The last 12,000 years, the Holocene geologic era, has been a time of a remarkably stable climate. Humans have used this time to move from hunter-gathers, to agrarian societies, and eventually to forms of industrialization. Were we prudent in our use of the natural world it is possible this stability could be extended far into the future.
Today, however, we see the biosphere in a death spiral. We are losing entire ecosystems. The latest Living Planet Index from the World Wildlife Fund shows a decline in wildlife populations of 60% between 1974 and 2014. “The Insect Apocalypse” has entered environmental jargon. Over half the world’s forests have been lost. The damage to the biosphere is happening faster than anyone anticipated, even 10 years ago, and it is putting our very existence at risk.
As the earth’s largest habitat, the oceans cover about 71% of the surface of the earth and contain 97% of the earth’s water. They are home to the majority of earth’s plants and animals.
Since the oceans cover so much of the globe, they absorb the majority of the sun’s radiation. They are central to the climate system in their distributing heat via interaction with the atmosphere (evaporation), and their complex system of currents that transfer heat like conveyor belts. Scientists estimate that a complete circuit of these currents takes about 1000 years to complete.
Weather patterns on the earth are predicated in large part by the difference in temperature between the tropics and the poles. The equatorial regions of the earth receive higher levels of solar insolation. The heat generated here is typically transferred north and south toward the poles. This is accomplished by a pattern of air currents and water currents. In the polar regions, water cools and becomes saltier, and denser. It sinks and is replaced by warm water from the tropics. This system has been stable for more than 10,000 years, but the oceans are warming, inhibiting the typical transfer of heat as the temperature difference between the poles and the tropics diminishes.
The most topical ocean current system today is referred to as the Atlantic Meridional Overtuning Circulation (AMOC). The AMOC has been getting weaker as lighter, freshwater from melting ice in the polar region and Greenland invades the system. With weather patterns in the North Atlantic and its environs dependent on the AMOC, a slowdown could lead to hotter European summers, changing tropical rain patterns, and affect hurricanes along the US east coast.
In addition to absorbing most of the sun’s radiation, critically, the oceans act as a huge carbon sink. This is an active area of study by scientists today. We have known for many years that not all the CO2 generated on the surface goes into the atmosphere. Over the last two hundred years, as humans have burned fossil fuels, the oceans have been absorbing most of those carbon emissions and the heat generated by those green house gases.
A new report published in Nature6 shows that the oceans have absorbed “far more heat” than previously thought. The meaning of this is profound. While we generally focus on climate change when we think about the temperature of the earth, the more accurate measurement is the temperature of the oceans. If the oceans are warming faster than we thought, the earth is warmer than we thought.
Global warming is actually ocean warming. The heat absorbed by the oceans remains to heat the planet for decades to come. It leaves the oceans via melting ice shelves, evaporation, and direct heating of the atmosphere. It has dramatic implications for the climate at the poles as we shall see in the section on the cryosphere. As the oceans warm, they expand. In her new book, “Rising: Dispatches from the New American Shore,” Elizabeth Rush describes how large parts of the U.S. coastline will vanish underwater by the end of the century. Citing Hal Wanless of the University of Miami, south Florida will be at least 15 feet underwater by the end of the century.7
The implications for the health of the oceans would be higher acidification (lower pH) because of increased levels of CO2. Ocean calcifying organisms will be less able to build their carbonate structure. Thus, we see the damage to the Great Barrier Reef and other reefs across the world which provide homes for 25% of oceanic species. In addition, the marine food chain is put at risk. The base species of the marine food chain, phytoplankton, will be dramatically affected as effects on calcification, photosynthesis, nitrogen fixation, and other processes occur, leading to a traumatic change in marine communities. The results will propagate up the food chain.
Humans have always depended on the oceans as a source of food. However, the UN Food and Agriculture Organization finds 90% of world fish stocks overfished. A major contributor to this situation is the $20 billion a year in subsidies which benefit large fleets. Although global collaboration to eliminate these subsidies is ongoing since 2015, as yet no agreement has been accepted.
