Climate Change is Now Irreversible in the Short Run, Planet Earth is on the Edge – Part 1

Given the current trajectory of global development, global warming cannot be halted to a 1.5 °C temperature rise over pre-industrial times. Many climate-related impacts will not reverse in the short run. They will take centuries or even millennia to revert, and some will not reverse at all. Climate change has brought Planet Earth to the edge of a tipping point that could regress human society or even collapse it.

Introduction

I endorse the broad trajectory of Sanjeev’s statement, “Irreversible Climate Change: An International Statement of Dismay,” and my statement below adds to Sanjeev’s statement with my understanding of the issue. There are a few points in Sanjeev’s statement that I may not fully agree with, e.g., that green hydrogen is a good alternative energy source. But these differences do not detract from the broad agreement I have with the main thrust of his statement.

My statement will be published in 6 parts:

1. Climate change is now irreversible in the short run. Planet Earth is on the edge
2. South Asia is one of the two most vulnerable areas to climate change impacts. It will burn, get parched, drown, and get washed away
3. What happened in COP 30? Should it be renamed “Circus of Parties 30?”
4. The world is on fire, but green capitalism is fiddling on the roof; it neither has the will nor the wherewithal to tackle the climate crisis
5. Eco-socialism-anarchism is the alternative to capitalism. But who will be the change agents to transition to a sustainable and equitable society? How long will we work in isolated silos?
6. Are we willing to dialogue about what to do before time runs out? A suggested draft programme of action for change for discussion

Climate Change is Now on an Irreversible Course in the Short Run–Mounting Evidence

Emissions are still rising

In the last two decades, global carbon dioxide (CO₂) emissions from fossil fuel burning, cement industries and land use change rose from 35.3 GtCO₂ in 2005 to 41.4 GtCO₂ in 2024 (Global Carbon Budget). Fossil CO₂ emissions account for ~69% of the total emissions, driven primarily by energy and industrial sectors.

Global greenhouse gas (GHG) emissions were 57.7 GtCO2e in 2024, a 2.3% increase from 2023. Deforestation and land-use change accounted for 53% of the overall emissions increase (UNEP, 2025, Emissions Gap Report 2025).

Except for the EU, the emissions of the five of the six largest emitters (China, the USA, India, the EU, Russia, and Indonesia) increased in 2024. India had the highest absolute growth in emissions, followed by China and Indonesia.

To remain within the 1.5 ^oC warming red line in 2100, emissions should drop by 8-10% pa between now and 2035 (UNEP, 2025. Emissions Gap Report 2025). Given the growing gap between emissions and what is desired to remain under the desired 1.5 ^oC warming, such a drastic drop is considered not feasible.

Warming continues relentlessly

The global average atmospheric warming above pre-industrial levels was 1.45 °C in 2023 and 1.55 °C in 2024, the latter being the hottest year in the last 175 years (WMO, State of the Global Climate 2023 and 2024).

Planet Earth is on Edge; Many Climate Impacts Cannot be Reversed in the Short Run

Global warming is predicted to have many impacts that will persist for a long time, even centuries after carbon emissions are reduced. The predictions for some climate impacts, and the time for recovery, if possible at all, for a ~3 ^oC warming are described below.

Loss of coral reefs

Warm-water coral reefs are in rapid decline. Over 99 % of warm-water coral reefs are expected to experience very frequent severe bleaching and be functionally lost already by a ~2 °C warming. At 3 °C, global coral reef collapse will happen.  Coral reefs are very likely to undergo irreversible phase shifts beyond ~1.5 °C. Once species are extinct, full ecological recovery is impossible(AR6).

Melting of the Greenland Ice Cap

Between 1992-2018, Greenland lost 3.8 trillion tonnes of ice, raising the global sea level by 10.6 mm. Greenland tipping threshold is somewhere between ~1–3 °C warming; a sustained 3 °C warming will cause a large, mostly irreversible, mass loss over the coming millennia (Multistability and transient response of Greenland Ice). If fully melted, the Greenland ice sheet could raise global sea levels by ~7.4 m. Even if temperatures fall subsequently, the Greenland Ice Cap is unlikely to fully recover even after 10,000 years, making this impact virtually irreversible (Greenland ice loss much faster than expected).

Weakened Atlantic Meridional Overturning Circulation

If large volumes of meltwater from the Greenland ice sheet enter the North Atlantic Ocean, the surface salinity of the Labrador and Irminger seas will be lowered. That will weaken the sinking branch of the Atlantic Meridional Overturning Circulation (AMOC), a circulating surface and deep-sea ocean current that connects the major oceans of the world, and distributes heat from the equator towards the poles and influences climate on all the continents. A weaker AMOC will alter global heat distribution and regional climate and storm patterns, i.e., a weakened AMOC has the potential to alter global climate.

By 2100, in a high emissions scenario, the AMOC is predicted to weaken by 24-39%. Even if the emissions decrease, the AMOC is expected to weaken substantially (Climate impact of a weakened AMOC in a warming climate). A recent study finds the tipping threshold for AMOC collapse to be around 3 °C warming with a lower bound of ~2.2 °C (Substantial Risk of 21^st Century AMOC Tipping even under Moderate Climate Change).

