Variability of the Earth’s climate - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 70

glacial period from 330 to 280 million years ago was the deepest and is referred to
as the ''Permo-Carboniferous period''.
(3) There was an additional cold period centered on 150 million years ago when
global average temperatures dropped by about 10 C to perhaps 15 C.
(4) Starting around 50 million years ago, the Earth entered into a period that was
mainly a cooling trend.
2.3.10.3 CO 2 variability during the Phanerozoic
In this section, we discuss the evidence from the Phanerozoic (the past 540 million
years) regarding CO 2 concentrations. We begin with a brief summary of results
provided by Berner (2004), which provides a good overview and introduction, and
follow that with data from other sources. The ''short-term carbon cycle'' is
described by Berner (2004) as shown in Figure 2.29 . The word ''short-term'' is
used for characteristic times for transferring carbon between reservoirs that range
from days to tens of thousands of years:
''Carbon dioxide is taken up via photosynthesis by green plants on the
continents or phytoplankton in the ocean. On land carbon is transferred to soils
by the dropping of leaves, root growth, and respiration, the death of plants, and
the development of soil biota. Land herbivores eat the plants, and carnivores eat
the herbivores. In the oceans the phytoplankton are eaten by zooplankton that
are in turn eaten by larger and larger organisms. The plants, plankton, and
animals respire CO 2 . Upon death the plants and animals are decomposed by
microorganisms with the ultimate production of CO 2 . Carbon dioxide is
Figure 2.29. The short-term carbon cycle (adapted from Berner, 2004).