Climate Change

Tipping Points – Climate Change

“We can’t muster the force of nations to really begin fundamental changes in their energy systems, their construction, their lifestyle patterns, without a profound understanding of the urgency of the situation. We’ve got to act now.” – Wesley Clark, Supreme Allied Commander of NATO, 1996-1999, Global Observatory: Climate Change is a Global Security Threat, Climate Change will affect all levels of society.

“If we don’t take action now, every day, every year that goes by, the options for dealing with the effects of climate change and the effects of energy security become much much more expensive, and in fact some of the options completely go away over the next ten to twenty years; if we don’t start taking some prudent actions now.” – Vice Admiral Dennis McGinn; Climate Patriots: A Military Perspective on Energy, Climate Change and National Security.

Earth’s precarious ‘Greenhouse Effect’ position in the Habitable Zone:

The Habitable Zone

The Habitable Zone: To be habitable, a planet the size of Earth should be within certain distances from its Sun, in order for liquid water to exist on its surface, for which temperatures must be between freezing point (0° C) and boiling point (100° C) of water.

In the Wikipedia image, the dark green zone indicates that a planet the size of Earth could possess liquid water, which is essential since carbon compounds dissolved in water form the basis of all earthly life, so watery planets are good candidates to support similar carbon-based biochemistries.

If a planet is too far away from the star that heats it, water will freeze. The habitable zone can be extended (light green color) for larger terrestrial planets that could hold on to thicker atmospheres which could theoretically provide sufficient warming and pressure to maintain water at a greater distance from the parent star.

A planet closer to its star than the inner edge of the habitable zone will be too hot. Any water present will boil away or be lost into space entirely. Rising temperatures caused by greenhouse gases could lead to a moist greenhouse with similar results.

The distance between Earth and the Sun is one astronomical unit (1 AU). Mars is often said to have an average distance from the Sun of 1.52 AU. A recent study led by Ravi Kopparapu at Penn State mentions that early Mars was warm enough for liquid water to flow on its surface. However, the present-day solar flux at Mars distance is 0.43 times that of Earth. Therefore, the solar flux received by Mars at 3.8 Gyr was 0.75 × 0.43 = 0.32 times that of Earth. The corresponding outer habitable zone limit today, then, would be about 1.77 AU, i.e. just a bit too far away from the Sun to sustain water in liquid form. Venus, on the other hand, is too close to the Sun.

Kopparapu calculates that the Solar System’s habitable zone lies between 0.99 AU (92 million mi, 148 million km) and 1.70 AU (158 million mi, 254 million km) from the Sun. In other words, Earth is on the edge of runaway warming.

Kopparapu et al. New calculations show that Earth is positioned on the edge of the habitable zone (green-shaded region), boundaries of which are determined by the moist-greenhouse (inner edge, higher flux values) and maximum greenhouse (outer edge, lower flux values)

Kopparapu et al. New calculations show that Earth is positioned on the edge of the habitable zone (green-shaded region), boundaries of which are determined by the moist-greenhouse (inner edge, higher flux values) and maximum greenhouse (outer edge, lower flux values)

Kopparapu says that if current IPCC temperature projections of a 4 degrees K (or Celsius) increase by the end of this century are correct, our descendants could start seeing the signatures of a moist greenhouse by 2100.

Kopparapu argues that once the atmosphere makes the transition to a moist greenhouse, not only are the ozone layers and ice caps destroyed, but the oceans would begin evaporating into the atmosphere’s upper stratosphere, resulting in the ‘greenhouse effect’.

“The rate of change is happening at 300 times faster than any other extinction time in earth history, except that of the Asteroidal impact. [On feedback loops] The distinction between just a feedback process and a runaway feedback process is very, very important indeed. You can have feedback that slowly increases, if you like, the risk and puts the temperature up a bit higher. Runaway feedback says the system responds so much to an increase in temperature that it becomes faster in the way it changes the climate with rising temperature. So the hotter it gets, the faster it gets hotter, and the hotter it gets, the faster it gets hotter faster, until you move into a process that’s completely uncontrollable. And instead of coming up to a new equilibrium temperature that may be a bit high, it goes on going up faster and faster until something runs out—there’s no more methane to release or we’ve run out of forests to burn or something …“The danger of moving into a runaway climate change scenario is now clear and is beginning to be quantified in the last few months. It’s probably the greatest threat that we face as a planet.” (from 11:15ff.) – Artic Methane: Why the Sea Ice Matters.

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Venus and the Greenhouse Effect:

In Venus’ runaway greenhouse effect a warning for Earth, Sam Carana explains how the greenhouse effect affected Venus:

Venus was transformed from a haven for water to a fiery hell by a runaway greenhouse effect, concludes the European Space Agency (ESA), after studying data from the Venus Express, which has been orbiting Venus since April 2006.

Venus today is a hellish place with surface temperatures of over 400°C (752°Fahrenheit), winds blowing at speeds of over 100 m/s (224 mph) and pressure a hundred times that on Earth, a pressure equivalent, on Earth, to being one km (0.62 miles) under the sea.

Hakan Svedhem, ESA scientist and lead author of one of eight studies published on Wednesday in the British journal Nature, says that Earth and Venus have nearly the same mass, size and density, and have about the same amount of carbon dioxide. In the past, Venus was much more Earth-like and was partially covered with water, like oceans, the ESA scientists believe.

How could a world so similar to Earth have turned into such a noxious and inhospitable place? The answer is planetary warming. At some point, atmospheric carbon triggered a runaway warming on Venus that boiled away the oceans. As water vapour is a greenhouse gas, this further trapped solar heat, causing the planet to heat up even more. So, more surface water evaporated, and eventually dissipated into space. It was a “positive feedback” — a vicious circle of self-reinforcing warming which slowly desiccated the planet.

“Eventually the oceans began to boil”, said David Grinspoon, a Venus Express interdisciplinary scientist from the Denver Museum of Nature and Science, Colorado, USA. “You wound up with what we call a runaway greenhouse effect”, Hakan Svedhem says. Venus Express found hydrogen and oxygen ions escaping in a two to one ratio, meaning that water vapour in the atmosphere the little that is left of what they believe were once oceans is still disappearing.

While most of Earth’s carbon store remained locked up in the soil, rocks and oceans, on Venus it went into the atmosphere, resulting in Venus’ atmosphere now consisting of about 95% carbon dioxide.

