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Don Keiller on plants and carbon dioxide

There has been some discussion in the comments about Don Keiller's undergraduate lecture about plants and carbon dioxide. Don has kindly sent over the slides, which can be seen here.

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    - Bishop Hill blog - Don Keiller on plants and carbon dioxide

Reader Comments (77)


Mar 19, 2013 at 12:44 PM | Unregistered CommenterAdam Gallon

Interesting slides. One thing that jumps out at me from slide 8 (looking at major events in plant evolution) is that the planet temperature seems to be almost bistable - ie. switching quite quickly between two stable states. I know the time scale is non-linear and highly compressed, but all the same, it is striking.

Mar 19, 2013 at 1:33 PM | Unregistered CommenterBitBucket

Bitbucket, you are correct the planet appears to have 2 stable states. About 22C (Warmhouse) and 14C (Icehouse). Over the Earths entire history warmhouse conditions have predominated.
Also you will note that there is no obvious corelation with CO2. In fact Rothman (Atmospheric carbon dioxide levels for the last 500 million years. Proceedings of the National Academy of Sciences 99 (7): 4167-4171, 2002), from which this figure is derived states "The resulting CO2 signal exhibits no systematic correspondence with the geologic record of climatic variations at tectonic time scales".

Mar 19, 2013 at 1:41 PM | Unregistered CommenterDon Keiller

Many thanks Don, that's excellent.

Did you know that the Dutch are now required by law to reduce the level of CO2 enhancement in their glasshouses? No science justification given.

Mar 19, 2013 at 1:48 PM | Registered Commenterflaxdoctor

Ah but, Don, our modern man-made CO2 is different. Our CO2 drives the system like it has never been known to do before. So it must be different. QED.

Mar 19, 2013 at 1:53 PM | Unregistered CommenterJohn Shade

Those blue/red icehouse/warm-house bands seem to correlate poorly with the temperature curve. How are they defined?

Mar 19, 2013 at 2:22 PM | Unregistered CommenterBitBucket

Jolly good! More ethanol to fight the cause of, er, more ethanol :-)

Mar 19, 2013 at 2:31 PM | Unregistered Commenterssat

I do hope the HGCA (Home Grown Cereals Authority) see this. They are the UK body set up (as the name suggests) to boost home production of crops. Unfortunately (especially after this evidence) they are fully commited to reducing CO2.


Mar 19, 2013 at 2:38 PM | Unregistered CommenterCharlie Flindt

Many thanks for these Don, it's good to see that there are still those such as yourself who believe in putting across the facts rather than the hype that tends to be indulged in by others in our educational establishments

"A leading climate scientist has presented new research findings on the increasing potential for a 4 degrees Celsius rise in global temperatures if the current high emissions of greenhouse gases continue.

The conference at Oxford University is the first to consider the global consequences of climate change beyond 2 degrees Celsius, and is jointly sponsored by University’s Environmental Change Institute, the Tyndall Centre for Climate Change Research and the Met Office Hadley Centre.

Speaking at the international conference called ‘4 degrees and beyond’ at Oxford University, Dr Richard Betts, Head of Climate Impacts at the Met Office Hadley Centre, described the possibility of a 4 degree warming happening ‘before the end of the century’. He added that a scenario of very intensive fossil fuel burning could bring this forward by 20 years.

Topics from over 50 other conference research papers will include: food and water security, vulnerable populations, human health, migration, wild fires, sea level rise, wildlife conservation, and ecosystem services. Regional case studies will include Amazonia, Australia, Bangladesh, Brazil, Ethiopia, Finland, Mauritius, Siberia, Vietnam, and the monsoon region.
Rates of warming will be faster than most people expect Dr Mark New
Conference convenor Dr Mark New, from the Oxford University School of Geography and the Environment, and the Tyndall Centre, said: ‘Since the late 1990s, greenhouse gas emissions have increased at close to the most extreme IPCC scenarios, meaning that rates of warming will be faster than most people expect. The conference will review the best science on the consequences of these large climate changes and what we can do about it.’

In today’s presentation Dr Betts warned that 4 degrees of warming could have extreme regional implications along with major changes in rainfall. He said: ‘If greenhouse emissions are not cut soon, then we could see major climate changes within our own lifetimes.’

