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Comment by ppod | Hacker News Reader

I still haven't found convincing data on this. There is this very weird guardian article that makes claims about large effects but contains a series of figures that seem to show very small effects:

https://www.theguardian.com/environment/2020/mar/27/coronavi...

Am I interpreting it wrong?

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how is 20 to 50 % reduction "very small effects"?

As I interpret it, the charts show a comparison of the change between two periods in 2020, compared to the average change over the same two periods in the previous five years. I can't see much difference between the trends this year and the five-year-average (I suppose the average difference is due to seasonality).

I don't think the data has been published properly, as far as I can tell. A article [1] by York University itself is clearer on what they are saying. Look at the second figure here and note

> In the graphs below, the blue bars show the average level of pollution from late February through to late March, taken from 2015 and 2019. The red bars show the average level of pollution between the same dates this year.

You can easily see that PM2.5 has roughly halved in London.

[1] https://ncas.ac.uk/en/18-news/3057-air-pollution-falling-acr...

I realise this anecdotal, but as a Londoner living in Zone2, I can actually see and feel the difference in air quality. The skyline is far clearer on average, and I definitely notice myself breathing easier, and I do not have asthma or any other respiratory or even allergy issues.

It's badly presented, but it seems to show the difference of the current values to two different baselines (earlier this year, and a long-term average).

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