The mission of The 2050 Project is to provide accurate, useful, long-range forecasts and information about the future of the planet. Our favored forecast interval is to 2050 and beyond, because we believe that shorter-range forecasts cannot portray the magnitude of our impending problems, and thus can only guide half-steps toward solution.

Understanding what we have done to this planet is difficult, particularly with the obfuscation offered by the energy industry and the complexity of the evidence. But understanding what will happen in the near future is even tougher, because it is clouded by reasonable uncertainty, wishful thinking, and the fact that this is the first time in the planet's history that any species has had any impact on the climate, or caused the extinction of even one other species.

The focus of this document is tipping points in the our planet's climate. Our species has been increasingly alarmed by the extent of climate change that has already occurred. Some worry about the continued unwanted changes that might occur even with "improvement" in human activities. But few of us believe that the future of the planet might reach a Tipping Point of irreversible change, where nothing that humans do can prevent an unwanted future from unfolding. And almost no one seems to believe that such a tipping point occurred a decade ago, and that it is already too late to "save the planet." At the moment, I am the most pessimistic of us all.  In this paper, I will outline evidence that several tipping points have already occurred.

The notion that the planet's climate has now reached a tipping point, and has begun to change on its own, is conjecture. We do not have first-hand experience with climatic tipping points, and few researchers have focused on them.  But there are reasons to think a tipping point has been reached:

• Again and again, climate models have been proven to be too optimistic. For instance, a model forecasting temperature change from carbon dioxide levels might find that actual temperatures in the last decade have risen faster than the model predicted.  Such models, it could be argued, have omitted the positive feedbacks that bring us to a tipping point.
• There is strong geological evidence that under conditions similar to the present, when greenhouse gases reached high levels, tipping points were triggered and climate changed dramatically.

This document will summarize what we know about what is happening to our planet. As an outline of the future, it will be revised bit-by-bit, day after day. Information in it will draw from sources listed in the Bibliography, all of which are highly recommended reading. We start with a look at some basic concepts, to understand the forces that are at work on the future of our climate.

Tipping Points

Complex systems such as global climate have many, many factors which influence them. Some of these influences are positive feedbacks -- effects which are strengthened by some factor, which in turn strengthens that factor.  And some are negative feedbacks, which help dampen the influence of some factor.

A negative feedback of concern is the possible effect of the melting polar ice on the "ocean conveyer belt".  As the ice melts, it creates fresh water, which has a lower specific gravity than salt water.  A large pool of freshwater off Nova Scotia could force the saltier gulf stream down, effectively bringing the current to a halt.  This is believed to have happened once before, when the giant lake occupying the middle of North America thawed, ice dams broke, and fresh water poured into the Atlantic, triggering an ice age.  There are signs that the gulf stream is slowing, and this negative feedback should be of concern.

The current pattern of global warming is a departure from the previous trend of global cooling, and appears to be a human-induced interruption in that trend. Global warming can trigger a number of positive feedbacks, that make the earth warm even faster.  Each of these factors can serve as a tipping point for irreversible climate change; in combination, they could overwhelm the cooling impact of a stopped ocean conveyer belt.  Here are the key positive feedbacks:

albedo

As we note below, all objects absorb some light, reflect some light. The more light that is reflected, the higher the object's albedo. snow has a high albedo, liquid water a much lower albedo. When a snowy area is warmed, and the snow melts, the albedo decreases, more sunlight is absorbed and becomes heat, and the temperature rises still further. Every bit of ice in the arctic thus helps keep things cool, and every bit of open water helps warm things further. Albedo plays a big role in helping an ice age keep its cool, and in preventing ice from even forming in warm periods, such as the Eocene.

The melting of arctic ice and increase in the area of the Arctic that is ice-free on any given day is having the biggest change on the earth's average albedo, but there are other factors too: increases in soot found on the ice of Antartica are helping the ice there melt faster. Warmer temperatures in areas where snow once fell are now causing those areas to experience rain, or quicker snow melts.

