NZ climate scientists run from challenging questions

UPDATE: I forgot to add in the main post below, some of the main points in the briefing. One is that the IPCC's next report, AR5 will see an increase in its sea level predictions by 2100 from an upper limit of 60cm to more than 90cm and possibly 1.5 metres. Another, and this one had me smiling given previous correspondence with alarmists, debunked the oft repeated myth that methane clathrates and hydrates on the ocean floor pose a major threat. To their credit, despite everything else below, not even the IPCC team were prepared to go where Gareth Renowden routinely treads.  The IPCC/NZ briefing is available as a podcast from this page.

I've just attended a major briefing on climate change by the NZ Government's "leading" climate experts, David Wratt, Tim Naish, Andy Reisinger and a couple of others. As a propaganda exercise drip-feeding a largely tame media, it was exceptional. As an informed appraisal of the latest science, it was just plain wrong, and it was tightly controlled to avoid any of the main speakers being challenged.

First of all, our first choice of attendee, Dr Vincent Gray, was banned from the event held at taxpayer funded Ministry for the Environment. Investigate magazine was informed last night that Gray was not an approved, accredited journalist and therefore would not be permitted to attend. Our response was that this was a gross invasion by the State into dictating who, or who could not, write for or represent Investigate magazine, which had already been formally invited to send someone.

I told them last night that no Government agency had a right to dictate which journalists/columnists could represent a publication. I wanted Gray there because I'm on deadline and he was as well briefed on the latest science as I was, unlike many of the daily media in attendance.

Secondly, I attended and listened to a disappointingly out of date and out of touch with the latest science presentation from all the men involved.

When I began asking a couple of questions, I was muted, and told privately I would be allowed to ask some later. Instead, they opted not to unmute and closed the news conference with no further challenging questions.

I may post audio in due course, but at no time was I rude or impolite. Just asking firm questions. Here's the text I've just described:

First question, 11:10am

Investigate: Andy, you put up a slide suggesting a 1000 year residence time for CO2, I'm just looking at a list of peer reviewed studies. Nearly 99% of them suggest the maximum residence time of CO2 in the atmosphere is less than 10 years. Can you explain how you get to 1000 years please?

Reisinger: I've never seen a peer reviewed study that suggested a residence time of ten years, I'm afraid.

Investigate: I can quote you some (gives details). The only people I can see on this list who go beyond 20 years is the IPCC report of 2007.

Reisinger: Which contains a large amount of peer reviewed studies, and the most recent understanding of climate science.

Investigate: Well, how do we explain this list of 30 peer reviewed studies suggesting a residence time of ten years? Doesn't that have an impact on our presumptions about climate change?

Reisinger: As I say the most recent IPCC assessment statement of understanding does not actually support that.

Investigate: But these peer reviewed studies do.

Howard: Ian, I have to say, I'm a climate scientist too and I've never seen a peer reviewed study that suggests a residence time of ten years.

Investigate: I'll forward it through, but what I'm suggesting is that the science on this is not settled.

Wratt: I would disagree.

Howard: We'll have to agree to disagree.

The list of studies I was referring to is this one:

You can read more about the residence time of CO2 here:

http://jennifermarohasy.com/blog/2009/04/carbon-dioxide-in-atmosphere-5-15-years-only/

Or read Junge's study here showing 15 years RT

UPDATE: The IPCC's own report discloses CO2 may have a residence time as low as 5 years (and up to 200), and adds that not enough is known about this as it depends on different factors. Forget their obfuscation for political reasons, (this was buried in the fine print), the peer reviewed studies above are pretty unanimous and it would be a struggle for me to accept IPCC's high option as gospel in the face of the above.

What I'm curious about is how on Earth the NZ scientists can justify the extrapolation out to 1000 years! And for two leading NZ (and UN IPCC) scientists to deny knowledge of low CO2 residency beggars belief. It's there in the IPCC report.

