I’ve been following this though it is far away from my focus on mitigation and
I may well be missing something obvious here.
Reto’s answer makes sense to me. If CO2 emissions cease, the warming caused by
the elevated CO2 concentration remains, but only in holding the new
equilibrium temperature (with some short term lead-lag dynamics). Just holding
a new equilibrium temperature requires warming - that’s what the
greenhouse effect does. Ceteris paribus, as CO2 gradually comes out of the
atmosphere so the temperature gradually declines. Changes in aerosols,
non-CO2 GHGs, carbon-cycle feedbacks etc all make for a more complicated
picture, but the fundamentals of Reto’s argument certainly hold to this
simple engineer.
As a thought experiment - and if the counter were true - the temperature would
have continued to rise with the pre-industrial CO2 concentration -
indeed any set concentration of CO2 would see an ongoing temperature rise
forever … which would not fit into the physics I recall from school - or
my engineering thermodynamics. But as I say I may well be missing something.
Kevin (Anderson)
On 18 Nov 2016, at 10:48, John Nissen <[email protected]> wrote:
Hi Mike,
I am astonished by Reto’s answer to my simple question about what would happen
if CO2 emissions were to cease overnight. All I have ever
been told about greenhouse gases is that they have a warming effect on the
planet. How could this warming effect be suddenly cancelled by
the cessation in emissions of the main greenhouse gas, CO2?
Reto is completely out on a limb as far as I am concerned.
You have pointed out that, not only would the greenhouse effect of the existing
CO2 in the atmosphere continue, but that aerosol cooling
would also be removed (e.g. in the turning off of coal-fired power stations
which emit SO2), leading to an even faster rate of temperature
increase, albeit temporarily.
You quoted from Phillip Williamson:
“With regard to Mike McCracken's email below, if all emissions were to be very
rapidly (instantly?) ended, the outcome is likely to be
accelerated warming over the short-term, since the cooling effect of aerosols
would be reduced more rapidly than the warming effects of
greenhouse gases. See FAQ 12.3 of IPCC AR5 WG1.”
Cheers, John
On Fri, Nov 18, 2016 at 4:09 AM, Michael MacCracken <[email protected]>
wrote:
I'd just note that one also has to consider tropospheric ozone response,
and the methane effect would also likely have an
influence over the first decade, so a lot to consider, though I agree
that the loss of the sulfate cooling influence is indeed an
important aspect to consider.
Mike
On 11/17/16 2:08 PM, Phillip Williamson (ENV) wrote:
Dear all
Two short comments on the latest postings in this very informative
exchange:
1. With regard to Mike McCracken's email below, if all emissions were to
be very rapidly (instantly?) ended, the outcome
is likely to be accelerated warming over the short-term, since the
cooling effect of aerosols would be reduced more rapidly
than the warming effects of greenhouse gases. See FAQ 12.3 of IPCC AR5
WG1.
2. With regard to Bernard Mercer's separate email sent just a few minutes
earlier, I am particularly interested in "I
think you would find non-profit foundations falling over themselves to
fund syntheses, but they need well-thought through
proposals!". That's because the UK Greenhouse Gas Removal programme
(http://www.nerc.ac.uk/research/funded/programmes/ggr/), led by the
Natural Environment Research Council, is likely to be
in the situation in a few months time that it is only able to fund a
minority of high quality proposals - including
syntheses - considered worthy of support. If anyone has suggestions for
additional co-support partnerships, e.g. via
foundations, I would be pleased to explore such possibilities and bring
them to the attention of the current GGR programme
funders
Regards
Phil Williamson
___________________________________________________________________________________________________________________________________________________
From: [email protected] <[email protected]> on behalf of
Michael MacCracken <[email protected]>
Sent: 17 November 2016 18:26
To: [email protected]; John Nissen
Cc: David Lewis; geoengineering; Kevin Anderson; [email protected];
Greg Rau; Peter Wadhams; Sev Clarke; Alan Gadian;
Kevin Lister; Kevin Lister; Adam Rutherford - Science; Hugh Hunt
Subject: Re: [geo] Negative Emissions: Arrows in the Quiver, Life Preserver,
and/or Moral Hazard?