Huge dead zones are being created in the oceans. Every year more oil spills into the oceans from US coasts than was released by the Exxon Valdez into the Gulf of Alaska. Yet, oil is a relatively small part of the overall pollution which results primarily from agricultural runoff. About 80% of agricultural fertilizers (about 3.5 billion tons), mainly nitrates, drain into aquifers and rivers and eventually the oceans. The Mississippi River Valley drains about half the agricultural land in the US into the Gulf of Mexico.8
The organic waste is augmented by plastic pollution which was estimated 4 years ago to be about 8 million metric tons per year. The plastic is harming nearly 700 species in the oceans, from plankton to whales. (Source: Ocean Conservancy)
This video clip from The Graduate (1967) demonstrates once again how little time it has taken for plastics to pollute the earth. It is now estimated that by 2050, there will be more plastic than fish in the oceans.
The Cryosphere - The Arctic
The frozen part of the hydrosphere, the cryosphere, includes the ice at the poles and the world’s glaciers. It acts as the earth’s air conditioner. Of the 2.5% of the water on earth that is fresh water, 69% of it is frozen, and stored in the polar ice caps and glaciers. Of the remaining 31%, most of it is ground water, leaving only 1.2% as surface fresh water.
There is nothing more dramatic about recent changes in the earth’s system than developments in the cryosphere. The Arctic was last thought to have been ice free between 100,000 to 120,000 years ago. It is, however, warming at twice the rate of the rest of the planet, and is expected to be ice free in September (the warmest month) within the coming decade.
Because it is warming, the temperature differential between the northern and lower latitudes is diminishing. The polar jet stream which depends on this difference to maintain its position about the pole is weakening and wandering outside its normal circular pattern. The result is wild swings in the weather which have been evident during recent winters in the US.
As the Arctic warms and the ice there melts, the albedo (the amount of light reflected from a surface) of the area changes from a very reflective ice cover to the darker color of the ocean. The open ocean absorbs rather than reflects the sun’s energy. That additional energy results in more melting as the positive feedback loop continues.
This “Arctic Amplification” affects nearby land masses such as Greenland which a recent study found to be melting faster than at any time in the last 400 years.9
The warming also affects the permafrost in the northern latitudes which harbor an estimated 1.7 trillion tons of carbon. When it thaws, this carbon is released as CO2 and methane. Here again, we have a situation never faced by humans. We don’t know if and when this could occur, but methane releases are increasing. This is a potential time bomb which, even if it didn’t happen this century, could make the planet uninhabitable in centuries to come.
A recent NASA research project documents a new process which could enhance the release of greenhouse gases. The process referred to as “abrupt thawing” occurs in a type of Arctic lake known as a thermokarst. This research points to a new source of greenhouse gases that is not part of current climate models. First author Katey Walter Anthony of the University of Alaska Fairbanks: “We don’t have to wait 200 or 300 years to get these large releases of permafrost carbon. Within my lifetime, my children’s lifetime, it should be ramping up. It’s already happening but it’s not happening at a really fast rate right now, but within a few decades, it should peak.”10
A new report released March 14, 2019 by the UN Environment Programme projects that GHG emissions already emitted will lead to a warming in the arctic of 3 to 5 degrees Celsius by 2050 and 5 to 9 degrees by 2080. The warming of the Arctic permafrost is also “locked in.”11
The Cryosphere - Antarctica
The fifth largest continent, Antarctica is covered with ice that averages almost 2 km in depth. It was not always like this. Over hundreds of millions of years it has assumed its current shape and moved around the globe via tectonic plates; it was at times even sub-tropical in climate. The cooling of the continent began nearly 23 million years ago as it was isolated and circumscribed by the circumpolar current. It has been mostly covered by ice for about 15 million years.
While it has long been considered a stable ice sheet, recent evidence demonstrates that even the Antarctic is not immune to global warming. Significant changes are occurring to glaciers on both the western and eastern sides of the continent.