Slippery Slopes: Water under Glaciers

thawing permafrost

Permafrost is soil that is frozen year-round. Some of this soil is the visible ground and below, but there is also much permafrost buried beneath the Arctic sea. In normal permafrost, soil several inches below the surface never exceed freezing at any time of the year, though the very top centimeter or two may thaw in the summer.

Until recently, the Arctic was a carbon sink, a rich, vast reservoir of decayed vegetation storing carbon from past ages.  Scientists estimate that the Siberian tundra contains as much buried organic matter as the world’s tropical rain forests.^[9]

But a thaw in the permafrost began in 2003 or earlier. With that thaw, the Arctic will become another carbon source, and the stored carbon will be released in the form of  CO₂  or methane.

Impact: The immediate impacts of thawing permafrost are ecological, including "destruction of trees and loss of boreal forests; expansion of thaw lakes, grasslands, and wetlands; loss of habitat for caribou and terrestrial birds and mammals; additional habitat for aquatic birds and mammals; increased coastal and riverine (along the banks of rivers) erosion; blocking of streams important for salmon spawning; increased slope and soil instability, landslides, erosion; and development of talik (a year-round thawed layer of what was formerly permafrost), and increased water table depth"^[7] The infrastructure of Siberia and Alaska will gradually collapse as buildings topple, pipelines crack, and roads sink. But long-term, a warming soil will resume the decomposition that had been frozen in time, producing massive releases of CO₂ and methane. (In dry areas, as the permafrost melts, CO₂ will be the primary gas released, but in wetter areas, methane -- a more dangerous greenhouse gas -- will be the form in which released.^[7])

Potential Magnitude of Impact: The shallow Siberian Shelf alone covers 580,000 square miles, and is estimated to contain about 12 times the methane now found in the atmosphere. If all of the methane of the Arctic were to be released, the effect would be comparable to burning all recoverable stocks of coal, oil, and natural gas.^[9] There is evidence from past geological cycles that sudden releases of methane have triggered runaway cycles of climate upheaval.

Date Triggered: the permafrost has been warming over the past century, but most rapidly in the past decade, when ground temperatures in Svalbard, Norway rose four times as much as they did in the prior century.  Warming permafrost appears to have been first reported by the press in 2004^[7].

• Scientists report that permafrost has been warming in Alaska for more than a century. In northern Alaska, the 4-7°F. warming that has occurred in the last century has still not reached a thawing temperature,  but south of the Yukon River and on the south side of the Seward Peninsula, permafrost was thawing in 2003. ^[8]
• Not coincidentally, "until 2003, concentrations of methane had remained relatively stable in the Arctic Ocean and the atmosphere north of Siberia. But then they began to rise. [In the summer of 2003] scientists taking part in the six-week International Siberian Shelf Study discovered numerous areas, spread over thousands of square miles, where large quantities of methane — a gas with 20-times the heat-trapping power of carbon dioxide — rose from the once-frozen seabed floor. These “methane chimneys” sometimes contained concentrations of the gas 100 times higher than background levels and were so large that clouds of gas bubbles were detected "rising up through the water column" from sub-sea permafrost, indicating that the sea bottom might be melting and freeing up this potent greenhouse gas."^[9]
• In May 2005, Katey Walter of the University of Alaska Fairbanks told a meeting in Washington of the Arctic Research Consortium of the US that she had found methane hotspots in eastern Siberia, where the gas was bubbling from thawing permafrost so fast it was preventing the surface from freezing, even in the midst of winter.^[10] In August 2005, Sergei Kirpotin and Judith Marquand reported that one million square kilometers of a frozen peat bog covering the entire sub-Arctic area of Western Siberia had started to melt in the last three to four years [2001 or 2002]. New calculations showed the levels of methane emissions from northern wetlands 10 to 63 percent higher than the previous estimates. Larry Smith of the University of California, Los Angeles, estimates that the west Siberian bog alone contains some 70 billion metric tons of methane, a quarter of all the methane stored on the land surface worldwide. These two reports in 2005 suggest that thawing of the frozen peat bogs occurred some time prior to 2005. ^[10]

I conclude that the tipping point for warming due to thaws in the permafrost began in 2003.

