulation taught by German school teacher and would-be scientist E.G. Beck: How to make it appear as if the Medieval times were warmer than today, even if all scientific studies come to the opposite conclusion. Today we publish curve manipulation, lesson 2: How to make it appear as if 20th Century warming fits into a 1500-year cycle. This gem is again brought to us by E.G. Beck. In a recent article (in German), he published the following graph:
Notice how temperature goes up and down in beautifully regular cycles since 800 B.C.? At the bottom, they are labelled “Dansgaard-Oeschger cycles” – this refers to the Dansgaard-Oeschger events found in Greenland ice cores during the last Ice Age (but not during the last 10,000 years), about which there is a serious scientific discussion whether they are paced by a 1500-year cycle (see my paper in GRL). Beck’s curve shows a warm phase 400 BC and the next one 1200 AD – that’s 1600 years difference, so it just about fits. (I’m not endorsing his curve, by the way, I have no idea where it comes from – I’m just playing along with it for the sake of the argument). So the next warm phase should be in the year – oooops… 2700 or 2800? Hang on, how come it looks like the current warmth fits so nicely into the cycle? Shouldn’t we be right in the coldest phase? Now I see it… two little lines across the x-axis indicate that the axis has been broken there – tick-marks after the break are in 200-year intervals and before the break in 400-year intervals, and there’s also a gap of 200 missing years there. So that’s how we make the current global warming fit past climate cycles – it’s so easy!
p.s. Beck appeared on German TV last Monday, after the “Swindle” film was shown, and he is announced to appear on the program “Report München” in the first channel of public German TV next Monday (18 June), to educate the viewers about another of his fantasy graphs, namely his CO2 curve. It promises to be a must-see for friends of the unintentionally farcical.
The sea level rise numbers published in the new IPCC report (the Fourth Assessment Report, AR4) have already caused considerable confusion. Many media articles and weblogs suggested there is good news on the sea level issue, with future sea level rise expected to be a lot less compared to the previous IPCC report (the Third Assessment Report, TAR). Some articles reported that IPCC had reduced its sea level projection from 88 cm to 59 cm (35 inches to 23 inches) , some even said it was reduced from 88 cm to 43 cm (17 inches), and there were several other versions as well (see “Broad Irony”). These statements are not correct and the new range up to 59 cm is not the full story. Here I will try to clarify what IPCC actually said and how these numbers were derived. (But if you want to skip the details, you can go straight to the critique or the bottom line).
[Read more…] about The IPCC sea level numbers