Other speakers are Professor John Schellnhuber, Director of the Potsdam Institute for Climate Impact Research, on 4 degrees warming and the potential for tipping points; Professor Yadvinder Mahli, from Oxford University’s Environmental Change Institute, on the impact on tropical forests; Dr Philip Thornton, International Livestock Research Institute, Nairobi, on sub-Saharan agriculture; Dr Pier Vellinga, from Wageningen University, on sea-level rise; and Professor Kevin Anderson, Director of the Tyndall Centre for Climate Change Research, on global emission pathways."

Mar 19, 2013 at 2:44 PM | Unregistered CommenterMarion

Don - excellent presentation - many thanks for making it available

Mar 19, 2013 at 3:06 PM | Unregistered CommenterJeremy Poynton

Just curious: Who first coined the phrase "hide the decline"? Was it first mentioned in that Phil Jone's email referencing "Mike's Nature trick"? Thanks,

p.s. I propose we have an international Hide The Decline day, on the date the phrase first entered the public consciousness. On this day, everybody gets to "hide a decline" of theirs in a printed-out email letter, which is then tossed en masse into a huge pit before being filled with concrete.

Mar 19, 2013 at 3:48 PM | Unregistered Commenterpeebo

Interesting slides. One thing that jumps out at me from slide 8 (looking at major events in plant evolution) is that the planet temperature seems to be almost bistable - ie. switching quite quickly between two stable states. I know the time scale is non-linear and highly compressed, but all the same, it is striking.
Mar 19, 2013 at 1:33 PM BitBucket

I've played around simulating chaotic systems in the past and found that they sometimes have the property of staying in one state* for an apparently arbitrary period and then abruptly switching to a second state (for no obvious reason), for an apparently arbitrary period, then back to the first state and so on.

[At school, another kid interested in electronics showed me how he could get a germanium transistor to "oscillate at all frequencies" as he put it. I think this was probably the same general effect.]

* Maybe "condition" would be a better term, to avoid confusion with the state variables of a system.

Mar 19, 2013 at 3:55 PM | Registered CommenterMartin A

Mar 19, 2013 at 2:44 PM Marion

That was 2009. You may have noticed that the Met Office has detectably toned down its propaganda output recently. It's still propaganda, but toned down relative to just a few years back.

Had the global average temperature exceeded the Met Office's predictions, can you imagine what their output would have been like today?

Mar 19, 2013 at 4:03 PM | Registered CommenterMartin A

Martin, bitbucket, yes. Another thing that does this is the Earth's magnetic field. It wobbles around for a while, with the magnetic North pole fairly near the real North Pole, then flips, so the magnetic N pole is near the geographical S pole. It does this all by itself, every few hundred thousand years, without any man-made forcing!

Mar 19, 2013 at 4:48 PM | Registered CommenterPaul Matthews

@Martin A
I think a Schmitt Trigger is nearer the mark for the process in question.

Mar 19, 2013 at 5:22 PM | Unregistered CommenterSandyS

Charlie Flindt,

Good timing - could you point this out to them in your FW column? They read it and act on it. They'll get the slides too.

Mar 19, 2013 at 6:19 PM | Registered Commenterflaxdoctor

The Warmist will hit back with More CO2 ,More Plants ,More Weeds,Day of the Triffids.

We hit back with More People, More CO2 ,More Plants, More Crops ,No Starvation. Man Versus Food

Mar 19, 2013 at 6:24 PM | Unregistered Commenterjamspid

Mar 19, 2013 at 4:03 PM | Martin A

Yes indeed Martin A that was 2009 but I don't think it does any harm to remind the Met Office just what they were hyping in the run-up to Copenhagen.

In particular Richard Betts conclusions -

Current CO2 emissions are near (but not above) upper end of IPCC

4°C global warming (relative to pre-industrial) is possible by the
2090s, especially under high emissions scenario

Many areas could warm by 10°C or more

The Arctic could warm by 15°C or more

Annual precipitation could decrease by 20% or more in many areas

Carbon cycle feedbacks expected to accelerate warming

With high emissions, best guess is 4°C in 2070s

Plausible worst case: 4°C by 2060

Or the quote given in the Oxford University article -

"In today’s presentation Dr Betts warned that 4 degrees of warming could have extreme regional implications along with major changes in rainfall. He said: ‘If greenhouse emissions are not cut soon, then we could see major climate changes within our own lifetimes.’"

- policy advice???

Mar 19, 2013 at 6:35 PM | Unregistered CommenterMarion

"In today’s presentation Dr Betts warned that 4 degrees of warming could have extreme regional implications along with major changes in rainfall. He said: ‘If greenhouse emissions are not cut soon, then we could see major climate changes within our own lifetimes.’"