Drought-induced Fire in the Amazon, American West, Mediterranean, Indonesian Peat

Changes in climate brought on by El Niño and other forces, has recently led to prolonged droughts in parts of the world. Drought seems invariably accompanied by fire, and fire transforms the stored carbon of plants, peat, and soil to CO_2.

Recent El Niños have occurred in 1986-1987, 1991-1992, 1993, 1994, 1997-1998, 2002-2003, 2004-2005 and 2006-2007. With El Niño comes drought to many parts of the world. Areas affected by drought and fire include Peru, Brazil, Ecuador, the Amazon, Australia, Papua New Guinea, Indonesia, Irian Jaya, Singapore, Philippines, China, North Korea, cyprus, Sahel, Cape Verde, Gambia, Senegal, Tanzania, Kenya, Botswana, Mpumalanga, Zambia, Zimbabwe, Mozambique, Namibia, Malawi, and Madagascar.

El Niño is triggered by unusually warm water in the Pacific ocean, occurring near the beginning of the year. Some scientists have speculated that a warmer atmosphere is likely to produce stronger or more frequent El Niños, based on trends observed over the past 25 years. As El Niño leads to drought and fire, it produces CO_2.which leads to more warming. ^[11]

Basic Concepts

To understand what is happening to our world, it will help to review some important concepts involved in the changes.

acidity, ocean. Under normal conditions, the ocean has a neutral pH. As the carbon dioxide of the air rises, the carbon dioxide dissolves in the ocean, where it joins with water to form carbonic acid. When carbon dioxide is added to the oceans gradually, chalk-forming organisms such as coccolithophorids (a kind of phytoplankton, at the bottom of many food chains) and the foraminifera use it to form calcium carbonate -- chalk -- which settles to the bottom when the organisms die. Added gradually, the ocean buffers excess carbon dioxide: the chalk can buffer the carbonic acid. But when carbon dioxide is added rapidly, the increase in ocean acidity results in grave danger to everything with a calcium-based shell, such as snails, clams, oysters, squid, coral, and coccolithophorids. All of these organisms become part of the buffering system, and their shells dissolve. Because of the sudden surge in carbon dioxide, our oceans are now more acidic than they have been in the past 100 million years. (Our current increase in carbon dioxide is 100 times as fast as it has ever been on the planet.)

albedo. All objects absorb some light, reflect some light. The more light that is reflected, the higher the object's albedo. Snow has a high albedo, liquid water a much lower albedo. When a snowy area is warmed, and the snow melts, the albedo decreases, more sunlight is absorbed and becomes heat, and the temperature rises still further. Every bit of ice in the arctic thus helps keep things cool, and every bit of open water helps warm things further. Albedo plays a big role in helping an ice age keep its cool, and in preventing ice from even forming in warm periods, such as the Eocene.

air pollution.

anoxia. Lacking oxygen. When oxygen levels become too low, aerobic life dies, and may be replaced by anaerobic life. In oxygen-deficient oceans, deep-sea anaerobic bacteria proliferate, and produce hydrogen sulfide.

biodiversity. The number of species, or number of species in an area. Species survive with climate stability, and disappear with climate change. Today's great biodiversity is made possible by a climate that has been stable for the past 8,000 years. Recent climate change accounts for some of the recent extinctions (though most recent extinctions are the result of habitat loss or degradation, or overhunting.)

black shale. A layer of rock with fine lamination and almost no fossils from the ocean floor, made from sediment deposited on an ocean bottom devoid of oxygen. Such shale may contain fossils from plants and animals living at the surface, suggesting that it was created at a time when the deep sea was anoxic, but there was still oxygen at the surface, and the ocean was thus unmixed or stratified. Fossils found in such shale are often well preserved, because of the absence of bacteria to aid in their decomposition after death. The black color of this shale comes from anerobic bacteria that consume sulfur and produced hydrogen sulfide. Black shale forms at the bottom of a Canfield ocean.

