Comments on: Putting the 400 ppm CO2 thing in perspective

By: Chris Wiegard

Chris Wiegard — Sat, 11 May 2013 16:01:54 +0000

The biosphere breathes in and out on a yearly basis- green plants absorb CO2 in the northern hemisphere in the global summer, Then give some back during winter. I believe the overall increase in atmospheric CO2 is something like 2 ppm per year now, correct? So living humans will probably never again in our lifetimes ever see a CO2 reading of, for example, 395 ppm. before we can reverse the rise of atmospheric CO2, we must first stop the Rise. As regards coastal sea level prospects for the 22nd century, this is terrifying.

By: Sadiq

Sadiq — Sun, 05 May 2013 06:16:13 +0000

This 400 ppm milestone underscores our duty to pay more attention to first world problems that mildly inconvenience certain women here.

By: Climate Post: May 2, 2013 : Living Green Magazine

Climate Post: May 2, 2013 : Living Green Magazine — Fri, 03 May 2013 13:27:55 +0000

[…] been recorded at the Mauna Loa Observatory in Hawaii, but they tend to fluctuate hourly. The milestone is significant because it illustrates how dramatically humans have altered the atmosphere in a few generations, […]

By: U.S. Oil Reserves Higher Than Previously Thought – News Watch

U.S. Oil Reserves Higher Than Previously Thought – News Watch — Thu, 02 May 2013 20:27:50 +0000

By: Lyle

Lyle — Wed, 01 May 2013 20:04:03 +0000

Actually the 280/300 is taken during a period when at least a part of the earth is ice covered. It would be interesting to know what the readings where during the last (Wisconsin, Illinoian) interglacial. Also interesting to know what the reading might have been during the time of the roman empire. Its clear if you go back before the Pleistocene the readings were significantly higher than 280.
The average of the last 3 million years includes a lot of periods of serious continental glaciers.

By: Greg Laden

Greg Laden — Wed, 01 May 2013 13:44:51 +0000

Yes, with natural variation up and down of ten or so either way over the last thousands of years; 300 is a conservative estimate. 280 may well be a more accurate baseline, but it then includes (probably) natural variation. That’s fine, but picking 300 as the baseline allows the statement that these 100 ppm are human release of fossil C to be fairly accurate.

By: Desertphile

Desertphile — Wed, 01 May 2013 13:21:39 +0000

Average ppmv for the past 3,000,000 years was 283.

By: Ed Davies

Ed Davies — Wed, 01 May 2013 09:14:28 +0000

Re the first sentence: I thought the generally accepted pre-industrial level of CO? was about 280 ppm so a bit less, rather than a bit more, than 300 ppm. Or, are you thinking of another baseline?

By: Richard Kowalski

Richard Kowalski — Wed, 01 May 2013 02:24:59 +0000

300 to 400 ppm is a 33% increase, not 25%