Holocene Climate Variations
I'm a fossil curator for the Natural History Society of Maryland, with a background in historical geology, via being enrolled for 4 years in an honors geology program, and being a teacher at the Smithsonian Museum of Natural History's Naturalist Center for 3 years, back in the 1980s.
On July 11, 2018, I gave a talk at the society, that in part involved extinction and climate change over the past 1 billion years. The following is what I found with regard to climate change during the Holocene Epoch, from roughly the time of termination of the last major ice age, to the present.
“The end of the Younger Dryas, about 11,500 years ago, was particularly abrupt. In Greenland, temperatures rose 10°C (18°F)” - NOAA https://www.ncdc.noaa.gov/abrupt-climate-change/The%20Younger%20Dryas
Depending on who you read, the Holocene is divided into a number of climactic periods. I have choosen these 5 as representative of the conditions.
Preboreal (10 ka–9 ka) https://www.sciencedirect.com/science/article/pii/S0277379101001482
Boreal (9 ka–8 ka) https://en.wikipedia.org/wiki/Boreal_(period)
Atlantic (8 ka–5 ka) https://en.wikipedia.org/wiki/Atlantic_(period)
Subboreal (5 ka–2.5 ka) https://en.wikipedia.org/wiki/Subboreal
Subatlantic (2.5 ka–present) https://en.wikipedia.org/wiki/Subatlantic
The Preboreal Oscillation can be attributed to a massive meltwater discharge from an abrupt drainage of glacial Lake Agassiz, Canada, via the Mackenzie River into the Arctic Ocean. A volume of 13,048 miles was discharged over a 1.5–3 yr period, equivalent to a 6 m rise in the Arctic Ocean . The flood occurred at about 11,335 BP. In10,750 BP, the southern outlet of Lake Agassiz reopened and diverted drainage to the Mississippi River system.
Boreal: Sea rise brought isolation by drowning entire coasts. In Europe, Ireland was cut off early in the Boreal, suffering an impoverishment of species. Britain was cut off by the end. Forest replaced the open lands in Europe, and forest-dwelling animals spread from southern areas and replaced the ice-age tundra mammals.
Atlantic: The warmest period of the Holocene, and is often referenced to as the Holocene climatic optimum. The sea rose to 9 feet above its present level. The temperature rise extended southern climates northward in a relatively short period. The treelines on northern mountains rose by 2000–3000 feet. Heat-loving species migrated northward.
Subboreal: Equivalent to most of the Neolithic and the entire Bronze Age. The climate was generally dryer and slightly cooler than in the preceding Atlantic, but still warmer than today. The Aegean area was marked by a pronounced drought. The lakes of subtropical Africa experienced a rapid fall in water levels. Arid conditions lead to the fall of Uruk and the Akkadian Empire, and possibly the end of Egypt’s Old Kingdom.
Subatlantic: began with the Roman Warm Period which lasted to the beginning of the 4th century. Analysis of Alpine glaciers concluded that the period AD 100-400 was significantly warmer than the periods that immediately preceded and followed. The drying and cooling that followed, an average winter temperature drop of 0.4°C centered around 350 AD, may have forced the Huns to move west, thus in turn triggering the migrations of the Germanic tribes.
After this relatively short cool interlude, the climate warmed again and reached between 800 and 1200 almost the values of the Roman Warm Period. This event is known as the Medieval Warm Period. It enabled the Vikings to settle in Iceland and Greenland. As Europe moved into the Little Ice Age, a decrease in temperature and a great number of devastating floods disrupted harvests and caused mass famine. Many settlements were abandoned and left deserted.
The Little Ice Age: (1300–1870), occurred in two pulses. The coldest period,(1645–1715), corresponds with the Maunder Minimum, a time when sunspots became exceedingly rare. During a 28-year period (1672–1699), observations revealed fewer than 50 sunspots. This contrasts with the typical 40,000–50,000 sunspots seen in modern times. Another period of low sunspot count, The Dalton Minimum, (1790–1830), also saw lower-than-average global temperatures. The earlier Spörer Minimum,(1400–1510), also coincided with a time when Earth's climate was colder than average.
The end of the Little Ice Age roughly corresponds to the Industrial Revolution.
From the data, it appears that climate changes often, and sometime rather quickly, and for a variety of reasons: Malankovitch Cycles, Sunspot Activity, and most important, Volcanic Eruptions.
My question still is, by what scientific method can we tell the difference between natural and manmade warming? Bill Nye of all people, an actor who goes around accusing people of being “Deniers” should have known this, but he was stumped.
I’ve been given a promising lead that I’m looking into, that may provided the answer.