Then a further question five minutes later:

Investigate: You mentioned about species extinction becoming a problem with global warming. Are you aware of Oxford University's statement that "alarming predictions that climate change will lead to the extinction of hundreds of species may be exaggerated" and that species adaptation, which biologists specialize in, has not been taken into account by climate scientists?

Reisinger: Well the study that's mentioned in that graph is not a study by climate scientists but biologists using the knowledge that was available at that time. And it is a moving field because we are only now seeing the warming and implications this has on various species. I'm not saying that this is a definite figure and all those species will die; as Howard was saying in his introduction adaptation can reduce some of those impacts, but it is very unlikely that adaptation would reduce the impacts from 25, 30% extinctions down to zero."

Investigate: Without tying it up on the one point, I'll just give you this synopsis from Oxford scientist Kathy Willis -

Ministry for Environment official: Ian, I don't want to interrupt you, but –

Investigate: She's made the point that the climate modeling and species modeling that's been done is far too obtuse –

MfE: We do have people waiting on line

Investigate [now muted] But these are relevant questions.

Here's what I got hit with:

[11:18:12 a.m.] Peter SMC (in private): I am happy to unmute you again if you will let me know through the chatbox that you have a question and wait on your turn to be called

[11:18:29 a.m.] You: that's ok...i have about eight further questions

[11:19:25 a.m.] Peter SMC (in private): Alright, noted. We will put you in the queue

[11:25:02 a.m.] You (to Peter SMC): By the way, having now listened to the presentation and seen the graphs, if this is state of the art science from NZ's perspective I'm appalled, just quietly.

[11:25:41 a.m.] You: Massive holes in the evidence, much built on suppositions, and often in contradiction to peer reviewed data

I waited patiently for a call that never came.

[11:33:04 a.m.] You (to Peter SMC): can i get some questions to Tim please

[11:40:22 a.m.] Peter SMC (in private): we are running short on time

[11:40:27 a.m.] Peter SMC (in private): I'll see what we can do

[Announcement that press conf had ended]

[11:41:09 a.m.] You: Peter...you assured me I could ask questions!

[11:43:40 a.m.] You: Questions that were not answered: Tim, you quote ice mass loss from Antarctica, but my understanding is we do not yet have full satellite coverage of Antarctica What is your evidence of mass loss given the incomplete data?

[11:44:32 a.m.] You: Greenland surface melt going through holes in the ice and lubricating ice sheets, found to be "inconsequential" in peer reviewed studies this past year. Your response?

[11:44:43 a.m.] Peter SMC (in private): Yes. You did get to ask questions, as many as anyone else in the room. Please do follow up by sending your questions to the researchers if you'd like further clarification. We can help coordinate if possible.

[11:45:04 a.m.] Sarah Gibbs: Which study is that in Ian?

I then cited the studies (Utrecht Uni; Uni of Washington/Woods Hole) that I'd printed on pages 185 to 187 of Air Con.

I then began by firing off other questions on the chat process addressed to the scientists, but visible to other media like Sarah Gibbs. Unfortunately the plug was pulled by MfE before I could save the updated chat.

So from memory, here are some of the questions I typed seeking answers to:

Question for Wratt: You cited the Antarctic warming study of Steig et al from earlier this year. Are you prepared to tell the media assembled here that in actual fact satellite records show no warming over Antarctica since 1980, despite rising GHG emissions, and in fact a cooling? Can you confirm that the Steig study you've shown the media contains errors?

Question for Wratt: You've stated there's been a temperature increase of 0.5C between 1980 and 1999 globally. Why did you not qualify that by pointing out the exceptional El Nino year of 1998 that pushed up temperatures? What is your comment on citing ten or twenty year cycles as proof of global warming?

Question for Wratt: Did any of the GCMs used by the UN IPPC forecasters predict the specific temperature deceleration that has occurred since 2002, despite rising GHG emissions?

