A contribution to The United Nations Task Force on El Niño for implementation of United Nations General Assembly Resolutions 52/200 and 53/185 The Inter-Agency Committee for the Climate Agenda led by the World Meteorological Organization with support from the Intergovernmental Oceanographic Commission of UNESCO the United Nations Environment Programme and the International Council for Science 1999 Front cover: The sea surface warms and rises off the South American coast and out into the Pacific Ocean as the El Niño of 1997–1998 spreads its influence across the planet. Sea level anomaly 10 November 1997 as measured by TOPEX/Poseidon. (NASA) WMO-No. 905 © 1999, World Meteorological Organization ISBN 92-63-10905-2 NOTE The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the World Meteorological Organization concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. Contents Page Foreword . 5 Preface . 6 Executive Summary . 7 Introduction . 11 Part I — The Climate System . 15 The seasonal cycle of climate . 15 The El Niño . 15 The Southern Oscillation . 19 Ocean-atmosphere coupling — ENSO . 21 Global change . 22 Part II — The 1997-98 El Niño event . 24 Monitoring El Niño . 24 The El Niño cycle . 26 Overview . 26 Prior conditions . 27 Commencement . 27 Evolution . 29 The mature phase . 30 The decline . 33 An historical comparison . 34 Regional climate anomalies and impacts . 36 South and Central America . 37 North and Central America . 42 El Niño effects on coastal fish resources — a case study . 46 China . 48 Equatorial Asia-Pacific . 51 Papua New Guinea — A case study . 53 South-West Pacific . 56 East and Southern Africa . 59 A global assessment . 61 Part III — The way ahead . 62 Prediction on seasonal timescales . 62 Applications of forecasts . 64 Bridging the knowledge gulf — a case study . 66 Climate Information and Prediction Services . 68 Risk and society . 69 Economic dimension . 70 Environmental dimension . 71 3 Page Developmental dimension . 71 Societal dimension . 72 An integrating framework for action . 72 International scientific infrastructure . 73 Regional cooperation . 75 National climate programmes . 77 Appendix — Climate processes . 78 The atmosphere . 78 Surface exchange processes . 79 The ocean surface layer . 80 Sea surface temperatures . 81 Monsoon circulations . 83 Teleconnections . 86 Climate prediction . ..