420ppm : Halfway to Hell
Filed under: Perpetually barreling towards a catastrophe
Welcome to Climate Matters, a weekly-ish newsletter on climate crisis written by me, Neelima Vallangi, a person who loves living on a beautiful and habitable planet.
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Yet another grim symbolic milestone has been crossed. Clues from peering into both the past & the future, confirms this bleak departure towards hell.
*Newly updated on May 9, 2022*
Since writing this post last June(2021), in astonishingly just within a year, the world went from a daily record high of 420ppm to a monthly record high of 420ppm. Atmospheric carbon dioxide concentration of 420ppm is unheard of, in the entirety of human evolution as a species. And even much before that. So hitting daily and monthly highs in such quick succession is alarming, and it also signals the arrival of an annual high of 420ppm as well(Currently, it is at 416.45 ppm for 2021).
Read the post below to understand the unprecedented nature of this level of atmospheric CO2 and what that means for us.
Before you wonder what’s the point of getting these depressing updates, remember that scalable, sustainable solutions come from policy and structural systemic changes. And what drives these huge societal changes is a sense of urgency and public pressure. That’s why, I tell you these things. So you can get invested, stay informed, understand the implications and then either work on appropriate solutions and/or demand an adequate solution from leaders based on our Common but Differentiated Responsibilities and Respective Capabilities. (there, I also threw in a major climate policy principle for you. ;) Read about it, it’s going to be super relevant in the coming days.)
This a long post, so I’m starting with a tl;dr (too long; didn’t read) version first
Here’s what happened:
Atmospheric carbon dioxide set a daily record high of
420ppm on 8th, April 2021422.06 ppm on April 26, 2022. And monthly average peaked at419ppm for May 2021420.02 ppm for April 2022.420 is halfway between preindustrial CO2 levels (280ppm) and CO2 doubling in the atmosphere(560ppm). That’s a 50% increase from pre-industrial levels.
(Alarmingly, it took almost 200 years for 25% increase in carbon dioxide levels from 280ppm in 1800s to reach 350ppm in late 1980s. But it took only 30 years for the next 25% increase to reach 420ppm in 2020s.)
Doubling of CO2 is the basis used by climate scientists to find out how the global temperature will alter in relation to changing carbon dioxide concentration in the atmosphere. Temperature rise per doubling of CO2 is called climate sensitivity.
As per latest studies, when the atmospheric CO2 doubles, the earth’s surface will warm between 2.6°C and 4.1°C.
So we’re halfway to at least 2.6°C of warming already. And it doesn’t help that at our current growth rate, we’re all set to see 560ppm in the next few decades, as early as 2080!
And the past climate records paint a terrible picture for what the scene was like when CO2 concentrations were as high as now. For starters, sea level was 78 feet higher than today.
So neither the past nor the future data is reassuring, meaning we need much stronger climate action. And faster!
To know the practical implications of this milestone and what all this means for us, you’ll have to read the full article below.
Right then, let’s understand all this properly?
On April 3rd 2021, the earth crossed a grim milestone when the daily atmospheric carbon dioxide concentration average crossed 420 parts per million(ppm) for the first time in millions of years.
And then, on April 8 2021 April 26 2022, the earth broke that record to set another record— a highest daily average of 421.36 ppm 422.06 ppm. Along with a monthly record high of 420.02 ppm for April 2022.
All of this is both super alarming and highly unusual.
Here’s why.
But first, what’s CO2 ppm and how does it vary over a year and over decades?
We now know there is a strong correspondence between CO2 concentrations in the atmosphere and global temperature. When CO2 concentration goes up, temperature also increases and when CO2 decreases, the temperature cools down. So it makes sense that we keep a close watch on carbon dioxide concentrations in the atmosphere because it predicts our future. And that’s exactly what CO2 ppm is. Here’s a brief primer on this measure.
The basics:
Atmospheric CO2 concentration has been fluctuating between 180 - 280ppm for the past 800,000 years at least.
Starting 1850s, which marks the beginning of the industrial revolution, atmospheric CO2 concentration starts shooting up and has only been steadily rising since.
Interactive: See this page to explore atmospheric Carbon Dioxide (CO2) levels, 1800–present.
In a year, the atmospheric CO2 concentration usually peaks in May and the lowest is observed during September - October. The average of the daily concentrations recorded over 365 days in a year is the CO2 concentration for that particular year.
Current state of things:
The atmospheric CO2 concentration for May 2021 averaged at 419 ppm.
For the year 2020, the annual mean is 414ppm at Mauna Loa Observatory.
While the weekly and monthly mean carbon dioxide concentrations should ideally go down over the coming months till Sep-Oct, the overall yearly average for 2021 will be higher than 2020’s for sure because we are not yet reducing emissions.
