1/7 New paper: ‘A cautionary tale about using the apparent carbon accumulation rate (aCAR) obtained from peat cores’: http://www.nature.com/articles/s41598-021-88766-8. A follow-up to: http://www.nature.com/articles/s41598-019-53879-8. #PeatPaper #PeatTwitter #palaeoecology

2/7 We demonstrate how the calculation of aCAR is based on a misapplication of the mass balance equation – the underlying principle that explains carbon accumulation rates in peatlands.

3/7 We use a simple peatland model to show from first principles why aCAR is an erroneous measure of net carbon balance.

4/7. We extend the simple model with DigiBog to simulate the millennial development of a sloping blanket bog and show how climatic changes in deeper peat are poorly and misleadingly represented by aCAR.

5/7 We note aCAR should not be used as a measure of past rates of peatland C accumulation. Studies that have used it to infer effects of past climate or management on peatland C balance may need to be re-visited, especially if they have been used to inform policy.

6/7 We also note that peat-core data can *still* be used to infer rates of C accumulation in peatlands. Age-depth or age-mass models and peatland development models can be combined to estimate past rates of net C balance, but more work is required by the peatland community.

7/7 As Clymo (1984) wrote: “The very concept of 'peat accumulation rate' thus needs careful consideration. To calculate it as the difference between two … dates divided by the depth between the samples from which they were measured… may be seriously misleading.”.