Temos tido uma política de (em geral) não comentar os vários rascunhos, citações incorretas e erros de leitura no relatório da Quarta Avaliação (“AR4” para aqueles acostumados com acrônimos) do IPCC. Agora que o sumário para tomadores de decisão (ou “SPM”) do IPCC foi enfim publicado, é possível discutir seu cerne sem nos preocupar tanto com sutilezas e detalhes do relatório. Esta postagem é somente inicial, desde que planejamos avaliar o relatório capítulo por capítulo durante os próximos meses, explicando as questões chaves e as questões ainda incertas. Este relatório será repetidamente referenciado nos próximos meses, de modo que poderemos a tempo realizar um trabalho razoável explicando seu conteúdo e motivo.
Em primeiro lugar, pelas pesquisas que vêm sendo realizadas desde o Terceiro Relatório de Avaliação (TAR) de 2001 – muitas das quais têm sido discutidas aqui – não é surpresa alguma que o AR4 traga uma forte conclusão. Em particular, o relatório conclui que as influências humanas sobre o clima são “muito possivelmente” (> 90% probabilidade) detectáveis nos dados observados; aumentado de “possivelmente” (> 66% probabilidade) no TAR. Resultados chaves apresentados aqui incluem as simulações climáticas ao longo do século XX, realizadas com os mais modernos modelos de clima, demostrando que as recentes tendências não podem ser explicadas sem a inclusão do aumento da concentração de gases de efeito estufa devido às ações humanas. Esse aumento também é consistente com o aquecimento dos oceanos, derretimento de gelo nos mares e em terra, e sinais de mudanças em ecossistemas naturais. Tal conjuntura torna irrefutáveis as projeções de grandes e contínuas mudanças ao longo do tempo, particularmente sobre o cenário business as usual (sem mudanças nos padrões globais de produção e consumo).
Tendo em vista todo o sensacionalismo desde o TAR, muitos de nós estávamos curiosos para ver o que o novo relatório iria trazer sobre as reconstruções paleoclimáticas dos últimos 1000 anos. Os ’contrários‘ irão sem dúvida ficar desapontados. As conclusões têm sido significativamente fortalecidas em relação ao que havia no TAR, o que certamente deveria ser esperado, haja vista os numerosos estudos adicionais que têm sido feitos apontando para uma mesma direção. A conclusão de que o recente aquecimento em grande escala provavelmente excede o alcance visto nos últimos séculos, foi estendido dos 1000 anos utilizados no TAR, para os últimos 1300 anos no relatório atual, e a confiança nessa conclusão foi promovida de “possivelmente” no TAR para “muito possivelmente” no relatório atual para o último meio milênio passado. Esta é apenas uma das várias e independentes linhas de evidências agora apontando em direção a uma clara influência antropogênica sobre o clima. Porém, dada todas as outras, as reconstruções paleoclimáticas são agora menos ainda o pilar central das evidências da influência humana sobre clima do que vinham incorretamente sendo consideradas.
As incertezas científicas envolvem principalmente a natureza precisa das mudanças esperadas, particularmente com respeito à elevação do nível do mar, mudanças do El Niño e em regimes hidrológicos regionais – freqüência de secas e descongelamento de coberturas de gelo, tempestades em latitudes médias, e com certeza, furacões. Pode ser divertido avaliar os pormenores das discussões nestes tópicos (e nós esperamos que haverá uma cobertura substancial da impresa sobre eles), mas isso não deve nos distrair das principais e das mais sólidas conclusões.
O processo de finalização do SPM (o qual é bem descrito aqui and aqui) pode parecer um pouco estranho. Representantes dos governos de todas as nações participantes pegam o rascunho do sumário (como escrito por um dos autores líderes de um dos capítulos individuais) e discutem se o texto reflete fielmente a ciência que está por trás do relatório principal. A chave aqui é notar que o que os autores líderes originalmente redigiram não é necessariamente a mais clara ou menos ambígua linguagem, de modo que cabe perfeitamente aos governos (para os quais o relatório está sendo escrito) insistirem que a linguagem seja modificada para que as conclusões sejam corretamente entendidas por eles e pelos cientistas. É também importante frisar que os cientistas têm que estar contentes com a linguagem final acordada, e se esta concorda com a ciência contida nos capítulos técnicos. A vantagem desse processo é que qualquer um envolvido está absolutamente consciente dos significados de cada sentença. Lembre-se que depois do National Academies report on surface temperature reconstructions” houve muita discussão sobre a definição de ‘plausível’. Este tipo de coisa não deve ocorrer no AR4.