Question for Wratt/Reisinger: Given that CO2 is central to UNIPCC and NZ government policy on climate, and your presentation this morning, what are the implications of the new University of Bristol study showing that the balance between airborne and absorbed CO2 has stayed the same since 1850, despite human-caused emissions rising from 2 billion tons a year to 35 billion?

Question for Wratt/Reisinger: The new study suggests terrestrial ecosystems and oceans "have a much greater capacity to absorb CO2 than had previously been expected". Doesn't this prove that the science on CO2 is nowhere near settled and in fact our understanding in the IPCC reports may be utterly wrong?

Question for Wratt/Reisinger: How much confidence can the media here have in this presentation, when its data conflicts with two peer reviewed studies in the past week suggesting emissions from deforestation have been grossly overestimated by the IPCC – in the words of one study "by at least a factor of two"?

Question for Tim Naish: You talk about the dangers of current warming in Antarctica leading to massive melt in as little as 300 years and sea level rises of many metres. How do you reconcile that with the study published in PNAS in 2006 on elephant seal colonies that proves elephant seals lived much further south than their current Ross Shelf breeding sites, between 600 BC and 1400AD, suggesting it was "substantially warmer [then] than at present". Is there evidence of a 7 metre sea level increase or decrease between 1000 and 1400AD that would correspond to massive melting from a much warmer Antarctica?

Question for Naish/Reisinger: You've portrayed massive sea level rise over time, and extended the IPCC estimates out. But given that sea level rise for the 20th century averaged 1.7mm a year, and recent studies such as Leuliette and Miller (2009) show SLR of only 1.5mm a year between 2003 and 2007 (supposedly the hottest decade), how accurate are your forecasts and what is the evidence in support of catastrophically rising sea levels?

In summary, my impression of the press briefing was "propaganda stunt", deliberately timed to hype up Copenhagen in four weeks. Given that AR5 is not due for release for several more years it was not a genuine justification for a press briefing.

Secondly, these scientists boasted that they or their NZ colleagues "controlled" the production of two of the four major IPCC AR4 reports. If true, then based on their shoddy presentation today, if these men are the smartest guys in the room then frankly we need a bigger room.

Perhaps they should read Climate Depot or WattsUpWithThat. And it wouldn't hurt for them to avoid further embarrassment by reading Air Con

Comments

[Thomas Everth]

Just one brief comment on residence time of CO2:

1) the times specified in research papers is normally the "half life time", not the "Maximum residence". It is nonsense to talk about the Maximum residence as even after a long time some of the molecules are still in "residence". So at the end of your bar graphs 1/2 of the CO2 is removed according to the papers you cite.

2) The research talking about short life times of CO2 assume equilibrium conditions, i.e. how long will it take for a bunch of CO2 molecules to be taken out of the atmosphere if the system as such is stable.

3) Currently the CO2 system is unstable. The CO2 concentration is rising fast (fast on a relevant time scale). Under these conditions excess CO2 has a much longer half life time.

See this:

http://geosci.uchicago.edu/~archer/reprints/archer.2005.fate_co2.pdf

[Jan]

Great post Ian.
May I suggest you use a screen-cast capture software in future to record your chats. Since many of these chat software databases may be deleted or altered to reflect whatever the moderator wishes.
I wish there were more un-bias media professionals like yourself. Keep it up!