The Thwaites Glacier on the western edge near the Amundsen Sea is currently the subject of intense scrutiny. Sridhar Anandarrishnan, a Penn State scientist, has been visiting it since 2008. Glaciers are incredibly complex and current models about them are nascent. Recent trips to Thwaites have revealed that it is starting to destabilize.12
Thwaites acts like a plug, holding back huge amounts of upstream ice from moving to the ocean. Were it to collapse, it could produce a meter of sea level rise all by itself. With this background, it came as a huge shock to scientists when, in February 2019, a hole two-thirds the size of Manhattan and a 1,000 feet tall was discovered within the glacier.13
On the other side of the continent, a recent study suggests that the East Antarctic Ice Sheet may be melting at an accelerating rate. If this is confirmed, it would suggest that global warming has begun melting the entire cryosphere. All current predictions about sea-level rise this century would be inaccurate, with a multi-meter rise possible.14
The Cryosphere - Mountain Glaciers
There are about 150,000 glaciers spread across the globe. Over the last four decades they have diminished by the equivalent of a layer of ice 70 feet thick. Across Southern Asia, nearly 2 billion people and their major rivers depend on glacial melt for water. In China these include the Yangtze and Huang He (Yellow) Rivers. South of the Himalayas, the Ganges, Indus, Brahmaputra, and Mekong provide water to India, Pakistan, Laos, Thailand, Nepal, Cambodia, Myanmar, and Vietnam. These rivers play a central role in the ecology of each of these countries. China which does not reap the water from the monsoon rains is especially vulnerable and has undertaken a huge water reallocation project with enormous environmental impacts.
A recent report, The Hindu Kush Himalaya Assessment, finds that “at least a third of the huge ice fields in Asia’s towering mountain chain are doomed to melt due to climate change.”15 If climate change continues unabated, the loss will be two thirds by 2100.
The glaciers in South America are most at risk because of their location in warmer latitudes. Climate change is rapidly transforming these environments – the glaciers are retreating at their fastest rate in 300 years. With a dry season in parts of Peru and Bolivia of as long as six months, the supply of water from the glaciers has become a contentious issue between a growing population and corporate interests who use the water to power mining activities and large-scale agricultural irrigation.
When the subject of climate change is discussed, it generally focuses on what is happening to the atmosphere. As we have already seen, though, there is much more going on than what is happening to our daily weather.
That said, the warming that is occurring to the troposphere creates much of the forcing that is affecting the planet. Dramatic weather events across the globe, huge and prolonged hurricanes and typhoons, unprecedented flooding and drought, and other weather events are evidence that, even in our short lifetimes, make it obvious that something has changed. Once again we need to think about how quickly this change has happened. In the course of a few generations, the climate has been redirected to a path from which there will be no return. We could have predicted another ice age in perhaps 50,000 years, but now that won’t happen.
The carbon dioxide in the atmosphere has for thousands of years been a benign and necessary contributor to the stability of the climate during the Holocene Era. Without naturally occurring greenhouse gases, which include CO2, the earth’s average temperature would be 0°F (-18°C). Since the last ice age, about 10,000 years ago, the level of CO2 has been remarkably stable at about 280 parts per million (ppm). This “interglacial period” and its stable and predictable climate have enabled humans to develop complex civilizations.
The greenhouse effect was first described in 1896 by Swedish scientist Svante Arrhenius. About 60 years later, Charles Keeling began collecting data on CO2 concentrations at the Mauna Loa Observatory in Hawaii. His data has become famous now as the “Keeling Curve” (see below) which documents the inexorable rise of CO2 concentration in the atmosphere. It wasn’t until 1988 when James Hansen’s testimony to Congress drew public attention to the issue. He stated that it was 99 percent certain that observed rising global temperatures were not a natural phenomenon, but rather caused by a buildup of carbon dioxide and other gases in the atmosphere.
In 1988 the CO2 level was 350 ppm. We are now just a bit beyond 30 years since that testimony and the latest CO2 concentration recorded at Mauna Loa is 415 ppm. Humans have put more than 400 billion metric tons of carbon dioxide into the atmosphere since 1751, and about half this total has been released since Hansen’s testimony.16
Global carbon emissions reached an all-time high in 2018 of 37.1 billion metric tons.
We are now on a path to a world humans have never experienced. The natural carbon cycle will eventually return it to the lithosphere, but the carbon dioxide we have already put into the atmosphere will remain there for hundreds if not thousands of years, essentially forever as far as humans are concerned. In addition, the heat that has been stored in the oceans will over decades be released into the atmosphere. Not often mentioned is that removing greenhouse gas (GHG) and its pollution from the atmosphere would remove a veil of particles that is shading the earth. It’s absence would lead to further warming. So even if we were to stop GHG emissions today we are already committed to increased warming.
You may have noticed that little attention has been paid here to the reports by the IPCC. Though the latest report of October 2018 was closer to the truth than previous reports, it still mentions the possibility of meeting the aspirations of the 2015 Paris Agreement on climate change by drastic cuts in GHG emissions during the next decade. It should be noted that meeting the goals of the 2015 accord will require the removal of carbon from the atmosphere, including technologies that are not yet available. Realistically, many who study the science are beginning to feel that the 1.5°C target is unattainable, and the the 2°C level should be considered a lower limit with a rise in temperature of 3°C to 4°C quite possible.
