Most of the scientific discussion in Part 5 is about “irreversible positive feed back loops.” I have not had time to look up all the references, but Guy continues to focus the worst-case scenario of all the poorly understood instabilities that are almost invariably swept under the rug to avoid “scaring the kids.”
“Hope for the best, but prepare for the worst” sounds like a good strategy. Unfortunately, the following graph, which shows how global carbon emissions have grown over the last 250 years, does not seem to provide a lot of room for hope, unless —on a national and global scale— we manage to precipitate a dramatic tipping point in humanity’s sense of responsibility.
Here you have it: exponential growth. This curve shows that every 30 years we double the cumulative total of the CO2 we —read the Undustrialized Predators of World— have dumped into the atmosphere since the beginning of the Industrial Revolution. 1, 2, 4, 8, 16, 32, 64, … blows up really fast!
At 1 minute and 20 second time mark of the video there is a list of papers under the heading Irreversible positive feedbacks. The first paper is about methane hydrates in the Arctic Ocean and this is what the authors say about their work, Extensive Methane Venting to the Atmosphere from Sediments of the East Siberian Arctic Shelf:
To discern whether this extensive CH4 venting over the ESAS [East Siberian Arctic Shelf ] is a steadily ongoing phenomenon or signals the start of a more massive CH4 release period, there is an urgent need for expanded multifaceted investigations into these inaccessible but climate-sensitive shelf seas north of Siberia.
Is that an irreversible positive feedback? Maybe, but maybe not.
This is the next paper: Enhanced Modern Heat Transfer to the Arctic by Warm Atlantic Water
The Arctic is responding more rapidly to global warming than most other areas on our planet. Northward- flowing Atlantic Water is the major means of heat advection [flow] toward the Arctic and strongly affects the sea ice distribution. Records of its natural variability are critical for the understanding of feedback mechanisms and the future of the Arctic climate system, but continuous historical records reach back only ~150 years. Here, we present a multidecadal-scale record of ocean temperature variations during the past 2000 years, derived from marine sediments off Western Svalbard (79°N). We find that early–21st-century temperatures of Atlantic Water entering the Arctic Ocean are unprecedented over the past 2000 years and are presumably linked to the Arctic amplification of global warming.
That certainly sounds like a milestone on our way to the destruction of the world as we know it.
In the video Guy also refers to his blog, where you can find this statement:
Extent of Arctic sea ice passed a tipping point in 2007, according to research published in the February 2013 issue of The Cryosphere.
Oh my goodness, a tipping point? Indeed, the title of this paper is A recent tipping point in the Arctic sea-ice cover: abrupt and persistent increase in the seasonal cycle since 2007. It turns out that the tipping point we are talking about here is increase in the amplitude of the oscillations that can be seen in this figure, but as the authors write their “statistical methods cannot shed light on geophysical mechanisms.”
All of the above may indeed be what onset of run-away climate change looks like. Does it imply human extinction? I do not find the case Guy makes and his predicted timing spectacularly compelling. But, hey, if he’s right it will surely make the jellyfish of the world really happy. So, how bad can it be? How much worse, by the way, is human extinction than “just” wiping out 50% of humanity? Whatever we may have unleashed is certainly a source of concern
Because something is happening here
But you don’t know what it is
Do you, Mister Jones?