 are on course to be as hot as at any time since the last ice age.)
GETTING WARMER: Earth's temperatures (here seen by an infrared sensor on the NASA satellite Aqua) are on course to be as hot as at any time since the last ice age.
Image: Image courtesy AIRS Science Team, NASA/JPL
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The Best Science Writing Online 2012
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Global average temperatures are now higher than they have been for about 75% of the past 11,300 years, a study suggests. And if climate models are any indication, by the end of this century they will be the highest ever since the end of the most recent ice age.
Instrumental records of climate extend back to only the late nineteenth century. Beyond that, scientists depend on analyses of natural chronicles such as tree rings and isotope ratios in cave formations.
But even these archives have their limits: many detailed reconstructions of climate, particularly of temperature, apply to only limited regions or extend back at most a couple of millennia, says Shaun Marcott, a climate scientist at Oregon State University in Corvallis.
Marcott and his colleagues set about reconstructing global climate trends all the way back to 11,300 years ago, when the Northern Hemisphere was emerging from the most recent ice age. To do so, they collected and analyzed data gathered by other teams. The 73 overlapping climate records that they considered included sediment cores drilled from lake bottoms and sea floors around the world, along with a handful of ice cores collected in Antarctica and Greenland.
Each of these chronicles spanned at least 6,500 years, and each included a millennium-long baseline period beginning in the middle of the post-ice-age period at 3550 BC.
For some records, the researchers inferred past temperatures from the ratio of magnesium and calcium ions in the shells of microscopic creatures that had died and dropped to the ocean floor; for others, they measured the lengths of long-chain organic molecules called alkenones that were trapped in the sediments.
After the ice age, they found, global average temperatures rose until they reached a plateau between 7550 and 3550 BC. Then a long-term cooling trend set in, reaching its lowest temperature extreme between ad 1450 and 1850.
Since then, temperatures have been increasing at a dramatic clip: from the first decade of the twentieth century to now, global average temperatures rose from near their coldest point since the ice age to nearly their warmest, Marcott and his team report today in Science.
Climate context
The temperature trends that the team identified for the past 2,000 years are statistically indistinguishable from results obtained by other researchers in a previous study, says Marcott. “That gives us confidence that the rest of our record is right too,” he adds.
Marcott and his colleagues “have put together a pretty impressive set of climate proxies”, says Gavin Schmidt, a climate scientist at the NASA Goddard Institute for Space Studies in New York. “The overall climate picture has been clear for a long time, mostly from the Northern Hemisphere, but this compilation really puts the rest of the world in context,” he adds.
“Prior to this study, researchers could only guess whether global temperatures had exceeded the warmest part of the present interglacial period,” says Darrell Kaufman, a geologist at Northern Arizona University in Flagstaff. The latest findings show that the recent high temperatures are not necessarily the warmest, but they are unusually high, he notes.
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16 Comments
Add CommentDEEPEST kudos - really the BEST long-term study ever.
Reply | Report Abuse | Link to thisShouldn't be long before the industry shills go berserk as never before.
GREAT job.
You can blame it on aliens stopping in to dispose of their excess CO2, but whatever the cause the increase since 1850 has been more rapid than other trends in the past. Man would clearly not do such a thing, since we have always been such good stewards of our home planet.
Reply | Report Abuse | Link to thisThe article mentioned that a cooling trend abrubtly ended between 1450 and 1850. We are in a fairly long interglacial period.If the cooling trend had continued, would we be encountering glaciation now - if not when? It's scary to lose the coasts to rising sea levels, but glaciers descending to 40 degree North latitude aren't very favorable to Western civilization either. Has anyone determined the timing and effects of our "natural cycle" of re-glaciation?
Reply | Report Abuse | Link to thisAt the time I posted the comment it would have been impossible to read the whole work, I don't like e-book versions of works I cannot annotate and the physical book is not on the market yet AFAIK.
Reply | Report Abuse | Link to thisThe reason why I commented positively is that I know a number of the works used and they are all scientifically sound beyond reasonable doubt. I would also guess that the Berkeley Earth Surface Temperature (BEST) project helped substantially and I rather respect what they do.
The reason why I am so positive is not that the authors themselves have provided groundbreaking new details, they haven't, their huge merit is to have compounded many disparate works from many not always deeply interacting fields into one big piece and drawn the unescapable conclusions.
