The era of accelerated CO₂

15 min readMar 3, 2023

November 13th, 1946, was a fantastic day for Irving Langmuir. Even though the Chemist Langmuir had received a Nobel Prize in 1932, the discovery of this day in November indeed was more groundbreaking. Or so he thought.

Earlier that day, Langmuir had sent his assistant Vincent Schaefer 14.000 feet (approximately 4,250 meters or about half the height of Mount Everest) up in the sky in a small prop plane that lifted from Schenectady airport, near Albany, NY. Schaefer was to seed a cloud with pellets of dry ice to make it rain. Dry ice is essentially frozen CO₂, and this substance is used in movies to produce mist without producing any moisture.

In earlier experiments using an open-top freezer, Schaefer discovered that water crystals would form when adding dry ice to the freezer. The water crystals did not develop without the dry ice, even though the temperature inside the freezer measured -9 degrees Fahrenheit (-23 Celsius). Langmuir and Schaefer had ruled out any chemical reactions as a cause for this effect. Their theory was that it was simply the super cold temperature of below -100 degrees Fahrenheit (-73 Celsius) that caused the water in the air to form crystals.

According to James Pollard Espy’s general theory of cloud formation, as vaporized water rises to higher altitudes, it cools down and condenses into droplets of liquid water. These droplets are what we see as clouds. The droplets are so tiny that their weight is less than the buoyant force of the atmosphere surrounding the droplets. Only once the droplets surpass a critical mass will they start to fall as rain, snow, or hail. Larger droplets will form when the water vapor has something to cling to, such as a bit of dry ice or some chemical like silver iodide.

Back to Langmuir, on November 13th, 1946, he succeeded in controlling the weather. After seeding a cloud with dry ice, the cloud acted like a tormented animal, writhing, and moving in unnatural ways; soon after, it started to rain. He had become the master of the weather.

Fueled by this success, Langmuir received funding for project Cirrus (1), which aimed at eliminating the risk that hurricanes pose to people. Langmuir would seed a hurricane with dry ice above the ocean and thus weaken it to no longer pose any danger. On October 13th, 1947, the day had come for the experiment on the perfect “storm”. King, a category two hurricane, moving towards the open Atlantic Ocean in a North Easterly direction. A Boeing B-17 “Flying Fortress” dropped 80 Kg (176 lb.) of dry ice into the cyclone King. What happened afterward was a shock to everyone involved in the project. King grew in strength, took an impossible 130-degree turn, and headed towards Savannah, Georgia, where it caused millions of dollars’ worth of damages (2).

Later research concluded that the turn most likely was not caused by project Cirrus. Similar studies furthermore concluded that seeding clouds would not cause additional rain, that we cannot manipulate hurricanes with the proposed methods, and that the complexity of atmospheric processes is too high to accurately predict the results of such experiments.

Humanities’ dream to control the weather remains, and since Langmuir lived, a lot has happened. We have become increasingly adept at predicting our weather conditions. The sooner in the future, the weather predictions lie, the more accurate these are. However, even in our times, the accuracy of our predictions has its limitations. In the flooding in Germany during July 2021, meteorologists were aware of the danger of heavy rain. However, the meteorological models could not accurately pinpoint the exact location and time for the heavy rain. Predicting climate change over long periods has even more considerable complexity.

Maybe we should see this story as a warning when meddling with our environment. Especially geoengineering technologies are connected to significant uncertainties regarding side effects. In the end, geoengineering might solve one problem but aggravate other aspects of our living environment. The atmosphere and the processes around it are simply too complicated to comprehend fully. Therefore, we should apply the precautionary principle before using any geoengineering technologies.

Climate models

At the heart of climate science lie highly advanced computational models that are incredibly complex and vary in the number of variables taken into account. Reductively speaking, though, climate models use information from previous and present times to predict the future.

The models consider data from historical weather records, such as satellite measurements, sea surface temperatures, wind speeds, cloud cover, and other parameters. They also apply socio-economic scenarios that forecast our energy consumption. This latter element plays a critical role in climate forecasting, as our increasing reliance on fossil fuels over the last 150 years has seen soaring CO₂ emissions that, in turn, have driven a rise in temperatures.

