Geological Record of the Earth's Temperatures

Since about the 1970’s, the big topic has been global warming. Before that time, the big topic was global cooling. In both cases, several unsubstantiated claims were made, usually attributing the ‘huge’ change to man. Pre-1970, the culprit was aerosols, which were thought to somehow be causing the globe to cool down. After the 1970’s, the blame went to carbon dioxide emissions. What does the geological record show?

The geological record comes from rock core samples and when the general non-scientific public sees that record, they are often surprised. It is important to note that both in the case of global cooling and global warming, the advocates were and are focusing on trends, rather than climate. The geological record spans enough time that the actual patterns become far clearer. The above graph shows the temperatures over the past 500 million years according to the geological record.

Let’s break it down a little. Here is the graph showing the temperatures from 500 million years ago to 80 million years ago.

The numbers along the vertical side of the graph represent degrees in Celcius above and below 0. The 0 number represents the global average temperature from 1960 to 1990. This part of the graph covers a period of about 400 million years (the graph actually covers about 520 million years).

Of special interest in this segment, note that in all but about 50 million years, temperatures were higher and often substantially higher than the 30 year average of 1960-1990. That included a spike where temperatures were 14 C higher than the average. The relatively small part when the temperatures were below what they are today was a time of glacier formation, known as the Permian Glaciation. It was an ice age.

During this 400 million year span, there were two major mass extinctions. In neither case were the temperatures at the maximum cold or warm.

This part of the graph spans the time from 1 million to about 65 million years ago. What stands out in this part is that there was another peak of 14 C or about 27 F above the temperatures today, but it didn’t occur until over 10 million years after the mass extinction 65 million years ago, in which the dinosaurs perished.

Also, notice that the line starts going up and down rapidly much more in this section. This is mostly because the closer we get to the current time, the more accurate the geological record becomes. Still, it is easy to see that the global temperatures are trending downward since the peak temperatures around 48 million years ago. They became colder than they are today around 2.5 million years ago.

This part of the graph spans about 20,000 years ago to 1 million years ago. Most of this 880,000 years, temperatures were below what they are today by up to about 6-7 degrees C. There were exceptions and four times the temperatures rose to several degrees C above what we are experiencing today. However, for almost all of this time, over 800,000 years of it, the temperatures were colder than today. This was the beginning of the series of ice ages.

It is quite interesting that the coldest that temperatures got was only about 7 C below what they are today. The hottest periods of the 500 million years were twice this amount of temperature difference above today’s temperatures. Indeed, it is believed that a drop of only 5 C would be enough to trigger another ice age.

This period saw more fluctuations in temperatures than in the previous 499 million years. The civilizations of man hadn’t yet begun yet and they weren’t in the picture during those 499 million years when temperatures were far warmer than they are today.

This is from 20,000 years ago to today. About 17,500 years ago, temperatures finally began to increase. They got to roughly what they are today about 11,000 years ago and this was when the glaciers from the last ice age began to finally melt. This is why it is often stated that the ice age ended 11,000 years ago, though the trend actually began about 6,500 years earlier. 

Of tremendous interest is that though there are fluctuations above and below today’s temperatures, the temperature has remained relatively constant for the last 11,000 years, despite the presence of man and the technological advances that occurred over that period of time. 

The three-tenths of a degree increase in temperatures that have been recorded over the past century is well within the amount of fluctuation there has been for 11,000 years. Looking at the past 11,000 years, in fact, it is easy to see that there is no basis to say whether there is a tremendous warming or cooling going on. We simply don’t have the knowledge to say if this is anything out of the ordinary. What’s more, if you average the temperatures over the past 500 million years, you’ll find that we are actually about 16 degrees F or 8 degrees C below the average temperature over that period of time. 

People tend not to look at things over the long term. When we do, it puts things in amazing perspective. 

Credits: Graph by Glen Fergus, CC SA 3.0

The credits Glen gave for the graph, based on 14 scientific reports, are found here.


What do you think?


Written by Rex Trulove

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  1. There could also be outside factors in causing global warming or cooling. We are being taken around the center of our galaxy by our Sun. It could be that the Sun is moving to a warmer part of space or a colder part of space. Yes the background microwave radiation is at 3 degrees Kelvin, but that doesn’t mean that this is the constant temperature. There could have been other stars closer than 4 light years that caused the temperature of the space in which the Earth and Sun and planets are , and this or these other stars could have warmed up the area. There are too many variables to really make statements as to the cause of global warming or cooling.

