Okay- so I'm studying geography at university and I love the message of this game, I really do. I get exactly where you're coming from and why you've included what you have (2 years of Earth Systems has forever ingrained ppm into my head), but...
The game seems completely impossible. Nothing made any difference to the ppm, metric tonnes, + or - anomaly temperature etc. I played this non-stop for over an hour and a half (addictive and competitive personality!), planted over 1 billion trees, and the temperature kept on rising.
I get that it's meant to be representative of real life, and that temperatures are rising and there's not a huge deal we can do to stop it (arguably we've already reached the tipping point/ peak oil etc) but if you want to get your message across, it needs to be somewhat easier.
I know that there's probably not meant to be an 'end' where everything turns out fine and people stop polluting because it would be unrealistic, but if you're going to give this an informative slant people will have to see some kind of progress, surely? Otherwise what's the point? You'll click and click over 15,000 times and see no change. It won't encourage anyone to change their behaviours or attitudes, in fact, even a fairly eco-conscious student like myself ended up thinking "f*ck it, why bother campaigning or planting a billion trees if it'll just keep getting worse? Might as well do nothing".
Again; maybe the point of this isn't to educate or change attitudes, maybe it's some kind of nihilistic scream into the void, a "what's the point? We'll die anyway" type thing- but if it's not, maybe try making it so there's some visible progress, so the game doesn't last as long so people still care when you give them your message of reducing carbon foot-prints and making conscious decisions to at least try and preserve and cool our planet. Maybe like 'The McDonald's Videogame' by Molleindustria?
Sorry this is so critical, but I care about the message and I love games with meaning- I want this to do well and the message to spread!