Table 3 Present value (PV) of global social costs of CH4 emissions, 2015–2050 (billion 2015 US$), from a harmful algal bloom sufficient to close all MI and OH beaches on Lake Erie.

From: Protecting local water quality has global benefits

 

PV

PV

Closure at 30 ppb chlorophyll aa

Closure at 50 ppb chlorophyll ab

SC-CH4 methodc

 Discount rate = 5%

13.72

23.87

 Discount rate = 3%

39.42

68.59

 Discount rate = 2.5%

55.16

95.97

SC-CO2 × CO2-e methodd

 Discount rate = 5%

9.92

17.25

 Discount rate = 3%

42.12

73.28

 Discount rate = 2.5%

66.08

114.96

  1. aA 30 ppb chlorophyll a concentration represents an 80–100% risk of Cyanobacteria blooms21; we associate this with a 1.003926 Tg yr−1 increase in CH4 emissions.
  2. bThe World Health Organization chlorophyll a guideline for avoiding moderate probability of adverse health effects in recreational waters is 50 ppb22; our estimates suggest an associated increase of 1.746587 Tg yr−1 in CH4 emissions.
  3. cSC-CH4 method uses estimates of the social costs of CO2, CH4, and N2O adapted from published sources16,29.
  4. dSC-CO2 × CO2-e method converts CH4 to CO2-equivalents and uses estimates of the social cost of carbon dioxide15.
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