Forests and other natural carbon reservoirs play an important role in slowing and potentially reversing the effects of climate change. But any carbon stored in nature is vulnerable to either natural or human-caused disturbances. …Current accounting mechanisms for natural carbon storage do not adequately deal with the risk of loss due to disturbances. Typically, carbon offsets and removal credits focus only on the amount of carbon stored, and assume that this carbon will remain in storage indefinitely. But what if we measured and tracked both the amount and time of carbon storage? As we show in our new research published in Nature Communications, this can be done using the tonne-year metric — defined as the amount of carbon storage multiplied by the number of years that it remains stored. Tonne-years have so far been used to measure the equivalency of temporary to permanent carbon storage.