Temperature versus CO2 – the big picture

11/28/2018 16:11 - Posted by Tom van Leeuwen
When discussing “Climate Change” it’s good to have an understanding of how the Earth’s climate has changed in the past. That will give us a reference to decide whether the current changes are normal or not.

Global temperatures have varied a lot over the last 500 million years. Depending on the timescale used, the current temperature is either cold or hot, so when you want to know the “normal temperature” you’ll have to indicate what timescale you’re using.

The role of CO2 has been heavily disputed over the last century. In 1970, scientists were convinced CO2’s greenhouse effect was already saturated, even at concentrations measured at the beginning of the Industrial Revolution (1850) when CO2 was at around 300 parts per million. Saturation means that adding more CO2 has no measurable effect on global temperatures.
Later some climate scientists started to doubt that fact, so it’s important to include CO2 concentration measurements or proxies in this overview.

The geological timescale – 570 million years

On this timescale, we observe the largest climate fluctuations. Continents were formed and ocean currents changed in the process.
Temperatures were very high, 15 to 20 °C higher than now. During most parts of this period, no sub-zero temperatures were measured anywhere on Earth, so ice-caps were absent.
CO2 levels were very high, above 5,000 parts per million during most of this period. That’s 12 times the current levels. Live on Earth flourished, the continents were covered with thick woods and in the oceans, coral riffs started to grow. Carbon deposits were created in the form of deep ocean sediments, carbonaceous rocks and fossil fuels like coal, oil and natural gas.

55 Million years ago, with CO2 levels still well above 1,000 ppm, global temperatures started to decline sharply. These CO2 levels are considered extremely dangerous by the IPCC and according to them, those concentrations could cause a runaway warming process. Real-world measurements, however, show us the contrary. Temperatures declined.
This contradicts the CO2 greenhouse gas hypothesis.

It’s very clear that seen on this timescale, both the modern temperatures and CO2 concentrations are extremely low. There is, however, no clear correlation between temperature and CO2 levels. Other factors like continent formation, volcanism and ocean currents ruled the climate changes.

The Quaternary timescale – 2.5 million years

This timescale is marked by the latest and current ice age.

Over 30 glacial periods have been defined in this period. These glacial periods are separated by interglacials, each one of them lasting around 10 thousand years. The Holocene is the current interglacial we’re living in.
In one complete glaciation cycle, worldwide average temperatures fluctuate around 12 °C between the deepest glacial minimum and the warmest interglacial optimum.
Over this whole period of 2.5 million years, both the Earth’s polar regions present permanent land ice. As a result of glaciations, the North Pole ice cap can reach as far south as the current locations of New York and London.
In the figure above, we observe the latest three glacial cycles.
Seen on this timescale, we currently live in a warm period that has enabled humans to develop. However, we observe that the current interglacial is not as warm as the previous ones. Current temperatures are not extreme in a Quaternary context.

During the Quaternary, CO2 concentration and temperature have tracked closely. That raises the question about causation and effect.
If we follow the “official” greenhouse gas hypothesis, as published in the various IPCC reports, temperature follows CO2 concentration. So, the relation would be:

Unknown cyclical forcing (???)

CO2 concentration fluctuations

temperature fluctuations

That leaves a big question: What caused the CO2 concentration to behave this way? What cyclical forcing caused carbon to be released from its natural deposits like deep-sea sediments, carbonaceous rocks, fossil fuel deposits and CO2 dissolved in seawater?
Do we have evidence for... something like cyclical volcano eruptions, repeating every 100 thousand years? Mysterious cyclical vertical ocean currents that transport carbon-rich sediments to the surface every 100 thousand years? Or Intelligent life appearing every 100 thousand years, burning fossil fuels and then disappear?
No. There seems to be no logical answer to this question.

If we take the CO2-temperature relation the other way around, we obtain the following line of reasoning:

Milankovitch cycles

temperature fluctuations

CO2 concentration fluctuations

Now everything fits together.
The Milankovitch cycles are small alterations in Earth’s orbit around the Sun, like the orientation of Earth’s axis (precession), eccentricity and variations in the axial tilt that create cyclical variations in the solar energy input. These external influences result in the cyclical temperature fluctuations known as glacials and interglacials, more or less the same way the Earth’s axial tilt creates the seasons but with a much longer cycle length.
Warm oceans can contain less CO2. So, when oceans warm, CO2 from the oceans is released into the atmosphere.
As CO2 levels are extremely low at the onset of each warming cycle, well below the saturation point of its greenhouse effect, there might be a small positive feedback of CO2-induced warming that helps the other natural factors to lift the Earth out of each glaciation. But when temperature CO2-concentration reaches a certain level the warming stops.

We must conclude that CO2 concentration trails temperature. Temperature fluctuations are the cause, CO2 level variations are the consequence.

To give the figure some perspective, the modern CO2 concentration spike is included at the far right side of the graph. It is quite clear that CO2 levels have exploded over the last 100 years, completely out of sync with natural variation. Most likely this increase is due to human emissions. The carbon that was stored in the form of fossil fuels is released, using its chemical energy for human development: food production, transportation, medicine, and other human welfare enhancements.
Although the CO2 levels have risen by almost 50%, there is no corresponding spike in worldwide temperatures. More about the Modern Warming Period later in this article.

The Holocene timescale – 10 thousand years

Fifteen thousand years ago, global temperatures started to rise as Earth came out of the latest glacial period.

Welcome to the Holocene!