(If you’re wondering how this increase in CO2 concentration happened today, despite the pandemic lockdown and emissions reduction, read the very post that launched Climate Matters last June: Coronavirus lockdown did nothing for the apocalyptic dumpsterfire that'll be Climate Crisis.)
And these numbers not good, I explain why below.
Why does it matter if CO2 concentration reached 420 ppm on some days?
Because it is a grim reminder that we’re halfway to hell.
What hell exact am I talking about? Scientists use complex climate models to predict future warming corresponding to carbon dioxide levels in the atmosphere. Per doubling of CO2, we can expect a certain amount of warming. This is called climate sensitivity.
So let’s say when CO2 doubles for the first time, i.e. if we go to 560ppm from 280ppm, then we can expect X°C of warming. For the next X°C of warming, CO2 concentration needs to double again. Meaning, it has to go from 560ppm to 1120ppm. So on and so forth.
Latest update on the climate sensitivity is 2.6°C and 4.1°C per doubling of CO2. (Read more on Equilibrium Climate Sensitivity here)
And at our current emissions growth rate, the first doubling of atmospheric carbon dioxide isn’t too far away, just 5 five decades as per one estimate. Meaning, we can experience at least 2.6°C of warming and a maximum of 4.1°C in the long term. (long term because it takes thousands of years for the climate system to stabilise and adjust to the new carbon dioxide concentration in the atmosphere. These changes are certain but long drawn out.)
(In the short term, the current policies take us to 2.9°C warming by 2100.)
Seeing what the paltry current 1.2°C warming is manifesting as, it is not a stretch to assume both the immediate present and the long term future are hellscapes unless we drastically cut emissions.
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And so, the fact we’ve reached 50% of the way today to the doubling of carbon dioxide is a stark & worrisome reminder of our extremely slow & inadequate response to this accelerating planetary crisis.
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That’s one thing. But the more concerning consideration of 420ppm is the condition of the earth the last time atmospheric carbon dioxide was at these levels.
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So what picture does the past paint about a time when the earth had similar atmospheric composition?
Before we proceed, would you like to venture a guess how long ago CO2 concentration was this high in the past?
Not 10,000 years ago.
Not 800,000 years ago.
Not 2,000,000 years ago.
Not even 3,000,000 years ago.
It was 4,000,000 years ago.
That’s 4 million years before now.
To put all this in context:
Complex civilisations as we knew it started only 8000 - 6000 years ago.
Humans, all our direct ancestors today, migrated out of Africa only 40,000 years ago.
Homo Sapiens as a species evolved only 200,000-300,000 years ago.
To put this is in further context on the unimaginable scale of both the timeline & changes we caused:
If we repeat such time periods of 300,000 years each over which homo sapiens evolved 14 times, only then we’ll reach 4 millions years in the past when the atmospheric CO2 was at similar levels today. Things weren’t remotely conducive for thriving human societies like today then because sea levels were 24 meters(!!!) higher and temperature was 4°C higher than pre industrial levels.
We know all this from paleoclimate data, that is the weather and climate informations from the geological past. We don’t have direct measurements from the past but by using something called proxy data, scientists can reconstruct the past atmospheric & climatic conditions going all the way back upto hundreds of millions of years.
“The atmospheric burden of CO2 is now comparable to where it was during the Pliocene Climatic Optimum, between 4.1 and 4.5 million years ago, when CO2 was close to, or above 400 ppm. During that time, sea level was about 78 feet [25.7 meters] higher than today, the average temperature was 7 degrees Fahrenheit [4 degree Celsius] higher than in pre-industrial times, and studies indicate large forests occupied areas of the Arctic that are now tundra.” — National Oceanic and Atmospheric Administration Research
Paleoclimate temperature and CO2 records show us our grim future:
These are some stunning graphs that helped me understand the impossible magnitude of changes that are afoot in the Anthropocene, i.e. the age where humans have significantly altered the planet’s systems.
Scientists have recreated the temperature records of up to the last 540 million years and you can see the temperature fluctuations over the past many million years. For millions of years temperature visibly & slowly changed responding to the atmospheric carbon dioxide and other radiative forcings.
If you are unfamiliar with earth’s timeline history and terminology, here’s a primer.
Earth’s 4.5 billions year old history is measured in something called Geological Time Scale which includes four Eons made up of several Eras each. Each Era in turn is made up of several Periods, which are further divided into Epochs and Ages. We are currently in Holocene Epoch, which is part of Quaternary Period, which is part of Cenozoic Era, that is part of Phanerozoic Eon. With me so far? (See illustration). Holocene is the most recent interglacial warming phase after the last glacial period ended, approximately 11,650 calendar years before present (circa 1950s).
