New Research Shows Global Warming Could Turn Tropics Into a Sweltering Dead Zone

New research out of Purdue University finds that a global warming event called the PETM made parts of the tropics too hot for living organisms to survive. And though the PETM happened many millions of years ago, these new scientific revelations are pertinent to the present day. The reason is that human activity in the form of fossil fuel burning is now rapidly causing the globe to heat up. And such warming, if it continues, could well turn large sections of the tropics into a dead zone.

PETM — Warm-up Sparks Global Upheaval, Extinction

The PETM was a big global warm up that happened 56 million years ago as the Paleocene epoch passed into the Eocene. It is numbered as one of many hothouse extinctions occurring in the geological record. And it is generally thought to have been one of the milder such events — especially when compared to the biosphere wrecking ball that was the Permian.

(NASA tool shows that business as usual greenhouse gas emissions would force average maximum July temperatures over large sections of the world to warm to 40-45 C [104-113 F] by the 2090s. For many regions, such a high degree of heat is incompatible with crops and human habitability. In the deep past, hothouse events were found, in recent research, to render large sections of the tropics uninhabitable to most forms of life. Image source: NASA.)

During the PETM, global temperatures jumped by 5 degrees Celsius above an already warm base-line over the course of about 6,000 years. And research indicates that the resulting heat stress set off massive wildfires, forced land animal species to move pole-ward, and killed off a big chunk of the ocean’s bottom dwelling foraminifera.

Parts of the Tropical Biosphere Seem to Have Died

However, past scientific consensus held that the tropics still managed to support life during the PETM due to a kind of thermostat-like heat regulation preventing the equatorial region from becoming too warm. Temperatures were thought to have remained within a range that would have continued to support life in this lower latitude zone. So it was only thought that the tropics experienced die-offs during ancient and more intense warming events like the Permain of 250 million years ago.

The new research by Purdue scientists calls that theory into question. Their findings show that temperatures crossed a key threshold — becoming too hot to support life throughout sections of the tropics and rendering large areas uninhabitable.

Matthew Huber, professor in the Earth, Atmospheric, and Planetary Sciences Department at Purdue University and study co-author notes:

“The records produced in this study indicate that when the tropics warmed that last little bit, a threshold was passed and parts of the tropical biosphere seems to have died. This is the first time that we’ve found really good information, in a very detailed way, where we saw major changes in the tropics directly associated with warming past a key threshold in the past 60 million years.”

Half of Human Population Lives and Farms in the Tropics

During the present day, about half the human population, a good chunk of the world’s life forms, and a considerable amount of global farming occupies the tropics. However, according to recent research by the Max Planck Institute, parts of the tropical zone could be rendered basically uninhabitable to human beings by mid Century as the Earth heats up due to fossil fuel burning. And already, the critical region of Equatorial Africa and the adjacent Middle East are experiencing record droughts, water stress, and instances of hunger, famine and related food insecurity as global temperatures rise to 1 C or more above 1880s averages.

(Climate zone habitability is a function of what forms of life can exist in a given region at a given range of temperatures. Warming in the tropics is expected to impact human habitability by mid Century. Warming, however, is also expected to impact crop yields well into the middle latitudes. U.S. food production is therefore likely to be negatively impacted by rising global temperatures. Video source: Peter Carter.)

The serious concern is that as the world warms up — a humanitarian crisis of unprecedented scope could emerge as whole countries become unable to support their populations. As entire regions become too hot to live in. And as major swaths of global farmland become non-productive.

The present narrative hints that human civilization can somehow adapt by shifting farm zones northward. However, it’s worth noting that boreal regions do not support the same highly productive soils as the tropical and temperate zones that are now under threat due to rising temperatures. In addition, the nations of the world have thus far shown considerable reluctance to accepting refugee populations from destabilized zones. And as the world heats up, desperation will only increase as waves of refugees seek to remove themselves from what could well become a kind of global warming produced dead zone.

The Perdue research underscores a very real risk that we are now facing. It shows that the tropics did not self regulate temperature in a range conducive for life during the PETM. And these findings reinforce present temperature and soil moisture research trends placing human habitability and crop production under threat due to fossil fuel based warming this Century.

