The climate is warming faster than it has in the last 2,000 years

The climate is warming faster than it has in the last 2,000 years
Global mean warming / cooling rates over the last 2,000 years. In red are the periods (each across 51 years) in which the reconstructed temperatures increased. Global temperatures decreased in the periods in blue. The green line shows that the maximum expected warming rate without anthropogenic influence is just under 0.6 degrees per century. Climate models (dashed orange line) are able to simulate this natural upper limit very well. At more than 1.7 degrees per century, the current rate of warming is significantly higher than the expected natural rate of warming, and higher than values for every previous century. Instrumental measurements since 1850 (in black) confirm these figures. Credit: University of Bern

Many people have a clear picture of the "Little Ice Age" (from approx. 1300 to 1850). It's characterized by paintings showing people skating on Dutch canals and glaciers advancing far into the alpine valleys. That it was extraordinarily cool in Europe for several centuries is proven by a large number of temperature reconstructions using tree rings, for example, not just by historical paintings. As there are also similar reconstructions for North America, it was assumed that the "Little Ice Age" and the similarly famous "Medieval Warm Period" (approx. 700—1400) were global phenomena. But now an international group led by Raphael Neukom of the Oeschger Center for Climate Change Research at the University of Bern is painting a very different picture of these alleged global climate fluctuations. In a study which has just appeared in the well-known scientific journal Nature, and in a supplementary publication in Nature Geoscience, the team shows that there is no evidence that there were uniform warm and cold periods across the globe over the last 2,000 years.

Climate fluctuations in the past varied from region to region

"It's true that during the Little Ice Age it was generally colder across the whole world," explains Raphael Neukom, "but not everywhere at the same time. The peak periods of pre-industrial warm and cold periods occurred at different times in different places." According to the climate scientist from Bern, the now-debunked hypothesis of climate phases occurring at the same time across the globe came about because of an impression that is defined by the climate history of Europe and North America. In the absence of data from other parts of the earth, this notion was applied to the whole planet, raising expectations that relatively cold or warm periods throughout the last 2,000 years were globally synchronous phenomena. But it has now been shown that this was not the case.

The authors of the study in Nature see the explanation for that as being that regional climates in pre-industrial times were primarily influenced by random fluctuations within the climate systems themselves. External factors such as volcanic eruptions or solar activity were not intense enough to cause markedly warm or cold temperatures across the whole world for decades, or even centuries.

The researchers relied on a database from the international research consortium PAGES (Past Global Changes, http://www.pastglobalchanges.org), which provides a comprehensive overview of climate data from the last 2,000 years, for their investigation of five pre-industrial climate epochs. In addition to tree rings, it also includes data from ice cores, lake sediments and corals. To really put the results to the test, the team led by Raphael Neukom analyzed these data sets using six different statistical models—more than ever before. This allowed for the calculation of the probability of extremely warm or cold decades and centuries, and not just the calculation of absolute temperatures. The result was that no globally coherent picture emerged during the periods being investigated. "The minimum and maximum temperatures were different in different areas," says Raphael Neukom. So thermal extremes across the world cannot be inferred from regional temperature phenomena like the oft-mentioned "Medieval Warm Period" in Europe and North America.

The current warm period is happening across the world for the first time

The results look very different for recent history. Both studies show that the warmest period of the last 2,000 years was most likely in the 20th century. They also show that this was the case for more than 98 percent of the surface of the earth. This shows—once again—that modern climate change cannot be explained by random fluctuations, but by anthropogenic emissions of CO2 and other greenhouse gases. What we didn't know until now is that not only average global temperatures in the 20th century are higher than ever before in at least 2,000 years, but also that a warming period is now affecting the whole planet at the same time for the first time. And the speed of global warming has never been as high as it is today.


Explore further

More sensitive climates are more variable climates, research shows

More information: No evidence for globally coherent warm and cold periods over the preindustrial Common Era, DOI: Nature Geoscience (2019). 10.1038/s41586-019-1401-2 DOI: 10.1038/s41586-019-1401-2
Journal information: Nature Geoscience , Nature

Provided by University of Bern
Citation: The climate is warming faster than it has in the last 2,000 years (2019, July 24) retrieved 24 August 2019 from https://phys.org/news/2019-07-20th-century-unmatched-years.html
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Jul 24, 2019
The climate is warming faster than it has in the last 2,000 years


Waiting patently for vineyards in Scotland. Grape clusters need >100 days of 27C+ and sun to ripen correctly. Wine was produced in Scotland during the Roman Climate Optimum and the Medieval Climate Optimum.