I guess it will be a standard in the field.
The essential AGW debate is closed, scientific agreement is near unanimous today, what remains questionable are nun-fundamental, nevertheless important aspects of it. In this context this work has IMO the merit to provide proper scientific argumentation laying to rest the recurrent comments on the long-term validity of climate data and their interpretation.
Therefore IMO a fantastic job.
Great.... now we're down to 4 suck-up comments from 102 comments that asked legitimate questions about the quality of the research in this paper and pointed out massive flaws contained within it.
Reply | Report Abuse | Link to thisThe censors are having a hoot. Goodbye SCIAM, I hardly knew ye! When you turn out the lights on the building you can blame your own censors.
SA Editors, if you only want comments from your special lackeys, probably for fear of being made to look foolish, just close down the 'comments' section.
Reply | Report Abuse | Link to thisAlternatively, perhaps you can give jctyler and sault special lackey passwords, so only they can comment. Wouldn't want any opposing discussion. .
"I have this OCD thing against censorship"
Reply | Report Abuse | Link to thiskid shown your comment
http://www.youtube.com/watch?v=RP4abiHdQpc
As I stated in an earlier comment, only to have it censored by the editors, anyone who wishes to post a demand that Scientific American post a retraction of this article be made based on its numerous contained fatal flaws please contact the editors at :
Reply | Report Abuse | Link to thiseditors@sciam.com
Note to the editors: You can keep censoring this post if you want, but I have made a copy of it and will re-post it when I see that it has been censored again. I have this OCD thing against censorship, and shoody science, so the only way that you will stop me from posting it is to ban me from your website.
NOTE: THIS COMMENT HAS BEEN CENSORED SEVERAL TIMES. THIS SERVES AS AN EXAMPLE OF THE BIAS OF SCIAM EDITORS.
I strongly appeal to the SciAm editors to start filtering the comments by quality and scientific relevance. Or at least intelligence and wit.
Reply | Report Abuse | Link to thisFor example could I do without present comment nr 8 as it adds nothing to the topic, neither scientifically nor intellectually nor even humourously.
As a subscriber who loves the additional benefits of the online edition I must admit that I read the comments with great interest. But I must wonder about the climate articles comments sections. These are often inundated by mass comments from two main groups.
The first are professional PR agents working for the polluting industry and attempting to make believe by the sheer number of their comments that there is a strong opposition to better environmental laws in the US. Which as all recent polls prove is not true anymore. Nevertheless, every year gained by the PR people is a billion-dollar windfall for the company owners and therefore for them worth every cent invested into PR campaigning, regardless of how wrong its contents are. These are often recognizable by their quoting outdated (generally pre-2006) links and reports and pseudo scientific talk.
The second group is made near exclusively of people who in some years past had for one reason or the other decided that AGW was an error but then missed the right moment to change their minds and are now stuck in this for them impossible situation not to know how to admit their errors without in their opinion losing face. These commenters exhibit behaviour usually known from religious fanatics.
Neither group is open by nature to scientific proof or argumentation. No logic or fact will change professional anti-AGW campaigners or the qua religious fanaticism of AGW deniers.
The scientific agreement on AGW is practically unanimous, details need to be debated. In this sense it is absolutely counterproductive to allow anti-AGW comments to outnumber intelligent comments for the sake of a PR pay-check or some denier's personal pride.
I could live with some commenters bringing a touch of humour into it but I do abhorr the eternal humourless, illogical whining of those who feel that climate creationism is an option.
I therefore appeal to the editors to filter the comments more selectively in the interest of those who read these postings for new ideas, alternative news and intelligent remarks.
No need to pester the editors, simply show your agreement in whatever way suits you by posting a supportive comment.
Editor: Comment #9 is opinion only and completely irrelevant to the subject matter.
Reply | Report Abuse | Link to thispostman:
Reply | Report Abuse | Link to thisIf you had said that Shoshin's "demand that Scientific American post a retraction of this article" is inacceptable simply because he does not believe in AGW one might have read your future comments with slightly more respect.
But why do you instead attack a neutral comment demanding that SciAm editors filter more qualitatively? Isnt' that what you always wanted, that stricter, more scientific criteria be applied to comments? Why do you feel that this applies particularly to your comments or anti-AGW commenters in general?
