More Fire and Anthrax for the Arctic: Study Finds 21 to 25 Percent of Northern Permafrost Will Thaw at Just 1.5 C of Warming

In the far north, the land is rippling, trembling, subsiding, and blowing up as greenhouse gasses are released from thawing frozen soil. Meanwhile, old diseases are being released from thawing carcasses and presenting a health hazard to locals. Strange processes that are likely to accelerate soon as global warming approaches 1.5 degrees Celsius and between 21 and 25.5 percent of all the vast region of Northern Permafrost thaws out.

(More methane blowholes like this one in Yamal are likely as permafrost thaw accelerates in the coming years and pockets of methane explosively remove the land above. How extensive permafrost thaw becomes is directly dependent on how much fossil fuel human societies decide to burn. Image source: The Siberian Times.)

Arctic Carbon Feedbacks Accelerating

Carbon feedbacks from the thawing permafrost are a serious concern. And they should be. There’s about 1,400 billion tons of carbon locked away in that massive region of frozen ground. More than twice the amount humans have already emitted into the atmosphere. And though frozen permafrost carbon stays locked away, thawed permafrost carbon tends to become biologically active — releasing into soils, the water and the air.

Already, this thawing has generated a worrying effect. During the 20th Century, it was estimated that about 500,000 tons of methane were released from the Siberian land-based permafrost region. By 2003, as this permafrost zone warmed, the annual rate of release was estimated to be 3.8 million tons per year. And by 2013, with still greater warming, the rate of release had grown to 17 million tons per year. This compares to a global emission of methane from all sources — both human and Earth System-based — of about 500 million tons per year.

(Megaslump craters like the one at Batagaika, formed by subsidence, are also a result of permafrost thaw. Such features are likely to grow and proliferate as the Earth warms and permafrost thaw expands.)

That’s a thirty-fold acceleration in the rate of Siberian permafrost methane emission over a little more than one generation. One that occurred as temperatures rose to about 1 C above 1880s averages and into a range not seen for about 150,000 years. It’s a warming that has produced visible and concerning geophysical changes throughout the Arctic permafrost environment. In Siberia, lands are subsiding even as more and more methane and carbon dioxide are leeching out. And in the Yamal region of Arctic Russia, temperatures warming into the upper 80s (30 C+) during summer appear to have set off a rash of methane eruptions from the soil even as ancient reindeer carcasses release anthrax spores into the environment as they thaw. From a report this week in The Guardian:

Long dormant spores of the highly infectious anthrax bacteria frozen in the carcass of an infected reindeer rejuvenated themselves and infected herds of reindeer and eventually local people. More recently, a huge explosion was heard in June in the Yamal Peninsula. Reindeer herders camped nearby saw flames shooting up with pillars of smoke and found a large crater left in the ground. Melting permafrost was again suspected, thawing out dead vegetation and erupting in a blowout of highly flammable methane gas.

21 to 25.5 Percent of Northern Permafrost Set to Thaw over Next Two Decades

In total, 14 methane blow out craters are now identified throughout the Yamal region. A testament to the growing carbon feedback coming from previously frozen and inactive stores.

(Permafrost losses are likely to be quite considerable over the coming decades — which is likely to produce serious knock-on effects for local and global environments. But continued fossil fuel burning through end Century produces more catastrophic results. Image source: Responses and changes in the permafrost and snow water equivalent in the Northern Hemisphere under a scenario of  1.5 C warming.)

But, unfortunately, these kinds of weird, disturbing, and often dangerous changes to northern environments are just a foreshadowing of more to come. For a recent scientific study has found that just 1.5 degrees Celsius worth of warming will force between 21 and 25.5 percent of the northern permafrost to thaw. A process that is already underway, but that will continue to accelerate with each 0.1 degree Celsius of additional warming. The study found that the faster human atmospheric greenhouse gas emissions build up, the more rapidly permafrost would thaw once the 1.5 C threshold was reached. Under a rapid human reduction of greenhouse gasses (RCP 2.6 scenario), permafrost thaw was reduced to 21 percent in the study. But under worst case human fossil fuel emissions (RCP 8.5 scenario), the accelerated rate of warming resulted in 25.5 percent permafrost thaw.

