2015-2019年全球气候（英文版）_24页_1mb

Summary of The Global Climate in 2015-2019

Core Content

The report "The Global Climate in 2015-2019" by the World Meteorological Organization (WMO) provides a comprehensive overview of global climate trends and impacts over the five-year period from 2015 to 2019. It highlights the continued increase in greenhouse gas concentrations, rising global temperatures, ocean acidification, sea-level rise, and the decline in sea-ice extent in both the Arctic and Antarctic. The report also discusses the frequency and impact of extreme weather events and their economic and human consequences.

Main Findings

Greenhouse Gases

• CO₂, CH₄, and N₂O concentrations increased significantly compared to previous years.
• The global mean surface CO₂ concentration reached 403 ppm in 2015-2017, up from 395.5 ppm in 2011-2015.
• Methane (CH₄) levels reached 1851.7 ppb in 2015-2017, a 21% increase over the previous five-year period.
• Nitrous oxide (N₂O) levels increased to 329.1 ppb, a 19% rise.
• The growth rates of these gases were nearly 20% higher than in the 2011-2015 period.
• CO₂ emissions from fossil fuel combustion and cement production have continued to rise, contributing to the global carbon budget.

Temperature

• 2015-2019 was the warmest five-year period on record, with global temperatures 1.1°C above pre-industrial levels.
• The global temperature increased by 0.2°C compared to the 2011-2015 period.
• 2016 was the warmest year on record, over 1°C above pre-industrial levels.
• Land-surface temperatures were 1.7°C above pre-industrial levels, with most land areas warmer than average.
• Sea-surface temperatures were 0.8°C above pre-industrial levels, with notable warming in the northeast Pacific, western North Atlantic, and western Indian Ocean.
• Temperature anomalies were highest in 2018, with record-breaking heatwaves affecting all continents.

Ocean

• Sea levels rose at an accelerated rate, reaching 90 mm since 1993.
• The rate of sea-level rise increased from 3.04 mm/year (1997-2006) to 4.36 mm/year (2007-2016).
• Ocean heat content reached new records, with 2018 being the warmest year for ocean heat content.
• The ocean absorbed 30% of anthropogenic CO₂ emissions, leading to increased acidity.
• Ocean pH has decreased by 26% since the beginning of the industrial revolution.
• Sea-ice extent in the Arctic continued to decline, with September minimum sea-ice extent in 2019 setting a new record low.
• Antarctic sea-ice extent also declined, with record lows in summer in 2017 and 2018.

Cryosphere

• Greenland ice sheet mass loss accelerated, with a negative SMB anomaly observed in most regions.
• Antarctic ice sheet mass loss increased six-fold between 1979 and 2017, contributing significantly to global sea-level rise.
• Glaciers worldwide lost mass at an accelerating rate, with an average specific mass change of -908 mm water equivalent per year during 2015-2018.
• Northern hemisphere spring snow cover decreased by -4.2% per decade in May and -12.9% per decade in June.
• Snow loss was most significant during the 2015-2018 period, with below-average snowfall in Canada and less than normal snow in Central Europe and southern South America.

Extreme Events

• Heatwaves were the deadliest meteorological hazard, causing over 8,900 deaths worldwide during 2015-2019.
• Hurricane Maria in 2017 resulted in over 2,000 deaths in Puerto Rico and Dominica.
• Hurricane Harvey in 2017 caused economic losses of over US$125 billion.
• Wildfires were widespread, particularly in Europe, North America, and the Amazon, with record-breaking fires in the Arctic in 2019.
• Tropical cyclones caused the highest economic losses, with floods and landslides being the primary contributors.

Key Information

• The report is part of the WMO Statements on Climate, providing authoritative information on climate trends and impacts.
• It relies on operational monitoring systems at global, regional, and national levels.
• Global temperature anomalies were highest in 2018, with 2019 likely to be one of the five warmest years.
• Sea-level rise is dominated by ice melt, particularly from glaciers and ice sheets.
• Ocean acidification is a direct result of increased CO₂ absorption, leading to a 26% increase in acidity since the industrial revolution.
• Climate-related risks have exacerbated food insecurity and threatened marine ecosystems and human health.
• Economic impacts from extreme weather events were substantial, with Hurricane Harvey being the costliest event of the period.

References

• Data sources include NASA, NOAA, WMO, and various international agencies.
• The report is authored by a team of experts from around the world, including Peter Siegmund, Jakob Abermann, and others.
• The findings reflect the authors' individual perspectives and do not necessarily represent the views of WMO or its Members.