“Earth is moving along the curve that connects it to Venus”, warns Dmitry Titov, science coordinator of the Venus Express mission.

Sam Carana: Three Kinds of Warming

Large-scale climate change assessments do not include consideration of (A) aggravating Tipping Points (Positive Feedback loops) or (B) mitigating Collapse of Industrial Civilization (Negative Feedback loops):

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Tipping Points to the Greenhouse Effect:

In Tipping Points; Aaron Franklin details how precarious Earth’s position in the Habitable zone is, and how crossing various tipping points, shall push it way over the tipping zone, with no return.

Earths current vulnerable Carbon stores amount to 7000 billion tons of carbon:

  • Carbon in the Arctic: 4450 Gton
    • ESAS: 500 Gton C organic; 1000 Gton C hydrate; 700 Gton C free methane; Total: 2200 Gton C
    • Other submarine arctic permafrost: 2200/0.8 = 2750 Gton C
    • Other Land permafrost = 1,700 Gt, which brings the total to 4450 Gton C
    • A large part of this is vulnerable to being lost rapidly into the Ocean/Atmosphere system if the Arctic defrosts, polar ocean warms, heavy rainfalls hit the Tundras.
  • Carbon in soils and Living Biomass: 2500 Gton
    • Total organic C in soil and living biomass is approx: 1000 Gton C living + 1500 Gton soil, amounting to a total of 2500Gton C
    • A large part of this is vulnerable to being lost rapidly into the Ocean/Atmosphere system if the Arctic defrosts, Global weather systems change, Rainforests and/or peat deposits burn, desertification and/or heavy rainfalls hit the Tropical, Temperate, Boreal forests.
    • So that’s the vulnerable surface Carbon stores. Total about 7000 billion tons of carbon, which does not include the carbon in deep sea clathrates.
  • Carbon in Deep sea Clathrates: 5,000-78,000 Gton
    • Estimates range from 5000 Gton C to 78000 Gton C
    • A large part of this is vulnerable to being lost into the Ocean/Atmosphere system if the oceans warm a few degrees, reaching the bottom in a few hundred to a few thousand years, causing the stability to be lost.

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Radiative Forcing Components:

Sam Carana: Radiative Forcing Components

This chart showing the present day situation, the effect of an extra 4.5 Gton C methane in the atmosphere, and the tipping point line for “super-greenhouse/Anoxic ocean” mass extinction events like the end Permian 252 million years ago, and the more recent PETM 56 million years ago. About 20 of those we know about in earths history.

However, the earth is not only confronted by one of the above tipping points, but all of them in a very short space of time, affecting each other in repeated positive feedback loops (threat multipliers) creating the perfect Eco-Geospheric beartrap planetary environmental storm.

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Tipping Elements (Positive Feedback Loops) to Earth’s Climate System.

Climate Change Tipping Point Feedback Loops

Potential future tipping elements in the climate system, overlain on global human populations density, as identified by Lenton et al. (2008)[T. M. Lenton et al., Tipping Elements in the Earth’s Climate System. Proceedings of the National Academy of Science 105, 1786 (2008).]

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Consequences of Major Tipping Points in the Earth’s Climate System:

The Report: Major Tipping Points in the Earths Climate System and Consequences for the Insurance Sector [Lenton Tim (Nov 2009): Major Tipping Points in the Earth’s Climate System and Consequence for the Insurance Sector; UEA/Tyndall Center, WWF & Allianz], was commissioned jointly by Allianz, a leading global financial service provider, and WWF, a leading global environmental NGO; and was prepared by Tyndall Center for Climate Change Research and Andlug Consulting.

The phrase ‘tipping point’ [‘Tipping point’ – the critical point (in forcing and a feature of the system) at which a transition is triggered for a given ‘tipping element’] captures the intuitive notion that “a small change can make a big difference” for some systems. The term ‘tipping element’ [‘Tipping element’ – a component of the Earth system that can be switched under particular conditions into a qualitatively different state by a small perturbation] has been introduced to describe those large-scale components of the Earth system that could be forced past a ‘tipping point’ and would then undergo a transition to a quite different state.

This definition includes cases where the transition is faster than the forcing causing it (also known as ‘abrupt’ or ‘rapid’ climate change) and cases where it is slower. It includes transitions that are reversible (where reversing the forcing will cause recovery at the same point it caused collapse) and those that exhibit some irreversibility (where the forcing has to be reduced further to trigger recovery). It also includes transitions that begin immediately after passing the tipping point and those that occur much later (offering a challenge for detection).

In some cases, passing the tipping point is barely perceptible but it still makes a qualitative impact in the future. These cases can be thought of as analogous to a train passing the points on a railway track – a small alteration can cause the trajectory of a system to diverge smoothly but significantly from the course it would otherwise have taken.

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Artic Sea Ice:

Observed changes in sea ice cover are more rapid than in all IPCC Assessment Report 4 AR4 model projections and the Arctic could already be committed to becoming largely ice-free each summer, within the next few decades.

What are the key concerns and impacts?

Amplified global warming – as Arctic ice melts this exposes a much darker ocean surface, leading to more sunlight being absorbed and hence accelerated ice melt (the ice-albedo feedback).

Ecosystem change – effects on arctic ecosystems and species including the iconic polar bear.

News Articles: Warm Atlantic water is defrosting the Arctic as it shoots through the Fram Strait (Science, January 2011). This breakdown of the thermohaline conveyor belt is happening in the Antarctic as well – Daily Kos. | Aaron Franklin (16 March 2013): Tipping Points; Artic News | Houser Gary (29 Jan 2013): The Tragic Failure of the Scientific community to Issue Adequate Warning re: The Arctic Tipping Point Emergency: The tremendous danger with this situation is that by the time any kind of “absolute proof” is gathered, it will very likely be too late to stop the conditions bringing on the dreaded runaway reaction; Arctic News | Carana Sam (17 Jan 2013): Accelerated Arctic Warming; Arctic News |

Arctic Sea Ice

Combined Sea Level Rise (SLR) from Greenland and West Antarctic Ice Sheets and continental ice caps:

IPCC (2007) chose not to include the uncertain contribution of changing mass of polar ice sheets in their projections of future sea level rise. As such, a ‘No Tipping’ scenario for global SLR from IPCC gives global SLR at around 0.15 m by 2050.

