On 14 May
the new book on climate change in the Baltic Sea basin and related impacts was
presented and discussed at the 2nd European Climate Change Adaptation
Conference (ECCA) in Copenhagen. This
event seemed perfect for this purpose as several hundred scientists,
practitioners, politicians and other stakeholders gathered at the ECCA
conference to discuss the state of the science and adaptation strategies
regarding the challenge of climate change.
In the
morning, Marcus Reckermann, coordinator of the book project, presented some
core results on behalf of the authors. Then, in a midday plenary, BACC
initiator and chairman Hans von Storch of the Helmholtz-Zentrum Geesthacht and
University of Hamburg, gave some background information on the BACC scope and
process, followed by a vivid panel discussion. Members of the discussion panel
next to Hans were (from left to right): Deliang Chen of the University of
Gothenburg, Sweden, renown climate scientists and former Executive Director of
ICSU (International Council of Science), Lykke Leonardsen, co-organizer of the
ECCA conference and head of the Climate Unit of the City of Copenhagen, and
Maxi Nachtigall, Advisor at CBSS (Council of the Baltic Sea States), a
political forum for regional intergovernmental cooperation between the Baltic
Sea states. The midday session was chaired by Jürgen Kropp of Potsdam Institute
for Climate Impact Research, and the discussion was moderated by Marcus
Reckermann of the International Baltic Earth Secretariat.
The
discussion evolved around two questions: Firstly, what are the differences
between BACC and the IPCC reports (and why are regional reports necessary), and
secondly, specifically addressed to the two ladies, what is the use for
stakeholders? Here is the attempt of a very brief summary:
Why a
regional report?
The first
question was taken up by Hans who pointed out that regional experts know the
conditions in their region better than “global” experts. Also, regional
decision makers require regional knowledge, as highly resolved as possible.
Hans also stressed the aspect that knowledge is more important than authors,
which is manifested by the fact that the new BACC report was authored by a
completely new group of authors, who nevertheless confirmed the knowledge of
the first report of 2008. Deliang mentioned the aspect that BACC is an independent
“bottom-up” effort organized by scientists while IPCC is a political
organization under governmental influence. Still both approaches have their
justification and should be considered as complementary rather than
competitive.
Is it any
use?
The question
whether the previous BACC material had been used by the stakeholder community
was candidly discussed. Both representatives from the stakeholder community
confirmed that the BACC material has been useful, but they also revealed
potential for improvement. Maxi suggested that a cooperation with other
stakeholders similar to the one with HELCOM would be desirable, so that the
material could be better shaped for the specific stakeholder needs. Lykke
pointed out that it is virtually impossible for a practitioner in a city
administration to work through the whole book and find the gems which are
relevant for their work. “Help us find the diamonds”, Lykke said, and Hans
replied that scientists do not know what the true diamonds for specific
stakeholder groups are. “You need to tell us what you need to know”, he said.
Also the envisaged publication of small summary booklets in the many languages
of the Baltic Sea region, may only partly solve this problem.
It seems
that if we really want to provide useful information not only for the
scientific community, we need to communicate on a par and in an open way. Maybe
this resume has also relevance for the complete conference.
7 comments:
Dear BACC team,
With interest I have seen your press release about the new BACC report:
http://www.hzg.de/public_relations_media/news/058989/index.php.en
However, I was surprised to see that the press release does not mention key content from the two palaeoclimate chapters. Of particular interest I found this statement:
“...a warm and stable climate with air temperature 1.0–3.5 °C above modern levels (8000–4500 cal year BP)...”.
In the chapter on the Medieval Warm Phase (MWP) I discovered this paragraph which in my opinion is crucial for understanding the context of the 20th century climatic evolution:
“Recent investigations of Fennoscandia by Ljungqvist (2010) showed that the MWP [Medieval Warm Period] occurred between 800 and 1300. At that time, warm-season (May-September) temperatures exceeded the contemporary warming of the end of twentieth century by about +0.5°C.”
Why have you not mentioned any of this content in your press release? Your subheader "Warming continues" reads very different when you know that 1000 years ago the Baltic area was already as warm as today or even warmer. I think it would have been your ethical duty to put the context right to avoid misinterpretation. The elephant in the room: How could it have been as warm as today in the Baltic during the MWP when CO2 levels were low?
Best regards
Sebastian Luening
Thank you for your comment which touches an important point. In fact, the first two chapters on the Holocene conditions in the Baltic Sea region were added to this new book to put the recent warming into perspective, to treat this important subject. The results are clearly spelled out in the chapters and also in the Executive Summary in Chapter 1 so there is surely no hiding or downplaying of findings. Of course you can criticize that the postglacial warming was not explicitly mentioned in the press release, but a press release cannot repeat the complete content of the book but needs to be short and concise, and we need to choose which points wrap up the book in a few sentences as good as possible. In fact other aspects which other interest groups may find of outstanding importance are also not mentioned in the press release.