(UDATED)

Links:

Global Warming Can Breach Limits for Life

Climate Impacts of the PETM

NASA

Peter Carter

Hat tip to Suzzanne

Hat tip to Colorado Bob

Hat tip to Andy in San Diego

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Ten Times Faster Than a Hothouse Extinction — Human Carbon Emission is Worst in at Least 66 Million Years

“If you look over the entire … last 66 million years, the only event that we know of … that has a massive carbon release and happens over a relatively short period of time is the PETM. We actually have to go back to relatively old periods. Because in the more recent past, we don’t see anything [even remotely] comparable to what humans are currently doing.” Richard Zeebe of the University of Hawaii in a recent paper published in Nature.

*****

carbon-emissions

(Annual human carbon emissions are about 150 times that of all the volcanoes on the Earth, 10 times faster than a hothouse extinction that occurred 55.8 million years ago. Image source: La Rosa Rossa.)

Let’s be very clear. The human fossil fuel emission is outrageous and unprecedented on geological timescales. An insult the Earth has likely never seen before. For the pace at which we are emitting carbon into the atmosphere is just flat out insane. We’ve known this for some time because the best of science can’t find any time in all of Earth’s geological history that produces a rate of atmospheric carbon accumulation equal to the one that’s happening now.

However, a new study recently published in Nature now sheds more light on this rather difficult and scary topic. But in order to find an event that is even remotely comparable to the current human greenhouse gas emission, scientists had to look far back into deep time. All the way back through a period when the last of the Dinosaurs were dying off about 55-66 million years ago.

During this time we find evidence of the most recent Hothouse Mass Extinction Event in the geological record. We call this event the Paleocene-Eocene Thermal Maximum or PETM because it’s an extreme period of rapid warming that occurred at the boundary between these two periods of Earth History about 55.8 million years ago.

The PETM Hothouse Extinction

The PETM was pretty amazingly bad. It set off a mass extinction in the oceans which wiped out half of all shellfish through the varied impacts of anoxia, acidification and coral bleaching. Its heat forcing was enough to completely reverse ocean circulation and set up a stratified ocean state. Peatlands and forests went up in mass conflagrations. Terrible insect plagues swept the globe. The related extreme surface temperatures forced a mass poleward migration and widespread genetic alteration of mammals which were eventually reduced to dwarfism.

Human vs PETM

(Earlier studies estimated PETM emissions rates in the range of 1.7 billion tons of carbon per year. A new Nature study finds PETM emissions to be even lower at 1.1 billion tons of carbon per year. This compares to a current human emission of 10 billion tons of carbon per year. A rate of emission that could jump to as high as 25 billion tons of carbon per year by mid Century unless fossil fuel use is curtailed. It’s worth noting that the ‘slow but steady’ PETM emissions above represent one of the most rapid periods of warming in Earth’s geological history. Image source: Climate Crocks.)

It was a rough and wrenching time of change and difficulty for pretty much all of life on Earth. But what the new study finds and confirms is that the rate of atmospheric carbon accumulation during that extinction period, though enough to cause seriously dramatic climate shifts, was much, much slower than what we see now.

A Human Hothouse Extinction Would be Far Worse

On average, over the PETM extinction event, rates of atmospheric carbon accumulation were found to be in the range of about 1.1 billion tons per year. By comparison, human carbon emissions during 2014 were about ten times this level at around 10 billion tons of hothouse gas hitting the atmosphere. As such, the new study finds that the velocity of the human carbon emission exceeds that of the Paleocene-Eocene hothouse extinction event by an order of magnitude (x10).

Study authors found that the large carbon emission occurred over the course of about 4,000 years. This spike in atmospheric carbon coincided with an approximate 5 degree Celsius spike in global temperatures in the 4,000 to 12,000 year time period. This implies a rate of warming of at most around 0.12 degrees Celsius every 100 years (or as little as 0.04 degrees Celsius per Century). Other estimates put the rate of PETM warming at around 0.025 C per Century. Expected human warming between 1 and 5 degrees Celsius this Century is therefore about 10 to more than 200 times faster than during the PETM extinction event given the best available current scientific evidence.

Such high rates of atmospheric carbon accumulation and related global heating risk generating an event that is outside of any geological context that scientists might use to predict the human warming event’s severity.