There is a convergence on minimum global sea level change being of the order of 75 cm in 2100 and absolute maximum being of the order 2 m.

On the basis of this, a ‘Tipping’ Scenario of around 0.5 m of global sea level rise by 2050 is a reasonable starting assumption.

The main impact associated with melting of the Greenland Ice Sheet (GIS), West Antarctic Ice Sheets (WAIS) and small continental ice caps, is sea level rise.

Greenland Ice Sheet (GIS):

The GIS is currently losing mass (i.e. water) at an accelerating rate. It will be committed to irreversible meltdown if the surface mass balance goes negative (i.e. mass of annual snow fall < mass of annual surface melt).

Whilst the time-scale for the GIS to melt completely is at least 300 years, because it contains up to 7 m of global sea level rise, its contribution to sea level rise over the whole of this time-scale means that it can still have a significant impact on societies this century.

What are the key concerns and impacts?

Sea level rise – depending on the speed of decay, the GIS could contribute up to 16.5–53.8 cm to global sea level rise this century (19).

Regionally increased sea level rise – as water added to the ocean takes time to be globally distributed this leads to sea level rise that is larger than the global average in some regions. Here, the greatest initial sea level rises are predicted down the North Eastern seaboard of the USA (21) affecting a number of US port megacities including Baltimore, Boston, New York, Philadelphia, and Providence.

Research Articles: Romm Joe (10 Mar 2011): JPL Bombshell: Polar ice sheet mass loss is speeding up, on pace for 1 foot sea level rise by 2050; Climate Progress; Romm Joe (24 Oct 2011): Greenland Ice Sheet “Could Undergo a Self-Amplifying Cycle of Melting and Warming .. Difficult to Halt,” Scientists Find; Climate Progress; Freedman Andrew (1 July 2012): Greenland Ice Sheet Melt Nearing Critical ‘Tipping Point’; Climate Central and Climate Progress; Romm Joe (30 Nov 2012): Science Stunner: Greenland Ice Melt Up Nearly Five-Fold Since Mid-1990s, Antartica’s Ice Loss up 50% in Past Decade; Climate Progress; Romm Joe (19 July 2013): Like Butter: Study explains Surprising Acceleration of Greenland’s Inland Ice; Climate Progress.

West Antartic Ice Sheet (WAIS):

Recent observations suggest that the WAIS is losing mass and contributing to global sea level rise at a rate that has increased since the early 1990s.

The WAIS is thought to be less sensitive to warming than the GIS but there is greater uncertainty about this. Unlike GIS, in the case of WAIS it is a warming ocean rather than a warming atmosphere that may be the control that forces the WAIS past a tipping point. Recent expert elicitation gives somewhat higher probabilities of WAIS disintegration under medium (2–4 °C above 1980–1999) and high (>4 °C) global warming than in an earlier survey.

What are the key concerns and impacts?

Sea level rise – a worst case scenario is WAIS collapse within 300 years with a total of ~5 m of global sea level rise (i.e. >1 m per century).

Other recent estimates give the maximum potential contribution of the whole of Antarctica to sea level rise this century as 12.8–61.9 cm (19).

Research Articles: Romm Joe (13 Aug 2009): Large Antarctic glacier thinning 4 times faster than it was 10 years ago: ‘Nothing in the natural world is lost at an accelerating exponential rate like this glacier”; Climate Progress | Romm Joe (10 Mar 2011): JPL Bombshell: Polar ice sheet mass loss is speeding up, on pace for 1 foot sea level rise by 2050; Climate Progress | Romm Joe (30 Nov 2012): Science Stunner: Greenland Ice Melt Up Nearly Five-Fold Since Mid-1990s, Antartica’s Ice Loss up 50% in Past Decade; Climate Progress | Nature Geoscience (April 2013): Summer ice melt in Antarctica is at its highest level in a thousand years – Reuters: Summer ice in the Antarctic is melting 10 times quicker than it was 600 years ago, with the most rapid melt occurring in the last 50 years – Nature.

Continental Ice Caps:

Smaller continental ice caps are already melting and much of the ice contained in them globally could be lost this century.

Such ice caps are generally not considered tipping elements because individually they are too small and there is no identifiable large-scale tipping threshold that results in coherent mass melting.

An exception may, however, be glaciers of the Himalayas (the Hindu-Kush-HimalayaTibetan glaciers or ‘HKHT’ for short) (9). HKHT glaciers represent the largest mass of ice outside of Antarctica and Greenland. No tipping point threshold has as yet been identified for the region as a whole but IPCC AR4 suggests that much of the HKHT glaciers could melt within this century.

What are the key concerns and impacts?

Reduction in river flow – the HKHT glaciers feed rivers in India, China and elsewhere. A dwindling contribution to river flows will have major implications for populations depending on those rivers and this may be aggravated by other shifts such as in the Indian Summer Monsoon (ISM – see further down).

In India alone, melt-water from Himalayan glaciers and snowfields currently supplies up to 85% of the dry season flow and initial modelling suggests that this could be reduced to about 30% of its current contribution over the next 50 years.

News Article: Cracking of glaciers accelerates in the presence of increased carbon dioxide (Journal of Physics D: Applied Physics, October 2012)

Permafrost (and its carbon stores):

In simple terms, permafrost is soil and/or subsoil that is permanently frozen throughout the year (and has often been frozen for thousands of years). Observations suggest that permafrost is melting rapidly in some regions, particularly parts of Siberia, and future projections suggest the area of continuous permafrost could be reduced to as little as 1.0 million km2 by the year 2100, which would represent almost total loss (30).

An abrupt change in the rate of permafrost shrinkage has been forecast around now, and large areas such as Alaska are projected to undergo the transition from frozen to unfrozen soil in the space of ~50 years (30).

Because there is no clear mechanism for a large area to reach a melting threshold nearly simultaneously, melting of most of the world’s permafrost is probably not a tipping element. However, frozen loess (windblown dust) of Eastern Siberia is an exception (31) and could release 2.0–2.8 GtC yr-1 (7.3–10.3 Gt CO2e yr-1) – mostly as CO2 but with some methane – over about a century, removing ~75% of the initial carbon stock. However, to pass this tipping point requires an estimated >9 °C of surface warming, which would only be reached this century under the most extreme scenarios.