[Thomas Everth]

I thought I cite the relevant conclusion here from the Archer paper:
and 1kyr = 1000 years (Kilo Years)

http://geosci.uchicago.edu/~archer/reprints/archer.2005.fate_co2.pdf

4. Summary
[19] The carbon cycle of the biosphere will take a long
time to completely neutralize and sequester anthropogenic
CO2. We show a wide range of model forecasts of this
effect. For the best guess cases, which include air/seawater,
CaCO3, and silicate weathering equilibria as affected by an
ocean temperature feedback, we expect that 17–33% of
the fossil fuel carbon will still reside in the atmosphere
1 kyr from now, decreasing to 10–15% at 10 kyr, and 7%
at 100 kyr. The mean lifetime of fossil fuel CO2 is about
30–35 kyr.
[20] A mean atmospheric lifetime of order 104 years is in
start contrast with the ‘‘popular’’ perception of several
hundred year lifetime for atmospheric CO2. In fairness, if
the fate of anthropogenic carbon must be boiled down into a
single number for popular discussion, then 300 years is a
sensible number to choose, because it captures the behavior
of the majority of the carbon. A single exponential decay of
300 years is arguably a better approximation than a single
exponential decay of 30,000 years, if one is forced to
choose. However, the 300 year simplification misses the
immense longevity of the tail on the CO2 lifetime, and
hence its interaction with major ice sheets, ocean methane
clathrate deposits, and future glacial/interglacial cycles. One
could sensibly argue that public discussion should focus on
a time frame within which we live our lives, rather than
concern ourselves with climate impacts tens of thousands of
years in the future. On the other hand, the 10 kyr lifetime of
nuclear waste seems quite relevant to public perception
of nuclear energy decisions today. A better approximation
of the lifetime of fossil fuel CO2 for public discussion might
be ‘‘300 years, plus 25% that lasts forever.’’

[Ian Wishart]

No Thomas, Archer and NZ appear to be wrong. See that study on the biosphere soaking up far more CO2 than expected.

Quite frankly, I no longer trust IPCC or the scientists associated with it...

[John Boy]

Debating this here is helpful but its always seems to descend to arguing stuff on the fringes rather than the bigger picture. Given the serious costs speculated the matter should be debated robustly at a much higher level. That Ian's questions were virtually ignored and his requested representative was excluded tends to support the claim that something is rotten here. We should be arguing the science but it seems we are not and only the disaster model that seemingly requires we make the UN and cronies rich and everyone else poor view is deemed acceptable. I'm grateful Ian is asking what appear to be sensible questions - no one else appears to be.

[robk]

Thomas

Off topic, but you mentioned nuclear waste above. Can you tell me if the 'spent' waste is more or less radioactive than the Uranium that came out of the ground?

I was thinking disposal should be down disused uranium mines (or similar) so there would not be a spreading of radioactivity...

[AcidComments]

Of interest:

Bombshell from Bristol: Is the airborne fraction of anthropogenic CO2 emissions increasing? – study says “no”

Controversial new climate change results

University of Bristol Press release issued 9 November 2009

New data show that the balance between the airborne and the absorbed fraction of carbon dioxide has stayed approximately constant since 1850, despite emissions of carbon dioxide having risen from about 2 billion tons a year in 1850 to 35 billion tons a year now.

This suggests that terrestrial ecosystems and the oceans have a much greater capacity to absorb CO2 than had been previously expected.

The results run contrary to a significant body of recent research which expects that the capacity of terrestrial ecosystems and the oceans to absorb CO2 should start to diminish as CO2 emissions increase, letting greenhouse gas levels skyrocket. Dr Wolfgang Knorr at the University of Bristol found that in fact the trend in the airborne fraction since 1850 has only been 0.7 ± 1.4% per decade, which is essentially zero.

The strength of the new study, published online in Geophysical Research Letters, is that it rests solely on measurements and statistical data, including historical records extracted from Antarctic ice, and does not rely on computations with complex climate models.

http://wattsupwiththat.com/
2009/11/10/bombshell-from-bristol-is-the-airborne-fraction-of-anthropogenic-co2-emissions-increasing-study-says-no/

[Thomas Everth]

Robk: the waste is vastly more radioactive than the Uranium ore from the ground as it contains elements and isotopes with much shorter half life and therefore much higher activity.

[fletch]

The proponents of AGW are going all out in the media now. Tonight they had a story on the TV news about some plane they've got that scoops 'air' from the atmosphere and bottles it so they can study just how much much greenhouse gas is in the atmosphere....I mean...REALLY?! FFS.

