In 2007 the Fourth Assessment Report from the Intergovernmental Panel on Climate Change (IPCC) gave us the latest generally accepted view on what has been happening and is likely to happen to our climate. Our ability to make such predictions and to develop increasingly sophisticated and, we hope, accurate models relies on the existence of a very large collection of weather measurements, in some cases going back over a hundred years. The “ground truth” of the measured data is the base of the pyramid on which is built all subsequent analysis and modelling. This lecture will describe the Irish climate monitoring networks and the challenges faced in meeting the required standards in measurement and data processing and analysis.