Present day land cover uncertainty and historical land cover change work published in Climate Dynamics.

This work, using the NCAR Parallel climate model (PCM), showed that uncertainty in the way land cover is classified can have a significant impact on the simulated global climate, and in fact that these uncertainties could lead to greater differences in simulated climate outcomes than the simulation of human land cover change.

Figure 1: Different land cover representations for present day (a, b and c) and compatible pre-human and present day land cover (d and b)

Comparing the effects of present day uncertainty (i.e. compare simulations using land cover 1a and 1b) and the effects of human land cover change (i.e. compare simulations using land cover 1d and 1b) shows that the uncertainty in land cover in Siberia and parts of the Amazon can have significant consequences on simulated climates (figure 2) and that these changes are potentially as large as those associated with human land cover change (figure 2b). Note that most of the historical human land cover change is linked to cooling in the mid-latitude agricultural zones.

Figure 2: Temperature changes associated with uncertainty in present day land cover representation by season

Figure 3: Temperature changes associated with historical human land cover change.

One of the outcomes of our simulations was the significant change in daily temperature range (figure 4). Observations (figure 5) suggest that similar changes have been observed over the last few decades (from the IPCC, 2001).

Figure 4: Simulated changes in daily minimum and maximum temperatures due to historical human land cover modification. These results generally lead to a decreased daily temperature range for most agricultural areas.

Figure 4: Observed Daily temperature range changes in the observation record (IPCC, 2001)