UN charts course to manage global warming-limit breach, Pg1

Key Highlights:

• The United Nations Environment Programme (UNEP) outlined an "overshoot, peak, and decline" pathway to manage the likely breach of the 1.5 degrees Celsius global warming limit.
• The UNEP report, "Limiting Overshoot," projects global warming will cross 1.5 degrees Celsius in the next few years, deeming it unavoidable.
• The 30th UN Climate Change Conference (COP30) in 2025 in Belém, Brazil, saw countries commit to limiting the size and duration of this overshoot.
• The report warns of irreversible ecological losses and compounding costs, including faster sea-level rise and coral reef collapse, if the 1.5 degrees Celsius limit is breached.
• Current policies are projected to lead to a rise of about 2.6 degrees Celsius by 2100, while even national climate plans result in a peak of 1.8 degrees Celsius.

Detailed Insights:

• The "overshoot, peak, and decline" pathway aims to hold peak temperatures as low as possible after the breach and then bring them back below 1.5 degrees Celsius by 2100.
• UN Secretary-General Antonio Guterres stated that the pathway is "the best remaining option" and emphasized making the overshoot "as small and short as possible."
• COP30 marked the first time a Conference of the Parties text, the "Global Mutirão (collective effort)" decision, conceded the likelihood of a temporary 1.5 degrees Celsius overshoot.
• Beyond emission cuts, the report calls for a steep scaling up of nature-based removals, such as large reforestation programs, to mitigate warming.
• Compounding costs of exceeding 1.5 degrees Celsius include glacier loss exceeding a quarter of global mass by 2100 and declines of up to 14% in global food production by 2050.
• The report highlights rising odds of irreversible tipping points in critical systems like the West Antarctic and Greenland ice sheets, Atlantic Meridional Overturning Circulation, and the Amazon.
• The article notes that the United States formally exited the Paris Agreement and announced withdrawal from the UNFCCC, Intergovernmental Panel on Climate Change (IPCC), and Green Climate Fund in the context of the report's release.

Key Concepts Involved:

• Paris Agreement: An international treaty adopted in 2015, aiming to limit global warming to well below 2 degrees Celsius, preferably to 1.5 degrees Celsius.
• Overshoot, Peak, and Decline Pathway: A climate strategy acknowledging a temporary exceedance of a temperature target, followed by efforts to reduce temperatures.
• Nature-based Removals: Actions that protect, sustainably manage, and restore natural ecosystems to remove carbon dioxide from the atmosphere.
• Tipping Points: Critical thresholds in Earth's climate system where small changes can lead to large, often irreversible, shifts.