What the Hockey Stick missed about climate change

(link updated March 2023)

You may have already heard of the 1999 hockey stick created by Michael Mann, Malcolm Hughes, and Raymond Bradley. It's a frequent skeptic talking point, and was involved in a whole scandal called climategate that rocked the scientific world. Eventually however it was validated by dozens of independent studies, and its conclusions accepted - the world is currently undergoing warming the likes of which humans have never seen before. Last month however, the hockey stick got an amazing upgrade. A new paper by Osman et al reconstructed the past 24,000 years of climate using new techniques, and gave us new insights into just how unprecedented anthropogenic global warming really is.

NOTES/REFERENCES
(2) This is a simplification - tree rings can sometimes act as a proxy for temperature or for precipitation, depending on the typical climate at a location
(5) I'm slightly oversimplifying here, what the paper did was attribute mechanisms to the principal components (PCs) of the temperature timeseries. PCs allow a signal to be broken down into components, ranked by size, that, when combined, reconstruct the signal. Solar and orbital forcing appears to be responsible for PC2, which was itself responsible for 3.5% of the total signal. The vast majority (over 90%) of the warming was accounted for by PC1, which could be explained almost entirely by greenhouse gases and changes in albedo.

---------- II ----------

---------- II ----------

This video is about the hockey stick graph created by Michael Mann and his collaborators in the MHB99 paper reconstructing the earth's past climate. I talk about how Mann missed key information in his analysis due to limitations of data at the time, and how instead of an eigenvector approach, a new study using Bayesian reconstruction paints a different picture of the Earth's past. The planet has never been as warm as it currently is during the holocene, with the medieval warm period and the little ice age barely featuring in the timeseries of past climate. This new nature paper from Osman et al is really something, amazing new climate change science that highlights present global warming.

Huge thanks to my supporters on Patreon: Andrew Knop, Shab Kumar, Cameron Grey, Brady Johnston, Liat Khitman, Jesper Norsted, Kent & Krista Halloran, Rapssack, abruptbanana, Kevin O'Connor, Timo Kerremans, Thines Ganeshamoorthy, Jerry Moore, Sam Harvey (the ever lasting student), Ashley Wilkins, Michael Parmenter, Samuel Baumgartner, Dan Sherman, ST0RMW1NG 1, Adrian Sand, Morten Engsvang, Josh Schiager, Farsight101, K.L, poundedjam, Daan Sneep, Felix Freiberger, Chris Field, Robert Connell, Jaime Stark, Kolbrandr, , Sebastain Graf, Dan Nelson, Shane O'Brien, Alex, Fujia Li, Harry Eakins, Will Tolley, Cody VanZandt, Jesper Koed, Jonathan Craske, Albrecht Striffler, Igor Francetic, Jack Troup, SexyCaveman , James Munro, Oskar Hellström, Sean Richards, Kedar , Alastair Fortune, bitreign33 , Mat Allen, Anne Smith, Rafaela Corrêa Pereira, Colin J. Brown, Princess Andromeda, Leighton Mackenzie, BenDent, Thusto , Andy Hartley, Lachlan Woods, Tim Boxall, Dan Hanvey, Simon Donkers, Kodzo , James Bridges, Liam , Andrea De Mezzo, Wendover Productions, Kendra Johnson.

[PhysicsOH]

Simon: "This graph is wrong"

Me: "Please be good news. Please be good news. Please be good news. DAMN IT!"

[jacobblackshaw]

Climate gate video would be great, I find the history of science controversies (and reactions to research at the time) fascinating

[SpiralDiving]

Reanalysis is still flawed if the input proxies are not good. There is still no good explanation as to why the medieval warm period was local when it may have stretched half way across the northern hemisphere. So why does the reanalysis not explain how barley was grown in Greenland? In any case, why do we think that a bit of warming is a bad thing and that the current condition is optimum?

[johnnygeneric]

In a fairly publicized lawsuit, Michael Mann REFUSED to hand over the data for the hockey stick chart to prove his side. Mann lost the lawsuit. You should hold anything he trots out with a high degree of suspicion.

[Camerondes]

The use of tree rings as a proxy for temperature is problematic because tree ring widths are more influenced by the regularity of rainfall not temperature.

[AhmetKaan]

*“You can’t go back and change the beginning, but you can start where you are and change the ending...”*
*―C. S. Lewis*

[michaelwillis]

Are they farming in Greenland again as they were in the Medieval Warm Period? No? Perhaps then that old graph was more correct than now claimed. Proxy measurements are nothing but a best guess and when one's best guess is guided by whether your grant money gets cut off or not those guesses can be cherry picked.

[jamesfairmind]

Three things we do know about the MWP is that there were three crop rotations a year, vineyards thrived from Scotland to Cornwall, and the skeletons of the period indicate that even the very poorest people were eating exceptionally well in contrast to evidence from skeletons before and after that period. Historical records also state the poor were able to live comfortably outside in rough shelters and evidence of ancient houses that still stand today show us clues that it was a very warm period indeed. Well I not sure about the rest of the world, but certainly in Northern Europe the temperature was certainly significantly higher in the MWP than today for those factors to occur. Try growing vineyards in Scotland today or achieving three crop rotations per year and see how far you get.

