Hi, just a short clarification:
The main point of our study is not that CDR is useless, but that it is
not effective enough to counteract business as usual CO2 emissions. Our
results stress, once again, that there is no alternative to immediate
emissions reduction - CDR can be deployed as a supplemental measure (and
maybe it should), but it would not be effective enough to reverse severe
changes caused by a delay in emissions reduction.
On alkalinity addition: How likely is it that we would be able to do
this on a global scale? I could imagine that alkalinity addition might
be a way to protect a coral reef, being deployed locally, but globally?
I guess it would be much harder to do than atmospheric CDR and you would
have to be very careful how much alkalinity you add and how often, to
not further stress marine organisms? As far as I know, there are hardly
any studies on this?
(By the way, our study is not only about ocean acidification, but also
about warming and oxygen depletion.)
Best,
Sabine
On 08/08/15 12:50 am, Greg Rau wrote:
If the goal is to restore ocean chemistry, it would indeed seem inherently
inefficient to do so via CO2 removal from air. Better to remove excess CO2
from the ocean by chemical, geochemical, or biological means (1), my favorite
being alkalinity addition.
Secondly, according to the IPCC (2) and now UNEP (3), RCP 2.6 scenarios cannot
be achieved without CDR - in the UNEP estimate, 300 Gts CO2 worth by 2100. So
while I don't think anyone is asking CDR to do all of the heavy lifting, it
would appear that at least some CDR is essential to achieve RCP 2.6 and
probably even less ambitious scenarios, depending on when/if we ever get
serious about emissions reduction. What then is the point of dissing CDR if
emissions reduction alone isn't going to save the ocean and the planet either?
1) http://link.springer.com/referenceworkentry/10.1007/978-94-007-5784-4_54
2) http://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter06_FINAL.pdf
3) http://www.unep.org/emissionsgapreport2014/
Greg
--------------------------------------------
On Mon, 8/3/15, Andrew Lockley <[email protected]> wrote:
Subject: [geo] Long-term response of oceans to CO2 removal from the atmosphere
To: "geoengineering" <[email protected]>
Date: Monday, August 3, 2015, 1:02 PM
http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2729.html
Long-term response of oceans to CO2 removal from the
atmosphere
Sabine Mathesius,1, 2,
Matthias Hofmann,1,
Ken Caldeira3,
& Hans Joachim Schellnhuber1, 4,
Nature Climate Change (2015):
doi:10.1038/nclimate2729
Published online 03 August 2015
Abstract
Carbon dioxide removal (CDR) from the atmosphere has been
proposed as
a measure for mitigating global warming and ocean
acidification. To
assess the extent to which CDR might eliminate the
long-term
consequences of anthropogenic CO2 emissions in the marine
environment,
we simulate the effect of two massive CDR interventions with
CO2
extraction rates of 5 GtC yr−1 and 25 GtC yr−1,
respectively, while
CO2 emissions follow the extended RCP8.5 pathway. We falsify
two
hypotheses: the first being that CDR can restore
pre-industrial
conditions in the ocean by reducing the atmospheric CO2
concentration
back to its pre-industrial level, and the second being that
high CO2
emissions rates (RCP8.5) followed by CDR have long-term
oceanic
consequences that are similar to those of low emissions
rates
(RCP2.6). Focusing on pH, temperature and dissolved oxygen,
we find
that even after several centuries of CDR deployment, past
CO2
emissions would leave a substantial legacy in the marine
environment.
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