Books by Mark Lynas:
Six Degrees: Our Future on a Hotter Planet and others

Six Degrees: Our Future on a Hotter Planet

In a hundred years, the Earth will be between 1.4° and 5.8° Celsius warmer. Radical and visible changes will result, including increases in coastal submersion, wildfires, and storm strengths. Much of the biosphere will go extinct. Homo Sapiens itself will be threatened with a population crash.

Six Degrees, based on peer-reviewed scientific articles, sophisticated computer models, and geoclimatology, is the scariest book I read this decade.

Lynas' previous book High Tide: News from a Warming World showed changes already seen on tidal height, weather, and biology. Six Degrees shows us the future.

The particularly intelligent thing about this book is that it is organized by years that certain events will occur, but instead it is in sections each of which describes what will be seen for its temperature increase.

These are some changes that Lynas shows for the different temperature rises:

  1. 1° C (2° F). "The current episode of global warming, of about 0.7° C [1.3° F] in the last century, has pushed Earth's temperature up to levels unprecedented in recent history ... no proxy records ... show any time in the last 1,300 years that was as warm as now. Indeed, records from the deep sea suggest that temperature are now within a degree of their highest levels for no less than a million years" [p.46].
    "The Arctic icecap has been in constant retreat since about 1980 ... Each year on average 100,000 square kilometers of new open ocean is revealed" [p.48] with a tipping point into a self-reinforcing and unpreventable melting of the Arctic icecap to begin as late as 2040 but as early as 2012.
    Mountains like the Matterhorn (their highest slopes previously stabilized by permafrost) are collapsing because melt zones are penetrating deeper than before. Bleaching of coral reefs will become an annual instead of a rare event. Animals like the pika may be pushed in a heat-forced migration up mountain into decreasingly small areas and into extinction.
    The Pacific island of Tuvalu, already experiencing high-tide flooding and salt-water intrusion, will be increasingly lost.

  2. 2° C (4° F). In 2003 about 30,000 people died as heatstroke victims in an intense Summer heat wave when the European temperatures averaged only 2° C above norm. "Over a billion tonnes of extra carbon poured out of plants and soil in response to the drought and heat" [p.82].
    "Each degree rise of temperature raises freezing levels by 150 meters [about 500 feet]. [In the Andes] Glaciers are currently found only above 5,000 meters ... [cities throughout Peru, Ecuador, and Bolivia] survive thanks to runoff from their mountain glaciers" [p.106]. Their populations will become climate refugees.
    Similarities "to the early Holocene (less than 10,000 years ago) and the last interglacial, around 130,000 years ago" [p.129].

  3. 3° C (5° F). "For the three-degree world, we have to go back much further, before the Earth entered its regular cycles of ice ages and interglacials. We have to go back a full three million years, to a period of time called the Pliocene ... [at which time] [o]ur primate ancestors were still exclusively in Africa" [pp.129-130], a time when the current ice barrens of Antarctica and north Greenland supported trees.
    "The model ... [to] show cooler tropics and warmer poles ... [as happened in the Pliocene is] consistent with carbon dioxide as a cause" [p.132]. At that time "[a]tmospheric concentrations of CO2 ranged from 360 to 400 parts per million (ppm). ... Today's concentrations are at 382 ppm, and rising at 2 ppm annually" [p.133].
    "If emissions go on rising as they currently are, global temperatures could shoot past three degrees as early as 2050" [p.134].
    "The 'carbon cycle feedback' [reported by Peter Cox and his Hadley Centre team] ... would potentially leave human beings as powerless bystanders in a devastating global-warming scenario. ... [T]he main furnace of this positive feedback would burn ... in the remote heart of South America, beginning with the near total collapse of the Amazonian rain forest. ... [A] three-degree rise in global temperature ... effectively reverses the carbon cycle" [pp.138-139]. With this Hadley model, global warming by 2100 would rise "from 4° C to 5.5° C " [p.139].
    "With a three-degree increase, the American Midwest and the Amazon Basin — today the source of 20 percent of Earth's fresh water — will begin to decay into arid, uninhabitable waste." Additional changes include: increased wildfires, increased hurricanes, storm surges (that will threaten NYC, London, and other cities), thriving vector-borne tropical diseases, and decreasing grain yields (at temperatures over 30° C.

  4. 4° C (7° F) Global sea level will be "half a meter or more above current levels" [p.186], encroaching into Alexandria and the Nile Delta (Egypt), a third of Bangladesh (Meghna Delta), Boston, Venice: "Low-lying and deltaic cities from Mubai to Shanghai" [p.187]
    The demise of the West Antarctica Ice Sheet would be followed by "[i]ts much large neighbor, the East Antarctic Ice Sheet, [which] is four kilometers thick in parts and holds enough water to raise global sea levels by more than 50 meters"[p.192] !!!!! This temperature increase puts us at even greater hazard of the 'carbon cycle feedback' noted above.

  5. 5° C (9° F) "With 5 degrees of global warming, an entirely new planet is coming into being — one largely unrecognizable from the one we know today" [p.215].
    Deep-ocean methane outgassing may be provoked by the rising ocean temperatures, adding to the greenhouse gasses and the resulting warming.
    "A drastic reduction in human population is unambiguously the most likely outcome of a rise in global temperatures toward five degrees — what James Lovelock unhappily terms 'the cull' [p.236].

  6. 6° C (11° F). "[H]umanity's survival, even as a species, could be threatened by the ultimate apocalypse &mdah; six degrees of global warming" [p.237].

Maximum CO2 targets for various heating scenarios [p. 279; data for the last column from throughout the book]:

350 ppm One degree Not avoidable: in 2009 we have
passed this, being at 380 ppm.
Most coral reefs die. Many mountain glaciers are lost.
400 ppm Two degrees. Reduce global emissions after
peaking no later than 2015.
Populations of cities throughout Peru, Ecuador, and Bolivia lose their mountain-glacier runoff; they become climate refugees.
450 ppm Three degrees.
Probable threshold for carbon-cycle feedback.
Reduce global emissions after
peaking no later than 2030.
Amazon rainforest have collapsed.
Greenland's ice sheet disappears.
Desertification across the Midwestern USA and southern Africa.
550 ppm Four degrees.
Probable threshold for
Siberian methane feedback.
Reduce global emissions after
peaking no later than 2050.
Global sea level has risen by at least half a meter (a foot and a half).
Loss of coastal (particularly deltaic) cities and delta croplands worldwide.
West Antarctica Ice Sheet has melted.
The larger East Antarctica Ice Sheet is melting.
650 ppm Five degrees. Allow constantly rising
global emissions.
Possible threshold for deep-ocean methane outgassing.
Drastic reduction in human population: James Lovelock's 'cull'.
800 ppm Six degrees. Allow very high and rising
global emissions.
Elimination of a significant number of species.
Population crash of Homo Sapiens.

Links and References.

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