2025年全球气候状况报告_46页_7mb

Summary of the State of the Global Climate 2025

Core Content

The State of the Global Climate 2025 is an annual report by the World Meteorological Organization (WMO) that provides a consolidated assessment of global climate conditions, key indicators, and high-impact weather events. It serves as a complementary resource to the Intergovernmental Panel on Climate Change (IPCC) and is intended for a broad audience, including policymakers, scientists, educators, and the general public.

The report highlights the continued warming of the Earth system, driven by increasing greenhouse gas concentrations, particularly carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). These gases have reached record levels, with CO₂ concentrations in 2024 being the highest in the last 2 million years and CH₄ and N₂O reaching their highest levels in the last 800,000 years. The 2025 report confirms that these concentrations continued to rise, reinforcing the ongoing climate crisis.

Key Climate Indicators

1. Atmospheric Carbon Dioxide

• Key Messages:
  • CO₂ levels reached a new high in 2024, with the largest annual increase since 1957.
  • CO₂, CH₄, and N₂O all increased in 2025.
• State of the Indicator:
  • Global average CO₂ concentration in 2024 was 423.9 ppm, representing about 3306 Gt of CO₂ in the atmosphere.
  • The airborne fraction of CO₂ emissions remained around 50% in the 2015-2024 period, with the ocean absorbing 29% and land 21%.
• Indicator Background:
  • CO₂ is the largest contributor to climate change, responsible for 66% of radiative forcing from long-lived greenhouse gases since 1750.
  • The report notes that while CO₂ helps buffer climate change, it also leads to ocean acidification, which has significant ecological and economic impacts.

2. Global Mean Near-Surface Temperature

• Key Messages:
  • 2025 was the second or third warmest year on record, slightly cooler than 2024.
  • The past eleven years (2015–2025) were the eleven warmest on record.
• State of the Indicator:
  • The annual average global mean near-surface temperature in 2025 was 1.43°C ± 0.13°C above the 1850–1900 baseline.
  • The warming trend is consistent with the Paris Agreement's long-term temperature goal, but single years do not indicate exceeding the 1.5°C warming level.
• Indicator Background:
  • The report uses nine global temperature datasets to assess temperature changes, with minor discrepancies due to differences in measurement methods and data coverage.

3. Ocean Heat Content

• Key Messages:
  • Ocean heat content reached a record high in 2025, surpassing the previous record set in 2024.
  • The rate of ocean warming over the past 20 years (2005–2025) was more than twice that of the previous 40 years (1960–2005).
• State of the Indicator:
  • The global ocean heat content (to 2000 m depth) increased by 5.8 ± 0.5 ZJ per year from 1971 to 2025.
  • The deep ocean (2000–6000 m) also warmed at a rate of 1 ± 0.2 ZJ per year.
• Indicator Background:
  • Ocean heat content is a key indicator of climate change, as the ocean absorbs 91% of the excess energy trapped by greenhouse gases.
  • Ocean warming has irreversible effects on marine ecosystems, biodiversity, and contributes to sea-level rise.

4. Global Mean Sea Level

• Key Messages:
  • Global mean sea level in 2025 was comparable to 2024 levels, with a smaller year-to-year increase due to La Niña conditions.
  • The rate of sea-level rise since 2012 is higher than in the earlier satellite period (1993–2011).
• State of the Indicator:
  • By the end of 2025, global mean sea level was 11 cm higher than in January 1993.
  • The average rate of sea-level rise from 1993 to 2011 was 2.65 ± 0.3 mm/year, and from 2012 to 2025, it increased to 4.75 ± 0.3 mm/year.
• Indicator Background:
  • Sea-level rise is driven by ocean thermal expansion and melting of land ice.
  • The report warns of cascading impacts on coastal communities, ecosystems, and infrastructure, including flooding, salinization, and habitat loss.

5. Ocean pH

• Key Messages:
  • The global average ocean surface pH has declined by 0.017 ± 0.001 units per decade over the past 41 years.
  • Regional variations in pH decline are notable, with the Indian Ocean, Southern Ocean, and Pacific regions experiencing the most rapid acidification.
• State of the Indicator:
  • The decline in ocean pH is unprecedented for at least 26,000 years, according to the IPCC.
  • The ocean continues to absorb 29% of anthropogenic CO₂ emissions, leading to acidification and affecting marine life.
• Indicator Background:
  • Ocean acidification is linked to increased CO₂ absorption, which lowers pH and disrupts carbonate chemistry.
  • The report emphasizes the impact on marine biodiversity, shellfish aquaculture, and fisheries, as well as the contribution to Sustainable Development Goals (SDGs).

6. Glacier Mass Balance

• Key Messages:
  • The 2024/2025 hydrological year saw exceptional glacier mass loss, ranking among the five most negative balances on record.
  • Eight of the ten most negative annual glacier mass balances since 1950 have occurred since 2016.
• State of the Indicator:
  • Observations from 155 glaciers indicate extremely negative mass balance in 2024/2025.
  • Iceland and the Pacific coast of North America experienced the most severe mass loss.
• Indicator Background:
  • Glacier mass balance is a critical indicator of climate change, reflecting the net gain or loss of ice mass.
  • The report highlights the long-term trend of glacier retreat, with significant ice loss from Antarctica and Greenland since satellite records began.

High-Impact Weather and Climate Events

• The report documents extreme weather events in 2025, including heatwaves, cold extremes, floods, droughts, and tropical cyclones.
• These events are linked to climate drivers such as El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD).
• Case Study: The report includes a detailed analysis of climate and heat impacts on health, highlighting the increased risks to vulnerable populations.

Conclusion

The State of the Global Climate 2025 underscores the accelerating pace of climate change, with record-breaking greenhouse gas levels, rising global temperatures, increased ocean heat content, accelerated sea-level rise, and ocean acidification. These changes are having cascading impacts on both natural and human systems, emphasizing the need for continued monitoring, adaptation, and mitigation efforts to address the challenges posed by a warming planet.