The BACC project is defined as purely scientific project, not being influenced by vested interests, be it by Oil Companies or Greenpeace. It is our intention to let the scientific evidence speak (in the form of published knowledge) and we try to describe the scientific consent but also we aim to state issues where there is not enough or contradicting evidence.
May I add that this book contains three chapters (Part 6) which attempt to draw together the state of knowledge concening the question if there are other factors also responsible for the regional contempory warming in the Baltic Sea region next to atmospheric CO2 (aerosols, land cover change). Please keep in mind that the findings in the book all refer to the Baltic Sea region and there is no claim made for the global scale.
Mr. Löning you wrote:
“I was surprised to see that the press release does not mention key content from the two palaeoclimate chapters. Of particular interest I found this statement: “...a warm and stable climate with air temperature 1.0–3.5 °C above modern levels (8000–4500 cal year BP)...”.
In the chapter on the Medieval Warm Phase (MWP )I discovered this paragraph which in my opinion is crucial for understanding the context of the 20th century climatic evolution: “Recent investigations of Fennoscandia by Ljungqvist (2010) showed that the MWP [Medieval Warm Period] occurred between 800 and 1300. At that time, warm-season (May-September) temperatures exceeded the contemporary warming of the end of twentieth century by about +0.5°C.””
I have to ask for your understanding that it took a little before you get this answer, but I needed some time to consider your inquiry.
Indeed, I asked Eduardo Zorita, who is one of the authors of the chapter on the Holocene Chapter 2, and his response was “The external climate forcings in the Mid-Holocene were different as today. For instance, not only the concentrations of greenhouse gases was different, but also the orbital configuration relative to the sun was different and as a consequence the solar insolation was also different. Especially at seasonal and regional scales, the solar insolation at high latitudes in the Northern Hemisphere was considerably stronger than today, and therefore, it is not surprising that the temperature in the Baltic Sea area during this period is believed to have been higher than today, specially so during the summer season.” Additionally one has to keep in mind the then very different geographic configuration of the Baltic Sea region.
The issue of the MWP is considered in Chapter 3.4, “The Medieval Warm Period”. Eduardo Zorita’s assessment is: “The case of the MWP is not so clear-cut, and its causes are still a matter of research. The energy output of the sun during this time could have been higher, although the uncertainty in its reconstruction are still broad. The recent PAGES2K reconstructions of continental temperatures indicate warmer temperatures than the mid-20th century over some continents, but not everywhere. Thus, it is not yet clear if the MWP was a global or regional phenomenon.” Here I would add that the sentence “Recent investigations … showed that the MWP [Medieval Warm Period] occurred between 800 and 1300. At that time, warm-season (May-September) temperatures exceeded the contemporary warming of the end of twentieth century by about +0.5°C.” is indeed potentially misleading, as it asserts an elevated temperature of about 0.5°C without making the uncertainty explicit. From the rest of the chapter it is clear (see: Abstract) that the warmer periods were not uniform across time. The sentence, as contained in the report, is based on one recent paper, making use of tree-ring width and wood density; that these data reproduce only part of the past variability and suffer from substantial uncertainty is long known, and we are good advised to show restraint in putting too much into such inversions in terms of temperature and precipitation. From the context the uncertainty becomes clear, but it may have been better if the formulation would have been less definite.
Dear Dr Reckermann,
I am thankful that you took the time to reply to my comments. As you rightly say, my criticism is not about the report - which represents a solid piece of work. I am more concerned that the press release actually does not follow your principle of open and unbiased reporting. I am fully aware that a press release has to be selective due to space constraints. But a conscious decision was taken by your team and the institute to highlight the temperature evolution in the press release. In my opinion it would have been your ethical duty to provide the full context of the 20th century warming. In your press release you write:
"The current study takes into consideration observed climate changes for approximately the last two hundred years".
This is incorrect. The truth is that the report also looked at the climate evolution of the past 10,000 years. Why are you hiding this in the press release? Maybe because inconvenient questions could have been asked like "how was the climate during that time"?
Let's not discuss the Mid Holocene Climate Optimum which indeed may be related to Milankovic cyclicity. Still it is an eye-opening fact that temperatures were much higher at the time than today.
I am more concerned with the Medieval Warm Phase, 1000 years ago. In your press release you have a subheading "Warming continues". It should have been your duty to provide the context of this "warming" to the public, that prior to the warming there was cooling in the Baltic area, of roughly the same amount. The whole meaning of the statement "Warming continues" changes 180°. A better subheading would have been "Significant Warming during 20th century, now matching temperatures of the Medieval Warm Phase 1000 years ago". I simply cannot accept that there was "not enough space" in the press release, this fact is just too important to leave it out. Omission in this case has a very strong political flavour to me.
I am fully aware that your report has a regional and not global character. We need more of these comprehensive regional reports for different regions of the world in order to build a solid palaeoclimatological and climatological basis for our understanding. It will be hard to unravel the overall drivers only from one region alone.
