How Bad Is Global Warming?

[wintler2]

Global climate change and children's health: threats and strategies for prevention.
http://www.ncbi.nlm.nih.gov/pubmed/20947468

Environ Health Perspect. 2011 Mar;119(3):291-8. doi: 10.1289/ehp.1002233. Epub 2010 Oct 14.
Sheffield PE, Landrigan PJ.
Department of Preventive Medicine and Pediatrics, Mount Sinai School of Medicine, New York, New York, USA. perry.sheffield@mssm.edu
Abstract
BACKGROUND: Global climate change will have multiple effects on human health. Vulnerable populations-children, the elderly, and the poor-will be disproportionately affected.

OBJECTIVE: We reviewed projected impacts of climate change on children's health, the pathways involved in these effects, and prevention strategies.
DATA SOURCES: We assessed primary studies, review articles, and organizational reports.
DATA SYNTHESIS:
Climate change is increasing the global burden of disease and in the year 2000 was responsible for > 150,000 deaths worldwide. Of this disease burden, 88% fell upon children. Documented health effects include changing ranges of vector-borne diseases such as malaria and dengue; increased diarrheal and respiratory disease; increased morbidity and mortality from extreme weather; changed exposures to toxic chemicals; worsened poverty; food and physical insecurity; and threats to human habitation. Heat-related health effects for which research is emerging include diminished school performance, increased rates of pregnancy complications, and renal effects. Stark variation in these outcomes is evident by geographic region and socioeconomic status, and these impacts will exacerbate health disparities. Prevention strategies to reduce health impacts of climate change include reduction of greenhouse gas emissions and adaptation through multiple public health interventions.

CONCLUSIONS: Further quantification of the effects of climate change on children's health is needed globally and also at regional and local levels through enhanced monitoring of children's environmental health and by tracking selected indicators. Climate change preparedness strategies need to be incorporated into public health programs.

[Ben D]

http://www.dailygalaxy.com/my_weblog/2013/09/ecoalert-milky-ways-cosmic-rays-have-direct-impact-on-earths-weather-climate.html

EcoAlert: "Milky Way's Cosmic Rays Have Direct Impact on Earth's Weather & Climate"

September 04, 2013

A fascinating new theory states that cosmic rays coming from our Milky Way Galaxy are directly involved in the Earth's weather and climate, according to Henrik Svensmark, lead author of the new study with the Technical University of Denmark. "In experiments over many years," he says, "we have shown that ionizing rays help to form small molecular clusters. Critics have argued that the clusters cannot grow large enough to affect cloud formation significantly. But our current research, of which the reported SKY2 experiment forms just one part, contradicts their conventional view. Now we want to close in on the details of the unexpected chemistry occurring in the air, at the end of the long journey that brought the cosmic rays here from exploded stars."

According to the theory, small clusters of molecules in the atmosphere have difficulty growing large enough to act as "cloud condensation nuclei" on which water droplets can gather to make our familiar low-altitude clouds. The SKY2 experiment shows that the growth of clusters is much more vigorous, provided ionizing rays -- gamma rays in the experiment or cosmic rays in the atmosphere -- are present to work their chemical magic.
Back in 1996 Danish physicists suggested that cosmic rays, energetic particles from space, are important in the formation of clouds. Since then, experiments in Copenhagen and elsewhere have demonstrated that cosmic rays actually help small clusters of molecules to form. But the cosmic-ray/cloud hypothesis seemed to run into a problem when numerical simulations of the prevailing chemical theory pointed to a failure of growth.

Fortunately the chemical theory could also be tested experimentally, as was done with SKY2, the chamber of which holds 8 cubic metres of air and traces of other gases. One series of experiments confirmed the unfavourable prediction that the new clusters would fail to grow sufficiently to be influential for clouds. But another series of experiments, using ionizing rays, gave a very different result, as can be seen in the accompanying figure.

The reactions going on in the air over our heads mostly involve commonplace molecules. During daylight hours, ultraviolet rays from the Sun encourage sulphur dioxide to react with ozone and water vapour to make sulphuric acid. The clusters of interest for cloud formation consist mainly of sulphuric acid and water molecules clumped together in very large numbers and they grow with the aid of other molecules.

