In 1850, scientists began recording semi-detailed, quasi-global temperature data. While earlier records exist, they are less reliable, and more localized. Of course, 161 years isn’t much data, especially considering that the earth is believed to be about four and a half billion years old. In order to get earlier temperature data, we have to turn to a field of science known as paleoclimatology.
Why is Paleoclimatology Important?
Paleoclimatology is the study of earth’s ancient climate. Since scientists often examine the past in order to better understand the present, paleoclimatology has huge ramifications on the wider climate change debate that rages today.
As mentioned earlier, fairly reliable temperature data exists back to 1850. For earlier periods, scientists rely heavily on proxy measurements. In other words, ancient temperatures are inferred via preserved physical objects. Dendroclimatology, or the study of changes in tree growth via tree rings, is one source of proxy data. Others include coral rings, ice core samples, differences in sedimentary rock levels, and borehole temperatures. Using these proxies, as well as observations recorded in ancient texts, scientists have been able to reconstruct temperature data as far back as 2,000 years for some areas in the northern hemisphere.
The field of paleoclimatology attempts to go back even further. It uses similar proxy sources as the ones mentioned above. Unfortunately, there are some limitations to this practice. Currently, the oldest ice cores are just 800,000 years old while the oldest marine sediments are only 200 million years old. Adding to the difficulty, these sediments have been influenced over time by chemical and physical changes. The biggest problem is that our confidence of proxy sources deteriorates the further back in time we go.
Despite these challenges, paleoclimatology scientists have constructed a timeline of historical temperatures on Earth going back about 500 million years. The chart above provides an overall perspective on what temperatures might have looked like over the course of that time period (please note that it uses a logarithmic scale).
Guerrilla Explorer’s Analysis
Assuming that the data is fairly accurate, the chart represents about 11% of Earth’s 4.5 billion year history. Unfortunately, it’s difficult to go back any further due to a lack of reliable proxy sources.
So, what conclusions can we draw from this paleoclimatology data? Well, for one we can see that there are about four cycles of ice ages and non ice ages, with about 140 million years separating each one. Second, temperatures have fluctuated fairly wildly throughout these cycles. Third, we are in an ice age as we speak. The Quaternary glaciation began about 2.58 million years ago. Surprised? Well, the reason it doesn’t feel more like an “an ice age” is that we are in a warmer, interglacial period.
Fears over a coming glacial period have existed for decades. Back in 1972, a group of paleoclimatology scientists suggested that “it is likely that the present-day warm epoch will terminate relatively soon if man does not intervene.” Thanks to scientific advances, most scientists no longer worry about so-called global cooling. In fact, most paleoclimatology scholars expect the current interglacial period to last another 15,000-50,000 years.
It should be noted that the present interglacial period, which encompasses the last 10,000-15,000 years, has been quite stable and warm compared to the previous one. This period of climate stability may be more important than it first appears. Some even think that it has been a decisive factor in allowing humanity to blossom into the present civilization we enjoy today.