blooms. The sudden proliferation of aquatic microbes or algae, often causing a change in water color and usually consuming all of the available oxygen. Blooms are generally toxic, if for no other reason than they produce anoxia. Blooms in the Gulf of Mexico are regular summer-time events, feeding on the fertilizer washing off farmland and carried down the Mississippi, and leaving the Gulf an increasingly large dead zone. A world-wide toxic bloom of microbes that produced hydrogen sulfide occurred at the P-T (Permian-Triassic) boundary, possibly contributing to the mass extinction that occurred.

boundary clay. Dark rock, absent chalky skeletons, that signifies that a mass extinction has occurred and that separates one geological era from the next. Boundary clays may contain high concentrations of fine soot, as in the K-T boundary clay, suggesting that large portions of the earth were simultaneously burning. They may contain iridium, shocked quartz grains, and spherules, suggesting impact from a large boloid. Finally, plants prefer a diet of carbon dioxide built from carbon-12 to that built from carbon-13, and photosynthesis converts this CO₂ to carbon and oxygen... so when a high ratio of carbon-13 to carbon-12 is found, it can be assumed that plants were busy using the carbon-12. Boundary clays don't show such high ratios, indicating a disuption to photosynthesis.

buckminsterfullerenes

buffering systems A buffering system is one which is able to maintain an approximately stable pH by moderating changes that would otherwise make things more acidic or more basic. As carbon dioxide (CO₂) dissolves in the ocean, it forms carbonic acid, lowering pH. In buffering, carbonic acid (H₂CO₃) can lose its hydrogen ions and combine with calcium ions to form calcium carbonate (CaCO₃) and reduce the acidity caused by these free hydrogen ions. Calcium carbonate can precipitate and settle on the bottom, or can dissolve in the ocean water. The oceans are important in buffering our CO₂ emissions: nearly half of all carbon emitted since the start of the Industrial Revolution has been absorbed by the ocean. ^[2]

Buffering maintains the pH of the ocean at an average of 8.1 with little variation over time. But buffering is a slow process, and we've been adding CO₂ to the atmosphere and ocean rapidly. The slow natural pace of buffering cannot offset the ocean's rapid acidification from carbon dioxide absorption.^[1] Since the pre-industrial era, the average pH of the ocean has dropped by 0.1 -- a 30% increase the the average hydrogen ion concentration of the ocean. ^[3] pH levels might fall by as much as 0.5 units by 2100, which would be equivalent to a three-fold increase in the hydrogen ion concentration since pre-industrial times.^[1] The acidification of the oceans reduces the ability of phytoplankton to produce shells and grow, and destroys coral reefs. One recent study concludes that acidification has the potential to trigger a sixth mass extinction event and to do so independently of anthropogenic extinctions that are currently taking place.^[4]

calcium carbonate

Canfield ocean

carbon cycle

carbon dioxide. Primary causes of mass extinctions are linked in various ways to the carbon cycle in general and ocean chemistry in particular with clear association with atmospheric carbon dioxide levels^[4] We are moving toward higher carbon dioxide levels than the world has seen in the past 60 million years -- which occurred in the greenhouse extinction of the Eocene.

catastrophism

chalk

chlorofluorcarbons

conveyer current. Ocean currents carry warm water up from the Gulf of Mexico, along the east coast of the U.S., across to Europe, and back down toward Africa. Similar currents flow around the entire earth, aided by prevailing winds and by the rotation of the earth. Such ocean currents resemble a convoluted conveyer belt, helping to warm areas that would otherwise be cold, and helping to cool areas that would otherwise be hot.

conveyer disruption hypothesis. The conveyer current is disrupted when there is a massive sudden addition of fresh water to the system, because fresh water is lighter than salt, so the salt water of the conveyer is forced down, below the fresh water, stalling the forward movement of the conveyer current. We don't know for sure what happens next. Two extreme (and extremely different) possibilities are worth considering:

