I don't think it will be that much (spoiler alert: I was wrong), because only a negligible amount of web traffic will be the headers themselves vs. web--pages a

I don't think it will be that much (spoiler alert: I was wrong), because only a negligible amount of web traffic will be the headers themselves vs. web--pages and streamed content. And the FLoC header itself will be a very small part of that header, maybe 40 bytes. Those 40 bytes could fit in a singular packet. So, at most, FLoC will add 1 packet per header. I don't know how many headers are sent total each day, but I remember reading that the average person visits 100 websites per day (including reloads). Out of 4 billion people who use the internet, we're talking about 400 Billion response headers per day. Assuming that each opt out of FLoC (a portion of this is Google, so that's unlikely), that means that an extra 400 Billion * 40 Bytes need to be sent. This is about 16 Trillion extra bytes that need to be sent (16E13). I've just checked, and it seems that the average Google Search is about 125kb, and I found that each releases approx. 7gCO2. So dividing this out, each kilobyte of traffic releases 0.056 grams of CO2. For each byte, that would be 0.000056 (5.6E-5) grams. Multiplying that out by the 16 Trillion extra bytes, you have 8.96 Million (896E7) grams of CO2, or an extra 8960 tons of CO2 per day. So, I was totally wrong. Jeez, that's a lot of CO2. But, my calculations were a badly-estimated, worst-case scenario. Also, since less websites will have third-party cookies as a result of this, we would have to subtract those now gone emissions. But, this is still a lot more CO2 than I expected, even if it was counteracted.