Jul 24, 2019
The climate is warming faster than it has in the last 2,000 years


Waiting patently for vineyards in Scotland. Grape clusters need >100 days of 27C+ and sun to ripen correctly. Wine was produced in Scotland during the Roman Climate Optimum and the Medieval Climate Optimum.


These warm periods are named Climate Optimums for a reason, you know?

Jul 24, 2019
Hay @shootit, I'm waiting for all the elephants and kangaroos to start appearing in Greenland. Isn't that needed for your conspiracy to workout? Grapes in Scottland? A solar-powered greenhouse would do the trick. What, you don't have a conspiracy yet? You can now buy a 'Conspiracy Theory' on DVD, or rent it from your favorite outlet. Also just a comment to the editor of this article the graph that you show doesn't fit the screen.

Jul 24, 2019
So now we have confirmation that the LIA and Medieval Warm Period were mild fluctuations and this warming is something taking us way beyond them - which we knew already.

Phys.org articles on studies that throw doubt on that simply aren't getting published because they either don't exist or are advocacy dressed up as science - which is exactly as it should be; multiple independent lines of inquiry are circling ever closer around the true state of our disturbed climate system. The gullible who swallowed the climate responsibility denier's conspiracy hook - line and sinker - are left dangling, gasping their same pointless objections in the guise of anonymous pseudo-expertise in comments below the continuing confirmations of the very science they choose not to accept.

Jul 24, 2019
So basically, as hard as they tried, the "Medievil warming period" old @shootlisp always brags of is nothing but total crap; which I'm sure he knows. He just posts here as a favor to Fox news Back to you @Ken.

Jul 24, 2019
It's obscene, for what idiots the AGW Cult takes their flock.
Gobble up Chicken Shites.

Jul 24, 2019
@algoreacle just loves to type words he knows, like 'AGW' and 'gobble'. Everything in between is just a meaningless photonic spray onto sensitive photochemically active nerve cells. But I digress.

I think it's interesting bozos post their stupidity to the public with comments like @algoreacle thing.

That said; it's also fascinating from a geekishly science point of view to see this quote from the article;

no globally coherent picture emerged during the periods being investigated. "The minimum and maximum temperatures were different in different areas," says Raphael Neukom. So thermal extremes across the world cannot be inferred from regional temperature phenomena like the oft-mentioned "Medieval Warm Period" in Europe and North America."


So old @shootit was simply just a bozo making noise about climate when he had no facts to base them on. Pony up a bottle of that awesome very old Scottish wine. We all want to see it.


Jul 25, 2019
Waiting patently for vineyards in Scotland. Grape clusters need >100 days of 27C+ and sun to ripen correctly. Wine was produced in Scotland during the Roman Climate Optimum and the Medieval Climate Optimum.

I think that the penguins in the Sahara during the Roman and Medieval Climate Optimums proves that they were only local events. There's just as much evidence for Sahara penguins as there is for Scottish vineyards, and according to Shootist they are far more real than the mythical Champagne that comes from a region that doesn't get >100 days of 27C+

https://en.climat...te-graph

Jul 25, 2019
That graph is even more clear cut than the hockey stick; another good couple of papers. (Excellent actually, is what I read, modern statistics combined with a tour de force in comparing historical data series!) But xqcd paraphrased the science even better: https://xkcd.com/1732/ .

asping their same pointless objections in the guise of anonymous pseudo-expertise in comments below the continuing confirmations of the very science they choose not to accept.


Well, blocked in my case. Wonder why that is, but there were no new senseless trolls in this bunch. Maybe they are running out of their "cool"? :-D

Jul 26, 2019
The climate is warming faster than it has in the last 2,000 years


Waiting patently for vineyards in Scotland. Grape clusters need >100 days of 27C+ and sun to ripen correctly. Wine was produced in Scotland during the Roman Climate Optimum and the Medieval Climate Optimum.

I see you've shifted your target further north now. Did you know there is a commercial vineyard in Yorkshire? Not quite Scotland, but close.

Jul 29, 2019
Grapes and tea are grown in England now again

Jul 30, 2019
Nice going combine "climate" and "warming" in headline: "The climate is warming faster than it has in the last 2,000 years." and you don't have to chose between "global warming" and "climate changing"! Should make it easier for Gore, the inventor of the internet (or so he says), and what's his name, you know the new spokesperson, who used to be a clown in a kid's show, while using the term "science" to give himself credibility. I'll pass out due to the heat... Wait, didn't I have to close my windows at 3:00 AM because it was so "hot" (NOT) here in Minnesota, two months before the end of the three months of summer. What ever!

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