[David Wratt via Ian Wishart]

David Wratt has asked me to post this because apparently the blog wouldn't let him (ironic, given the way the plug was pulled on me during the news conference):

On the issue of "residence time" of carbon dioxide:

The link ( http://www.ipcc.ch/ipccreports//tar/wg1/016.htm) you
provide to "The IPCC's own report" in your blog refers to the Third
Assessment Report (2001), where a lifetime of "5 to 200 years" is
quoted, along with the qualification that "No single lifetime can be
defined for CO2 because of the different rates of uptake by different
removal processes".

This issue is discussed further in FAQ 10.3 of the 2007 Fourth
Assessment
(http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-faqs.pdf).
This explains that "while more than half of the CO2 emitted is
currently removed from the atmosphere within a century, some fraction
(about 20%) of emitted CO2 remains in the atmosphere for many
millennia".

A helpful paper on this subject is Archer D. and Brovkin V., 2008: "The
millenial atmospheric lifetime of anthropogenic CO2" Climatic Change Vol
90, pp 283-297.
(http://geosci.uchicago.edu/~archer/reprints/archer.2008.tail_implications.pdf)

Archer and Brovkin discuss the difference between the EXCHANGE of
carbon dioxide between the atmosphere and the ocean (one molecule
dissolving into the ocean, another evaporating from the ocean) and the
NET INVASION of CO2 from the atmosphere into the ocean. They explain
that the 5 year low end of the lifetime range quoted in the 2001 IPCC
report is an "exchange lifetime". However the important timescale for
considering climatic effects of anthropogenic carbon dioxide emissions
is the "invasion lifetime". Likewise I assume that the "residence time"
in the many studies you quote in your blog is that related to the
"exchange lifetime."

For readers of your blog who may be interested I have copied two
relevant paragraphs from page 293 of the Archer and Brivkin paper
below:

"The treatment of the atmospheric lifetime of CO2 was substantially
revised in the most recent IPCC Scientific Assessment Report in 2007
(Solomon et al. 2007). Previous Assessment Reports recognized the long
tail to the CO2 peak in the detailed chapters, but listed an atmospheric
lifetime of 50–200 years in the First Assessment Report in 1995,
revised to 5–200 years in the Second and Third Assessment Reports. The
caveat was given in the Third Assessment Report that “No single
lifetime can be defined for CO2 because of the different rates of uptake
by different removal processes", but the existence of the long tail was
easily missed by most readers.

Confusion of net versus gross carbon fluxes can also lead to a
conclusion of a short CO2 lifetime. The lifetime of an individual CO2
molecule released to the atmosphere may be only a few years, because of
exchange fluxes with the ocean and with the terrestrial biota. Carbon
dissolves in the ocean in one place, and different carbon evaporates to
the atmosphere someplace else. Each year, about 100 Gton C is exchanged
between the atmosphere and the ocean, while the net invasion of CO2 from
the atmosphere into the ocean is only about 2 Gton C per year (Denman et
al. 2007). However, exchange of carbon has no impact on climate, only
net uptake of carbon. The lifetime of climate impacts from CO2 release
will be much longer than the lifetime of the particular CO2 molecules we
release. The 5-year low end estimate of the lifetime of CO2 from the
2001 IPCC must be an exchange lifetime, rather than an invasion
lifetime."

Regards - David Wratt

[Ian Wishart]

David, welcome to the blog - debate is encouraged here. I'm sure by now you've seen the graph above and the studies referred to.

Yes, we are referring to the lifetime of individual CO2 molecules in the atmosphere, because when it comes to radiative absorbtion and forcing a CO2 molecule is only absorbing and re-radiating heat energy for around ten years before it disappears, on average.

