Archives par mot-clé : Holocene

How the Little Ice Age affected South American climate

by Fundação de Amparo à Pesquisa do Estado de São Paulo, July 24, 2018 in ScienceDaily


A new study published in Geophysical Research Journal shows that the so-called Little Ice Age — a period stretching from 1500 to 1850 in which mean temperatures in the northern hemisphere were considerably lower than at present — exerted effects on the climate of South America.

Based on an analysis of speleothems (cave formations) in the Brazilian states of Mato Grosso do Sul and Goiás, the study revealed that in the seventeenth and eighteenth centuries, the climate of southwestern Brazil was wetter than it is now, for example, while that of the country’s Northeast region was drier.

The same Brazilian cave records showed that the climate was drier in Brazil between 900 and 1100, during a period known as the Medieval Climate Anomaly (MCA), when the northern hemisphere’s climate was warmer than it is now.

 

Study: abrupt shifts occurred in the ancient European climate

by A. Watts, July 23, 2018 in WUWT and NatureCommunications


From the University of Helsinki and the “no SUV’s needed” department comes this study which suggests big cold snaps occurred right in the middle of the warm Eemian period. My only concern is perhaps they over-rely on climate models. For reference (and not part of the study) here’s the Eemian graph in context. Data sources listed int he graph.

New Science Affirms Arctic Region Was 6°C Warmer Than Now 9000 Years Ago, When CO2 Levels Were ‘Safe’

by K. Richard, July 12, 2018 in NoTricksZone


Unearthed new evidence (Mangerud and Svendsen, 2018) reveals that during the Early Holocene, when CO2 concentrations hovered around 260 ppm, “warmth-demanding species” were living in locations 1,000 km farther north of where they exist today in Arctic Svalbard, indicating that summer temperatures must have been about “6°C warmer than at present”.

Proxy evidence from two other new papers suggests Svalbard’s Hinlopen Strait  may have reached about 5 – 9°C warmer than 1955-2012 during the Early Holocene (Bartels et al., 2018), and Greenland may have been “4.0 to 7.0 °C warmer than modern [1952-2014]” between 10,000 and 8,000 years ago according to evidence found in rock formations at the bottom of ancient lakes (McFarlin et al., 2018).

In these 3 new papers, none of the scientists connect the “pronounced” and “exceptional” Early Holocene warmth to CO2 concentrations.

New Holocene geological subdivisions. The Anthropocene nowhere to be found.

by Javier, July 9, 2018 in WUWT


The International Commission on Stratigraphy (ICS) has announced that the proposal by the International Subcommission on Quaternary Stratigraphy (ISQS) for the subdivision of the Holocene Series/Epoch has been ratified unanimously by the International Union of Geological Sciences (IUGS).

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nb:  ‘No Christiana, the geologists do not think the Anthropocene is a concept worthy of consideration, and you should be better informed.’

Friday Funny- Welcome to the Anthropocene Narcisscene

by Mark Sagoff, June 29, 2018 in WUWT


In view of the glacial pace of geologic events and the time it takes for things to turn into rock or become encased in it, you might think there would be no hurry to name a new geologic epoch, especially because the current one, the Holocene, started only about 11,500 years ago. You would be wrong. In 2002, Crutzen published an article in Nature magazine, “Geology of Mankind,” which called on geologists “to assign the term ‘Anthropocene’ to the present, in many ways human-dominated, geological epoch, supplementing the Holocene — the warm period of the past 10–12 millennia” and the beginning of which roughly coincided with the advent of human agriculture.The idea of the Anthropocene, which Earth system scientists initiated and advocated, landed like a meteor, setting off a stampede among academics. Nature followed with an editorial that urged that the Anthropocene be added to the geologic timescale. “The first step is to recognize,” Nature editorialized, “that we are in the driver’s seat.”

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Scientists Find Sun-Driven Temperature Changes Led CO2 Changes By 1300-6500 Years In The Ancient Past

by Kenneth Richard, June 7, 2018 in NoTricksZone


It has long been established in the scientific literature (and affirmed by the IPCC) that CO2 concentration changes followed Antarctic temperature changes by about 600 to 1000 years during glacial-interglacial transitions throughout the last ~800,000 years (Fischer et al., 1999Monnin et al., 2001Caillon et al., 2003Stott et al., 2007Kawamura et al., 2007).
In contrast, two new papers cite evidence that the timing of the lagged CO2 response to temperature changes may have ranged between 1300 and 6500 years in some cases.  It would appear that a millennial-scale lagged response to temperature undermines the claim that CO2 concentration changes were a driver of climate in the ancient past.

New Scientific Evidence Robustly Affirms Scandinavian Temperatures Were 3-4°C Warmer 9000 Years Ago

by K. Richard, May 31, 2018 in NoTricksZone

Because trees may only grow within narrowly-defined temperature ranges and elevations above sea level, perhaps the most reliable means of assessing the air temperatures of past climates is to collect ancient treeline evidence.  In a new paper, Kullman (2018) found tree remnants at mountain sites 600 to 700 meters north of where the modern treeline ends, strongly implying Early Holocene air temperatures in northern Sweden were 3-4°C warmer than recent decades.