I would just add that if one considers the effects of short-lived species like
methane, black carbon, sulfate and tropospheric
ozone that also introduce substantial forcings, going to zero CO2 emissions
would also likely imply going to (near) zero
emissions of these species as well, so there is lots of potential for reducing
forcing and stopping the increase in temperature
and even pushing it down (with all emissions going to zero)--the challenge is
doing something so large in a short time.
Mike
On 11/17/16 12:25 PM, Knutti Reto wrote:
Dear John,
Thanks for your comments.
> I would love you to publish this result if you can.
Why would I want to publish it if it is wrong? To publish a result you need to
provide quantitative evidence. Claiming that
someone else is wrong is not enough. The figure you show is based on a climate
carbon cycle model, so please tell me what
specifically is wrong in that model (and in all other climate models that show
similar results), and provide another model
that is more credible, then we can discuss again.
In your letter to COP22 you state:
>The climate community and consensus of scientists, represented by IPCC, had
assumed that, by reducing net emissions of CO2
to zero, global warming could be halted. They had also assumed that such a
reduction would halt Arctic warming, by the
process which has kept Arctic warming proportional to global warming but
amplified by a factor of around two.
Unfortunately evidence indicates that these assumptions are no longer valid.
So “evidence indicates”, but where it that evidence? In your whole letter not
one quantitative argument or number is given
that contradicts the scientific consensus as represented in IPCC, not a single
one. What is the evidence?
You also assert that the scientists “assume” things. These are *results* based
on our best understanding of the system, the
best data we have, and the most objective and quantitative models we can build.
They may not be perfect, but they are
*results*, conclusions drawn from data, not assumptions.
>The temperature curve in red is complete nonsense, because the forcing from
the ~500 ppm of CO2 will continue the
radiative forcing on the planet and hence the temperature will continue rising.
In my previous email I demonstrated that the forcing will decrease, and that
temperature will not increase for long if the
forcing decreases, based on basic conservation of energy and timescales of the
carbon cycle. You can go back to work by
Wigley, Hansen and others thirty years ago and it’s there, and nobody has
disproven it. You provide no counterargument but
simply restate your claim. See my other email to Kevin. This is about science,
not beliefs. I don’t see this discussion
going anywhere.
Best regards,
Reto
From: John Nissen [mailto:[email protected]]
Sent: Donnerstag, 17. November 2016 02:48
To: Knutti Reto <[email protected]>
Cc: Michael MacCracken <[email protected]>; David Lewis
<[email protected]>; geoengineering
<[email protected]>; Kevin Anderson
<[email protected]>; [email protected]; Greg Rau
<[email protected]>; Peter Wadhams <[email protected]>; Sev Clarke
<[email protected]>; Alan Gadian
<[email protected]>; Kevin Lister <[email protected]>; Kevin Lister
<[email protected]>; Adam
Rutherford - Science <[email protected]>; Hugh Hunt
<[email protected]>
Subject: Re: [geo] Negative Emissions: Arrows in the Quiver, Life Preserver,
and/or Moral Hazard?
Hi Knutti,
I would love you to publish this result if you can. A number of us have been
trying to defy the modelling community which
seems to manage to get results which conflict with observations and, I
belatedly find, with basic physics. We have been
bombarded with weasel words, as Stephen Salter puts it. But it is this diagram
attached that astonished me, because it
shows up the basic premise, promoted by IPCC, that cessation of emissions will
cause the temperature to peak and start
falling. The temperature curve in red is complete nonsense, because the
forcing from the ~500 ppm of CO2 will continue the
radiative forcing on the planet and hence the temperature will continue rising.
It is when we try to reduce CO2 from its peak that we get into trouble, because
the 50% CO2, absorbed by land and ocean
when we put a certain amount of CO2 into the atmosphere, will then be emitted
by land and ocean. We have to work twice as
hard to reduce CO2 level as one might have thought: taking two tons out to
reduce the amount in the atmosphere by one ton.
