# A pie chart of greenhouse gas emissions

The following program depicts the emissions of greenhouse gases by mass of "carbon equivalent". Data from the 2007 IPCC report, 2007: Climate Change 2007: Synthesis Report. Contribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, Pachauri, R.K and Reisinger, A. (eds.)]

import numpy as np
import matplotlib.pyplot as plt

# Annual greenhouse gas emissions, billion tons carbon equivalent (GtCe)
gas_emissions = np.array([(r'$\mathrm{CO_2}$-d', 2.2),
(r'$\mathrm{CO_2}$-f', 8.0),
('Nitrous\nOxide', 1.0),
('Methane', 2.3),
('Halocarbons', 0.1)],
dtype=[('source', 'U17'), ('emission', 'f4')])

# 5 colours beige
colours = ['#C7B299', '#A67C52', '#C69C6E', '#754C24', '#534741']

explode = [0, 0, 0.1, 0, 0]

fig, ax = plt.subplots()
ax.axis('equal')        # So our pie looks round!

The segment corresponding to nitrous oxide has been "exploded" by 10% and the percentage values are formatted to one decimal place (autopct='%.1f%%').