    • The earth and the sun not only move around the Milky Way, they also bob up and down through the spiral arm, moving from above it to below it and above it again. The sun is also variable in its energy output. This is something we’ve only known for a few decades, but the output wavers and Earth gets its weather and climate from the sun. The earth’s magnetic poles also periodically swap and this could very well impact such things as the climate and weather. Many more things can impact our weather, too, all having nothing to do with humans.

  2. 0 reactions…positive or negative? Thanks for this. Here is my problem with the whole premise that some people won’t even question or leave up to conversation. If you don’t agree with the assessment you must be an idiot, unintelligent, misinformed-all of this closes down any conversation.

    I am a huge lover of the earth and I feel it’s great if we try to improve the way we treat our planet but I don’t feel it’s the government’s job which has its own agenda.

    The problem with the whole global warming or cooling situation, for me, is that it’s like saying in the scope of time comparison, the daylight in the winter is getting shorter so it must mean we are losing the sun and must fight to save it. We capture such an insignificant measurement of time and make hypothesis about the whole process of the earth that has been supporting life long before man ever stepped into the landscape.

    True science doesn’t change its parameters to suit its conclusion. All facts are taken into account and logic is applied, not emotion, shame or bandwagonning. The whole problem is there is an agenda, the government is constantly coming up with other attempts at streams of income.

    If there is a problem, you don’t make special adjustments to those with money. We are banning all burning in the forest because of a risk of fire, unless you have fire credits than you can pay to have a fire. The whole carbon credit idea is just a way for some with more funds to get what they want.

    I thought it was funny when the olympics in South America I think had a major display of green and global warming awareness in their opening ceremonies. I just thought of all the planes that flew all the people to the olympics and now we are lecturing on global warming…I don’t like contradiciton and I see so much of it in the argument over climate change.

    Several factors that are red flags. You don’t change the name of a science to suit the change conversation…global cooling, wait no global warming, wait no climate change. The whole premise of climate change is amazing…it has and will be changing long before us and long after we have faded into obscurity.

    You don’t degrade someone that doesn’t agree with your premise and make them somehow stupid or uninformed, this is where emotion and anger trumps logic and reason.

    If there is a problem, you don’t offer coupons or options for those that don’t want to follow the movement as long as they have cash to do so.

    You can’t ignore a whole earth timeline because the facts don’t support a conclusion.

    Thanks for this post and sorry for the long reply. I believe we need to have a conversation that is adult, sober and reasonable. We all have our opinions, we can improve our earth but it’s the people that will do it not the government. Let’s pick up trash in our communities, let’s not trash our planet but let’s do it with reason and logic. Thanks again and good to read your post again, it’s been too long.

    • I don’t mind long comments. I’ve been known to be a bit verbose, myself. I also agree with what you said. It gets pretty bad when science is politicized to the point where NASA, NOAA, and the NSA feel that it is necessary to falsify data and then claim that it is just an ‘adjustment’. Of course, all three agencies get their money from the government, so it is pretty clear that they are doing and saying what the government wants to hear.

      For that matter, the reason climatology is a pseudo-science is that they don’t follow the rules of science. For that matter, I’m a climatologist. You don’t need a science degree to be a climatologist and in fact don’t need any college education, which I do have.

      The way I see it, we don’t have nearly enough knowledge or data to make a reasonable guess about the climate, even when the data isn’t tampered with. Climate is the average of weather over a century or longer and most of the weather stations that exist now didn’t exist a century ago.

      I *do* agree that there is climate change. The graph I used in this article clearly shows that the climate is dynamic and not static, so the climate has been changing for at least 500 million years. To think that it would stop is silly.

      Blaming a warm trend on CO2 levels is also unsupported. As this graph and others shows, CO2 levels do increase, but they do that AFTER warming, not before it. CO2 also isn’t as powerful a greenhouse gas, nor anywhere near as abundant as water vapor.

      Either way, the government is overstretching its authority when they start mandating things like this. Using Al Gore as a spokesman was also a very unwise move. His carbon footprint is over 10 times that of an average family.

      I do think that more needs to be done to lower pollution and this is the responsibility of all individuals. Here in Montana, the US Forest Service does burn forest slash to get rid of fuels that can contribute to forest fires, but that produces far less pollution than one of the fires.

      I could also go on, but better stop. Like I said, I tend to be verbose.

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