“It means we don’t have a really good analog in the past for the massive amount of carbon we’re releasing,” Zeebe said to National Geographic. “Even if we look at the PETM and say the transition to a warmer climate may have been relatively smooth, there’s no guarantee for the future.”

In other words, if you’re adding carbon to the atmosphere at a rate ten times faster than during one of the most remarkable warming events in Earth’s History, then the pace of wrenching geophysical changes and the extinction pressure on organisms is going to be far, far greater. Something that is certainly worse than the PETM and that may even exceed the terrible losses seen during the Permian Mass Extinction if we don’t get a handle on our fossil fuel emissions soon.

Links:

Anthropogenic Carbon Release Unprecedented in Last 66 Million Years

A Deadly Climb From Glaciation to Hothouse — Why the Permian Extinction is Pertinent to Human Warming

Earth Hasn’t Heated Up This Fast Since the Dinosaurs’ End

PETM — Global Warming, Naturally

Hat tip to DT Lange

Hat tip to Colorado Bob

 

 

Dangerously Beyond 350: CO2 to Remain Above 400 PPM For Most of 2015

For 2015, CO2 levels will remain above the dangerous 400 parts per million level for almost 2/3 of the year. A perilous new record for a human-warmed world.

The last time global CO2 levels averaged above 400 parts per million was more than 3 million years ago during the Pliocene. A period that was just beginning to see the dawn of humankind (Australopithecus emerged about 2.5 million years ago). It was a world of 25-75 foot higher seas. A world where much of Greenland and West Antarctica was ice free. A world that took hundreds of thousands of years to settle into its climate patterns.

2014 Begins at 400 ppm +

(A bad start of 2015 — CO2 levels on January 1st exceeded 400 PPM. Most of the year will see levels in excess of this dangerously high atmospheric value. Image source: The Keeling Curve.)

But the current human tool-using species that is now warming the Earth so drastically would have to wait for about 2.8 million more years and for far cooler climes to develop. And that species would set conditions for a rapid shift to climate states not seen for 3 million years in just decades through a hellish pace of fossil fuel burning.  For in just one century we’ve propelled ourselves back to that deep time. Back to a world climate state that is entirely alien to what we, and so many other animals, are accustomed to.

For this year, human fossil fuel emissions will push 2015 to reach or exceed those 400 ppm levels for around 7-8 months running. By 2016, it’s possible that 300 part per million levels — the ones that dominated our environment for most of the 20th Century — will be little more than a melancholy memory as humans face off against a series of increasingly dangerous  geophysical changes.

All set off by the inexorable burning of fossil fuels. A malpractice that simply must stop.

An All Too Steep Ramp-up Toward The Hothouse

Current human fossil fuel burning coupled with a few, still somewhat contained, environmental carbon feedbacks are enough to push an annual atmospheric CO2 increase of 2.2 parts per million each year. It’s a pace of initial greenhouse gas heat forcing never before seen in all of Earth’s geological past — even during the greatest global hothouse extinction events. The fruits of dumping 36 billion tons of CO2 into the atmosphere each and every year.

petm_vs_modern_emissions

(Rate of carbon emission at more than 30 billion tons of CO2 each year vs the PETM [Note that WeatherUnderground has erroneously labeled CO2 as Carbon in the graph]– which was the most recent hothouse extinction 55 million years ago. It’s enough to push an atmospheric temperature rise on the scale of a mass extinction over the course of decades rather than millenia. It’s also worth noting that with CO2 emissions at 36 gigatons in 2013 [vs the above graph results from 2010] and CO2e emissions just shy of 50 gigatons this trajectory is even steeper than the graph depicts. Image source: WeatherUnderground.)

As a result, if current rates of burning continue or increase, we will see 450 parts per million levels well exceeded within about two decades. And that threshold will undeniably lock in at least 2 C worth of warming together with a growing carbon feedback from the Earth System itself.

484 PPM CO2e For 2015

But this drastic pace of atmospheric greenhouse gas additions doesn’t tell the whole story. For if you add up all the other gasses humans have dumped into the atmosphere, all the methane and HCFs, all the industrial chemicals, you end up with a CO2 equivalent number (CO2e) far greater than the present CO2 measure. And that CO2e measure is set to hit 484 parts per million this year (With a nearly 50 gigaton annual increase in CO2e gasses each year). A level that, if it correlates with past climates, will push warming by 1.9 C this century and 3.8 C after the entire Earth System responds. A level not seen in at least 13 million years.

