An Existential Threat

This page explains that the myriad of changes we are causing Earth to undergo now pose a threat to the existence of civilisation.

Despite repeated warnings about climate change, civilisation has chosen not to be precautionary. Instead civilisation chooses to be reckless and hold climate science in contempt by endorsing politicians who fail to act, and to indulge in oil, coal and gas. And so our climate radically changes along with Earth’s land and ocean, on vast scales at extreme rates. Civilisation chooses indifference, leaving a nightmarish burden for young people.

Greta Thunberg’s speech at the World Economic Forum in Geneva, Jan 2019. The video looks dim but this was the only full version available.

Climate change is now an existential threat to civilisation, not only because of the global warming that has directly resulted from our emissions, but because of the ways Earth’s climate system has responded, and will continue to respond. These responses are known as feedbacks. Feedbacks act on different timescales, so some are fast and others are slow. They are also either negative feedbacks that reduce, or positive feedbacks that amplify. Our emissions have already set in play fast amplifying feedbacks in Earth’s climate system, and are now triggering additional further amplifying feedbacks associated with Earth’s ice sheets that may take the climate system past tipping points. These are points of no return, with consequences beyond our control. For example, no amount of solar panels and wind turbines will arrest the collapse of an ice sheet.

Climate change is now an existential threat

We face a direct existential threat… Extreme heatwaves, wildfires, storms and floods are leaving a trail of death and devastation… We are careering towards the edge of the abyss.

UN, 2018, UN Secretary-General’s press encounter on climate change.1 

The current rate of global warming could raise sea levels by “several meters” over the coming century, rendering most of the world’s coastal cities uninhabitable and helping unleash devastating storms, according to a paper published by James Hansen, the former Nasa scientist who is considered the father of modern climate change awareness.

The Guardian, 2016, Climate guru James Hansen warns of much worse than expected sea level rise.2

The abundant empirical evidence of the unprecedented rate and global scale of impact of human influence on the Earth System has led many scientists to call for an acknowledgement that the Earth has entered a new geological epoch: the Anthropocene. Although rates of change in the Anthropocene are necessarily assessed over much shorter periods than those used to calculate long-term baseline rates of change, and therefore present challenges for direct comparison, they are nevertheless striking. The rise in global CO2 concentration since 2000 is about 20 ppm per decade, which is up to 10 times faster than any sustained rise in CO2 during the past 800,000 years. AR5 (the IPCC fifth assessment report)3 found that the last geological epoch with similar atmospheric CO2 concentration was the Pliocene, 3.3 to 3.0 Ma (million years ago). Since 1970 the global average temperature has been rising at a rate of 1.7°C per century, compared to a long-term decline over the past 7,000 years at a baseline rate of 0.01°C per century. These global-level rates of human-driven change far exceed the rates of change driven by geophysical or biosphere forces that have altered the Earth System trajectory in the past; even abrupt geophysical events do not approach current rates of human-driven change.

IPCC, 2018, Global warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways.4

As explained in Part 1, humanity’s CO2 emissions: (i) are currently trapping two thirds of the energy causing global warming, (ii) are the only rapidly increasing contributor, (iii) solely determine our long term warming commitment, and (iv) continue to grow with no peak in sight. Half of all CO2 ever emitted has been emitted recently and almost all by the world’s energy system.

The World Meteorological Organisation (WMO) points out that COannual rates of change since preindustrial times have been, and still are, about 10 times faster than the fastest natural change, and that levels of atmospheric CO2 concentration are now similar to climates million of years in the past when seas were much higher.5

The increase in CO2 from 2015 to 2016 was larger than the increase observed from 2014 to 2015 and the average over the last decade.
Direct measurements of atmospheric CO2 over the past 800,000 years provide proof that over the past eight swings between ice ages (glacials) and warm periods similar to today (interglacials) atmospheric CO2 varied between 180 and 280 parts per million (ppm), demonstrating that today’s CO2 concentration of 400ppm exceeds the natural variability seen over hundreds of thousands of years. Over the past decade, new high-resolution ice core records have been used to investigate how fast atmospheric CO2 changed in the past. After the last ice age, some 23,000 years ago, COconcentrations and temperature began to rise. During the period recorded in the West Antarctica ice core, fastest CO2 increases (16,000, 15,000 and 12,000 years ago) ranged between 10 and 15ppm over 100–200 years. In comparison, CO2 has increased by 120ppm in the last 150 years due to combustion of fossil fuel. 
Periods of the past with a CO2 concentration similar to the current one can provide estimates for the associated “equilibrium” climate. In the mid-Pliocene, 3–5 million years ago, the last time that the Earth’s atmosphere contained 400ppm of CO2, global mean surface temperature was 2–3℃ warmer than today, the Greenland and West Antarctic ice sheets melted and even some of the East Antarctic ice was lost, leading to sea levels that were 10–20m higher than they are today. During the mid-Miocene (15–17 million years ago), atmospheric CO2 reached 400–650ppm and global mean surface temperature was 3–4℃ warmer than today.

WMO, 2017, State of the Global Climate in 2017.5

The WMO states:6

  • Global mean temperatures in 2017 were 1.1℃ ± 0.1℃ above pre-industrial levels
  • Average global temperature for 2013 to 2017 was close to 1℃ above that for 1850 to 1900
  • 2013 to 2017 was the highest five-year average on record
Global mean temperature anomalies, with respect to the 1850 to 1900 baseline, for the five global datasets. Reprinted from figure 1 of WMO, 2017, State of the Global Climate in 2017.7

A striking consequence of global heating8 is rapid retreat of glaciers, such as the Upsala glacier in the Southern Andes:

Upsala Glacier, Southern Patagonian Ice Field, Argentina and Chile. Credit: Fabiano Ventura.9

The charts below show the obvious global trend of glacier retreat:

Selection of long-term cumulative glacier length changes as compiled from in situ measurements. Reprinted from Fig 4.9, p. 339 of Vaughan et al., 2013, Observations: Cryosphere. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.10

Glaciers in Alaska have dramatically retreated:

Muir Glacier, Alaska Range.11
McCarty Glacier, Alaska Range.11
Bear Glacier, Alaska Range.11
Northwestern Glacier, Alaska Range.11
Retreat of the Columbia Glacier, Alaska, USA, by ~6.5 km between 2009 and 2015. Credit: James Balog and the Extreme Ice Survey.12

Global warming is rapidly melting Arctic sea ice, thereby triggering a fast amplifying feedback that drives further global warming. This is known as polar amplification or the sea ice/ocean surface albedo feedback: “With retreating sea ice, surface albedo decreases, air temperatures increase and the ocean can absorb more heat. The resulting ocean warming contributes to further sea ice melting.”13

Sea ice helps to keep the Arctic atmosphere cold. Its whiteness reflects much of the Sun’s energy back to space, and it physically insulates the Arctic atmosphere from the underlying Arctic Ocean. With less sea ice, more dark open water is exposed, which readily absorbs the Sun’s energy in summer, heating the ocean and leading to even more melt. With less sea ice there is also less insulation, so that heat from the ocean escapes to warm the atmosphere in the autumn and winter.