It sounds like common sense to say that "our CO2 emissions caused global
warming, so ceasing our CO2 emissions will stop
the temperature rising". I can see why IPCC was tempted to promote this
nonsense: they wanted a simple story for the
public. But it's simply not true.
I am copying in Adam Rutherford as an impartial scientist, not bound up in the
politics of climate change or the
machinations of IPCC and COP. I have been putting my point to several
distinguished climate scientists, and they can't
fault my physics. They will argue endlessly about other points, but not my
point on the basic physics: that zero emissions
won't halt temperature rise.
I am also copying to Hugh Hunt, who I hear is at COP22, so could pass on this
message.
Of course the implications are huge: we have a colossal challenge to remove CO2
fast enough from the atmosphere to avoid
dangerous climate change. We have to start immediately on a CDR initiative -
which I had hoped COP22 would do (hence the
letter to COP which I wrote and attach again for Hugh's benefit). On the other
hand the rewards of restoring the Earth
System to Holocene conditions would be fantastic. The possibility of doing so
is really good news for everyone on the
planet.
BTW, I have been spending most of my energy over the past few years on battling
against the modelling community about the
Arctic sea ice, observed to be in exponential decline as should be expected
from the physics of positive albedo feedback.
I only realised in January this year how badly we've also been led astray on
the CO2 front when I did a few simple
calculations for myself.
Kind regards, John
On Wed, Nov 16, 2016 at 9:34 PM, Knutti Reto <[email protected]> wrote:
Dear John,
> The arithmetic gives a frightening answer, which I expect is why you never
hear it and nobody publishes it.
Nature and Science love frightening results and would be happy to publish those
if they are correct. But not if they
contradict the evidence we have. You seem to imply that scientists only publish
what they like or what people want to
hear. I don’t see any evidence for that. If I had strong evidence for things
being much worse, I would publish that
tomorrow. Same if I could prove that climate change is a hoax. We are not
“selling a dream to the media, politicians,
environmentalists and the UN”, we publish and assess what the science and the
data tell us.
There are two main errors in your analysis:
> The CO2 would only fall very slowly for the rest of the century, because of
CO2's long life in the atmosphere.
Thus the forcing from nearly 500 ppm CO2 would persist for the rest of the
century.
First, the initial decrease of CO2 isn’t that slow for zero emissions because
the exchange with the surface ocean and
land is fast. CO2 doesn’t have a single lifetime, and it’s the long tail that
is slow. For a single pulse emission
into the atmosphere, after 50 years only half remains in the air (Joos,
doi:10.5194/acp-13-2793-2013, Fig. 1a).
Second, other gases would also be reduced and some have shorter lifetimes. Even
without going abruptly to zero, e.g.
as in RCP2.6, the radiative forcing decreases after 2050. For zero emissions in
2050 the forcing would drop more.
> Even if the warming rate remained at only 0.25C for the rest of century,
temperature would rise a further 1.25C to
reach 3.2C above pre-industrial.
That is simply wrong. There is no reason for the warming rate to remain the
same if the forcing decreases. For
*constant* forcing (today) the additional warming is about 0.5°C after 200
years (IPCC AR5 WG1 p.1103 bottom left).
For 50 years it’s about half (Knutti, 2008 doi:10.1029/2007JD009473, Fig. 1b).
That is for constant forcing, so
obviously for *decreasing* forcing it’s even less. RCP2.6 temperature is
constant after 2050, it doesn’t increase. As
I said before, the climate system is complex, but conservation of energy is
not. Look at the simple Q=F-lambda T
discussed below: if forcing F is constant or even decreasing, then temperature
T only increases a bit because heat
uptake Q reduces, but in equilibrium T is proportional to F. So the assumptions
that T would continue to increase at
the same rate if F is decreasing violates conservation of energy.
We are in the fortunate position to have dozens of simple and comprehensive
climate models which have run such
scenarios, and the models do incorporate all those timescales in the climate
and carbon cycle, they include other
gases, and the feedbacks. RCP2.6 has zero CO2 emissions around 2075 (IPCC AR5
WG1 Fig. TS.19, p. 94) and stays
“likely” below 2°C relative to preindustrial (IPCC AR5 WG1 SPM p.20). Zero CO2
emissions in 2050 would result in less
warming than that.