Perhaps more concerning was the fact that the study found that this 1.5 C temperature threshold was reached by as early as 2023 under the worst case fossil fuel burning scenario even as it was held off only to 2027 if rapid fossil fuel burning reductions were achieved. A broader sampling of studies and natural variability hold out some hope that 1.5 C might be pushed back to the early to mid 2030s in the absolute best case. However, considering the amount of human emissions already released and in the pipeline even under the best cases, it appears that crossing the 1.5 C threshold sometime in the near future is unavoidable at this time (barring some unforeseen massive global response and mobilization).

(Permafrost losses under different human emissions scenarios through 2100 show that continued fossil fuel burning results in between 47 and 87 percent loss of permafrost area by 2100 [RCP 4.5 and 8.5]. Image source: Responses and changes in the permafrost and snow water equivalent in the Northern Hemisphere under a scenario of  1.5 C warming.)

Overall, the study found that surface permafrost losses lagged the crossing of the 1.5 C threshold by only about 10 years. And that the lowest emissions scenarios (RCP 2.6) resulted in a leveling off of permafrost losses to 24 percent by 2100. Meanwhile, the worst case human greenhouse gas emissions scenarios (RCP 8.5) resulted in 87 percent permafrost area reductions by 2100.

Risk of Serious Carbon Feedback Far Worse With Fossil Fuel Burning

With so much carbon locked away in permafrost, heightened rates of thaw present a risk that longer term warming might eventually run away as millions and billions of tons of carbon are ultimately liberated. Under moderate to worst case human fossil fuel burning scenarios, it is estimated that permafrost carbon emissions could approach 1 billion tons per year or more. At about 10 percent or more of the present human emission, such a rate of release to the atmosphere is about equivalent to that achieved during the last hyper-thermal event of 55 million years ago (the PETM). Moreover, a heightened response by large methane stores could result in a more immediate warming effect as methane is 28 to 36 times more potent a heat trapping gas than carbon dioxide over Century time scales.

A risk of serious carbon feedbacks that accelerate rates of warming this Century and over the longer term is not inconsiderable even with a 24 percent loss of Permafrost under the best case scenario identified by this study. However, the likelihood of a much more serious feedback under continued fossil fuel burning is far more apparent.

(UPDATED)

Links:

Responses and changes in the permafrost and snow water equivalent in the Northern Hemisphere under a scenario of  1.5 C warming

All Hell Breaks Loose as Tundra Thaws

Permafrost Thaw to Blow Carbon Budget Faster Than We Would Expect

PETM Hyperthermal

Arctic Methane Emissions

RCP Scenarios

Hat tip to Spike

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2016 on Track for Record Rate of Atmospheric CO2 Increase

During 2016, the annual rate of atmospheric carbon dioxide increase will have hit a record 3.2 to 3.55 parts per million (ppm). By 2017, the amount of carbon dioxide in the Earth’s atmosphere will be roughly equivalent to concentrations last seen during the Middle Miocene climate epoch (404 to 410 ppm average). In other words, atmospheric CO2 is rising at a record rate and we are hitting levels of this heat-trapping gas that have not been seen in about 15 million years.

Record Rates of CO2 Increase

The world is struggling to make the necessary turn toward reducing fossil fuel-based carbon emissions. Global emissions have plateaued at or near new record highs during the past three years. Conflicts over fossil fuel cuts and transitioning to renewable energy embroil numerous countries. Climate change deniers hold significant power in places like the United States, the United Kingdom, Canada, and Australia. And facing off against those who would defend the harmful interests of what could well be called the most destructive industry to ever inhabit the planet, are a broad group of environmentalists, scientists, concerned citizens, and renewable energy advocates.

carbon-dioxide-october-2016-global

(Global carbon dioxide is approaching a level not seen since the Middle Miocene period around 15 million years ago when atmospheric concentrations typically averaged above 405 ppm and global temperatures were 3-4 degrees Celsius hotter than 19th-century averages. Record annual rates of CO2 increase in excess of 3 ppm each year for 2015 and 2016 are swiftly propelling us into a climate state that is more similar to this ancient epoch — a shift that is producing increasingly harmful global consequences. Image source: The Copernicus Observatory.)