• The conveyer stops. The conveyer seems to have stalled at the end of the last ice age, when the ice dams that held back the huge lake in the interior of North America suddenly burst, releasing a torrent of fresh water into the North Atlantic. When the conveyer is turned off, cold areas no longer get their flow of warming ocean current, and they begin to chill. So stalling the ocean conveyer can bring on an ice age. Such a conveyer disruption could also occur if our current warming trends melt ice near the north pole, creating a flood of fresh water... which would, in turn, disrupt the conveyer and begin a period of global cooling!
• The conveyer continues, but following a new route: warm salty water meeting cold fresh water is forced down, but slowly moves away as it nears the bottom. Because warm water can carry less oxygen than cold, such a shift, if continued, could create an anoxic ocean, eventually becoming a Canfield ocean.

deforestation

Eocene epoch. The Eocene epoch was so hot that there were no polar ice caps. Sea level was about 150 feet higher than it is today. Palms and crocodiles lived throughout the world, including Canada and northern Europe.

extinction, mass. A paper in Nature, 2005, predicted that climate changes caused by our global warming would lead to the extinction of more than a million species by 2050.

greenhouse effect. The warming of the planet that results from the accumulation of greenhouse gasses in the atmosphere. The predicted effects include temperature increases (particularly in midlatitude, temperate, and continental interior regions), decreases in precipitation in these regions, and increases in the severity of storms.

greenhouse gas. Any gas in the atmosphere that absorbs infrared radiation, and radiates it back to earth. Such gases permit sunlight to penetrate and reach the earth, but trap radiated heat, much like the action of a greenhouse. Greenhouse gases include carbon dioxide, methane, chlorofluorocarbons, sulfur dioxide, and nitrogen oxides. The level of greenhouse gases in the atmosphere has increased since the beginnings of human agriculture, dramatically since the start of the industrial revolution, and even more dramatically in recent decades. Most climate models predict that the amount of greenhouse gasses in the atmosphere will double in the coming 100 years.The buildup of greenhouse gases is the leading cause of global warming.

hydrogen sulfide. A poisonous gas emitted by volcanos and produced by anaerobic bacteria. The amount of hydrogen sulfide entering the late Permian atmosphere was likely about 2,000 times greater than the small amount emitted by today's volcanos.

irreversible change

Jurassic-Cretaceous mass extinction

mass extinction. see extinction, mass

melting. The rate at which a glacier melts is not perfectly correlated with rising temperature. Initially, a rise in temperature produces melting that contributes to local climate change, which can increase local rainfall or snowfall, feeding the glacier that has melted and keeping its volume nearly the same. So the edges melt at first, and the center may grow in size. But as this happens, a temperature may be reached where water can remain liquid below the ice. This liquid water speeds the warming of the glacier, and causes it to float... downhill, toward the sea.

methane. One of the most potent of the greenhouse gases. The P-T (Permian-Triassic) event, which had rapid global warming, sudden deforestation, and massive extinctions, may have been marked by large, sudden methane releases.

ocean acidity. see acidity, ocean

Paleocene Thermal Event.

positive feedback loop. A change in a system that causes that system to move in the direction of the change. For instance, if heat is added to ice, it melts, and as liquid water it absorbs more heat -- reflects less heat -- than ice does, so that adding a little heat to a frozen area allows the sun to add more. As a writer in Wikipedia notes, "The end result of a positive feedback is often amplifying and "explosive", i.e. a small perturbation results in big changes. This feedback, in turn, will drive the system further away from its original setpoint, thus amplifying the original perturbation signal, and eventually become explosive because the amplification often grows exponentially (with the first order positive feedback), or even hyperbolically (with the second order positive feedback)... In some cases (if not controlled by negative feedback), a positive feedback loop can run out of control, and can result in the collapse of the system. "^[6]

P-T (Permian-Triassic) event. The end of the Permian period 252 million years ago saw the greatest mass extinction in the geological record. It is estimated that 95% of all species of marine animals became extinct. On the land, the impact was so great that no coal was laid down for at least 6 million years afterward.