A rather terrible situation to say the least. For at these levels, even the great ice sheets of Antarctica proper were much reduced and sea levels were 85-120 feet higher than they are today. And continuing to burn begs the very worst hothouse extinction consequences that come from wrecking the world’s oceans.

Very Hard Work to Get Back to 350 PPM

Near the end of the first decade of the 21st Century Dr. James Hansen, former head of GISS at NASA advised the world community that the likely safe level of global CO2 was below 350 parts per million. This assertion flew in the face of some in the international community who were pushing for an established ‘safe’ level of 450 parts per million and below. A level, of course, which would allow for the burning of quite a bit more of the world’s fossil fuel reserves.

But Hansen wouldn’t compromise. He felt it would be a betrayal to future generations. To his grandchildren. To all our grandchildren. So he set the safe limit at 350 parts per million with the caveat that we may need to reduce it further.

In 2008, during the year Hansen set the 350 parts per million level, CO2 levels peaked at around 386 parts per million. For 2015, just 7 years later, levels will peak at around 404 parts per million. A rampant increase directly in the wrong direction.

In order for rates of CO2 increase to begin to taper off, the world simply must stop burning so much in the way of fossil fuels. And even a full cessation of fossil fuel use would still result in some emissions unless both farming and construction were altered to reduce carbon emissions. Beyond this, atmospheric carbon capture through various methods to include fixing carbon capture and storage facilities to biomass generation and other land use and chemical based techniques are the most likely to be effective.

Such a transition and change is as difficult as it is necessary. For the world as we know it simply cannot continue along its current path. Hansen was right and we should have listened 7 years ago. We should have listened in 1988 at his first major climate hearing. But we didn’t. And so valuable time was wasted.

Let’s not make the same mistake in 2015.

Links:

The Keeling Curve

2015 Begins With CO2 Above the 400 PPM Mark

WeatherUnderground

2013 CO2 Emissions Will Set Record High

A Faustian Bargain on the Short Road to Hell: Living in a World at 480 PPM CO2e

Scientific Hat Tip to Dr. James Hansen and Dr. Ralph Keeling

El Nino Update: Monster Kelvin Wave Continues to Emerge and Intensify

Monster Kelvin Wave

(Kevin Wave continues to strengthen and propagate across the Pacific Ocean. Image source: NOAA’s Climate Prediction Center.)

Record global temperatures, extraordinarily severe storms for the US West Coast and telegraphing on through the Central and Eastern US, a disruption of the Asian Monsoon and various regional growing seasons, record heat and drought in Northern Australia, severe drought and fires in the Amazon, the same throughout Eurasia and into the Siberian Arctic, another potential blow to Arctic sea ice. These and further extreme impacts are what could unfold if the extraordinarily powerful Kelvin Wave now racing toward the Pacific Ocean surface continues to disgorge its heat.

The most recent update from NOAA shows that the monster Kelvin Wave we reported on last week has continued to grow and intensify even as it shows no sign of slowing its rather ominous emergence from waters off the west coast of South America.

The pool of 4-6+ degree Celsius above average temperatures continues to widen and lengthen, now covering 85 degrees of longitude from 170 East to 105 West. Perhaps more disturbing is the fact that the zone of extreme 6+ C temperature anomalies has both widened and extended, covering about 50 degrees of longitude and swelling to a relative depth of about 30-40 meters. This is an extraordinarily intense temperature extreme that well exceeds those observed during the ramp-up to the record 1997-98 El Nino event.

Meanwhile, a smaller, but still disturbing, zone of 3-6+ C above average temperatures has now developed just 100 feet below the surface along a line near 100 degrees West Longitude. It is a very strong heat pulse, the head of the Kelvin Wave that by late March had pushed its nose up in the Eastern Equatorial Pacific.

Kelvin Wave Side Graph

(Deep, hot Pacific Ocean water continues to shift east. Image source: NOAA’s Climate Prediction Center.)

In the above NOAA graph we can see the hot, deep pool in the Western Pacific gradually flowing eastward, spreading out and shallowing as it begins to dump its heat content back into the atmosphere. A return of stored ocean heat that will, likely, spike global atmospheric temperature values all while sparking off a series of very extreme weather events.

