F. Earth is Currently in an Ice Age.
Earth is currently in its last ice age known as the Quaternary Glaciation. During an ice age there are several glaciers advancing cycles, retreating cycles, and interglacial period. We are currently in an interglacial period. This has been going on for millions of years. The following graph shows 5 major ice ages. The ones applicable to this analysis are shown on the far right hand side of the graph going back 542 million years ago. During this period, there has have been 3 ice ages.
The Andean-Saharan Ice Age was about 460 million years ago and lasted 40 million years. The next is called the Karoo glaciation about 300 million years ago and it lasted about 100 million years. The last and current one is the Quaternary Glaciation that started 2.58 million years ago and is currently ongoing. It has had many advancing, retreating, and interglacial periods.
The earth is currently in an interglacial period inside the Quaternary Glaciation Ice Age. The current Quaternary Glaciation Ice Age has undergone many periods where glaciers are advancing, several where glacier are retreating and several interglacial period in between. The earth is currently in one of those interglacial periods. This is illustrated by the Rhode graph going back 450,000 years ago. Note, the up and downs in the temperature where it ranges around 9 to 10°C. In every one of the peak periods, the ice age was and is ongoing. It did not stop, the glaciers did not melt or disappear.
Ice ages are triggered by variations in the earth’s orbit known as the Milankovitch Cycles. [Citation] [Berger A. (1988) Milankovitch Theory and Climate, Reviews of Geophysics, Vol 26, No. 4, pgs. 624-657. Marsh G. Interglacial, Milankovitch Cycles and Carbon Dioxide, Argonne National Lab. https://arxiv.org/ftp/arxiv/papers/1002/1002.0597.pdf%5D . Berger stated:
“Recent new evidence seems to have laid to rest the arguments that orbital variations might cause only minor climate fluctuations but not the major climatic changes manifested in the ice ages, the largest and most abrupt climate changes known during the past 2 myhr. Among the competing theories to explain the coming and going of the Quaternary ice ages and other similar climatic variations of the past, only the astronomical theory (of which the Milankovitch theory is a particular version) has been supported so far by substantial physical evidence.” Pg. 647
Marsh G stated:
“Unlike what was believed then, it is known today that for Earth’s present climate water vapor is the principal greenhouse gas with carbon dioxide playing a secondary role.” Pg. 2
“Carbon Dioxide appears to play a very limited role in setting interglacial temperature.” Pg. 13
It is apparent from the Rhodes chart above, ice ages are not triggered by warming and cooling periods or carbon dioxide. In fact, there have been many warming and cooling periods of ±10°C in the middle of the current ice age. According to the Milankovitch cycle the Earth is expected to enter an advancing glacial period in about 50,000 years from now. There are many periods within the current ice age where the glaciers advanced and periods where the glaciers retreated. This is illustrated by the Rhode Figure above. Glaciers have been retreating for the last 25 thousand years and have apparently slowed. The Greenland Jakobshavn Glacier is currently advancing. It became 22-33 yards thicker in the last three years (2016 -2019). The Jakobshavn is 40 miles long and more than a mile thick and was the source of the iceberg that sank the Titanic.