This "event" is marked by large numbers of fungi spores at the boundary, coal below, and no coal above. The fungi spores suggest that the fungi were feeding on dead, rotting plants, and the lack of coal above this boundary indicates a massive loss of plant life. Ocean sediments suggest massive erosion, which would come with a loss of forests.

Many theories have been advanced as to the cause, including a fall in sea level, severe climate change induced by methane release, intense volcanism, impact by a bolide, overturn of a stratified, sulfidic ocean, or a combination of these. Increasing evidence indicates that the global ocean at this time was anoxic, and likely sulfidic, for a period of time before and through the boundary. Whatever the causes, the extinction event was accompanied by dramatic changes in seawater chemistry including excursions in the isotopic compositions of organic and inorganic carbon. The ratio of carbon-13 to carbon-12 decreases in this boundary, consistent with the catastrophic release of 4 trillion tons of methane from the floor of a stratified ocean.

sea level

tipping point

T-J (Triassic-Jurassic) event

ultraviolet radiation

Climate States

A "stable state" for our climate is one which remains constant, buffering various forces that would change it.  It seems that earth's climate has three stable states:  too hot, too cold, and just right. These states may be characterized as follows:

• Too hot. The earth as hot house can occur when a build-up of greenhouse gases occurs. Volcanism releases greenhouse gases and ash; the ash blocks the sun and the earth cools. With enough ash (volcanism lasting tens of thousands of years), global cooling can result, with the rapid formation of polar ice caps and glaciation. When the volcanism subsides, the aerosols settle, the sky becomes clear, and the greenhouse gases take over, rapidly melting the ice and flipping the earth toward hot house.
• Too cold. The earth as ice house occurs on its own, naturally, from a combination of causes. Variations in earth's orbit can cause more or less heat to fall on the earth. If summers are cool enough that not all of the previous winter's ice is melted, the planet may become cooloer. When continents are located at a pole (as Antactica does today), or a polar sea is almost land-locked (as the Arctic Ocean is today), or the equator is covered by a supercontinent, the flow of warm water from the equator to the poles is blocked, helping polar ice to form.
  • Technically, we are living in an "ice age" because extensive ice sheets may be found on earth (in Greenland and Antarctica). The last Glacial Maximum within this ice age took place about 18-20,000 years ago, when a mile-thick glacier stretched across North America. Albedo helped the ice stay cold, reflecting most of the sun's heat back into space. The low temperature meant that there were few plants, and thus little carbon dioxide available to warm the earth. 
  • "Too cold" can come about too quickly: about 70,000 years ago, a supervolcano in Indonesia darkened the world's sky with dust and sulfur, blocking out the sun and causing the world's temperature to plunge.
• Just right. For the past 8,000 years, this world has had a climate much like that of today, one which favored abundant biodiversity and biomass. But this stable climate is possibly an anomaly in the history of the earth, which is prone to tipping into "too hot" or "too cold" for a prolonged period.

Mass Extinctions

Exactly what happens in a mass extinction depends a bit on the triggers.

• For an extinction caused by plume tectonics (a giant pulse of heat rising toward the surface of the planet as a plume), the effect would be sudden cooling as the sky darkened with volcanic ash. "Even a short-lived catastrophe among land plants and surface plankton at sea would drastically affect normal food chains. Large animals would have been vulnerable to food shortage, and their extinction after a catastrophe seems plausible. In the oceans, invertebrates living in shallow water would have suffered greatly from cold or frost, or perhaps from CO2-induced heating. High-latitude faunas and floras in particular were already adapted to winter darkness, though perhaps not to extreme cold. Thus, tropical reef communities could have been devastated, but high-latitude communities could have survived much better."^[5]
• A mass extinction caused by bolide impact would be similar: a cloud of dust would darken the sky, and until it cleared, photosynthesis would stop. Death would roll up the food chain: plants and phytoplankton, herbivores, carnivores.
• For the mass extinction that may have begun a decade or more ago, the future is less certain. Our planet may have been on its leisurely way toward another ice age when man's agricultural age began 8,000 years ago. Such a prediction comes from an understanding that the earth's orbit around the sun changes at regular intervals -- Milankovitch cycles -- and that these changes impact the intensity of the sun on the earth, in turn impacting plant growth, CO₂ production, and the greenhouse effect. So if the earth was moving toward an ice age when our species came along, we've have certainly reversed that trend -- at least temporarily. But the stored carbon is finite, and sometime not too long from now, we will run out of oil, out of coal, and out of wood. When we are out of wood, the current mass extinction will already be quite advanced.