Atmospheric chemists have assumed that when the clusters have gathered up the day's yield, they stop growing, and only a small fraction can become large enough to be meteorologically relevant. Yet in the SKY2 experiment, with natural cosmic rays and gamma-rays keeping the air in the chamber ionized, no such interruption occurs. This result suggests that another chemical process seems to be supplying the extra molecules needed to keep the clusters growing.

Technical University of Denmark FULL PAPER LINK PROVIDED IN THE DTU PRESS RERLEASE:https://dl.dropboxusercontent.com/u/51188502/PLA22068.pdf

Danish experiment suggests unexpected magic by cosmic rays in cloud formation
13 hours ago

[Iamwhomiam]

"This result suggests that another chemical process seems to be supplying the extra molecules needed to keep the clusters growing."

[stillrobertpaulsen]

Global Warming Has Increased Risk of Record Heat

Sep. 5, 2013 — Researchers calculate that intense heat like that in the summer of 2012 is up to four times more likely to occur now than in pre-industrial America, when there was much less carbon dioxide in the atmosphere.


Researchers calculate that intense heat like that in the summer of 2012 is up to four times more likely to occur now than in pre-industrial America, when there was much less carbon dioxide in the atmosphere. (Credit: © Tom Wang / Fotolia)

Drought shriveled crops in the Midwest, massive wildfires raged in the West and East Coast cities sweltered. The summer of 2012 was a season of epic proportions, especially July, the hottest month in the history of U.S. weather record keeping.

And it's likely that we'll continue to see such calamitous weather.

In the north-central and northeastern United States, extreme weather is more than four times as likely to occur than it was in the pre-industrial era, according to a new study by Noah Diffenbaugh, a Stanford associate professor of environmental Earth system science, and Martin Scherer, a research assistant in the department.

Diffenbaugh and Scherer found strong evidence that the high levels of greenhouse gases now in the atmosphere have increased the likelihood of severe heat such as occurred in the United States in 2012.

The researchers focused primarily on understanding the physical processes that created the hazardous weather. They looked at how rare those conditions were over the history of available weather records, going back over the last century.

Then, using climate models, they quantified how the risk of such damaging weather has changed in the current climate of high greenhouse gas concentrations, as opposed to an era of significantly lower concentrations and no global warming. Their findings don't pinpoint global warming as the cause of particular extreme weather events, but they do reveal the increasing risk of such events as the world warms.

"Going forward, if we want to understand and manage climate risks, it's more practically relevant to understand the likelihood of the hazard than to ask whether any particular disaster was caused by global warming," Diffenbaugh said.

In 2012 alone, the United States suffered 11 extreme weather events that each caused at least $1 billion in damage. "It's clear that our greenhouse gas emissions have increased the likelihood of some kinds of extremes, and it's clear that we're not optimally adapted to that new climate," Diffenbaugh said.

While Diffenbaugh cautions against trying to determine whether global warming caused any individual extreme event, the observed global warming clearly appears to have affected the likelihood of record heat, according to Diffenbaugh and Scherer.

The study, looking at the likelihood of July 2012 U.S. temperatures recurring, is part of a larger report edited by scientists at the National Oceanic and Atmospheric Administration (NOAA) and published Sept. 5 in the Bulletin of the American Meteorological Society. The report includes studies of a dozen 2012 extreme weather events by research teams around the world, about half of which found some evidence that human-caused climate change contributed to an extreme weather event.

Close study of extreme weather events can help quantify the likelihood that society will face conditions similar to those that occurred in the summer of 2012, thereby informing efforts to reduce vulnerability and increase resilience. Diffenbaugh argues that the new results can also help to quantify the true cost of emissions to society, since the cost of the disaster is measurable.

"Knowing how much our emissions have changed the likelihood of this kind of severe heat event can help us to minimize the impacts of the next heat wave, and to determine the value of avoiding further changes in climate," Diffenbaugh said.

Funding for this research was provided by the National Science Foundation and the National Institutes of Health.