Even if the models underestimate the Artic sea ice loss, that would not change
those numbers a lot. The albedo
feedback is only about a quarter of the total global feedback (IPCC AR4 WG1
Fig. 8.14, p.631). Even the models with
the steepest sea ice decline do not support your analysis. No model is perfect,
but I’d rather base my conclusions on
the best possible representation of all processes, the best data, and a
quantitative analysis, than on a naïve and
wrong extrapolation of past trends. Climate change is a serious issue, but it
doesn’t help if people go out with
scary extrapolations that have no scientific basis.
Best regards,
Reto
From: John Nissen [mailto:[email protected]]
Sent: Mittwoch, 16. November 2016 11:45
To: Knutti Reto <[email protected]>
Cc: Michael MacCracken <[email protected]>; David Lewis
<[email protected]>; geoengineering
<[email protected]>; Kevin Anderson
<[email protected]>; [email protected]; Greg
Rau <[email protected]>; Peter Wadhams <[email protected]>; Kevin Lister
<[email protected]>; Sev
Clarke <[email protected]>; Alan Gadian <[email protected]>
Subject: Re: [geo] Negative Emissions: Arrows in the Quiver, Life Preserver,
and/or Moral Hazard?
Hello Knutti,
The arithmetic gives a frightening answer, which I expect is why you never hear
it and nobody publishes it.
Suppose the CO2 level had got to 500 ppm by 2050, when net emissions reached
zero. The CO2 would only fall very
slowly for the rest of the century, because of CO2's long life in the
atmosphere. Thus the forcing from nearly 500
ppm CO2 would persist for the rest of the century.
The current underlying trend rate of global warming is somewhere between 0.2C
and 0.3C per decade, given that the
average rate over the past 45 years was 0.18C per decade [1]. Taking 0.25C as
a conservative average till 2050, and
assuming we have had 1.1C global temperature rise since pre-industrial times,
the global temperature would rise 0.85C
by 2050 to reach 1.95C above pre-industrial. Even if the warming rate remained
at only 0.25C for the rest of
century, temperature would rise a further 1.25C to reach 3.2C above
pre-industrial.
Unfortunately leading climate scientists, in their efforts to get CO2 emission
reduced, sold a dream to the media,
politicians, environmentalists and the UN: that we can adapt to climate change
providing net emissions are reduced to
zero over the next few decades.
According to this dream, the sea ice will last indefinitely, see the figure
SPM.7(b) reproduced in Peter W’s book,
page 89. Sea level will rise about half a metre this century: 44cm is the
‘best estimate’ in range 28cm to 61cm
maximum according to AR5 [2]. There is no need for interventions, except possibly some
"negative emissions" to
achieve net zero emissions. We can make the planet safe for future
generations. But it is a dream.
The reality is that we need to reduce the net effect of climate forcing agents
to zero, which includes restoring
Arctic albedo. Saving the sea ice is crucial. We risk losing a critical
element of the control of the planet’s
climate system if we allow the Arctic Ocean to become seasonally free of sea
ice, since it will probably be locked
into this state indefinitely which could have catastrophic consequences for sea
level rise, methane emissions and NH
weather extremes. The Arctic has already warmed 7C according to Peter Carter.
The most natural climate restoration CDR involves putting carbon into trees,
soil and marine biomass. This simply
involves improving forestry, agriculture and aquaculture practices on a massive
scale. It is also returning the
planet’s biosphere to a state before human population explosion when forests
were cut down, soils denuded of carbon
and marine biomass reduced. Surely this can only be good for the planet – and
something positive that every
environmentalist can work for.
We can also use weathering of crushed olivine rocks on a large scale to
neutralise CO2 and halt ocean acidification.
This, together with local cooling, could save corals – even possibly the Great
Barrier Reef. (Diatoms might help
purify the water.)
Who is standing in the way of this progress towards a safer planet? It is the
scientists who continue to promote a
dream: a totally unrealistic scenario of the future and a plan to get there.
COP is just doing what seems to be
required from this plan, though they know they cannot get to net zero emissions
quickly enough with current pledges.