Warm Storms Continuing to Pull Heat Eastward and Upward

The west-to-east progression and upwelling of Pacific Ocean heat is currently facilitated by low pressure systems lining up along the equator. The lows are fed by heat and evaporation bleeding off the Pacific Ocean surface. This heat enhances the formation of thunderstorms that join into larger, heat-driven cyclonic systems. The countervailing circulations of these systems act to slow the trade winds while allowing the hot pool to spread further and further east.

It is a pattern that tends to emerge at the beginning of most El Nino events. A self-reinforcing cycle that draws energy from ocean surface heat even as its intensity is enhanced more and more by heat transfer from the depths.

GFS Model North Pacific

(GFS model guidance through April 13 shows a persistent cyclone off New Guinea interrupting the trade winds — lower left — even as a long trough is predicted to form over the Eastern Pacific just north of the Equator — lower right. This pattern would tend to enhance the formation of El Nino conditions throughout the forecast period. Image source: NOAA)

It is the kind of cycle in which the excess Ocean heat, amplified by human-caused global warming, and long stored in the Pacific, as Dr. Kevin Trenberth well observed, may now be coming back to haunt us.

Conditions of a Human-Altered ENSO Cycle Compared to the Most Recent Warming at the End of the Last Ice Age

The La Nina to El Nino cycle (ENSO) is part of a larger ocean and air energy transfer pattern in which heat is periodically stored in the vast equatorial waters of the Pacific before being returned again to the atmosphere. In a normal climate state, this dance of heat energy between the airs and the waters would result in simple periodic variation appearing at the peak of either La Nina (atmospheric cool extreme) or El Nino (atmospheric warm extreme). But because human warming has now added a very strong and rapid heat forcing to this natural cycle of variability, La Nina periods have displayed slower rates of atmospheric warming (where they should have showed cooling) and El Nino periods have often resulted in temperatures spiking to new global records.

Natural variation, in this case, rests on a curve that we are forcing to bend inexorably upward.

Of the .8 degrees Celsius worth of annual global warming experienced since the 1880s, about .15 C, or nearly 20 percent of this warming, occurred during the powerful 1997-98 El Nino event in which vast amounts of stored ocean heat returned to the atmosphere. Since 1998, the Pacific Ocean has undergone a long period of La Nina events in which a large store of atmospheric heat was transferred to the global ocean system. But despite this enormous heat transfer, global temperatures continued to climb with new records achieved in 2005 and 2010 during relatively weak to moderate El Nino events.

For the currently emerging El Nino, all indications point toward it being as strong or stronger than the extraordinarily powerful 1997-98 El Nino, perhaps readying to raise global temperatures by another .15 C or more.

April 1 sea surface temperature anomaly

(April 1 Sea Surface Temperature Anomaly Map shows a band of 1-3 C above average temperatures covering the Equatorial Pacific. It’s a marked difference from the slightly cooler than average conditions that have dominated for much of the past year. Given the current Pacific Ocean weather context and the very strong Kelvin Wave lurking just beneath the surface, it appears to be the start of a powerful El Nino phase. Image source: NOAA/ESRL)

For context, the difference between the 1880s and the last ice age was about 4 degrees Celsius. A temperature change that took about 10,000 years to complete. The total current warming of .8 C is equal to about 20% of the difference between the 19th Century and an ice age, but on the side of hot. This warming occurred at extraordinary velocity, over the course of little more than a century. An extreme pace of warming now between 30 and 40 times faster than that at the end of the last ice age. A pace of global heat accumulation that has not been seen in at least 65 million years.

Under business as usual fossil fuel emissions, even that very rapid pace of warming could more than triple over the coming decades, producing a warming equivalent to what occurred during the end of the last ice age over the course of 10,000 years in less than 200. A disastrous pace that will wreck untold harm on the world’s weather systems, climates, ocean systems, geographies and ecologies should it emerge. A pace of warming that likely has no corollary even in the Permian Hot House Extinction Event of 250 million years ago.

In the current cycle of human warming, a strong El Nino can push that measure by as much as 5% or more in just a single year. So we may well see global average temperatures of 1 C higher than 1880s values by the end of 2014-2015 should the current and very powerful El Nino continue to emerge.