What are the key concerns and impacts?

Amplified global warming – In addition to problems of subsidence of structures such as buildings and pipelines, the key concern is that when permafrost melts, the large quantities of carbon it contains are returned back into the atmosphere as methane and carbon dioxide. In addition, frozen compounds called clathrates under the permafrost may be destabilized and result in the release of methane and carbon dioxide.

There have been claims that these responses and the associated release of GHGs will lead to ‘runaway’ global warming as a positive feedback mechanism. These claims are, however, grossly exaggerated and amplification of global temperature change is modest compared to other well known climate feedbacks.

Research Reports: Methane hydrates are bubbling out the Arctic Ocean (Science, March 2010) | Siberian methane vents have increased in size from less than a meter across in the summer of 2010 to about a kilometre across in 2011 (Tellus, February 2011) | Methane is being released from the Antarctic, too (Nature, August 2012) | Exposure to sunlight increases bacterial conversion of exposed soil carbon, thus accelerating thawing of the permafrost (Proceedings of the National Academy of Sciences, February 2013) | Franklin Aaron (12 Mar 2013): The worst-case and — unfortunately — looking almost certain to happen scenario; Arctic News |

Boreal Forests:

Widespread die-back of the southern edges of boreal forests has been predicted in at least one model when regional temperatures reach around 7 °C above present, corresponding to around 3 °C global warming.

What are the key concerns and impacts?

Forest fires, productivity and forest pests & diseases – Under such circumstances, boreal forest would be replaced by large areas of open woodlands or grasslands that support increased fire frequency.

Warning signs of ecosystem changes are already apparent in Western Canada where an infestation of mountain pine beetle has caused widespread tree mortality, and fire frequencies have been increasing.

Research Articles: Peat in the world’s boreal forests is decomposing at an astonishing rate (Nature Communications, November 2011) | Russian forest and bog fires are growing (NASA, August 2012).

Atlantic thermohaline circulation (THC):

Sometimes called the ‘ocean conveyor belt’ the thermohaline circulation (THC) has a profound effect on climate. Collapse of the THC is the archetypal example of a tipping element with the potential tipping point being a shut-off of deep convection and North Atlantic Deep Water (NADW) formation in the Labrador Sea.

Best estimates are that reaching the threshold for total THC collapse requires at least 3–5 °C warming within this century. IPCC AR4 views the threshold as more distant and transition of the THC would probably take the order of another 100 years to complete.

However, whilst total collapse of the THC may be one of the more distant tipping points, a weakening of the THC this century is robustly predicted by IPCC AR4 models and will have similar (though smaller) effects as a total collapse.

What are the key concerns and impacts?

Complex and combined impacts on other climate variables and tipping elements – THC collapse would tend to cool the North Atlantic and warm the Southern Ocean, causing a Southward shift of the Inter-Tropical Convergence Zone (ITCZ) in the atmosphere.

It would raise sea level dynamically by ~1 m in parts of the North Atlantic, including ~0.5 m along the Atlantic coasts of North America and Europe, and reduce sea level in the Southern Ocean.

THC collapse would also have implications for a number of hydrological tipping elements (discussed in Section 2.4).

News article: The Beauford Gyre apparently has reversed course (U.S. National Snow and Ice Data Center, October 2012)

El Niño southern oscillation (ENSO):

The El Niño southern oscillation (ENSO) is the most significant natural mode of coupled ocean-atmosphere variability in the climate system. Changes in ENSO and a corresponding change in Pacific temperatures occurred around 1976. Prior to 1976 there were low amplitude El Niño events with 2–3 year frequency, subsequently there have been larger amplitude events with 4–5 year frequency.

The first coupled model studies predicted a shift from current ENSO variability to more persistent or frequent El Niño conditions. However, in response to a stabilized 3–6 °C warmer climate, the most realistic models simulate increased El Niño amplitude (with no change in frequency). Increase in El Niño amplitude is consistent with the recent observational record. Paleo-data also indicate different ENSO regimes under different climates of the past.

What are the key concerns and impacts?

Complex and combined impacts on other climate variables and tipping elements – higher amplitude El Niño events would have impacts in many regions and on other tipping elements.

Amazonian Rainforest:

The Amazon rainforest is well known as a rich cradle of biodiversity. However, it could be threatened by coupled changes in the water cycle and vegetation involving:

* An increase in drought anomalies (such as that in 2005), leading to
* Amazon rainforest die-back.

The Amazon region is sensitive to changes in both ENSO and the THC, suffering drying during El Niño events, and when the North Atlantic is unusually warm. In 2005, large sections of the western Amazon basin experienced severe drought resulting in significant impacts in a number of regions. The 2005 drought has been linked to an anomalously warm tropical North Atlantic. Recent studies suggest that droughts similar to that of 2005 will increase in frequency in future projections assuming increasing greenhouse gas forcing and decreasing sulphate aerosol (cooling) forcing in the North Atlantic. The 2005 drought was an approximately 1-in-20-yr event, but a 2005-like drought in Amazonia is forecast to become a 1-in-2-yr event by 2025 (at 450 ppmv CO2e) and a 9-in-10-yr event by 2060 (at ~600 ppmv CO2e) with the threshold depending on the rate of increase of CO2 (3).

The trees of the Amazon rainforest help maintain rainfall by recycling water to the atmosphere (a positive feedback). They can tolerate short droughts by using their deep roots to access soil water. However, if droughts become more frequent and the dry season continues to get longer, a number of studies have forecast that the forest could reach a threshold beyond which widespread die-back occurs.

Potentially up to ~70% of the Amazon rainforest could be lost due to climate changedriven die-back by late this century (36). Widespread die-back would occur over a few decades and would be effectively irreversible on any politically meaningful time-scale.

The most recent work (37) suggests that the Amazon rainforest could be committed to long-term die-back long before any response is observable, finding, for example, that the risk of significant loss of forest cover in Amazonia rises rapidly for a global mean temperature rise above 2 °C.

What are the key concerns and impacts?

* Drought impacts – with effects on wildfire, hydroelectric generation, agricultural production and related service industries, river navigation and livelihoods more generally.

* Die-back impacts – many, including biodiversity loss, decreased rainfall, effect on livelihoods, and creation of a significant carbon source that amplifies global warming.