One of the first prominent climate models came from John Sawyer in 1972 (4). Sawyer hypothesized that between 1969 and 2000, the concentration of CO₂ in the atmosphere would increase by 25%, and the world would warm by 0.6C (1.08 F) degrees. This model forecasted climate development fairly accurately for 30 years. Sawyer’s model is also one of the very earliest to argue for the notion of climate sensitivity — a term referring to how much long-term warming will occur per doubling of atmospheric CO₂ levels.

Sawyer argued for 2.4 degrees warming per CO₂ doubling — a little less than the 3 degrees estimated by the Intergovernmental Panel on Climate Change (IPCC) today. His estimation of atmospheric CO₂ concentration of 375–400 ppm by the year 2000 nearly matched the recorded levels of 370 ppm.

Two Years later, in 1975, Wally Broecker published his climate model, which concerned Earth’s temperature connected to a rapid increase in atmospheric CO₂ (5). Broecker was the first to project future temperatures due to global warming. Like Sawyer, Broecker also used an equilibrium climate sensitivity of 2.4 C (4.32F) per doubling of CO₂.

His forecasting of rising CO₂ emissions and his calculations and predictions of warming temperatures remained relatively accurate until the year 2000, after which the predictions overestimate CO₂ levels somewhat.

A pertinent quote from his introduction to the report resonates today. A climate future driven by the powerful force of CO₂ emissions, when Broecker stated that “a strong case can be made that the present cooling trend will, within a decade or so, give way to a pronounced warming induced by carbon dioxide.” Published when scientists believed a modest cooling of the Earth was taking place, Broecker points towards the opposite.

In 1990, the IPCC published its first climate forecast report (6), with subsequent updates in 1995, 2001, 2007, 2013, and the latest one in 2021. The 2013 IPCC report also included a first assessment report, which uses a more complex climate model.

This model introduced a new set of future greenhouse gas concentration scenarios, known as the Representative Concentration Pathways (RCPs). The pathways predict different climate futures, and all are deemed possible depending on the volume of greenhouse gases emitted in the years to come.

While all of the above models predict either a slightly lower or higher increase in temperatures vs. observations, they all forecast levels of CO₂ reasonably close to the subsequently recorded measurements. Regarding the temperatures, the subsequent measurements had a strong tendency to follow the highest temperature predictions.

The calculations used in these models and forecasts use the increasing amount of CO₂ in the atmosphere over time. As Broecker predicted over 40 years ago, the world is witnessing pronounced warming induced by carbon dioxide. Our growing consumption of fossil fuels correlates very strongly with the rise in atmospheric CO₂ that we can measure. In other words, the global warming that in the last 50 years has been recorded and tracked on Earth correlates with the increase in atmospheric CO₂.

The models used in the past have given us an insight into how good we were at predicting our current climate. We now stand before a climate future we anticipate with excitement, fear, uncertainty, confidence, worry, or hope, depending on our views and beliefs.

In the IPCC’s 5th Assessment Report and onwards, these possible future simulations are called the Representative Concentration Pathways — the RCPs — that predict different climate futures.

The RCP pathways both consider climate sensitivity — how temperatures are affected by increased concentrations of CO₂ in the atmosphere — and predict the quantity of climate gas emissions, using models, like socio-economic structures, to simulate different future scenarios.

Considering some of these different RCP scenarios gives us insight into various possible futures. The IPCC has outlined trajectories for different development paths until 2100, and we can choose what model we deem most likely.

The RCP2.6 is a scenario that most likely will keep the global temperature rise below 3.6 degrees Fahrenheit (2 C) by the year 2100. It requires a decline in CO₂ emissions by 2020, a deadline already passed, and CO₂ emissions to hit zero by 2100.

The RCP4.5, predicts a global temperature rise between 3.6 and 5.4degrees Fahrenheit (2 and 3 C) by 2100. This scenario predicts the peak of CO₂ emissions in 2040, followed by a reduction to 50% in the year 2100, compared to 2050 levels.

The RCP8.5 considers a scenario where emissions continue to rise throughout the 21st century. This model predicts a global temperature rise of 7.75 degrees Fahrenheit (4.3 C) in 2100.

Central to considering these scenarios and all climate models of today is the notion of the carbon-cycle feedback and the uncertainty this phenomenon brings to the projections. Around 50% of the CO₂ emitted by humans today remains in the atmosphere, and oceans and land absorb the last 50%. However, this cycle will change with increased temperatures, as warming will reduce the amount of CO₂ that the ocean absorbs (7).