NSIDC, 2009, Highlights–Arctic Amplification.14
Temperature anomalies for period 2015 to 2018 relative to 1951 to 1980 base period. From NASA Goddard Institute for Space Studies (GISS), showing increased Arctic warming. The 1951 to 1980 base period is used because global heating was roughly constant for this period (see Chart 6) and the preindustrial period 1880 to 1920 suffers from limited data coverage. Reprinted from Fig 2 of Hansen et al., 2019, Global Temperature in 2018 and Beyond.15
Global surface temperatures relative to the 1880 to 1920 base period. From NASA Goddard Institute for Space Studies (GISS), showing the stable stable period of 1951–1980. Reprinted from Fig 1 of Hansen et al., 2019, Global Temperature in 2018 and Beyond.15

Surface air temperatures in the Arctic continued to warm at twice the rate relative to the rest of the globe. Arctic air temperatures for the past five years (2014-18) have exceeded all previous records since 1900.

In 2018 Arctic sea ice remained younger, thinner, and covered less area than in the past. The 12 lowest extents in the satellite record have occurred in the last 12 years.

NOAA, 2018, Arctic Report Card.16

Dr. Osborne, the lead editor of the report and manager of NOAA’s Arctic Research Program, said the Arctic was undergoing its “most unprecedented transition in human history.”

In 2018, “warming air and ocean temperatures continued to drive broad long-term change across the polar region, pushing the Arctic into uncharted territory,” she said at a meeting of the American Geophysical Union in Washington.

NYT, 2018, Warming in Arctic Raises Fears of a ‘Rapid Unraveling’ of the Region.17

Arctic sea ice extent18 increases during the colder months, reaching a maximum in March, and decreases in the warmer months, reaching a minimum in September. This cycle is shown below:

“Charctic” Interactive Sea Ice Graph, NSIDC.19

Summer Arctic sea ice extent has reduced to about two-thirds of the 1981 to 2000 mean (also known as “average”), as shown by the black line below:

Arctic sea ice extent by proportion of 1981 to 2000 mean. Monthly data points from NSIDC.20

The following video explains the decline of the annual creation and extent of Arctic sea ice.

NOAA, 2018, Recent trends of Arctic sea ice.21

Older, and therefore thicker Arctic sea ice has almost completely disappeared:

Over the past three decades of global warming, the oldest and thickest ice in the Arctic has declined by a stunning 95 percent, according the National Oceanic and Atmospheric Administration’s annual Arctic Report Card.

The finding suggests that the sea at the top of the world has already morphed into a new and very different state, with major implications not only for creatures such as walruses and polar bears but, in the long term, perhaps for the pace of global warming itself.

Increasingly, what remains is ice that only forms after the peak warmth of the summer, usually in September, and which may not survive the following summer. This “first year ice” is more brittle, more easily tossed around by winds and waves, rendering the Arctic ice pack more mobile and prone to breaking apart.

In 1985, the new NOAA report found, 16 percent of the Arctic was covered by the very oldest ice, more than four years old, at the height of winter. But by March, that number had dropped to under 1 percent. That’s a 95 percent decline.

At the same time, the youngest, first-year ice has gone from 55 percent of the pack in the 1980s to 77 percent, the report finds. (The remainder is ice that is two to three years old.)

The Washington Post, 2018, The Arctic Ocean has lost 95 percent of its oldest ice — a startling sign of what’s to come.22
Arctic sea ice extent by age, in March. Chart reprinted from NSIDC and NASA.23
Arctic sea ice extent by age, in September. Chart reprinted from NSIDC and NASA.23

This process of reverse-aging, scientists say, is all headed to a crucial moment — when all of the ice in the Arctic will be thin and a year old or less. When that happens — the day of maximum youth — we will be on the verge of a much feared milestone: an entirely ice-free Arctic Ocean in summer.
“Looking down from the North Pole from above, for all intents and purposes, you’re going to see a blue Arctic Ocean” Meier said.24

Ramanathan25 fears that entirely ice-free summers, if they began to occur regularly, could add another half-degree Celsius (0.9 degrees Fahrenheit) of warming on top of whatever else the planet has experienced by that time.
“If that were to happen, I would think of it as an unmitigated disaster,” said Ramanathan of consistently ice-free Arctic summers. “It will quickly pump in this half a degree warming.”

The Washington Post, 2018, The Arctic Ocean has lost 95 percent of its oldest ice — a startling sign of what’s to come.22

Climate change impacts

The list below is adapted from the paper ‘Assessing ‘‘Dangerous Climate Change’’: Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature’ by Dr Hansen et al.26

Sea level rise

Plausibly, the climate change impact with most severe consequences for civilisation will be rapid multi-metre sea level rise from the collapse of Earth’s ice sheets – the Greenland ice sheet, the West Antarctic ice sheet (WAIS) and the East Antarctic ice sheet (EAIS). This impact alone is a threat to the existence of global civilisation not only because of greater coastal flooding and storm surges, but also the financial and economic ramifications from the flooding of wealthy cities and ports, and the interruptions to international trade.

Ice sheets, as opposed to ice shelfs, sit on bedrock that may be above or below sea level, and are dynamic – continuously gaining and losing mass. They gain mass from snow and rain that falls on them, which accumulates and compacts to form ice. This ice gradually drains to the ocean via rivers of ice known as glaciers which may terminate at the ocean, making them marine terminated glaciers. The point where an ice sheet leaves the bedrock it rests upon, and becomes afloat is known as the grounding line (see figure below). Here, the flow of ice leaves land and floats on the ocean surface, forming a tongue of ice known as an ice shelf.

