Rosenthal et al have put out quite a humdinger of a paper. They’ve reconstructed the temperature of the water flowing out of the Pacific to the Indian Ocean over the last 10,000 years and as deep as 900m. The Indonesian Throughflow is pretty significant in global ocean currents. There’s narrow routes for Pacific upper waters to squeeze through to the Indian Ocean through the Makassar and Lombok Straits, and via the Lifamatola Passage through the Banda Sea, and water comes in from both the North and South Pacific.
An important point in global ocean currents where the Pacific flows through to the Indian Ocean.
Points to note (assuming the study is right):
Temperatures started rising around 1700AD – long before our carbon emissions. That temperatures were much warmer (0.65C) in 1100AD than they were in 1950. 8,000 years ago water was 1.5 to 2 degrees warmer — isn’t that meant to be a global catastrophe? Apparently coral reefs, fish, and turtles survived.
Figure 4. Holocene changes in Pacific Ocean heat content. (A) Reconstructed anomalies in Pacific OHC in the 0- to 700-m depth interval for the early Holocene, mid-Holocene, MWP, and LIA periods. Reconstructed anomalies are calculated relative [...]
There have been suggestions that Jo Nova might be trying to hide or ignore the most recent boreholes graph from Huang et al. So here it is. This is the last 2,000 years according to 6000 boreholes, with the last 100 years also using the “instrumental record” which gives us that hockey-stick uptick at the end. Below I explain the pros and cons of this study and update my thoughts.
Huang and Pollack 2008: Their latest boreholes published study
A borehole sounds like a bit-of-a-stretch as a proxy. How could we tell if the world was warmer in 1066 by drilling a hole in the ground? Yes, fair point. But what makes boreholes useful is that they are global and there is a lot of data: specifically 6,000 holes all over the world.
I’ve been looking at boreholes in more detail, analyzing them in the light of newer proxies. When all the evidence is considered, boreholes turn out be not-much-use at giving us meaningful numbers in degrees C, and in my opinion, not-too-hot at telling us the “when” of an event either. Too much depends on assumptions.
But what are they good for is that, when combined with [...]
Two major proxy studies, larger than ever, were released in April and June 2012. They show that the Medieval Warm Period (MWP) existed, and was similar to current temperatures. These comprehensive studies suggest current temperatures are not unusual, and that itself is not all that surprising — I’ve mentioned before how there are hundreds of proxy studies showing it was as warm or warmer back then. (CO2science has been documenting them.) But these studies are worth a mention because they are so large.
Climate models cannot explain what caused the warming 1000 years ago, nor the cooling 300 years ago, so they can’t rule out the same factors aren’t changing the climate today (though they claim they can). If climate models can’t explain the past, they can’t predict the future.
The last 12 Centuries
Ljungqvist used 120 proxy records — nearly 3 times as many proxies as previous studies and conclude: “during the 9th to 11th centuries there was widespread NH warmth comparable in both geographic extent and level to that of the 20th century”. Their proxies included ice-cores, pollen, marine sediments, lake sediments, tree-rings, speleothems and historical documentary data.
Ljungqvistet al 2012 Fig. 4. Mean time-series of centennial [...]
A blockbuster Chinese study of Tibetan tree rings by Liu et al 2011 shows, with detail, that the modern era is a dog-standard normal climate when compared to the last 2,500 years. The temperature, the rate of change — it’s all been seen before. Nothing about the current period is “abnormal”, indeed the current warming period in Tibet can be produced through calculation of cycles. Liu et al do a Fourier analysis on the underlying cycles and do brave predictions as well.
In Tibet, it was about the same temperature on at least four occasions — back in late Roman times (those chariots!), then again in the dark ages (blame the collapse of industry), then in the middle ages (the Vikings?), then in modern times (blame the rise of industry).
Clearly, these climate cycles have nothing to with human civilization. Their team finds natural cycles of many different lengths are at work: 2-3 years, 100 years, 199 years, 800 years, and 1,324 years. The cold periods are associated with sunspot cycles. What we are not used to seeing are brave scientists willing to publish exact predictions of future temperatures for 100 years that include rises and falls. Apparently, it will [...]
Qassiarsuk: This is the site of the Viking settlement of 972 and unlike much of Greenland, offers relatively sheltered grazing land for sheep. Photo: John McLean. (Click to see more images of Greenland).
For the first time temperatures over the last 5,600 years have been reassembled from the inhabited area of Greenland. (Other estimates were from ice-cores that are far inland.)
