This lecture provides an introduction to numerical methods with an emphasis to geosciences. The following topics will be discussed: -We discuss the concept of numerical methods and their accuracy. -We introduce the Taylor series as a fundamental expansion for numerical methods. -We derive several methods for numerically finding roots. -We discuss numerical differentiation and integration methods. -We solve linear systems of equations with direct and iterative methods. -We solve ordinary and partial differential equations with a variety of methods. close