MISI (Marine Ice-Sheet Instability) due to a marine based ice sheet on a bed with retrograde slope. Reprinted from Fig. 1a of Pattyn, 2018, The paradigm shift in Antarctic ice sheet modelling.27

Global warming has caused the flow rate of the glaciers that drain the Greenland and WAIS to increase, putting the ice sheets out of mass balance (“more ice going out, than forming from falling snow and rain”), and their grounding lines have rapidly retreated.28

Unfortunately for civilisation, there are characteristics unique to the ice sheets that will cause them to rapidly melt and fracture due to amplifying feedbacks: (i) three of the glaciers that drain the Greenland ice sheet, some of those that drain EAIS and all of those that drain WAIS have submerged grounding lines that lie on bedrock with a reverse, or retrograde slope as shown in the diagram above, and (ii) almost the entirety of WAIS is grounded on bedrock below sea level. The amplifying feedbacks are: (i) as the glaciers retreat, their terminating face becomes taller and exposed to deeper and deeper warm ocean water due to the retrograde slope of the bedrock, ever increasing the rate of melt and fracture, (ii) the ice cliff at the face of glacier above sea level becomes taller, less stable and more likely to collapse, (iii) friction of the ice flowing in the glacier reduces, causing the glacier’s velocity to increase, (iv) the end of the glacier becomes lighter, lifting off the bedrock allowing warm ocean water to melt it from underneath, and (v) the glacier meltwater at the glacier’s outlet acts a lid trapping warm ocean water at the base of the glacier. The meltwater freshens the ocean water, making it less dense, reducing ocean heat circulation to the surface, preventing this heat venting to the atmosphere and space.

All these amplifying feedbacks will continuously accelerate glacier melt and fracture. These are explained further below, along with evidence from Earth’s climatic past (paleoclimate data) that demonstrates rapid multi-metre sea level rise is expected.

As far as anyone knows, no human had ever set foot on the West Antarctica glaciers until the International Geophysical Year, in 1957, a Cold War collaboration of the U.S. and the Soviet Union and other nations to expand the boundaries of scientific exploration. A team of scientists had trekked across the glaciers of West Antarctica, including Thwaites; by drilling ice cores and taking other measurements, they discovered that the ground beneath the ice was on a reverse slope and had been depressed further by the weight of the glaciers over millions of years. “Think of it as a giant soup bowl filled with ice,” says Sridhar Anandakrishnan, an expert in polar glaciology at Penn State University.

RollingStone, 2017, The Doomsday Glacier.29

This is shown in the diagram below as cross-hatched areas in (b).

(a) Map of Antarctica showing the delineation between West and East Antarctica.30(b) West Antarctica showing ice shelves, ice grounded below sea level and ice covering land above sea level. Reprinted from Fig. 2. of Mercer, 1978, West Antarctic ice sheet and CO2 greenhouse effect: a threat of disaster.31

Then, in 1974, Hans Weertman, a materials scientist at Northwestern University, figured out that these glaciers in West Antarctica were more vulnerable to rapid melting than anyone had previously understood. He coined a term for it: “marine ice-sheet instability.” Weertman pointed out that warm ocean water could penetrate the grounding line, melting the ice from below. If the melting continued at a rate that was faster than the glacier grew – which is currently the case – the glacier would slip off the grounding line and begin retreating backward down the slope, like “a ball rolling downhill,” says Howat, the Ohio State glaciologist. As the glacier becomes grounded in deeper and deeper water, more of the ice is exposed to warming ocean water, which in turn increases the rate of melt. At the same time, parts of the glacier want to float, which places additional stress on the ice, causing it to fracture. As the face of the glacier collapses, or “calves,” more and more ice falls into the sea. The farther the glacier retreats down the slope, the faster the collapse unfolds. Without quite meaning to, Weertman had discovered a mechanism for catastrophic sea-level rise.

Mercer saw that Weertman’s breakthrough had big implications. In a 1978 paper called “West Antarctic Ice Sheet and the CO2Greenhouse Effect: A Threat of Disaster,”32 Mercer focused on the floating ice shelves that buttress the West Antarctica glaciers. Because they are thinner and floating in the ocean, as the water warms they will be the first to go. And when they do, they will not only reduce friction that slows the glaciers’ slide into the sea, they will change the balance of the glaciers, causing them to float off the grounding line. And that, in turn, will advance their retreat down the slope. Mercer argued that this whole system was more unstable than even Weertman had realized. “I contend that a major disaster – a rapid (16-foot) rise in sea level, caused by the deglaciation of West Antarctica – may be imminent,” he wrote

RollingStone, 2017, The Doomsday Glacier.29
RollingStone, 2017, The Doomsday Glacier.29

As the ocean warms it begins to melt ice shelves, the tongues of ice that extend from the ice sheets into the ocean. These ice shelves buttress the land-based ice sheets. Thus as the ice shelves melt, the ice sheets expel ice into the ocean at a faster rate. This process is self-amplifying, because the melting icebergs freshen the ocean surface waters. Fresh water reduces the density of the ocean surface layer, thus reducing the ocean’s vertical overturning, which in turn reduces the release of ocean heat into the atmosphere and space. Instead, this ocean heat stays at depth, where it accelerates the rate of ice shelf melting.

The danger is that the ice discharge will pass a tipping point such that the amplifying feedbacks cause rapid acceleration of the melting process. It is even possible that, for a vulnerable portion of the Antarctic ice sheet sitting on bedrock well below sea level, the melting process could become self-sustaining. In that case, we say that a ‘point of no return’ is reached and it is too late to prevent discharge of massive amounts of ice, sufficient to raise sea level several meters. My colleagues and I estimate that this process could lead to multi-meter sea level rise in a period as short as 50 – 150 years, if greenhouse gases continue to increase rapidly.

If global warming continues unabated, portions of the ice sheets will become unstable, ice sheet disintegration will accelerate, and sea level will rise continuously. A majority of large U.S. and global cities are coastal. Continued high fossil fuel emissions will lead to eventual sea level rise that makes these cities dysfunctional, with consequences that are incalculable.

Hansen, 2018, Climate Change in a Nutshell: The Gathering Storm p.10-11.33

In the past, Earth’s climate alternated between ice ages and warm periods. Civilisation developed during the warm period known as the Holocene. The prior warm period is known as the Eemian, which lasted from 130,000 to 115,000 years ago.34 The best estimate of the maximum global surface temperature of the Eemian, relative to preindustrial time, is between +1℃ and +1.5℃ (+1.8℉ to +2.7℉).34 The global surface temperature averaged over 2009–2018 was +0.93℃ relative to preindustrial time, and averaged over 2014–2018 was +1.04℃.35 36 Therefore civilisation may have caused Earth’s climate to leave the Holocene and return to the Eemian.

The Holocene, over 11,700 years in duration, had relatively stable climate, prior to the remarkable warming in the past half century. The Eemian, which lasted from about 130,000 to 115,000 years ago, was moderately warmer than the Holocene and experienced sea level rise to heights 6–9 m (20–30 ft) greater than today.

