Occasional Thoughts on Climate Change

[LibertyBell]

7 hours ago, TheClimateChanger said:

File this under controversial, but I was doing some "light" reading on the climate from past authorship in the early/mid 19th century over the holiday as I enjoy reading about past climate. I was rather surprised that the great minds of the 18th and early 19th century did not believe there was any appreciable change in climate from antiquity. In fact, this was the prevailing school of thought into the first half of the 20th century.  The modern idea of a "medieval warm period" did not really arise until 1965 with H. H. Lamb's publication on the matter, although that built off scholarship from the preceding few decades. I reviewed that article, and found the persuasiveness somewhat lacking. Evidence against a large change was repeatedly dismissed, and when proxy evidence did not correspond to the desired result, it was adjusted and then adjusted some more. The timing of the supposed warm period even seems inconsistent with the modern view - showing warming most pronounced in England from like 1100-1300 CE, whereas now it's more like 800-1000 CE. Icelandic records of sea ice are suggestive of a climate in the North Atlantic much colder than present by the early/mid 13th century (and even colder than the 19th century), but these are dismissed by Lamb.

It looks like the idea of a medieval warm period reached its zenith in 1990, with the publication of the first IPCC report, which had an absurd hump for the medieval warm period extending even into the 14th century, despite loads of evidence that it was significantly colder in the 13th and 14th centuries. Hmmm, I wonder why that graphic made it in there? Modern reconstructions such as that appearing in more recent IPCC publications instead show a slight and gradual cooling trend over the entire millenia, abruptly ceasing in the 19th century. The medieval warm period is a small blip in the record. It would appear modern research largely confirms the prevailing scientific wisdom of the 18th and 19th century that there was no significant change in climate in the preceding 2000 years. Personally, I attach great significance to the conclusions of this era, since we are told these scientists and fathers of modern meteorology and climatology were living in the end of a "little ice age." Despite this, they looked at the same evidence we have and concluded there was no significant change in climate from the so-called medieval warm period to the era in which they were living. They may have had access to even more records which have been lost to the hands of time. Yet, some here today like to claim the medieval warm period was even warmer than our current globally-warmed times. These scientists also weren't burdened by the "woke" nonsense of today and would have had no pecuniary interest in their findings. AGW wasn't even known in that era... their only motivation was a desire to find the scientific truth. No money was being showered upon them by vested interests.

Despite the foregoing, it would seem many here - even those who accept the scientific reality of anthropogenic climate change - attach an unreasonable significance to the medieval warm period, suggesting it may have been as warm and snowless as recent years. I feel like Band-Aid, except instead of "Do they know its Christmastime at all," it's "do they know the current era is far, far warmer than the so-called medieval warm period?" as per the most reliable temperature / climate reconstructions?

What's the truth here? Is there even a medieval warm period and little ice age, or was it more or less, just a natural prolonged and gradual climatic cooling that was interrupted by human activities? Some say it was only a "local" phenomenon and not global. But user @blizzard1024made a good point about this some years back. That's not how the atmospheric circulation works. It seems suspect that there would be sustained local anomalies of warm and cold in a global system. He, of course, concluded that means the medieval warm period was a global phenomenon. But another conclusion that can be drawn is that there simply wasn't a medieval warm period of any significance, local or otherwise, and the temperature departures from that era were not anything significant? More credence ought to be given to the formerly prevailing view of a largely static climate regime over the past 2,000 years. After all, the scientists who reached this conclusion were living in the very region said to be most affected by the MWP and LIA and could find no strong evidence of cooling from the published records and local histories. Modern temperature reconstructions appear more consistent with this view than the one that had its brief zenith in the mid to late 20th century of much more significant global temperature changes.

@donsutherland1 @Typhoon Tip

Read about the winter of 1782-1783

It was absolutely amazing and all because of a little volcano in Iceland.

 

 

[chubbs]

19 hours ago, TheClimateChanger said:

File this under controversial, but I was doing some "light" reading on the climate from past authorship in the early/mid 19th century over the holiday as I enjoy reading about past climate. I was rather surprised that the great minds of the 18th and early 19th century did not believe there was any appreciable change in climate from antiquity. In fact, this was the prevailing school of thought into the first half of the 20th century.  The modern idea of a "medieval warm period" did not really arise until 1965 with H. H. Lamb's publication on the matter, although that built off scholarship from the preceding few decades. I reviewed that article, and found the persuasiveness somewhat lacking. Evidence against a large change was repeatedly dismissed, and when proxy evidence did not correspond to the desired result, it was adjusted and then adjusted some more. The timing of the supposed warm period even seems inconsistent with the modern view - showing warming most pronounced in England from like 1100-1300 CE, whereas now it's more like 800-1000 CE. Icelandic records of sea ice are suggestive of a climate in the North Atlantic much colder than present by the early/mid 13th century (and even colder than the 19th century), but these are dismissed by Lamb.