If there is no AMOC collapse, it may partially recover in 100-200 years, but may not recover fully to its original strength, even after a millennium. However, if it collapses, it may recover partially after centuries, and the collapse may be irreversible in human timescales.

Methane emissions from the Arctic region

Warming has begun to release methane (CH₄) from the permafrost in Siberia, Northern Canada and Alaska, and from undersea methane hydrates, where an estimated 4,000 GtC are stored (CH₄ hasa global warming potential that is 1-2 orders of magnitude higher than that of CO₂).  In a 3–5 °C warming, up to ~90 % of near-surface permafrost area can thaw in many regions, turning them into net carbon sources. Permafrost carbon losses are irreversible even on centennial to millennial timescales (Review of permafrost science in IPCC’s AR6 WG1).

Glacier retreat

A large fraction of the world’s ~215,000 glaciers are already committed to loss due to warming. At a ~2.7–3 °C warming, up to ~75 % of these glaciers and a large share of ice volume will be eventually lost (IPCC). Even if temperatures drop below 1.5 ^oC warming, changes of glacier mass will be irreversible for centuries (Irreversible glacier change and trough water after overshooting 1.5 ^oC).

Sea level rise

A warming of ~3 °C by 2100 will cause a global mean sea-level rise of ~0.6–1.0 m(AR6). After a 3 °C warming peak, sea level will keep rising for millennia, potentially reaching several metres higher even if temperatures fall modestly (The multi-millennial sea level commitment of global warming). Sea rise will leave thousands of climate refugees permanently homeless in the small island nations and low-lying lands in countries such as Bangladesh.

Ocean acidification

Ocean pH has already fallen by ~0.1 pH since pre-industrial; continued high emissions up to 2100 will drop it further by 0.1–0.3 pH (NOAA). This will severely impact calcifying organisms (corals, molluscs, some plankton) and the ecosystem structure (Ocean acidification and climate change: advances in ecology and evolution).

Fires

Wildfire risk and burned area increase strongly with warming. The global annual area of forest disturbance due to fire in 2023 and 2024 was 36.6 and 38.3 million ha, respectively. Compared to the 2002–2022 average, annual forest disturbance due to fire, the 2023–2024 disturbance was 2.2 times higher globally, and 3 times higher in the Tropics. More than 25% of all 2024 forest disturbance from fire occurred in tropical forests (Unprecedentedly high global forest disturbance due to fire in 2023 and 2024).

While the frequency of fires may decline rapidly with a return to pre-industrial climate, repeated burning will trigger ecosystem changes—e.g., boreal forest changes to shrubland/grassland, Amazon forest dieback in some regions may be hard or impossible to reverse on timescales less than centuries (IPCC AR6).

Drought

The WMO has identified global drought hotspots all across the world: in Africa, in the Mediterranean region, in South America, and in South and Southeast Asia. Data on drought trends are scanty. One study (Global Health Emergencies of Extreme Drought Events) estimates that between 2000 and 2023, 1.6 billion people were affected by drought globally. FAO notes that drought is the leading cause of agricultural loss and affects the livelihoods of large parts of the population, especially in developing countries. A consequence of drought is global hunger, and with that, global unrest and global conflict.

With rising emissions, droughts are expected to increase in intensity and severity in future (Global drought trends and future projections). A 3 ^oC warming will increase the frequency of drought. While drought frequency may decrease when temperatures drop, the consequences of drought–groundwater depletion, soil degradation, vegetation changes, and desertification are much slower to reverse, possibly centuries, if reversal happens at all.

Storms

The increase in intensity and frequency of storms and superstorms around the world is a result of oceanic warming. The average number of Category 4 (200-250 km/hr windspeeds) and Category 5 (>250 km/hr windspeeds) storms has increased from an average of 15 storms per year during the period 2000-2004 to an average of 21 such storms per year during 2020-2024 (IBTrACS).

Storms correlate directly with global temperature and ocean heat content. When temperatures stabilise or decline, storm patterns will adjust over a few decades, but with permanent changes to coastlines, infrastructure and ecosystems.

Floods & landslides

The year 2021 saw the second-largest number of floods recorded globally in the period 1990 to 2023 (WMO). In 2020, South Asia had devastating floods, and in 2022, Pakistan floods inundated a third of the country and affected 33 million people. In 2023, Italy was affected by floods and in the next year, Spain was inundated. In the period 2022-24, Niger, Chad, Nigeria, Somalia, and Tanzania experienced floods. India, in particular, has experienced floods and landslides after heavy rainfall events, which have caused heavy loss of life, e.g., more than 300 lives were lost in the 2024 Wayanad Landslide Disaster.

At 2-4 ^oC warming, heavy rainfall events are expected to become roughly 1.7–2.7 times more frequent and 14–30% more intense (IPCC). As warming decreases, extreme rainfall events will revert to the pre-industrial era pattern over a period of a few decades, but changes to river morphology, sedimentation, changes in floodplains, and loss of wetlands imply that pre-industrial flood risk is not recoverable just by changing the climate.