Links:

NOAA’s Climate Prediction Center

Monster El Nino Emerging in the Pacific

NOAA/GFS

NOAA/ESRL

Global Heating Accelerates, Deep Ocean Warming the Fastest, What Does it Mean for Methane Hydrates?

A Deadly Climb From Glaciation to Hothouse — Why the Permian Extinction is Pertinent to Human Warming

NOAA: El Nino is Coming, Extreme Weather, New Global High Temperature Records Likely to Follow

A Deadly Climb From Glaciation to Hothouse — Why the Permian-Triassic Extinction is Pertinent to Human Warming

In looking at the potential impacts of human caused climate change over the coming decades and centuries, scientists have often pointed toward more recent times such as the Eemian (the most recent warm interglacial in which global temperatures are similar to what they are now and where they are expected to be over the next 20 years), the Pliocene (2-3 million years ago and the most recent time in which CO2 levels were about equal to those of today), and the PETM (about 55 million years ago and the most recent period during which CO2 levels were above 600 ppm and in which there was very rapid warming, possibly due to methane hydrate release).

The PETM has been a period of very intense study for leading climatologists such as James Hansen who has warned of the potential for a mini-runaway warming event of this kind should humans continue along a business as usual path of fossil fuel burning through the 21rst Century. In particular interest in the PETM corollary scenario is both the amazing velocity of the initial human warming, with CO2 and greenhouse gas releases occurring at rates that are five (CO2) to 27 (methane) times faster than the PETM (Hat tip to Timothy Chase, Source: Skeptical Science). So rapid and powerful a rate of forcing puts at risk of greater release a number of very large global carbon deposits including the massive CO2 and carbon stocks stored in the world’s melting permafrost as well as the even larger stores of carbon locked in methane hydrates scattered across the world’s oceans. Hansen and other scientists have noted a potential for a 4-7 degree Celsius or greater warming by 2100 (at between 700 and 1000 ppm CO2) through a combination of human greenhouse gas emissions and Earth systems carbon emissions. Overall warming by 2300 from Earth Systems feedbacks, even if human emissions were to stop by 2100, is likely to be twice this level.

That such a massive warming would be catastrophic is a given. There is no evidence in the geological record for such a stunning pace of warming over so short a period. And the potential climate change impacts from such high levels of heating, alone, would be extraordinarily difficult for human civilizations and the innocent inhabitants of our living world to manage.

Late Permian Just Prior to De-glaciation

Late Permian Just Prior to De-glaciation at approx 260 million years ago.

(Image source: Ron Blakey, NAU Geology)

But this scientific scenario is based, in part, on knowledge gleaned by studying past geological periods such as the Eemian, Pliocene, and the PETM hyperthermal (other information is derived from the still-developing climate models of terrestrial, ocean, and Earth systems). And, in looking at each of these paleoclimate periods, we find that a single key factor is missing: they all occurred during periods in which Earth was either ice-free, or in which Earth was settling into its current period of glaciation. In the case of human-caused warming, the exact opposite process is ongoing. As during the great Permian Extinction event of around 250 million years ago, the Earth is rising out of a period of glaciation and into a potential human-caused hot-house.

No More Ice Ages and a Start Down the Path Toward De-glaciation

In the current period of human-caused warming we encounter the novel and relatively uncharted territory of an Earth System that is being forced to arise out of a 40 million year long period of glaciation. This period has been characterized, first, by the freezing of the vast land mass of Antarctica, then by the freezing of Greenland and, later, by long ice ages in which glaciers expanded from the poles to cover large areas of land and water. This latter ice age-interglacial period began about 800,000 years ago and has dominated until today.

Glaciation since PETM

(Image source: James Hansen)

With atmospheric CO2 levels now at 400 ppm and with humans continuing to emit high volumes of CO2 for at least the next two decades, we can officially declare the period of ice ages and interglacials at an end (or at least put on extended hold). For retaining even a very small portion of our current greenhouse gas emitting infrastructure or agriculture would be enough to stave off another ice age. Hansen notes:

Forces instigating ice ages, as we shall see, are so small and slow that a single chlorofluorocarbon factory would be more than sufficient to overcome any natural tendency toward an ice age. Ice sheets will not descend over North America and Europe as long as we are around to stop them.