O processo do SPM também é muito útil como uma proposta política. Especificamente, ele permite aos governos envolvidos sentirem-se ‘como parte’ do relatório. Isso torna difícil mudanças posteriores nas posições assumidas, com base no argumento de que o relatório foi escrito por outra pessoa. Isso fornece aos governos um absoluto interesse em tornar esse relatório o melhor possível (dada as incertezas). Existem de fato muitas salvaguardas (ao menos pelos cientistas presentes) para assegurar que o relatório não seja enviesado em qualquer direção preferencial. Todavia, o lado ruim é que ele pode ser erroneamente confundido como um ponto de partida para negociações. Esta pode ser uma conclusão falsa – as negociações estão, de fato, fortemente constritas pela ciência subjacente.
Finalmente, poucas pessoas têm se perguntado por que o SPM está sendo lançado agora enquanto o relatório deverá ainda ser publicado em alguns meses. Existe um número de razões – primeiramente, a reunião de Paris possui tal significado público que segurar o SPM até que o relatório principal esteja pronto torna-se sem sentido. O relatório principal propriamente dito ainda não foi corrigido na íntegra, e não houve tempo suficiente para incluir dados observacionais do fim de 2006. Uma questão final é que as melhorias na concisão da linguagem do SPM devem ser propagadas para os capítulos individuais, de modo a remover qualquer ambigüidade superficial. O conteúdo científico não deve mudar.
Se dependesse de nós, teriamos tentado colocar tudo junto de modo que eles pudessem ser lançados ao mesmo tempo, mas talvez isto não fosse possível. Notamos que o “Arctic Climate Impact Assessment” em 2004 também teve um procedimento similar – o que levou a uma certa confusão inicial, pois as afirmações contidas no sumário não estavam referenciadas.
O quão bom estavam os relatórios anteriores do IPCC quanto à antecipação do futuro? Na verdade, nos últimos 16 anos (desde o primeiro relatório em 1990), eles têm se mostrado notavelmente bons para as mudanças de CO2 e temperatura, mas com previsões não tão boas acerca das mudanças do nível do mar.
Com relação às discussões específicas, os dois temas mais cobertos pelos jornais são as projeções de aumento do nível do mar e os furacões. Essas questões contêm um número de “ignorâncias conhecidas” – coisas que nós sabemos que não sabemos. Para o aumento do nível do mar, o desconhecimento é quão grande será o efeito de alterações na dinâmica das superfícies de gelo. Tais mudanças dinâmicas já foram observadas, mas estão fora do alcance da capacidade dos modelos atuais de superfícies de gelo (veja esta discussão anterior). Isso significa que suas contribuições para o aumento do nível do mar são bastante incertas, mas com todas as incertezas pendendo para o pior cenário (veja este recente artigo para uma avaliação (Rahmstorf , Science 2007)). A linguagem no SPM ressalta isso dizendo
“Processos dinãmicos relacionados à movimentação de gelo não incluídos nos modelos correntes mas sugeridos por observações recentes podem ampliar a vulnerabilidade das superfícies de gelo ao aquecimento, aumentando a futura elevação do mar. A compreensão desses processos é limitada e não há consenso sobre sua magnitude.”
Note que alguns órgãos da mídia têm comparado maçãs com peras: eles argumentam que o IPCC reduziu seu limite superior do nível do mar de 88 para 59 cm, mas o primeiro número do TAR incluiu a incerteza da dinâmica do gelo, enquanto que o último do AR4 não inclui, precisamente porque essa questão é agora considerada mais incerta e possivelmente mais séria que antes.
No caso das tempestades tropicais/furacões, a linguagem é muito suave, como pode-se esperar do um documento de consenso. A ligação entre SST e a intensidade de tempestades tropicais é claramente reconhecida, mas também a distância entre as projeções de modelos e as análises das observações de ciclones. “O aumento aparente da porporção de eventos muito intensos desde 1970 em algumas regiões é muito maior que o simulado pelo modelos atuais para este período”.
Iremos focalizar algumas dessas questões em postagens específicas durante as próximas semanas. Existe muita coisa aqui, e o nós precisaremos de tempo para digerir tudo!
Traduzido do inglês por Ivan B. T. Lima e Fernando M. Ramos.
Where may I obtain a copy of the actual report, instead of just a summary?
[Response: The full report won’t be finalized until April. –eric]
Just mentioning another possible environmental disaster linked to global warming and climate change: when the Greenland glaciers finally melt (either slowly or in a big whoosh) tectonic rebound will probably increase the frequency and magnitude of earthquakes around the world. The 30 foot rise in sea level will cause the Antarctic ice shelves to detach making it easier for the Antarctic glaciers to move more quickly into the ocean, causing still more sea level rise, tectonic rebound and earthquakes.
Nice world we are leaving our grand children. And theirs.