It looks like the idea of a medieval warm period reached its zenith in 1990, with the publication of the first IPCC report, which had an absurd hump for the medieval warm period extending even into the 14th century, despite loads of evidence that it was significantly colder in the 13th and 14th centuries. Hmmm, I wonder why that graphic made it in there? Modern reconstructions such as that appearing in more recent IPCC publications instead show a slight and gradual cooling trend over the entire millenia, abruptly ceasing in the 19th century. The medieval warm period is a small blip in the record. It would appear modern research largely confirms the prevailing scientific wisdom of the 18th and 19th century that there was no significant change in climate in the preceding 2000 years. Personally, I attach great significance to the conclusions of this era, since we are told these scientists and fathers of modern meteorology and climatology were living in the end of a "little ice age." Despite this, they looked at the same evidence we have and concluded there was no significant change in climate from the so-called medieval warm period to the era in which they were living. They may have had access to even more records which have been lost to the hands of time. Yet, some here today like to claim the medieval warm period was even warmer than our current globally-warmed times. These scientists also weren't burdened by the "woke" nonsense of today and would have had no pecuniary interest in their findings. AGW wasn't even known in that era... their only motivation was a desire to find the scientific truth. No money was being showered upon them by vested interests.

Despite the foregoing, it would seem many here - even those who accept the scientific reality of anthropogenic climate change - attach an unreasonable significance to the medieval warm period, suggesting it may have been as warm and snowless as recent years. I feel like Band-Aid, except instead of "Do they know its Christmastime at all," it's "do they know the current era is far, far warmer than the so-called medieval warm period?" as per the most reliable temperature / climate reconstructions?

What's the truth here? Is there even a medieval warm period and little ice age, or was it more or less, just a natural prolonged and gradual climatic cooling that was interrupted by human activities? Some say it was only a "local" phenomenon and not global. But user @blizzard1024made a good point about this some years back. That's not how the atmospheric circulation works. It seems suspect that there would be sustained local anomalies of warm and cold in a global system. He, of course, concluded that means the medieval warm period was a global phenomenon. But another conclusion that can be drawn is that there simply wasn't a medieval warm period of any significance, local or otherwise, and the temperature departures from that era were not anything significant? More credence ought to be given to the formerly prevailing view of a largely static climate regime over the past 2,000 years. After all, the scientists who reached this conclusion were living in the very region said to be most affected by the MWP and LIA and could find no strong evidence of cooling from the published records and local histories. Modern temperature reconstructions appear more consistent with this view than the one that had its brief zenith in the mid to late 20th century of much more significant global temperature changes.

@donsutherland1 @Typhoon Tip

Last 12 months GISS temperatures vs 1881-1910. Warming is maximized over Northern Hemisphere land, which is more sensitive to climate change and natural variability. Not surprising that MWP and LIA appear more significant there.  Since 1990 more information has been obtained for the rest of the world, reducing the climate importance of both eras.

1.5C warming on a global basis is very significant. Roughly  25% of an ice age swing from complete glaciation to warm interglacial. The earth hasn't been this warm since the last interglacial 120,000 years ago, and we continue to warm rapidly, roughly 20x faster than the last deglaciation. In a decade or two we will have to go back several  million years.

[LibertyBell]

1 hour ago, chubbs said:

Last 12 months GISS temperatures vs 1881-1910. Warming is maximized over Northern Hemisphere land, which is more sensitive to climate change and natural variability. Not surprising that MWP and LIA appear more significant there.  Since 1990 more information has been obtained for the rest of the world, reducing the climate importance of both eras.

1.5C warming on a global basis is very significant. Roughly  25% of an ice age swing from complete glaciation to warm interglacial. The earth hasn't been this warm since the last interglacial 120,000 years ago, and we continue to warm rapidly, roughly 20x faster than the last deglaciation. In a decade or two we will have to go back several  million years.

we can forget about 1.5, 2.5 is much more likely by 2050

[TheClimateChanger]

3 hours ago, chubbs said:

Last 12 months GISS temperatures vs 1881-1910. Warming is maximized over Northern Hemisphere land, which is more sensitive to climate change and natural variability. Not surprising that MWP and LIA appear more significant there.  Since 1990 more information has been obtained for the rest of the world, reducing the climate importance of both eras.

1.5C warming on a global basis is very significant. Roughly  25% of an ice age swing from complete glaciation to warm interglacial. The earth hasn't been this warm since the last interglacial 120,000 years ago, and we continue to warm rapidly, roughly 20x faster than the last deglaciation. In a decade or two we will have to go back several  million years.

Yes, I know all that. I never really looked into the medieval warm period, and assumed it was more robust and significant based on how people refer to it on this website. They make it sound like the Eocene or some period of eternal warming. But many of the lines of evidence to support that appear to be superstitious hocus pocus.

