What is the highest co2 levels in earth history

The amount of carbon dioxide (CO2) in the atmosphere has hit a historic high, shooting up to levels not seen for 4 million years, the National Oceanic and Atmospheric Administration (NOAA) announced in a statement last week.

Scientists measured a concentration of 420.99 parts per million (ppm) at NOAA’s mountaintop observatory in Hawaii, an increase of 1.8 ppm since 2021, per the administration.

“Watching these incremental but persistent increases in CO2 year-to-year is much like watching a train barrel down the track towards you in slow motion. It’s terrifying,” University of Wisconsin-Madison climate scientist Andrea Dutton tells Seth Borenstein of the Associated Press. “If we stay on the track with a plan to jump out of the way at the last minute, we may die of heat stroke out on the tracks before it even gets to us.”

Around four million years ago, during the Pliocene Climatic Optimum, carbon dioxide levels were similar—close to or above 400 ppm, per NOAA. The earth was seven degrees hotter, ice caps at both the North and South Poles nearly completely melted and sea levels were 16 to 82 feet higher, high enough to submerge many major cities, the administration says. Paleoclimatologists can learn about past climates by looking at tree rings, ice cores, and mineral and element compositions in sediment core samples as well analyzing plant and animal remains. Particularly useful are forams and diatoms, shelled creatures that frequently record climate conditions in the compositions of their shells.

“Carbon dioxide is at levels our species has never experienced before,” Pieter Tans, senior scientist with NOAA’s Global Monitoring Laboratory says in the statement. “We have known about this for half a century, and have failed to do anything meaningful about it. What’s it going to take for us to wake up?”

From analysis of gas composition in ice core samples, scientists can tell that for almost 6,000 years of human history before the Industrial Revolution of the 18th and 19th centuries, carbon dioxide levels stayed consistently around 280 ppm. The advent of mass industry during the Industrial Revolution spurred emissions on, particularly from burning fossil fuels, especially coal and oil.

But carbon emissions from human activities have increased rapidly. Last year, 36.3 billion tons of global energy-related carbon dioxide were released, the highest ever recorded, and carbon emissions from the use of coal reached an all-time high of 15.3 billion tons.

According to the EPA, the three biggest sources of carbon emission worldwide are the transportation industry (27% of emissions in 2020), the production of electricity from all sources (25%, with fossil fuels making up 60% of this share), and general industrial activity in general, like the production of raw industrial materials (24%).

Now global temperatures are about 2 degrees Fahrenheit higher than before the Industrial Revolution, writes Henry Fountain for the New York Times.

Earlier this year, an Intergovernmental Panel on Climate Change (IPCC) report warned that rapid and deep cuts to greenhouse gas emissions are needed to hit the goal of keeping global warming at only 1.5 degrees Celsius (or about 2.7 degrees Fahrenheit). This was another in a series of government and non-profit reports on the devastating effects of human-induced climate change on various facets of the planet, including Earth’s water supply and biodiversity loss.

Overall human carbon dioxide? emissions must be reduced by 43 percent by 2030 and 84 percent by 2050. By 2050, global coal use must drop by 95 percent compared to 2019.

The effects of human emissions on climate have been discussed by international organizations for decades—the first UN meeting on climate took place all the way back in 1972, yet unified action has been difficult to come by.

“It’s depressing that we’ve lacked the collective will power to slow the relentless rise in CO2,” says Ralph Keeling, a geochemist who runs CO2 measurements for the Scripps Institution of Oceanography in Hawaii, in a statement. “Fossil-fuel use may no longer be accelerating, but we are still racing at top speed towards a global catastrophe.”

Margaret Osborne | | READ MORE

Margaret Osborne is a freelance journalist based in the southwestern U.S. Her work has appeared in the Sag Harbor Express and has aired on WSHU Public Radio.

