Simulated dust activity in typical time periods of the past 250 million years.

The dust cycle in three typical time periods of the past 250 Myr, namely 240 Ma, 130 Ma and 80 Ma, is studied using the climate model CESM1.2.2 combined with the vegetation model BIOME4 and compared with that of the present day. The atmospheric dust loading obtained for these three periods is 35.9, 9.7 and 3.2 Tg, respectively. In comparison, the present-day dust loading is ∼24 Tg. It is found that the area of subtropical land is the major controlling factor in the variation of dust loading; the climate and the land plant evolution play a relatively minor role in these experiments where continental ice sheets are not considered and the reliability of BIOME4 in simulating vegetation of deep time is still uncertain. Although the simulated atmospheric dust loading in 240 Ma was much higher than that simulated for today, the fraction of dust deposited into the ocean (26%) was much lower due to its supercontinental configuration. Dust was able to cool the local annual mean surface temperature by a maximum of 2 °C in 240 Ma. A warming is obtained in the northern polar region in both 240 Ma and 130 Ma, likely due to strengthened meridional oceanic heat transport rather than due to snow darkening.