Then we enter Holocene about 12,000 years ago. You can see the temperature stabilised for thousands of years, during which period human civilisation started and thrived. And then you can see what happens in the last 100 or so years in the right end of the illustration, the observed and predicted temperature rise is so drastic that it is a line on the graph!
Next, we have predictions for future based on the past climates. Once again, the exceedingly drastic timeline of human caused climate change becomes apparent. 4/5th of the chart deals with 100,000 year and 1,000,000 year periods on the X-axis but the last section is the just 600 years overall and would you look at the temperature changes!!
In this paper, titled Pliocene and Eocene provide best analogs for near-future climates, the authors predict that we could go back to Pliocene and Eocene like climates in just 200 years from now, based on our high emission pathway. Of course, if we still reduce emissions according to the mid and low emissions pathways, then we won’t go into those utterly unfamiliar climates that existed 10-20 millions of years before present. But that also means we strictly need to achieve Paris Agreement targets.
At the moment, the carbon dioxide levels are as high as 4 million years ago, as in we are in mid Pliocene equivalent now. Look at the chart properly and remember, homo sapiens evolved only in mid-Pleistocene and human civilisations started only in Holocene.
Why haven’t the sea levels risen to 78 feet/24 meters if the CO2 levels are the same as Pliocene then?
Because of something called Climate Stabilisation.
The easiest way to explain this would be through this video below. Watch it, seems unrelated but I think you’ll understand climate stabilisation so much better after.
What happens at minute 1:48 is the climate equivalent of climate being finally stabilised. And everything that happens before is the process of stabilisation where several concurrent and consecutive processes have to happen to reach the final state of equilibrium. Of course, the endgame of climate stabilisation process won’t be a sudden event like the one pictured here but you get the gist, right?
So if we have to come back to climate stabilisation, the full effect of a particular level of carbon dioxide concentration in the atmosphere is perceptible only after CO2 concentration is stable and all feedbacks have completed. Climate feedbacks are ocean warming, then ice sheet melting, change in vegetation cover, water vapour concentration changes, cloud cover effects and other long terms processes that can be affected by warming. It takes hundreds to thousands of years for all these feedback processes to fully respond to the carbon dioxide increase. And that’s why even though we have CO2 levels never seen within human lifetime, we don’t see those extreme changes in environment yet. (Read more on Climate Stabilisation here)
But the most important point to remember here is that these changes are a matter of when, not if.
From 350 ppm to 450 ppm to 500 ppm: Shifting goalposts and continuing inaction
When the first IPCC report was released in 1990, the carbon dioxide concentration was a little over 350 ppm and in the years that followed, 350 ppm was considered an achievable and best target.
By the time Paris Agreement was signed 2015, we started considering 450 ppm or even 500 ppm, approximately corresponding to 1.5°C and 2°C warming, as the best target.
And today we are at 420 ppm already.
We keep crossing these dangerous milestones like it’s a random toll booth on the highway. Articles like these were written in 2016 when the earth crossed 400ppm as well. Today in 2021, we’re writing the same alarming articles as the earth records 420ppm.
It is depressing and infuriating to see this planetary crisis not being taken seriously enough, and that our leaders keep failing to meet targets and we keep shifting the goalposts hoping they’d act on this at least.
But knowing what the future holds, it is also imperative that we don’t give up the fight for a liveable planet.
What is the optimal carbon dioxide concentration anyway?
There’s no definitive answer to this. What we do know is that humans thrived in the Holocene, i.e. the last 12, 000 (11,700 to be precise) years where CO2 concentration and global surface temperature was conducive to large scale agricultural production, resource abundance, pleasant climates and population growth overall. So based on the past and the current conditions, we could say anywhere between 280ppm to 350ppm is the optimal carbon dioxide concentration for us to thrive.
There is this concept called the human climate niche, a small range of atmospheric and environmental conditions during which humans evolved, adapted and prospered. Two things to remember here are that 1. we can function efficiently and comfortably within this range and 2. we can be certain of climate, weather, seasons and other environmental conditions to effectively plan for future. Unfortunately, the human climate niche is no longer a certainty because our climate is changing fast and we have no way to know how our bodies or societies will respond to this change because none of our ancestors had to face conditions like this. So with that uncertainty in mind, I’d say it is in our absolute best interest to get it back to similar levels or slightly higher.
Read more on this at MIT’s Climate Portal - What is the ideal level of carbon dioxide in the atmosphere for human life?
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On a related note, I leave you with this cracking segment on The Newsroom, where an Environmental Protection Agency official, Richard Westbrook, goes off on TV dropping truth bombs, when the report on 400ppm is released. (All of it is true, except for the ending where we can and will have to do something to minimise the climate impacts)
Phew! That turned out to be unexpectedly long.
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