The expectation is that global warming will weaken the carbon cycle, and more CO₂ emissions will remain in the atmosphere. Higher temperatures will furthermore release CO₂ previously locked into the soil. Other likely fallouts from a temperature rise are the acceleration of tree death and the likelihood of wildfires, while thawing permafrost could also release stored CO₂.

Climate scientists debate the RCP8.5 pathway; some consider it very unlikely with the green changes globally implemented. Others describe it as unlikely but plausible, as its forecast is, in fact, consistent with the current pace of global emissions. Other scientists argue that the scenario underestimates future concentrations of atmospheric carbon if we continue the business-as-usual path.

The debate about the uncertainty and strength regarding the carbon-cycle feedback shows the importance of considering the RCP8.5 predictions. Maybe it is not just as a worst-case, but indeed as a possible future scenario.

Fast forward to 2100, each RCP scenario projects a rise by 2100 to respectively.

1.6–4.1 degrees Fahrenheit (0.9–2.3C) with CO₂ levels at 420 ppm (RCP 2.6);

3–5,75 degrees Fahrenheit (1.7–3.2C) with CO₂ levels at 540 ppm (RCP4.5);

3.6–6.6 degrees Fahrenheit (2.0–3.7C) with CO₂ levels at 660–750 ppm (RCP6);

and 5.7–9.7 degrees Fahrenheit (3.2–5.4C) with CO₂ levels at 1000–1200 ppm (RCP8.5)

When extending the RCP scenarios and trajectories further into the future, all the way until the year 2300, they forecast our dream scenario of RCP2.5 only to decrease CO₂ levels to 360ppm. Furthermore, the best-case scenario requires a carbon-negative pathway where we stop releasing CO₂ into the atmosphere and at the same time remove CO₂ from the atmosphere.

At the other end of the scale, the RCP8.5 projects CO₂ concentrations to reach around 2,000 ppm in 2250, nearly seven times the pre-industrial level!

Some may take comfort in knowing that the Earth has been at such CO₂ concentration levels before. The year 2100 forecast of 1,000 ppm having last been recorded some 50 million years ago.

We should perhaps pause, though, to consider that these levels existed long before we walked the Earth and that they were due to changes that took place over millions of years. The current increase of atmospheric CO₂, potentially taking us on the path to reach 1,000 ppm, is driven by our fossil fuel consumption and taking place over a handful of decades rather than millions of years.

We base these CO₂ predictions on data gathered for climate model purposes. The models pay great attention to predicting future emissions and CO₂ levels linked to global warming.

For the climate models, however, atmospheric CO₂ acts as an intermediate step to predict future temperatures. Global warming remains the central concern in our recordings and predictions of climate change; Melting ice caps and increased sea levels are the disturbing and essential images we hold in our mind’s eye when we discuss global warming.

CO₂ concentration in the atmosphere is an essential and critical tool to predict and prevent these scenarios, but what seems to be missing from the equation is the direct impact rising atmospheric CO₂ may have on life on Earth.

At the other end of the scale, the RCP8.5 projects CO₂ concentrations to reach around 2,000 ppm in 2250, nearly seven times the pre-industrial level!

Some may take comfort in knowing that the Earth has been at such CO₂ concentration levels before. The year 2100 forecast of 1,000 ppm having last been recorded some 50 million years ago.

We base these CO₂ predictions on data gathered for climate model purposes. The models pay great attention to predicting future emissions and CO₂ levels linked to global warming.

Impact of CO₂ on life in the oceans

Below the surface, in the oceans, critical changes are happening that witness the direct effects of increasing CO₂ levels on life on Earth. The annual increase in CO₂ levels has risen 100 times faster over the past 60 years than the natural increases we see from ice core data — the most recent occurring at the end of the last ice age 11,000–17,000 years ago. And this change is making itself known in our oceans.

Water absorbs vast amounts of CO₂. The rise in CO₂ levels has caused increased carbon absorption by the oceans. Records show that the pH levels of oceans’ surface water have dropped, from 8.21 to 8.10. The drop in pH levels may appear insignificant, but a 1 unit drop causes a tenfold increase in acidity. This means that a drop from 8.21 to 8.10 has caused a 30% increase in acidity in oceans’ surface water (9). A continued increase in CO₂ emissions predicts a further decrease in pH levels from 8.1 to 7.8. Scientists do not yet know the consequences of this potential pH lowering and further increase of 120% in acidity (10).

