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Why do you think that current CO2 concentration levels are important for intelligent life? Slight adjustment in how body works can easily adapt organism to new

Why do you think that current CO2 concentration levels are important for intelligent life? Slight adjustment in how body works can easily adapt organism to new CO2 levels.

danieltillett 12y ago
I did explain it in my post, but maybe it was too short. Earth has been kept in the habitable temperature zone over the last 3.5 billion years through falling CO2 levels. Around 3.5 billion years ago the sun provided ~25% less energy than now and the CO2 levels were much higher. This is the green house effect. As the sun got brighter over time the level of CO2 in the atmosphere has fallen. For more on this see the slow carbon cycle [1]. The problem is that the level of CO2 in the atmosphere is getting very low (~0.2%). At this level plants are starved for CO2 - if it gets down to 0.01% then plants can't grow at all and the ecosystem needed to support the evolution of intelligent life would collapse. 1. http://earthobservatory.nasa.gov/Features/CarbonCycle/page2.php http://earthobservatory.nasa.gov/Features/CarbonCycle/page2....
- dennisgorelik 12y ago
  So some CO2 is needed for plants. It does not make certain CO2 levels a requirement for intelligent life. Change in temperature does not necessarily kill intelligent life either.
  - sampo 12y ago
    At least for the foreseeable future, we still need plants and natural ecosystems to survive on Earth.
  - danieltillett 12y ago
    Photosynthesis is required for the evolution of intelligent life. The point I was making is that intelligent life has evolved on Earth pretty close to the latest time possible.
- sampo 12y ago
  C4 photosynthesis is an adaptation to higher temperatures and lower atmospheric CO2. And C4 is a very recent innovation (25 to 32 million years ago, says Wikipedia). But yeah, I don't know if even the C4 plants could handle 0.01% ambient CO2.
  - danieltillett 12y ago
    Yes C4 photosynthesis is an adaption to falling CO2 levels in the atmosphere. It does come at a cost which is why in areas that are not water limited C4 plants have not out competed C3 plants.
- sampo 12y ago
  > CO2 in the atmosphere is getting very low (~0.2%). We are currently at about 400 ppm (parts-per-million), which would be 0.04%. http://co2now.org/ http://co2now.org/ About 20 000 years ago, the lowest was maybe ca. 200 ppm.

Why do you think that current CO2 concentration levels are important for intelligent life? Slight adjustment in how body works can easily adapt organism to new CO2 levels.

danieltillett 12y ago

I did explain it in my post, but maybe it was too short. Earth has been kept in the habitable temperature zone over the last 3.5 billion years through falling CO2 levels. Around 3.5 billion years ago the sun provided ~25% less energy than now and the CO2 levels were much higher. This is the green house effect. As the sun got brighter over time the level of CO2 in the atmosphere has fallen. For more on this see the slow carbon cycle [1]. The problem is that the level of CO2 in the atmosphere is getting very low (~0.2%). At this level plants are starved for CO2 - if it gets down to 0.01% then plants can't grow at all and the ecosystem needed to support the evolution of intelligent life would collapse. 1. http://earthobservatory.nasa.gov/Features/CarbonCycle/page2.php http://earthobservatory.nasa.gov/Features/CarbonCycle/page2....

dennisgorelik 12y ago
So some CO2 is needed for plants. It does not make certain CO2 levels a requirement for intelligent life. Change in temperature does not necessarily kill intelligent life either.
- sampo 12y ago
  At least for the foreseeable future, we still need plants and natural ecosystems to survive on Earth.
- danieltillett 12y ago
  Photosynthesis is required for the evolution of intelligent life. The point I was making is that intelligent life has evolved on Earth pretty close to the latest time possible.
sampo 12y ago
C4 photosynthesis is an adaptation to higher temperatures and lower atmospheric CO2. And C4 is a very recent innovation (25 to 32 million years ago, says Wikipedia). But yeah, I don't know if even the C4 plants could handle 0.01% ambient CO2.
- danieltillett 12y ago
  Yes C4 photosynthesis is an adaption to falling CO2 levels in the atmosphere. It does come at a cost which is why in areas that are not water limited C4 plants have not out competed C3 plants.
sampo 12y ago
> CO2 in the atmosphere is getting very low (~0.2%). We are currently at about 400 ppm (parts-per-million), which would be 0.04%. http://co2now.org/ http://co2now.org/ About 20 000 years ago, the lowest was maybe ca. 200 ppm.