Young people’s burden: requirement of negative CO2 emissions.37

Professor Eric Rignot explains below the mapping of glaciers on Greenland and Antarctica, how these glaciers are changing and the consequences of rapid multi-meter sea level rise that will soon occur as a result of 1.5℃ to 2℃ warming:

Rignot, 2017. Watching the planet’s ice sheets disappear.38

Below Dr James Hansen explains the amplifying feedbacks between the ocean and ice-sheets, in which he states: “These feedbacks raise questions about how soon we will pass points of no return and in which we lock in consequences that cannot be reversed on any time scale that people care about, consequences include sea level rise of several meters”:

Hansen, 2016. Ice Melt, Sea Level Rise and Superstorms: The Threat of Irreparable Harm.39

Pine Island, Thwaites, Haynes, Smith, Pope, and Kohler Glaciers are among the fastest-flowing glaciers in continental Antarctica. Combined together, they drain one third of the West Antarctic Ice Sheet into the Amundsen Sea Embayment (ASE). Their mass flux into the southern Pacific Ocean is comparable to that of the entire Greenland Ice Sheet into the Arctic Ocean. Since first revealed with satellite radar interferometry in the 1990s, this sector has been significantly out of balance due to glacier speedup. Concurrent with the acceleration in ice flow, the glaciers have been thinning and their grounding-line positions—where ice goes afloat—have been retreating at a rate of 1 km/yr, one of the fastest retreat rates in the world. Together, these glaciers and their catchment basins combined contain 1.2 m global sea level rise.

Observations of the ASE of West Antarctica since 1973 indicate speedup of all the glaciers and a steady increase in ice discharge into the ocean from the collective ensemble of these large, major glaciers. During retreat across their respective ice plains, Pine Island and Smith Glaciers underwent a rapid increase in ice discharge. However, since 2009, the ice discharge of Pine Island has remained steady. Thwaites Glacier, which had experienced a steady flow since 1992, started to speed up in 2006 and has increased its ice discharge considerably since.

Mouginot et al., 2014, Sustained increase in ice discharge from the Amundsen Sea Embayment, West Antarctica, from 1973 to 2013.28

The Antarctic lost 40 billion tons of melting ice to the ocean each year from 1979 to 1989. That figure rose to 252 billion tons lost per year beginning in 2009, according to a study published Monday in the Proceedings of the National Academy of Sciences. That means the region is losing six times as much ice as it was four decades ago, an unprecedented pace in the era of modern measurements. (It takes about 360 billion tons of ice to produce one millimeter of global sea-level rise.)

“I don’t want to be alarmist,” said Eric Rignot, an Earth-systems scientist for the University of California at Irvine and NASA who led the work. But he said the weaknesses that researchers have detected in East Antarctica — home to the largest ice sheet on the planet — deserve deeper study.

“The places undergoing changes in Antarctica are not limited to just a couple places,” Rignot said. “They seem to be more extensive than what we thought. That, to me, seems to be reason for concern.”

“The traditional view from many decades ago is that nothing much is happening in East Antarctica,” Rignot said, adding, “It’s a little bit like wishful thinking.”

The Washington Post, 2019, ‘Ice loss from Antarctica has sextupled since the 1970s, new research finds'40
Map of Antarctic ice velocity in 2011, place names and drainage basins. Reprinted from Fig. 1. of Rignot et al., 2011, Ice flow of the Antarctic ice sheet.41

East Antarctica has the potential to reshape coastlines around the world through sea level rise, but scientists have long considered it more stable than its neighbor, West Antarctica. Now, new detailed NASA maps of ice velocity and elevation show that a group of glaciers spanning one-eighth of East Antarctica’s coast have begun to lose ice over the past decade, hinting at widespread changes in the ocean.

“Totten is the biggest glacier in East Antarctica, so it attracts most of the research focus,” said Catherine Walker, a glaciologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who presented her findings at a press conference on Monday at the American Geophysical Union meeting in Washington. “But once you start asking what else is happening in this region, it turns out that other nearby glaciers are responding in a similar way to Totten.”

Walker found that four glaciers west of Totten, in an area called Vincennes Bay, have lowered their surface height by about 9 feet (almost 3 meters) since 2008—before that year, there had been no measured change in elevation for these glaciers. Farther east, a collection of glaciers along the Wilkes Land coast have approximately doubled their rate of lowering since around 2009, and their surface is now going down by about 0.8 feet (0.24 meters) every year.

“The change doesn’t seem random; it looks systematic,” said Alex Gardner, a glaciologist with NASA’s Jet Propulsion Laboratory in Pasadena, California. 

“Those two groups of glaciers drain the two largest subglacial basins in East Antarctica, and both basins are grounded below sea level,” Walker said. “If warm water can get far enough back, it can progressively reach deeper and deeper ice. This would likely speed up glacier melt and acceleration, but we don’t know yet how fast that would happen. Still, that’s why people are looking at these glaciers, because if you start to see them picking up speed, that suggests that things are destabilizing.”

There is a lot of uncertainty about how a warming ocean might affect these glaciers, due to how little explored that remote area of East Antarctica is.

For example, if it turned out that the terrain beneath the glaciers sloped upward inland of the grounding line—the point where glaciers reach the ocean and begin floating over sea water, forming an ice shelf—and featured ridges that provided friction, this configuration would slow down the flow and loss of ice. This type of landscape would also limit the access of warm circumpolar deep ocean waters to the ice front.

A much worse scenario for ice loss would be if the bedrock under the glaciers sloped downward inland of the grounding line. In that case, the ice base would get deeper and deeper as the glacier retreated and, as ice calved off, the height of the ice face exposed to the ocean would increase. That would allow for more melt at the front of the glacier and also make the ice cliff more unstable, increasing the rate of iceberg release. This kind of terrain would make it easier for warm circumpolar deep water to reach the ice front, sustaining high melt rates near the grounding line.

NASA, 2018, More glaciers in East Antarctica are waking up.42
Hansen, 2018, Aerosol Effects on Climate & Human Health: Urgent Research Needs.43
Hansen, 2006, The Case for Action by the State of California to Mitigate Climate Change.44
Hansen, 2006, The Case for Action by the State of California to Mitigate Climate Change.44

Human health and wellbeing

Impacts of climate change cause widespread harm to human health, with children often suffering the most. Food shortages, polluted air, contaminated or scarce supplies of water, an expanding area of vectors causing infectious diseases, and more intensely allergenic plants are among the harmful impacts. More extreme weather events cause physical and psychological harm. World health experts have concluded with ‘‘very high confidence’’ that climate change already contributes to the global burden of disease and premature death.

