At a glance - How does the Medieval Warm Period compare to current global temperatures?

On February 14, 2023 we announced our Rebuttal Update Project. This included an ask for feedback about the added "At a glance" section in the updated basic rebuttal versions. This weekly blog post series highlights this new section of one of the updated basic rebuttal versions and serves as a "bump" for our ask. This week features "How does the Medieval Warm Period compare to current global temperatures?". More will follow in the upcoming weeks. Please follow the Further Reading link at the bottom to read the full rebuttal and to join the discussion in the comment thread there.

Fact-Myth-Box

At a glance

To explore this topic, the first question must surely be: what was the Medieval Warm Period? The answer lies in the dim and distant past, in modern human terms, that is. Compared to the age of the Earth, at 4.5 billion years, it is a fraction of a very small fraction of a blink of the eye. Nevertheless, let's continue.

The period of time known to archaeologists as the Common Era (CE) roughly covers the past 2000 years. Decades ago it was divided into a series of climate epochs. Although there is no firm consensus regarding their precise duration, the 'Roman Warm Period' covered the first few centuries. The 'Dark Ages Cold Period' was from around 400-800 CE, the 'Medieval Warm Period' was from 800-1200 CE and the 'Little Ice-Age' was from 1200-1850 CE.

Each of these climatic epochs has its origin in old pieces of paleoclimatic evidence from the Northern Hemisphere. Decades ago, it was assumed each such epoch must have been global in extent. But since that time, climatology has steadily moved on. More new ways of reconstructing the Common Era climate have been discovered and refined. Coverage has been extended from those few Northern Hemisphere localities to the entire globe.

Thanks to such improvements, we now know that many of these warming and cooling events were regional, not global effects. The evidence no longer supports the idea of epochs of globally coherent and synchronous climate. Yes it was warm in Europe in the Medieval Warm Period. However, it was much cooler, for example, over the Pacific than it is today.

The coldest epoch of the last millennium is known as the Little Ice Age. But here too, the effects were not the same everywhere at the same time, as pointed out in a recent paper published in Nature. Its authors commented that peak cold occurred at widely-spaced locations hundreds of years apart. Coldest temperatures occurred during the fifteenth century in the central and eastern Pacific Ocean. But by the seventeenth century it was coldest in northwestern Europe and southeastern North America.

In contrast the same study found that the warmest period of the past two millennia occurred during the 20th century. The warmth affects more than 98% of the globe. That constitutes solid evidence that modern human-caused global warming is unusual. As the paper says, it is, "unparalleled in terms of absolute temperatures and also unprecedented in global coverage within the past 2,000 years".

Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!


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In case you'd like to explore more of our recently updated rebuttals, here are the links to all of them:

Myths with link to rebuttal Short URLs
Ice age predicted in the 1970s sks.to/1970s
It hasn't warmed since 1998 sks.to/1998
Antarctica is gaining ice sks.to/antarctica
CRU emails suggest conspiracy sks.to/climategate
What evidence is there for the hockey stick sks.to/hockey
CO2 lags temperature sks.to/lag
Climate's changed before sks.to/past
It's the sun sks.to/sun
Temperature records are unreliable sks.to/temp
The greenhouse effect and the 2nd law of thermodynamics sks.to/thermo
We're heading into an ice age sks.to/iceage
Positives and negatives of global warming sks.to/impacts
The 97% consensus on global warming sks.to/consensus
Global cooling - Is global warming still happening? sks.to/cooling
How reliable are climate models? sks.to/model
Can animals and plants adapt to global warming? sks.to/species
What's the link between cosmic rays and climate change? sks.to/cosmic
Is Al Gore's An Inconvenient Truth accurate? sks.to/gore
Are glaciers growing or retreating? sks.to/glacier
Ocean acidification: global warming's evil twin sks.to/acid
The human fingerprint in global warming sks.to/agw
Empirical evidence that humans are causing global warming sks.to/evidence
How do we know more CO2 is causing warming? sks.to/greenhouse
Explaining how the water vapor greenhouse effect works sks.to/vapor
The tricks employed by the flawed OISM Petition Project to cast doubt on the scientific consensus on climate change sks.to/OISM
Is extreme weather caused by global warming? sks.to/extreme
How substances in trace amounts can cause large effects sks.to/trace
How much is sea level rising? sks.to/sealevel
Is CO2 a pollutant? sks.to/pollutant
Does cold weather disprove global warming? sks.to/cold
Do volcanoes emit more CO2 than humans? sks.to/volcano
How do human CO2 emissions compare to natural CO2 emissions? sks.to/co2
Climate scientists could make more money in other careers sks.to/money
How reliable are CO2 measurements? sks.to/co2data
Do high levels of CO2 in the past contradict the warming effect of CO2? sks.to/pastco2
What is the net feedback of clouds? sks.to/cloud
Global warming vs climate change sks.to/name
Is Mars warming? sks.to/mars
How the IPCC is more likely to underestimate the climate response sks.to/underestimat
How sensitive is our climate? sks.to/sensitivity
Evidence for global warming sks.to/warming
Has the greenhouse effect been falsified? sks.to/falsify
Does breathing contribute to CO2 buildup in the atmosphere? sks.to/breath
What is causing the increase in atmospheric CO2? sks.to/CO2increase
What is methane's contribution to global warming? sks.to/methane
Plants cannot live on CO2 alone sks.to/plant
Is the CO2 effect saturated? sks.to/saturate
Greenhouse warming 100 times greater than waste heat sks.to/waste
How will global warming affect polar bears? sks.to/bear
The runaway greenhouse effect on Venus sks.to/venus
What climate change is happening to other planets in the solar system? sks.to/planets
Has Arctic sea ice returned to normal? sks.to/arctic
Was Greenland really green in the past? sks.to/green
Is Greenland gaining or losing ice? sks.to/greenland
Human activity is driving retreat of Arctic sea ice sks.to/arcticcycle
The albedo effect and global warming sks.to/albedo
Does CO2 always correlate with temperature? sks.to/correlate
Human fingerprints on climate change rule out natural cycles sks.to/cycle
Global warming and the El Niño Southern Oscillation sks.to/elnino
The Pacific Decadal Oscillation (PDO) is not causing global warming sks.to/pdo
Is the science settled? sks.to/settled
The difference between weather and climate sks.to/weather
Clearing up misconceptions regarding 'hide the decline' sks.to/decline
Tree-ring proxies and the divergence problem' sks.to/diverge
What ended the Little Ice Age? sks.to/lia
How does the Medieval Warm Period compare to current global temperatures? sks.to/mwp

 

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Posted by John Mason on Tuesday, 21 May, 2024


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