Link -

Mar 19, 2013 at 6:47 PM | Unregistered CommenterMarion

@Martin A
I think a Schmitt Trigger is nearer the mark for the process in question.
Mar 19, 2013 at 5:22 PM SandyS

Yes, SN7413 etc - I remember them well.

A bit of positive feedback is very likely involved in a system that suddenly switches states

Mar 19, 2013 at 6:48 PM | Registered CommenterMartin A

- policy advice???
Mar 19, 2013 at 6:35 PM Marion


Instead of providing balanced and carefully considered advice, one of the traditional functions of the scientific Civil Service, it became a generator of propaganda. Its success in this activity is marked by the fact that it lead a scientifically illiterate parliament to pass the climate change act.

Mar 19, 2013 at 6:57 PM | Registered CommenterMartin A

SayNoToFearmongers and Charlie Flindt,

I can't see the HGCA taking any notice.

It isn't a practical measure they could propose, as with soil analysis, advice on strains, or if cereals were grown in greenhouses.

Undue recognition of the fact would mean they were breaking with the orthodoxy, which would not be a career enhancing stance.

If cornered they might issue a statement along the lines of, "It is well recognised that there is an increase in productivity due to enhanced CO2, however, it is also well recognised from the best scientific advice that a general increase in atmospheric CO2 levels has a deleterious impact on climate which greatly outweighs any possible benefits."

They are not about to break ranks over something they can't control and is of no direct benefit to them. They might tone it down if the rest of the establishment is toning it down.

Mar 19, 2013 at 7:10 PM | Unregistered Commentercosmic


That's not really the point - Charlie and his fellow farmers pay for the HGCA's activities through a statutory levy on sales of grain and oilseeds. That's the only funding HGCA gets, and its job is to agree a research and marketing programme with its levy payers to spend this money in developing the industry. In my view the focus should on genuinely pressing research issues, such as overcoming long-term yield plateauing in our key crops when we may have more people to feed from the same land area. There are far too many people across the world squandering money on last century's fantasy demons. We need to be smarter than them.

Mar 19, 2013 at 7:26 PM | Registered Commenterflaxdoctor

@Marion- I'm very disappointed with Dr Richard Betts. He has tried to come over as a voice of reason, yet this lecture ( has all the hallmarks of Alarmist hype.
Look at what he is saying;
"Current CO2 emissions are near (but not above) upper end of IPCC
4°C global warming (relative to pre-industrial) is possible by the
2090s, especially under high emissions scenario
Many areas could warm by 10°C or more
The Arctic could warm by 15°C or more"

Yet what is actually happening?
Despite high CO2 emissions, Global temperature has stagnated for 15 years. Even his own organisation has been forced to revise their forecasts down.

You can't be all things to all men Richard.
Who are you?

Mar 19, 2013 at 9:01 PM | Unregistered CommenterDon Keiller

What puzzles me about slide 8 (the one with the 4.6bn year temperature history) is that sceptics as a rule wouldn't give house room to a 150 instrumental record and would only accept a proxy reconstruction of the last few thousand years if it had their favourite bumps and curves - and only then to hang next to a picture of Michael Mann to throw darts at. Yet a reconstruction spanning 4.6 billion years gets to hang over the fireplace next to a picture of the favourite uncle. Very odd...

Mar 19, 2013 at 9:14 PM | Unregistered CommenterBitBucket

Marion, Martin A

I suspect Dr Betts might no longer even attempt to defend an ECS of 4.8°C per doubling of atmospheric carbon dioxide (implied [happy to show my workings] by the [unduly alarmist] presentation in 2009 i.e. 4°C [from 1855] by 2100 [or earlier!]!).
I would look forward to his contribution. But then, he does find His Grace's blog a little too robust (!!!).
Millikan Effect, anyone?

Mar 19, 2013 at 9:29 PM | Unregistered CommenterEvil Denier

Are you saying that slide 8 is wrong? Or perhaps there are instrumental records spliced on for the last couple of hundred years?

Mar 19, 2013 at 9:40 PM | Unregistered CommenterSandyS

Wrong? How do I know? But it goes back almost 4600 million years. Sceptics dispute even last century's thermometer records and any record based on proxies going back to relatively recent historical (let alone geological) times. Yet the graph presents a temperature, CO2 and flooding (!) profile going back over 500 million years. Do you trust it to give any more than a very vague idea of possible past conditions?

