2019年全球气候状况（英文版）.pdf

WMO Statement on the State of the Global Climate in 2019 WMO-No. 1248 WEATHER CLIMATE WATERThe right of publication in print, electronic and any other form and in any language is reserved by WMO. Short extracts from WMO publications may be reproduced without authorization, provided that the complete source is clearly indicated. Editorial correspondence and requests to publish, reproduce or translate this publication in part or in whole should be addressed to: Chair, Publications Board World Meteorological Organization (WMO) 7 bis, avenue de la Paix Tel.: +41 (0) 22 730 84 03 P.O. Box 2300 Fax: +41 (0) 22 730 81 17 CH-1211 Geneva 2, Switzerland Email: publicationswmo.int ISBN 978-92-62-11248-5 NOTE The designations employed in WMO publications and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of WMO concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. The mention of specific companies or products does not imply that they are endorsed or recommended by WMO in preference to others of a similar nature which are not mentioned or advertised. The findings, interpretations and conclusions expressed in WMO publications with named authors are those of the authors alone and do not necessarily reflect those of WMO or its Members. Cover illustration: Volunteer firefighters rescuing lives and farms from bushfire in Bundaberg, Queensland (Australia). WMO-No. 1248 World Meteorological Organization, 2020Contents Foreword 3 Statement by the United Nations Secretary-General 4 Key messages 5 Global Climate Indicators 6 Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Greenhouse gases and ozone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Ocean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Cryosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Drivers of short-term climate variability. . . . . . . . . . . . . . . . . . . . . . . . . . . .17 High-impact events in 2019. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 Climate-related risks and impacts 27 Health at increasing risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Food security and population displacement continue to be adversely affected by climate variability and extreme weather . . . . . . . . . . . . . . . . . . . . 29 Marine life and biodiversity threatened by the changing climate and extreme events . . 32 Case study: Severe climatic shocks lead to a deterioration of the food security situation and to population displacement in the Greater Horn of Africa in 2019 . . . . . .33 Dataset references 35 List of contributors 39Since 2016, the following United Nations agencies have significantly contributed to the WMO Statement on the State of the Global Climate in support of climate policy and action: Food and Agriculture Organization of the United Nations (FAO), Intergovernmental Oceanographic Commission of the United Nations Educational, Scientific and Cultural Organization (IOC/UNESCO), International Monetary Fund (IMF), International Organization for Migration (IOM), United Nations Conference on Trade and Development (UNCTAD), United Nations Environment Programme (UNEP), Office of the United Nations High Commissioner for Refugees (UNHCR), United Nations Office for Disaster Risk Reduction (UNDRR), World Health Organisation (WHO) 3 Foreword Concentrations of greenhouse gases, particularly CO 2 , continue to rise. The year 2019 ended with a global average temperature of 1.1 C above estimated pre-industrial averages, second only to the record set in 2016. Without the role of El Nio in the warming increase observed in 2016, 2019 would have been a record year. Temperature is one indicator of the ongoing climate change. Also, sea levels are rising at an increasing pace, through greater warming of the oceans, on the surface and in the depths, and through the enhanced melting of Greenlands ice and of glaciers, exposing coastal areas and islands to a greater risk of flooding and the submersion of low-lying areas. Furthermore, in 2019, heatwaves, combined with long periods of drought, were linked to wildfires of unprecedented size. This was the case in Australia, where millions of hectares were set ablaze, and in Siberia and other Arctic regions hit by wildfires of record intensity. Besides these powerful phenomena, there has been weather-related damage, such as the effects of multi-annual droughts on the internal and cross-border migration of populations, greater exposure of the world population to health hazards due to heat and pollution, and the reduction of economic growth, especially in developing economies, due to rising temperatures and weather extremes. The results of this report demonstrate that climate change is already very visible in various ways. More ambitious climate mitigation efforts are needed to keep the warming below 2 C by the end of the century. The World Meteorological Organization will continue to follow closely climate variability and change and their impact. An information portal is being set up to allow indicators of the state of the climate to be tracked. I would like to thank the many expert teams in climatology and other disciplines, National Meteorological and Hydrological Services, the global and regional centres for climate data collection and analysis and the United Nations sister agencies. Thanks to their unfailing collaboration, the WMO Statement on the State of the Global Climate has become a flagship publication providing policymakers all over the world with essential climate information. (P. Taalas) Secretary-General4 Statement by the United Nations Secretary-General Climate change is the defining challenge of our time. Time is fast running out for us to avert the worst impacts of climate disruption and protect our societies from the inevitable impacts to come. Science tells us that, even if we are successful in limiting warming to 1.5 C, we will face significantly increased risks to natural and human systems. Yet, the data in this report show that 2019 was already 1.1 C warmer than the pre-industrial era. The consequences are already apparent. More severe and frequent floods, droughts and tropical storms, dangerous heatwaves and rising sea levels are already severely threatening lives and livelihoods across the planet. We are currently way off track to meeting either the 1.5 C or 2 C targets that the Paris Agreement calls for. We need to reduce greenhouse gas emissions by 45% from 2010 levels by 2030 and reach net zero emissions by 2050. And for that, we need political will and urgent action to set a different path. This report outlines the latest science and illustrates the urgency for far-reaching climate action. It brings together data from across the fields of climate science and lists the potential future impacts of climate change from health and economic consequences to decreased food security