SRM geoengineering as soon as possible?
John Nissen
Hi all,
I argue that we shouldn't wait for the sea ice to disappear, but get on with SRM geoengineering with due haste. This is what I wrote to John Shepherd and Ken Caldeira on this subject recently:
---
So I don't see any alternative to SRM for generally cooling the Arctic and saving the sea ice. (Reduction of black carbon would also help, as Tim Lenton points out, but I disagree with him that it could be an alternative.) It will have to be done eventually, but when is the best time? I would argue that the best time is as soon as possible, for a number of reasons:
- Positive feedback is building up;
- Less SRM is required if done sooner;
- Side-effects will be smaller, and more easily dealt with;
- There's a lot of uncertainty about how quickly sea ice could disappear;
- There is a risk that techniques do not work as well as expected;
- If one technique fails there is more time to modify it or develop alternatives;
- Deployment might have to be temporarily suspended for some
reason, and there would be more time to play with.
As you point out, deployment in both north and south high latitudes would be desirable to minimise chance of unbalancing the hemispheres, and because there are threats from polar amplification in both polar regions.
Probably the biggest side-effect risk is from disruption of monsoons, and one might want to reduce or suspend SRM in a period of high El Nino for example. And you would probably want to suspend SRM if there were a major volcanic eruption, ejecting sulphur into the stratosphere.
Deploying stratospheric aerosols would then buy time for the development and deployment of safer (even safer) but more expensive techniques, in particular the marine cloud brightening. Somebody has suggested this technique would take ten years - but with a crash programme, we should aim to have it ready much sooner - not only as an insurance policy, but it opens up options for a mix and match approach to SRM (e.g. stratospheric aerosols for general cooling, cloud brightening for more local cooling).
BTW, efforts to reduce sulphate aerosol pollution in the troposphere, e.g. from ships, should be subject to a moratorium, because their masking of global warming is so valuable.
---
Do you disagree with any of that?
Cheers from Chiswick,
John
chsee
I refer you back to the long discussions in <a href="http://
groups.google.com/group/geoengineering/browse_thread/thread/
69cfdba5a81d9846/8ea4216310ec8f1d?q=nissen+arctic
+srm&lnk=ol&">response to your 'simple argument for SRM
geoengineering'</a>
There is a danger that you pose the question, and since people do not
give the responses again that they gave before you assume they now
agree with you, or forget that they did not.
Your argument is predicated on the idea that artic sea ice melt will
feedback into permafrost melt, methane release, and greenland melting.
Yet you say nothing of timescales except that SRM is urgent and 'will
have to be done eventually'. No-one would argue that a warmer arctic
will have less ice, less permafrost and release more methane but the
speed and extent to which this will happen is much less clear.
I do not agree that a <u>necessity</u> (urgent or otherwise) to cool
the Arctic via SRM is demonstrated. Further, you acknowledge the
unquantified but potentially significant environmental risks. Despite
this you advocate SRM as sson as possible. Has anyone done any work
modelling rates of permafrost melt and methane release in a BAU vs SRM
scenario?
Let's say I know nothing at all about SRM geoengineering. Who should I
take advice from? David King or John Nissen?
Or perhaps I read Science: Robock et al argue "stratospheric
geoengineering cannot be tested without full-scale implementation".
Blackstock and Long say "Eventually, confirming the effectiveness of
an SRM scheme would require large-scale tests with demonstrable
climatic impacts - essentially low-level deployment." And they add "it
will be extremely difficult to attribute impacts and unintended
consequences to any test."
On your specific seven points:
1&2) Less SRM needed if sooner: perhaps; but how much less if we were
to wait 5 years? 10 years?
3) Side-effects lesser and easier to deal with if sooner: assumption.
Also how will 'side-effects' be 'dealt with'? Easy to say but hard to
do. And it will be hard to separate 'side-effects' from natural
variation. Is there a risk of cascading geoengineering schemes to
solve percieved side-effects, followed by another to solve that one's
side-effects and so on?
4&5) Uncertain ice melt trajectory and SRM efficacy: agreed, but that
is an argument for more caution and patience not less.
6) Need for another technique if first fails: difficulty of
attribution. What will failure look like? Success?
7) Possible need to suspend and therefore need for more time to play
with: urgency? plus see 1&2
As to a moratorium on SO4 controls for ships &c, there are good health
and environmental reasons why these controls were brought in. I would
have thought it necessary to carefully weigh up these reasons against
potential climate benefits before advocating a moratorium.
ie "their masking... is so valuable": how valuable? and how valuable
are the benefits of controls? An interesting question but not a simple
one. I imagine there is some research on this. Anyone?
best,
simon evans
The ENDS Report
London
+44(0)2082678135
On Feb 1, 10:19 pm, John Nissen <j...@cloudworld.co.uk> wrote:
> Hi all,
> I argue that we shouldn't wait for the sea ice to disappear, but get on with SRM geoengineering with due haste. This is what I wrote to John Shepherd and Ken Caldeira on this subject recently:
> ---
> So I don't see any alternative to SRM for generally cooling the Arctic and saving the sea ice. (Reduction of black carbon would also help, as Tim Lenton points out, but I disagree with him that it could be an alternative.) It will have to be done eventually, but when is the best time? I would argue that the best time is as soon as possible, for a number of reasons:Positive feedback is building up;Less SRM is required if done sooner;Side-effects will be smaller, and more easily dealt with;There's a lot of uncertainty about how quickly sea ice could disappear;There is a risk that techniques do not work as well as expected;If one technique fails there is more time to modify it or develop alternatives;Deployment might have to be temporarily suspended for some reason, and there would be more time to play with.We do not know how well stratospheric aerosols would work - especially because of unknown droplet size, movement in air currents, and lifetime. Therefore, I would suggest that some field-trials are started for stratospheric aerosols at high latitudes in spring (to reduce ozone depletion risk) - ideally next spring in/near Arctic, but otherwise next spring in/near Antarctic. Balloons and/or high-flying aircraft could be used. Monitoring could be by instrumented balloons, if suitable satellites are unavailable.