Nature: Global Temperatures Are a Falling Trend 786
New submitter sosume writes "An article in Nature shows that temperatures in Roman times were actually higher than current temperatures. A team lead by Dr. Esper of the University of Mainz has researched tree rings and concluded that over the past 2,000 years, the forcing is up to four times as large as the 1.6W/m^2 net anthropogenic forcing since 1750 using evidence based on maximum latewood density data from northern Scandinavia, indicating that this cooling trend was stronger (0.31C per 1,000 years, ±0.03C) than previously reported, and demonstrated that this signature is missing in published tree-ring proxy records."
Re:Headline should say... (Score:5, Informative)
Re:Headline should say... (Score:4, Informative)
There are several instances where the kick up sharply throughout the last 2000 years.
El Reg anti-AGW propaganda again (Score:3, Informative)
Temperatures were lower than in Roman and medieval times, and falling... until the recent warming kicked in.
This is yet another hockey stick. I can't see how the Register is turning it into anti-AGW propaganda. Read the Nature article, not the Register.
Re:Headline should say... (Score:1, Informative)
Nothing in the TFA even comes close to disproving the "hockey stick" graphs of climate and warming trends.
AGW is affecting us, no matter how deep our heads go in the sand. It is just how much -- if we cook too much life in the sea that produces 70-95% of our oxygen, then we will end up with a nice global extinction event.
Summary Is Woefully Incorrect (Score:4, Informative)
A team lead by dr Esper of the University of Mainz has researched tree rings and concluded that over the past 2,000 years
That's odd, according to the image from the paper [nature.com] the trend in question is from 138 BC–AD 1900. Of course, after reading the Guardian article, it's clear that the only papers in Nature worth this "reporter's" time are those that confirm his professional opinion on the state of global temperatures. Tell me, why exactly didn't they construct a trend from 138 BC–AD 2012? Was that 1900-2012 range more difficult to acquire for some hilarious reason? I mean, the data is in the graph right there.
You can select special time ranges, you can select windows and you can look at millions of years of data and say that temperatures right now are no big deal. But when you start to look at the rate of change (even in the paper's graph linked above) and you notice recently we're starting to approach rates that are increasingly less frequent in the historical record, I think it's okay to start to talk about what could be causing it. I mean now we're talking about the last two thousand years and yeah, that's an acceptable window but if we never swing back down below to average it out, at what point are you going to admit that the theory of C02 affecting global average temperatures has some weight to it? Trust me, if we increase by 2 degrees Celsius, you can increase this window back five millennium and say "Hey, they used to have temperatures warmer than we do now." It's entirely possible to endlessly play this game by moving the goal posts. But I don't think the Earth is going to be able to adapt as well as humans do to rapid change. I guess the only thing that can convince people is time and repercussions that actually inconvenience humans.
Re:Headline should say... (Score:5, Informative)
These findings, together with the missing orbital signature in published dendrochronological records, suggest that large-scale near-surface air-temperature reconstructions9, 10, 11, 12, 13 relying on tree-ring data may underestimate pre-instrumental temperatures including warmth during Medieval and Roman times.
In other words: estimates of temperature in medieval/Roman times based on tree ring data may well be too low.
Re:An inconvent truth (Score:2, Informative)
I guess you've never heard of ocean acidification [wikipedia.org]?
Re:Headline should say... (Score:4, Informative)
I don't know which graph you are looking at, but the one in TFA shows several instances of abrupt rises in temps, or, hockey sticks if you want...at least six.
Re:El Reg anti-AGW propaganda again (Score:4, Informative)
Looking at the graph you can see at least 6 instances of abrupt temperature increases and at least 5 times temps exceeded the trend.
In that context, our recent increases are not unique. If you want to pin the recent increases on Man, then you need to explain how the past increases came to be and why the current increases are not driven by the same forces.