IPCC projects the following trends, if global warming continues to increase, where only trends assigned very high confidence or high confidence are included: (i) increased malnutrition and consequent disorders, including those related to child growth and development, (ii) increased death, disease and injuries from heat waves, floods, storms, fires and droughts, (iii) increased cardio-respiratory morbidity and mortality associated with ground-level ozone. While IPCC also projects fewer deaths from cold, this positive effect is far outweighed by the negative ones.

Growing awareness of the consequences of human-caused climate change triggers anxiety and feelings of helplessness. Children, already susceptible to age-related insecurities, face additional destabilizing insecurities from questions about how they will cope with future climate change. Exposure to media ensures that children cannot escape hearing that their future and that of other species is at stake, and that the window of opportunity to avoid dramatic climate impacts is closing. The psychological health of our children is a priority, but denial of the truth exposes our children to even greater risk.

Hansen et al., 2013, Assessing ‘‘Dangerous Climate Change’’: Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature, p. 6.45

In 2013 and 2014, the World Bank Group published a series of reports detailing how climate change impacts will be felt disproportionately in developing countries around the equatorial regions:46

With a focus on Sub-Saharan Africa, South East Asia and South Asia, the report examines in greater detail the likely impacts for affected populations of present day, 2°C and 4°C warming on critical areas like agricultural production, water resources, coastal ecosystems and cities.

The result is a dramatic picture of a world of climate and weather extremes causing devastation and human suffering. In many cases, multiple threats of increasing extreme heat waves, sea-level rise, more severe storms, droughts and floods will have severe negative implications for the poorest and most vulnerable.

In Sub-Saharan Africa, significant crop yield reductions with 2°C warming are expected to have strong repercussions on food security, while rising temperatures could cause major loss of savanna grasslands threatening pastoral livelihoods. In South Asia, projected changes to the monsoon system and rising peak temperatures put water and food resources at severe risk. Energy security is threatened, too. While, across South East Asia, rural livelihoods are faced with mounting pressures as sea-level rises, tropical cyclones increase in intensity and important marine ecosystem services are lost as warming approaches 4°C.

Across all regions, the likely movement of impacted communities into urban areas could lead to ever higher numbers of people in informal settlements being exposed to heat waves, flooding, and diseases.

World Bank. 2013. Turn Down the Heat: Climate Extremes, Regional Impacts, and the Case for Resilience.47

For this report, the third in the Turn Down the Heat series, we turned again to the scientists at the Potsdam Institute for Climate Impact Research and Climate Analytics. We asked them to look at the likely impacts of present day (0.8°C), 2°C and 4°C warming on agricultural production, water resources, cities and ecosystems across Latin America and the Caribbean, Middle East and North Africa, and parts of Europe and Central Asia.

Their findings are alarming.

In Latin America and the Caribbean, heat extremes and changing precipitation patterns will have adverse effects on agricultural productivity, hydrological regimes and biodiversity. In Brazil, at 2°C warming, crop yields could decrease by up to 70 percent for soybean and up to 50 percent for wheat. Ocean acidification, sea level rise, tropical cyclones and temperature changes will negatively impact coastal livelihoods, tourism, health and food and water security, particularly in the Caribbean. Melting glaciers would be a hazard for Andean cities.

In the Middle East and North Africa, a large increase in heat-waves combined with warmer average temperatures will put intense pressure on already scarce water resources with major consequences for regional food security. Crop yields could decrease by up to 30 percent at 1.5–2°C and by almost 60 percent at 3–4°C. At the same time, migration and climate-related pressure on resources might increase the risk of conflict.

In the Western Balkans and Central Asia, reduced water availability in some places becomes a threat as temperatures rise toward 4°C. Melting glaciers in Central Asia and shifts in the timing of water flows will lead to less water resources in summer months and high risks of torrential floods. In the Balkans, a higher risk of drought results in potential declines for crop yields, urban health, and energy generation. In Macedonia, yield losses are projected of up to 50 percent for maize, wheat, vegetables and grapes at 2°C warming. In northern Russia, forest dieback and thawing of permafrost threaten to amplify global warming as stored carbon and methane are released into the atmosphere, giving rise to a self-amplifying feedback loop.

World Bank. 2014. Turn Down the Heat: Confronting the New Climate Normal.48

The World Bank report ‘Groundswell’ states:49

Under all three scenarios in this report, there is an upward trend of internal climate migration in Sub-Saharan Africa, South Asia, and Latin America by 2050. In the worst-case or “pessimistic” scenario, the number of internal climate migrants could reach more than 143 million (around 86 million in Sub-Saharan Africa, 40 million in South Asia, and 17 million in Latin America) by 2050. The poorest people and the poorest countries are the hardest hit.

Across all scenarios, climate change is a growing driver of internal migration. Climate change impacts (crop failure, water stress, sea level rise) increase the probability of migration under distress, creating growing challenges for human development and planning. Vulnerable people have the fewest opportunities to adapt locally or to move away from risk and, when moving, often do so as a last resort. Others, even more vulnerable, will be unable to move, trapped in increasingly unviable areas.

Internal climate migration will intensify over the next several decades and could accelerate after 2050 under the pessimistic scenario due to stronger climate impacts combined with steep population growth in many regions.

World Bank Group, 2018, Groundswell – Preparing for internal climate migration.49
World Bank Group, 2018, – Preparing for internal climate migration.49

Water from glacial runoff is an important supply for some cities and rural communities, for agricultural production and for hydroelectric power generation. Glaciers help to regulate streamflow in regions where water is stored during colder periods of the year, and later released as melt water runoff during warm dry conditions.50 An example of this is the Chacaltaya glacier, that was a supply of water for drinking and hydroelectric power in Bolivia’s main cities, La Paz and El Alto.51 The three main dams that supply these cities are no longer fed by runoff from glaciers and have almost run dry. Water rationing was introduced and the armed forces were brought in to distribute water while emergency wells were drilled.52

Climate extremes

The charts below show the change of summer and winter temperatures in the northern hemisphere (NH), and summer in the southern hemisphere (SH).53 Prior to 1980, hot summers and cold summers each occurred over approximately 30% of Earth’s land area. Cold summers now occur over about 5%, and hot summers about 80% of Earth’s land area. Summers so unusually hot they rarely occurred anywhere prior to 1980, now cover about 30% of northern hemisphere land area, and 20% in the southern hemisphere (i.e. the bright red lines in the top and bottom rows).

Area covered by temperature anomalies for NH summer, in the categories defined as hot, very hot, and extremely hot, with analogous divisions for cold anomalies. Anomalies are relative to 1951–1980 base period. The centre column of boxes shows the proportion of land area that experienced a respective season typical of the period 1951–1980. Reprinted from Hansen et al., 2012, Perception of climate change.54

Consequently, the area burned by wildfire annually in the U.S. has increased.