I would also suggest you take a long hard look at this study:

Knorr et al. Is the airborne fraction of anthropogenic CO2 emissions increasing? Geophysical Research Letters, 2009; 36 (21): L21710 DOI: 10.1029/2009GL040613

This is the bombshell Uni of Bristol study referred to above that indicates the biosphere has been absorbing far more CO2 than you and the IPCC gave it credit for, making assumptions about the net invasion of CO2 you referred to highly speculative.

I particularly liked this comment from the study authors:

"The strength of the new study, published online in Geophysical Research Letters, is that it rests solely on measurements and statistical data, including historical records extracted from Antarctic ice, and does not rely on computations with complex climate models."

Unlike Archer et al.

My point has consistently been that earth's climate systems are exceedingly more complex than the simplistic IPCC approach allowed for.

The massive overestimation of GHG emissions from deforestation, based on real data instead of models, is another example.

While NZ and others have talked of 'ocean acidification' (more correctly a 'de-alkalinsation' as the oceans are not expected to actually turn acidic, and models are predicated on the long time it takes for oceans to re-plenish their alkalinity, I'd be intrigued at your thoughts on this study:

http://www.rsmas.miami.edu/pressreleases/20090116-flounder.html

Essentially, it indicates ocean fish are probably the prime determinant of ocean alkalinity and can alter the ocean's pH balance much faster than carbonates from plankton.

I suspect if climate models took the extreme overfishing of recent years into account (thus reducing alkaline production in the ocean), we might be getting a more realistic picture of the real cause of the slide towards acidic conditions.

I would also be interested in answers to the rest of the questions above.

Cheers
Ian

[Sally]

The ODT has been running a blog on their website after an opinion piece “We all stand to lose by delaying action on climate” published by Doug Mackie, Hugh Doyle and Christina McGraw, researchers in climate-related disciplines at the University of Otago.
http://www.odt.co.nz/opinion/opinion/79606/we-all-stand-lose-delaying-action-climate

“By using the very simple “not since” claim we illustrated a wider point: People don’t have to understand any chemistry or physics to see that “not since” is totally false. So false in fact that anyone using it has no grasp of the science and is wilfully ignoring the facts.”

Mackie just keeps harping on to various bloggers the not since claim. “I was also wondering if you would care to comment on the apparent dichotomy of your having previously used the "not since" claim and then said it was not a valid argument. Does that mean you were wrong earlier? However do you think you made such an obvious and easily spotted error? Have you made any other such errors?”

In their article they arrogantly said this. “However, our main point is that outright deniers are a sideshow.”

[David Wratt]

Ian

Regarding the "lifetime" issue: What is important for climatic effects is the time for which atmospheric CO2 concentrations remain elevated due to an anthropogenic emission - not the "exchange lifetime" of an individual molecule.

Regards - David Wratt

[iwishart]

David...I'm mobile (albeit at a service station) in the wops...so not near my computer...but what then is the point of talking about a 1000 year residence time?

The other studies (and I've read a few) all use the phrase (residence time) which you are now indicating is being redefined...even since TAR.

You seem to be suggesting this is how long a net surplus amount of CO2 will take to be reabsorbed...but the latest studies appear to show your interpretation is wrong.

If far more CO2 is being reabsorbed by the biosphere...that would appear to contradict one of Archer's previous assertions about the airborne fraction..and undermine the fundamentals of AGW theory.

It might not take 1000 years to be soaked up at all...

I'm still waiting for answers to the other questions arising from yesterday's presentation...by the way.

Mobile email sent via Palm Treo

[AcidComments]

"I'm still waiting for answers to the other questions arising from yesterday's presentation...by the way.'

Ian. W.

Have you seen Todays NZ Herald. Section A. A6?

Rather laughable crystal ball gazing predictions yet again.

I think I've a better chance at predicting the winning Lotto numbers IMO. :-)

[CM]

Yes Acid, you're right, obviously it's better to not even try and work out what might happen. If we ignore what we don't like, that might make it go away or not happen.

