We are surrounded by numbers throughout our daily lives. Some, you’ll recognize easily. 24: the number of hours in one day. 365: the number of days in one year (except for leap years). $100: roughly the amount of money in my bank account at the moment. But what about 406.95 parts per million (ppm)? If you’re not a climate geek, you’re probably not familiar with it, but you really should be since it’s an incredibly important number for our planet.