Total wildland acres burned in the U.S.55

Changes in the frequency and magnitude of climate extremes, of both moisture and temperature, are affected by climate trends as well as changing variability. Extremes of the hydrologic cycle are expected to intensify in a warmer world. A warmer atmosphere holds more moisture, so precipitation can be heavier and cause more extreme flooding. Higher temperatures, on the other hand, increase evaporation and can intensify droughts when they occur, as can expansion of the subtropics.

An increase of intense precipitation events has been found on much of the world’s land area.

Heat waves lasting for weeks have a devastating impact on human health: the European heat wave of summer 2003 caused over 70,000 excess deaths. This heat record for Europe was surpassed already in 2010. The number of extreme heat waves has increased several-fold due to global warming and will increase further if temperatures continue to rise.

Hansen et al., 2013, Assessing ‘‘Dangerous Climate Change’’: Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature.56

Seasons vary year to year, with some winters being extremely cold, some being mild and some being warmer than others. The same applies to the other seasons. If a chart is drawn showing the difference between the mean (or “average”) temperature of each month within a season for a given year, and the long term mean for that season, the result is the shape of a bell as shown in the example below, also known as a Normal distribution:

Example of a Bell curve.

The bell curve will vary in width and height depending on the geographical area and time period being considered. The y-axis can be interpreted as “frequency of occurrence”, with the peak in the centre being the most frequently occurring value because it’s the mean. Deviations from the mean in either direction, shown by the x-axis, represent cool or hot months for the season being plotted. To allow changes to be compared between different regions of Earth, the x-axis can be scaled as numbers of standard deviations, and then the bell curves plotted for seasons of consecutive years, as has been done below. This demonstrates that the seasons over different areas have rapidly warmed since the climatically stable period of 1951 to 1980. Note the increased proportion of extremely hot months for a given season, as a result of 1.1℃ of global warming.

Bell curve shifts over the northern hemisphere in summer (top) and winter (bottom). Reprinted from Hansen et al., 2012, Perception of climate change.54 Updated versions of figures may be available.57
Geographic bell curve shifts.58 Note the percentage figure in the top right of each map is the proportion of Earth’s land area. Updated versions of figures may be available.59

Note that almost half of the months shown are now so hot that they never occurred during 1951 to 80 over the African rainforest region and south east Asia. The same applies to summer in the Mediterranean and the Middle East.

Shifting climate zones

Wild species have responded to climate change, with three-quarters of marine species shifting their ranges poleward as much as 1,000 km and more than half of terrestrial species shifting ranges poleward as much as 600 km and upward as much as 400 m.

Hansen et al., 2013, Assessing ‘‘Dangerous Climate Change’’: Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature.60

Human extermination of species

Biodiversity is affected by many agents including overharvesting, introduction of exotic species, land use changes, nitrogen fertilization, and direct effects of increased atmospheric CO2 on plant ecophysiology. However, an overriding role of climate change is exposed by diverse effects of rapid warming on animals, plants, and insects in the past three decades.

A sudden widespread decline of frogs, with extinction of entire mountain-restricted species attributed to global warming, provided a dramatic awakening. There are multiple causes of the detailed processes involved in global amphibian declines and extinctions, but global warming is a key contributor and portends a planetary-scale mass extinction in the making unless action is taken to stabilize climate while also fighting biodiversity’s other threats.

Mountain-restricted and polar-restricted species are particularly vulnerable. As isotherms move up the mountainside and poleward, so does the climate zone in which a given species can survive. If global warming continues unabated, many of these species will be effectively pushed off the planet. There are already reductions in the population and health of Arctic species in the southern parts of the Arctic, Antarctic species in the northern parts of the Antarctic, and alpine species worldwide.

A critical factor for survival of some Arctic species is retention of all-year sea ice. Continued growth of fossil fuel emissions will cause loss of all Arctic summer sea ice within several decades.

IPCC reviewed studies relevant to estimating eventual extinctions. They estimate that if global warming exceeds 1.6℃ above preindustrial, 9–31 percent of species will be committed to extinction. With global warming of 2.9℃, an estimated 21–52 percent of species will be committed to extinction.

Hansen et al., 2013, Assessing ‘‘Dangerous Climate Change’’: Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature.60

Seventeen years ago, in the mountains of Costa Rica, the Monteverde harlequin frog (Atelopus sp.) vanished along with the golden toad (Bufo periglenes). An estimated 67% of the 110 or so species of Atelopus, which are endemic to the American tropics, have met the same fate, and a pathogenic chytrid fungus (Batrachochytrium dendrobatidis) is implicated. Analysing the timing of losses in relation to changes in sea surface and air temperatures, we conclude with ‘very high confidence’ (> 99%, following the Intergovernmental Panel on Climate Change, IPCC) that large-scale warming is a key factor in the disappearances. We propose that temperatures at many highland localities are shifting towards the growth optimum of Batrachochytrium, thus encouraging outbreaks. With climate change promoting infectious disease and eroding biodiversity, the urgency of reducing greenhouse-gas concentrations is now undeniable.

Pounds et al., 2006, Widespread amphibian extinctions from epidemic disease driven by global warming.61

Despite increase of vegetation available for grazing, herd populations of caribou and wild reindeer across the Arctic tundra have declined by nearly 50% over the last two decades.

NOAA, 2018, Arctic Report Card.16

Among the most clear and profound influences of climate change on the world’s oceans are its impacts on habitat-forming species such as corals, sea grass, mangroves, salt marsh grasses, and oysters. Collectively, these organisms form the habitat for thousands of other species. Although some resident species may not have absolute requirements for these habitats, many do, and they disappear if the habitat is removed. For example, mass coral bleaching and mortality, the result of increasing temperatures, is already reducing the richness and density of coral reef fishes and other organisms.

Hoegh-Guldberg et al., 2010, The impact of climate change on the world’s marine ecosystems.62

It was not until the global bleaching event of 1982–1983 that widespread bleaching and mortality were recognised as a major phenomenon that could impact coral reef status and health at regional and global scales.

Oppen et al., 2018, Coral bleaching: patterns, processes, causes and consequences.63

Coral reefs provide some of the most biologically rich, productive and economically valuable ecosystems on Earth. Over 25 per cent of all marine species live in coral reefs, and yet they cover less than 0.1 per cent of the ocean, about half the area of France.

Globally, around 850 million people live within 100km of a coral reef and directly benefit from the economic, social and cultural services it provides. Reefs support many economically important fish species, providing food for hundreds of millions of people. They also protect the coast from storms and erosion, and generate jobs and income from fishing, tourism and recreation.

