In geologic time, our planet currently is in the Holocene Interglacial period which began approximately 10,000 years ago. The preceding interglacial period, frequently called the Eemian Interglacial, had lasted from roughly 130,000 to 107,000 years ago.
For the past 400,000 years, Antarctic ice has preserved a record of the variations in temperature, methane, and atmospheric carbon dioxide concentrations present on earth. Please see the references listed below.
Scientists have studied the gases trapped in air bubbles within the ice cores extracted from the Antarctic ice sheet and have compared their concentrations over those 400,000 years represented within the samples. When narrowed down to just the comparison of the Eemian and Holocene epochs, both interglacial periods were relatively short in duration and were initiated by natural cycles of global warming.
The Eemian strongly resembled our present Holocene’s climate, except that sea levels were roughly four to six meters higher at the peak of the Eemian warmth compared to our current sea heights. Based upon exposed coral reefs in disparate locations around the globe and terrestrial pollen core records, the Eemian was slightly warmer everywhere than our present late-Holocene environment.
How did changes in temperature and the atmospheric carbon dioxide and methane concentrations measure out when they were studied across the 400,000-year record represented in the Antarctic ice cores? THEY MATCHED ALMOST PERFECTLY!
Levels of carbon dioxide (parts per million) and methane (parts per billion) followed every rise and fall of the changing temperatures throughout the past 400,000 years. Peaks for the three parameters simultaneously occurred at approximately 324,000 years ago, repeated at 236,000, then again at 126,000 years ago (Eemian), and recently now. Troughs for all three happened approximately at 330,000, at 265,000, at 135,000, and lastly at 21,000 years ago.
What are the factors that have caused these natural cycles for very prolonged ice ages interrupted by short periods of natural global warming? Are there processes existing beyond our planet’s orbital variations, and do they operate within our real world such that we have not yet been smart enough to include them in our climate change models? Any reasonable theory on climate change must account for the three peaks of global warming and the four prolonged troughs of global cooling delineated above prior to the Holocene epoch.
Here are some questions to consider regarding climate change:
— Do atmospheric carbon dioxide and methane concentrations increase predominately as a response to rising global temperatures?
— If airborne carbon dioxide and methane actually cause global temperatures to increase, then what were the natural processes that created the increases in carbon dioxide and methane which initiated the Eemian and Holocene Interglacial epochs? Do these natural processes continue today to influence our climate? What extracted sufficient carbon dioxide and methane out of the Eemian epoch to bring on our planet’s last Ice Age? Are these processes known and accounted for in our latest computer modeling for current climate changes?
— Where does the heat generated within the earth’s core go? Does it escape uniformly or in cycles from our planet’s interior through the crust’s oceans?
For more information and speculation about natural theories on climate change, please visit Spirit Made Smaller and also the author’s blog, “How Much Climate Change Comes from the Earth’s Core,” dated June 11, 2014.
1. Blunier et al., 1997: Timing of the Antarctic Cold Reversal and the atmospheric CO2 increase with respect to the Younger Dryas event. Geophys. Res. Let., 24(21), 2683-2686.
2. Fischer et al., 1999: Ice core records of atmospheric CO2 around the three glacial terminations. Science, 283, 1712-1714.
3. Petit et al., 1999: Climate and Atmospheric History of the past 420,000 years from the Vostok Ice Core, Antarctica. Nature, 399, 429-436.