As the political turmoil ramps up, it appears that the Earth’s oceans and biosphere are straining to draw in the massive volumes of these gasses that we’ve been pumping out. Annual atmospheric CO2 growth rates for 2015 were a record 3.05 ppm. 2016 appears to be on track to beat that high mark, being likely to see a new annual increase of between 3.2 and 3.55 ppm.

Hot Lands and Oceans Tend to Produce a Carbon Feedback

The previous most rapid annual rate of atmospheric CO2 increase was 2.93 ppm during the strong El Niño year of 1998. Back then, high ocean surface temperatures combined with warming-related wildfires and droughts which spanned the globe to reduce the Earth’s capacity to take in carbon. More carbon was squeezed out of hot soils, burning forests, and warming oceans. Less was drawn down. New record rates of atmospheric CO2 increase were breached.

the-keeling-curve-2-years

(Except for a couple of days, all of 2016 saw atmospheric CO2 levels above 400 ppm. Peak values as measured at the Mauna Loa Observatory in May were 407.7 ppm. By May 2017, atmospheric CO2 levels are likely to hit near 410 ppm — a level not seen in about 15 million years. Image source: The Keeling Curve/Scripps Institution of Oceanography.)

Even during the period of heightened heat stress that occurred in 1998, we did not see a year in which annual rates of CO2 increase exceeded 3 ppm. We have never, until 2015-2016, seen a time when there were two back-to-back years of such rapid rates of increase. Similar but worsening heat stress impacts have likely flagged what at first appeared to be an increased rate of carbon uptake from the biosphere during the late 2000s. Ocean heat content is now dramatically greater than during 1998 and this significant warming is likely having at least a periodic impact on the ocean’s rate of carbon uptake. Wildfires are now far more prolific, generating more atmospheric carbon. Droughts are more widespread and these tend to squeeze carbon from the soil. The Arctic is the warmest it’s been in 115,000 years and, as a result, some new Earth system carbon sources are starting to pop up.

Record High Rates of Fossil Fuel Emissions Hitting a Plateau

In the intervening years since 1998, global carbon emissions from fossil fuels have also jumped dramatically. During 1998, yearly CO2 emissions were in the range of 26 billion tons per year. By 2014-2015, these greenhouse gas releases had soared to around 35.8 billion tons per year. Through this period, average annual rates of CO2 increase continued to climb during the 2000s and 2010s.

global-carbon-project-emissions-2015

(Global carbon emission increases stalled during 2013, 2014, and 2015 according to The Global Carbon Project. But despite this recent pause, atmospheric rates of carbon dioxide increase have continued to ramp up. Due to a number of factors, including atmospheric and ocean inertia as well as temperature and saturation stress to global carbon stores, it is likely that significant reductions in carbon emissions from fossil fuels will be necessary to have a marked impact on annual rates of atmospheric CO2 increase.)

According to NOAA, the 1980s and 1990s saw yearly jumps in CO2 at the rate of about 1.5 ppm each year. By the 2000s, this average rate of increase had leaped to about 2 ppm per year. For the first six years of the 2010s, the average rate will likely be around 2.5 ppm per year.

New Records Provide Urgency For Rapid Emissions Cuts

This rate of increase roughly matches the overall rate of increase in emissions. As yet, there is no major global trend sign in the atmospheric CO2 data showing that carbon uptake from the oceans and the biosphere has been significantly curtailed, at least not to the point that it has shown up in the long term global trend. There are, however, widespread signs of stress to the Earth’s carbon storage system, and two years of 3 ppm-plus increase back-to-back is a warning blip on the climate radar.

In other words, these new record rates of CO2 increase are disturbing. If the annual increases do not fall back into the low 2-ppm per year range in 2017 and 2018, it will be an indication that some of the Earth’s ability to draw down carbon has been significantly hampered. If that is the case, then the urgency to draw down emissions is considerably greater.