[Sounder]

Dupe

[Sounder]

Why am I not surprised that nobody chooses to address my missive on pg.44?

This is cross posted from vanlose kids thread because for me it illustrates how the progressive commitment to science has produced some extraordinarily bad thinking. Thinking that seems to have been remarkably consistent and widespread among the ‘leftist’ British socialists.

Here then is a concrete example of elitist (so called progressive) conformity and science combined to produce bad thinking.

Please say it ain’t so; science (and so called progressive thinking) can and does support bad thinking just as well as religion does.


viewtopic.php?f=8&t=36960&start=15

Thus George Bernard Shaw could write: “The only fundamental and possible socialism is the socialisation of the selective breeding of man.” Later he mused that “the overthrow of the aristocrat has created the necessity for the Superman.” The revered pacifist, disarmer and philosophical titan, Bertrand Russell, dreamed up a wheeze that would have made even Nazi Germany’s eugenicists blush. He suggested the state issue colour-coded “procreation tickets.” Those who dared breed with holders of a different-coloured ticket would face a heavy fine. That way the high-calibre gene pool of the elite would not be muddied by any proletarian or worse, foreign, muck. The New Statesman agreed, explaining in July 1931: “The legitimate claims of eugenics are not inherently incompatible with the outlook of the collectivist movement. On the contrary, they would be expected to find their most intransigent opponents amongst those who cling to the individualistic views of parenthood and family economics.” The bottom line is bleak but clear. Eugenics, the art and science of breeding better men, is not just the historical problem of Germany and now Scandinavia, nor even of the jackbooted right. It took root right here in Britain - pushed and argued by the left. Indeed, contempt for ordinary people and outright racism were two of the defining creeds of British socialism.

The trouble began with Charles Darwin. His breakthrough work, The Origin of the Species, did not restrict its impact to the academy and laboratories. Instead it transformed the very way mankind understood itself in the 19th century, its message fast spilling over into the realm of political ideas. Suddenly the religious notion that all life was equally sacred was under attack. Human beings were like any other species – some were more evolved than others. The human race could be divided into different categories and classes. When Karl Marx took on the task of charting human development and defining the class structure, he acknowledged his debt – dedicating an early edition of Das Kapital to none other than Charles Darwin.

From the beginning socialism regarded itself as the natural ally, even the political version, of science. Just as biologists sought to understand animals and plants, so scientific socialism would master people. According to Adrian Wooldridge, author of Measuring the Mind: Education and Psychology in England 1860-1990, and a recognised authority on early ideas of human merit, progressives believed the only enemies of Darwin were reactionaries, the religious and the superstitious. Science, by contrast, represented progress. Crucially, these early leftists regarded science as an utterly neutral tool; something could not be scientifically right and morally wrong. In this climate, says Wooldridge, “eugenics became the political correctness of its day.” If you were modern, you believed in it....

For years, leftists, historians and everyone else have drawn a veil over Adolf Hitler’s naming of his creed National Socialism. It has been dismissed as a perverse PR trick of the Fuhrer’s, as if Nazism and socialism represented opposite faiths. The same view has infused the left’s understanding of the genocides committed in the name of communism, whether by Stalin or Pol Pot, as if those men were merely betraying the otherwise noble theory whose cause they proclaimed. But the early history of British socialism tells a different story. It suggests that socialism – with its unshakeable faith in science, central planning and the cool wisdom of the rational elite – contained the seeds of the atrocities that were to come later.

[Iamwhomiam]

I believe I addressed your missive on the same page, Sounder. But then, more than once you shared your wisdom with us on page 44 so it's possible you're now referring to a different missive than that to which I responded.

Your missive above with its reinforcing cut n paste is dismissive.

We have little to fear from the left today, which should be quite plain to all quasi-informed curious persons, whom I would tend to believe are more than well aware of the now rapidly escalating exacerbating effects they’re experiencing from the everlasting oppression thrust upon them by the right.

