The unit for greenhouse gas (GHG) emission rate is typically expressed as mass per unit of time, most commonly in terms of:

• Kilograms per hour (kg/h)
• Kilograms per day (kg/day)
• Metric tons per year (t/yr or Mg/yr)

For example, CO₂ emissions might be reported as kilograms of CO₂ per hour (kg CO₂/h) or metric tons of CO₂ per year (t CO₂/yr).

When expressed in micrograms, the unit for greenhouse gas (GHG) emission rate is typically given as:

• Micrograms per second (µg/s)
• Micrograms per minute (µg/min)
• Micrograms per hour (µg/h)
• Micrograms per day (µg/day)

For instance, CO₂ emissions might be reported as micrograms of CO₂ per second (µg CO₂/s) or micrograms of CO₂ per hour (µg CO₂/h).