[Response: I am happy to be able to correct you that tectonic rebound from the Greenland ice sheet won’t have impacts on earthquakes around the world. Big earthquakes are due to processes much deeper in the earth’s crust, and much more localized. It is, on the other hand, rather likely that rising sea levels will help to destabilize the Antarctic ice sheet. On what timescale, however, remains quite uncertain. –eric]
Minor, minor observation:
even we need time to digest it
I know it wasn’t the intention, but that comes across as a little arrogant. I know that you are professional climatologists and wicked smart and all, but I would have gone with sometihing like “and we need time to digest it too.”
Minor point, but tone matters.
[Response: Fair enough! Of course what was really meant is that virtually all of the science being reported on is stuff that we are already very familiar with. “Digesting it” means making sure that what we think is in it (even before reading it) is actually in the final text, we most of us, like you, have just gotten a chance to start reading. -eric]
The direct link to the summary report (that is, what was published today) is here:
http://www.ipcc.ch/SPM2feb07.pdf
Keep an eye on http://www.ipcc.ch/ to see the other sections as they’re released.
The immediate thing that stood out for me about the AR4 SPM is the willingness to talk (again) about “the globally averaged net effect of human activities since 1750”, whereas here and hereabouts, of recent times, there has been more of a “let’s keep it to the last ~50 years” kind of discussion (whether by accident or design).
I find this encouraging, for the science.
You can find the SPM report at: http://ipcc-wg1.ucar.edu/
“Scientists offered Cash to Dispute Climate Study”
http://www.commondreams.org/headlines07/0202-05.htm
This is very confusing to the public. The 59 cm is the upper bound in the A1F1 scenario. I quote from AR4 —
Who among us expects a decreasing or linearly growing flow rate from the ice sheets until the year 2100? This would make recent trends anomalous. The public will see a lower number and not understand that the trend is “more serious than before” — and also not understand recent not-included studies that indicate accelerating flow rates in Greenland and W. Antarctica. Already there is considerable confusion in the media. This constitutes a disservice to mankind.
#1, the report can be found here
Sorry to nitpick, but it would be nice if, when finalizing a report that is to be read by hundreds of millions of people, the authors could remove unfinished formating suggestions (e.g. [Numbers to be converted to mm per year] on page 5 and [To be changed: Change annotation from cnstant composition to year 2000 constant concentration. Colour central bar in grey bars and lettering to match A2, A1B, B1 curves as appropriate. Drop model numbers and move to caption] on page 21). It makes an otherwise well-crafted report appear unprofessional. Both of the copies report linked from the IPCC site have these formatting errors, at least at the time of posting:
http://ipcc-wg1.ucar.edu/wg1/docs/WG1AR4_SPM_PlenaryApproved.pdf
http://www.ipcc.ch/SPM2feb07.pdf
I think I already found an error in the SPM! If you sum up the contributions to sea level rise from 1993-2003 in table SPM-O, you get 0.657, not 0.28. I think they screwed up the Greenland and Antarctic values, which they list as 0.21 (each). If you assume they are 0.021 instead, the sum total contribution is indeed 0.28.
OOPS!
[Response: Well spotted. I noticed this as well and alerted IPCC a few hours ago. -stefan]
BBC News24 are announcing it as the end of “the debate” about the reality of climate change.
So that means the real battle to get individuals to factor this into behaviour is now starting. It seems to me that our only attainable option is to aim to take the edge off the increases by energy efficiency etc. Drop the talk about “Stop Climate Chaos”, implications that we can just stop fall in the face of evidence and reason. Argue for the attainable; piecemeal reduction of emissions. Do what you can. Every little helps.
But I think it would have been a stronger “coup de grace” had it been presented at the same time as the WG1 Scientific Basis report. Surely as it’s based on the results of WG1 they could have finalised the full Scientific Basis first?
BCC.
These are the sort of people who do stuff as cheeky as attempting to model something as complex as climate and pull it off! (e.g. http://rabett.blogspot.com/2006/09/well-lookee-that.html ) As an intellectual also-ran I request RealClimate leaves the ‘even’ in.
Neal Boortz attempted to criticize the report. Very interesting and ALL flawed. What’s worse is that he uses it to convince listeners, who have no knowledge of the science and believe him. http://boortz.com/nuze/index.html
It would be both very good and very useful to have a point by point rebuttal of the charges this fellow makes. Not being a climatologist’s but certainly someone with a great deal of interest in this subject (I am a research scientist in photobiology) who gets called on to comment occasionally on global climate change (stratospheric ozone depletion/UVB impacts) it would help to have some good strong arguments to counter the comments by this person. Good references would be most appreciative as well.
A few errors I’ve noted in the media coverage.