William D’Andrea, the paper’s first author says: “.. we can say there is a definite cooling trend in the region right before the Norse disappear.”
What do you know? The Medieval Warm Period, which either “didn’t exist” or “only happened in Europe”, also hit Western Antarctica.
Booth Island and Mount Scott are also on the Antarctic Peninsula. Photo: Stan Shebs.
The climate models don’t know why the world was warmer 1000 years ago. They don’t know why it cooled into the Little Ice Age either. The models don’t do regional projections well, and they don’t do seasonal projections with any skill, and they (in the last ten years) don’t work on short decadal timeframes either, but surely when it comes to big global temperature changes the models have got all the major forces figured out? Surely they’d be able to predict large movements across the entire globe eh? — but the first test we come to, a mere thousand years ago, shows the models have a predictive ability not significantly different from a coin toss.
Just because it was warmer 1000 years ago (due to some other reason), doesn’t mean that CO2 isn’t responsible for this warming cycle, but when all the evidence for CO2′s guilt comes only from models that can’t get the last warming cycle right, and from argument from ignorance (“Our [...]
The public might not understand the science, but they do understand cheating
Dr. David Evans
6 October 2010
[A series of articles reviewing the western climate establishment and the media. The first and second discussed air temperatures, the third discussed ocean temperatures.]
Click to download a pdf file containing the whole series
They Don’t Tell You: The Current Global Warming Trend is Over 300 Years Old
A Scene on the Ice by Hendrick Avercamp, circa 1600
Satellite data only goes back to 1979, and global land-thermometer records only go back to 1850. Before that we have to resort to “proxies”, which are various natural phenomena from which temperature can be deduced. As we go further back in time, the errors and uncertainties increase.
A sample of recent scientific news from NIPCC * The Glaciers of Greenland were smaller 5000 years ago; * African savanna trees thrive with increases in CO2; * It was hotter in China a thousand years ago, and by a whole degree; * Marine-life-with-shells can’t agree on their favourite CO2 level and * Temperatures make no difference to the 5000 year record of hurricanes. [...]
A joint post with Baa Humbug
It’s all about audacity.
Michael Mann’s contribution to modern science may one day be remembered as the guy who made it statistically possible to get a thousand year temperature graph using any local telephone directory as a data source. (Who needs tree-rings?)
If you were a guy who’d been caught producing scientific work so inept that people could pour in random data and get the same “curve”, then you might take a satirical video on the chin (or crawl into a hole). But if you’re Michael Mann, and you also used the wrong proxy, you hid your data, used graphs upside down, and invented deceptive “tricks” to hide declines, then you might call your lawyers.
The Minnestoans for Global Warming (M4GW) made the hilariously popular Hide The Decline video, which has now been removed from YouTube. Mann claims they defamed him “by leaving viewers with the incorrect impression that he falsified data to generate desired results in connection with his research activities”. The Minnesotans said “please do”, and responded undaunted by producing a new version (see below).
Greenland Temperatures – last 10,000 years. Are we headed for an ice age? (See below for more detail.)
David Lappi is a geologist from Alaska who has sent in a set of beautiful graphs–including an especially prosaic one of the last 10,000 years in Greenland–that he put together himself (and which I’ve copied here at the top).
If you wonder where today’s temperature fits in with the grand scheme of time on Earth since the dinosaurs were wiped out, here’s the history. We start with the whole 65 million years, then zoom in, and zoom in again to the last 12,000 from both ends of the world. What’s obvious is that in terms of homo sapiens history, things are warm now (because we’re not in an ice age). But, in terms of homo sapiens civilization, things are cooler than usual, and appear to be cooling.
Then again, since T-rex & Co. vanished, it’s been one long slide down the thermometer, and our current “record heatwave” is far cooler than normal. The dinosaurs would have scoffed at us: “What? You think this is warm?”
With so much volatility in the graphs, anyone could play “pick a trend” and depending on [...]
Guest post by Dr David Evans PDF at sciencespeak.com
Now that ClimateGate has buried the fraudulent hockey stick for good, it is easy to prove that global warming is not man-made: just compare the timing of our carbon dioxide emissions with the timing of global warming.
Human Emissions of Carbon Dioxide
Emissions of carbon dioxide by humans are easy to estimate from our consumption of coal, oil, and natural gas, and production of cement:
Figure 1: Carbon emissions by humans. Source: Carbon Dioxide Information Analysis Center.
The vast bulk of human emissions occurred after 1945, during post-WWII industrialization. Half of all human consumption of fossil fuels and cement production has occurred since the mid 1970s.
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