This interglacial has allowed the human race to develop like never before.
The Holocene Optimum was reached 8 thousand years ago with temperatures around 4 °C higher than today. Since then, temperatures have steadily declined, with some ups and downs like the Minoan Warm Period (3,500 years ago) the Roman Warm Period (2,000 years ago), the Medieval Warm Period (1,000 years ago) and the Little Ice Age that ended 200 years ago.
On this scale, we’re living in a cold period recovering from the extremes of Little Ice Age. Over 90% of the Holocene has been warmer than today.

CO2 levels have been rising over the last 8 thousand years to around 300 parts per million at the end of the Little Ice Age.
So, temperatures fell while CO2 concentration increased. This contradicts any claim that there is a positive correlation between CO2 levels and global temperature.

Modern Warming – 200 years

Temperatures are recovering from the coldest period of the Holocene, the Little Ice Age, so there has been some warming over the past 200 years.
There have been intervals with a clear correlation between CO2 and temperature, but during two periods, from 1940 until 1975 and since 2000 until now, the correlation has been inversed. Rising CO2 concentrations coupled with falling temperatures.
This is in contradiction with the CO2-hypothesis.


  • Global temperatures are recovering from the coldest period (Little Ice Age) of a warm period (Holocene) within one of the coldest periods (Quaternary) of Earth’s history
  • It is not true that we are breaking temperature records. Moreover, we’re much closer to breaking all-time cold records then all-time highs
  • It is true that CO2 concentration levels are the highest of the past 2.5 million years
  • It is true that rising CO2 levels are due to human carbon emissions
  • It is not true that these high CO2 levels are a threat to life on Earth. Life started and thrived at much higher global temperatures and CO2 levels
  • It is not true that CO2 concentration fluctuations are the main driver for temperature variation. None of the four timescales we've observed show evidence of a clear positive correlation between CO2 and global temperature.
So the CO2-hypothesis is contradicted by real-world, empirical observations.

View the facts without prejudice.

Tom van Leeuwen, November 2018.


Please donate

Fighting the climate hysteria is time-consuming! If you think I'm on the right track and you want to support my efforts I would be more than happy to receive a small donation that will help me to maintain this site.


The fingerprints of the greenhouse effect

The hypothesis of "man-made climate change" tells us that the increase in the concentration of CO2 enhances the greenhouse effect of the atmosphere and has global warming as a final result.

Since the beginning of the industrialized era around 1850, man emits relatively large amounts of CO2 into the atmosphere through the use of fossil fuels. The consequence of these emissions is that during that period, the concentration of CO2 in the atmosphere increased sharply from about 300 parts per million to more than 400 ppm, an increase of almost 40%. The average temperature increased in the same period more or less 1.5 °C with a small variation depending on the data source used.

Why did the warming stop?

The political reports of the IPCC are based on the hypothesis that CO2 is the most important control knob of the Earth's temperature. The problem is that this hypothesis does not correspond at all with the empirical data available to science. Forecasts are made using models that are not capable of 'predicting' the past.

Dutch Warming

In the Netherlands, the day-to-day whether depends heavily on the direction the wind is coming from. Being a small country, the wind direction is quite homogeneous for the whole country, specially on higher altitudes where the bulk of heat convection is taking place.

Due to its geographical position, midway between the icy-cold Arctic to the north, the dry and hot Sahara to the south, the Eurasian land-mass to the east and the Atlantic Ocean to the west, every wind direction comes with unique weather characteristics.

North - cold,
East - dry,
South - warm,
West - wet whether.

Satellite temperature observations

This month of January 2023, the average satellite temperature published, by Dr. Christy and Dr. Spencer (University Alabama Huntsfield) had a negative deviation, compared with the average monthly measures between 1991 and 2000.

Of course, this value does not mean much, it's definition is full of arbitrary begin and endpoints, but anyway it doesn't sound like a lot of warming has taken place over the past 30 years, and even less "catastrophic warming" we're reading about in the Mainstream Media, newspapers and TV stations.

CO2 saturation

This graph is all you need to understand that CO2 is not the Earth's Climate Control Knob.

On the horizontal axis, we see the Infra-red (IR) spectrum wavelengths, that is like "IR colors" were this kind of radiation visible to the human eye.
The vertical axis shows to energy flux, that is the energy emitted by the Earth, as seen from outer space.

The graph itself shows how the Earth's atmosphere filters the IR radiation emitted by the Earth's surface and the role of the various greenhouse gases in that filtering process. The green line is the filter of the Earth's atmosphere without any greenhouse gases.

Video - Who are the real climate deniers?

The climate has shown many fluctuations during the Holocene. The difference between the highest and lowest average temperature of the past 10 thousand years is about 3 °C.

Climate alarmists, led by the IPCC, are trying to deny this, and understandably so. This variation means that without human influence there was climate change as well.

This undermines their hypotheses and often their jobs depend on it.

Climate change seen from a historical perspective.

Satellite Earth temperature February 2022

The satellite temperature departure measurement for February 2022 is exactly 0° C.

This means that Earth temperature during February 2022 was exactly the same as the average from 1991 to 2020.

Satellites are the best way to have insight into the short-term temperature variations. They measure the whole surface, independent of weather station distribution, Heat Islands, measurement failures, surface condition (land or water).

There is a step-wise increase in temperature, triggered by two very strong El Niño events (1998 and 2016.) The energy that welled up from the deep oceans established a new level in these two ocasions, where the warming paused. This is a natural phenomenon and has nothing to do with CO2, or human activity.

Where is the Climate Emergency? It just does not exist.

Wake up and spread this information to your government!

Tom van Leeuwen, March 1st, 2022.