So my point is, when SM casually says:

"It was pointed out to me that about 500m years ago CO2 levels were about 2000ppm (5x that of today) and life flourished and temperatures were not that different from today."

He's representing planetary "life" as something that "flourished", but fails to point out that "life" back then was nothing like we think of it ranged across the planet.

It was a throw-away comparison - a one-liner to set up the erroneous conclusion that "life" back then was somehow comparable with "life" now.

That CO2 levels were elevated and "life flourished" is misleading in the context of us discussing the threat to life and civilisation as we know it in the modern era.

http://en.wikipedia.org/wiki/Late_Devonian_extinction

What's interesting during these epochs is marine extinctions...anoxia, etc

Humans have been busy outgassing CO2 for some time now, but it's "sudden" on an historic timeline.

Hi Poirot :)

When SM writes,

"He's representing planetary "life" as something that "flourished", but fails to point out that "life" back then was nothing like we think of it ranged across the planet. .... "

it's a safe bet that he is not assuming, or leading anybody to think, that life then was just like it is now, plus the odd dinosaur. Real life is not like Jurassic Park. Dinosaurs had not been invented back 500m years ago, nor plants or humans, life existed only in the seas - but perhaps he was intimating that life in the seas was teeming ? The late Devonian Extinctions did not occur for at least another 100m years.

As our friendly Wikipedia author writes,

"The extinction seems to have only affected marine life. Hard-hit groups include brachiopods, trilobites, and reef-building organisms; the latter almost completely disappeared, with coral reefs only returning upon the evolution of modern corals during the Mesozoic.

"The causes of these extinctions are unclear. Leading theories include changes in sea level and ocean anoxia, possibly triggered by global cooling or oceanic volcanism. The impact of a comet or another extraterrestrial body has also been suggested. Some statistical analysis suggests that the decrease in diversity was caused more by a decrease in speciation than by an increase in extinctions. This might have been caused by invasions of cosmopolitan species, rather than any single event.

"Surprisingly, jawed vertebrates seem to have been unaffected by the loss of reefs or other aspects of the Kellwasser event, while agnathans were in decline long before the end of the Frasnian."

Yeah, bugger the agnathans, what did they ever do for us ?

Cheers :)

Joe

From your referenced link, Joe,
http://en.wikipedia.org/wiki/Evolutionary_history_of_plants#Colonization_of_land , it also says:

Land plants evolved from chlorophyte algae, perhaps as early as 510 million years ago;[4] some molecular estimates place their origin even earlier, as much as 630 million years ago....... the land plants evolved from a branched, filamentous alga dwelling in shallow fresh water,[6] perhaps at the edge of seasonally desiccating pools.[4] ..... Co-operative interactions with fungi may have helped early plants adapt to the stresses of the terrestrial realm.[7]
Plants were not the first photosynthesisers on land; weathering rates suggest that organisms were already living on the land 1,200 million years ago,[4] and microbial fossils have been found in freshwater lake deposits from 1,000 million years ago......"

A bit confusing and overlapping, as may well be the data Poirot has drawn from.

Personally, I remain convinced that a 3-4 degree rise would be catastrophic to mankind in the sense that we will not be adapt to it as a whole society, but only in pockets. Rather than hoping my DNA falls into one of those pockets, I'd like to do something more to avert the problem than is planned.

Luciferade,

You suggest:

"Personally, I remain convinced that a 3-4 degree rise would be catastrophic to mankind in the sense that we will not be adapt to it as a whole society, but only in pockets. Rather than hoping my DNA falls into one of those pockets, I'd like to do something more to avert the problem than is planned."

Well, yes, that's what many of us have been saying all along: that instead of sitting, weeping and wailing about doom what can we do about it ?

Of course, if the 'pause' gets much longer, and it becomes clear that there might be other factors in global swarming and cooling besides CO2, and yet CO2 production keeps rising, we may have that much longer to work out what to do, no rush.

Joe

Joe, the jury is in. AGW continues and we must not burn all our fossil fuel reserves.

Growing trees may buy a little time, at best, requiring not only our best land diverted from current purposes, but massively more forestation in new areas than existed before agrarian man, given our population is now ten thousand times more.

We have to cut to the chase and not visit every dead-end, so I'll not comment further on reforestation. Clinging naively to it as our salvation is dumb and does not make one green, only feeling green.

Hi Luciferade,

I'm certainly not relying only on re-forestation, simply that it could play a major role, alongside renewable energy production, perhaps taking our cue on nuclear power from France or Sweden rather than the Ukraine or Japan, using power more efficiently, switching from coal to natural gas (no, not coal-seam gas: Canning Basin gas, for example), etc., etc.

Of course, if geneticists could make trees edible over the next few decades, we could be on a winner. Perhaps they could make it in different flavours. Warmer, and more CO2 would mean much faster growth, and more efficient use of water at the same time. Win-win-win !

Joe