Links:

NOAA ESRL

Middle Miocene

The Global Carbon Project

The Copernicus Observatory

The Keeling Curve

Doubling Down on Our Faustian Bargain

Hat tip to SmallblueMike

(Note: This post focuses primarily on CO2 as an indicator. Overall CO2e levels will be covered in a separate exploration.)

Carbon Sinks in Crisis — It Looks Like the World’s Largest Rainforest is Starting to Bleed Greenhouse Gasses

Back in 2005, and again in 2010, the vast Amazon rainforest, which has been aptly described as the world’s lungs, briefly lost its ability to take in atmospheric carbon dioxide. Its drought-stressed trees were not growing and respiring enough to, on balance, draw carbon out of the air. Fires roared through the forest, transforming trees into kindling and releasing the carbon stored in their wood back into the air.

These episodes were the first times that the Amazon was documented to have lost its ability to take in atmospheric carbon on a net basis. The rainforest had become what’s called carbon-neutral. In other words, it released as much carbon as it took in. Scientists saw this as kind of a big deal.

This summer, a similar switch-off appears to be happening again in the Amazon. A severe drought is again stressing trees even as it is fanning wildfires to greater intensity than during 2005 and 2010. Early satellite measures seem to indicate that something even worse may be happening — the rainforest and the lands it inhabits are now being hit so hard by a combination of drought and fire that the forest is starting to bleed carbon back. This gigantic and ancient repository of atmospheric carbon appears to have, at least over the past two months, turned into a carbon source.

Amazon carbon dioxide

(High levels of carbon dioxide, in the range of 410 to 412 parts per million, and methane in the atmosphere over the Amazon rainforest during July and August of 2016 is a preliminary indicator that the great forest may be, for this period, acting as a carbon source. Image source: The Copernicus Observatory.)

Carbon Sinks Can’t Keep Up

Though the story of human-forced climate change starts with fossil-fuel burning, which belches heat-trapping carbon dioxide into the atmosphere, sadly, it doesn’t end there. As that burning causes the Earth to heat up, it puts stress on the places that would, under normal circumstances, draw carbon out of the atmosphere. The carbon-absorbing oceans, boreal forests, and great equatorial rainforests all feel the sting of that heat. This warming causes the oceans to be able to hold less carbon in their near-surface waters and sets off droughts and fires that can reduce a forest’s ability to take in that carbon.

In the context of the global cycle of carbon entering and being removed from the Earth’s atmosphere, oceans and large, healthy forests serve to take in greenhouse gasses. We call these carbon sinks, and throughout the past 10,000 years of our current epoch, the Holocene, they’ve helped to keep these gasses, and by extension, Earth’s temperatures, relatively stable.

carbon sinks

(Without the ability of forests, soils and oceans to take in carbon — to act as carbon sinks — global atmospheric CO2 would have already risen well above 500 parts per million by 2009 due to fossil-fuel burning. These sinks are a helpful mitigating factor to the insult of human carbon emissions, but if they become too stressed, they can become sources of carbon instead. Image source: IPCC/CEF.)

However, for a long time now human fossil-fuel emissions have far exceeded the ability of the world’s carbon sinks to draw in excess carbon and keep greenhouse gas levels stable. Though these sinks have taken in more than half of the great volume of carbon emitted from fossil-fuel burning, the total portion of heat-trapping CO2 has risen from 280 ppm to more than 400 ppm. The oceans acidified as they strained beneath the new carbon overburden. And the forests took in this carbon even as they fought off expanding deforestation. As a result of all the excess carbon now in the atmosphere, the Earth has warmed by more than 1 degree Celsius above 1880s levels. And combined with the already strong stress imposed by clear-cutting and slash and burn agriculture, the added heat is a great strain on an essential global resource.