And Trump now could throw a spanner in the COP works.
However the plan is doomed, not because of Trump, but because it is based on a
dream. We now need to focus on
reality and how we can use CDR and albedo enhancement to restore the Earth
System back to the Holocene norm, with
potentially huge benefits for humanity and biodiversity.
Kind Regards, John
[1]
https://www.theguardian.com/environment/2016/oct/03/global-temperature-climate-change-highest-115000-years
[2]
http://www.realclimate.org/index.php/archives/2013/10/sea-level-in-the-5th-ipcc-report/
On Tue, Nov 15, 2016 at 11:38 PM, Knutti Reto <[email protected]> wrote:
Dear John,
> an embarrassment to IPCC, as it conflicts with their story that global
warming can be restricted to 2C or
even 1.5C by getting net CO2 emissions to zero. This is obviously not true
from the physics, as I pointed out
to you and some other distinguished scientists a few days ago without
challenge! When net emissions fall to
zero the rise in atmospheric CO2 flattens off but the climate forcing remains,
so temperature will continue
rising. I wish I was wrong about this, and we could halt temperature rise so
easily. But, if we are halt
global warming we have to reduce the net forcing from all radiative forcing
agents, including Arctic albedo
loss, to zero.
I don’t deny the need for strong mitigation, but let’s try to inform decisions
by the best possible science.
Where is the evidence that zero CO2 emissions soon (say before 2050) would be
insufficient to limit warming to
2°C. Please send me the papers or your analysis. I’d like to know what is
“obviously not true from the
physics”.
If by “halt global warming” you mean limit/stabilize warming at some level
above preindustrial (e.g. 1.5 or
2°C), then your statement is simply wrong: net forcing does not need to be zero
as I showed below. By
definition net zero forcing implies zero warming in after sufficient time,
because the forcing is defined as an
anomaly from a reference temperature, typically preindustrial.
Best regards,
Reto Knutti
From: John Nissen [mailto:[email protected]]
Sent: Dienstag, 15. November 2016 14:53
To: Michael MacCracken <[email protected]>
Cc: Knutti Reto <[email protected]>; David Lewis
<[email protected]>; geoengineering
<[email protected]>; Kevin Anderson
<[email protected]>;
[email protected]; Greg Rau <[email protected]>; Peter Wadhams
<[email protected]>; Kevin
Lister <[email protected]>; Sev Clarke <[email protected]>; Alan Gadian
<[email protected]>
Subject: Re: [geo] Negative Emissions: Arrows in the Quiver, Life Preserver,
and/or Moral Hazard?
[Please excuse if this arrives twice]
Hi Mike,
I suppose I might have expected you to loyally defend IPCC. But their position
is untenable.
On the sea ice, Peter Wadhams presented the death spiral to an audience of sea
ice modelling experts at the
Royal Society, and not a single person rose to say it is not happening. The
exponential trend of sea ice
volume decline has been followed until 2012, and even the subsequent volume
estimates (which are tricky due to
so much broken ice and surface slush) are within natural variability.
Therefore on the precautionary principle
we must act on the expectation of losing sea ice at the end of summer within a
few years, despite what
modellers might hope.
Peter Wadhams points out in his book that the trend towards nearly ice-free
conditions in September is
"blindingly obvious" and he cannot understand why IPCC clings to models. "The
trend in the PIOMAS data
effectively gives us a drop-dead date of about 2020 for summer sea ice" [1].
As Kevin Lister points out, a rapid demise of sea ice would be an embarrassment
to IPCC, as it conflicts with
their story that global warming can be restricted to 2C or even 1.5C by getting
net CO2 emissions to zero.
This is obviously not true from the physics, as I pointed out to you and some
other distinguished scientists a
few days ago without challenge! When net emissions fall to zero the rise in
atmospheric CO2 flattens off but
the climate forcing remains, so temperature will continue rising. I wish I was
wrong about this, and we could
halt temperature rise so easily. But, if we are halt global warming we have to
reduce the net forcing from all
radiative forcing agents, including Arctic albedo loss, to zero. This means we
have the huge challenge of
reducing levels of CO2, methane and other greenhouse gases to their
pre-industrial levels. And we have to
restore Arctic albedo.