Heat waves

Heat is among the biggest direct health risks, especially in South Asia, the Middle East, and parts of Africa (WHO-10 Key Heat Health Messages from the IPCC AR6 Report). Once global mean temperatures peak and decline, heatwaves will decline on decadal scales, but a return to pre-industrial heat risk levels is impossible unless all warming is reversed.

Loss of Arctic ice

The Arctic ice extent in September of any year, when it is at its minimum, shrank from 6 million km² in 2004 to 4.28 million km² in 2024, a 28% loss in area in 20 years (National Snow and Ice Data Center, CIRES, University of Colorado, Boulder).  At 3 °C warming, the Arctic will be practically sea ice-free in September in most years, with progressively longer ice-free seasons with more warming (AR6).

Loss of Arctic ice extent changes the reflectance (albedo) of the Arctic waters, resulting in significantly greater absorption of incoming radiation in the Arctic Ocean and adjacent seas like the Kara Sea off Siberia.

Sea ice is a fast-response cryosphere component. If atmospheric CO₂ is brought back down, Arctic sea ice cover can regrow on decadal scales (Regionally-Dependent Arctic Sea Ice Recovery to CO₂ Removal).

Climate change-related health effects

Climate change has already increased the burden of heat-related mortality, vector-borne, food, and water-borne diseases. At 3 ^oC warming, climate-related health risks will increase further (IPCC).

If the climate cools, some vectors and pathogens could decrease over decades, but they do not contract fully. Climate-related health risks can be reduced substantially within decades through adaptation and mitigation measures, but a return to pre-industrial disease patterns is impossible, as the ecological and social systems would have changed significantly.

Other impacts

There are many other climate-related impacts for which forecasting how they may pan out is beyond the scope of this document, e.g., an increase in desertification, which may take centuries to reverse, if it reverses at all, an increase in marine heatwaves, loss of food and water security, social changes, indebtedness, political changes within and between countries.

After a  3 °C temperature rise by 2100, even if emissions fall, the climate system will not revert to its original state. Some variables may improve noticeably within a human lifetime after net-zero carbon emissions are achieved, but the slow components will lock in a transformed planet for many generations. The choice to make in this century is how much irreversible change are we willing to commit to, not whether we can go back to 1750.

Assuming emissions decline after 2100, net-zero or net-negative CO₂ is achieved, the timelines for major impacts are as follows:

Timelines for major climate change impacts

Though climate change will impact the entire earth and all of humanity, people in the most geographically vulnerable areas, e.g., small island nations, and those who are economically weak, will be hit the hardest.

South Asian People’s Action on Climate Crisis (SAPACC)

The South Asian People’s Action on the Climate Crisis (SAPACC) is a platform of workers, farmers, youth, gender equality, women, and environmental organisations who are interested in working together on issues related to sustainability and equity. SAPACC was set up in 2019 by people from Bangladesh, India, Nepal and Sri Lanka.

Submissions to SAPACC Dialogues

Those interested in responding to this post or making a fresh submission on a topic related to sustainability and equity may send it to [email protected]. Views expressed in the submissions to SAPACC Dialogues may not necessarily agree with SAPACC’s core beliefs.

While we have not yet decided on the maximum length of the submissions, they may be 500 words upwards. For the time being, we can handle submissions in English.

SAPACC’s core beliefs

• Sustainability: Developed nations must pledge to become net carbon negative in consumption emissions by 2035-40 to create space for developing nations to fully decarbonise by 2045-50.

Note: Decarbonisation must focus primarily on: a) Mitigation, focused on the reduction of consumption levels in the Global North, and supply-side management, leaving >90% of the remaining fossil fuel reserves in the ground;  b)  Sequestration, focused on Nature-based Solutions that centre climate and social justice. In addition, decarbonisation strategies must eschew failed, untested, hypothetical market-based solutions and techno-fixes. Through these means, gross global consumption should be reduced to sustainable levels, the measure for which should be a quantifiable justice-centric sustainability index.

• Environmental justice: a) Responsibility for loss & damage: Nations/regions should take responsibility for climate change impacts attributable to them—displacement, property loss, etc—in proportion to their cumulative emissions (emissions from 1750-to date); b) Sharing benefits and risks equitably: Engineering and administrative controls should be put into place (e.g., global warming mitigative and adaptive measures, facilitating population migration where risk becomes high) such that all people of the world face roughly the same degree of risk from the impacts of GHG emissions; and the wealth created by the use of fossil fuels are distributed equally to all people of the world.

• Equity: The ratio of the maximum income consumption for all people in the world should be~5

• Decentralisation, democratic, transparent governance: Governance should be decentralised and democratic; all governance information should be in the public domain.

• Environmental remediation: Degraded land, water, air, and, to the extent possible, biodiversity should be remedied.

• Natural resource sharing: To engender global peace, people should share natural resources cooperatively and equitably as usufruct rights (and not ownership rights).

Sagar Dhara Member of the most ferocious predator that stalked Earth—humans; Male; Upper caste & class; College educated; City slicker. Email: [email protected]