Some computer models predict that human-generated greenhouse gases will heat the earth, postponing the next glaciation by as much as 50,000 years. Other computer models predict that such warming will, paradoxically, trigger global cooling and increased glaciation. I think it likely that we are in store for both heating and cooling, in that order. But I don't think any of us will live to see the cooling. Here's what is most likely:

1. As we release greenhouse gases, the arctic will warm, and the polar ice will melt. This fresh water will block the flow of the Gulf Stream, causing it to come to a stop.
2. Once the ocean conveyer belt has come to a halt, the impacts on land will vary. The rainforest, western U.S., and Mediterranean will begin to dry, and be consumed by forest fires, releasing vast amounts of CO₂ -- These areas will become uninhabitable. The British Isles will lose the moderation of weather that the ocean conveyer delivered, and suffer hot summers and cold winters. Throughout the east coast of the U.S., weather patterns will stall for longer periods, bringing alternations from flood to drought.
3. The new warmth in the arctic will melt the permafrost, releasing huge amounts of CO₂ and methane.
4. The release of CO₂ and methane from forest fires, burning peat swamps in Indonesia, and melting permafrost will act as a positive feedback loop, producing runaway warming.
• Throughout the world, storms will become unimaginably intense.
• With all ice melted, our oceans will rise, drowning all coastal cities. Low-lying areas like Bangladesh and Holland and Florida will be gone.
• Our oceans will become far too acidic for corals or phytoplankton, and the bottom of the ocean's food chain will be gone.
• Almost equally quickly, our oceans will become anoxic, and nearly all life in them will die.
• On the land, the heat and fires will reduce most areas to a look now found in parts of central Australia: near lifeless desert.
5. Unknown, but likely, are three final blows:
• stored methane in the oceans will be released in giant bubbles, increasing the greenhouse effect.
• Sulfur-based bacteria, that don't need oxygen, will begin to rule the seas, producing upwellings of poisonous hydrogen sulfide, killing everything in their path, and serving as still another greenhouse gas.
• The hydrogen sulfide will destroy the ozone layer. Without an ozone layer, only those animals that live in burrows and are active at night will have a chance to survive mutations triggered by the ultraviolet penetrating the atmosphere. As in parts of central Australia, our new life may be rats, snakes, and flies.
6. Eventually, most of the stored carbon on earth will have been released as CO₂, and no further warming will occur. The planet will be stable -- and remarkably unpleasant -- for many million years, until the natural effects of the earth's wobbly orbit finally begin to create seasons again.

Of course, there will be smaller scale events along the way. The polar bears will die. The penguins will die. The sea birds will die. But there will be some more unpleasantness involving humans:

• In less than 50 years, Pakistan will have a doubled population and no water. The glaciers that feed the Indus River will be gone, the Indus will be dry, and Pakistanis will look to India for water. This will not be a comfortable situation for either nuclear power.
• The water tables in the Middle East will have dropped too far to be usable, and water will come only from expensive desalinization processes. Agriculture will nearly cease, and populations will be on the move.
• In 100 years, much of the populations of Florida and the U.S. west of the Mississippi will have moved to the east, to avoid the fires and flooding. In the east, population will far outstrip the water supply, and rivers like the Potomac and Hudson won't reach the sea.

