They showed that 350 parts per mil­lion CO2 in the atmos­phere is the safe limit for humanity.

The bad news is we’re already past that num­ber — we’re at 390 parts per mil­lion, which is why the Arc­tic is melt­ing, why drought is spread­ing across the planet, why human­ity is fac­ing per­haps its great­est chal­lenge ever.

The good news: that num­ber gives us a tar­get to aim for.

If you’re free Sat­ur­day between 8am and 3pm, join in the activ­i­ties for the Inter­na­tional Day of Cli­mate Action, begin­ning with the aer­ial pho­to­graph (using a boom lift, not a fuel guz­zling heli­copter or other air­craft) of hope­fully hun­dreds of peo­ple form­ing the num­ber 350 at Hong Lim Park.

More details of the day’s activ­i­ties can be found here.

Set your Twitter account name in your settings to use the TwitterBar Section.