Ice ages are now stopped in their tracks and current human levels of CO2 at 400 ppm are now sufficient to begin melting Greenland and West Antarctica. We can see this melt in yearly losses exceeding 500 gigatons of melt water and ice from Greenland and from Antarctic melt losses in the range of 300 gigatons per year or more. And with the increasing human heat forcing, these melt rates are on a very rapid incline. Greenland is showing a doubling in its melt rate every 5 years.

Yet even this, rapidly expanding, melt pace may seem slow if humans continue along their current path of greenhouse gas emissions growth. Last year, over 32 gigatons of CO2 were emitted into the atmosphere and the net human greenhouse gas emission was equivalent to more than 45 gigatons of CO2. At the current rate of emissions and emissions growth, we are now on track to hit between 500 and 600 parts per million of CO2 by the middle of this century. And this range of CO2 is enough or nearly enough to melt all the world’s ice, setting us on a path toward a place not seen in at least 40 million years. A path toward long-term temperatures in the range of 6 degrees Celsius hotter than the 1880s. If emissions continue until the end of this Century, the path is almost certainly toward that of a hyperthermal and one with unique consequences given the speed at which we approach it and the fact that we will send massive volumes of fresh meltwater into the oceans as we approach it.

The PETM and the Great Dying

And this is where we encounter a bit of a problem. Because the world is rapidly rising up out of a 40 million year long glacial period, it is bound to encounter changes not visible 40 million years ago as the Earth was steadily cooling down toward glaciation or even during the PETM as the Earth emerged from a lesser cool period and entered a hothouse state. In the case of the Permian and the current day, Instigating the loss of glaciers presents its own, rather unique, set of problems and difficulties.

In looking at the geological record, we find that the last major cold period with temperatures close to those of the recent ice ages (aside from a somewhat cool period during the late Jurassic and early Cretaceous) occurred during the late Carboniferous and the early to mid Permian period.

Past Hot and Cold Periods

Hot and cold periods during the last 500 million years (best proxy data used).

(Image source: Commons)

During the late Permian and early Triassic, however, very rapid and intense warming roughly equivalent to that of the Eocene of 55 million years ago occurred. Both events resulted in extinctions in the oceans and on land. Both events showed major temperature spikes toward the end that are theorized to be linked with large methane pulses and amplifying Earth Systems feedbacks. And both are typical to a mini runaway hyperthermal of the kind James Hansen warns is possible under a regime of human warming.

The primary differences between these two events is that, first, the Permian Triassic extinction event occurred after a long period of glaciation and, second, that the Permian extinction was the greatest mass extinction ever recorded in the geological past. What resulted killed off a devastating 96% of the species in the oceans and 80% of all species on land. It is for this reason that the Permian-Triassic boundary layer extinction is known as the great dying.

By contrast, the PETM resulted in a similar, but far less, extreme event. About 35-50% of the benthic forminifera of the deep ocean went extinct. Many other ocean species, especially those of the deep ocean, exhibited stress and losses. Life on land, especially among mammals, was pushed toward dwarfism to deal with the extreme high temperatures. But, overall, stresses to land and ocean animals was far, far less than that of the Permian extinction.

Putting a Lid on the Ocean — Glacial Melt’s Role in Enhancing Anoxia

At issue here is the likely anoxic ocean states resulting from major warming events. As the oceans are heated, they are able to hold less oxygen in solution. This steady depletion results in growing regions of anoxia and related algae blooms that can be very dangerous to marine and, in extreme cases, terrestrial organisms. Warmer, anoxic oceans are more likely to host blooms of deadly green and purple algae.

Troubling Green Algae Bloom North of Scandinavia.

Troubling Green Algae Bloom North of Scandinavia.

(Image source: NASA/Lance-Modis)

These primordial creatures once ruled the seas during the days of ancient Earth, before higher levels of oxygen were present. Now, a mixed, oxygen rich ocean keeps their development in check. But the warmer ocean during the time of the PETM is thought to have brought anoxic states back to the world’s deep oceans.

In short, ocean circulation is thought to have reversed. Heating at the tropics resulted in seas becoming saltier as waters there evaporated. These saltier waters grew dense and sank toward the ocean bottom drawing fresher, cooler water in from the poles. This type of ocean circulation is thought to have dominated for about 40,000 years during the PETM and contributed greatly to anoxic ocean states by concentrating warmer, anoxic water at the bottom of the world’s oceans.