I can't argue with someone so divisive as to separate the thought of humans into categories, left-right, for example. Talk about elitists... follow that path and next you'll wind up separating humans, with one or the other feeling superior in thought, Stormy weather-Front-like, and frankly, that's ridiculous.

(By the way, if you haven't caught the flick Pawn Shop Chronicles you should. It is a spectacular social commentary and a fantastic reflection of a tiny segment. If you have, you may understand why I now reference it. It's one of the greatest flicks ever, in my book, and deserving of its own thread.)

[Sounder]

This was my second post on pg 44,

Iamwhomiam, try this maybe.

climate change concern creates a meme among the general population that says ‘our leaders’ have great concern for future generations.

This meme happens to counter and cover for several of the duplicitous needs of power.
First off, it provides a facile reason for calling another person ‘pro-polluter’.
It’s also an excellent antidote to deep politics in general, well because the club of Rome clearly has the best interests at heart for humanity in general.
Was there ever any MSM coverage of the total chemical decimation of Fallujah?
How bout Fukushima? Any news? Corexit? What about the state dept big wigs being sales agents for Monsanto?
Do people who ‘care’ about future generations salt a sizable portion of this world with depleted uranium?

So, this is put to the lie when we see the variety and extent to which power will resort to in order to maintain itself.

Part of that image maintenance involves throwing all kinds of money at various ‘good’ causes. And I’m not being facetious, as quite a lot of the money does seem to do good work.

Yet as Rockefeller, and many megalomaniacs before and after him have found, one can define the agenda if one has a good enough hook.

Rockefellers hook was ‘modern medicine’. Yes, the practice of medicine at the time deserved a fair bit of criticism and there was need for better standards, but what we have at this point is a VERY polluting system, to both individuals at all levels and to the larger environment. We have grown to rely on many long-chain molecules to provide ‘cures’ and to control and design our surroundings.

This was not a ‘necessary’ occurrence; we could live much of even modern life without, or with better formulations and control of the toxic materials.

We are not in control of our situation because as a general population we are passively unaware of the larger forces that shape our psyches.

Our psyches are built around coercion. One might control its effects in ones personal life, but in the big world, it’s fucking everywhere and is indeed quite sickening for both the individual and the entire system. Coercion is the death blood and soul of Thantos.

CO2 is not making the system sick, coercion backed by a vertical authority distribution system is the element that could crash the system.

Think about it, common sense says the system would ‘work’ better if more people had critical thinking abilities, yet a vertical authority distribution system demands that ones thoughts be inhibited so as to show preference the ‘authority’ or mental fashion of the moment.

Now you are welcome to argue with points I make but it is not at all ‘critical thinking’ to mock what is said or to deflect by avoidance, derision or other tricks, so that you do not address the basic assertion that climate change concern (among its sponsors) is a fig leaf that effectively covers some very sordid examples of anatomy.

The preceding sentence references a video posted by a member suggesting that I lacked the critical thinking skills of a two year old.
This sort of thing may discourage other weak willed people from considering the perspective I present, but it’s really quite silly and some folk around here are really quite old enough by now to have grown up more than what it sometimes appears.

After which you posted:

Just wanted to pop-in to let you know I've read your comment, appreciate your sharing it and look forward to sharing my response later, when time allows.

Since then, no response. Which is fine if you so choose.

In regard to your most recent post, the idea being presented in my post was that there is clear precedence for scientism and progressive politics combining to produce some fairly dour results.

So, I made an assertion and backed it up solid and common knowledge.

This is quite distinct from the cut and paste style where no perspective or comments are included with the polished propaganda.

[Sounder]

Hat tip to Delta Dawn

Iamwhomiam wrote...

We have little to fear from the left today, which should be quite plain to all quasi-informed curious persons, whom I would tend to believe are more than well aware of the now rapidly escalating exacerbating effects they’re experiencing from the everlasting oppression thrust upon them by the right.

I want what I think is best for the left, that is for the progressive cause to not discredit itself by over focusing on one issue that effectively negates proper outrage at other issues even though those issues can be largely traced to the same foundations and folk that profited from those other issues and now support AGW.