With regard to S. Science, while I agree warming is a major concern, the “scientists” involved seem to habitually ignore these inconvenient truths. In other words, they’re engaging in the same behavior as those they accuse of being “deniers.” In psychology, this is called Projection.
On July 11, 2018, I gave a talk at the society, that in part involved extinction and climate change over the past 1 billion years. The following is what I found with regard to climate change during the Holocene Epoch, from roughly the time of termination of the last major ice age, to the present.
“The end of the Younger Dryas, about 11,500 years ago, was particularly abrupt. In Greenland, temperatures rose 10°C (18°F)” - NOAA https://www.ncdc.noaa.gov/abrupt-climate-change/The%20Younger%20Dryas
Depending on who you read, the Holocene is divided into a number of climactic periods. I have choosen these 5 as representative of the conditions.
Preboreal (10 ka–9 ka) https://www.sciencedirect.com/science/article/pii/S0277379101001482
Boreal (9 ka–8 ka) https://en.wikipedia.org/wiki/Boreal_(period)
Atlantic (8 ka–5 ka) https://en.wikipedia.org/wiki/Atlantic_(period)
Subboreal (5 ka–2.5 ka) https://en.wikipedia.org/wiki/Subboreal
Subatlantic (2.5 ka–present) https://en.wikipedia.org/wiki/Subatlantic
The Preboreal Oscillation can be attributed to a massive meltwater discharge from an abrupt drainage of glacial Lake Agassiz, Canada, via the Mackenzie River into the Arctic Ocean. A volume of 13,048 miles was discharged over a 1.5–3 yr period, equivalent to a 6 m rise in the Arctic Ocean . The flood occurred at about 11,335 BP. In10,750 BP, the southern outlet of Lake Agassiz reopened and diverted drainage to the Mississippi River system.
Boreal: Sea rise brought isolation by drowning entire coasts. In Europe, Ireland was cut off early in the Boreal, suffering an impoverishment of species. Britain was cut off by the end. Forest replaced the open lands in Europe, and forest-dwelling animals spread from southern areas and replaced the ice-age tundra mammals.
Atlantic: The warmest period of the Holocene, and is often referenced to as the Holocene climatic optimum. The sea rose to 9 feet above its present level. The temperature rise extended southern climates northward in a relatively short period. The treelines on northern mountains rose by 2000–3000 feet. Heat-loving species migrated northward.
Subboreal: Equivalent to most of the Neolithic and the entire Bronze Age. The climate was generally dryer and slightly cooler than in the preceding Atlantic, but still warmer than today. The Aegean area was marked by a pronounced drought. The lakes of subtropical Africa experienced a rapid fall in water levels. Arid conditions lead to the fall of Uruk and the Akkadian Empire, and possibly the end of Egypt’s Old Kingdom.
Subatlantic: began with the Roman Warm Period which lasted to the beginning of the 4th century. Analysis of Alpine glaciers concluded that the period AD 100-400 was significantly warmer than the periods that immediately preceded and followed. The drying and cooling that followed, an average winter temperature drop of 0.4°C centered around 350 AD, may have forced the Huns to move west, thus in turn triggering the migrations of the Germanic tribes.
After this relatively short cool interlude, the climate warmed again and reached between 800 and 1200 almost the values of the Roman Warm Period. This event is known as the Medieval Warm Period. It enabled the Vikings to settle in Iceland and Greenland. As Europe moved into the Little Ice Age, a decrease in temperature and a great number of devastating floods disrupted harvests and caused mass famine. Many settlements were abandoned and left deserted.
The Little Ice Age: (1300–1870), occurred in two pulses. The coldest period,(1645–1715), corresponds with the Maunder Minimum, a time when sunspots became exceedingly rare. During a 28-year period (1672–1699), observations revealed fewer than 50 sunspots. This contrasts with the typical 40,000–50,000 sunspots seen in modern times. Another period of low sunspot count, The Dalton Minimum, (1790–1830), also saw lower-than-average global temperatures. The earlier Spörer Minimum,(1400–1510), also coincided with a time when Earth's climate was colder than average.
The end of the Little Ice Age roughly corresponds to the Industrial Revolution.
From the data, it appears that climate changes often, and sometime rather quickly, and for a variety of reasons: Malankovitch Cycles, Sunspot Activity, and most important, Volcanic Eruptions.
My question still is, by what scientific method can we tell the difference between natural and manmade warming? Bill Nye of all people, an actor who goes around accusing people of being “Deniers” should have known this, but he was stumped.
I’ve been given a promising lead that I’m looking into, that may provided the answer.
With regard to S. Science, while I agree warming is a major concern, the “scientists” involved seem to habitually ignore these inconvenient truths. In other words, they’re engaging in the same behavior as those they accuse of being “deniers.” In psychology, this is called Projection.