Carbon Dioxide Concentration in the Atmosphere
We’ll start to recreate Gregor Aisch’s plot of carbon dioxide concentration over time.
data(co2_ml)co2_ml is a data.frame of monthly CO2 measurements from March 1958 to January 2022, taken at Mauna Loa, Hawaii . In order to plot a line for each decade on a common scale, we first need to add one additional variable to co2_ml that we’ll call date_scale.
co2_ml$date_scale <- as.Date(sprintf("%d-%d-01", 1950 + (co2_ml$year %% 10), co2_ml$month))Also, we create a helper function to change the date labels of the x-axis.
axis_labeller <- function(date) {
year <- as.integer(format(date, "%Y"))
tmp <- year - min(year, na.rm = TRUE)
replace(tmp, !tmp, "")
}See full code
# layers
p <- ggplot(co2_ml, aes(date_scale, co2_ppm, color = decade))
# sustainable level
p <- p + geom_hline(aes(yintercept = 350),
color = "#dbd9db",
size = 1)
p <- p + geom_text(aes(x = as.Date("1951-01-01"), y = 348),
label = "sustainable level",
size = text_size + .3,
color = "#dbd9db",
hjust = "left",
inherit.aes = FALSE)
p <- p + geom_line()
p <- p + geom_pointless(location = c("first", "last"), size = 2)
# label decades
p <- p + geom_text(
data = subset(co2_ml, subset = decade != "2020's"),
aes(label = decade),
size = text_size,
stat = "pointless",
location = "last",
hjust = "left",
nudge_x = 40
)
# label at first year in decade
p <- p + geom_text(
data = subset(co2_ml, subset = decade != "1950's"),
aes(label = year, group = decade),
size = text_size,
color = text_color,
stat = "pointless",
location = "first",
vjust = "top",
hjust = "left",
nudge_y = -2
)
# label at last year in decade
p <- p + geom_text(
data = subset(co2_ml, subset = !(decade %in% c("1950's", "2020's"))),
aes(label = year, group = decade),
size = text_size,
color = text_color,
stat = "pointless",
location = "maximum",
vjust = "bottom",
nudge_y = 1
)
# label the years 2014 to 2018 in the format '%y
p <- p + lapply(2014:2018, function(yrs) {
geom_text(
data = subset(co2_ml, subset = year == yrs),
aes(label = sprintf("'%i", year %% 100), group = year),
size = text_size,
color = text_color,
stat = "pointless",
location = "maximum",
vjust = "bottom",
nudge_y = 1
)
})
# highlight all-time maximum
p <- p + geom_pointless(
data = subset(co2_ml, subset = decade == "2020's"),
location = "maximum",
size = 8,
shape = 21,
fill = NA,
stroke = .9
)
# label all-time maximum
p <- p + ggtext::geom_richtext(
aes(
x = date_scale + 500,
y = co2_ppm - 3,
group = NULL,
label = sprintf("**%g ppm**<br>%s %s", round(co2_ppm), month.name[month], year)
),
stat = "pointless",
location = "maximum",
size = text_size,
color = text_color,
fill = NA,
label.color = NA
)
# draw curve from all-time maximum to its label
p <- p + geom_curve(
data = subset(co2_ml, subset = decade == "2020's"),
aes(
x = date_scale + 90,
xend = date_scale + 500,
y = co2_ppm + 2,
yend = co2_ppm + 2
),
stat = "pointless",
location = "maximum",
curvature = -.4,
size = .35,
color = text_color,
inherit.aes = FALSE
)
# scales
p <- p + scale_x_date(
breaks = as.Date(sprintf("%i-01-01", c(1950:1960))),
labels = axis_labeller,
expand = expansion(mult = c(0.01, -.03)),
limits = as.Date(sprintf("%i-01-01", c(1950, 1961))))
# colors
p <- p + scale_color_manual(
values = c(
'#f4ae1b',
'#e99950',
'#dc8471',
'#cc708f',
'#b85baa',
'#9f46c6',
'#7a31e1',
'#311dfc'
)
)
# title, subtitle, caption
p <- p +
labs(title = "Carbon Dioxide Concentration in the Atmosphere",
subtitle = "Each line represents one decade, from 1958 to 2022. CO2 concentration is measured in\nparts per million* (ppm).",
caption = "*The mole fraction of CO2, expressed as parts per million (ppm) is the number of molecules of CO2 in every million\nmolecules of dried air (water vapor removed). The 'sustainable level' of 350ppm, equivalent to the 1990 levels, has\nbeen identified by UN climate scientists.\nSource: National Oceanic & Atmospheric Adm. (NOAA)",
x = "Years into decade",
y = "ppm")