[czerwonadupa]

As soon as he said they used "scientific modelling" I shook my head.
The academic Prof Ferguson who created the infamous Imperial College model that warned Boris Johnson that, without an immediate lockdown, the coronavirus would cause 500, 000 deaths and swamp the National Health Service - Never happened.
Ferguson was behind the disputed model that sparked the mass culling of eleven million sheep and cattle during the 2001 outbreak of foot-and-mouth disease and predicted 150, 00 deaths from mad cow disease by 2080 - Never happened only 177 people have died.
In 2005, Ferguson's model predicted that up to 150 million people could be killed from bird flu. In the end, only 282 people died worldwide from the disease between 2003 and 2009.

In 2009, a government estimate, based on Ferguson’s advice, said a “reasonable worst-case scenario” was that the swine flu would lead to 65, 000 British deaths. In the end, swine flu killed 457 people in the U.K.

Many of these scientists would be better off playing with model trains than "modelling" predictions that vastly over estimate what they want to predict

[replevideo]

I don't get your point. Your final] graph shows warming of about 1.2°C over the last 150 years, which is not in dispute. However your claim about the Medieval Warm Period is very much in dispute. Signs of it have been found in the southern hemisphere even Antarctica, where it appears to have been less marked than in the northern hemisphere but still present. There are also many other studies which have found good reason to question how much greenhouse gases have contributed to temperature rise. The GMT during the Holocene optimum is also in question and may have been between 2 and 3°C warmer than today, which if true means today's GMT is not unprecedented. It all amounts to which proxies you want to trust and which to discard. Remember, science is never settled, and if you claim it is, that is not science.

[flingmonkey]

I would like to request clarification on one point in this climate change discussion. I have heard (please correct me if I am wrong) that of all CO2 emitted into the atmosphere each year, 95% of it is from natural causes. If that is so, and only 5% of CO2 emissions is from ALL human activity, and America's contribution is only a piece of that, how is forcing everyone to drive electric cars going to change these numbers, especially in view of the facts that China is frantically building more coal-powered electrical generation and all electric vehicles are, essentially, coal powered anyway?

[Spazmonkeyorange]

Anyone else find it interesting that almost all the SST proxy data points were coastal? Seems like that would make a big difference.

[dbadaddy]

What made it a conspiracy is their active refusal to provide access to their data, and when they did provide data, it was clear they had intentionally altered the datasets. Yes, "cleaning" data is a thing and can be valid, because some data can be in error or is spoiled in various ways, but they actively opposed investigating this. Yes, you also release the bad data and explain why it is bad, you don't hide it and lie about it. Their unscientific behavior rightfully led to questioning the validity of the graph. Note that nothing I said discussed the validity of the graph itself, just the bad behavior of Mann and Company was a strong driver of the controversy. Good scientists don't refuse to release full datasets.

[brentkn]

Despite being predominantly recorded in Europe, south-western North America and in some tropical regions, the Medieval warm period affected both the northern and southern hemispheres. But the temperature increase was not universal, varying across regions of the world, and did not happen simultaneously everywhere.

[TechAltar]

Oh hi, nice Nebula original pick 😁
Also, great video as always

[solarcrystal]

The problem with the hockey stick graph is that it stops using the tree ring data at about a century ago because the hockey stick doesn't show up in it.

[davidtonkin]

It’s curious that Michael Mann is so reluctant to defend his hockey stick in court. He started the cases but has refused to complete them.

[TheTmshuman]

Real climate science is a great channel that goes into old news paper archives to show all the omitted data that was too inconvenient to include in the ever changing main stream graphs.

[PeloquinDavid]

Strange example... Mangoes ripen and they ALL fall to the ground whether eaten by monkeys or not. Moreover, if there were variations, that would be a better proxy for how many mangos are harvested by humans and taken home to be eaten or sold. (Monkeys seldom export mangoes outside their home range.)

[old_toucs]

The Hockey stick graph shows two different kinds of data. There are modern thermometer readings with high accuracy, regular and frequent records and good geographical coverage. Then there are proxies which are the opposite. The proxy data is easy to find via PAGES12K (the metadata spreadsheet) and graphing up any dozen of the 1300 proxies will show huge variability even for the same places using similar methods. The graph you are shown is just lots of estimates added together. The likely +/- indicates a warm era like ours would be expected every few centuries.

The IPCC best estimate for human warming is currently 1.07C. However the first 0.5C is just a return to normal after the Little Ice Age. So we are all supposed to panic over 0.6C above normal after 150 years.

The obvious conclusion is that we are having a small effect on something that isn't that big in the first place. It might be a problem if we don't change for a few centuries but there is no reason to assume any crisis is going to happen.