How many simulations?

• The Monte Carlo solution:

  • Vary parameters over very wide ranges
  • Simulate 1950-2050 changes with many models
  • Down-weight predictions from runs that fail to fit observed changes over 1950-2000

• Non-linear: can’t just add up responses to different perturbations. Eg 5 settings of 9 parameters gives 59 permutations, or 2M simulations

• Currently typical ensemble sizes with a comprehensive climate model: 4 simulations