50 years measuring the cleanest air | Hacker News Reader

50 years measuring the cleanest air

csiro.au

24 pointsdefrost5 comments

It’s crazy to think that:

— middle-aged people alive today experienced a 35% increase in average ambient atmospheric carbon dioxide concentration within their lifetimes[0], and

— ambient atmospheric carbon dioxide concentration today has apparently never been this high since Miocene[1] (15 megayears ago). It blew past the last relative peak, from around 300 kiloyears ago, around World War I and Russian Revolution[2] and is skyrocketing since then.

This is not a hypothetical downstream effect from global warming or sea level rise, it’s what all of us breathe. When talking about indoor spaces, official recommendations are always to keep it as close to outdoor air as possible. However, “outdoor air” is a moving target: give it another 35% increase, and planet average will be reach 600 ppm. Meanwhile, 1000 ppm to be a safe limit[3] for round-the-clock exposure by an average human.

[0] https://www.climate.gov/news-features/understanding-climate/...

[1] https://pubmed.ncbi.nlm.nih.gov/10963587/

[2] https://nsidc.org/learn/ask-scientist/core-climate-history

[3] https://www.canada.ca/en/health-canada/services/publications...

I don't know why this angle isn't emphasized more. Pollution that is experienced personally is much more persuasive than the abstract idea of climate change.

For those looking to manage their indoor CO2 levels, I found videos by this HVAC expert pretty helpful: https://www.youtube.com/watch?v=CkGDN85I29U

There are caveats like:

- opening windows and doors may not change much if the air is not moving i.e. with fans

- and it may not be the worth the tradeoff of introducing outdoor irritants e.g. pollen

- indoor plants unfortunately do not make a big difference in CO2 levels

- consider focusing on more important facets of indoor air quality, like VOCs

Personally, the unnerving fact is not that ambient carbon dioxide is harmful in current concentrations (it almost certainly isn’t), but more that the average baseline concentration outdoors (which we have to live with and cannot really escape much) is rising seemingly drastically. It’s probably not going to be an issue in our lifetimes, but because it’s a global rise we can hardly even have a control group to test for any subtle health effects from a 100 ppm increase. Also, most advice and regulations about indoor concentrations rely on the fact that we don’t exclusively live indoors, we do get regularly exposed to baseline level outdoors, and rarely account for the fact that that level is rising.

I definitely should’ve reviewed that last paragraph one more time…

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