When discussing climate change, it usually goes hand in hand with discussing carbon dioxide levels because of the impact carbon dioxide and greenhouse gases can have.
In this guide, we look at the history of earth’s carbon dioxide levels over time, and recent C02 concentration levels (and the significance of that).
Summary – Earth’s Carbon Dioxide Levels Throughout History
- Today, in 2019, carbon dioxide concentration levels are around 410ppm. This is higher (by far) than at any point in at least the last 800,000 years (CO2 levels have always went up and down between about 200 and 300ppm)
- The rate at which carbon dioxide is increasing is around 100 times faster than the increase that occurred when the last ice age ended
- Pre industrial levels of ppm were about 280, and since we started burning fossil fuels heavily, they are at current levels
- The last time ppm levels were around this high might have been about 400 million years ago
- It is thought that CO2 levels could have been the same or higher in Earth’s ancient past without catastrophic consequences because of a more gradual increase in CO2, and because of variables like a less active sun
- It’s worth noting that CO2 levels from the past are obtained from ancient samples such as shells from deep sea sediments, and ice cores (mainly from Antarctica and Greenland). So, their accuracy is dependent on the reliability of these types of samples
Why Are Carbon Dioxide Levels So Important To Monitor?
- Greenhouse gasses – mainly CO2, but also methane – have been implicated in most of the climate changes in Earth’s past. When they were reduced, the global climate became colder. When they were increased, the global climate became warmer.
Humans are the main cause for the level of GHG emissions in modern times, especially since 1950. Greenhouse gases have been observed to either be absorbed by the ocean and create ocean warming or acidification (and other issues), or more commonly, they rise in the atmosphere/ozone and reflect heat back at the earth’s surface – creating further warming.
What Are The Carbon Dioxide Levels On Earth Right Now?
- As of January 2019, carbon dioxide levels are 410 ppm (parts per million)
At What Rate, Or How Fast Are Carbon Dioxide Levels Increasing Recently?
- Today’s rate of increase is more than 100 times faster than the increase that occurred when the last ice age ended.
You can view the rates of C02 increase, in terms of ppm per year, from 1959 until 2014, at https://www.co2.earth/co2-acceleration
The trend is that the ppm concentration rate is increasing with time.
1959 to 1964 started at 0.73 ppm, and 2005 to 2014 increased all the way up to 2.13 ppm.
What Is The Significance Of Current Carbon Dioxide Levels, & The Rate At Which Carbon Dioxide Levels Are Rising?
- … levels of carbon dioxide (CO2) in the atmosphere are higher than they have been at any time in the past 400,000 years
- If fossil-fuel burning [which is the main way human emit greenhouse gases into the air] continues at a business-as-usual rate, such that humanity exhausts the reserves over the next few centuries, CO2 [could] rise to levels of order of 1500 ppm. The atmosphere would then not return to pre-industrial levels even tens of thousands of years into the future.
- Pre industrial levels of C02 were around the 280 ppm mark.
- By burning fossil fuels we have launched atmospheric carbon dioxide levels beyond 400ppm – that’s an extra trillion tons of carbon dioxide in the air
- The last time the Earth saw these kinds of carbon dioxide levels was 3m years ago, well before Homo sapiens appeared, in what is called the “Mid Piacenzian Warm Period” of the Pliocene Epoch
- A true Hothouse Earth emerged when carbon dioxide levels reached something like 800ppm – about double those of today.
- Global annual mean CO2 concentration has increased by more than 45% since the start of the Industrial Revolution, from 280 ppm during the 10,000 years up to the mid-18th century to 410 ppm as of mid-2018.
- The present concentration is the highest in the last 800,000 and possibly even the last 20 million years. The increase has been caused by human activities, particularly the burning of fossil fuels and deforestation. This increase of CO2 and other long-lived greenhouse gases in Earth’s atmosphere has produced the current episode of global warming.
- About 30–40% of the CO2 released by humans into the atmosphere dissolves into oceans, rivers and lakes, which has produced ocean acidification
How Do Current Carbon Dioxide Levels Compare To Past Carbon Dioxide Levels – Are They Higher Or Lower?
Compared to the last 400,000 years, CO2 levels right now are higher than they have been.
But, going back millions, and hundreds of millions of years, there have been many times when CO2 levels were higher than they are now (much higher in fact).
The period when dinosaurs inhabited the earth is one example of this.
- For a 2009 study, published in the journal Science, scientists analyzed shells in deep sea sediments to estimate past CO2 levels, and found that CO2 levels have not been as high as they are now for at least the past 10 to 15 million years, during the Miocene epoch.
- The last time there was this much carbon dioxide (CO2) in the Earth’s atmosphere, modern humans didn’t exist. Megatoothed sharks prowled the oceans, the world’s seas were up to 100 feet higher than they are today, and the global average surface temperature was up to 11°F warmer than it is now.