1. Most reports I’ve heard say that the IPCC says it’s 90% likely that etc. Actually their term “very likely” means 90-99% certain.
2. Most reports talk about temperature rise etc. by 2100. Actually the summary gives the averages expected 2090-2099, a half-decade sooner. Not significant I suppose but annoying.
3. Most reports I’ve heard mention a 1.5-4 degree C expected rise. These are actually the best estimated central values for different economic-technological scenarios. Fair enough, but the ranges of temperatures the IPCC considers “likely” go from 1.1-2.9 for the most benign emission scenario to 2.4-6.4 for the least benign one (that’s the one with the 4.0 “best estimate”), so the actual “likely-depending-on-what-we-do” range is 1.1-6.4
[Response: Spencer, your second point is quite relevant for sea level, where leaving off the last 5.5 years (when it rises fastest) and other technicalities are the reason why the new sea level values look a bit lower than the previous model projections. In fact, all else being equal, for any given emission scenario the new (AR4) models give a slightly higher sea level projection than the old models used in the TAR, we were told in Paris. -stefan]
O.K., so if we assume there is a human coponent, how do we know what percentage of global warming is attributable to humans and, even if we were to stop any further increase from the human component, that would slow down or even reverse the process?
Also, Spencer: let’s say “very likely” means 99% certain that (human) greenhouse gases have caused most of the observed increase in globally averaged temperatures since the mid-20th century. What does “most” mean in regard to my pending questions? Does that include gases from non-human sources? Keep in mind that the Paris study, looking at all the science of global warming, will only project a “best estimate” that temperatures will rise by 3 Celsius (5.4 Fahrenheit) by 2100 over pre-industrial levels. I doubt that is bad enough for the entire world to stop in its tracks.
#16 exactly…… if humans are the culprit…..
Should you not be calling for reducing the human population on this planet then?
Should you not be doing a Kyoto on China, India, and Muslims which each have approximately 1.3 billion and growing populations?
Just want to think RealClimate for its efforts to help non-scientists to understand the new report. I am part of Al Gore’s Climate Project and working very hard to improve my understanding of all this to complement the local presentations of his slide show I am doing. Realclimate makes that much easier!
The SPM predicts 20% drop in precip in subtropics. Do we trust the models enough to beleive the projections for regional shifts in precip?
Release of this new IPCC summary is a profound event and will be covered by every major newspaper in the world, as it should. Scientifically speaking, no other domain benefits from such a magnificent collaboration of investigators, whose task is to summarize the published literature into concise, universally usable reports – imagine if every field of science had the benefit of such review! What a boon to researchers and the public both. But climate-related science especially demands this level of attention – it is a political decision to do this, not merely an intellectual one, for it reflects the importance and urgency of the relevant information, not to mention the widespread lack of action that it suggests is needed.
To my mind, as a sometime student and scholar of scientific expression past and present, the report is a well-tuned document. It’s authors have clearly learned a thing or two from the last go-around. It is crisp, data-rich, fairly well-organized, and confident in its points. It uses qualitative but explained probabilities (extremely likely, very likely, likely, etc.), discusses (in yellow-highlighted boxes) the significance of the knowledge domain covered by each section, and admits uncertainties. It is not a policy document, per se: it does not recommend or critique specific measures, ideological concepts, weigh risks and benefits, or the like. It has what might be termed a low intimidation factor, meaning that nearly all the scientific points are comprehensible to the educated layperson. There is a pictorial rhetoric, too, that is very effective. The graphics, though placed at the end instead of embedded in the narrative (as in most scientific documents) are improved from the TAR (2001 report). Going through them has a cumulative effect that even supersedes that of the text. Especially interesting and well-done, in visual terms, is the global map showing temperature trends since 1900 for the major continents. The final two pages of figures, a culmination of sorts, showing predicted temperatures and precipitation patterns for the remainder of the century, are visually striking, and thus daunting. There is calculated force here (on the eye and mind), to be sure, but one that is warranted by the results. To claim this as “propaganda” would be absurd and naive: all effective documents employ these sorts of persuasive tools, and have done so since manuals of rhetoric were written in Greek and Roman times (Galileo’s famous little book, Sidereus nuncius, with the first pictures of a rocky moon, is a superb example).