I can't argue with someone so divisive as to separate the thought of humans into categories, left-right, for example. Talk about elitists... follow that path and next you'll wind up separating humans, with one or the other feeling superior in thought, Stormy weather-Front-like, and frankly, that's ridiculous.

But wait, you just did that in your preceding paragraph. For my part I like to see right and left as stay or go people.

We have both, I assume that we need both and think that some day we will collectively learn to appreciate each others qualities.

That day will come sooner if folk from both sides realize just how big the budget is for the manufacturing of divisiveness through the bending of narratives and other more drastic means.

Peace

[jingofever]

"climate change concern creates a meme among the general population that says ‘our leaders’ have great concern for future generations."

How does that happen when our leaders haven't done and don't intend to do shit about climate change? The only "meme" I'm picking up is that they care about the short term profits of corporations over everything else.

[Ben D]

Apparently the Daily Mail has got their hands on a leaked copy of the final draft of the latest six yearly UN IPCC assessment due to be published by the end of the month and have done a job on it....

Global warming is just HALF what we said: World's top climate scientists admit computers got the effects of greenhouse gases wrong

[Rory]

The Hate Mail? Yawn.

They should stick to what they're good at - demonizing immigrants and liberals while satiating 'politically conservative' older men's desire for vicarious titillation via copious detailed and lurid coverage of sex crimes, illustrated with 'celebrity news' showing in the main, pictures of barely dressed young women

But lets take their word for it when a serious scientific subject its being discussed

For example, this story was ranked above your global warming denier shite

http://www.dailymail.co.uk/news/article ... sport.html

With said sexy pictures, of course

This is my favorite (from a long time ago, to be fair)

[Ben D]

All eyes on IPCC AR5...

http://www.spiegel.de/international/world/climate-scientists-face-crisis-over-global-warming-pause-a-923937.html

Warming Plateau? Climatologists Face Inconvenient Truth

Data shows global temperatures aren't rising the way climate scientists have predicted. Now the Intergovernmental Panel on Climate Change faces a problem: publicize these findings and encourage skeptics -- or hush up the figures.

http://www.thetimes.co.uk/tto/environment/article3877171.ece

Met Office’s climate model is exaggerating warming effect’

The Met Office method of predicting climate change contains flaws that cause it to overestimate the warming Britain will experience, according to a think-tank that opposes urgent emission cuts.

http://opinion.financialpost.com/2013/09/23/lawrence-solomon-lets-play-chicken-little/

Let’s play Chicken Little

Climate change models that claim the world will suffer great harm in future are “close to useless,” pronounces a prestigious new study by Robert S. Pindyck, a physicist, engineer, professor of Economics and Finance at MIT’s Sloan School of Management and true believer in perils from global warming.

[norton ash]

viewtopic.php?f=8&t=31261

[jfshade]

Paleoclimate: The End of the Holocene
Filed under:

Climate Science

— stefan @ 16 September 2013 - (Deutsch)

Recently a group of researchers from Harvard and Oregon State University has published the first global temperature reconstruction for the last 11,000 years – that’s the whole Holocene (Marcott et al. 2013). The results are striking and worthy of further discussion, after the authors have already commented on their results in this blog.

A while ago, I discussed here the new, comprehensive climate reconstruction from the PAGES 2k project for the past 2000 years. But what came before that? Does the long-term cooling trend that ruled most of the last two millennia reach even further back into the past?

Over the last decades, numerous researchers have painstakingly collected, analyzed, dated, and calibrated many data series that allow us to reconstruct climate before the age of direct measurements. Such data come e.g. from sediment drilling in the deep sea, from corals, ice cores and other sources. Shaun Marcott and colleagues for the first time assembled 73 such data sets from around the world into a global temperature reconstruction for the Holocene, published in Science. Or strictly speaking, many such reconstructions: they have tried about twenty different averaging methods and also carried out 1,000 Monte Carlo simulations with random errors added to the dating of the individual data series to demonstrate the robustness of their results.

