What is up with the negative N2O

Set Up

library(hector)
library(ggplot2)

Objective

Why is the N2O RF negative during the historical period?

path <- here::here("input", "hector_ssp245.ini") 
core <- newcore(path)
run(core)

Hector core:    Unnamed Hector core
Start date: 1745
End date:   2300
Current date:   2300
Input file: /Users/dorh012/Documents/2021/2021-hector-ar6rf/input/hector_ssp245.ini

out <- fetchvars(core, 1750:2100, vars = c(GLOBAL_TEMP(), RF_N2O(), 
                                           ATMOSPHERIC_N2O(), EMISSIONS_N2O(), 
                                           NAT_EMISSIONS_N2O()))

RF

out %>% 
  filter(year %in% 1750:2010) %>% 
  filter(variable == RF_N2O()) %>% 
  ggplot(aes(year, value)) + 
  geom_line() + 
  labs(title = "N2O RF during the historical period", y = "RF") + 
  geom_hline(yintercept = 0, color = "red")

out %>% 
  filter(year %in% 1750:2010) %>% 
  filter(variable == ATMOSPHERIC_N2O()) %>% 
  ggplot(aes(year, value)) + 
  geom_line() + 
  labs(title = "N2O concentrations during the historical period") + 
  geom_hline(yintercept = 273.87, color = "red") + 
  labs(y = "[N2O]")

out %>% 
  filter(year %in% 1750:2010) %>% 
  filter(variable == EMISSIONS_N2O()) %>% 
  ggplot(aes(year, value)) + 
  geom_line() + 
  labs(title = "Anthropogenic N2O Emissions") + 
  labs(y = "N2O")

out %>% 
  filter(year %in% 1750:2010) %>% 
  filter(variable == NAT_EMISSIONS_N2O()) %>% 
  ggplot(aes(year, value)) + 
  geom_line() + 
  labs(title = "Natural N2O Emissions") + 
  labs(y = "N2O")

I think that is it odd that the N2O concentrations decline after preindustiral.

What happens if the preinustrial N2O is changed?

setvar(core, NA, var = PREINDUSTRIAL_N2O(), values = 272.9596, unit = "ppbv N2O")
reset(core)

Hector core:    Unnamed Hector core
Start date: 1745
End date:   2300
Current date:   1745
Input file: /Users/dorh012/Documents/2021/2021-hector-ar6rf/input/hector_ssp245.ini

run(core)

Hector core:    Unnamed Hector core
Start date: 1745
End date:   2300
Current date:   2300
Input file: /Users/dorh012/Documents/2021/2021-hector-ar6rf/input/hector_ssp245.ini

out2 <- fetchvars(core, 1750:2100, vars = c(GLOBAL_TEMP(), RF_N2O(), 
                                           ATMOSPHERIC_N2O(), EMISSIONS_N2O(), 
                                           NAT_EMISSIONS_N2O()))


setvar(core, NA, var = PREINDUSTRIAL_N2O(), values = 265, unit = "ppbv N2O")
reset(core)

Hector core:    Unnamed Hector core
Start date: 1745
End date:   2300
Current date:   1745
Input file: /Users/dorh012/Documents/2021/2021-hector-ar6rf/input/hector_ssp245.ini

run(core)

Hector core:    Unnamed Hector core
Start date: 1745
End date:   2300
Current date:   2300
Input file: /Users/dorh012/Documents/2021/2021-hector-ar6rf/input/hector_ssp245.ini

out3 <- fetchvars(core, 1750:2100, vars = c(GLOBAL_TEMP(), RF_N2O(), 
                                           ATMOSPHERIC_N2O(), EMISSIONS_N2O(), 
                                           NAT_EMISSIONS_N2O()))