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Changes in the Rate of Sea Level Rise

by Willis Eschenbach, May 22, 2018 in WUWT


There’s been some discussion of the rate of sea level rise lately, so I thought I’d take a look at some underlying data.

I started with a 2016 paper by the modern master of failed serial doomcasting, James Hansen. It has the frightening title of Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2°C global warming could be dangerous… yikes! Be very afraid!

In Figure 29 of that paper, Hansen claims to show that sea level rise has been accelerating, from 0.6 mm/year from 1900 to 1930, to 1.4 mm/year from 1930 to 1992, and 2.6 mm/year from 1993 to 2015.

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Solar activity over nine millennia: A consistent multi-proxy reconstruction

by C.J. Wu et al., April 5, 2018 in Astronomy&Astrophysics


.pdf (13 pages)

The solar activity in the past millennia can only be reconstructed from cosmogenic radionuclide proxy records in terrestrial archives. However, because of the diversity of the proxy archives, it is difficult to build a homogeneous reconstruction. All previous studies were based on individual, sometimes statistically averaged, proxy datasets. Here we aim to provide a new consistent multi- proxy reconstruction of the solar activity over the last 9000 years, using all available long-span datasets of 10Be and 14C in terrestrial archives.

Another New Paper Shows Arctic Sea Ice Has Been INCREASING Overall Since The 1930s

by K.  Richard, March 1, 2018 in NoTricksZone


In his seminal 1982 book Climate, History, and the Modern World, the renown climatologist Dr. H.H. Lamb revealed that sea ice in the subarctic and Arctic regions was much less extensive during the Medieval Warm Period (9th-13th centuries) compared to today.

For example, records indicate that there were decadal and centennial-scale periods without any sea ice invading any of Iceland’s coasts.  These no-ice periods coincided with atmospheric CO2 concentrations of 275 ppm, which is about 130 ppm less than today’s calculated CO2 values.

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Why did gas hydrates melt at the end of the last ice age?

by GEOMAR Inst., February 12, 2018 in WUWT


GEOMAR researchers find links between sedimentation and methane seeps on the seafloor off the coast of Norway

Large amounts of the greenhouse gas methane are locked up as solid gas hydrates in the continental slopes of ocean margins. Their stability depends on low temperatures and high pressure. However, other factors that influence gas hydrate stability are not as well understood. A German-Norwegian research team has found evidence off the coast of Norway that the amount of sediment deposited on the seafloor can play a crucial role. The study has been published today in the international journal Nature Communications.

A never before western published paleoclimate study from China suggests warmer temperatures in the past

by A. Watts, February 11, 2018 in WUWT

Preliminary Conclusions:

1. During the first 2000 years of our 5000-year civilization, most of the time, the annual average temperature was 2ºC higher than now. The temperature in January was 3-5ºC higher than now.

2. From then on, there was a series of temperature fluctuations. The lowest temperatures occurred in AD 1000, 400, 1200, and 1700. The range of fluctuation was 1-2ºC.

3. In every 400-800 period, a smaller cycle lasting 50 to 100 years can be detected with a temperature range of 0.5 -1ºC.

4. During the above cycles, it seems that any coldest period started from the Pacific coast of East Asia. The cold waves then moved westward to Europe and the Atlantic coasts. And at the same time, there were also trends from the North to the South.

What are, in fact, the grounds for concern about global warming?

by Javier, January 30, 2018 in AndyMay WUWT


Climate change is a reality attested by past records. Concerns about preparing and adapting for climate change are real. However, the idea that we can prevent climate change from happening is dangerous and might be anti-adaptive. Certain energy policies that might have no effect on climate change could make us less able to adapt.

Physics shows that adding carbon dioxide leads to warming under laboratory conditions. It is generally assumed that a doubling of CO2 should produce a direct forcing of 3.7 W/m2 [1], that translates to a warming of 1°C (by differentiating the Stefan-Boltzmann equation) to 1.2°C (by models taking into account latitude and season). But that is a maximum value valid only if total energy outflow is the same as radiative outflow. As there is also conduction, convection, and evaporation, the final warming without feedbacks is probably less. Then we have the problem of feedbacks that we don’t know and cannot properly measure. For some of the feedbacks, like cloud cover we don’t even know the sign of their contribution. And they are huge, a 1% change in albedo has a radiative effect of 3.4 W/m2 [2], almost equivalent to a full doubling of CO2.

Northern South China Sea SST changes over the last two millennia and possible linkage with solar irradiance

by Deming Kong et al., November 30, 2017 in Quaternary International


High-resolution surface temperature records over the last two millennia are crucial to understanding the forcing and response mechanism of Earth’s climate. Here we report a bidecadal-resolution sea surface temperature (SST) record based on long-chain alkenones in a gravity sediment core retrieved from the northern South China Sea. SST values varied between 26.7 and 27.5 °C, with a total variability ∼1 °C over the last 2000 years.