1. A method for ablating a target tissue with cryo-energy arising from use of a cryogen circulating along a path, said method comprising the steps of: measuring a cryogen flowrate of the cryogen circulating along the path; measuring a first temperature of the cryogen while the cryogen is in a liquid state at a first location along the path and moving towards said tissue, said first location being within an inflow conduit; measuring a second temperature of the cryogen while the cryogen is in a liquid state at a second location along the path and moving away from said tissue, said second location being within an outflow conduit; calculating a temperature difference between said first temperature and said second temperature; and applying an amount of cryo-energy to the tissue based on said temperature difference and the cryogen flowrate.