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We are already above 350 ppm, and have been for 20+ years. (We’re not talking about a future event here.)
Warming was already taking place before he hit 350 ppm. (We used to call it “The Greenhouse Effect.”) Dramatic changes were noted in the 70's but the warming started well before that:
Please, read what Hansen et al really said about 350 ppm:
http://dx.doi.org/10.2174/1874282300802010217
[font face=Times, Serif][font size=5]Target Atmospheric CO[font size="1"]2[/font]: Where Should Humanity Aim?[/font]
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[font size=2]Abstract: Paleoclimate data show that climate sensitivity is ~3°C for doubled CO[font size="1"]2[/font], including only fast feedback processes. Equilibrium sensitivity, including slower surface albedo feedbacks, is ~6°C for doubled CO[font size="1"]2[/font] for the range of climate states between glacial conditions and ice-free Antarctica. Decreasing CO[font size="1"]2[/font] was the main cause of a cooling trend that began 50 million years ago, the planet being nearly ice-free until CO[font size="1"]2[/font] fell to 450 ± 100 ppm; barring prompt policy changes, that critical level will be passed, in the opposite direction, within decades. If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO[font size="1"]2[/font] will need to be reduced from its current 385 ppm to at most 350 ppm, but likely less than that. The largest uncertainty in the target arises from possible changes of non-CO[font size="1"]2[/font] forcings. An initial 350 ppm CO[font size="1"]2[/font] target may be achievable by phasing out coal use except where CO[font size="1"]2[/font] is captured and adopting agricultural and forestry practices that sequester carbon. If the present overshoot of this target CO[font size="1"]2[/font] is not brief, there is a possibility of seeding irreversible catastrophic effects.[/font]…[/font][/font]
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