[AcidComments]

"Yes Acid, you're right, obviously it's better to not even try and work out what might happen. If we ignore what we don't like, that might make it go away or not happen."

CM.

The Point is.

Many of these socalled predictions are being passed off more like they're an absolute fact.

When infact they're not!

They come from computer model projections which in many cases turn out to be next to useless and unreliable anyway.

Once again. Garbage in . Garbage Out!

[CM]

>>>>One is that the IPCC's next report, AR5 will see an increase in its sea level predictions by 2100 from an upper limit of 60cm to more than 90cm and possibly 1.5 metres.<<<<

Presumably only because they are going to include, rather than exclude, ice dynamics once again. You need to mention that really.

>>>>....not even the IPCC team were prepared....<<<<

You've agreed previously that the very nature of the IPCC makes their overall assessment quite conservative. So what does 'even the' mean?

[Tim Naish]

In answer to your first question regarding the distribution of Elephant Seal remains along the coast of the Ross Sea (reported in PNAS by Hall et al., 2006) as evidence for warmer climate without ice shelf/sheet collapse 1000-3000 years ago I offer the following.

The reported Elephant Seal colonies also occur with Adelie Penguin remains which requires the presence of seasonal pack ice in Ross Sea (for Adelie Penguins), but open water at the coast line (for Elephant seals). Seasonally open water in southern most McMurdo Sound occurs today during the warmest summers, or this may be also be just the influence of katabatic winds. In any case if summer temperatures were slightly higher than present (enough to melt season fast ice) it's a red hearing as loss of sea ice does not cause global sea-level to rise (remember the ice cube in the glass). A number of studies from sediment cores both under the Ross Ice Shelf and in Ross Sea (McKay et al., 2008; Paleogeography, Paleoclimatology and Paleoecology and Domack et al.,1999 Bulletin of the Geological Society of America) show that the northern margin of the Ross Ice Shelf has not moved for 9000 years since it became pinned to Ross Island during retreat following the last ice age. Even the Larsen B Ice Shelf has been stable for the last 9000 years before its demise in 2002 (Domack et al. Nature 2005). Any small rise in local summer temperatures would have been too small to cause major ice shelf or ice sheet retreat. Certainly ice core and tree ring temperature records do not show any significant global temperature increase during this time, that could cause major changes to the polar ice sheets capable of meters of sea-level rise. In fact there is no evidence anywhere on Earth to support +7m of sea-level rise during this time. The last time average global temperatures approached +2°C warmer than present day (the temperatures we will be facing very soon) was 125,000 years ago (the last interglacial warm period), the polar ice sheets did melt and there is widespread evidence of shorelines preserved 4-6m above present day levels. Ice core records indicate that polar temperatures were 2-3°C warmer . Rates of sea-level rise between 1-3m per century are well documented in past climate records ( from corals, uplifted coral terraces and cave stalagmites) when the large northern hemisphere ice sheets melted at the end of the ice ages (e.g. Fairbanks et al., Nature 1989; Rohling et al., Nature Geosciences 2008; Carlson et al., Nature Geosciences 2008; Hunebuth et al., Science, 2000).

The last time Earth had an atmosphere with 400ppm carbon dioxide was about 4 million years ago. Global average surface temperature was +3° C above present and the Ross Sea surface temperature was +4-5°C above present. There is geological (Naish et al., Nature 2009) and model (Pollard and DeConto, Nature 2009) evidence to show that the Antarctic ice sheet (mainly West Antarctic Ice Sheet) melted rapidly to raise sea-level +7m globally. The vulnerable portion of the West Antarctic Ice Sheet (the bit that sits below present day sea-level) is shown in models to melt in 300 years raising sea-level by 3m above present (1m/century).

[CM]

Gotta say, Ian, the willingness of both David and Tim to actively come here to participate does undermine your conspiracy theory about them not wanting debate.