Global Warming Causes Carbon Sinks to Switch Off, or Worse, Turn into Sources

In this tragic context of heat, drought, ocean acidification and deforestation, it appears that the grace period that the Earth’s carbon sinks have given us to get our act together on global warming is coming to an end. Heating the Earth as significantly as we have is causing these sinks to start to break down — to be able to draw in less carbon, as was the case with the Amazon rainforest in 2005 and 2010. At these points in time, the sink was carbon-neutral. It was no longer providing us with the helpful service of drawing carbon out of the atmosphere and storing it in trees or soil. But, more ominously, in 2016, it appears that the Amazon may also to be starting to contribute carbon back to the atmosphere.

High Surface Methane Amazon August 4

(High surface methane readings over the Amazon in excess of 2,000 parts per billion is a drought and wildfire signature. It is also a signal that the rainforest during this period was emitting more carbon than it was taking in. Image source: The Copernicus Observatory.)

After each of these brief periods of failing to draw down carbon in 2005 and 2010, the Amazon carbon sink switched back on and began to function again for a time. But by 2015 and 2016, record global temperatures had again sparked a terrible drought in the Amazon region. According to NASA officials, the new drought was the worst seen since at least 2002 and was sparking worse fire conditions than during 2005 and 2010 — the last times the Amazon’s carbon sink switched off. In July of 2016, the Guardian reported:

“Severe drought conditions at the start of the dry season have set the stage for extreme fire risk in 2016 across the southern Amazon,” Morton said in a statement. The Brazilian states of Amazonas, Mato Grosso, and Pará are reportedly at the highest risk.

Per NASA’s Amazon fire forecast, the wildfire risk for July to October now exceeds the risk in 2005 and 2010 — the last time the region experienced severe drought and wildfires raged across large swaths of the rainforest. So far, the Amazon has seen more fires through June 2016 than in previous years, which NASA scientists said was another indicator of a potentially rough wildfire season.

Extensive Wildfires Over Brazil and Amazon on August 5 2016

(Extensive wildfires over the southern Amazon and Brazil coincide with apparent atmospheric methane and CO2 spikes. Indicator that the Amazon carbon sink is experiencing another period of failure. Image source: LANCE MODIS.)

At the same time that drought and related wildfires were starting to tear through the Amazon, atmospheric carbon monitors like the The Copernicus Observatory were picking up the signal of a carbon spike above the Amazon with methane levels higher than 2,000 ppb (which is often a drought and wildfire signature) and carbon dioxide levels in the range of 41o to 412 ppm. It was a spike comparable to those over industrial regions of the world like eastern China, the U.S. and Europe.

In context, these Amazon carbon spikes are occurring at a time of record atmospheric CO2 increases. For the first seven months of 2016, the average increase in CO2 versus 2015 was 3.52 ppm. 2015’s overall rate of CO2 increase in the range of 3.1 ppm year-on-year was the fastest annual increase ever recorded by NOAA and the Mauna Loa Observatory. So far this year, the rate of atmospheric gain in this key greenhouse gas is continuing to rise — this in the context of carbon spikes over a region that should be drawing in CO2, not spewing it out.

Links:

Drought Shuts Down Amazon’s Carbon Sink

Amazon Could Face Intense Wildfire Season This Year, NASA Warns

The Keeling Curve

The Copernicus Observatory

NOAA ESRL

IPCC/CEF

LANCE MODIS

Hat tip to Colorado Bob

Hat tip to DT Lange

Global CO2 Spike Spurs Hottest June on Record, Extreme Weather For US

According to NOAA, the United States just experienced its hottest June ever recorded in the whole of the national climate record starting 122 years ago in 1895. That’s an average temperature of 71.8 F (22.1 C) across the contiguous United States — or 3.3 F (1.83 C) hotter than a typical June.

NOAA Record heat

(The United States just experienced its hottest June on record. The extreme heat comes alongside a period of record global warmth and helped to spur numerous extreme weather events across the country. Image source: NOAA.)

The new national June record broke the old record set back in 1933 and comes amidst a 13 month long streak of record hot months in the NOAA Climate measure. The record US heat also coincided with an extreme Southwestern heatwave, an apparently unquenchable California drought, record low Lake Mead water levels amidst a 16 year drought in the Colorado River basin, severe US wildfires, and the worst flooding in a hundred years to strike West Virginia.

