There is no doubt that Earth has a fairly consistent cycle of Ice Ages followed by interglacials, or Warm Ages. Using physical geologic evidence of the last Ice Age, and by analyzing and comparing ice cores, ocean sediment cores, and other samples that preserve air and climate data within them, scientists have an understanding of Earth’s overall climate back for over 400,000 years.
There is a pattern to the data that suggests an approximate 100,000 year cycle that includes a 90,000 year cold period (Ice Age) followed by a brief 10,000 year warm period (Warm Age.) While this cycle can vary, the fact is that we have been in a Warm Age for over 10,000 years. Another unusual aspect of the current pattern is that typically the Warm Age rises to a sudden peak followed by a fairly rapid cooling period. The current Warm Age suddenly began and peaked about 11,000 years ago. The Earth has stayed relatively warm, and is in fact, continuing to get warmer.
The question is, are we missing an Ice Age?
GRAPH 1.0 is the data from the Vostok Station ice cores in the Antarctica. The top (blue line) graph indicates the trending air temperature, the middle graph (green line) indicates CO² levels trapped in the ice, and the bottom graph (red line) indicates the dust found in the ice samples. Note that present day is on the left side of all of the graphs and to the right is going farther back in time. Ice core data is not precise because of several factors; however, the data indicates the conditions within a 6,000 year margin of error.
The data indicates that there was a sudden warming starting at about 15, 140, 245, and 330 thousand years ago. The CO² has similar peaks but lags behind the temperature increases by 200 to 600 years. Dust seems to also correlate with the temperature variations, but whether low dust causes warmer temperatures, or warmer temperature cause a cleaning of atmosphere by increased rain, is unknown.
The consistency of the cycles indicates that there is some mechanism that drives the cold/warm periods which would be difficult to explain using Earth-bound causes. Volcanic periods, plate tectonics, ocean currents and other activities on Earth that might influence our climate don’t seem to have cycles that could be matched to the ice core data; however, there are exo-mechanisms (outside of Earth) that could help to explain the Ice/Warm Age cycles.
Earth as a Battery
Everyone knows that the Earth warms in the Spring and Summer and cools in the Fall and Winter. The reasons for this are due to Earth’s 23.5° tilt as we orbit around the Sun (SEE: 23.5 Degrees = Seasons on Earth.) Based on our firsthand experiences, it might be easy to believe that the Earth’s relationship to the Sun, outside of the annual march of the seasons, is relatively constant; however, it is not.
Earth’s orbit and tilt change over time and there is a significant difference in how much of the Sun’s energy (solar radiation) that Earth receives based on its relative position with the Sun. This is important because the energy our planet receives from the Sun is like a battery charger for our climate. When Earth absorbs more energy, the battery charges and we have a warmer, more active climate. When the Earth absorbs less energy, it cools and our climate reacts accordingly.
There are multiple factors that change Earth’s position in relationship to the Sun. Almost 100 years ago, Serbian geophysicist and civil engineer, Milutin Milanković noted these astronomical variations and suggested a theory of climate change based on these factors now known as the Milankovitch Cycles. In Part II of this series we will learn about the changes in Earth’s orbit and tilt that result in variation of the amount of solar radiation our planet receives. In Part III we will discuss Earth’s current status in the Milankovitch Cycle and why we may be overdue for an ice age.
PART II – Understanding the Milankovitch Cycles, Clues to Earth’s Climate Changes
PART III – Should We Be In An Ice Age Now?