To show the main result straight away, it looks like this:


Figure 1 Blue curve: Global temperature reconstruction from proxy data of Marcott et al, Science 2013. Shown here is the RegEM version – significant differences between the variants with different averaging methods arise only towards the end, where the number of proxy series decreases. This does not matter since the recent temperature evolution is well known from instrumental measurements, shown in red (global temperature from the instrumental HadCRU data). Graph: Klaus Bitterman.

The climate curve looks like a “hump”. At the beginning of the Holocene – after the end of the last Ice Age – global temperature increased, and subsequently it decreased again by 0.7 ° C over the past 5000 years. The well-known transition from the relatively warm Medieval into the “little ice age” turns out to be part of a much longer-term cooling, which ended abruptly with the rapid warming of the 20th Century. Within a hundred years, the cooling of the previous 5000 years was undone. (One result of this is, for example, that the famous iceman ‘Ötzi’, who disappeared under ice 5000 years ago, reappeared in 1991.)

The shape of the curve is probably not surprising to climate scientists as it fits with the forcing due to orbital cycles. Marcott et al. illustrate the orbital forcing with this graphic:


Figure 2 Changes in incoming solar radiation as a function of latitude in December, January and annual average, due to the astronomical Milankovitch cycles (known as orbital forcing). Source: Marcott et al., 2013.

In the bottom panel we see the sunlight averaged over the year, as it depends on time and latitude. It declined strongly in the mid to high latitudes over the Holocene, but increased slightly in the tropics. In the Marcott reconstruction the global temperature curve is dominated primarily by the large temperature changes in northern latitudes (30-90 °N). For this, the middle panel is particularly relevant: the summer maximum of the incoming radiation. That reduces massively during the Holocene – by more than 30 watts per square meter. (For comparison: the anthropogenic carbon dioxide in the atmosphere produces a radiative forcing of about 2 watts per square meter – albeit globally and throughout the year.) The climate system is particularly sensitive to this summer insolation, because it is amplified by the snow- and ice-albedo feedback. That is why in the Milanković theory summer insolation is the determining factor for the ice age cycles – the strong radiation maximum at the beginning of the Holocene is the reason why the ice masses of the last Ice Age disappeared.

However a puzzle remains: climate models don’t seem to get this cooling trend over the last 5,000 years. Maybe they are underestimating the feedbacks that amplify the northern orbital forcing shown in Fig. 2. Or maybe the proxy data do not properly represent the annual mean temperature but have a summer bias – as Fig. 2 shows, it is in summer that the solar radiation has declined so strongly since the mid-Holocene. As Gavin has just explained very nicely: a model-data mismatch is an opportunity to learn something new, but it takes work to find out what it is.

Comparison with the PAGES 2k reconstruction

The data used by Marcott et al. are different from those of the PAGES 2k project (which used land data only) mainly in that they come to 80% from deep-sea sediments. Sediments reach further back in time (far further than just through the Holocene – but that’s another story). Unlike tree-ring data, which are mainly suitable for the last two thousand years and rarely reach further. However, the sediment data have poorer time resolution and do not extend right up to the present, because the surface of the sediment is disturbed when the sediment core is taken. The methods of temperature reconstruction are very different from those used with the land data. For example, in sediment data the concentration of oxygen isotopes or the ratio of magnesium to calcium in the calcite shells of microscopic plankton are used, both of which show a good correlation with the water temperature. Thus each sediment core can be individually calibrated to obtain a temperature time series for each location.

Overall, the new Marcott reconstruction is largely independent of, and nicely complementary to, the PAGES 2k reconstruction: ocean instead of land, completely different methodology. Therefore, a comparison between the two is interesting:

Figure 3 The last two thousand years from Figure 1, in comparison to the PAGES 2k reconstruction (green), which was recently described here in detail. Graph: Klaus Bitterman.

As we can see, both reconstruction methods give consistent results. That the evolution of the last one thousand years is virtually identical is, by the way, yet another confirmation of the “hockey stick” by Mann et al. 1999, which is practically identical as well (see graph in my PAGES article).

Is the modern warming unique?