As is, although your comment could suggest you being a particularly devious member of the first group because you use off-topic commenting when logic fails you I don't believe you are for the simple reason that your posts do not fit the profile of the professional anti-AGW commenter. Not that they are too obviously errored, present-day anti-AGW comments usually are, they are simply too obviously driven by personal motives against people disagreeing with your opinion of yourself.
Therefore I must conclude that you have now definitely outed yourself as a member of group two = commenter being anti-AGW for personal reasons.
I do give you credit for honesty though, because intentional or not, you always appear as what you are.
For example, when you write "Editor: Comment #9 is opinion only and completely irrelevant to the subject matter"
...
what can I say about you that you don't?
I used to read scientific american as a youngster. I am disturbed by the apparent lack of scientific method surrounding the AGW discussion here and elsewhere on this site. The title of this article. "Global Average temperatures are close to 11,000-year peak". As if 11,000 years is a long period of time in the ice age cycle. Isn't the accepted ice age cycle 100,000 years or more? Wouldn't we expect to have warming when not in a glacial period? As for comments like "the scientific agreement on AGW is practically unanimous" without citing to anything is disturbing to. I have read the IPCC and all it concludes is that the net effect of humans is that of warming without even an attempt at quantifying that effect. It is also well accepted that H2O is a much more extensive greenhouse gas than CO2 as to make the CO2 percentage contribution negligible. And no I am not a lobbyist for the petroleum industry just a scientific american evaluating the basis for the theories. Is Scientific American a publication dedicated to objective scientific study or do they have an agenda?
Reply | Report Abuse | Link to thisSciAm's agenda is far too lax as I am concerned. Strange people with strange ideas should not even be allowed to swamp the comments sections with their increasingly detached surreal climate ideas. Why not bring in the big bang and its instant-tanning qualities? Grow a long, white beard and you'd make a perfect apostle of the New Church of Climate Creationism.
Reply | Report Abuse | Link to thisEvery AGW "doubter" comes up with his own strange standards, changes the perimeters as it suits him, demands that every scientist on the planet accept his opinion as the gospel or be damned forever. When climatologists show that the last ten years were the warmest in modern history, you try to discredit them with irrelevant ice data. When they look at 20-year cycles you pretend these are too short. Now a conclusive work covers 11 000 years, suddenly that is not long enough. Then they compare cycles within human history and you fire back with eras where human life was not even possible because of heat and CO2 to prove that Earth was hotter and dirtier already. You simply forget that in those times you mention human life was not possible and cannot be used for comparison.
Which is exactly what you are proving by your comment, whichis the contrary of what you are trying to say. Only look at the two black holes in your feet.
If you had continued to read SciAm after your youth you would have stayed up-to-date on the evolution of climate science and possibly not be tripping over your ignorance now.
Or are you one of the climatewazza fans? If you desperately want to be funny you could mention that the Cambrian was far hotter and had 20 times more CO2 than today and then say with absolute conviction that human evolution was helped by those conditions or the cockroaches would have taken over.
You change your standards and test perimeters any way suits you. Which is the contrary of scientific and therefore not admissible. Insisting on your approach disqualifies you from scientific discourse. In short, your comment is invalid. In short, your opinion of yourself is not accepted proof for the validity of your comment.
And your attempt at discrediting SciAm is so pathetic one is embarrassed for you. You provoke what the Germans call "Fremdschämen". Embarrassing strangers is not very nice. But you will get half decent notes for brave attempt at entertaining class.
German readers in Frankfurt:
Reply | Report Abuse | Link to thisI hear there is a superb exhibition in the Senckenberg Museum
„Planet 3.0. Klima, Leben, Zukunft: Eine Zeitreise durch den Klimawandel“
(Planet 3.0. Climate, Life, Future: a time travel through climate change)
Link to this exhibition:
Reply | Report Abuse | Link to thishttp://www.senckenberg.de/root/index.php?page_id=5206&PHPSESSID=qo7dcvavld3g2lfebd6tqjnvuilk4e07&kid=1&id=2666
I wonder how much effect the increase in the accumulated thermal output of man made items have on the temperature of the world. In the past I've asked this question, and had volcanos cited as worse contributers. If this is the case, I have two further questions: 1) Does increased tectonic activity imply an impending polar reversal? and 2)Has there been a noteworthy increase in volcanic eruptions in the past century?
Reply | Report Abuse | Link to this