For now, then, let’s concern ourselves with the consequences of our current 30% increase in acidity and dive beneath the ocean surface. Here you find an ocean snail bearing a simple spiral shape — a seashell. Gather it from the beach and study the smoothly contoured ridges. What rests in your palm is a healthy ocean snail. Or perhaps, if you look closely, you may instead be holding something that is becoming increasingly common; a cloudy and ragged shell, pockmarked with weak spots. This damaged ocean shell is the embodiment of ocean acidification (11).

Ocean snails are protected by their shell, consisting of calcium carbonate — a chemical compound that is also essential in building and strengthening the bones in our bodies. Normal ocean conditions provide enough calcium carbonate to form a healthy protective shell for the snail.

With the increase of atmospheric CO₂, and the increased CO₂ dissolved in the ocean, more bicarbonate will form and thus use up more carbonate in the water, leaving shell-building organisms with less shell-building calcium carbonate.

It may sound like a small and insignificant change; a small body in a vast body of water, a small detail to a small spiral-shaped life form. But the calcium carbonate shortage is affecting everything from our ocean snails to the lives of coral reefs. The seawater’s increased acidity means less calcium carbonate stored, and coral, too, need calcium carbonate to build their protective shells and exoskeletons. Without this element, shells grow slowly and will weaken.

A normally protective shell made thin, fragile, and transparent by acidification (12)

Ocean acidification may affect the growth of a single coral, but we know that these organisms live in colonies. Coral reefs with breakable, slow-growing corals erode more quickly than they accrete, and the consequence is that they die out. Together, corals produce reefs that provide housing and food for other creatures, and they provide a place of thriving biodiversity. Coral reefs are some of the most diverse ecosystems in the world, and the disappearance of such ‘homes’ could cause the extinction of entire groups of species below water.

Below the same waters, other processes also bear witness to the impact of rising CO₂. Warming oceans, nitrogen deposition from the burning of fossil fuels, and the release of waste products into the seas are causing a phenomenon known as ocean deoxygenation.

The increase of atmospheric CO₂ drives up ocean surface temperatures, and as oxygen is less soluble in warmer waters, a decrease in O₂ levels is occurring. This pernicious combination reduces the oxygen content in the ocean, and scientists have recorded a 2% decrease in the oceans’ O₂ levels between 1960 and 2000.

A change in oxygen levels to a body that represents 97% of the physical habitable space on the planet (13) will have a fundamental impact. Decreasing ocean oxygen levels could lead to the disappearance of higher trophic level organisms (organisms higher on the food chain) and change the entire food web structure. The full extent of its effect on the planet and our lives is unknown. Scientists, however, believe that the change will result in a decrease in biodiversity, a shift in the distribution of species, a reduction in fishery resources, and expanding algal blooms. All CO₂-induced consequences, some experts argue, will disrupt the food provisioning ecosystem services of the ocean.

Above the surface, life also shows the effects of increased atmospheric CO₂ with crop yields and plant biodiversity being affected. Higher CO₂ may cause increased growth in plant species. Still, the so-called ‘greening’ effect means that slower-growing trees, for instance, will give way to faster-growing species. Above ground, ecosystems could ultimately also face significant radical changes (14).

While the climate- debate -and models pay great attention to the undeniable rising CO₂ levels, a focus on this increase and its direct effects on life forms here on Earth is mainly absent. Widening our focus may help us understand the role CO₂ plays in the life of our planet. CO₂ is not only a cause of soaring temperatures. CO₂ also directly affects the very fabric of our world, living creatures, from snails to corals and perhaps even us?

We may be complex and highly evolved creatures. Still, we rely on narrow lines in rocks and fine sedimentary particles to learn about our beginnings, and it is within tiny bubbles of air that hold vast amounts of information about our climate past. Similarly, the smallest of ocean shells, the strength of a single coral, and the change in the vegetation growth of a tree may hold vital information about our climate future and the direct impact increased atmospheric CO₂ has on all the many, varied, and extraordinary forms cohabiting the Earth.

Book

This is the fourth chapter of my book “Atmosphere, CO₂ on my mind”. You can find more information and references on my website.

The era of accelerated CO₂

Climate models

Impact of CO₂ on life in the oceans

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Written by Daniel Lux