| Kendall’s tau (τ) | P value | Trend classes |
| τ > 0.5 | P < 0.05 | Strong greening |
| 0 < τ < 0.5 | P < 0.05 | Weak greening |
| −0.5 < τ < 0 | P < 0.05 | Weak browning |
| τ < −0.5 | P < 0.05 | Strong browning |
| Other τ values | P > 0.5 | No trend |