No. The Miocene is not an example of the “last time it was as warm as it’s going to get later this century”… Argh!
Guest ridicule by David Middleton
From ARS Technica, one of the most incoherent things I’ve ever read…
WAIT, THERE IS HOPE! —
What happened last time it was as warm as it’s going to get later this century?
Kids today will be grandparents when most climate projections end—does the past have more hints?
HOWARD LEE – 6/18/2018
The year 2100 stands like a line of checkered flags at the climate change finish line, as if all our goals expire then. But like the warning etched on a car mirror: it’s closer than it appears. Kids born today will be grandparents when most climate projections end.
And yet, the climate won’t stop changing in 2100. Even if we succeed in limiting warming this century to 2ºC, we’ll have CO2 at around 500 parts per million. That’s a level not seen on this planet since the Middle Miocene, 16 million years ago, when our ancestors were apes. Temperatures then were about 5 to 8ºC warmer not 2º, and sea levels were some 40 meters (130 feet) or more higher, not the 1.5 feet (half a meter) anticipated at the end of this century by the 2013 IPCC report.
Why is there a yawning gap between end-century projections and what happened in Earth’s past? Are past climates telling us we’re missing something?
Can the Miocene tell our future?
The Mid-Miocene Climate Optimum (MMCO) was an ancient global warming episode when CO2 levels surged from less than 400ppm to around 500ppm.
The shocking thing is that Howard Lee has a degree in geology. The fact that he makes his living as an “Earth Science writer” and not as a geologist might just be relevant.
Can the Miocene tell our future? I’ll let Bubba’s mom answer that question:
The fact that atmospheric CO2 levels may have surged from 400 to 500 ppm during the Middle Miocene Climatic Optimum is completely and totally fracking irrelevant in the Quaternary Period.
While the configuration of the continents was superficially similar to the modern world, there were substantial differences.
Estimates of MMCO atmospheric CO2 levels range from less than 200 to about 500 ppm…
Modern atmospheric CO2 levels are already within the MMCO range, but temperatures are MUCH, MUCH cooler than they were during the Miocene.
Oceanic and atmospheric circulation patterns were totally different in the Miocene. Atmospheric CO2 levels are not the reason the Miocene was warmer than the Pliocene and Quaternary.
Tectonics and paleoclimate
The Miocene saw a change in global circulation patterns due to slight position changes of the continents and globally warmer climates. Conditions on each continent changed somewhat because of these positional changes, however it was an overall increase in aridity through mountain-building that favored the expansion of grasslands. Because the positions of continents in the Miocene world were similar to where they lie today, it is easiest to describe the plate movements and resulting changes in the paleoclimate by discussing individual continents.
In North America, the Sierra Nevada and Cascade Mountain ranges formed, causing a non-seasonal and drier mid-continent climate. The increasing occurrences of drought and an overall decrease in absolute rainfall promoted drier climates. Additionally, grasslands began to spread, and this led to an evolutionary radiation of open-habitat herbivores and carnivores. The first of the major periods of immigration via the Bering land connection between Siberia and Alaska occurred in the middle of the Miocene, and by the end of the Miocene the Panama isthmus had begun to form between Central and South America.
Plate tectonics also contributed to the rise of the Andes Mountains in South America, which led to the formation of a rain shadow effect in the southeastern part of the continent. The movement of the plates also facilitated trends favoring non-desert and highland environments.
In Australia, the climate saw an overall increase in aridity as the continent continued to drift northwards, though it went through many wet and dry periods. The number of rainforests began to decrease and were replaced by dry forests and woodlands. The vegetation began to shift from closed broad-leaved forests to more open, drier forests as well as grasslands and deserts.
Eurasia also experienced increasing aridification during the Miocene. Extensive steppe vegetation began to appear, and the grasses became abundant. In southern Asia, grasslands expanded, generating a greater diversity of habitats. However, southern Asia was not the only area to experience an increase in habitat variability. Southern Europe also saw an increase in grasslands, but maintained its moist forests. Although most of Eurasia experienced increasing aridity, some places did not. The climate in some Eurasian regions, such as Syria and Iran, remained wet and cool.
