The picture with the snowy mountain is first because the snow typically happens naturally and the black and white photo is next because the snow is melting witch could happen because of climate change witch leads to the final photo with the mountain that has not snow
there are changes in the climate which result in the enviorment changing
i think that the first picture (the one with snow) happened first because it shows the most "natural" of them all, with snow in the beguning and melted into picture number 2 (the gray pic). it shows climate changing resulting in the mountain snow to melt faster and developing into something similar but different.