Would it surprise people to learn that grapes were successfully grown in parts of England for winemaking even during the heart of the so-called little ice age? And there are plenty of vineyards today in England. Why is so much significance given to the cultivation of grapes in medieval times? No special significance was afforded this by the great minds of the past, with evidence of cultivation being rather limited, and evidence that the wine was of low class. There was no need to grow grapes in England in the 19th century, when fine wines could be imported from France and Italy.

Would it surprise people to learn that the opposite was said to be true around the Black Sea and surrounding parts of Europe? That is, grapes were said to be cultivated in places in the so-called Little Ice Age where there was no prior record of their cultivation?

Would it surprise people to learn that the native "forests" of Iceland were principally shrubby bushes, as they are today, unsuitable for most building? And the Viking sagas considered it a great feat that two of the early settlers were able to assemble enough wood to build a boat to sail to Norway.

The Viking sagas describe Vinland as a place with nearly equal day and night, but where on the shortest day, the sun rises at 7:30 and sets at 4:30. I don't know about you, but that doesn't sound like L'Anse Aux Meadows to me.

The Viking settlements at Greenland may have failed, but there is little concrete evidence of the role climate change played. Mostly, it was mismanagement, and loss of trade/contact with the mother country which was in the throes of the Black Death. It's likely there was disease and epidemics in the colonies as well.

Much significance is attached to cultivation of barley in Iceland during the medieval times, yet in Scotland, the range for cultivation of grains was both northward and higher in altitude than in its historic range during the LIA than during the MWP [which was attributed by the writers to advancements in agriculture, not evidence of climate change].

[TheClimateChanger]

The point is we have had people for decades treating AGW as some unproven theory, while past climate changes are accepted as 100% fact [and often grossly exaggerated]. In fact, the evidence for AGW is obviously 100s of times greater than any supposed evidence of these past eras. And indeed, most modern temperature reconstructions suggest the MWP was perhaps a 0.5C warmer than the heart of the LIA [not at all warmer than the present], and perhaps on par with the start of the 20th century on a global average. By all reliable measures, it was far colder than the present era on a global scale. Yet, there are some here who, even today, believe it was some period where it never snowed and winters torched all year around. What is the evidence for this nonsense?

In fact, if you attribute knowledge of the modern greenhouse effect to Svante Arrhenius, the characterization of the greenhouse effect [and the impact of carbon on the climate] far predates any formal characterization of the MWP? Yet, some say the modern reconstructions are "erasing" the MWP? The greatest minds living in the LIA looked at the same evidence that some trot around and concluded [correctly] that there was no massive change in climate. Obviously, they didn't have access to ice cores and tree rings, and things of that nature, that do provide support for some measure of warming, but much of the discussion is just nonsense. I mean you can make the same argument these folks make and say the MWP was "invented" in the late 20th century specifically to obfuscate the reality of human-caused climate change.

[TheClimateChanger]

The characterization of the Medieval Warm Period on Encyclopedia Brittanica versus Wikipedia is telling. Wikipedia presents it as uncontroverted fact, whereas here is how it is presented on Encyclopedia Brittanica:

Quote

medieval warm period (MWP), brief climatic interval that is hypothesized to have occurred from approximately 900 ce to 1300 (roughly coinciding with the Middle Ages in Europe), in which relatively warm conditions are said to have prevailed in various parts of the world, though predominantly in the Northern Hemisphere from Greenland eastward through Europe and parts of Asia.

The notion of a medieval warm period is highly controversial. Many paleoclimatologists claim that well-documented evidence for the phenomenon appears across the North Atlantic region, while others maintain that the phenomenon was global, occurring all over the world. Still other scientists insist that their data do not show appreciable changes in average temperature anywhere over the course of the interval. Meanwhile, global warming skeptics have used the MWP to bolster their position in the debate over the nature and effects of climate change.

 

Note it's a hypothesis, the extent of which is disputed among experts [i.e., whether it was a global phenomenon or if it even existed at all].

The graphic shown illustrates Mann's and Jones' reconstructions of Northern Hemisphere temperatures since 1000 C.E., and also includes H. H. Lamb's original reconstruction of Central England temperatures over the same interval [as presented in his 1965 work, which as best as I can tell was the first piece of scholarship to formerly characterize the MWP as a possible widespread event]:

This CET reconstruction is extremely flimsy. The proxies used didn't support such a massive jump. They were adjusted by Lamb to produce that effect... read the paper and see how many adjustments [on questionable assumptions] were made to produce that level of warming. The same thing climate deniers accuse scientists of doing today. The timing doesn't even make sense. Icelandic records of sea ice suggest cooling with lots of heavy sea ice conditions in the 1200s and 1300s. 1348 was said to be perhaps the coldest winter. How would there be such a huge disconnect between Iceland and central England?

Like I said, I'm just trying to figure out why there are so many that believe it was a period of no snow in North America, and what evidence there is to support that? There doesn't seem to be any.