The view from from Skeptical Science:
Showing posts with label CO2. Show all posts
Showing posts with label CO2. Show all posts
Monday, February 04, 2013
Monday, January 28, 2013
Current data shows biosphere carbon uptake holding steady
One of the biggest questions for ecosystem scientists is the degree to which terrestrial and marine ecosystems can continue to sequester carbon in the face of continuing human emissions of CO2 and accompanying global climate change.
This is one of the best (i.e. easiest to interpret) graphs to show that the fraction of emitted CO2 remaining in the atmosphere (i.e. not sequestered) has held steady at around 50% for the last 40+ years (purple line, "Airborne Fraction"). Data Sources: Fossil fuel CO2 emissions - Land use CO2 emissions - Airborne CO2 levels Graph by Willis Eschenbach.
Similar conclusions were reached by the National Oceanic and Atmospheric Administration’s Earth System Research Laboratory in Boulder, Colorado last year.
Similar conclusions were reached by the National Oceanic and Atmospheric Administration’s Earth System Research Laboratory in Boulder, Colorado last year.
Thursday, February 10, 2011
Global CO2 plumes
Ever wonder where our oxygen comes from in the winter? When vegetation dies back in the Northern Hemisphere, we have to subsist on old air until the summer. In this image, you can see the plume of carbon dioxide downwind of large human population centers.
Sunday, June 06, 2010
Carbon Considerations
How much CO2 does flying emit compared with cars, and how much would it cost to offset that?
The average airplane flight emits about 0.4lb of CO2 per passenger mile. Compare that to a decent 20mpg car, which emits about 1lb of C02 per mile. Of course, if you carpool, you can divide that by the number of passengers. This confirms most calculations I have seen that show that flying gets about 70 mpg per passenger (source) However, because the effect of CO2 at that altitude is greater, a correction factor gives an effective mpg of 35mpg per passenger, still better than most cars, but not if you carpool. If your flight isn't completely booked, your share of the CO2 emitted would be even greater. In general, about 20lb CO2 are emitted per gallon of gas (source)
So, driving or flying 2,000 miles would emit 800 lb and 2,000 lb, respectively. But for two people, the figures for flying would become 1,600 lb, versus 2,000 lb driving. Let's just say that it's about a ton.
What would it take to offset these emissions?
To offset one ton carbon costs about $15. A number of companies will do this. "Afforestation of crop or pasture land is estimated to have the potential to sequester
between 2.2 and 9.5 metric tons of CO2 per acre per year. Reforestation is estimated at 1.1 to 7.7
metric tons of CO2 per acre per year." (source: Congressional Research Service) So a fraction of an acre could sequester the carbon from a cross-country airplane flight.
Interestingly, the cost to plant an acre of trees is $250-$2,000/acre (average: $500). According to this analysis, if afforestation (greatest potential to sequester carbon) cost $200/acre it could be profitable at a carbon price of $21/ton.
The average airplane flight emits about 0.4lb of CO2 per passenger mile. Compare that to a decent 20mpg car, which emits about 1lb of C02 per mile. Of course, if you carpool, you can divide that by the number of passengers. This confirms most calculations I have seen that show that flying gets about 70 mpg per passenger (source) However, because the effect of CO2 at that altitude is greater, a correction factor gives an effective mpg of 35mpg per passenger, still better than most cars, but not if you carpool. If your flight isn't completely booked, your share of the CO2 emitted would be even greater. In general, about 20lb CO2 are emitted per gallon of gas (source)
So, driving or flying 2,000 miles would emit 800 lb and 2,000 lb, respectively. But for two people, the figures for flying would become 1,600 lb, versus 2,000 lb driving. Let's just say that it's about a ton.
What would it take to offset these emissions?
To offset one ton carbon costs about $15. A number of companies will do this. "Afforestation of crop or pasture land is estimated to have the potential to sequester
between 2.2 and 9.5 metric tons of CO2 per acre per year. Reforestation is estimated at 1.1 to 7.7
metric tons of CO2 per acre per year." (source: Congressional Research Service) So a fraction of an acre could sequester the carbon from a cross-country airplane flight.
Interestingly, the cost to plant an acre of trees is $250-$2,000/acre (average: $500). According to this analysis, if afforestation (greatest potential to sequester carbon) cost $200/acre it could be profitable at a carbon price of $21/ton.
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