Record heat — both at the national and at the global level — is a well-known driver of extreme weather events such as wildfires, droughts, and deluges. And NOAA shows that six of the past nine years have seen far above average damages due to severe weather — with 2016 tracking near the all time worst year (2011) for number of billion + dollar disaster events. Meanwhile, extreme weather attribution studies are increasingly providing a physical science basis for linking single and regional events with the larger global warming trend.

Heat Driven By Spiking Carbon Dioxide Levels

At the same time that national temperatures were hitting new record highs, average carbon dioxide levels measured by the Mauna Loa Observatory saw record rates of rise for the month. According to NOAA’s Earth Systems Research Laboratory, June of 2016 saw average carbon dioxide levels that were 4.01 parts per million higher than June of 2015. That’s a huge jump in the atmospheric concentration of a greenhouse gas that rose by about 1 part per million every year during the 1960s and during recent years has risen by an average of about 2 parts per million.

NASA CO2

(NASA graphic provides a stark paleoclimate contrast to the human carbon dioxide spike. The current rate of increase in atmospheric CO2 levels is faster than at any time in the last 60 million years and, possibly, faster than for any period in which life occupied planet Earth. Image source: NASA.)

Last year saw a record annual rate of atmospheric CO2 increase of around 3.05 parts per million. But the first six months of 2016 have so far greatly outstripped even 2015’s nasty rise — currently tracking 3.59 parts per million above the first six months of the previous year.

Record global greenhouse gas levels and a spike that is essentially vertical on geological timescales are, in greatest portion, driven by human fossil fuel emissions. These spiking levels of heat trapping gasses, in turn, drive extreme global temperatures and related severe weather events. But as the world’s land and ocean surfaces heat up, they tend to also draw in less of the human carbon emission even as they emit more. Expanding deserts, worsening wildfires, expanding ocean hot pools and thawing permafrost all add to this vicious cycle. And it’s possible that we’re starting to see rumor of these amplifying feedbacks starting to kick in now. Which makes the continued burning of fossil fuel that drives the whole vicious cycle an ever more dangerous prospect.

Links/Attribution/Statements:

NOAA

NASA

June Swoon — US Breaks Another Monthly Temperature Record

Bad Rains Fall Across the Globe

Water Knives in the Near Future

US Drought Monitor

Humans are Likely Culprits of Southern European Droughts

Scientific hat tip to Dr. Stefan Rahmstorf

Hat tip to DT Lange

Hat tip to Greg

Hat tip to Suzanne

A Fearful Glance at the Global Carbon Stores — Weekly CO2 Values Hit 404 Parts Per Million a Little Too Soon

mlo two years April 15

(Big jump in weekly CO2 averages during second week of April bring 2015 concentrations into the range of 404 parts per million a month earlier than expected. Image source: The Keeling Curve.)

Over the past decade, annual rates of atmospheric CO2 increase have remained in a range of around 2.2 parts per million (ppm) each year. It’s a geologically blinding pace of increase driven by a human carbon emission on the order of around 11 billion tons each and every year. Primarily driven by fossil fuel burning, this massive dumping of carbon into the atmosphere is steadily filling up a number of the world’s key carbon stores.

The oceans are brimming full with carbon — as we see in a rapidly rising rate of acidification.  The oceans are warming, steadily losing their ability to keep a higher fraction of greenhouse gasses stored in solution. The trees are lagging in their ability to draw carbon from the atmosphere — a symptom of a combined deforestation, wildfire proliferation, and endemic outbreaks of invasive species that prey on key trees. And the carbon store in the Arctic is showing signs that it may be actively venting higher volumes of greenhouse gasses back into the atmosphere and oceans.

As a leading indicator that some of these carbon stores are starting to fill up, or worse, dump a significant portion of their sequestered carbon back into the atmosphere, we would expect to see spiking levels of CO2 and CH4 in the global measures. Which is why when, starting on April 5 of 2015, Mauna Loa CO2 values shot up to around 404 to 405 parts per million in some of the hourly records, a few eyebrows were raised.