As you may be aware, I am of the opinion that we currently seriously underestimate the role of the fluctuating sun in the climate equation. A good example is Leal-Silva & Velasco Herrera (2012) who found that sea ice distribution in the Baltic Sea was largely controlled by solar activity changes: http://www.sciencedirect.com/science/article/pii/S1364682612002167
I have run a full text search through your open access book (thanks for making it freely available!), but could not find this important paper. Why?
I want to urge you to keep your principle of unpolitical and unbiased work. In this case, however, it has failed at the stage of the press release.
Best regards
Sebastian Lüning
Dear Mr von Storch,
Thanks a lot also to you for providing these additional information. Independent of the press release that I criticize, I find the question of the Medieval Warm Period of great importance. There are good papers out there that show a very clear MWP, such as Ljungqvist et al. 2012.
http://www.clim-past.net/8/227/2012/cp-8-227-2012.html
I will have to study the PAGES2K report in more detail before I comment. It is clear that there is never a 100% worldwide snychronicity to be expected. Even today, Antarctica has been cooling for the last few decades. Does it question the overall warming of the 20th century? No, it does not. Let's put it like this: At the moment we cannt rule out that the MWP is of similar extent as the present Modern Warm Phase. None of the climate models can reproduce a "global" MWP. This worries me.
But it is true, more work has to be done on the palaeoclimatology, unaffected by political interests. We will present a couple of regional reviews on the MWP on the www.kaltesonne.de website in the coming months. I am curious myself what will be the outcome.
Best regards
Sebastian Lüning
Dear Sebastian Lüning,
thanks for your interest in the Medieval Warm Period which is indeed a very important research topic. I tried to verify the remarkable sentence you brought up here from the BACC II report refering to Ljungqvist (2010)
"Recent investigations of Fennoscandia by Ljungqvist (2010) showed that the MWP [Medieval Warm Period] occurred between 800 and 1300. At that time, warm-season (May-September) temperatures exceeded the contemporary warming of the end of twentieth century by about +0.5°C."
Unfortunately, the reference seems to be not correct here as the paper does not deal with Fennoscandia nor with the warm-season. I asked the lead author if he can help to find the correct reference. Ljungqvist (2010) is about annual temperatures for the entire northern hemisphere north of 30°N. His reconstruction indicates even a "... Roman Warm Period as warm on a hemispheric scale as the twentieth century.". You should however also read what he writes about the most recent warming and about major uncertainties inherent to his and comparable studies.
Reference:
Ljungqvist (2010): A NEW RECONSTRUCTION OF TEMPERATURE VARIABILITY IN THE EXTRA-TROPICAL NORTHERN HEMISPHERE DURING THE LAST TWO MILLENNIA
Tadeusz Niedźwiedź, the lead author of Chapter 3, responded today as follows:
Corrigendum and explanations concerning BACCII Chapter 3 “The Historical Time
Frame (Past 1000 years)”, pages 57 and 64.
Text on page 57:
“Recent investigations of Fennoscandia by Ljungqvist(2010) showed that the MWP
occurred between 800 and 1300. At that time, warm-season (May–September)
temperatures exceeded the contemporary warming of the end of twentieth century by
about +0.5 °C.”
must be corrected as follows (corrections are in italics):
“Recent investigations of temperature variability in the extratropical Northern
Hemisphere by Ljungqvist (2010a) showed that the MWP occurred between
800 and 1300. At that time in Scandinavia north of 60° N (Ljungqvist 2010b),
warm-season (May–September) temperatures exceeded the contemporary warming
of the end of twentieth century by about +0.5 °C.”
Also in the References on page 64:
Ljungqvist FC (2010) A new reconstruction of temperature variability in the
extratropical Northern Hemisphere during the last two millennia. Geogr Ann A
92:339-351
must be corrected and supplemented by the second paper of Ljungqvist (2010b):
Ljungqvist FC (2010a) A new reconstruction of temperature variability in
the extratropical Northern Hemisphere during the last two millennia. Geogr Ann A 92:339-351
Ljungqvist FC (2010b) A regional approach to the Medieval Warm Period and the
Little Ice Age. In: Climate Change and Variability, Suzanne Simard (Ed.), ISBN:
978-953-307-144-2, InTech, 1-25, DOI: 10.5772/9798. Available from:
http://www.intechopen.com/books/climate-change-and-variability/a-regional-approach-
to-the-medieval-warm-period-and-the-little-ice-age
Additional comment and explanation:
The information that during “warm-season (May–September) temperatures exceeded the
contemporary warming of the end of twentieth century by about +0.5 °C” was taken
from the curves of a temperature reconstruction in the second paper of FC
Ljungqvist (2010b), presented on page 7 on Fig. 3. The level of temperature
deviation is about +0.4°C at the end of the 20th century, and +0.9°C in the second
half of the 12th century. The difference is +0.5 °C.
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