WWF, 2015, Living Blue Planet Report.64

The Great Barrier Reef – which, at 1,400 miles long, is the longest and largest coral reef in the world – was blanketed by dangerously hot water in the summer of 2016. This heat strangled and starved the corals, causing what has been called “an unprecedented bleaching event.”

The Atlantic, 2018, Since 2016, Half of All Coral in the Great Barrier Reef Has Died.65
Life and death after Great Barrier Reef bleaching.66

“On average, across the Great Barrier Reef, one in three corals died in nine months,” said Terry Hughes, an author of the paper and the director of the ARC Center of Excellence for Coral Reef Studies, the Australian government’s federal research program devoted to corals.

About 50 percent of all the coral that perished in the 2016 bleaching event died in the autumn and winter, long after temperatures had returned to normal. Those corals never regained their algae after evicting them, and they slowly starved to death.

“But about half of the corals that died did so in March, at the peak of summer temperatures,” Hughes told me. “We were surprised that about half of that mortality occurred very quickly.”

In other words, some corals did not even survive long enough to starve. “They died instantly, of heat stress,” Hughes said. “They cooked.”

Yet it was not the end of troubles for the Great Barrier Reef. In the summer months of 2017, warm waters again struck the reef and triggered another bleaching event. This time, the heat hit the reef’s middle third. Hughes and his team have not published a peer-reviewed paper on that event, but he shared early survey results with me.

Combined, he said, the back-to-back bleaching events killed one in every two corals in the Great Barrier Reef. It is a fact almost beyond comprehension: In the summer of 2015, more than 2 billion corals lived in the Great Barrier Reef. Half of them are now dead.

The study fits into a streak of dreary findings for coral reefs. If the world were to warm by an average of 2 degrees Celsius, then ocean temperatures would consistently exceed their 2016 levels, even during non-El Niño years, a recent study in Nature Climate Change found. In another study, released in January, scientists surveyed observations of 100 coral reefs around the world going back 35 years. They found that mass bleaching events now strike five times more often than they did in the early 1980s.

The Atlantic, 2018, Since 2016, Half of All Coral in the Great Barrier Reef Has Died.65
ARC Centre of Excellence for Coral Reef Studies.67
ARC Centre of Excellence for Coral Reef Studies.67

More than 70% of coral reefs around the world experienced the heat stress that can cause bleaching and/or mortality during the three-year long global event.

Multiple coral reef ecosystems around the world experienced severe bleaching in back–to–back years, including areas like Guam, where corals bleached every year from 2013 to 2017. As of the end of May 2017, the third global coral bleaching event most likely ended (National Oceanic and Atmospheric Administration (NOAA) 2017) but will remain the longest, most widespread, and possibly the most damaging coral bleaching event on record. It affected more reefs than any previous global bleaching event and was worse in some locales (e.g., Great Barrier Reef, Kiribati, Jarvis Island). Heat stress during this event also caused mass bleaching in several reefs that never bleached before (e.g., northernmost Great Barrier Reef).

Coral Reef Watch, NOAA, 2018.68
Coral Heat Stress. NOAA Coral Reef Watch 5km Maximum Satellite Coral Bleaching Alert Area, June 2014–May 2017. Alert Level 2 heat stress indicates widespread coral bleaching and significant mortality. Alert Level 1 heat stress indicates significant coral bleaching. Lower levels of stress may have caused some bleaching as well. Coral Reef Watch, NOAA, 2018.68

Recurrent regional-scale (>1000 km) bleaching and mortality of corals is a modern phenomenon caused by anthropogenic global warming. Bleaching before the 1980s was recorded only at a local scale of a few tens of kilometers because of small-scale stressors such as freshwater inundation, sedimentation, or unusually cold or hot weather.

Our findings reveal that coral reefs have entered the distinctive human-dominated era characterized as the Anthropocene, in which the frequency and intensity of bleaching events is rapidly approaching unsustainable levels.

At the spatial scale we examined, the number of years between recurrent severe bleaching events has diminished fivefold in the past four decades, from once every 25 to 30 years in the early 1980s to once every 5.9 years in 2016.

The time between recurrent events is increasingly too short to allow a full recovery of mature coral assemblages, which generally takes from 10 to 15 years for the fastest growing species and far longer for the full complement of life histories and morphologies of older assemblages.

Hughes et al., 2018, Spatial and temporal patterns of mass bleaching of corals in the Anthropocene.69

The summer of 2016 remains one of the most severe coral bleaching and die-off events ever observed—a level of devastation that scientists didn’t expect to see until the 2050s. A new study argues that it will not remain a rare event for long. Even in simulations of the most hopeful global-warming scenarios, modern climate models suggest that ocean temperatures around the Great Barrier Reef will regularly surpass the devastating warmth of 2016.

In a 1.5-degree world, there’s still about a two-thirds chance that any summer would bring 2016-level heat to the Great Barrier Reef. And even in the coolest, kindest of the scenarios—the “gentlest” version of a 1.5-degree world—the odds of 2016-level heat are just over 50 percent. The reef would bleach every other year.

The Atlantic, 2017, The Great Barrier Reef Is Probably Doomed No Matter What.70

Marine heatwaves have also devastated kelp forests. “Kelp is a type of seaweed (or marine algae) that describes 27 genera worldwide. Some kelps form dense patches on rocky reefs resembling a forest of trees underwater and are referred to as kelp forests.”71

Diver in kelp forest, University of Tasmania Institute for Marine and Antarctic Studies.72

The first global study of kelp forest change over 50 years concluded that kelp had declined in 38% of the 1,138 sites studied globally.72

A hundred kilometres of kelp forests off the western coast of Australia were wiped out by a marine heatwave between 2010 and 2013, a new study has revealed.

About 90% of the forests that make up the north-western tip of the Great Southern Reef disappeared over the period, replaced by seaweed turfs, corals, and coral fish usually found in tropical and subtropical waters.

The Great Southern Reef is a system of rocky reefs covered by kelp forests that runs along the south coast of Australia, extending past Sydney on the east coast, down to Tasmania and, previously, back up to Kalbarri on the west coast.

It supports most of the nation’s fisheries, including the lucrative rock lobster and abalone fisheries, and is worth about $10bn to the Australian economy. It is also a global biodiversity hotspot, with up to 30% of species endemic.

The Guardian, 2016, Australia’s vast kelp forests devastated by marine heatwave, study reveals.73

Today, more than 95 percent of eastern Tasmania’s kelp forests — luxuriant marine environments that provide food and shelter for species at all levels of the food web — are gone. With the water still warming rapidly and the long-spine urchin spreading southward in the favorable conditions, researchers see little hope of saving the vanishing ecosystem.

