The Climate Monitoring Branch at the National Climatic Data Center produces an annual overview of regional and global climatic conditions. The focus of this climate summary is on the observed weather and climatic trends in 2004, with emphasis on how they compared with the historical record. This paper will focus on the monthly, seasonal, and annual climate of 2004, as well as unusual events and extreme weather, across the U.S. and around the world.

Numerous climatic elements will be analyzed globally and regionally in developing the climate summary, including: temperature, precipitation, tropical cyclone activity, snow cover and sea ice, droughts, floods, and stratospheric ozone and trace gases. Particular emphasis will be placed on analysis of anomalies and trends in global temperature, given the observed rise in globally averaged temperature over the past century. Analysis of the state of the El Niņo/Southern Oscillation (ENSO) phenomenon will also be presented, focusing on changes in regional precipitation patterns related to ENSO in 2004.