By the way here is another picture: http://en.wikipedia.org/wiki/File:Atmospheric_CO2_with_glaci...
Human deforestation and burning of fossil fuel has raised atmospheric CO2 to over 380 ppm in the last century, well above pre-industrialized levels, and "off the scale" of this graph top.
The mean global temperature in the carboniferous period, with CO2 concentrations over double of present day was an astounding, just wait for it... 14C, which is the incredible, * unbelievable* 0C above the mean present day global temperature.
As CO2 levels spiked in the carboniferous period, it is marked by the drop of sea levels by 120m to the present day level, and as the CO2 level subsided, the sea levels rose 80m.
Sorry, but "off the scale" only counts when you actively pick and choose what scale you want to use, which in terms of geological temperature, CO2 and O2 concentrations quite literally means disregarding millions of years of geological time.
Also, when discussing matters scientific, please cite your scientific sources --- otherwise the discussion is of little value. Like so:
http://www.nature.com/nature/journal/v449/n7159/abs/nature06...
As other people have said, life on earth will go on in one form or another. But "off the scale" is a necessary term in this context to drive home the incredible turmoil and human suffering that will result as we are forced to adjust the local pressures of water shortages, mass human migration, and agricultural failures that will be caused by this...
This issue as other's have pointed out is the CAUSE of the current levels and the implications thereof.
In the past the high levels of C02 were at least partially due to ice ages, which prevented the normal processes for the mitigation of C02, once the levels built up enough the greenhouse effect melted the ice and restored the levels.
Look around, there's no ice age.
So not only is there no discernible cause for the increase except out actions, we don't have a huge C02-eating army trapped in the ice waiting to be released.
Some natural mechanism will probably step in, but who knows what effects it will have.
We are monkeying with a system we know to have far reaching and potentially devastating effects.
Here are estimated CO2 levels through geologic time -- "currently" rather low! -- at UCSD site:
http://earthguide.ucsd.edu/virtualmuseum/climatechange2/07_1...
CO2 is essentially airborne fertilizer. Our planet wouldn't be so green without lots of it. (I'd rather be alive during an interglacial, abundantly green geological period.)
Sure, but as with fertilizer on fields, there are consequences for using way too much.
> I'd rather be alive during an interglacial, abundantly green geological period.
As long as there aren't a billion or so refugees from the low-lying areas rampaging through.
Hence my link to CO2 levels over Geologic Time. Do you think there was "way too much" CO2 in the past?
Humanity survived the ice age, but that didn't make it a fun period in our history.
Does the fact that CO2 levels have varied hugely in Geologic Time affirm that we are under imminent threat of terrible climate changes? is it irrelevant? or contradictory? or a puzzle? is it impolitick to ask such questions?
Edit: I want to be scientific, include all relevant evidence, and some people here dislike it? (I'm not interested in the politics -- I've never even voted in a national election. And yes, I see these down-votes as a form of political activism. Disagree and argue if you have reason and facts.)