When we have done all this, we will have saved the sea ice, halted sea level
rise from Greenland ice melt and
hopefully restored climate in the Northern Hemisphere, reducing the weather
extremes to their old level.
Thus we should be close to restoring the Earth System to the 'old norm' of the
Holocene in which our
civilisation developed and flourished.
In the process we can actually improve food production, as I point out in the
attached letter which I was
hoping could be presented to COP22.
Restoration is the only path to a safe future for our children and
grand-children. It can be done. It must be
done.
Best wishes, John
[1] Wadhams (2016) "A farewell to ice" page 88.
On Tue, Nov 15, 2016 at 7:38 PM, Michael MacCracken <[email protected]>
wrote:
Dear Knutti--Thank you for your note and full explanation. I have been
trying to point out these
misconceptions of John's for a number of years now. I hope your note will
finally convince him.
I have also been trying to convince him that the really significant drop
in albedo leading to large
amounts of additional solar absorbed comes when the fresh snow on ice
melts (presumably in late
spring), reducing the surface albedo from something like 70-80% to or
order 20-30% and that the
albedo effect of going from melting ice surface albedo to the albedo of
open water (with Sun at low
slant angle) will not lead to a catastrophic increase in the absorbed
heat in the fall (though it
may well set the situation up for an earlier melting of the snow surface
in the spring, etc.). What
would be really interesting to have is a graph of the amount of solar
heat uptake at the surface
over the warm season (I guess, as well, actually having a comparison of
what the uptake is now with
what it would be were there no sea ice).
Best regards, Mike MacCracken
On 11/15/16 2:18 PM, Knutti Reto wrote:
Dear John, all
As a coordinating lead author of IPCC AR5 WG1 (and someone how has done work on
these topics) I’m
surprised to read such comments.
> Blunder 1. IPCC has ignored the increasing loss of Arctic albedo, which is
already contributing
the equivalent of 30 ppm CO2 to the radiative budget, i.e. a quarter of the
forcing from CO2. […]
The first blunder is symptomatic of IPCC's treatment of the Arctic sea ice,
where they refuse to
accept the observations that it is in a death spiral, preferring to rely on
models of proven
inadequacy which predict that the sea ice will last for decades. You can read
all about it in
Peter Wadhams' new book "A Fairwell to Ice".
The change in albedo is part of every climate model as snow cover and sea ice
change. Indeed some
many models show smaller Arctic sea ice decline than observed. But the natural
variability is very
large (e.g. Kay 2011, Swart 2015, Screen 2013, 2016). There is no reason why
short term trends
could simply be extrapolated, and the predictions by Peter Wadhams of sea ice
disappearing by today
have not happened so far
(https://www.theguardian.com/environment/2012/sep/17/arctic-collapse-sea-ice,http://www.independent.co.uk/environment/climate-change/arctic-could-become-ice-free-for-first-time-in-more-than-100000-years-claims-leading-scien
tist-a7065781.html). Maybe the models are missing something, but it’s just as
plausible (and in
most scientist’s view more likely) that the models are largely consistent with
observations within
natural variability.
Many studies have used observations to recalibrate and weight models, and even
IPCC has explicitly
made projections for Arctic sea ice based on those models that best reproduce
various aspects of
sea ice (section 12.4.6.1). All of these studies indicate that using
observations point to a
somewhat steeper decline of Arctic sea ice (Boe 2009, Massonnet 2012, Mahlstein
2012, Wang 2013,
Notz 2016), but not a “death spiral”.
I’m not downplaying the strong changes in the Arctic, but the science suggests
a fairly linear (and
reversible) relationship between Arctic sea ice and temperature with large
variability
superimposed. In my view they do not support a “death spiral”.