During the Permian, anoxic ocean states were thought to be far, far more intense. Paleontological research conducted by Peter Ward found a massive series of three extinction events ranging over the course of about 165,000 years in which death began at the bottom of the Permian ocean and climbed toward the atmosphere.

It is thought by some scientists that rapid warming during the Permian enhanced both glacial melt even as it amped up the hydrological cycle to increase fresh water runoff from the continental land mass. The result was a much greater freshening of the ocean surface. Enhanced evaporation at the equator is thought to have driven a similar ocean circulation to that of the PETM in which hotter, saltier water sank to the ocean bottom. Glacial melt, in this case, greatly enhanced an ocean circulation change that was already leading to anoxic ocean states. The result was that ocean layers became even more stratified and less mobile further amplifying anoxia. In the case of the Permian, ocean anoxia eventually enveloped a majority of the worlds oceans, permeating all the way to the surface and eventually invading the atmosphere.

The Emergence of the Canfield Ocean

A stratified, anoxic ocean developed which started increasing mortality among deep water life forms first. As anoxia rose through the deep and mid levels of the ocean, death advanced up the water column as green and purple algae found sunlit regions and proliferated, adding hydrogen sulfide gas as a killing mechanism to ocean acidification and low ocean oxygen levels. Eventually, the hydrogen sulfide reached the surface waters at which point it began bubbling into the atmosphere. The anoxic ocean had fully transitioned to a primordial Canfield Ocean.

Hydrogen sulfide gas is directly toxic to both plants and animals alike and this great out-gassing likely resulted in the massive loss of land species. Ironically, high temperatures (on the order of 9-12 degrees C hotter than now) enhance the lethality of hydrogen sulfide gas. When the gas reaches the stratosphere, it depletes the ozone layer, causing even greater harm to land species. Fossil remains show evidence of genetic damage indicative of a depleted ozone layer and related Canfield Ocean state.

Human Warming is Much, Much Faster

It took about 20,000 years for the Earth to warm 6 degrees Celsius during the PETM. During the Permian, the final extinction and related warming events lasted about 165,000 years. In the case of the PETM, it is thought that volcanism in India stoked global warming until a rapid methane release over a 20,000 year spike period occurred. During the Permian, volcanism is thought to have burned through coal patches over a large region of Siberia, possibly eventually setting off similar very large methane pulses to those suspected to have occurred during the PETM.

In both cases, temperatures rose to between 9 and 12 degrees Celsius hotter than today. But, in the case of human warming, we have the potential to warm the Earth by as much as 7 degrees Celsius by the end of this century and, possibly, to Permian/PETM levels over the next 300 years. Such a rapid pace of warming holds no corollary in either the Permian, the PETM or during any other major warming event visible in the geological record of Earth’s past. So while we may look to the Permian for potential enhanced ocean circulation and anoxia impacts due to glacial melt and increasingly intense ocean stratification, we have no rational means by which to determine how far behind increasing temperatures and glacial melt such events may arise. In the case of the Permian, it took about 165,000 years for a Canfield Ocean to arise. But anoxic ocean states emerged and intensified as warming ramped up. So it is likely that ocean anoxia and stratification will become an increasing problem as the Earth rapidly warms due to human forcing. We can also expect glacial melt to amplify the problems caused by anoxia by increasing stratification and by pushing warm, oxygen-poor waters toward the ocean bottom where they have little opportunity to recharge oxygen stores. Lastly, in the worst case, we can look for Canfield Oceans as a potential tail-end risk for human warming, especially if global temperatures approach 9 to 12 degrees Celsius above the 1880s average and if very large fresh water pulses from glaciers shut down and reverse current ocean circulation.

Links:

Climate Model Links Past Extinction to Higher Global Temperatures

Changes in Permian Ocean Circulation, Anoxia in the Permian Ocean, and Changes in the Permian Carbon Cycle

Rapid and Synchronous Collapse of Marine Ecosystems During Permian Biotic Crisis

Carbon Isotope Anomaly in Conjunction with Biotic Crisis

Biogeochemical evidence for euxinic oceans and ecological disturbance presaging the end-Permian mass extinction event

Storms of My Grandchildren

Under a Green Sky

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