In the late 1950s, Roger Revelle, an American oceanographer based at the Scripps Institution of Oceanography in La Jolla, California began to ring the alarm bells over the amount of CO2 being emitted into the atmosphere. Revelle was very concerned about the greenhouse effect from this emission and was cautious because the carbon cycle was not then well understood. So, he decided that it would be wise to begin monitoring atmospheric concentrations of CO2. In the late 1950s, Revelle and a colleague, Charles Keeling, began monitoring atmospheric CO2 at an observatory on Mauna Loa, on the big island of Hawaii. Mauna Loa was chosen because its elevation and location away from industrial centers made it as close to a global signal as any other location. The record from Mauna Loa, one of the most classic plots in all of science, shown in the figure below, is a dramatic sign of global change that captured the attention of the whole world because it shows that this "experiment" we are conducting is apparently having a significant effect on the global carbon cycle. The climatological consequences of this change are potentially of great importance to the future of the global population. The CO2 concentration recently crossed the 400 ppm mark for the first time in millions of years! In 2022, the yearly average was 420 ppm (check that number with the curve below!).

The record of CO2 measured at Mauna Loa, Hawaii shows seasonal cycles superimposed on a longer-term rise in the yearly average (black line). The seasonal cycles are related to seasonal variations in photosynthesis and soil respiration in the Northern Hemisphere, where most of the land mass is located at present. The long-term trend is related to the addition of CO2 to the atmosphere through the combustion of fossil fuels.

Credit: NOAA

As the Mauna Loa record and others like it from around the world accumulated, a diverse group of scientists began to appreciate Revelle's concern that we really did not know too much about the global carbon cycle that ultimately regulates how much of our CO2 emissions stay in the atmosphere.

The importance of present-day changes in the carbon cycle, and the potential implications for climate change became much more apparent when scientists began to get results from studies of gas bubbles trapped in glacial ice. As we learned in Module 1, the bubbles are effectively samples of ancient atmospheres, and we can measure the concentration of CO2 and other trace gases like methane in these bubbles, and then by counting the annual layers preserved in glacial ice, we can date these atmospheric samples, providing a record of how CO2 changed over time in the past. The figure below shows the results of some of the ice core studies relevant for the recent past -- back to the year 900 A.D.

The recent history of atmospheric CO2, derived from the Mauna Loa observations back to 1958, and ice core data back to 900, shows a dramatic increase beginning in the late 1800s, at the onset of the Industrial Revolution. At the same time, the carbon isotope composition (δ13C is the ratio of 13C to 12C in atmospheric CO2) of the atmosphere declines, as would be expected from the combustion of fossil fuels, which have low values of δ13C. The inset shows a more detailed look at the last 150 years, where we can see that the rise in CO2 coincides with the rise in the burning of fossil fuels.

Credit: David Bice © Penn State University is licensed under CC BY-NC-SA 4.0

The striking feature of these data is that there is an exponential rise in atmospheric CO2 (and methane, another greenhouse gas) that connects with the more recent Mauna Loa record to produce a rather frightening trend. Also shown in the above figure is the record of fossil fuel emissions from around the world, which show a very similar exponential trend. Notice that these two data sets show an exponential rise that seems to begin at about the same time. What does this mean? Does it mean that there is a cause-and-effect relationship between emissions of CO2 and atmospheric CO2 levels? Although we should remember that science cannot prove things to be true beyond all doubt, it is highly likely that there is a cause-and-effect relationship -- it would be an extremely bizarre coincidence if the observed rise in atmospheric CO2 and the emissions of CO2 were unrelated.

How serious is our modification of the natural carbon cycle? Here, we need a slightly longer perspective from which to view our recent changes, so we return to the records from ice cores and look deeper and further back in time than we did in the figure we have been examining.

The record of atmospheric CO2 over the last 400,000 years shows that the recent rise in CO2 is unlike anything we’ve seen in the past 400 kyr both in terms of the rate of increase and the levels to which it is rising. Before this recent rise, CO2 fluctuated by about 80 ppm in connection with the ice ages (which as you can see have a regularity to their timing); this pattern has clearly been interrupted by the recent trend. The data shown here come from a variety of ice cores (blue, green, red, and cyan) and the Mauna Loa observatory (black).

Credit: Robert A. Rohde (original PNG), User: Jklamo (SVG conversion) [CC BY-SA 3.0]

In addition to providing a record of the past concentration of CO2 in the atmosphere, as we learned in Module 1, the ice cores also give us a temperature record. By studying the ratios of stable isotopes of oxygen that make up the glacial ice, we can estimate the temperature (in the region of the ice) at the time the snow fell (glacial ice is formed by the compression of snow as it gets buried to greater and greater depths). From these data, shown in the figure below, we can see the natural variations in atmospheric CO2 and temperature that have occurred over the past 160,000 years (160 kyr).