Implications of Hitting Expected Peak Values a Bit too Soon

Typically, atmospheric CO2 peaks around mid-May. And, for this year, following the 2.2 ppm increase trajectory, we would expect a May monthly value of around 404 parts per million. So readings in the range of 404 to 405 parts per million in early April are a significant jump well ahead of the expected marks. If this increase remained consistent and showed continued seasonal rise on through mid-May, it could skew April and May readings upward — well beyond a 2.2 ppm annual increase at peak.

mlo_one_month

(Consistently High CO2 values show up at the end of the monthly measure. Note the frequent hourly departures above 405 ppm. Image source: The Keeling Curve.)

Typically, the difference between April and May monthly values is in the range of 0.5 to 1 ppm CO2. So an April Average near 404 ppm could yield a May average of 404.5 to 405 ppm or a 2.7 to 3.2 ppm increase over 2014 peak values. A significant high departure that could be a leading indicator of a bad response from the global carbon stores. This possibility was raised as daily Mauna Loa CO2 values ranged from 403.2 ppm through 404.9 ppm from April 5 to 14 and as weekly values for April 8-14 hit 403.9 ppm.

Signal or Noise?

Of course, these admittedly worrisome spikes could well be noise in the overall carbon system. CO2 values have tended to vary more wildly in the Mauna Loa measure recently. And average rates of increase from peak to peak could still fall into the standard range.

It is also worth noting that any major disruption in the global carbon system as it relates to CO2 would also show up as a trailing indicator in the CO2 airborne fraction measure. A higher level of emitted CO2 would remain in the atmosphere as sinks began to fail and as stores became sources. Such a carbon sink failure would eventually show up as a higher airborne CO2 fraction.

Overall, the airborne fraction measure is an indicator of how much of the carbon human beings emit into the atmosphere is being taken up by the global environment:

CO2 Airborne Fraction

(Airborne CO2 fraction showing global carbon dioxide emissions [as gigatons of carbon without oxygen molecular weight added] since 1960 through 2012 and amount of emitted CO2 that has remained in the atmosphere. Image source: James Hansen and The University of Columbia.)

Currently, the amount of carbon from CO2 remaining in the atmosphere is in the range of 45% of the human emission — or around 5 gigatons.

If carbon sinks are retaining their ability to uptake CO2, then the fraction will remain relatively low. If carbon sinks are over-topping and bleeding substantial volumes of their carbon back into the atmosphere, then the airborne fraction measure will tend to rise as a trailing indicator.

During recent decades, the airborne fraction has actually fallen as emissions ramped up — probably due to a combined increase in ocean surface exposure to CO2 and to an initial bump in the rate of CO2 respiratory uptake by photosynthetic life. But considering the very high volume of carbon being dumped into the global system coordinate with a wide variety of stresses to carbon stores resulting from both added heat and chemistry changes, these carbon sinks are under ever-increasing stress. A number of scientific studies have indicated a likely rise in CO2 airborne fraction, under business as usual fossil fuel emissions, to as much as 80 percent through 2100 — with start of carbon store failures during the current decade.

If carbon stores do begin to fail, we would first see atmospheric spikes in the global CO2 and CH4 measures. Then, as a trailing indicator, the CO2 airborne fraction measure would begin to ramp up. In this context, weekly CO2 spikes at Mauna Loa are some cause for concern, but we can’t make any strong calls of a larger carbon system response without a more consistent spike and, eventually, a jump in the airborne fraction.

To this final point, I’ll leave you with the somewhat related Mauna Loa CH4 measure which has, lately, also been showing an increasing rate of accumulation for that greenhouse gas:

Mauna Loa Methane Measure 2004 to 2015

(Mauna Loa Methane measure shows ramping up of atmospheric CH4 readings at that station. Image source: NOAA ESRL.)

Links:

The Keeling Curve

Doubling Down on Our Faustian Bargain

Modeling The Atmospheric Airborne Fraction in a Simple Carbon Cycle Model

NOAA ESRL

Scientific Hat tip to Dr. James Hansen

Hat tip to Wili

Hat tip to Kevin Jones

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