During the Miocene, Eurasia underwent some significant tectonic rearrangements. The Tethys Sea connection between the Mediterranean and Indian Ocean was severed in the mid-Miocene causing an increase in aridity in southern Europe (see next paragraph for more on this). The Paratethys barrier, which isolated western Europe from the exchange of flora and fauna, was periodically disrupted, allowing for the migration of animals. Additionally, faunal routes with Africa were well established and occasional land bridges were created.
Africa also encountered some tectonic movement, including rifting in East Africa and the union of the African-Arabian plate with Eurasia. Associated with this rifting, a major uplift in East Africa created a rain shadow effect between the wet Central-West Africa and dry East Africa. The union of the continents of Africa and Eurasia caused interruption and contraction of the Tethys Sea, thereby depleting the primary source of atmospheric moisture in that area. Thus rainfall was significantly reduced, as were the moderating effects of sea temperature on the neighboring land climates. However, this union enabled more vigorous exchanges of flora and fauna between Africa and Eurasia.
Antarctica became isolated from the other continents in the Miocene, leading to the formation of a circumpolar ocean circulation. Global ocean and atmospheric circulation were also affected by the formation of this circumpolar circulation pattern, as it restricted north-south circulation flows. This reduced the mixing of warm, tropical ocean water and cold, polar water causing the buildup of the Antarctic polar ice cap. This enhanced global cooling and accelerated the development of global seasonality and aridity.
Notice anything missing from the UCMP Berkeley discussion of the Miocene paleoclimate? I’ll give you a hint: It starts with a “C” and ends with a “2.”
We’ve already experienced nearly 1 ºC of warming since pre-industrial time. Another 0.5 to 1.0 ºC between now and the end of the century doesn’t even put us into Eemian climate territory, much less the Miocene.
Back to the ARS Technica nonsense…
130 feet of sea level rise
Between a third and three-quarters of Antarctic ice melted. Land liberated by retreating ice sprouted tundra and forests of beech and conifers, which can’t have happened unless Antarctic summers were warmer than 10ºC (50ºF—much warmer than the -5ºC/23ºF it is today). It’s not clear what Greenland was up to, but there may have been a small ice sheet in Northern Greenland that melted substantially.
Consequently, sea levels rose by a whopping 40 meters or so (~130 feet). To put that in perspective, Mid-Miocene-like sea levels today would draw a new US Atlantic coast roughly along Interstate 95 through Philadelphia, Baltimore, Richmond and Fayetteville, North Carolina, inundating the New York-New Jersey-Connecticut metro area, Boston, most of Florida, and the coastal Gulf of Mexico. Similar things would happen across densely populated lowland areas around the globe, home to a quarter of the world’s people.
Forty meters is just a bit more than the latest projections for modern sea level rise of 1-3 feet by 2100, and 4.5 to 5.25 feet (1.4-1.6 meters—home to about 5 percent of the world’s population) by 2300, assuming we stabilize warming to around 2ºC. The difference is, once again, partly explained by time. According to the 2017 US National Climate Assessment, 2ºC of warming would commit us to a loss of three-fifths of Greenland’s ice and one third of Antarctic ice, resulting in 25m (80ft) of sea level rise—but occurring over 10,000 years.
Even so, the Miocene hints that modern sea level rise could be larger and more rapid.
2 ºC of warming would commit us to a loss of three-fifths of Greenland’s ice and one third of Antarctic ice, resulting in 25m (80ft) of sea level rise—but occurring over 10,000 years.
The East Antarctic ice sheet, 86% of Antarctica’s ice, hasn’t substantially melted in 8 million years.
You can’t get there from here!
The Greenland Ice Sheet didn’t even shrink by 3/5’s during the Eemian, when the Arctic was more than 5 ºC warmer than it is today.
“Even so, the Miocene hints that modern sea level rise could be larger and more rapid.”
To paraphrase the judge in the Donny Berger case in That’s My Boy… “That is just fracking mental.” Warning F-bomb alert: she didn’t say “fracking.”
It really takes a special kind of stupid to base a whacked out climate catastrophe fantasy on the 400-500 ppm rise in atmospheric CO2 during of the Middle Miocene Climatic Optimum.
There’s a bunch of them. I’ll get…
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