1) If we loose 50% of the capacity to reduce CO2 to oxygen won't the equilibrium concentration of oxygen fall considerably?
Put simply, why? There is vastly more oxygen than carbon dioxide in the atmosphere. Losing the capacity to convert carbon dioxide back to oxygen - yes - I think one would expect a gradual (and proportionately rapid) build up of carbon dioxide - but the reduction in oxygen would be proportionately far smaller and slower.
Try doing the maths sometime - and work out just how much carbon must be oxidised to deplete atmospheric oxygen substantially? The figure is ... impressive. I think it's safe to take a ratio of approximately 3 (but it varies by fuel source) for the rate at which oxygen is depleted for combusting fossil fuels (or any other comparable natural processes). It's around 3 for oil and gas because 2 oxygens are consumed by each carbon atom - and some oxygen also tends to be consumed by combusting hydrogen into water. I believe coal is nearer to 2. Bearing in mind oxygen comes in two atom molecules (O
2) this link explores the maths a bit:
http://blogcritics.org/atmospheric-oxygen-levels-fall-as-carbon/http://scrippso2.ucsd.edu/faqDespite the reference suggesting 19.5% atmospheric oxygen would be a concern, I don't think the lower tolerance range for human survival is clearly defined - especially not if a change is occurring over the timescales implied by the scale of combustion required to significantly shift atmospheric oxygen. Consider that people live at high altitudes and indeed have even climbed mount Everest without an oxygen supply - surviving on just a fraction of the oxygen available at sea level.
In short, while fossil fuels do consume oxygen and killing large amounts of photosynthesisers would no doubt reduce the replenishment of oxygen in the atmosphere it requires staggeringly immense events to appreciably shift the balance of oxygen in the atmosphere - and the human tolerance range seems reasonably generous.
Over geological time the oxygen content of the atmosphere has varied significantly.
http://en.wikipedia.org/wiki/Geological_history_of_oxygenNote that it has at one time been far higher than present (too high and fire tends to break out far more often).
2) The tree topic is controversial e.g. Plant a tree and save the Earth? https://www.llnl.gov/news/newsreleases/2006/NR-06-12-02.html
Trees are somewhat controversional. I am discounting any ability they might have to sequester carbon dioxide - and emphasising their benefits to the local environment in which they grow. Preventing erosion and moderating temperatures and weather (setting aside their impact on the global heat budget) are very valuable attributes if you happen to be living nearby.
It's a pity that McPherson's arguments have the problems you point out because his performance is superb. We don't see climate and economy linked often enough.
His presentation style is pretty direct and effective - it's unfortunate that very few people:
a) try to join up all the dots into presentations aimed at the average person or politician
b) are willing to engage with the more pessimistic end of the spectrum, which may well turn out to be the more realistic end
Choices are hence very limited, notwithstanding that it really isn't that hard to reference properly and find scientific evidence to support a pretty gloomy long term outlook.
Where have they said that the climate models they use are missing important feedbacks and lag the real world - considerably in the case of Arctic sea ice? If they have actually said this it was too quiet for me to hear.
I am myself very skeptical of the IPCC - and somewhat negative about how I perceive them. I think many valid criticisms are levelled at them - but I think the majority of fault does not lie with them. Consider a few things:
Despite the very large amount of material they have produced (and how many of us have even read it all - I haven't), look at how few errors have been found and jumped on by the denying forces?
I am going to argue that if you read closely what the IPCC write, they are actually presenting a very open ended and ambiguous answer. Horrific amounts of detail is discarded in the communication and translation of what they say when it is presented to the public and to policy makers.
They come in for especial criticism for relying upon incomplete and inaccurate models, so I would like to highlight a few select quotes from this link from their literature:
http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch10s10-5.html#10-5-1The quotes I find especially apt are:
Uncertainty in predictions of anthropogenic climate change arises at all stages of the modelling process
The specification of future emissions of greenhouse gases, aerosols and their precursors is uncertain
At each step, uncertainty in the true signal of climate change is introduced both by errors in the representation of Earth system processes in models (e.g., Palmer et al., 2005) and by internal climate variability (e.g., Selten et al., 2004)
However, some processes may be missing from the set of available models, and alternative parametrizations of other processes may share common systematic biases.
And finally - the most damning admission of all (I appreciate I quoted heavily from the first paragraph, but I would argue each of those statements stands alone in admitting uncertainty):
For fundamental physical reasons as well as data limitations, values substantially higher than 4.5°C still cannot be excluded, but agreement with observations and proxy data is generally worse for those high values than for values in the 2°C to 4.5°C range.
Let's pause a moment. The IPCC is saying they
cannot exclude values substantially higher than 4.5°C for values of climate equilibrium sensitivity.
So what is the media reporting? What is the message policy makers are concentrating on? Are they focusing on the fact that the IPCC still cannot rule out substantially worse outcomes than the ones predicted by the models (declared to be uncertain for a number of reasons above)? Or are they just saying "the IPCC says 2-4.5C"?
Since the models drive almost every forecast they make - this applies to almost everything they publish. While I have no read that much of the stuff the IPCC produce, it is my general feeling that they are very careful and precise in attempting to enumerate the limitations of their approach and the uncertainties and caveats.
They also tend to be careful to avoid stating solid conclusions unless extremely sure. So for example, on the chances of abrupt AMOC shutdown this century:
http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch10s10-es-15-atlantic-ocean.htmlIt is very unlikely that the MOC will undergo a large abrupt transition during the course of the 21st century.
If memory serves,
very unlikely means it is thought to be < 10%. Well, there are quite a few things that the IPCC thinks are
very unlikely - so I suggest one should consider, based purely on statistics - that at least some of them
are going to happen, despite being thought very unlikely.
Yet - we regularly see people arguing against them as points of concern on the basis that they aren't expected to happen - and not admitting that statistically at least some of these very unlikely things should be expected to happen. I've even seen that on this forum, though not as much as most other places.
I think they meant "Don't listen to Jennifer Francis!" (because the policy consequences are too great?)
Of one thing I am quite sure - nobody really wants to believe abrupt climate change (and all that implies) is starting here and now. It's more comfortable to perceive it as a future problem, or one that will affect only others.
I often speak to scientists who do not think climate change is as serious as many here. I think often they are highly specialised experts in one narrow field of study and don't step back to look at the bigger picture in detail.
Scientists and reporting groups are also human beings. It takes time for information to propagate, for ideas to be accepted, and so on. They may represent the most heavily weighted quality of information we have - but they aren't a definitive and final statement.