Because of the above-mentioned limitations of sediment cores, the new reconstruction does not reach the present but only goes to 1940, and the number of data curves used already strongly declines before that. (Hence we see the uncertainty range getting wider towards the end and the reconstructions with different averaging methods diverge there – we here show the RegEM method because it deals best with the decreasing data coverage. For a detailed analysis see the article by statistician Grant Foster.) The warming of the 20th Century can only be seen partially – but this is not serious, because this warming is very well documented by weather stations anyway. There can be no doubt about the climatic warming during the 20th Century.

There is a degree of flexibility on how the proxy data (blue) should be joined with the thermometer data (red) – here I’ve done this so that for the period 1000 to 1940 AD the average temperature of the Marcott curve and the PAGES 2k reconstruction are equal. I think this is better than the choice of Marcott et al. (whose paper was published before PAGES 2k) – but this is not important. The relative positioning of the curves makes a difference for whether the temperatures are slightly higher at the end than ever before in the Holocene, or only (as Marcott et al write) higher than during 85% of the Holocene. Let us just say they are roughly as high as during the Holocene optimum: maybe slightly cooler, maybe slightly warmer. This is not critical.

The important point is that the rapid rise in the 20th Century is unique throughout the Holocene. Whether this really is true has been intensively discussed in the blogs after the publication of the Marcott paper. Because the proxy data have only a coarse time resolution – would they have shown it if there had been a similarly rapid warming earlier in the Holocene?

I think for three reasons it is extremely likely that there was not such a rapid warming before:

1. There are a number of high-resolution proxy data series over the Holocene, none of which suggest that there was a previous warming spike as strong as in the 20th Century. Had there been such a global warming before, it would very likely have registered clearly in some of these data series, even if it didn’t show up in the averaged Marcott curve.

2. Grant Foster performed the test and hid some “20th C style” heating spikes in earlier parts of the proxy data to see whether they are revealed by the method of Marcott et al – the answer is a resounding yes, they would show up (albeit attenuated) in the averaged curve, see his article if you are interested in the details. [Update 18 Sept: one of our readers has confirmed this conclusion with a different method (Fourier filtering). Thanks!]

3. Such heating must have a physical basis, and it would have to have quickly disappeared again (would it have lasted, it would be even more evident in the proxy data). There is no evidence in the forcing data that such a climate forcing could have suddenly appeared and disappeared, and I cannot imagine what could have been the mechanism. (A CO2-induced warming would persist until the CO2 concentration decays again over thousands of years – and of course we have good data on the concentration of CO2 and other greenhouse gases for the whole Holocene.)

Conclusion

The curve (or better curves) of Marcott et al. will not be the last word on the global temperature history during the Holocene; like Mann et al. in 1998 it is the opening of the scientific discussion. There will certainly be alternative proposals, and here and there some corrections and improvements. However, I believe that (as was the case with Mann et al. for the last millennium) the basic shape will turn out to be robust: a relatively smooth curve with slow cooling trend lasting millennia from the Holocene optimum to the “little ice age”, mainly driven by the orbital cycles. At the end this cooling trend is abruptly reversed by the modern anthropogenic warming.

The following graph shows the Marcott reconstruction complemented by some context: the warming at the end of the last Ice Age (which 20,000 years ago reached its peak) and a medium projection for the expected warming in the 21st Century if humanity does not quickly reduce greenhouse gas emissions.


Figure 4 Global temperature variation since the last ice age 20,000 years ago, extended until 2100 for a medium emissions scenario with about 3 degrees of global warming. Graph: Jos Hagelaars.

Marcott et al. dryly state about this future prospect:

By 2100, global average temperatures will probably be 5 to 12 standard deviations above the Holocene temperature mean.

In other words: We are catapulting ourselves way out of the Holocene.

Just looking at the known drivers (climate forcings) and the actual temperature history shows it directly, without need for a climate model: without the increase in greenhouse gases caused by humans, the slow cooling trend would have continued. Thus virtually the entire warming of the 20th Century is due to man. This May, for the first time in at least a million years, the concentration of carbon dioxide in our atmosphere has exceeded the threshold of 400 ppm. If we do not stop this trend very soon, we will not recognize our Earth by the end of this century.

Links and comments: see original