Mar 19, 2013 at 10:59 PM | Unregistered CommenterBitBucket

As usual BB you miss the point in an attempt to nitpick.
The point is that major plant evolutionary events;
Sea- land, Bryophytes to Pteridiophytes, Pteridiophytes to Gymnosperms etc. all happened when it was warm and CO2 levels high (not that I am saying one drives another or vice-versa).
Plants LIKE these conditions.
At current levels of CO2 many plants are working sub-optimally.
During the last Ice-age there was a real danger of photosynthetic shut-down and that would have been a real disaster, unlike the spoof scare of AGW.

Mar 19, 2013 at 11:14 PM | Unregistered CommenterDon Keiller

" Bryophytes to Pteridiophytes, Pteridiophytes to Gymnosperms" - call from Bitbucket to!

Mar 19, 2013 at 11:44 PM | Unregistered Commenterdiogenes

I like the way Slide 3 stops at 1950.

Mar 20, 2013 at 12:04 AM | Unregistered CommenterEntropic man

Entropic Man,

If you could read without letting your biases blind you, you would see that the slide is a graph of central Greenland temperatures over the last 50,000 years and based on the data from Alley 2000, which in turn was based on the gisp2 ice core analysis. The graph uses the term (x) years before present, the standard for such long term graphs. 1950 is the standard year used in all such graphs to represent “present”. Now, the graph is necessarily low resolution. You could, if you were so inclined, stick on the last 60 years of high resolution instrumental readings, but it wouldn’t give you a valid graph. Of course, according to NASA-GISS, temperatures in Greenland were higher in the thirties and forties and cooling by 1950. Todays’ temperatures there haven’t yet matched those of the thirties and forties, so I’m not sure what it is you're insinuating Don is trying to hide.

Mar 20, 2013 at 1:49 AM | Registered CommenterLaurie Childs

Missing the point? I don't think so. Take a look at what appears to be your source. Scotese has pretty much your temperature curve. Now look in his links for each period, starting with the Cambrian. Look what he says: "The climate of the Cambrian is not well known. It was probably not very hot, nor very cold. There is no evidence of ice at the poles." Now look at his temperature curve - not very hot and not very cold has translated into or his steaming Hot House. I haven't checked all of the rest but just looking at the methods page anyone with an ounce of scepticism in them would see this whole temperature curve for completely speculative.

But not you. You jump on these speculative curves (the CO₂ curve is probably equally speculative) to draw some spurious conclusion that plant evolution depends in some way on high temperature/CO₂ levels, when it could equally be that low CO₂ levels could trigger evolutionary jumps (there you are, I can speculate too). For example C4 photosynthesis most likely didn't evolve because there was abundant CO₂ but because levels were low.

Mar 20, 2013 at 1:59 AM | Unregistered CommenterBitBucket


I think you’ll find very few sceptics who don’t accept last centurys’ (and the century before thats‘) thermometer records. I think you’ll find it’s the subsequent continual adjustments to those records coupled with the attempt to average them into some kind of meaningless global temperature that sceptics, rightly or wrongly, object to. Same with proxies. When they are used to give us a general idea of the prevailing conditions in whatever timeframe, then fine. I don’t see a problem. Provided, of course, that they are not used as gospel and that it’s borne in mind that the interpretation of the proxies may well be wrong and not telling us what we think they are telling us. It’s when they are statistically (often badly) tortured to give, for instance, a temperature to within 2 decimal places, or a CO2 reading to within a ppm, that’s when sceptics kick up a fuss. You’ve been around quite a while now, yet you still seem to have no comprehension of the sceptics viewpoints at all. Very odd … ;)

PS Just as I was about to post this, I noticed your comment that I missed earlier (Mar 20, 2013 at 1:59 AM). For once, I agree with what you say. Of course it’s speculative. It has to be. However, I take it simply as an indication that at this particular time, give or take a million years or so, it was warm. Then at this other time, give or take a million years or so, it was cold. Same with the CO2 levels and the flooding events. If it's not entirely accurate, it doesn't really matter. Nobody is trying to define absolutes on which to base policy. I’m glad though to see your scepticism awakened. I trust we’ll see it in action on all proxy based papers from now on. For instance, I’ve no doubt the Marcott paper will be discussed here again at some point. I look forward to reading your views.

