Posts
Robertscribber
does what he does so well – describe yet another positive feedback
while at the same time he tells people they can save the word by
voting for the war monger Hillary Clinton or adopt “alternative”
energy.
He
doesn't even adopt Paul Beckwith's three-legged barstool!
Carbon Sinks in Crisis — It Looks Like the World’s Largest Rainforest is Starting to Bleed Greenhouse Gasses
5
August, 2016
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.
(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.
(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 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 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:
Hat
tip to Colorado Bob
Hat
tip to DT Lange
No comments:
Post a Comment
Note: only a member of this blog may post a comment.