A science presenter, writer, speaker & former TV host; author of The Skeptic's Handbook (over 200,000 copies distributed & available in 15 languages).



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Denying 2000 years of the Medieval Warm Period, Little Ice Age on every continent

Here we go again. For five or so years believers didn’t really mention the Medieval Warm Period. Too bruised by the embarrassment of Hockey Stick Zombie failures. But it’s an inconvenient era they have to rub out because none of the expert models can explain what caused it, and it’s hard to panic about same temperatures that Edward the Confessor survived with oxen and carts.

And it’s hard to call the modern warmth “man-made” if nature created something just like it 1,000 years ago.

Climate change: We haven’t experienced anything like this in the past 2,000 years

By Michael Collett, ABC, Environmental Copy and Paste Promoter

Climate scientists writing in the journal Nature have found there is no evidence for “globally coherent warm and cold periods” over the past 2,000 years prior to industrialisation.

That’s significant, because climate change deniers have sometimes pointed to epochs like the so-called “Little Ice Age” or “Medieval Warm Period” to argue that the current global warming is one among multiple similar global climate events.

But what the research actually shows is that other “peak warming and cooling events” over the past two millennia appear to have […]

Antarctica was warmer one thousand years ago — and life was OK

Remember when polar amplification was the rage? So much for that theory

Antarctica is twice the size of the US or Australia. Buried 2 km deep under domes of snow, it holds 58 meters of global sea level to ransom. The IPCC have been predicting its demise-by-climate-change for a decade or two.

A new paper looks at 60 sites across Antarctica, considering everything from ice, lake and marine cores to peat and seal skins. They were particularly interested in the Medieval Warm Period, and researched back to 600AD. During medieval times (1000-1200 AD) they estimate Antarctica as a whole was hotter than it is today. Antarctica was even warmer still — during the dark ages circa 700AD.

Credit to the paper authors: Sebastian Lüning, Mariusz Gałka, and Fritz Vahrenholt

Feast your eyes on the decidedly not unprecedented modern tiny spike:


The little jaggy down after 2000 AD is real. While there was rapid warming across Antarctica from 1950-2000, in the last twenty years, that warming has stalled. Just another 14 million square kilometers that the models didn’t predict.

We already knew the Medieval Warm Period was a global phenomenon, thanks to hundreds of proxies, and 6,000 boreholes. But […]

Scottish summers not doing anything they haven’t done for 800 years already

Gotta love a long unbroken proxy.

Scientists looked at 44 pines sites across the Scottish Highlands and used their tree rings to create a continuous temperature series for the last 810 years. Showing admirable restraint, they did not paste on adjusted thermometer records to create a hockey stick effect. Instead we can see that Scottish summers were just as warm in the 1300s, the 1280s and around 1500 as well.

The rate of warming is not unprecedented. The temperature is not unusual. But thermometers don’t tell the same story as the tree rings in the last 50 years. They both can’t be right. Either the tree rings are always unreliable thermometers or the thermometers are placed near ice cream trucks and adjusted up-the-kazoo?

Thanks to CO2Science:

Rydval et al. extended “the previously published Scottish dendroclimatic record (Hughes et al., 1984) by nearly 500 years,” in order to create an 810-year-long proxy over the period AD 1200-2010. The reconstruction was derived from a network of 44 Scots pine (Pinus Sylvestris) sites across the Scottish Highlands from both living and subfossil samples that correlated well with summer (July-August) temperatures.

In placing the most recent warming of the instrumental […]

Chinese scientists find 2,000 years of not-hockey stick

There was no Medieval Warm Period in China. No little ice age either. Not warm in Roman times either.

Obviously CO2 controls this climate.

(Click to enlarge)

Quansheng et al show that weather is lumpy, that modern warming is a lot like past warming. They go so far as to say that there are regular cycles and hint that sun might have something to do with it, and volcanoes.

“…centenial variation is significantly correlated with long-term changes in solar radiation—especially cold periods, which correspond approximately to sunspot minima, as well as the frequency of large volcanic eruptions.”