Mar 20, 2013 at 3:08 AM | Registered CommenterLaurie Childs

Geological perspective... don't leave home without it.

Mar 20, 2013 at 5:23 AM | Unregistered CommenterMickey Reno

@Laurie Childs Mar 20, 2013 at 5:23 AM
I agree with you.
Also of course proxies are only proxies whether a million years ago or 1000 years ago, it only gives an estimate roughly in a time frame. Splicing proxy to temperature records is a pointless exercise. Hopefully more people in the MSM might begin to realise that splicing two different things together only works well for roses and fruit trees.

Mar 20, 2013 at 8:03 AM | Unregistered CommenterSandyS

Don Keiller

Who am I? I'm a scientist who is interested in both roles of CO2 in the climate system:

1. as an influence on plant photosynthesis and water use efficiency
2. as a greenhouse gas

Our modelling of CO2 effects on plants in the Met Office Hadley Centre climate models is very much along the lines you describe in your slides, see this paper.

So I'm glad we agree on something (and an important thing too!)

Mar 20, 2013 at 8:14 AM | Registered CommenterRichard Betts

Don't avoid the question, Richard.
Do you stand by your comments of 4C-15C temperature increases by 2090?

I skimmed through your paper and I am pleased you agree that increased CO2 will result in increased primary production and water use efficiency- Why not scream this from the rooftops, rather than the Alarmist rubbish at Oxford?

But no the conclusion is "enhanced warming" and
"The resulting change in surface energy partitioning produces an appreciable magnification of the
warming over tropical rainforests."

So how has your MOSES model fared over the last 13-14 years in terms of "an appreciable magnification of the warming over tropical rainforests."?

Not very well :-)

Mar 20, 2013 at 11:02 AM | Unregistered CommenterDon Keiller

There are two kinds of CO2: the physical and the political.

The physical kind plays a very modest role in determining the twists and turns of climate as has been documented over geological as well as over instrumented timescales. It is very variable in concentration in the air, and is disproportionately released at ground level by tropical and sub-tropical vegetation with marked annual cycles, and from the world’s oceans on far longer timescales. This CO2 is good for plants, most of which were evolved when CO2 levels were far higher. It may even one day produce a gentle warming large enough to be reliably detected amidst the variation due to many other causes. Given our presumed proximity to the end of the Holocene, this is even more good news since our species and most others thrive in warmer conditions.

The political kind plays an extremely important role in determining future climates, and indeed some say current ones. That it has never been known to do this before is the key clue to the existence of this new substance, which is primarily released at ground level by industries and some other activities linked to human progress in the most developed or developing regions of the northern hemisphere, mostly outside of the tropics. It does not appear in computer models of the climate – that remains an elusive goal. Instead it is represented by a drop in heat energy released at the top of the model atmosphere, and this can be both instantaneous and uniform in space. This CO2 is always bad, and the very thought of it can produce tears in grown men, nightmares in children, and hideous videos by Labour government and associated zealots.

Don's lecture has given some prominence to physical CO2, whereas Richard's work allows him to dabble with both - although his job is crucially dependent on the political type, as are so many positions created in the wealthier countries in the past few decades. We have local authorities appointing CO2 reduction officers for example, and no end of consultancies offering similar services. Efforts at creating a new financial market around this political gas have generally faltered, although there seems little doubt some have made fortunes from the attempts. Charitable organisations once pre-occupied with wildlife or pollution or hunger or poverty have found it far more lucrative to concentrate on this gas, and quite a few would-be revolutionaries, knocked back by the ignominious failure of the Soviet Empire and other such left-wing disasters have found a new lease of life through touting and analysing the awfulness of it. Others are busy taking a longer-term view to keep these opportunities going by encouraging children to be afraid of this gas and thereby scornful of the progress which has produced it - so much so that the hope is they will put pressure on their parents to take political action to help destroy that progress. There may well be decades of prosperity and job security left for those doing all these things, but theirs is a goal-inhibited drive since reducing this political gas to what they deem acceptable levels will require their followers to find new ways to make their fortune and interfere in the lives of others generally to their detriment.

Mar 20, 2013 at 11:50 AM | Unregistered CommenterJohn Shade

Very apposite points, John.

Mar 20, 2013 at 1:18 PM | Unregistered CommenterDon Keiller

Re: Mar 20, 2013 at 11:50 AM | John Shade

Nice post, John.