Data from the Vostok (Antarctica) ice core for the past 160 kyr show the relationship between variations in heat-trapping gases CO2 (carbon dioxide) and CH4 (methane) concentrations in parts per million (ppm) and parts per billion (ppb) and the temperature at Vostok. Note that each curve has its own scale for the vertical axis, but they all share the same time scale. The dashed blue line at the end shows the very recent rise in CO2 to the present day value of about 410 ppm, indicated by the arrow. The gas concentrations come from tiny bubbles trapped in the ice as it forms near the surface, while the temperature variations come from studying isotopes of oxygen and hydrogen in the ice itself. The ice cores thus provide us with an exceptional picture of atmospheric gas concentrations in the past and their relationship with temperature.

Credit: David Bice © Penn State University is licensed under CC BY-NC-SA 4.0

In fact, looking at this much longer span of time enables us to clearly see that the present CO2 concentration of the atmosphere is unprecedented in the last several hundreds of thousands of years. As geoscientists, we are interested in more than just the last few hundred kiloyears, and so we look back into the past using sediment cores retrieved from the deep sea. Geochemists studying these sediments have been able to reconstruct the approximate concentration of CO2 in the atmosphere and the sea surface temperature (SST).

The longer history of atmospheric CO2 as reconstructed from studies of deep-sea sediments. In the upper right, the blue region represents the upper and lower estimates back through time — you can see that it is difficult to be too precise going back this far in time — and you can see that the last time the midpoint of these estimates rose above the current level was around 2.5 Myr ago. This was a time when there was far less ice on Earth; the Arctic was apparently 15 to 20°C warmer than it is today, and sea level was about 20 meters higher than the present. As we go further back in time, we see that the atmospheric CO2 concentration rises to very high levels. The Earth was a very different place before about 30 Myr ago — sea level was perhaps 100 m higher and there was practically no ice on Earth.

To find atmospheric CO2 levels equivalent to the present, we have to go back 2.5 million years. This means that, to the extent that the state of the carbon cycle is closely linked to the condition of the global climate, we are pushing the system toward a climate that has not occurred any time within the last several million years -- not something to be taken lightly.

The farther back in time we go, the more difficult it is to figure out how CO2 concentrations have changed, but that has not stopped some from attempting:

The history of atmospheric CO2 over the last 550 Ma, based on modeling, shows extremely high levels about 100 Ma (million years ago) and before 350 Ma. Note that there are huge uncertainties associated with these estimates, but the mid-range of the estimates suggests that CO2 levels were very high during this time period. Interestingly, these periods of high CO2 more or less coincide with periods of high sea level as can be seen in the lower panel.

One thing that is clear is that further back in time, CO2 levels have been much, much higher, and the average global temperatures have also been much higher. Why does the CO2 concentration change so much? This is a big question whose answer involves many factors, but consider two that are relevant to what we'll learn about in this module. Photosynthesis only started in the Silurian (S on the timescale in the figure above), and photosynthesis is a major sink or absorber of atmospheric CO2. Sea level was much higher during the two big peaks in CO2 — this leaves less room for photosynthesis and it also decreases the planet's albedo, making it warmer. A warmer ocean cannot absorb atmospheric CO2 and instead, it releases it to the atmosphere.

In conclusion, from this brief look at the record of fossil fuel emissions and atmospheric CO2 concentrations, it is clear that we have cause for concern about the effects of the global CO2 "experiment". Because of this concern, there is a tremendous effort underway to better understand the global carbon cycle. In the remainder of this module, we will explore the global carbon cycle by first examining the components and processes involved and then by constructing and experimenting with a variety of models. The models will be relevant to the dynamics of the carbon cycle over a period of several hundred years -- these will enable us to explore a variety of questions about how the system will behave in our lifetimes and a bit beyond.

What is the highest historical CO2 level in the atmosphere?

The most distant period in time for which we have estimated CO2 levels is around the Ordovician period, 500 million years ago. At the time, atmospheric CO2 concentration was at a whopping 3000 to 9000 ppm!

What is the highest concentration of CO2 in the past 650000 years?

After searching ice spanning the period of 390,000-650,000 years before present, Stocker's team has discovered that carbon dioxide levels in the atmosphere did not exceed 290 parts per million during that time. Today, that figure is around 375 parts per million.