This is in part likely because the pledges by individual nations in the 2015 Paris accord, even if met, would lead to a 3°C rise. As of late 2018, most of the world’s major polluters are showing no indication of meeting even these modest goals.17
The Biosphere at Elevated Levels of CO2
The predictions of changes to the atmospheric temperature are based on the known correlation between CO2 concentrations and the earth’s temperature. While this relationship has been known for over 100 years, there remains some uncertainty about the exact amount of warming that will occur in response to an increase in CO2. This variable is referred to as “climate sensitivity” and refers to the amount of warming that will occur in response to a doubling of atmospheric CO2. The variation in estimates of climate sensitivity results from the uncertainties about climate feedback such as how water vapor, clouds, and surface reflectivity vary as the earth warms. Current studies suggest that this feedback will amplify warming.18
With no mitigation to GHG emissions, a recent study predicts that by 2030 the earth’s climate will most closely resemble that of the mid-Pliocene, some 3 million years ago.19 At that time, sea levels were more than 60 feet higher than today and the Arctic was forested and ice free. If carbon dioxide levels continue to climb through mid-century at their current rate, the earth could reach a state not seen for 50 million years. At that time the earth’s temperature was 10°C (18°F) warmer than today.20
These historic periods evolved over millennia and we are not going to see them reoccur within a decade or even two. The rate at which the earth is currently changing is, however, unprecedented, and represents a threat to civilization as we know it.
Several years ago, a documentary was produced that delineated the changes that would occur to the world as it warmed up degree by degree to 6°C. It’s a veritable horror story and still available, though already dated as climate change proceeds at an alarming rate. I will simply focus on what it would be like to live in a world of 3°C warming – a very plausible possibility within the lifetime of those who live through the century.
As a response to this situation, the Paris commitments are woefully inadequate. The “NDCs” in the chart are Nationally Determined Contributions, the pledges by individual countries. “Conditional” are just that, targets if some internal conditions are met. The vertical line is total GHG emissions with GHG emissions other than CO2 included as equivalent CO2.
Paris 2015 Accord
The bottom line is that we must reduce CO2 emissions by about 50% between now and 2030 and reach net zero by 2050. Though some still believe that this can be done, it will have to coincide with growth in the world population to almost 10 billion, the associated growth in global GDP, and large increases in the demand for food and energy.
Methane - The Joker in the Deck
The chart above regarding the 2015 Paris Accord shows that every year about 50 billion tons of “carbon dioxide equivalent” is added to the atmosphere. Of that total, 70% is CO2 and half the remaining 15 billion tons is methane. Methane(CH4) is created by microbes in the soil. It is released by sources both natural and man-made, among them animal digestion, fermentation in rice fields, fracking for natural gas, coal mines, festering bogs, and burning forests.
Though the quantity of methane in the atmosphere is much lower than that of CO2, methane is a much more potent GHG. Over 20 years, it is more than 100 times as effective in trapping heat than CO2. It is broken down in the atmosphere by oxidation producing CO2 and water vapor (both are GHG).
Scientists are concerned about a sharp rise in methane emissions since 2007. It’s not clear why this is happening, but there are several possible causes. Some suggest that fugitive leaks from fracking are to blame while others like Euan Nisbet of Royal Holloway, University of London point to “an increase in biogenic emissions, probably from wetlands and agricultural sources.”21
Nisbet’s research is for the period 2007 – 2014. His more recent research looks at the four years 2014 to 2017 and finds a further acceleration in the growth of methane emissions. Here again, the issue is so complex that no one factor can be singled out as the source. It could be the increase in anthropogenic emissions from mining and gas production, natural sources (wetlands and/or ruminant waste), or most troubling, a decline in the ability of the atmosphere to break down methane, producing a longer lifetime for it in the atmosphere. This could occur because of increased pollution in the atmosphere and is considered to be “profoundly worrying.”22
This increase in methane emissions has the potential to thwart all the prospects for the 2015 Paris Accord without even considering CO2.
The scariest part about methane concerns the huge amounts of it that are locked up in hydrates in the higher latitudes. These ice-like crystals reside beneath ocean waters and could potentially degrade, releasing the methane trapped inside them.
