text: import climlab
  from climlab.dynamics.diffusion import Diffusion
  import matplotlib.pyplot as plt
  
  c = climlab.GreyRadiationModel()
  K = 0.5
  d = Diffusion(K=K, state = {'Tatm':c.state['Tatm']}, **c.param)
  
  c.add_subprocess('diffusion',d)
  
  ### Integrate & Plot ###
  
  fig = plt.figure( figsize=(6,4))
  ax = fig.add_subplot(111)
  
  ax.plot(c.lev, c.state['Tatm'], label='step 0')
  c.step_forward()
  ax.plot(c.lev, c.state['Tatm'], label='step 1')
  
  ax.invert_xaxis()
  ax.set_title('Diffusion subprocess')
  ax.set_xlabel('level (mb)')
  #ax.set_xticks([])
  ax.set_ylabel('temperature (K)')
  ax.legend(loc='best')
  plt.show()
  