Comments on: Record heat for DC climate march… https://habitablezone.com/2017/04/29/record-heat-for-dc-climate-march/ Tue, 07 Apr 2026 19:18:10 -0700 hourly 1 http://wordpress.org/?v=3.3.1 By: RL https://habitablezone.com/2017/04/29/record-heat-for-dc-climate-march/#comment-38942 RL Sun, 30 Apr 2017 01:57:09 +0000 https://www.habitablezone.com/?p=63576#comment-38942 We have surpassed 410ppm CO2 concentration, the following was written when we passed 400ppm in 2013: <a href="http://www.climatecentral.org/news/the-last-time-co2-was-this-high-humans-didnt-exist-15938" target="_blank" rel="nofollow">http://www.climatecentral.org/news/the-last-time-co2-was-this-high-humans-didnt-exist-15938</a> <blockquote> The last time there was this much carbon dioxide (CO2) in the Earth's atmosphere, modern humans didn't exist. Megatoothed sharks prowled the oceans, the world's seas were up to 100 feet higher than they are today, and the global average surface temperature was up to 11°F warmer than it is now. As we near the record for the highest CO2 concentration in human history — 400 parts per million — climate scientists worry about where we were then, and where we're rapidly headed now. According to data gathered at the Mauna Loa Observatory in Hawaii, the 400 ppm mark may briefly be exceeded this month, when CO2 typically hits a seasonal peak in the Northern Hemisphere, although it is more likely to take a couple more years until it stays above that threshold, according to Ralph Keeling, a researcher at the Scripps Institute of Oceanography.</blockquote> We have surpassed 410ppm CO2 concentration, the following was written when we passed 400ppm in 2013:

http://www.climatecentral.org/news/the-last-time-co2-was-this-high-humans-didnt-exist-15938

The last time there was this much carbon dioxide (CO2) in the Earth’s atmosphere, modern humans didn’t exist. Megatoothed sharks prowled the oceans, the world’s seas were up to 100 feet higher than they are today, and the global average surface temperature was up to 11°F warmer than it is now.

As we near the record for the highest CO2 concentration in human history — 400 parts per million — climate scientists worry about where we were then, and where we’re rapidly headed now.

According to data gathered at the Mauna Loa Observatory in Hawaii, the 400 ppm mark may briefly be exceeded this month, when CO2 typically hits a seasonal peak in the Northern Hemisphere, although it is more likely to take a couple more years until it stays above that threshold, according to Ralph Keeling, a researcher at the Scripps Institute of Oceanography.

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