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1.5 is Dead: How Hot Will the Earth Get?

Ian Angus

2024 was the warmest year since records began being kept 175 years ago. According to the World Meteorological Organization’s latest State of the Global Climate report:

• Each of the past ten years set a new global temperature record.
• Each of the past eight years set a new record for ocean heat content.
• The 18 lowest Arctic sea-ice extents on record were all in the past 18 years.
• The three lowest Antarctic ice extents were in the past three years.
• The largest three-year loss of glacier mass on record occurred in the past three years.
• The rate of sea level rise has doubled since satellite measurements began.[1]

There is no room for doubt: Earth is getting hotter. The question now is how hot will it get?

In 2015, at the United Nations climate conference (COP21) in Paris, 196 countries promised to “significantly reduce the risks and impacts of climate change” by “holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels.”[2]

A May 2024 survey asked 380 leading climate scientists whether the 1.5°C goal will be achieved. Only 6% said yes. 77% believe that global temperatures will rise more than 2.5°C by 2100, and 42% think the increase will be over 3°C.[3]

Future Earth, the international agency that coordinates global change research, warns that “overshooting 1.5°C is fast becoming inevitable.”

Decades of insufficient action for mitigating GHG emissions have set the world on the current trajectory to overshoot the internationally agreed target of limiting global warming to 1.5°C, enshrined in the Paris Agreement. National mitigation commitments are inadequate to even stay well below 2°C of global warming, creating unacceptable risks for human societies and ecosystems, with vast yet unequally distributed costs. This is a dangerous gamble that could lead to irreversible impacts for life on Earth, including devastating loss of biodiversity and a rising risk of triggering climate tipping points.[4]

Under the Paris Agreement, each country decides its own targets, called National Determined Contributions. According to the UN, there is a “massive gap” between the treaty’s objectives and the policies actually adopted by the largest polluters.

Collectively the NDC targets of the G20 are far from the average global percentage reductions required to align with 2°C and 1.5°C scenarios…

A continuation of the mitigation effort implied by current policies is estimated to limit global warming to a maximum of 3.1°C (range: 1.9—3.8) over the course of the century.[5]

This isn’t just a matter for future concern. 2024 was the hottest year since preindustrial times, and the first full year in which the average temperature passed the 1.5°C target. Actually exceeding the Paris goal requires at least a decade, but 2024 is almost certainly an indicator of what is to come, especially if, as noted climate scientist James Hansen argues, global warming is speeding up.

Therefore, we expect that global temperature will not fall much below +1.5°C level, instead oscillating near or above that level for the next few years, which will help confirm our interpretation of the sudden global warming. High sea surface temperatures and increasing ocean hotspots will continue, with harmful effects on coral reefs and other ocean life. The largest practical effect on humans today is increase of the frequency and severity of climate extremes. More powerful tropical storms, tornadoes, and thunderstorms, and thus more extreme floods, are driven by high sea surface temperature and a warmer atmosphere that holds more water vapor. Higher global temperature also increases the intensity of heat waves and—at the times and places of dry weather—high temperature increases drought intensity, including ‘flash droughts’ that develop rapidly, even in regions with adequate average rainfall.[6]

It has become common in scientific reports to assert that it’s still “technically possible” to meet the Paris objectives. That’s just barely true, but unlikely. The United Nations Environment Program Emissions Gap Report tells us just what needs to be done:

Specifically, if action in line with 2°C or 1.5°C pathways were to start in 2024, then global emissions would need to be reduced by an average of 4 and 7.5 per cent every year until 2035, respectively. If enhanced action… is delayed until 2030, then the required annual emission reductions rise to an average of 8 per cent and 15 per cent to limit warming to 2°C or 1.5°C, respectively.[7]

No matter what you think of those numbers, the fact is that none of that is going to happen. Greenhouse gas emissions are going up, not down, and not one G20 government has shown any willingness to even slow down the increase, let alone go into reverse. The United States has withdrawn from the UN climate process, and Trump has cancelled climate change programs. If other big emitters don’t take up the slack, or just fail to carry through on their Paris Agreement commitments, 3°C will be passed, probably sooner then the climate models project.

Andreas Malm and Wim Carton sum up where things stand today:

Promises were, after all, just that, and most were not backed up by measures that could take them out of the realm of ‘blah blah blah’, to use Greta Thunberg’s phrase. When in 2023, eight years after Paris, one scratched away at the net zero façade and summated all the actual efforts—not promises—in place across the globe, the sobering result was that the world was on track for 2.7°C; or, rounding the number, 3°C, meaning a warming twice as large as that which the global South had insisted on to stay alive. And we know that the warming does not produce a linear rise in damages: 3°C would be something far worse than just a doubling of the impacts at 1.5°C. But deep into the Paris era, this is where the world was heading.[8]

Notes

1. World Meteorological Organization, “WMO report documents spiralling weather and climate impacts”, (Press Release, March 18, 2025.

2. Paris Agreement, https://shorturl.at/w0KbU

3. Damian Carrington, “World’s top climate scientists expect global heating to blast past 1.5C target,” The Guardian, May 8, 2024.

4. Future Earth, The Earth League, WCRP. 10 New Insights in Climate Science 2023/2024, (Stockholm, 2023)

5. United Nations Environment Programme, Emissions Gap Report 2024, (Nairobi, April 2025), xii, xvii.

6. James E. Hansen, et al., “Global Warming Has Accelerated: Are the United Nations and the Public Well-Informed?” Environment: Science and Policy for Sustainable Development, February 2025.

