Thanks to help from jules, I've been able to implement a flow graph which causes the player to loose health at a slow rate between the hours of 6pm and 6am. I thought this was a condensed representative of the increased desire for heaters etc. in colder months, which correlates with the large increase of Co2 emissions.

The health decrease stops when the player is within range (10) of the heater, indicating that when the player is warm the player is happy and the dependence of humans on technologies to keep warm.