and increased displacement. I call on everyone from government, civil society and business leaders to individual citizens to heed these facts and take urgent action to halt the worst effects of climate change. We need more ambition on mitigation, adaptation and finance in time for the climate conference (COP26) to be held in Glasgow in November. That is the only way to ensure a safer, more prosperous and sustainable future for all people on a healthy planet. (A. Guterres) United Nations Secretary-General5 Key messages 5 Global atmospheric mole fractions of greenhouse gases reached record levels in 2018 with carbon dioxide (CO 2 ) at 407.80.1 parts per million (ppm), methane (CH 4 ) at 18692 parts per billion (ppb) and nitrous oxide (N 2 O) at 331.10.1 ppb. These values constitute, respectively, 147%, 259% and 123% of pre-industrial levels. Early indications show that the rise in all three CO 2 , CH 4and N 2 O continued in 2019. The global mean temperature for 2019 was 1.10.1 C above pre-industrial levels. The year 2019 is likely to have been the second warmest in instrumental records. The past five years are the five warmest on record, and the past decade, 20102019, is also the warmest on record. Since the 1980s, each successive decade has been warmer than any preceding one since 1850. The ocean absorbs around 90% of the heat that is trapped in the Earth system by rising concentrations of greenhouse gases. Ocean heat content, which is a measure of this heat accumulation, reached record- high levels again in 2019. As the ocean warms it expands and sea levels rise. This rise is further increased by the melting of ice on land, which then flows into the sea. Sea level has increased throughout the altimeter record, but recently sea level has risen at a higher rate due partly to increased melting of ice sheets in Greenland and Antarctica. In 2019, the global mean sea level reached its highest value since the beginning of the high-precision altimetry record (January 1993). Over the decade 20092018, the ocean absorbed around 23% of the annual CO 2emissions, lessening the increase in atmospheric concentrations. However, CO 2absorbed in sea water decreases its pH, a process called ocean acidification. Observations from open- ocean sources over the last 20 to 30 years show a clear decrease in average pH at a rate of 0.0170.027 pH units per decade since the late 1980s. The year 2019 saw low sea-ice extent in both the Arctic and the Antarctic. The daily Arctic sea-ice extent minimum in September 2019 was the second lowest in the satellite record. In Antarctica, variability in recent years has been high with the long-term increase offset by a large drop in extent in late 2016. Extents have since remained low, and 2019 saw record-low extents in some months.6 Global Climate Indicators Global Climate Indicators describe the changing climate, providing a broad picture of climate change at a global level that goes beyond temperature. They provide important information for the domains most relevant to climate change, including the composition of the atmosphere, the energy changes that arise from the accumulation of greenhouse gases and other factors, and the responses of land, oceans and ice. Key Global Climate Indicators include global mean surface temperature, atmospheric greenhouse gas concentrations, ocean heat content, global sea level, ocean acidification, sea-ice extent and the mass balance of glaciers and ice sheets. 1The five datasets comprise three in situ datasets HadCRUT.4.6.0.0 produced by the UK Met Office and the Climatic Research Unit at the University of East Anglia, NOAAGlobalTemp v5 produced by the US National Atmospheric and Oceanic Administration (NOAA), and GISTEMP v4 produced by the US National Aeronautics and Space Administration (NASA) Goddard Institute for Space Studies as well as two reanalyses ERA5 produced by the European Centre for Medium-range Weather Forecasts (ECMWF) for the Copernicus Climate Change Service, and JRA-55 produced by the Japan Meteorological Agency. 2Total warming refers to the actual temperature change, irrespective of cause, while human-induced warming refers to the component of that warming that is attributable to human activities. The estimate of human-induced warming is based on: Haustein, K. et al., 2017: A real-time Global Warming Index. Scientific Reports 7, 15417, doi:10.1038/s41598-017-14828-5. TEMPERATURE The global mean temperature for 2019 was around 1.1 0.1 C above the 18501900 baseline, used as an approximation of pre- industrial levels. The year 2019 is likely to be the second warmest on record. The WMO assessment is based on five global temperature datasets 1(Figure 1), with four of the five putting 2019 in second place and one dataset placing it third warmest. The spread of the five estimates is between 1.05 C and 1.18 C. The Intergovernmental Panel on Climate Change (IPCC) Special Report: Global Warming of 1.5 C (IPCC SR15) concluded that “Human- induced warming 2reached approximately 1 C (likely between 0.8 C and 1.2 C) above pre-industrial levels in 2017, increasing at 0.2 C (likely between 0.1 C and 0.3 C) per decade (high confidence)”. An update of the figures for 2019 is consistent with continued warming in the range of 0.10.3 C per decade. The year 2016, which began with an exceptionally strong El Nio, remains the warmest on record. Weak El Nio conditions in the first half of 2019 may have made a small contribution to the high global temperatures 1850 1875 1900 1925 1950 1975 2000 2025 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0.2 HadCRUT NOAAGlobalTemp GISTEMP ERA5 JRA-55 Year C Figure 1. Global annual mean temperature difference from pre- industrial conditions (18501900). The two reanalyses (ERA5 and JRA-55) are aligned with the in situ datasets (HadCRUT, NOAAGlobalTemp and GISTEMP) over the period 19812010. 10 5 3 2 1 0.5 0 0.5 1 2 3 5 10 C Data source: ERA5 Figure 2. Surface-air temperature anomaly for 2019 with respect to the 19812010 average (Source: European Centre for Medium-range Weather Forecasts (ECMWF) ERA5 data, Copernicus Climate Change Service)7 in 2019, but there was no clear increase in temperature at the start of the year as was seen in early 2016. The past five years, 20152019, are the five warmest on record. The last five-year (2015 2019) and ten-year (20102019) averages are also the warmest on record. 3Since the 1980s, each successive decade has been warmer than any preceding one since 1850. Although the overall warmth of the year is clear, there were variations in temperature anomalies across the globe. Most land areas were warmer than the recent average (1981 2010, Figure 2). The year 2019 was among the top three warmest on record since at least 1950 over Africa. Other continental averages were among the three warmest, except the average