News Article: Drought in the Amazon triggered the release of more carbon than the United States in 2010 (Science, February 2011)

West African Monsoon (WAM) and the Sahel:

The most pronounced hydrological change in the observed climate record was the recent (1960s to 1980s) drought in the Sahel. Key drivers for this were the weakening of the Atlantic North South sea surface temperature (SST) and the weakening of the THC.

New results show that more severe, earlier intervals of drought in West Africa were linked to weakening of the THC (44, 45). Recent simulations suggest a tipping point or threshold for THC weakening below which the subsurface North Brazil Current reverses, abrupt warming occurs in the Gulf of Guinea, and the West African Monsoon (WAM) shifts such that it does not seasonally reach the Sahel, and there is an increase in rainfall in the Gulf of Guinea and coastal regions (44).

However, in a future simulation with one of the IPCC AR4 models, shift of the WAM unexpectedly leads to wetting and greening of the Sahel and parts of the Sahara back toward conditions last seen around 6000 years ago. Such transitions can potentially occur within years and their reversibility (or irreversibility) is currently unresolved.

What are the key concerns and impacts?

Uncertain outcome – there is a recent history of failed efforts to make multidecadal forecasts of rainfall in the Sahel. Currently it is unclear whether the Sahel will experience wetting or drying in future. In the best-case scenario, tipping the WAM may provide a net benefit by changing regional atmospheric circulation in a way that wets large parts of the Sahel.

Indian Summer Monsoon (ISM) and other Monsoons in South East Asia:

The arrival of Indian Summer Monsoon (ISM) rainfall is, generally, remarkably reliable, occurring annually in June or July (depending on location). Greenhouse warming would on its own be expected to strengthen the monsoonal circulation, however, the observational record shows declines in ISM rainfall which have been linked to an ‘atmospheric brown cloud’ (ABC) haze created by a mixture of black carbon (soot) and sulphate aerosols.

This ABC haze tends to weaken the monsoonal circulation and, in simple models, there is a tipping point for the regional planetary albedo (reflectivity) over the continent which, if exceeded, causes the ISM to collapse altogether.

Regional black carbon (soot) emissions from China and India have increased significantly in recent decades. The most pronounced regional hotspot of black carbon emissions is in North Eastern China, which may be linked to a distinct southward shift of monsoonal precipitation in China.

What are the key concerns and impacts?

Interference with monsoon cycle and drought frequency – owing to its reliability, agriculture, livelihoods and economy have grown to depend upon the ISM. Increasing aerosol forcing of the system could weaken the monsoon, but if then removed, greenhouse warming could trigger a stronger monsoon, producing a ‘roller coaster ride’ for many millions of people as, if switches occur, they could happen from one year to the next.

South Western North America (SWNA):

On decadal and longer time-scales, drought in Western North America (WNA) is linked to periods of increased sea surface temperatures (SSTs) in the North Atlantic, which have been linked to strengthening of the THC (50). Recent drought could also have been contributed to by the removal of aerosol forcing.

Aridity in South-western North America (SWNA) is robustly predicted to intensify and persist in future and a transition is probably already underway and will become well established in the coming years to decades, akin to perpetual drought conditions.

As such, levels of aridity seen in the 1950s multiyear drought or the 1930s Dust Bowl are predicted to become the new climatology by mid-century. Western North America (WNA) has already experienced increased winter air temperature, a declining snow pack (linked to more precipitation falling as rain instead of snow and earlier snow melt), and a shift to earlier run-off (increasing in spring, decreasing in summer), all of which have been attributed to anthropogenic (greenhouse gas and aerosol) forcing (51).

Increasing aridity in SWNA may still not qualify formally as a tipping element unless a threshold can be identified. However, evidence suggests that the changes are either imminent or already underway.

What are the key concerns and impacts?

Prolonged drought impacts – with impacts on wildfire probability and consequences for agriculture, water resources and water markets.

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How Insurance Corporations Can Send Effective Loud Economic Warning Signals to Society:

Acting on Early Warnings:

Recent work on the topic of climate tipping points and widespread media and policymaker response to it suggests that the first, general type of early warning is underway and, indeed, this report contributes to this. However, regardless of the accuracy of forecasts and warnings, getting to the point where action is taken on the basis of such early warnings (to at least mitigate their impacts) is arguably a much greater challenge.

The insurance sector could play a potentially valuable role here if it can enshrine the increased probability of an approaching tipping point in terms of greatly increased premiums or even the refusal to insure certain items in certain locations. Such changes would send an economic signal to society at large that may be more effective as an early warning than any number of scientific reports or newspaper headlines.

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Climate, Food Security and Conflict:

Spratt David (11 July 2013): Arctic melt hits food security in bitter taste of life on a hotter planet; Arctic News; report:

Combination of Wet Summer and Autumn and Cold winter and spring have wrecked farmers schedules. Less growth in a dull 2012 summer – combined with water-logged crops and pastures in autumn – reduced yields, and some crops had to be left in the ground.

The spring 2013 growing season, including for apples and pears as well as pasture, started up to six weeks late due to the cold, dull conditions. And waterlogged fields meant that across Ireland cattle were still being kept in their winter sheds in the first week of June, ostensibly a summer month. The consequences – whilst mild compared to climate-change impacts on vulnerable communities in the developing world from the African Sahel to Asia’s changing monsoons – show how easily the security of food production can be disrupted:

WHEAT: In the UK, a wet autumn, hard winter and cold spring has resulted in one of the smallest wheat harvests in a generation, 30% below normal. Britain, generality the third biggest wheat grower in the EU, will be a net importer for the first time in 11 years. Charlotte Garbutt, a senior analyst at the industry-financed Agriculture and Horticulture Development Board says: “Normally we export around 2.5m tonnes of wheat but this year we expect to have to import 2.5m tonnes.” The latest analysis from the UK Department for the Environment, Food and Rural Affairs says total farming income decreased by £737million in 2012 to £4.7bn, as farmers faced both crop losses and higher feed costs.

STOCK LOSSES: Late snowstorms across England, Sotland, Wales and Ireland March 2013, with drifts of up to 5 metres, killed an estimated 40,000 newborn lambs. In Ireland’s west, one-quarter more animals died in the first three months of 2013 compared to 2012, with some vets trained to look for suicidal behaviour in farmers.

