Not a bad effort all in all by Joel Winston. Slightly making news out of an article that really only adds further confirmation to the 'not a free lunch' argument about climate engineering. Misses the point a bit (and he's not the first) that the key comparison is between engineering and unmitigated climate change. Yes, rainfall will change under CE for sure, but how does that compare to BAU??? especially in areas of higher vulnerability...
Interestingly, I suspect Steve Raynor, Hauke Schmidt and I all feel pretty similarly...
Deploying giant space mirrors and spraying particles from
stadium-sized balloons may sound like an engineer's wild fantasy,
but climate models suggest that the potential of geoengineering to
offset rising atmospheric carbon dioxide may be significantly
Through a variety of computer simulations used for reporting to
the Intergovernmental Panel on Climate Change (IPCC), the team
investigated a scenario where an increase in the world's
atmospheric carbon dioxide levels was balanced by a "dimming" of
Across all four models tested, the researchers showed that
geoengineering could lead to adverse effects on the Earth's
climate, including a reduction in global rainfall. They therefore
concluded that geoengineering could not be a substitute for the
reduction of greenhouse gas emissions.
However, in a field with divided opinion on geoengineering's
potential role in addressing climate change, some doubt the
significance of this conclusion. "From a policy standpoint, this
doesn't provide very helpful guidance to decision-makers," said
Steve Rayner of the Oxford Geoengineering Programme. "No
serious player in this field suggests that [geoengineering] could
ever be a substitute for mitigation and adaptation."
The leader of the research, Hauke
Schmidt of the Max Planck Institute, Germany, believes their
experiment still contributes important details on how the Earth's
systems might respond to geoengineering. "The first thing we
realised was that we had to 'dim' the sun 25 percent more than
expected, in order for the Earth's systems to show a response,
which translates to needing more geoengineering than previously
thought," says Schmidt.
A reduction in global rainfall is not necessarily an equal one.
"It becomes interesting when you look into the regional responses,"
continues Schmidt. "If you have just a carbon dioxide increase,
most models predict a global rainfall increase, but a strong
decrease in the Mediterranean and subtropics. But if you try to
balance this with geoengineering, these zones shift to Northern
Europe, Northern Asia and North America."
There's also the question of how effective these simulations are
in recreating real-world deployment of geoengineering. One
particular concern is the study's assumption of a quadrupling of
carbon dioxide levels. "If it ever gets to that stage, then we have
probably passed the point where geoengineering can be useful
anyway," says Rayner.
The researchers recognise this level is at the upper end. "But
one of the simulations we're running for the next IPCC has more
than a quadrupling of CO2," explains Schmidt. "That's called the
'business as usual' scenario, and it's not completely outside
The team have also run simulations with smaller (and perhaps
more realistic) CO2 increases and will publish results in the
upcoming months. But they say the extreme CO2 increase in this
first scenario helps to identify signals and understand how the
system responds. "From the point of view of a climate researcher it
is the most interesting scenario," continues Schmidt. "While those
who are interested in geoengineering applications may find it
One scientist particularly interested in geoengineering
Matthew Watson, leader of the volcano-inspired
Stratospheric Particle Injection for Climate Engineering (Spice)
project. The government-funded project was investigating the
potential effects of spraying solar-reflective sulphates into the
stratosphere from a 20 kilometre-high, stadium-sized balloon.
However, a scaled-down field test of a smaller balloon spraying
water droplets was
cancelled due to governance and patent issues.
Now Watson is concerned by the report's conclusions, which he
says could be used to suggest that geoengineering research is a
waste of time. "Only through combined modelling and field research
can we generate the evidence-base for a salient answer on whether
climate engineering is a good or bad idea," says Watson. "It's
vitally important that scientists are given the space within which
to ask and try to answer difficult questions."
To understand different components of the Earth's systems,
Schmidt agrees that a few experiments are necessary. "I'm not
generally against small-scale field experiments if they help us
understand processes in nature," says Schmidt. "But they should
obviously be benign, and we should be very careful." However,
small-scale field tests are also limited, Schmidt believes, with
climate simulations possibly being the only way to fully grasp the
long-term and large-scale climate effects of geoengineering.
Both options may have their individual limitations, according to
Watson. "That small-scale experiments are, by their nature,
incomplete is often used as an argument against climate
engineering, but that can also be said of models, which are, by
definition, imperfect." In addition to large-scale simulations,
Watson accepts the need for small, benign and well-governed field
experiments in the interim.
Despite the controversy on the best course of action to take,
there is agreement between all parties on the need to determine the
effects of geoengineering with confidence. But this confidence may
perhaps only be found by both peering through simulations to see
long-term global effects, and engaging in detailed examination of
field tests to assess the practical potential of specific
Watson says time is short: "Unfortunately, we don't have
hundreds of years before climate change really takes hold. So
researching climate engineering now is much better than undertaking
that effort only when it becomes clear it is necessary."