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Monday, January 21, 2013


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Steve Bloom

A big difference between the Death Valley of the present and the Dallas of the future is humidity; while Dallas will probably be drier, it'll still be more humid than Death Valley is now. That makes for a big difference in public health terms. There is, unsurprisingly, a vast literature pertaining to this issue.


RCP8.5 is an unreasonable view of emissions, if one is concerned with things like economics. The growth of emissions in RCP8.5 does not match known resources of fossil fuels and the very real (and demonstrated) depletion of current resources and the relationship to price and production.

[RESPONSE: No, actually RCP 8.5 is a very reasonable view of climate forcings, which is what matters if one is concerned with real-life results. Emissions and forcings are not one and the same (see end note 1). If a half-filled tanker truck (emissions) drives at high speed into a fuel depot (positive feedbacks), there will be an explosion (RCP 8.5 or worse).

[RESPONSE PART 2: "While it is still too early to say whether any particular scenario is being tracked by current emissions, A1FI is considered to be as plausible as other non-mitigation scenarios and cannot be ruled out." - quote from Betts et al., Phil. Trans. R. Soc. A 13 January 2011 vol. 369 no. 1934 67-84. The A1FI scenario is nearly the same as the RCP8.5.

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Convert carbon dioxide (CO2) weight to carbon (C) weight


CO2/3.67 = C 


ex: 40 GtCO2 ≈ 10.9 GtC


1 Gt (Gigatonne) = 1 billion tonnes

1 tonne = 1,000 kg


Also: 1 Pg = 1 Gt


1 Pg (Petagram) = 1 quadrillion grams


Soil specialists tend to use Pg, as they are used to working with gram units per square meter of soil area. Atmospheric specialists tend to use Gt. 

Convert carbon emissions to ppm atmospheric CO2


GtC/2.12 = ppm

To convert emissions of carbon to atmospheric ppm CO2, carbon sinks must be taken into account. 

So far, terrestrial and oceanic sinks have taken up about 50% of CO2.



ex: 40 GtCO2 emissions ≈ 10.9 GtC

10.9 GtC/2.12 ≈ 5.14 ppm CO2 before accounting for sinks

5.14 ppm CO2 x 0.5 ≈ 2.57 ppm CO2 after accounting for sinks


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