POTATO SHORTAGE: A wet autumn and poor season in 2012 prevented many crops being harvested in Ireland. Supermarket price-squeezing has also driven some farmers out of the industry, together resulting in reduced yields of at least 30 per cent in 2012. By spring 2013, potato prices had almost tripled in many parts of Ireland, with supplies exhausted and a reliance on imports from central Europe.

Limavady farmer, James Wray, told UTV News that said the changing weather in recent weeks had forced the price up: “This year has been a terrible growing season with loads of crops lost and loads of crops not harvested and any crops that have been harvested have produced low yields. There just isn’t any potatoes left in the country, there are no farmers with potatoes left, so whatever potatoes are about, are very, very expensive. If you go to any of the major supermarkets most of their potatoes are coming in from Europe just to bridge the gap.”

Potato shortages have a particular cultural resonance in Ireland as a consequence of the Irish potato famine of the mid-nineteenth century, which killed a million people and forced another million to emigrate.

FEED SHORTAGE: In the last week of May (the final week of spring), farmers in Ireland’s west were queuing for hay and silage imports from England, France and Netherland as their winter feed became exhausted and a lack of pasture growth in spring due to cold and overcast conditions, and wet fields, prevented cattle from being moved from their winter sheds. More than 13000 tonnes of feed was imported, but even so farmer Enda Stenson said local farmers “have neither money nor fodder”. Many had sold down their herds to be able to buy feed for the remainder.

BEES IN TROUBLE: Bad weather and disease is also threatening honey production, with some beekeepers expecting to produce no honey as bees have been unable to mate and hives are decimated. And bees play a crucial role in pollinating many crops.

Jim Donohoe, of the Federation of Irish Beekeepers’ Associations, told the Irish Independent that the problem was weather related: “We’ve had bad summers before, but because of the wind, rain and lack of sunshine, we’ve had serious problems with colonies wanting to swarm, but the queens being unable to mate with drones which refused to fly because there wasn’t calm conditions. This year, we had a delayed winter where bees couldn’t fly. The flowers were delayed coming out, and that crucial period meant bees died from old age. All of this combines to about 50pc of colonies being lost. If we don’t get milder weather, the losses will be closer to 75pc.

These stories may seem trivial compared to the devastating impact of climate change on global food security and prices, and their political consequences. Writing on Egypt’s new political turmoil, Nafeez Ahmed notes that: “Food price hikes have coincided with devastating climate change impacts in the form of extreme weather in key food-basket regions. Since 2010, we have seen droughts and heat-waves in the US, Russia, and China, leading to a dramatic fall in wheat yields, on which Egypt is heavily dependent. The subsequent doubling of global wheat prices – from $157/metric tonne in June 2010 to $326/metric tonne in February 2011 – directly affected millions of Egyptians, who already spend about 40% of their income on food. That helped trigger the events that led to the fall of Hosni Mubarak in 2011, but the same configuration of factors is worsening.”

And Lester Brown, head of the Earth Policy Institute in Washington, has warned that grain harvests are already shrinking as US, India and China come close to ‘peak water’. He says that 18 countries, together containing half the world’s people, are now over-pumping their underground water tables to the point – known as “peak water” – where they are not replenishing and where harvests are getting smaller each year.

Together these stories paint a compelling picture of the threat to food security from climate change, not just in the Middle East, Asia and Africa, but in the heart of the developed world too.

Global food supply is under stress as extreme weather becomes the new norm. Farmers may be inclined to respond to drought by overusing ground water, or by slashing and burning forest, in efforts to create more farmland. Such practices do not resolve the problems; instead, they tend to exacerbate the problems over time, making things progressively worse.

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Near Term Extinction (NTE): Climate Change, Scarcity, Conflict and Extinction:

“On our current emissions path, projected warming is catastrophic even in the unlikely event of a low climate sensitivity of 1.5 – 2.0°C.” Michael Schlesinger et al 2012.

Sam Carana writes in How to avoid mass-scale death, destruction and extinction:

The diagram below shows that there are many climatological feedbacks (ten of which are pictured) that make climate change worse. At the top, the diagram pictures vicious cycles that are responses by farmers that can add to make the situation even worse. Without effective action, the prospect is that climate change and crop failure combine to cause mass death and destruction, with extinction becoming the fourth development of global warming.

Sam Carana: Diagram of Doom and Responses

How can we avoid that such a scenario will eventuate? Obviously, once we are in the fourth development, i.e. mass-scale famine and extinction, it will be too late for action. Similarly, if the world moves into the third development, i.e. runaway global warming, it will be hard, if not impossible to reverse such a development. Even if we act now, it will be hard to reverse the second development, i.e. accelerated warming in the Arctic.

The most effective action will target causes rather than symptoms of these developments. (own emphasis)

Part 1. Since emissions are the cause of global warming, dramatic cuts in emissions should be included in the first part of the responses. In addition, action is needed to remove excess carbon dioxide from the atmosphere and oceans. Storing the carbon in the soil will also improve soil quality, as indicated by the long green arrow on the left.

Part 3. Methane management and further action is needed, e.g. to avoid that methane levels will rise further in the Arctic, which threatens to trigger further releases and escalate into runaway global warming. Measures to reduce methane can also benefit soil quality worldwide, as indicated by the long green arrow on the right.

Thus, the proposed action tackles the prospect of mass death and extinction by increasing soil fertility, as illustrated by the image below.

Carana’s scientific political correctness fails to address the consumption and population growth causes of emissions. Reducing population pressures on agriculture and reducing consumption by limiting citizens consumption to carrying capacity levels, will not only reduce emissions, but reduce other feedback loops aggravating agriculture, biodiversity loss, deforestation, etc.

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Methane Hydrate Time Bomb:

Sam Carana’s Methane Hydrates provides a layman terms overview: When ice sheets form, they overrun organic matter such as that found in lakes, tundra and ocean sediments, which is then cycled to methane under the anoxic conditions beneath the ice sheet. The methane could be released to the atmosphere if the ice sheet shrinks and exposes these old sedimentary basins.