>Blunder 2. IPCC has ignored the warming effect of accumulated CO2. They say
that global
temperature rise will be halted when net CO2 emissions have fallen to zero,
ignoring the effect of
accumulated CO2 and other forcing agents in the atmosphere.[…] The second
blunder can be
illustrated by AR5 WG1 figure 6-40 attached and available here [1]. The red
curves are supposed to
show the effect if net emissions were to suddenly fall to zero at 2050, when
CO2 has reached about
500 ppm. The temperature (red curve in bottom diagram) should continue to rise
as a result of the
forcing from 500 ppm CO2; but instead the temperature flattens off as if the
accumulated CO2 ceased
to have a warming effect!
Of course CO2 continues to have an effect, but as emissions are set to zero the
atmospheric
concentration and therefore forcing decrease.
>It is absolutely astonishing and frightening that such a fundamental mistake
can be made.
Where is the evidence for a fundamental mistake?
>If we want to halt global warming at any particular temperature, then we need
to bring net forcing
down to zero by the time that temperature has been reached.
No, that is simply wrong. The forcing has to decrease to compensate the slowly
decreasing ocean
heat uptake, but it does not have to be zero at any time to limit warming, not
even in equilibrium.
The global energy balance is Q=F-lambda*T where Q is heat uptake, F is forcing,
lambda is the
inverse of climate sensitivity and T is warming (see Knutti and Hegerl 2008 for
example). If today
F~=2.3 Wm-2 and Q~=0.9 Wm-2 and we want to keep T constant and Q=0 towards
equilibrium then F needs
to decrease to about 2.3-0.9=1.4 Wm-2 on the timescale on which the ocean warms
(decades to
centuries), but not zero. Climate is complex, but conservation of energy isn’t.
IPCC WG1 chapter 12 has an long discussion of the difference concepts of
commitment warming
(section 12.5.2) with plenty of references from different models going back
many decades. There is
even an FAQ 12.3 discussing that, and it also does discuss non-CO2 forcings.
There are models which
show some warming after zero CO2 emissions, and others that show some cooling,
but in general these
concepts of commitment warming are well understood. IPCC isn’t perfect, but
it’s probably the best
reviewed document on climate, with hundreds of scientist contributing. It seems
rather unlikely
that it would contain “fundamental mistakes”, and in my view the claims you
made here have no
scientific basis.
Best regards,
Reto Knutti, ETH Zurich
http://www.iac.ethz.ch/people/knuttir
Swart, Neil C., John C. Fyfe, Ed Hawkins, Jennifer E. Kay, and Alexandra Jahn.
2015. “Influence of
Internal Variability on Arctic Sea-Ice Trends.” Nature Climate Change 5 (2).
Nature Publishing
Group: 86–89. doi:10.1038/nclimate2483.
Kay, Jennifer E., Marika M. Holland, and Alexandra Jahn. 2011. “Inter-Annual to
Multi-Decadal
Arctic Sea Ice Extent Trends in a Warming World.” Geophysical Research Letters
38 (15): 2–7.
doi:10.1029/2011GL048008.
Screen, James a., Clara Deser, Ian Simmonds, and Robert Tomas. 2013.
“Atmospheric Impacts of Arctic
Sea-Ice Loss, 1979–2009: Separating Forced Change from Atmospheric Internal
Variability.” Climate
Dynamics 43 (1–2): 333–44. doi:10.1007/s00382-013-1830-9.
Screen, James A., and Jennifer A. Francis. 2016. “Contribution of Sea-Ice Loss
to Arctic
Amplification Is Regulated by Pacific Ocean Decadal Variability.” Nature
Climate Change 6 (9):
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From: [email protected] [mailto:[email protected]]
On Behalf Of John
Nissen
Sent: Montag, 14. November 2016 16:06
To: David Lewis <[email protected]>
Cc: geoengineering <[email protected]>; Kevin Anderson
<[email protected]>; [email protected]; Greg Rau
<[email protected]>;
Peter Wadhams <[email protected]>; Kevin Lister
<[email protected]>; Sev Clarke
<[email protected]>; Alan Gadian <[email protected]>
Subject: Re: [geo] Negative Emissions: Arrows in the Quiver, Life Preserver,
and/or Moral Hazard?
Dear David,
I think Klaus et al have the voice of realism. Global warming is far more
serious than we have
been led to believe, and without several rapid interventions, we are heading
for many degrees of
global warming this century.
