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For the first time in recorded history, Earth’s average global temperature exceeded 1.5°C above pre-industrial levels for the entire calendar year 2024, a threshold scientists have long warned would mark a turning point in the climate crisis. This is not a fleeting anomaly; according to a recent study, Earth has likely entered a 20-year period where global temperatures will consistently remain at or above this level. The Paris Agreement was designed to prevent such an outcome, aiming to keep global warming well below 2°C while striving to limit it to 1.5°C, but with emissions still rising and climate policies lagging, this goal now hangs by a thread. The study’s findings suggest that unless immediate and drastic emission cuts are implemented, what was once considered a critical warning line may soon become our new climate reality.
The Science Behind the 1.5°C Threshold
The 1.5°C threshold is not just a symbolic number—it represents a scientifically determined tipping point beyond which climate impacts become significantly more severe and potentially irreversible. The Paris Agreement, adopted in 2015, set out to keep global temperature rise well below 2°C and to pursue efforts to limit the increase to 1.5°C above pre-industrial levels. This target was based on research from the Intergovernmental Panel on Climate Change (IPCC), which warned that even half a degree of additional warming beyond 1.5°C could cause devastating consequences. At 1.5°C, extreme heatwaves, droughts, and storms will intensify, sea levels will rise, and coral reefs will suffer massive die-offs. However, at 2°C, these impacts are significantly worse—coastal cities will face more frequent and severe flooding, heatwaves will threaten millions of lives annually, and ecosystems such as the Amazon rainforest may reach collapse points.
The Paris Agreement defines pre-industrial levels as the average global temperatures between 1850 and 1900. This means the 1.5°C threshold is measured relative to those historical baselines when human-induced greenhouse gas emissions were significantly lower. However, the agreement tracks long-term temperature trends, usually measured over 20-year periods, rather than focusing on single-year exceedances. A recent study published in Nature Climate Change argues that when global temperatures exceed a critical warming level for a single year, it usually happens within a 20-year period where that level becomes the new normal. This means that 2024’s record-breaking temperatures are not just an anomaly but an early signal that Earth has entered a long-term period of sustained warming at or above 1.5°C. The study highlights that unless immediate and deep emission cuts are implemented, global warming will continue accelerating, further increasing the risks of surpassing the Paris Agreement’s most critical threshold.
What’s Driving This Warming—El Niño or Human Activity?
Natural climate variability and human-induced global warming influenced the record-breaking global temperatures in 2024, but the latter remains the dominant force behind long-term trends. The study finds that 2023 had already reached 1.43°C above pre-industrial levels, and 2024’s spike to 1.55°C was driven mainly by human-caused climate change, with El Niño providing an additional boost.
The primary driver of rising global temperatures is the increasing concentration of greenhouse gases (GHGs) in the atmosphere, primarily from burning fossil fuels such as coal, oil, and natural gas. Carbon dioxide (CO2) levels have risen by around 50% since the pre-industrial era, reaching record highs of over 420 parts per million (ppm). Additionally, methane (CH4), a far more potent greenhouse gas, has surged due to agriculture, livestock, and fossil fuel extraction. These gases trap heat within the Earth’s atmosphere, intensifying the greenhouse effect and driving long-term warming trends. According to the study, even without El Niño, human-induced warming had already pushed Earth close to the 1.5°C threshold.
However, the El Niño phenomenon played a role in pushing 2024’s temperatures even higher. El Niño is a natural climate pattern that temporarily raises global temperatures by warming the Pacific Ocean’s surface waters, releasing excess heat into the atmosphere. The 2023–24 El Niño event was powerful, amplifying global temperatures and leading to widespread climate extremes. However, scientists emphasise that El Niño’s effect is short-term and cyclical, whereas human-driven climate change is persistent and accelerating. Even if La Niña—a cooling phase that follows El Niño—briefly moderates temperatures in the coming years, the underlying warming trend will continue rising unless strong mitigation measures are implemented. The study clarifies that El Niño may have been the match, but human-caused climate change provided the fuel.
Are We Still on Track to Meet Climate Goals?
The grim reality is that the world is not on track to meet the Paris Agreement’s temperature goals. Despite global pledges to reduce emissions, greenhouse gas levels have continued to rise rather than fall, making it increasingly difficult to limit warming to 1.5°C. The study warns that unless “very stringent climate mitigation” efforts are undertaken immediately, the 1.5°C threshold will be fully locked in, making it almost impossible to reverse course.
Current policies and emissions trajectories put the world on track for a 2.7°C rise in global temperatures by 2100, leading to catastrophic climate impacts. Even under optimistic scenarios, where all announced government climate pledges are successfully implemented, we are still looking at a 2.1–2.4°C increase, far beyond the Paris Agreement’s goal. To limit warming to 1.5°C, global emissions would need to fall by nearly 50% by 2030 and reach net-zero CO₂ emissions by 2050—an ambitious but necessary target.
However, recent years have shown that climate action is still lagging what is needed. The continued expansion of fossil fuel projects, slow policy implementation, and insufficient global cooperation have created major roadblocks to meeting these targets. Some progress has been made—investments in renewable energy are at an all-time high, and countries like the United States, China, and the European Union have introduced more aggressive climate policies—but these actions still fall short of what is needed to prevent long-term overshoot of the 1.5°C threshold. The study’s findings serve as a clear warning: unless drastic action is taken now, the world will soon face a future where 1.5°C is not just a breached threshold but a permanently locked-in reality.
The Consequences of Long-Term 1.5°C Warming—What’s at Stake?
If global temperatures remain above 1.5°C for an extended period, the consequences will become significantly more dangerous, widespread, and irreversible. The study emphasises that the climate impacts we witness—heatwaves, wildfires, floods, and sea-level rise—will only intensify as warming continues. One of the most immediate threats is extreme weather. With continued warming, heatwaves will become more frequent and severe, affecting billions of people worldwide. Countries already struggling with water scarcity will experience longer and more intense droughts, reducing agricultural yields and threatening food security. Meanwhile, hurricanes and typhoons will increase frequency and intensity, causing more devastating floods and destruction in coastal regions.
Rising sea levels are another significant consequence. With the accelerated melting of glaciers and polar ice caps, low-lying coastal cities like Jakarta, Miami, and Dhaka face the risk of permanent inundation, forcing millions to relocate. Entire island nations could disappear beneath the waves if warming is not curbed. Ecosystems are also at severe risk. Coral reefs, home to over 25% of marine species, could face near-total extinction at sustained 1.5°C warming. Forests and wetlands, crucial for carbon storage and biodiversity, are also threatened, increasing the risk of ecosystem collapse.
Meanwhile, vector-borne diseases like malaria and dengue fever will spread to new regions as rising temperatures create favourable conditions for disease-carrying insects. The study emphasises that every fraction of a degree of warming matters. The risks at 1.5°C are already severe, but if temperatures rise beyond 2°C, the consequences become far more catastrophic and irreversible. The only way to avoid these long-term dangers is through urgent, global climate action—and the time to act is now.
References:
https://www.nature.com/articles/s43247-024-01274-1
https://www.nature.com/articles/s41558-025-02246-9
http://climate.copernicus.eu/copernicus-2023-hottest-year-record
Chapter 7 – Sea Level Rise and Ice Melt
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