An estimated 21,000 petagrams (1Pg equals 1015g) of organic carbon are buried beneath the Antarctic Ice Sheet, estimates a research team led by Jemma Wadham. The potential amount of methane hydrate and free methane gas beneath the Antarctic Ice Sheet could be up to 400 billion tonnes (that is, 400 Pg of carbon, or 400 Gt, see table below).

In the Arctic, the amounts of methane are equally vast. Shakhova et al. (2010) estimate the accumulated methane potential for the Eastern Siberian Arctic Shelf (ESAS, image 7. on the right) alone as follows: (i) organic carbon in permafrost of about 500 Gt; (ii) about 1000 Gt in hydrate deposits; (iii) about 700 Gt in free gas beneath the gas hydrate stability zone.

Shakhova et al. (2008) consider the release of up to 50 Gt of predicted amount of hydrate storage as highly possible for abrupt release at any time. By comparison, the total amount of methane currently in the atmosphere is about 5 Gt.

Methane’s potency as a greenhouse gas: Releases of methane into the atmosphere are very worrying, given methane’s high potency as a greenhouse gas. In the context of tipping points, which is most appropriate regarding methane releases in the Arctic, it makes sense to focus on a short time horizon, i.e. as short as a few years, rather than decades.

Based on the figures by Shindell et al. and using a horizon of 10 years, methane’s GWP is more than 130 times that of carbon dioxide. The danger is that a large abrupt methane release in the Arctic will trigger further local releases. This danger is particularly high the first few years after the methane enters the atmosphere, due to methane’s high initial warming potential, as further discussed in the next two chapters.

Methane’s Local Warming Potential: Methane releases from hydrates at the poles differ in a number of ways from the methane that is typically released elsewhere around the globe: After 5 years, a methane cloud 20% the size of its original abrupt release in the Arctic will still have more than 1000 times the warming potency locally that the same mass of CO2 has globally.

Abrupt release of methane from hydrates will initially be highly concentrated in one location. Other types of methane releases (e.g. from wetlands, livestock, bio-waste and burning of fuel) occur spread out over the world throughout the year, i.e. such releases are pretty much global and continuous to start with and can be more easily broken down by hydroxyl that is continuously produced around the world.

By contrast, much of the methane from an abrupt release in the Arctic Ocean will initially remain concentrated over the Arctic Ocean, which covers only 2.8% of the Earth’s surface. While the methane will eventually spread around the world, this will take time. Nesbit mentions that a major methane release in the high Arctic would take 15-40 years to spread to the South Pole.

Given the lack of hydroxyl in the Arctic atmosphere, it may well be possible that some 20% of the methane from an abrupt release over the Arctic Ocean still remains there after 5 years. Using a GWP for methane of 130 times that of carbon dioxide over a period of ten years would already lift methane’s LWP (local warming potential) over the Arctic to (130*100:2.8:5=) 929 over 10 ten years. For a shorter period, the Arctic LWP will be even higher. In conclusion, local concentration alone makes that a methane cloud still hanging over the Arctic five years after its release will have a huge LWP, i.e. well over 1000 times the potency locally that the same mass of carbon dioxide has globally.

Additionally, high temperature anomalies mean that methane releases at the poles will be felt more severely than elsewhere on Earth. These high temperature anomalies are the result of feedbacks such as albedo changes caused by melting. The danger is that large abrupt release of methane will contribute to high sea surface temperature in summer, mixed down to the seafloor during storms, to penetrate cracks and conduits in the permafrost, destabilizing the methane held in sediments and triggering subsequent methane releases, and this danger is particularly high in the shallow seas of the Arctic.

Sam Carana: Extreme Warming Events

Above image illustrates how this dangerous situation has developed in the Arctic, and what can be expected in future without action. The image pictures three kinds of warming (red lines) and their main causes:

Emissions by people cause global warming, with temperatures rising around the globe, including the Arctic. High levels of greenhouse gases in the Arctic, combined with the impact of aerosols such as soot, and rivers that end in shallow waters in the Arctic combine to cause high summer temperature peaks in the Arctic. In other words, global warming is amplified in the Arctic.

Accelerating Arctic warming is caused by at least ten feedback effects. Melting of snow and ice causes albedo changes, i.e. less sunlight gets reflected back into space and instead gets absorbed, causing further warming. Additionally, soot, dust and volatile organic compounds settle down on snow and ice, causing further albedo change.

Three of these feedbacks are pictured as gold lines:

Fires feedback: Accelerated warming in the Arctic is changing the Jet Stream, contributing to increased frequency and intensity of droughts and heatwaves.

Albedo feedback: Accelerated warming in the Arctic also speeds up the decline of ice and snow cover, further accelerating albedo change.

Methane feedback: Methane releases in the Arctic further add to the acceleration of warming in the Arctic, further contributing to weaken Arctic methane stores, in a vicious cycle that threatens to escalate into runaway global warming.

Runaway warming. Accelerating warming further weakens the capability of the seabed to hold the methane that is contained in the form of hydrates and free gas in sediments under the sea, in a vicious cycle that threatens to lead to runaway warming.

Runaway warming:

What would the impact be of abrupt release of 1Gt of methane in the Arctic, compared to the total global carbon dioxide emissions from fossil-fuel burning, cement manufacture, and gas flaring? Image 22. below gives a rather conservative impact, showing a rapid decline toward a small residual impact as carbon dioxide.

Sam Carana: 1GT of Methane Release

Above graph does not yet include the indirect effect of triggering further releases. This is especially a threat in the Arctic, given the large presence of methane in sediments, the accelerated warming already occurring in the Arctic, the little oxidation that takes place in the Arctic atmosphere, and the time it will take for abruptly released methane to spread away from the Arctic.

The additional warming that this will cause in the Arctic will make that the decline of sea ice and snow cover will take place even more dramatically than is already the case now. There will be a huge warming impact, due to the albedo change caused by decline of snow and ice combined with the warming impact of methane. This threatens to trigger further releases of methane in the Arctic, with their joint impact accumulating as illustrated in the image below.

Sam Carana: 1 Gt of Methane Release Comparison

Dramatic warming will first strike in the Arctic, but will soon spread, threatening to cause heatwaves and firestorms across North America and Siberia, adding additional soot and carbon dioxide in the atmosphere globally, as forests, peat bogs and tundras at higher latitudes burn, threatening to escalate in runaway global warming.