But here’s another point. It is not just the content of this document that matters with regard to its place in our evolving discussion on climate change, but how it’s represented in the media. This may be obvious, but the reality is a complex affair. Compare, for example, this morning’s coverage by the International Herald Tribune and our favored NYTimes. The former discusses the importance of the report, it’s confirming aspects with regard to the phenomenon of global warming, and implications, with some spicing of comments by authors and reviewers, some rather silly ones (“This is real. This is real. This is real.”) Most important, though, the article emphasizes that the science is not complete but in progress, and that the new report represents a further step in this process. Yes, we all know this, but saying it in these terms is fairly rare in newspaper and tv reports. As for the NYTimes, they decided to beat the drum of controversy: “Even before its release, world climate report is criticized as too optimistic.” It is focused almost entirely on the discussion over predicted sea level rise – the decision of the IPCC not to include potential ice melt, which is largely (as I understand it) due to timing issues of the published material and also uncertainties related to modeling. Moreover, the article ends with a little melody from Fred Singer about the IPCC being the contrarians now. This is indeed poor stuff from our most valued daily paper, but not really surprising.
The media are able to bring a critical faculty to bear on scientific subjects, but choose to do so on a haphazard and selective basis. Highlighting controversy, or manufacturing it, is not merely a way to attract attention; it is also a means of distinguishing your own reporting from that of other papers. The most basic aspect to climate science – that it is science-in-the-making, always advancing, always partial, always ready to jettison some things and improve others, and therefore any summary of it will be no more than a snapshot of what has already been surpassed – does not make for good news all the time. Reporters serve different masters than scientists, not necessarily kinder and gentler ones. The final truth is that the media are not necessarily well-qualified, on their own, to transmit technical knowledge to the public, but they are what we have. To understand these matters better, I’d recommend reading Dot Neklin’s book “Selling Science,” which remains the more clear-eyed treatment of the subject.
In the meantime, we will have to grit our teeth, hope, and sometimes smile at the popular treatment of this new, epochal report. Given the momentum that is now building in the U.S., I expect that good things will come out of the IPCC’s work. As I say, we can certainly hope so.
Jake at #16:
If you look at the SPM, page 16, there is a nice table of the magnitudes of various factors, anthropogenic and natural. The anthropogenic factors total out to a forcing of 1.6 Watts/m^2, while the natural factors are 0.12. Clearly, the human factors are the biggie. The vast majority of the current warming is ‘our fault.’
There was also discussion of the ‘% attribution’ question here at RealClimate back in October: https://www.realclimate.org/index.php/archives/2006/10/attribution-of-20th-century-climate-change-to-cosub2sub/
As for how much we have to change our behaviors before we restore our climate to a pre-industrial state, I think it can’t happen. A certain amount of warming is going to be with us for centuries. What we have to do is stop accelerating the process, so that the total warming is smaller than what are are currently heading towards.
Scientists and economists have been offered $10,000 each by a lobby group funded by one of the world’s largest oil companies to undermine a major climate change report due to be published today.
Letters sent by the American Enterprise Institute (AEI), an ExxonMobil-funded thinktank with close links to the Bush administration, offered the payments for articles that emphasise the shortcomings of a report from the UN’s Intergovernmental Panel on Climate Change (IPCC).
http://www.guardian.co.uk/frontpage/story/0,,2004399,00.html
Jake, see the name immediately above your question? click on it to read: http://www.aip.org/history/climate/
The comment taken from the leftist rag the Guardian, “Scientists and economists have been offered $10,000 each by a lobby group funded by one of the world’s largest oil companies to undermine a major climate change report due to be published today”…
Hmmm, so what did the IPCC pay people who for the most part aren’t scientists to come up with this myth called global warming?
[Response: Indeed an intellectually brilliant conspiracy theory… But in case anyone seriously wants to know: the 600+ scientists working on the IPCC reports do this for free in their spare time. That involves lots of hours wading through review comments (the report attracted over 30,000 such comments), and evenings and weekends away from the family. A voluntary effort I right now don’t feel like ever doing again, once seems enough for a lifetime… -stefan]
I would like to see more discussion of the reasons for the increase in probability regarding man induced climate change and how one goes from a 60 percent probability to a ninety plus probability. It’s not like rolling dice, I presume, so how precise are these probability estimates. Are they similar to the kinds of probabilities we get from noaa when we look up the forecasted weather? Or what?
The primary reason I bring this up is the fact that Lindzen seemed to make fun of the whole notion of probability the other night on CNN. Yes, I can understand that all this data and analysis makes us more certain, but is it really reasonable to put a number on it?
Re: 2
Could tectonic rebound from ice loss on Greenland and Antarctic result in additional significant increases in sea level?
For example, if something raised a portion of the bottom area of a lake, the displacement of the water would increase the surface level of the lake (assuming no lake outlets).
Does anyone know of any literature summarizing positive feedback effects. In particular I am interested in boreal permafrost feedbacks such as thawing permafrost, burning boreal forests…do these feedbacks overtake man made emissions scales and were these considered in the report findings such as shrinking sea ice was (hopefully)?
