ATMOSPHERE EVOLUTION 205 Figure Phanerozoic temperature history (Reproduced from with permission from Berner RA Geocarb II: A revised model of atmospheric CO2 over phanerozoic time, Am Jour Sci., 294: 56 91) PAL at the end of the Carboniferous Massive carbon burial and increased solar radiation by the Carboniferous meant that atmospheric oxygen concentrations were greater than at any other time in Earth history (see Palaeozoic: Carboniferous) This may have allowed the existence of the huge Carboniferous insects observed in the fossil record (see Fossil Invertebrates: Insects) Insects rely on diffusion-limited flow