A ‘sinking’ capital: Crossing climate thresholds
Global heating reaching 1.8 degrees Celsius may now seem unavoidable in the next few years, meaning that for the first time since the United Nations Intergovernmental Panel on Climate Change began warning about the catastrophic impacts of a human-induced climate crisis, humanity is about to cross multiple tipping points that could cause irreversible damage.
In my previous column (see “Navigating the global warming ‘overshoot,’” 10/22/26), I discussed the UN Environment Program’s (Unep) “Limiting Overshoot Spotlight Report,” which warned that “under current policies and alternative near-term trajectories, exceedance of 1.5 degrees Celsius is now widely assessed as unavoidable.”
The Paris Agreement is a legally binding international treaty on climate change adopted by 195 countries in 2015. Unep’s report warned that despite progress in climate change mitigation, failing to expedite global action to cut greenhouse gas (GHG) emissions from fossil fuels could push global warming past the Paris Agreement’s landmark 1.5 degrees Celsius goal. The peak temperature rise could reach 1.8 degrees Celsius in the next few years. “Even an optimistic scenario of current government pledges (full implementation of all national climate plans plus meeting additional net-zero targets) puts expected peak temperature rise at 1.8°C,” Unep said.
After examining studies on peak warming and its attendant risks and impacts on our planet, Unep suggested an “overshoot, peak and decline” mitigation pathway for subsequent temperature decline, and adaptation and development approaches that could reverse this overshoot. (You can access the report here: https://tinyurl.com/2xfpuzj6). Burning fossil fuels such as coal, oil, and natural gas for electricity and heat, manufacturing and industrial production, and transportation drives about a third of global GHG emissions.
The Unep report is timely, calling for political will from governments worldwide to strengthen and sustain global climate action ahead of the UN Climate Change Conference in Antalya, Turkiye, scheduled for Nov. 9 to 20. “Today’s decisions are therefore critical: the lower the peak warming reached, the lower the risks faced by people, societies, economies and ecosystems,” Unep said.
The reverse is also true: “the shorter the duration of overshoot, the lower the probability of crossing irreversible thresholds and adaptation limits. The central message is clear: mitigation and adaptation must advance together. Overshoot is not an argument for resignation, but rather for urgency to action,” Unep added.
It’s important to reiterate that exceeding 1.5 degrees Celsius will not lead to any positive outcomes. We can expect faster sea level rise, a higher likelihood of coral reef collapse, impacts on food security and water supplies, more frequent and intense heat waves, droughts and flooding, and greater risks of pathogen spillover.
As an example, Unep pointed out that glaciers could lose more than a quarter of their mass by 2100, a scenario that could raise sea levels by 9 to 12.5 centimeters (cm) (assuming global warming of up to or less than +3 degrees Celsius). “There is also a higher risk of irreversible tipping points to global systems such as the West Antarctic and Greenland ice sheets, the Atlantic Meridional Overturning Circulation and the Amazon rainforest—which would reshape the world forever,” it added.
But other climate scientists and researchers say that climate tipping points (CTPs)—planetary thresholds beyond which changes in part of the climate system become self-perpetuating—become likely even within the Paris Agreement’s target range of 1.5 to 2 degrees Celsius of warming. These CTPs include the “collapse of the Greenland and West Antarctic ice sheets, die-off of low-latitude coral reefs, and widespread abrupt permafrost thaw” (source: tinyurl.com/33wu5afy).
Faster sea level rise. Such a scenario will accelerate sea level rise—depending on the rate of global warming—and drive a slow but steady encroachment of seawater into outlying parts of islands and coastal communities, including archipelagos such as the Philippines.
Faster sea level rise puts Manila Bay reclamation projects and similar projects in island provinces, such as Masbate and Cebu, at great risk, and some ecosystem losses that affect water and food security could become irreversible.
Active reclamation and waterfront projects in Pasay, Manila, and Bulacan will face the double whammy of localized ground subsidence (sinking ground) and sea level rise, which is three times faster than the global average (21 to 24 cm/8 to 9 inches since 1880)—up to 9 cm a year in Metro Manila, according to one study. In 2023, the global average hit a new record high—101.4 millimeters (3.99 inches) above the 1993 levels (source: https://tinyurl.com/ys45vfjd).
Government planners and private developers should read the writing on the wall.
Beyond the high cost of developing these reclaimed lands to address these environmental vulnerabilities, the biggest problem is seasonal flooding—water displaced by reclaimed land must go somewhere else, causing prolonged inland flooding and increasing tidal heights.
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