7. UNEP, Emissions Gap Report 2024, (Nairobi, April 2025), xv.

8. Andreas Malm and Wim Carton, Overshoot: How the World Surrendered to Climate Breakdown, (Verso, 2024), 69.

(Ian Angus is editor of Climate and Capitalism. Courtesy: Climate and Capitalism, an eco-socialist journal.)

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‘Ticking Time Bomb’ of Ocean Acidification has Already Crossed Planetary Boundary, Threatening Marine Ecosystems: Study

Cristen Hemingway Jaynes

On the first day of the United Nations Ocean Conference in Nice, France, the findings of a new study have revealed that ocean acidification (OA)–which damages ecosystems like coral reefs–is not only getting worse, but crossed its “planetary boundary” roughly five years ago.

The findings came as a surprise, as scientists in a report published last year said OA was “approaching a critical threshold,” but had not yet crossed the boundary.

The nine defined planetary boundaries in which Earth can operate safely include climate change, freshwater use and OA.

“OA is the term given to the long-term shift of marine carbonate chemistry resulting primarily from the uptake of carbon dioxide (CO2) by the oceans, leading to an increase in ocean acidity and a decrease in carbonate ion (CO32−) concentration,” the authors of the study wrote.

OA can severely affect marine organisms through its direct impact on physiology, growth, survival and reproduction.

The researchers pointed out that ocean conditions vary widely across the world, with OA levels in tropical regions over two times as high as in polar regions.

“Looking across different areas of the world, the polar regions show the biggest changes in ocean acidification at the surface. Meanwhile, in deeper waters, the largest changes are happening in areas just outside the poles and in the upwelling regions along the west coast of North America and near the equator,” said lead author of the report Helen Findlay, a professor at the United Kingdom’s Plymouth Marine Laboratory (PML) and chair of the North-East Atlantic Ocean Acidification Hub, in a press release from PML.

The study, led by PML, the National Oceanic and Atmospheric Administration in the United States and Oregon State University’s Cooperative Institute for Marine Resources Studies (CIMERS), said OA’s threat to marine ecosystems globally is much more widespread than previously believed.

The research team used the most recent chemical and physical measurements of the upper ocean, along with studies of marine life and advanced computer models to conclude that by 2020, average ocean conditions globally were already very near–and in some regions had already surpassed–the OA “danger zone.”

“Most ocean life doesn’t just live at the surface—the waters below are home to many more different types of plants and animals. Since these deeper waters are changing so much, the impacts of ocean acidification could be far worse than we thought. This has huge implications for important underwater ecosystems like tropical and even deep-sea coral reefs that provide essential habitats and nursing refuge for many species, in addition to the impacts being felt on bottom-dwelling creatures like crabs, sea stars, and other shellfish such as mussels and oysters,” Findlay explained.

Professor Helen Findlay working in the laboratory to investigate the impacts of climate change and ocean acidification on marine organisms and ecosystem functioning Plymouth Marine Laboratory

The team discovered that roughly 60 percent of deeper ocean waters–down to approximately 656 feet–had crossed the planetary boundary for OA–compared with 40 percent at the surface. The increase in acidification has enormous implications for the survival rates of many sea creatures, particularly those who build their skeletons or shells from calcium carbonate.

Some subtropical and tropical coral reefs have already lost 43 percent of suitable habitats, while pteropods, a main food web species in the polar regions–also known as “sea butterflies”–have lost as much as 61 percent of their habitat. Additionally, 13 percent of the habitats of coastal shellfish species have been lost worldwide.

Based on the findings, the scientists recommended that a change be made to the previous safety limit of a 10 percent deviation from pre-industrial levels being harmful to ocean ecosystems, as the entire surface of the ocean had already exceeded the stricter limit by about the year 2000.

“Ocean acidification isn’t just an environmental crisis—it’s a ticking time bomb for marine ecosystems and coastal economies. As our seas increase in acidity, we’re witnessing the loss of critical habitats that countless marine species depend on and this, in turn, has major societal and economic implications.” said Steve Widdicombe, a professor at PML who is co-chair of the Global Ocean Acidification Observing Network, one of the focuses of the UN’s sustainable development goal of addressing and minimizing the effects of OA.

“From the coral reefs that support tourism to the shellfish industries that sustain coastal communities, we’re gambling with both biodiversity and billions in economic value every day that action is delayed,” Widdicombe added.

The authors of the study suggested conservation measures should be directed toward to species and regions that are most vulnerable to acidification. They also emphasized the importance of suitable management measures or protection of areas that are the least compromised by acidification to ensure their longevity.

The newly identified subsurface water impacts highlight a pressing need to safeguard mid-water habitats and their marine life. The researchers stressed the importance of improved approaches to addressing OA, as well as other ocean pressures, to better support stronger ecosystem resilience.

“This report makes it clear: we are running out of time and what we do—or fail to do—now is already determining our future,” said Jessie Turner, director of the International Alliance to Combat Ocean Acidification, who was not part of the study, as The Guardian reported.

We are coming to terms with an existential threat while grappling with the difficult reality that much suitable habitat for key species has already been lost. It’s clear that governments can no longer afford to overlook acidification in mainstream policy agendas.

The study, “Ocean Acidification: Another Planetary Boundary Crossed,” was published in the journal Global Change Biology.

(Cristen Hemingway Jaynes is a writer of fiction and nonfiction with an MA in Creative Writing from Birkbeck, University of London, and a JD and an Ocean & Coastal Law Certificate from University of Oregon School of Law. Courtesy: EcoWatch, a long-time leader in environmental news that was founded in 2005.)