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Comment by brchr | Hacker News Reader

"CO2 levels higher": Would you mind sharing your source on this?

Here are the last 6,000 years [1] (it cuts off at 4713 BC because that happens to be the earliest timestamp available in Postgres). The source data from the NOAA are here [2] and you can see for yourself that we are something like 30% higher than the highest level of CO2 recorded in the last 800,000 years.

If you have a source that tells a different story, let me know.

[1] https://numer.al/noaa_data/figures/antarctic-ice-cores-revis...

[2] ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/antarctica2015co2composite.txt

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You just need to go back in time further than the ice age: https://en.wikipedia.org/wiki/Ice_age

"Outside these ages, the Earth seems to have been ice-free even in high latitudes."

If you want to maintain the status quo and not allow human impact on the climate, you can expect the glaciers to arrive sooner rather than later: https://en.wikipedia.org/wiki/Ice_age#/media/File:Vostok_Pet...

During the Devonian and Carboniferous time (~400 million years ago) Earth was like 20 degrees warmer and CO2 was really high.

That's correct. If memory serves, it's been >400 ppm quite a few times since.

The earth, and rich (though temporarily diminished) life on its surface will continue.

I suspect there will be a much smaller number of humans to enjoy it.

Okay, so we can say that:

1. CO2 is currently the highest it has ever been since human civilization has existed (10k years, roughly).

2. CO2 is currently the highest it has ever been since humans have existed (200k years, roughly).

3. CO2 is currently the highest it has ever been since primates have existed (50M years, roughly).

But for the sake of argument let’s say:

4. CO2 may not be the highest it has ever been since mammals have existed (200M years, roughly).

5. CO2 is not the highest it has ever been since multicellular life has existed on land (500M years, roughly).

Fair enough. Maybe 1-3 are less concerning to you than they are to me. When you say "the climate has been warmer in the past and CO2 levels higher" and are referring to a period prior to the existence of primates, it doesn't necessarily make me feel that much better. :) That said I’m nothing close to being expert in this stuff.

It’s interestingly difficult to think about time over so many orders of magnitude.

I like this xkcd's comic cosmic perspective:

http://xkcd.com/1732/

When put in this perspective it is hard to not be concerned about 1-3.

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