IPCC are guilty of two colossal blunders in their projections of global
warming. The effect has
been to lull the international community into a false sense of security. Rapid
interventions are
now required to avoid a lethal combination of climate change, ocean
acidification and rising sea
levels. Here are the facts:
Blunder 1. IPCC has ignored the increasing loss of Arctic albedo, which is
already contributing
the equivalent of 30 ppm CO2 to the radiative budget, i.e. a quarter of the
forcing from CO2.
Blunder 2. IPCC has ignored the warming effect of accumulated CO2. They say
that global
temperature rise will be halted when net CO2 emissions have fallen to zero,
ignoring the effect of
accumulated CO2 and other forcing agents in the atmosphere.
The first blunder is symptomatic of IPCC's treatment of the Arctic sea ice,
where they refuse to
accept the observations that it is in a death spiral, preferring to rely on
models of proven
inadequacy which predict that the sea ice will last for decades. You can read
all about it in
Peter Wadhams' new book "A Fairwell to Ice".
The second blunder can be illustrated by AR5 WG1 figure 6-40 attached and
available here [1]. The
red curves are supposed to show the effect if net emissions were to suddenly
fall to zero at 2050,
when CO2 has reached about 500 ppm. The temperature (red curve in bottom
diagram) should continue
to rise as a result of the forcing from 500 ppm CO2; but instead the
temperature flattens off as if
the accumulated CO2 ceased to have a warming effect! It is absolutely
astonishing and frightening
that such a fundamental mistake can be made.
If we want to halt global warming at any particular temperature, then we need
to bring net forcing
down to zero by the time that temperature has been reached. This involves
bringing all GHGs down
to their pre-industrial level and restoring Arctic albedo, unless their
residual heating (positive
forcing) is counteracted by an equal amount of cooling (negative forcing), e.g.
from aerosols.
CDR has to suck CO2 out of the atmosphere faster than it is being emitted into
the atmosphere, in
order to bring the level down from over 400 ppm to pre-industrial 280 ppm.
Methane emissions have to be suppressed (including fugitive emissions from
coal, oil and gas
extraction) in order to bring the level down from 1850 ppb to pre-industrial
750 ppb.
The retreat of sea ice has to be halted and then Arctic albedo has to be
restored to its level of
at least thirty years ago.
Thus our best chance to halt global warming is through CO2 emissions reduction
(better than already
committed) combined with several immediate and aggressive interventions: CDR,
methane emissions
reduction, and rapid cooling of the Arctic.
As Klaus Lackner et al say in their comment, CDR is indeed like throwing a
lifebelt to a drowning
person. We need to start CDR as quickly as we can, to be as certain as we can
be to save the
planet.
In parallel we must suppress methane and cool the Arctic before we lose any
more albedo from snow
and sea ice retreat.
The ultimate objective must be to restore the Earth System to Holocene
conditions of climate
stability, ocean alkalinity and sea level constancy.
Cheers, John
[1]
http://www.ipcc.ch/report/graphics/images/Assessment%20Reports/AR5%20-%20WG1/Chapter%2006/thumbnail/Fig6-40.jpg
On Mon, Nov 14, 2016 at 4:55 PM, David Lewis <[email protected]> wrote:
Anderson could maintain his stance as a voice for realism while adding
his voice to
those calling for research into all forms of geoengineering. He could
compare the cost
of reducing emissions to the current cost of removing them from the
atmosphere, call
for a vigorous program of further research, then state that it is still
his opinion
that civilization needs to urgently and fundamentally transform its
social, economic,
and political relations if it wants to continue to exist.
Moral: Do not ignore or downplay potentially useful actions, especially
if you
have the time and resources to carefully evaluate them.
___________________________________________________________________________________________________________________________________________________
From: Greg Rau <[email protected]>
To: Geoengineering <[email protected]>
Sent: Friday, November 11, 2016 4:50 PM
Subject: [geo] Negative Emissions: Arrows in the Quiver, Life Preserver, and/or
Moral Hazard?
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http://science.sciencemag.org/content/354/6313/714.1
GR: Disclaimer - I was a co-signer.
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