I prefer #3, with some modifications to the % sign, and perhaps someway to make the earth also look more like a zero. #2 is my second pick, and is more ready for use today as is.
Ideally, I would like to see more time available before a ten percent challenge campaign logo is selected. It is really for the participatory campaign, which is still a little ways (not far) off. For the immediate need of the 31st an Alliance for Climate Action, logo could be used, and existing letter head can serve nicely.
I know this may not fit with needs of the day, or other thinking, so I am flexible.