First, I totally agree with point 8 – why did they put in a 59cm upper bound that nobody seems to think is likely to be right – it is confusing, misleading and will be seized on by contrarians. At the very least they should have included an apples to apples comparison, as well as the one discounting the effect, especially in the summary, which is all that many folks will ever read.
Second – Point 13, Neal Boortz discussion – even if he was right, which is unlikely, he still seems to be saying that global warming is happening. Also he says that the IPCC are saying it is futile as we can’t stop it. That does seem to be the impression I get as well.
It seems to me that we need to start taking the whole issue of what to do about it a lot more seriously – emissions control is not going to be enough, even if it was incredibly aggressive, and the more optimistic models are right.
We are most likely going to have a sea level rise over the next century that will cause problems, and the rise will continue in the century after that, and possibly for quite a bit longer.
Either we need to really give up on places like Bangladesh and Venice and Northern Africa and so on, or we need to get some serious research going into putting the genie back in the bottle.
I know this is not a popular sentiment amongst climate scientists right now but I really don’t see that we have a choice, do we? Either we accept widescale disruption in the next 100-300 years with phenomenal human cost, or get cracking on finding additional techniques as well as the current ‘reduce carbon emissions’.
Any additional techniques, such as widescale stratospheric aerosols, or iron filings in the ocean or such like are going to take a decade or more to research, do tests with etc. During that time, the accuracy of models will continue to improve, as will our understanding of ice melt behaviour and the other uncertainties.
My current project is investigating the current set of options we have for attempting to reduce the impact of global warming – there are about a dozen methods at the moment, varying from plausible to blue sky. We need to push research for this sort of work way up the agenda, instead of it being the poor cousin to analysing what is actually happening – they go together – understand how it works and then changing things to improve the situation.
Please note – I completely believe the current approach of reducing carbon emissions is necessary, so that we can return to a relatively stable climate and avoid having an even bigger problem to face in the future. But while that happens, I think we have to have additional measures in place, or face a huge human cost.
Contrarians talk about how we will eventually go into the next ice age, as the climate changes no matter what we do. That is very likely true, and when that starts to happen, we are also going to have to deal with it, or accept even more destructive changes to the planet (I don’t want to get into the philosophy here of that issue…). That is not a reason to ignore the current problems. We have built a world that depends on a very stable climate, and until the population drops dramatically or we can easily adjust, we are going to have to try to maintain that stability, against the current warming and a future cooling.
A question regarding sea water rise…
If seawater would rise … say 10 m … would the seafloor compact a bit, resulting in less than 10 m effetive rise?
Pat Neuman — Tectonic rebound takes many thousands of years. The rebounding area you suggest is but a tiny fraction of the surface area of the oceans.
A few comments:
RC writes:
The AR4 states:
Indeed, the observed trend in global temperatures is about 0.2ºC per decade from 1990 to 2006 (or 2006 for that matter). What seems to be forgotten both by the IPCC and Rahmsdorf et al. (or at least swept far under the rug in Rahmsdorf et al.), is that a big volcano went off in 1992 and cooled global temperatures for 2-3 years afterwards (if not a bit longer). A big non-anthropogenic cooling near the beginning of the period of record being compared in one dataset (the observed data) and not in the other (the collection of IPCC model results) doesn’t lend itself to an appropriate comparison. Using a longer period of record, say 1977-2006, shows the observed global warming to be about 0.17ºC per decade, or, alternatively, removing the known volcano-influenced years, say 1992 and 1993, from the 1990-2005 period of record produces a warming rate of about 0.15ºC per decade. Take your pick. But, in either case, the observed warming rate is certainly in the low range of IPCC projections (from any IPCC report) for the period 1990-2005.
Also, RC comments about sea level rise and the potential contribution from ice sheet dynamics, quoting the IPCC AR4 SPM:
I would like to add that also found in the IPCC AR4 SPM is the following concerning the role of dynamic ice processes on sea level rise:
Notice the phrase “but these flow rates could increase or decrease in the future” [emphasis mine]. While some commentors may choose to ignore this (e.g. RealClimate) and others may think that it is a “disservice to mankind” (e.g. comment #8), nevertheless, the IPCC authors felt that the current state of the science necessitated its inclusion.
-Chip Knappenberger
to some degree, funded by the fossil fuels industry since 1992
[Response: First, my name is Rahmstorf. Second, I find your accusation that we sweep something under the rug bizarre, since we show all the data since 1973. I invite everyone to see for themselves; to those without subscription, our paper can be accessed through the link on my home page. -stefan]
Re: #28. Something else would sink as Greenland rose but the timing would vary and contribute to the natural sloshing around of global sea level. I post this because I’m amazed at our need to totally understand how the earth and everything works. Somewhere, sometime, some comedian needs to do a skit of how we torture ourselves over our need to know every little detail. It kills my wife. Much more to worry about right now, but as an example the U.S.’s Gulf of Mexico coastline is slowly sinking in response to the melting and subsequent rise of the lands once under the laurentide ice sheet (see Gonzales and Tornqvist in Eos, Vol. 87, No. 45, 7 November 2006).
