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Global Warming / Climate Changes Pt. 19

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Re: Global Warming / Climate Changes Pt. 19

Unread postby vox_mundi » Thu 12 Oct 2017, 10:24:51

Geologic Evidence Suggests Ominous Prospects for Hurricanes on a Warming Earth

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http://www.sciencedirect.com/science/ar ... ihub#f0030

While strong seasonal hurricanes have devastated many of the Caribbean and Bahamian islands this year, geologic studies on several of these islands illustrate that much more extreme conditions existed in the past. A new analysis published in Marine Geology shows that the limestone islands of the Bahamas and Bermuda experienced climate changes that were even more extreme than historical events. In the interest of our future world, scientists must seek to understand the complexities of linked natural events and field observations that are revealed in the geologic record of past warmer climates.

In Bermuda and the Bahamas, the geology of the last interglacial (LIG; approximately 120,000 years ago) is exquisitely preserved in nearly pure carbonate sedimentary rocks. A record of superstorms and changing sea levels is exposed in subtidal, beach, storm, and dune deposits on multiple islands. Extensive studies by the authors over the past decades on these islands have documented stratigraphic, sedimentologic, and geomorphic evidence of major oceanic and climatic disruptions at the close of the last interglacial.

Dr. Paul J. Hearty, a retired Associate Professor at the University of North Carolina at Wilmington, and Dr. Blair. R. Tormey, a Coastal Research Scientist at Western Carolina University conducted an invited review of published findings. It demonstrates that during a global climate transition in the late last interglacial, also known as marine isotope substage 5e (MIS 5e), abrupt multi-meter sea-level changes occurred. Concurrently, coastlines of the Bahamas and Bermuda were impacted by massive storms generated in the North Atlantic Ocean, resulting in a unique trilogy of wave-transported deposits: megaboulders, chevron-shaped, storm-beach ridges, and runup deposits on high dune ridges.

While perhaps more mundane than the megaboulders (found only locally on Eleuthera), the sedimentological structures found within chevron ridge and runup deposits across islands throughout the Bahamas and Bermuda point to frequent and repeated inundation by powerful storm waves, in some locations leaving storm deposits tens of meters above sea level.
During the last interglacial, sea levels were about 3-9 meters higher than they are now. The geologic evidence indicates that the higher sea-levels were accompanied by intense "superstorms," which deposited giant wave-transported boulders at the top of cliffed coastlines, formed chevron-shaped, storm beach ridges in lowland areas, and left wave runup deposits on older dunes more than 30 meters above sea level. These events occurred at a time of only slightly warmer global climate and CO2 (about 275 ppm) was much lower than today.

The authors emphasize "the LIG record reveals that strong climate forcing is not required to yield major impacts on the ocean and ice caps." In our industrial world, rapidly increasing atmospheric CO2 has surpassed 400 ppm, levels not achieved since the Pliocene era about 3 million years ago, while global temperature has increased nearly 1 °C since the 1870s. Today, ice sheets are melting, sea level is rising, oceans are warming, and weather events are becoming more extreme.

Drs. Hearty and Tormey conclude that with the greatly increased anthropogenic CO2 forcing at rates unmatched in nature, except perhaps during global extinction events, dramatic change is certain. They caution that, "Our global society is producing a climate system that is racing forward out of humanity's control into an uncertain future. If we seek to understand the non-anthropogenic events of the last interglaciation, some of the consequences of our unchecked forward speed may come more clearly into focus...a message from the past; a glimpse into the future."

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P.J. Hearty et al. Sea-level change and superstorms; geologic evidence from the last interglacial (MIS 5e) in the Bahamas and Bermuda offers ominous prospects for a warming Earth, Marine Geology (2017).
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late.
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Re: Global Warming / Climate Changes Pt. 19

Unread postby dohboi » Thu 12 Oct 2017, 13:23:45

Wow, vox!

And then there's this:

Climate change impacts on Africa, in the coming decades, will not be limited to that continent as hunger drives tens to hundreds of millions of people to immigrant primarily northward to the EU (and elsewhere):

Fall Army Worm Arrives in Africa on the Heels of Climate Change

http://www.sierraclub.org/sierra/fall-a ... ate-change

A rapidly spreading invasive pest now threatens crops across the continent

Endemic to North and South America, the fall armyworm was first spotted in January 2016 in Nigeria. No one knows for certain how it arrived on the African continent, but since its initial appearance the pest has spread to more than 28 countries, including South Africa, Burundi, Rwanda, Kenya, Ethiopia, the Democratic Republic of Congo, and most recently, Sudan and Mali. As it has spread, it has destroyed more than 740,000 acres of maize, the staple food for more than 200 million Africans...


thanks to aslr at asif for text and link
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Re: Global Warming / Climate Changes Pt. 19

Unread postby dohboi » Sat 14 Oct 2017, 13:45:43

The linked reference concludes: "... the specific equilibrium climate sensitivity which considers radiative forcing of CO2 and land ice sheet (LI) albedo, S[CO2,LI], is larger during interglacial states than during glacial conditions by more than a factor two." This is not good news as consensus climate science typically assumes the modern ECS is essentially the same as that during the last glacial period. Thus is it conceivable that before 2100 the effective ECS (S[X) could be as high as 6C.


Peter Koehler, Lennert Stap, Anna von der Heydt, Bas de Boer, Roderik, S. W. van de Wal & Jonah Bloch-Johnson (4 October 2017), "A state-dependent quantification of climate sensitivity based on paleo data of the last 2.1 million years", Paleoceanography, DOI: 10.1002/2017PA003190

http://onlinelibrary.wiley.com/doi/10.1 ... 0/abstract

Abstract: "The evidence from both data and models indicates that specific equilibrium climate sensitivity S[X] — the global annual mean surface temperature change (ΔTg) as a response to a change in radiative forcing X (ΔR[X]) — is state-dependent. Such a state dependency implies that the best fit in the scatter plot of ΔTg versus ΔR[X] is not a linear regression, but can be some non-linear or even non-smooth function. While for the conventional linear case the slope (gradient) of the regression is correctly interpreted as the specific equilibrium climate sensitivity S[X], the interpretation is not straightforward in the non-linear case. We here explain how such a state-dependent scatter plot needs to be interpreted, and provide a theoretical understanding — or generalization — how to quantify S[X] in the non-linear case. Finally, from data covering the last 2.1 Myr we show that — due to state dependency — the specific equilibrium climate sensitivity which considers radiative forcing of CO2 and land ice sheet (LI) albedo, , is larger during interglacial states than during glacial conditions by more than a factor two."

thanks again to aslr for this
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