With the Arctic warming as quickly as it is, there is concern about the release of methane in this area. Although we are, indeed, seeing methane being produced here, a paper published in January 2018 finds that it is not from the seafloor, but rather “from recently produced organic matter or from the atmosphere.”23 While this is relatively good news, it does seem to add evidence to the idea mentioned above in the Arctic section that processes such as the abrupt thaw of thermokarst lakes may be an important new sources of methane in the northern latitudes.
In a similar fashion, methane is trapped throughout the permafrost in northern latitudes. Nearly a quarter of the Northern Hemisphere sits atop permafrost. A year after the aforementioned paper from January 2018, a new global study in Nature Communications, confirmed that the permafrost is thawing across the globe. In parts of Siberia, the rise was almost one degree Celsius.24
Clouds are an incredibly difficult part of the atmospheric equation to understand. Cloud formation in the Arctic has been thought to play a cooling role there, but new insights now suggest that the “blanket” effect of the cloud cover could predominate, leading to a warming of the Arctic.25
There is so much we don’t know about this. The obvious danger is that as the climate warms, positive feedback loops could be triggered, leading to a cycle of more methane and higher temperatures. The warmer and wetter weather across the tropics will simply exacerbate this process, as will the warming at the poles.
The Lithosphere is the rigid, outermost shell of our planet. Residing on the Lithosphere we have access to air, water, soil and the ecosystems of plants and other animals upon which we depend. It plays a fundamental role in the earth’s carbon cycle with most of the planet’s carbon stored in rocks and sediments. It moves throughout the components of the biosphere. Plants remove carbon from the atmosphere by photosynthesis using energy from the sun. The Amazon jungle is sometimes referred to as the earth’s lungs because of this. When the plants are eaten the carbon moves to the animal food chain. Eventually, that carbon is moved to the ground (lithosphere) with some of it becoming fossil fuel after millions of years. The burning of fossil fuels releases the carbon into the atmosphere as carbon dioxide. Most of the carbon released in this way is absorbed by the oceans.
Over very long time scales, the weathering of rocks adds carbon to surface water which eventually ends up in the oceans. Mountain building provides new rock and opportunities for weathering. The result is that the process of mountain uplift lowers the CO2 in the atmosphere. When the Indian tectonic plate collided with the Asian plate and created the Himalayas, some 50 million years ago, the weathering from the monsoon rains produced a cooling so dramatic that global temperatures dropped enough to set the stage for the Ice Ages.26
The carbon dioxide being added to the atmosphere by the burning of these ancient fossil fuels will eventually be removed by the carbon cycle, but we are talking about millions of years for this to happen. What we are doing to the planet will be the legacy for the generations of humans to come as well as all the creatures with which we share the earth essentially forever.
Update June 20, 2019 – Arctic Permafrost Thawing 70 Years Sooner Than Expected
In a paper published June 10, 2019, a research team from the University of Alaska Fairbanks has found a shocking increase in the rate of change of melting during their long term study of the permafrost in the Canadian High Arctic.27
This stunning news follows from the team’s traveling to remote sites where “they were confronted with a landscape that was unrecognizable from the pristine Arctic terrain they had encountered during initial visits a decade or so earlier…The vista had dissolved into an undulating sea of hummocks – waist-high depressions and ponds known as thermokarst.”28
As has already been discussed here, this rapid thawing could release vast quantities of GHG and fuel a feedback loop producing even more melting.
Update August 15, 2019 – The Loss of the Arctic’s Reflective Sea Ice Will Advance Global Warming by 25 Years
The Arctic continues to change at nothing less than alarming speed. The implications for the planet are dramatic: a new paper from the Scripps Institution of Oceanography 29 concludes that the loss of the remaining Arctic sea ice and it’s ability to reflect incoming solar energy back to space “would be equivalent to adding one trillion tons of CO2 to the atmosphere.” To put this into context, 2.4 trillion tons of CO2 have been emitted since the beginning of the Industrial Age. This huge addition of CO2 would bring the onset of global warming of 2° Celcius 25 years sooner than expected.
The summer of 2019 has been characterized by unusual wildfires across Siberia, Scandinavia, Alaska, and Greenland. One estimate is that the fires released 50 million tons of carbon dioxide in the month of June alone, equivalent to the annual emissions of Sweden.30