Python Matplotlib subscript

This is how to add subscripts to a string in your matlab plot
See more here: http://matplotlib.org/users/mathtext.html

plt.scatter(cyr_no80,co2_no80,color='k',marker='+',label='points')
plt.title(r'CO$_2$ Concentration, no 1980s')
plt.ylabel(r'CO$_2$ (ppm)')
plt.xlabel('Year')