Hi All
Was there never a mention of tropospheric marine cloud brightening?
Stephen
Emeritus Professor of Engineering Design. School of Engineering,
University of Edinburgh, Mayfield Road, Edinburgh EH9 3JL, Scotland
[email protected], Tel +44 (0)131 650 5704, Cell 07795 203 195,
WWW.homepages.ed.ac.uk/shs, YouTube Jamie Taylor Power for Change
On 08/07/2015 08:57, Andrew Lockley wrote:
http://www.spp-climate-engineering.de/symposium-blog-single/items/day-1-could-we.html
Day 1 - Could we?
07.07.2015 22:42 (comments: 0)
tl_files/ce-projekt/media/aktuelles/Day1_07.png
Day 1: Tuesday July 7, 2015 - Berlin-Brandenburg Academy of Sciences
and Humanities
Although many hold high hopes for the next international climate
conference in Paris this winter (COP 15), evidence suggests that
environmental, technological, economic and social inertia will prevent
the world's major polluters from reducing carbon dioxide emissions
fast enough to prevent dangerous climate change. This has led to the
increased consideration of a range of Climate Engineering (CE)
technologies, which can be grouped into two main categories; Carbon
Dioxide Removal (CDR) methods, which aim to reduce the levels of
carbon dioxide (CO2) in the atmosphere, allowing outgoing long-wave
heat radiation to escape more easily, and Solar Radiation Management
(SRM) methods, which aim to reduce the net incoming short-wave solar
radiation and thus warmth reaching the Earth. While SRM technologies
may be able to reduce the risks associated with rapid climate change,
they do not represent an alternative to carbon management. As Klaus
Lackner outlined in today's introductory lecture, the inherent inertia
of the global carbon system means that stabilizing emissions to meet
the 2 degree target outlined by the IPCC requires not only the
reduction of global net emissions to zero, but also implies the need
for negative emissions. Therefore, as the symposium's opening
presentation emphasized, a deeper understanding of the feasibility of
both CDR and SRM technologies is needed as soon as possible.
This week's symposium aims to deal with a wide spectrum of Climate
Engineering related questions, but today's session focused on what is
arguably one of the most fundamental of them all: Could we do it? [1]
Entitled "Scientific Feasibility of Climate Engineering Ideas," the
first session of the week included talks by seven natural scientists
and engineers who addressed the "Could we?" question from different
perspectives.
We were updated on a plurality of practical CE puzzles being addressed
around the world. First, Jon Egill Kristjansson told us about the fine
line a potential cloud seeder would have to walk by seeding small,
homogenous ice nuclei in cirrus clouds, which then cool the planet by
letting more long-wave radiation out, but making sure not to
"over-seed", as injecting too many nuclei would mean reduced solar
reflection and subsequently more warming. We heard that although
initial modeling on cirrus cloud "thinning" in this manner indicates
that the method is scientifically feasible, as one member of the
audience pointed out, very little is known about its technical
feasibility. The creation of small, homogenous ice nuclei in cirrus
clouds could cool the planet, but a multitude of questions remain
regarding how, where and under what conditions such particles can be
successfully created.
tl_files/ce-projekt/media/aktuelles/Day1_11.png
The second speaker, Rolf Müller, filled us in on how little is
currently known about the way in which injecting sulphates into the
stratosphere may affect the ozone layer. He went on to emphasize that
future models need to look at the sensitivity of chlorine particles
and moisture when assessing the effects of sulphur-based Solar
Radiation Management (SRM) techniques. In a related talk on the
technical complications associated with getting sulphur particles up
into the stratosphere some 20 km above our heads, Hugh Hunt explained
that delivering 10 million tonnes of particles a year using aircraft
would roughly double today's global aviation traffic, requiring
approximately 30,000 flights per day. A potentially much less
expensive (and considerably quieter) alternative involving only 10
tethered balloons with hoses attached, delivering a steady flow of
particles at a rate of 300 kg per second would seem a much simpler
option. But then we heard about the troubles the wind poses for this
type of delivery system, the fact that a tether strong enough hold an
enormous balloon 20 km above the Earth's surface for an indefinite
period does not yet exist, and the fear that CO2 pumped up such a long
hose would need to be under such high pressure that it would solidify
rather than "flow steadily" as originally envisioned. Other open
questions raised in the subsequent discussion included the suitable
framing of future tests; potential incompatibility between the
scientifically optimal location for the launch of such balloons and
the technical practicalities involved (weather conditions, population,
flight paths etc); and the concern that successful initial testing may
lead to the method becoming increasingly "politically tempting."
tl_files/ce-projekt/media/aktuelles/Day1_12.png
Coming down from the heavens, Lena Boysen followed with her talk
focused on the potentials of terrestrial CO2 sequestration using
biomass plantations. Although these sequestration alternatives are
often considered attractive and "green," today we heard that they are
likely to have a multitude of side-effects on the water cycle, food
production, biodiversity and the planet's albedo. Additionally,
modeling results suggest that even dramatic shifts in land use would
not remove enough carbon from the atmosphere to reduce warming
significantly: Even simulated so-called 100% replacement scenarios in
which all agricultural land was replaced with biomass plantations did
not result in a dramatic reduction in warming within the model
parameters. Greening the planet may be desirable for a variety of
reasons, but this presentation suggested afforestation alone will not
be enough to reduce warming significantly.
The final two presentations on this warm Tuesday in Berlin [2] focused
on olivine accelerated weathering, with Peter Köhler looking at ocean
fertilization and Thorben Amann discussing the effects of element
release as a consequence of land-based weathering. A simulated CO2
removal experiment on the role of iron during olivine dissolution in
the open ocean showed that the size of the olivine grains played a
huge role in the effective dissolution: Too large and they sink, too
light and they remain in the surface layers. Questions were raised by
members of the audience about how the grains of the optimal size would
be sourced - would naturally ground small particles be transported
from beaches, or would larger particles be ground, and how would the
energy use of the two options compare? The land-based use of ground
rock particles poses different problems - during the final
presentation of the day, Thorben Amann indicated that although the
particles can release fertilizing nutrients which could be beneficial
to agriculture, the rock types with most enhanced weathering carbon
capture potential also contain trace heavy metals. The use of this
method would therefore boil down to a trade-off between fertilising
potential, trace metal release level and CO2 capture potential.
After a long, interesting day of talks, we found ourselves trickling
out of the conference hall with even more questions to ponder. Today's
speakers showed us that before an answer to the deceptively simple
query posed at the start of this post can be found, a multitude of
much more complex questions remain to be answered
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