In their seminal piece on the emerging Hyper-Anthropocene, James Hansen and co-authors provide a photo of mysterious boulders on a cliff overlooking the Atlantic Ocean. The boulders, we now know after extensive research by many geological experts, were dredged from the ocean floor, taken up and over a cliff and left there like Easter Island statuary, in a great storm event during a past interglacial warming epoch. The largest weighs about 2300 tons.
|Bangladesh with 1m sea level rise; |
Bates, Climate in Crisis (1990)
The CO2 dial must be turned to ∼ 260 ppm to achieve a Holocene-level interglacial. CO2 ∼ 250 ppm was sufficient for quasi-interglacials in the period 800–450,000 years before present, with sea level 10–25 m lower than in the Holocene. Interglacials with CO2 [at]∼ 280 ppm, i.e., the Eemian and Holsteinian (400,000 years ago), were warmer than the Holocene and had sea level at least several meters higher than today.
Bates, Climate in Crisis (1990)The IPCC (2013) report increased estimates of sea level rise compared to prior IPCC reports, but scenarios they discuss are close to linear responses to the assumed rising climate forcing. The most extreme climate forcing [RCP8.5, 936 ppm CO2 in 2100] is estimated to produce 0.74 m sea level rise in 2100 relative to the 1986–2005 mean sea level, with the “likely” range of uncertainty 0.52–0.98 m.
|Bates, Climate in Crisis (1990)|
Bates, Climate in Crisis (1990)The boulders must have been transported to their present position by waves, as two of the largest ones are located on the crest of the island’s ridge, eliminating the possibility that they were moved downward by gravity or are the karstic remnants of some ancient landscape. A tsunami conceivably could have deposited the boulders, but the area is not near a tectonic plate boundary. The coincidence of a tsunami at the end-Eemian moment is improbable given the absence of evidence of tsunamis at other times in the Bahamas and the lack of evidence of tsunamis on the Atlantic Coastal Plain of the United States. The proximity of run-up deposits and nested chevron ridges across a broad front of Bahamian islands is clear evidence of a sustained series of high-energy wave events.
Temperature change in 2065, 2080 and 2096 for 10 year doubling time should be thought of as results when sea level rise reaches 0.6, 1.7 and 5 m, because the dates depend on initial freshwater flux. Actual current freshwater flux may be about a factor of four higher than assumed in these initial runs, as we will discuss, and thus effects may occur 20 years earlier. A sea level rise of 5 m [16 feet] in a century is about the most extreme in the paleo record but the assumed 21st century climate forcing is also more rapidly growing than any known natural forcing.
|Bates, Climate in Crisis (1990)|
[T]here is no morally defensible excuse to delay phase-out of fossil fuel emissions as rapidly as possible. We conclude that the 2◦C global warming “guardrail”, affirmed in the Copenhagen Accord (2009), does not provide safety, as such warming would likely yield sea level rise of several meters along with numerous other severely disruptive consequences for human society and ecosystems. … Given the inertia of the climate and energy systems, and the grave threat posed by continued high emissions, the matter is urgent and calls for emergency cooperation among nations.