Carbon Dioxide Levels On Earth Throughout History – Timeline
Last 1,000 years…
- There is a graph that shows both CO2 and methane levels over the past 1000 years – https://skepticalscience.com/climate-change-little-ice-age-medieval-warm-period-intermediate.htm
Last 400,000 years…
- There is a graph at https://climate.nasa.gov/evidence/ that shows CO2 levels for the last 400,000 years, and there’s a fairly predictable pattern of rising and falling CO2 ppm levels. At 1950, you can see the CO2 levels start to rise uncharacteristically to the levels they are today
Last 160, 2,000 and 800,000 years…
- There’s a graph at https://www.science.org.au/learning/general-audience/science-booklets-0/science-climate-change/2-how-has-climate-changed of the CO2 levels over these time periods
Last 400 million years…
- There is a graph at https://skepticalscience.com/climate-change-little-ice-age-medieval-warm-period-intermediate.htm, and it shows CO2 levels compared to today’s levels over the last 400 million years. It shows CO2 estimates from fossil soil carbonate, and all other proxies
Other CO2 level information:
- Can be found at https://en.wikipedia.org/wiki/Carbon_dioxide_in_Earth%27s_atmosphere#Measuring_ancient-Earth_carbon_dioxide_concentration
- Concentrations of CO2 in the atmosphere were as high as 4,000 parts per million (ppm) during the Cambrian period about 500 million years ago to as low as 180 ppm during the Quaternary glaciation of the last two million years.
Why Are We Still Worried About Current Day Carbon Dioxide Levels Today When Levels Were Higher In The Past?
There’s a few reasons.
- Sudden vs slow change…
- Life flourished in the Eocene, the Cretaceous and other times of high CO2 in the atmosphere because the greenhouse gasses were in balance with the carbon in the oceans and the weathering of rocks. Life, ocean chemistry, and atmospheric gasses had millions of years to adjust to those levels.
- … there have been several times in Earth’s past when Earth’s temperature jumped rapidly, in much the same way as they are doing today. Those times were caused by large and rapid greenhouse gas emissions, just like humans are causing today.
- Those rapid global warming events were almost always highly destructive for life, causing mass extinctions such as at the end of the Permian, Triassic, or even mid-Cambrian periods. The symptoms from those events (huge and rapid carbon emissions, a big rapid jump in global temperatures, rising sea levels, ocean acidification, widespread oxygen-starved zones in the oceans) are all happening today with human-caused climate change. The outcomes for life on Earth were often dire.
- There were different factors to consider in the past…
- Over the Earth’s history, there are times where atmospheric CO2 is higher than current levels.
- Does this contradict the warming effect of CO2? No, for one simple reason. CO2 is not the only driver of climate. To understand past climate, we need to include other forcings that drive climate.
- Atmospheric CO2 levels have reached spectacular values in the deep past, possibly topping over 5000 ppm in the late Ordovician around 440 million years ago. However, solar activity also falls as you go further back. In the early Phanerozoic, solar output was about 4% less than current levels.
- … When the sun is less active, the CO2-ice threshold is much higher.
- … So we see that comparisons of present day climate to periods 500 million years ago need to take into account that the sun was less active than now.
- While there have been past periods in Earth’s history when temperatures were warmer than they are now, the rate of change that is currently taking place is faster than most of the climate shifts that have occurred in the past, and therefore it will likely be more difficult to adapt to.
A Note About CO2 Levels Throughout History
The further you go back in time, the more disagreement and uncertainty there can be between scientists about what the estimated CO2 levels were at any one particular time.
Depending on what ancient records, ice cores, rock sediment samples etc. you are looking at – you might get a different idea of what the levels were.
An example of this is:
- Relevant to this dispute is the observation that Greenland ice cores often report higher and more variable CO2 values than similar measurements in Antarctica. However, the groups responsible for such measurements (e.g. H.J. Smith et al.) believe the variations in Greenland cores result from in situ decomposition of calcium carbonate dust found in the ice. When dust concentrations in Greenland cores are low, as they nearly always are in Antarctic cores, the researchers report good agreement between measurements of Antarctic and Greenland CO2 concentrations.
Climatecentral.org also mentions:
- The news that CO2 is near 400 ppm for the first time highlights a question that scientists have been investigating using a variety of methods: when was the last time that CO2 levels were this high, and what was the climate like back then?
- There is no single, agreed-upon answer to those questions as studies show a wide date range from between 800,000 to 15 million years ago. The most direct evidence comes from tiny bubbles of ancient air trapped in the vast ice sheets of Antarctica. By drilling for ice cores and analyzing the air bubbles, scientists have found that, at no point during at least the past 800,000 years have atmospheric CO2 levels been as high as they are now.