Would the moderators consider deleting the ignorant, sneering, hostile, insulting, content-free and completely worthless remarks from the flame troll identifying himself as “juandos”? Such drivel belongs on Free Republic or some other right-wing hangout, not here.
Re 21 [SPM and the media]
As Scott writes: The media are able to bring a critical faculty to bear on scientific subjects, but choose to do so on a haphazard and selective basis.
Indeed. Several media venues have a different spin.
Popular media behavior is shaped by market forces; hence, the need for a hooking headline and topic based on culling and maintaining readership. Akin to what you have said, I submit media choices are the best guess of an editor seeking to satisfy readership, advertisers, and stockholders.
Meanwhile, I am going to keep my eyes out for the reaction of ecologists–who can try to make sense of what will happen in the oceans–as currents accommodate to new exchanges of energy, and the poles continue to warm so much faster than the rest of the globe.
Frankly, my guess is one may very well be able to start watching the collapse of ocean food chains on the news eventuallyâ��partly due to pollution, and overexploitationâ��and now overtaxed by new ocean transport current relationships which are sure to emerge–perhaps without specific prediction. While the task of the IPCC does not stipulate exploring the reaction of ecosystems, the crux of our most vexing of problems will be how the Earth as a whole reacts on a granular level to the new phase composite of climate. Sea level rise may rank as the simplest tasks to deal with.
So far, rather predictably, the reaction to the report seems to resolve around preconceived attitude and how one tends to lens the world. As others have implied in an earlier thread, pure unadulterated science transcends rhetoric. Move to science applied, and politics rears a head. (The Boortz fellows web site left me shaking my head.)
As an aside, reading the many earlier threads as of late, on real climate, has been quite time consuming�yet worthwhile. To see such discourse, with some well founded scientific explanation and outlinks�I am thankful.
Thanks for your comment. I wanted reassurance, with the thaws happening much quicker now vs the thaws in Earth’s history and those which didn’t involve Greenland and Antarctica. I’ve seen photos of the mud flats near near Anchorage, apparently from rebound. I was surprised by the magnitude of the lifting in that area. Maybe there’s more at work near Anchorage than rebound – like the giant quake they had in the 1960s.
Typo police:
I assume you meant to type underpredicted. Keep up the good work!
[Response:Thanks! – gavin]
Does the IPCC address the recent paper by Lyman et al., documenting ocean cooling the past couple years? Or has this work been dated already by more recent data?
I do not know if anyone will ever work out the evidence, but this lay reader is assured the contributors of Real Science have been a strong support for the work of hundreds of scientists who have worked to make the report of or to the IPCC the best science can do. This is due to the steadfast centering function RC has performed. Unhappily it will now be needful to prepare for the attacks of a crowd of ideologues who are even worse than the gang that could not count, the economists. I guess someone will come forward, but they will have quite a job to measure up to the standard RC has set. Three cheers and a tiger.
Climate change. Maybe man made maybe not! But what does it matter. We obviously will have to make some tough decisions!
Let me pose a Question?
Lets say there is a large asteroid discovered on a collision course with earth!
At that time, we may have many ways of which to stop this catastrophe. But maybe just maybe this is our only oppotunity to reverse the global warming issue by allowing it to strike! Therebye starting a new iceage.
Are we ready to assume all resposibility for mankind who seems to be more concerned about whats causing global warming then the ultimate effects of sustained ignorance will lead us.
Some day we will have to decide!
It may mean that we lose half of the earths population but mankind will endure.Or will we?
#11: data for Greenland and Antarctica are messed up for the 1961-2003 period as well (factor of 10 too high). I guess those data were in mm/year instead of m/century (cf. the editing note above the table that they forgot to remove). Probably American authors, for them mm are units from Mars, like Btu/ft2/h for us Europeans.
RE #12, yes, every little bit helps. So print these 21 pages on used paper, if possible, or doubled-sided on recycled paper. I get my used paper at the university library, mainly page separator sheets, and it’s high grade. First REDUCE, second REUSE, third RECYCLE.
I forgot what the cut-off date was for the journal articles included in AR4. Was it June 2005 or 2006?
I always take these reports as being on the conservative side of conservative, since they require great consensus, beyond the typical conservative (false-positive avoiding) single scientific studies. I think the cutting edge studies of dangerous predictions would indicate greater harms than what IPCC indicates (though the reports do include ranges, but may excluded the highest ends).