I'd further define these as being representative of the two types of scientific research , the former being the real science whereas the latter, the political kind is the policy-led 'science'.

Unfortunately we have far too much of the latter in the climate change arena, unsurprisingly, as this is where all the funding has been made available!!

Mar 20, 2013 at 2:08 PM | Unregistered CommenterMarion

Laurie Clilds

I'm indulging in a bit of irony. Only a few days ago I was reading complaints on Bishop Hill about a Marcott et al graph stopping in mid-century. :-)

Mar 20, 2013 at 2:47 PM | Unregistered CommenterEntropic man

Entropic Man - you should educate yourself on just why Marcott et al stop mid Century
checkout the following:

When you have finished your journey of enlightenment, Grasshopper, come back and tell us of your findings.

Mar 20, 2013 at 3:13 PM | Unregistered CommenterDon Keiller

Laurie, the trouble is that these curves appear to be no more than fantasy or guesswork - see the link I posted before. Your 'give or take a million years or so' would make the guesses on the chart for 500 million years ago accurate to 0.2%. Are you serious? Tell me a proxy (ice core, tree ring mud core etc) that you would trust to be accurate to that degree.

The problem I have is that DK takes this guesswork, draws some arrows on the chart and states that "...major plant evolutionary events ... all happened when it was warm and CO2 levels high" - without qualification (ie without pointing out that the chart is fantasy). He has no proof of this - it is just an assertion. If this is what is served up to his undergrads I would recommend them to ask for their £9000 back and to go somewhere else.

Sandy, why do you object to splicing? If you have a proxy record and a thermometer record that overlap significantly in time and they don't correspond, then one is wrong, probably the proxy. If you don't splice them together you don't know. This seems self-evident, so maybe I missed your meaning...

Mar 20, 2013 at 4:19 PM | Unregistered CommenterBitBucket

Adding extra CO2 to to the air when growing C3 plants in greenhouses does boost yields.

The practical limit is around1500ppm, at which reduced transpiration due to closing stomata cancels out the extra photosynthesis. 1500ppm is also the point at which the more vulnerable workers start to show breathing difficulties.

Mar 20, 2013 at 7:05 PM | Unregistered CommenterEntropic man

Bit bucket

In fairness to Keiller, his first slide excellently demonstrates the reliability of ice core CO2 data. The fit between the Keeling curve and the Law Dome data is very good.

Don Keiller

Your insult does not answer the question. In Slide 3, why did YOUR graph stop at 1950?

Mar 20, 2013 at 7:13 PM | Unregistered CommenterEntropic man

Don, Entropic man is unable to understand McIntyre's posts. He understands dates on the horizontal axes of graphs though, they do that at GCSE.

Mar 20, 2013 at 7:56 PM | Unregistered CommenterSJF

Entropic Man. Quite simple- because snow does not compact fully to ice for about 50 years, therefore data is unreliable.

Unlike your hero, Mann, Alley did not feel the need to splice instrumental data onto proxy data.

Also look at the scale on the temperature axis. Now splice your 0.7C on the post 1950 section.
Completely negligible- and this is what you and other Alarmists are getting so worked up about.

Mar 20, 2013 at 8:22 PM | Unregistered CommenterDon Keiller

Entropic Man- you say "The practical limit is around 1500ppm, at which reduced transpiration due to closing stomata cancels out the extra photosynthesis.".
Look again at slide 13. Stressed plants (that is the vast majority growing outside in the real World, rather than hydroponics) are still responding positively to a CO2 enhancement of 1350ppm.
Add that to ambient and you get 1700ppm.
Transpiration shutdown? Get real- what do you think plants did when atmospheric CO2 was over 200ppm? Grow like crazy that's what.
Finally where did you get your 1500 ppm rubbish causing "breathing difficulties"?
CO2 concentrations up to 1% (10,000 ppm) can make some people feel drowsy.

Go away, as I suggested earlier and actually learn some facts.

Mar 20, 2013 at 8:34 PM | Unregistered CommenterDon Keiller

Bitbucket- the objection I have to splicing instrumental data to proxy is simple- even you might understand if you take the trouble to read with an open mind.
Proxy data is averaged and high frequency variation (less than 10 years, often less than 100 years) is subsumed. Instrumental data is yearly and captures high frequency variation. You take the average of the 20th Century temperatures and paste that on the end of your proxy curve and it is not very impressive.

Mar 20, 2013 at 8:44 PM | Unregistered CommenterDon Keiller

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