Misleading (Score:4, Informative)
Real Climate has a much more interesting take on the paper:
http://www.realclimate.org/index.php/archives/2012/07/tree-rings-and-climate-some-recent-developments/ [realclimate.org]
Finding the weak points in various temperature proxies and using that knowledge to improve the overall accuracy of the temperature record is a good thing, and a normal part of the scientific process. Sensationalist reporting of the type The Register engages in just serves to inflame the debate without adding anything useful to the discussion.
Re:Headline should say... (Score:5, Informative)
Indeed, RealClimate notes [realclimate.org] that if you remove dendrochronology records from Mann et al (2008), you actually get a lesser pre-industrial cooling trend [realclimate.org]. Of the dozens of independent lines of evidence, tree rings have long been one of the *least* suggestive of disproportionately high GHG forcing versus other forcings, so it's always funny to see them called out as though the case for global warming rests on them. ;) (The reason that they're often called out is because they're *really tricky* to use well; so many things affect tree growth that have to be accounted for, and the factors vary greatly from location to location)
Re:ARG (Score:3, Informative)
http://wattsupwiththat.com/2009/10/30/yamal-treering-proxy-temperature-reconstructions-dont-match-local-thermometer-records/ [wattsupwiththat.com]
http://pielkeclimatesci.wordpress.com/2010/05/17/comments-on-the-tree-ring-proxy-and-thermometer-surface-temperature-trend-data/ [wordpress.com]
Basically, tree ring width is sensitive to a LOT of factors, and generally, temperature doesn't affect them nearly as much as these other factors. Using tree rings as a proxy data is analogous to using a car's radiator temperature to determine its speed. It certainly affects it, but the signal is pretty low and the noise is rather high...
Re:Headline should say... (Score:5, Informative)
No, the burden of proof is always on the person making the affirmative statement. It's usually very difficult to prove a negative. However, in many cases we're willing to accept a theory that makes sense and fits all the observed data.
Does anyone even read primary articles? (Score:5, Informative)
And before I jump into the paper can we clearly define what journal an article is published in? Saying "Nature" is misleading. It's "Nature: Climate Change". Not similar, at all.
The paper is a methods paper. It's outlining a very interesting way to get at fine-resolution temperature fluctuations on a not-so-far-back time scale. Additionally, the moving average rise in temperature isn't suggesting it was HOTTER back then than now (as this submission and the press release indicate) but that instead our ESTIMATES of how hot it was are off.. SLIGHTLY. How far off? Here, let me copy primary literature for you. I hear that's good journalistic practice.
"...These findings together with the trends revealed in long-term CGCM runs suggest that large-scale summer temperatures were some tenths of a degree Celsius warmer during Roman times than previously thought. It has been demonstrated4 that prominent, but shorter term climatic episodes, including the Medieval Warm Period and subsequent Little Ice Age, were influenced by solar output and (grouped) volcanic activity changes, and that the extent of warmth during medieval times varies considerably in space. Regression-based calculations over only the past millennium (including the twentieth century) are thus problematic as they effectively provide estimates of these forcings that typically act on shorter timescales. Accurate estimation of orbitally forced temperature signals in high-resolution proxy records therefore requires time series that extend beyond the Medieval Warm Period and preferably reach the past 2,000 years or longer6. Further uncertainty on estimating the effect of missing orbital signatures on hemispheric reconstructions is related to the spatial patterns of JJA orbital forcing and associated CGCM temperature trends. First, the simulated temperature trends, indicating substantial weakening of insolation signals towards the tropics, can at present be assessed in only two CGCMs (refs 7, 8). More long-term runs with GCMs to validate these hemispheric patterns are required. Whereas the large-scale patterns of temperature trends seem rather similar among the CGCMs, the magnitude of orbitally forced trends varies considerably among the simulations. Additional uncertainty stems from the weight of tree-ring data and varying seasonality of reconstructed temperatures in the large-scale compilations. Although some of the reconstructions are solely composed of tree-ring data, others include a multitude of proxies (including precipitation-sensitive time series) and may even include non-summer temperature signals. Some of these issues are difficult to tackle, as the weighting of individual proxies in several large-scale reconstructions is poorly quantified. The results presented here, however, indicate that a thorough assessment of the impact of potentially omitted orbital signatures is required as most large-scale temperature reconstructions include long-term tree-ring data from high-latitude environments. Further well-replicated MXD-based reconstructions are needed to better constrain the orbital forcing of millennial scale temperature trends and estimate the consequences to the ongoing evaluation of recent warming in a long-term context."