“Our giant kelp forests are now a tiny fraction of their former glory,” says Craig Johnson, a researcher at the University of Tasmania’s Institute for Marine and Antarctic Studies. “This ecosystem used to be a major iconic feature of eastern Tasmania, and it no longer is.”

The Tasmanian saga is just one of many examples of how climate change and other environmental shifts are driving worldwide losses of giant kelp, a brown algae whose strands can grow to 100 feet. In western Australia, increases in ocean temperatures, accentuated by an extreme spike in 2011, have killed vast beds of an important native kelp.

In southern Norway, ocean temperatures have exceeded the threshold for sugar kelp which has died en masse since the late 1990s and largely been replaced by thick mats of turf algae, which stifles kelp recovery.

In western Europe, the warming Atlantic Ocean poses a serious threat to coastal beds of kelp, and researchers have predicted “extirpation of the species as early as the first half of the 21st century” in parts of France, Denmark, and southern England. 

YaleEnvironment360, 2017, As Oceans Warm, the World’s Kelp Forests Begin to Disappear.74

Ecology and the environment

The ecological impact of fossil fuel mining increases as the largest, easiest to access, resources are depleted. A constant fossil fuel production rate requires increasing energy input, but also use of more land, water, and diluents, with the production of more waste.

Coal mining has progressively changed from predominantly underground mining to surface mining, including mountaintop removal with valley fill, which is now widespread in the Appalachian ecoregion in the United States. Forest cover and topsoil are removed, explosives are used to break up rocks to access coal, and the excess rock is pushed into adjacent valleys, where it buries existing streams. Burial of headwater streams causes loss of ecosystems that are important for nutrient cycling and production of organic matter for downstream food webs. The surface alterations lead to greater storm runoff with likely impact on downstream flooding. Water emerging from valley fills contain toxic solutes that have been linked to declines in watershed biodiversity. Even with mine-site reclamation intended to restore pre-mined surface conditions, mine-derived chemical constituents are found in domestic well-water. Reclaimed areas have been found to produce little if any regrowth of woody vegetation even after 15 years, and, although this deficiency might be addressed via more effective reclamation methods, there remains a likely significant loss of carbon storage.

Oil mining has an increasing ecological footprint per unit delivered energy because of the decreasing size of new fields and their increased geographical dispersion; transit distances are greater and wells are deeper, thus requiring more energy input. Useful quantitative measures of the increasing ecological impacts are provided by the history of oil development in Alberta, Canada for production of both conventional oil and tar sands development. The area of land required per barrel of produced oil increased by a factor of 12 between 1955 and 2006 leading to ecosystem fragmentation by roads and pipelines needed to support the wells. Additional escalation of the mining impact occurs as conventional oil mining is supplanted by tar sands development, with mining and land disturbance from the latter producing land use-related greenhouse gas emissions as much as 23 times greater than conventional oil production per unit area, but with substantial variability and uncertainty. Much of the tar sands bitumen is extracted through surface mining that removes the ‘‘overburden’’ (i.e., boreal forest ecosystems) and tar sand from large areas to a depth up to 100 m, with ecological impacts downstream and in the mined area. Although mined areas are supposed to be reclaimed, as in the case of mountaintop removal, there is no expectation that the ecological value of reclaimed areas will be equivalent to predevelopment condition. Landscape changes due to tar sands mining and reclamation cause a large loss of peatland and stored carbon, while also significantly reducing carbon sequestration potential. Lake sediment cores document increased chemical pollution of ecosystems during the past several decades traceable to tar sands development and snow and water samples indicate that recent levels of numerous pollutants exceeded local and national criteria for protection of aquatic organisms.

Gas mining by unconventional means has rapidly expanded in recent years, without commensurate understanding of the ecological, environmental and human health consequences. The predominant approach is hydraulic fracturing (‘‘fracking’’) of deep shale formations via injection of millions of gallons of water, sand and toxic chemicals under pressure, thus liberating methane. A large fraction of the injected water returns to the surface as wastewater containing high concentrations of heavy metals, oils, greases and soluble organic compounds. Management of this wastewater is a major technical challenge, especially because the polluted waters can continue to backflow from the wells for many years. Numerous instances of groundwater and river contamination have been cited. High levels of methane leakage from fracking have been found, as well as nitrogen oxides and volatile organic compounds. Methane leaks increase the climate impact of shale gas, but whether the leaks are sufficient to significantly alter the climate forcing by total natural gas development is uncertain. Overall, environmental and ecologic threats posed by unconventional gas extraction are uncertain because of limited research, however evidence for groundwater pollution on both local and river basin scales is a major concern.

Hansen et al., 2013, Assessing ‘‘Dangerous Climate Change’’: Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature.75

Astoundingly, despite this predicament, civilisation continues to rapidly increase CO2 emissions, as detailed in Part 1. What will it take for emissions to instead decline? But even that change, seemingly insurmountable for civilisation, will now be inadequate as explained in Part 3.

  1. UN Secretary-General’s press encounter on climate change()
  2. Professor James Hansen’s warning of multi-metre sea level rise in The Guardian()
  4. p. 54, box 1.1, M. R. Allen, O. P. Dube, W. Solecki, F. Aragón–Durand, W. Cramer, S. Humphreys, M. Kainuma, J. Kala, N. Mahowald, Y. Mulugetta, R. Perez, M. Wairiu, K. Zickfeld, 2018, Framing and Context. In: Global warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [V. Masson-Delmotte, P. Zhai, H. O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J. B. R. Matthews, Y. Chen, X. Zhou, M. I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, T. Waterfield (eds.)]. In Press.()
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  11. NASA Global Ice Viewer()()()()
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  18. The difference between extent and area is explained at This states “A simplified way to think of extent versus area is to imagine a slice of swiss cheese. Extent would be a measure of the edges of the slice of cheese and all of the space inside it. Area would be the measure of where there is cheese only, not including the holes. That is why if you compare extent and area in the same time period, extent is always bigger. Scientists at NSIDC report extent because they are cautious about summertime values of ice concentration and area taken from satellite sensors. To the sensor, surface melt appears to be open water rather than water on top of sea ice.”()
  24. Walt Meier, a sea ice expert at the National Snow and Ice Data Center()
  25. Veerabhadran Ramanathan is a climate expert at the Scripps Institution of Oceanography who was the discoverer of the role of chlorofluorocarbons (or CFCs) in not only destroying the ozone layer but also amplifying global warming. Refer to
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  57. Updated figures:
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