They go on to say that rate of warming was about half a degree per century lately. It may have been the fastest rate, but then again, it may not. It was hard to tell with the error bars being so wide. It was all done with proxies and has a ten year resolution. Obviously it is in need of having homogenadjustoided thermometer data added after 1960 as is the custom in climate science.

The Medieval Warm Period was global Medieval Warm Period found in 120 proxies. Plus Roman era was similar to early 20th Century. Sun controls half of […]

How to make climate graphs look scary — a reply to XKCD

This week XKCD (a popular Geek comic site) posted an epic cartoon called “A Timeline Of Earth’s Average Temperature”. It was a cutesy long godzilla hockey-stick — “scary” to the unwary.

It’s easy to make a scary historical-looking temperature graph — so easy that the artist probably didn’t even know how. (Thank Shakun, Marcott, Annan, Hadcrut and the IPCC for doing the tricky part.) First, guesstimate temperatures over last 20,000 years with anything at hand: tree-rings, ice bubbles, coral, fossilized tea leaves, whatever. Blend. Then stop the proxies, tack on thermometer data that was recorded in a different way with different errors and a very different response to faster temperature changes. Finally, launch that line into the future with unvalidated, skillless multivariate models that predict a fingerprint which 28 million weather balloons can’t find. Then take the models that didn’t work for the last twenty years, and run with the errors to the next century… Voila!

I took the 14,000 pixel cartoon and squeezed it to one shot that shows the curve that matters. See the error bars? Me neither.

(But who needs an uncertainty range when you have faith?)

Click to enlarge.

The secret to a good hockey-stick […]

Sun controls half of the groundwater recharge rate in China for last 700 years

Could this be why climate models do rainfall with all the competence of tea-leaf-reading? Tiwari et al report that as much as 47% of the recharge rates of ground water in China are controlled by the sun. Apparently climate models miss the minor factor of the major cycles.

Try this radical idea on: imagine a world where climate models worked. Not only could the BoM warn people that there would be a drought coming, they could name the region, and the years.

Tiwari et al:

Here for the purpose of comparison of long term ground water recharge rates with long term solar activity, we used the 10-year average sunspot time series, for the period 1300 to 1905 AD, published by Solanki et al., [2004]. Also the additional average annual sunspot number time series (1700 to 2000 AD) is used from data source Solar Influences Data Analysis Centre. In addition to decadal data annual sunspot number data from 1700 to 2000 AD downloaded from Solar Influences Data Analysis Centre is used in the present study. The cross-correlation coefficient (+0.63) between the groundwater recharge rate time series and decadal sunspot number [Solanki et al., 2004] shows that there is statistically significant solar […]

The North Atlantic jet stream correlates with Solar output over a millennium

A new paper (Moffa-Sánchez et al) reports that they looked at layers of dead plankton in ocean mud (otherwise known as foraminifera in marine sediments) and have reconstructed the temperature and salinity of a couple of spots in the North Atlantic between 818AD – 1780 with data on δ18O and the Mg/Ca ratios. One immediate thought, an aside, is that if this technique works, there is no shortage of ocean mud, surely, and perhaps we could drill and analyze more mud for solar correlations in other places. (I hear foraminifera live in the Southern Hemisphere too). Perhaps no one is looking for the connection with the sun?

Moffa-Sánchez et al find the big climate shifts (the 100-year variations) correlate with total solar irradiance (TSI). See especially that orange line black line track in the d graph below. I stress, correlations don’t mean causation and the mechanism is mere speculation. But I find the graph intruiging. There are a lot of turning points, and in pure “curve fitting” type of analysis, this is a better curve fit than the one with CO2. (Find me a turning point that matches with carbon dioxide!) I suspect we’ll be referring back to this paper, […]

Ocean heat content around Indonesia shows Medieval Warm Period and 2C warmth in holocene

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 […]

The message from boreholes

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 […]

Medieval Warm Period found in 120 proxies. Plus Roman era was similar to early 20th Century.

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 […]