Another point, each succeeding report not only reveals greater precision in the science, but also that global warming is more potentially dangerous than experts had earlier thought. I might be wrong, but that’s the sense I get.
Ark, You’re right. They apparently screwed up the Antarctic contribution for 1961-2003 as well in Table SPM-0. Also, if you assume they meant 0.014, the numbers in the 1961-2003 column don’t add up (i.e. .042+.05+.05+.014 = .156, NOT .11 as they have in the table)
[[Now that you are one of those who are either ignorant beyond all help or just a pathological liar, do you have any other excuses for being a fear monger?
Just asking… ]]
Stay off the sauce when you post. It improves the quality of your prose.
Where is the discussion of natural variability in all this? There is of course the minor contribution of solar irradiance but the changes over the ENSO cycle, over decadal timescales and over longer period don’t rate a mention. The decadal variance in particular is dismissed at Wikapedia as climate noise and addressed on this site as a single paragraph and a blind link. How is this possible?
The cyclical changes in global temperature and climate more generally over periods of decades – to 1946, 1947 to 1975 and 1975 to 1998 in the instrument record – and, from proxy data, occuring 11 times in the past 400 years with an average duration of 23 years.
FAR predicts a 0.2 degree C/decade rise in temperature over the next couple of decades. The history of decadal variability suggests that temperatures will decline (since 1998) over the next couple of decades – well before which the entire science community is utterly discredited. Don’t believe me – this is very simple experiment and one that doesn’t require 5000 of the world’s leading scientists.
Random fluctuation is not much of an explanation for such a persistent and influential phenomenon. I feel like being very rude but will of course refrain. Feel free to claim that the temperature decline since 1998 is random climate noise – pretty much as the CRU did on New Years Day 2007 when claiming, after 2006 came in at the sixth warmest year, that 2007 will surely see the upward trend return. I am not likely to be listening until I see the data.
Says RK Pachauri, DG, The Energy and Resources Institute & Chair IPCC: “A number of scientists say Siachen should be made a protected area, a heritage site of sorts, and that there should be no army presence on either side. For purely ecological reasons, this *might* be a good idea. But I *don’t* see why there would be melting as a result of military presence and activity.” The *s show a vagueness unworthy of an environment leader who ought to ask for withdrawal of all troops immediately’
Please Cleck to see how indian and Pakistan Army melting Siachen glacier
http://www.zeenews.com/articles.asp?rep=2&aid=345084&ssid=26&sid=ENV – 58k –
http://www.wwfpak.org/15-01-07meltingofthesiachenglacier.php – 32k – Cached – Similar pages
in.news.yahoo.com/061230/211/6apcs.html – 39k – Cached – Similar pages
http://www.thenews.com.pk/daily_detail.asp?id=38553 – 21k – Cached – Similar pages
While you can appreciate the representation of scientific knowledge, available late 2006, in this IPCC report, you might wonder how it will affect the political decision-chain. Here in the Netherlands, the rather conservative estimates on sea-level-rise already led to (secondline) features in the national television news show, in which the one-line statement “Holland will not be flooded…” sounded like a sense of relief. But even without accounting for possible dynamic changes in icecaps the consequences stated in the report make clear there is not much relief while reading carefully. My point is that it is not just a question of how much sea-level-rise will occur. Agricultural and land-use change, growing salinity of groundwater and estuaries, re-arranging drinking-water facilities, changing character of rivers etcetera. This will put an ever growing strain on our national budget. Not to mention the help we might want to offer in less fortunate regions in the coming world. It is time to be clever and to accept that it might cost us a considerable amount of our “business as usual” to cope. I just hope the full fourth assessment will contribute to that awareness!
Any significance to the fact that the report was released on Grounfhog Day? “If the groundhog sees his shadow, there’ll be another six weeks of winter.” (Probably as valid as some of the exquisitately accurate computer modelling with questionable input data.)
Sea stand rise — On another thread, Nigel Williams asked for a 500 year prediction. I offered 7 m for the melting of the Greenland ice sheet and up to 20 m (conservatively high) for the melting of the West Antarctic ice sheet. So minor adjustments due to isostacy and tectonic rebound are just too insignificant to consider when faced with a long-range prediction of 22–27 m.
One query concerns precipitation. In a warmer world the oceans will warm, causing more evaporation. The warmer air will be able to hold more water. Therfore one would expect a greenhouse world to be a lot wetter. Yet the report forecasts droughts and reductions in rainfall most places.
This is odd, especially in the tropics where there will be a lot of extra precpitation looking for somewhere to go. Where will it all end up?