I wish I could just copy past the whole article into peoples brains and make them understand the difference between science and sensationalism.
Opinions differ...and that's science (Score:4, Informative)
When Al Gore and other politicians start saying 'the time for discussion is over' on such a complex subject, technically-trained people know that the time for discussion and study is just starting. This article summarizes an interesting study that points to warmer temperatures in roman times. Archaeological studies also support this. For example, many of the seaports that those Romans used are now far inland thanks to a lower sea level due to cooling temperatures. AGW believers minds are firmly closed to any idea that does not include imminent peril from 'hockey-stick' warming. The reality is that the support for AGW caused by atmospheric carbon dioxide concentrations rests on very crude computer models of the global climate that will probably be the subject of horse laughs 50 years into the future.
Re:Scandinadvia is less than 0.3% of the world... (Score:4, Informative)
The Micheal Mann hockeystick used in An Inconvenient Truth is substatntially located aroudn th e same lattitide, using European and Russian trees. So if you are going to call this into question, you have to also call Mann's hockey stick into question. Ironically, they will both live or die together. What this paper does is correct for orbital mechanics, so in a way, it is a refinement that tilts the hockey stick a bit.
Re:Cool. (Score:5, Informative)
It's important you realize that the majority of photosynthesis doesn't include trees, see for example algaes: http://en.wikipedia.org/wiki/Carbon_sink [wikipedia.org]
Additionally, our cars are not even a blip on the global scale for carbon output: http://www.dailymail.co.uk/sciencetech/article-1229857/How-16-ships-create-pollution-cars-world.html [dailymail.co.uk]
Furthermore, while it isn't on a global scale, we've basically stopped having a negative impact on forest sizes here in the US for a while: http://www.wendmag.com/greenery/2011/02/the-u-s-has-more-trees-now-than-100-years-ago/ [wendmag.com]
Next, many of the sources of greenhouse gases are unrelated to burning things, and just normal biological processes which are involved in food PRODUCTION: http://science.howstuffworks.com/environmental/life/zoology/mammals/methane-cow.htm [howstuffworks.com]
Food for thought (pun intended), but I'm not challenging your goals, just want you to be more informed in your arguments or you make yourself and any others that hold your views look bad.
Re:Headline should say... (Score:5, Informative)
Rome had a Mediterranean wide economy based in coastal cities. It was dependent on Egypt for food.
Re:Simple Explanation: (Score:2, Informative)
We're basically entering an ice age
please provide a source when making claims. how can you tell? maybe some model is predicting it, but if we go by model predictions of the world, it would have ended many times already. acid rain, san andreas fault, ozone layer, massive famine, extinction of 90% of all species, some examples of the scaremongering you are willingly a part of.
Re:Headline should say... (Score:5, Informative)
Re:Scandinadvia is less than 0.3% of the world... (Score:4, Informative)
Re:Simple Explanation: (Score:5, Informative)
An article in Scientific American back around 2003-2004 (I forget when exactly) covered work that seemed to show that indeed, we were not only overdue for another ice age, but we had begun going in back a few thousand years ago. But the advent and epansion of farming (which has a tendency to warm things, for several reasons discussed in the paper/article) increasingly mitigated the cooling trend. The variance between actual temperatures and predicted temperatures for entering into an ice age was linear with the expanding acreage of farmland. So the author argued that we have been staving off the next ice age for some 4000 years. He had citations, sorry I'm too lazy to go back and find the article.