Not Believable

The suggestion that a tipping point has already been reached, and the extreme changes in our climate have already been set in motion -- irreversible motion -- is not acceptable. Not believable. Here are some of the forces working against belief in such a notion:

1. Humans as Superman.  People believe that when organized and motivated, humans can do anything. Anything broken can be fixed. Any problem can be solved.  So we can feed the planet if we just buckle down and work at it.  And we can reduce carbon emissions and thus stop global warming if we all pull together. And if there is a plausible plan, then things are as good as done.
2. The Pollyanna Principle. People want good news. They prefer to hear good news. Too much bad news, and they just can't handle news at all.
3. Gradual change undetectable, unbelievable. If the world is warming, why were Britain's last two summers so mild and damp?, some wonder.  Humans focus so much on day-to-day fluctuations that small shifts in average rainfall or temperature go undetected. And many choose to believe that what they cannot sense does not necessarily exist. Our planet is full of people who do not believe the planet is warming at all.
4. Good people don't do bad things. Us little humans couldn't change the weather. Many folks want to find evidence of climate cycles or sun spots or anything that could account for observed climate change, in hopes of sustaining their belief that we are not at fault. 
5. Sudden change is unimaginable. Climate tipping points have been reached perhaps only 10 times in the last 100 million years. Why should we believe that one might happen (or have happened already) in our lifetime?
6. Humans don't do real math well. Regardless of our mathematical training, we don't have any direct experience on things very big or very small.  One hundred million years doesn't seem much longer than a thousand years, and a degree doesn't seem like much at all. Most everyone has trouble with simple questions such as "what is the average temperature", answering with "it depends...". Too much variability (noise) and we lose the signal. And so a few cool days makes it harder to see a general increase in temperatures.

Bibliography

• Diamond, Jared. Collapse. How Societies Choose to Fail or Succeed. Viking. New York. 2005. Amazon.com.  
• Gore, Al. An Inconvenient Truth. The Planetary Emergency of Global Warming and What We Can Do About It. Rodale. Emaus PA. 2006. Amazon.com
• Lynas, Mark. Six Degrees. Our Future on a Hotter Planet. National Geographic. Washington D.C. 2008. Amazon.com 
• NASA. 'Tipping Points' High-Resolution Multimedia for the 2007 AGU Press Event.
• Pearce, Fred. With Speed and Violence. Why Scientists Fear Tipping Points in Climate Change. Beacon Press. Boston. 2007. Amazon.com
• Ward, Peter D. Under a Green Sky: Global Warming, the Mass Extinctions of the Past, and What They Can Tell Us About Our Future. Collins. N.Y. 2008. Amazon.com 

Footnotes

1. ↑ Caldeira K. and Wickett M. J. (2003) "Anthropogenic carbon and ocean pH ." Nature 425 Page 365
2. ↑ Doney, S.C. 2006. "The dangers of ocean acidification." Scientific American: 58 – 65.
3. ↑ Brewer, P.G. 1997. Ocean chemistry of the fossil fuel CO2 signal: the haline signal of “business as usual”. Geophys. Res. Lett. 24: 1367 – 1369.
4. ↑ Veron, J.E.N. "Mass extinctions and ocean acidification: biological constraints on geological dilemmas" Coral Reefs. Volume 27, Number 3 / September, 2008
5. ↑ Cowen, Richard. The Permo-Triassic (P-T) Extinction. March, 2002. Online.
6. ↑ Positive feedback. Wikipedia. October 22, 2008.
7. ↑ Bentley, Molly. Earth's Permafrost Starts to Squelch. BBC News. December 29, 2004.
8. ↑ US National Assessment of the Potential Consequences of climate variability and Change Educational Resources Regional Paper: Alaska . US Global Change Research Program. October 21, 2003.
9. ↑ Stranahan, Susan Q. Melting Arctic Ocean Raises Threat of ‘Methane Time Bomb’ Environment 360 October 30, 2008.
10. ↑ Pearce, Fred Climate warning as Siberia melts. New Scientist Environment. August 11, 2005.
11. ↑ Benestad, Rasmus & Raymond Pierrehumbert El Niño and Global Warming. RealClimate. Climate Science from Climate Scientists. May 17, 2006.