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Temperature rise:

Sam Carana: Three Types of Warming

The above image shows how global warming (blue line) is projected to eventuate based on NASA global temperature anomalies. Note that the rise is projected to be much steeper in the Arctic (latitudes 64 North to 90 North, pink line).

If runway warming will eventuate as described above, the world as a whole will gradually catch up with such a steep rise in a matter of years (white line).

Destruction and Extinction:

In the above projection, runaway global warming will catch up with Arctic warming by 2039, resulting in a global temperature increase of 10 degrees Celsius and rising. The heatwaves that will come with such a temperature rise will in itself be enough to cause crop losses at massive scale. Additionally, heatwaves at high latitudes will cause wildfires, e.g. in Siberia, which has a very high soil carbon content.

Sam Carana: Diagram of Doom

The heatwaves in Russia provide a gloomy preview of what could happen as temperatures rise at high latitudes. Firestorms in the peat-lands, tundras and forests in Siberia could release huge amounts of emissions, including soot, much of which could settle on the Himalayan plateau, darkening the ice and snow and resulting in more local heat absorption. Rapid melt of glaciers will cause flooding at first, followed by dramatic decreases in the flow of river water that up to a billion people now depend on for water supply and irrigation.

Taking no action risks extinction for many species, including humans, possibly within one human generation. With so much at stake, the cost of taking action is dwarfed by the price paid when no action is taken. The longer the delay in action, the larger the risk becomes and the more difficult, expensive and risky it will become to take measures to try and reduce the danger.

Scientists warning of Near-Term Extinction (NTE) in absence of inaction:

James Hansen, Adjunct Professor of Earth and Environmental Sciences at Columbia University’s Earth Institute: “Imagine a giant asteroid on a direct collision course with Earth. That is the equivalent of what we face now [with climate change], yet we dither.” – Why I must speak out about climate change TED.

Arctic Methane Emergency Group: Founding members Peter Wadhams, Professor of Ocean Physics, Cambridge; Stephen Salter, Emeritus Professor of Engineering Design, Edinburgh; and Brian Orr, former Principal Science Officer at the UK DoE.

Matter of Arctic Methane Alert Survival Letter to World Leaders

Methane Outbreak Alert: “Over the past three decades, snow cover has been reduced by 17-18% per decade and sea ice is declining fast because of human-induced global warming. Consequently, the albedo effect is collapsing in the Arctic. Albedo is the reflection of Sun’s radiation off the white ice and white snow surfaces. Unfortunately, when the albedo effect collapses, the dark sea and dark land mass absorb most of the Sun’s radiation. A collapsing albedo effect is ominously apocalyptic for the Arctic, and for the world. And, disturbingly, Arctic albedo is already in the collapsing stage. This will inevitably lead to ever more methane emissions and a vicious cycle of feedbacks leading to an extinction event, probably unstoppable. ..

AMEG 2012 Policy Brief: “AMEG’s conclusion is that there is now a planetary emergency. Only by grasping the nettle and intervening with great determination, as in a war effort, is there a chance of remedying the situation before it is too late. International collaboration to fight this common “enemy” of Arctic meltdown must bring all nations together, in the cause of our very survival.”

Malcolm Light (9 Feb 2012): Global Extinction within one Human Lifetime as a Result of a Spreading Atmospheric Arctic Methane Heat wave and Surface Firestorm; Arctic News

Goreau, PhD: Global Coral Reef Alliance, former Senior Scientific Affairs Officer at the United Nations Centre for Science and Technology for Development, in charge of Global Climate Change and Biodiversity issues, where he contributed to the original draft of the UN Framework Convention on Climate Change: “The long-term sea level that corresponds to current CO2 concentration is about 23 meters above today’s levels; and the temperatures will be 6 degrees C or more higher. These estimates are based on real long term climate records, not on models.” — Briefing to the United Nations Conference of the Parties in Copenhagen (COP15): What is the Right Target for CO2?: 350 PPM is a death sentence for Coral Reefs and Low-Lying Islands: The Safe level of CO2 for SIDS is around 260 parts per million footnote, via Wrong Kind of Green.

Scientists call for war on climate change, but who on Earth is listening?; David Spratt (8 Dec 2012); Climate Code Red

  • Dr Daniel Pauly; Professor and the project leader of the Sea Around Us Project at the Fisheries Centre at the University of British Columbia, Director of the Fisheries Centre (2003 – 2008), said it was time to prepare economy for a climate change ‘war’ – ABC.
  • Josep Canadell: Global Carbon Project: CSIRO Marine and Atmospheric Research – The Conversation.
  • World Bank said that 4 °Cs of warming will end the world as we know it.
  • United Nations Environment Programme Report on Tipping Point Policy Implications of Warming Permafrost.
  • Professor Matthew England, University of NSW told the ABC’s 7.30 Report that we need a global-scale effort akin to preparing for a war – ABC.
  • Corinne Le Quéré, director of the Tyndall Centre for Climate Change Research in Britain and professor at the University of East Anglia, says “We need a radical plan” – The Guardian.
  • Professor Andrew Weaver of the University of Victoria, Canada: “We are losing control of our ability to get a handle on the global warming problem” [Think Progress] and “The scientists have lost patience with our carefully constructed messages being lost in the political noise. And we are now prepared to stand up and say enough is enough” [The Guardian] and “Put bluntly, climate change commitments are incompatible with short- to medium-term economic growth (in other words, for 10–20 years). Moreover, work on adapting to climate change suggests that economic growth cannot be reconciled with the breadth and rate of impacts as the temperature rises towards 4 °C and beyond — a serious possibility if global apathy over stringent mitigation persists. Away from the microphone and despite claims of ‘green growth’, few if any scientists working on climate change would disagree with the broad thrust of this candid conclusion…. At the same time as climate change analyses are being subverted to reconcile them with the orthodoxy of economic growth, neoclassical economics has evidently failed to keep even its own house in order.” [Nature].
  • Guy McPherson, former Professor Emeritus of Natural Resources and Ecology & Evolutionary Biology: “The evidence for human extinction by 2030 is overwhelming” — The End: Walking Away from Apocalypse with Guy McPherson, by Adam Engel / May 3rd, 2013; and (at 20:18, 26:00 & 27:40) Environmental Point of No Return: A Discussion with Dr. Guy McPherson.); [Near-term Extinction] Climate Change Summary and Update.

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