Re:Manmade climate change is centuries old (Score:4, Informative)
A couple of relevant posts from The Register (Score:5, Informative)
"Oolons
Did Lewis read the same paper?
Thanks to the link below I got to read the actual paper - the standard of reporting on this issue is atrocious. The paper looked at tree data from a small area of Scandinavia. Also pointing out that they have experienced a lot less warming in recent years than other northern areas.... Hmm do you think that may be true 1000's of years ago - it could have been warmer or cooler than the global average we don't know. So for CLIMATE in Lewis's article read WEATHER, i.e. Local effects for which it is extremely inaccurate to extrapolate to the world. Glad my knee jerk feeling that this was a daft extrapolation has been verified by the paper."
and
Anonymous Coward
Paper says:
"These findings, together with the missing orbital signature in published dendrochronological records, *suggest* that large-scale near-surface air-temperature reconstructions9, 10, 11, 12, 13 relying on tree-ring data *may* underestimate pre-instrumental temperatures including warmth during Medieval and Roman times."
Lewis says:
"CLIMATE WAS HOTTER IN ROMAN, MEDIEVAL TIMES THAN NOW: STUDY"
flame on...
Re:Manmade climate change is centuries old (Score:4, Informative)
Re:Headline should say... (Score:5, Informative)
WRONG the sceptics demand a continued rise in CO2 in the air. The scientists demand no further increases in CO2 concetrations.
Close, but no cigar. The skeptics don't demand a continued rise in CO2, and you would likely be hard-pressed to find an AGW skeptic who believed that we should stop R&D toward the goal of reducing CO2 emissions. What the skeptics are saying is that the "OMG! OMG! CATASTROPHE! Divert all money into halting CO2 emissions NOW! (and keep giving us grants so we can continue to produce doomsday predictions) or we're all DOOMED!" attitude of the AGW proponents would have us all throwing money down a rathole, diverting huge amounts of funds from actually doing something useful in our depressed economies and using it for programs that won't have the benefits the warmists are claiming.
Re:Headline should say... (Score:5, Informative)
The problem is that this isn't relevant to the social issue of global warming, and many "skeptics" will claim that it is relevant. Even if the change in temperature ends up being a blip on the radar in geological time, it only takes a few years of drought to decimate food stores and cause a world-wide pandemic. THIS is the issue that should be relevant to us these days, and I'm afraid that all these newly minted arm-chair scientists (more accurately described as big business apologists) are going to ensure that we delay action until it is too late.
Another thing I should say is that we have a very reliable model for showing that increased CO2 can cause warming on a small scale.
First off, your scare-mongering helps no one and nothing. The work presented in this paper includes the claim that past climate forcings have been up to four times as large as the current 1.6 W/m**2 that is due to antropogentic CO2 since 1760.
Let me repeat that for everyone who missed it: there have been extended periods--centuries--in the past that have experienced orbital climate forcings that are up to 6.4 W/m**2 as opposed to our current 1.6 W/m**2. The proxy temperature also shows sharp upward jumps of the kind that appear in the 20th century.
If you deny this, you are denying scientific evidence. Feel free to do so if that's what your politics dictate, but don't pretend you're defending science in the process.
It follows from this that the Earth's ecosystem, the polar bears, and so on, are capable of weathering the kind of thing we are doing to the world. This is what the science is telling us. Human economies may be more fragile. Or not.
Secondly, your claim that we have "a very reliable model" of the complex non-linear system that is the Earth's atmosphere and oceans is simply false. We have a set of more-or-less unphysical models that contain all the science we can find, but are still parameterized and approximated in ways that make computational physicists shudder. These models have not been developed by computational physicists but by climatologists, and that's a problem.
None of this is to say that we should go on dumping gigatonnes of garbage--including CO2--into the atmosphere. But this cherry-picking of the scientific results is about 10% as bad on the pro-AGW side as the anti-AGW side, and that's pretty damned bad. No matter who wins, science loses.
Re:Headline should say... (Score:4, Informative)