Lethal Humidity Global Council highlights escalating threat of humid heatwaves at UNGA

23 Sept 2025 – A global coalition of leading climate scientists, public health experts, economists, and policymakers will reconvene today on the sidelines of the UN General Assembly (UNGA) to confront one of the most urgent and under-recognised climate threats: lethal humidity.

Convened by Minderoo Foundation and launched at UNGA in 2024, the Lethal Humidity Global Council (LHGC) brings together experts to drive research on rapidly rising heat and humidity, which is lethal to humans when it passes a certain threshold. Due to humanity’s continued burning of fossil fuels, lethal conditions already exist on Earth and are becoming more widespread, prolonged and frequent.

The LHGC was created to quantify the impacts of lethal humidity on survival, health, food security and human migration, building a foundation for large-scale policy solutions that address the threat of fossil fuel use. LHGC members hold affiliations with leading institutions globally, including Harvard, NASA, Oxford, Cambridge, Australian National University, the Indian Institute of Technology and Tsinghua University.

This year, the LHGC will gather aboard the Fortescue Green Pioneer, the world’s first green ammonia dual-powered vessel, which has docked in New York City for Climate Week.

The New York event will feature a keynote by Dr Andrew Forrest AO and an update on the state of the science by Dr Colin Raymond, the author of one of the seminal science papers on lethal humidity in 2020, which demonstrated that lethal conditions – previously thought to emerge mid-century – already existed. The following panel discussion will feature leading experts actively working on the science that will quantify the true impact of lethal humidity in countries such as India.

The conversation will highlight a range of threats posed by increasing lethal humidity events, from global heat thresholds to cascading impacts on health, migration, and food systems – underscoring the urgent need for global action and solutions.

As low-lying atoll states, Pacific nations are some of the world’s vulnerable to climate impacts, including humid heatwaves. Tuvalu’s Minister for Home Affairs, Climate Change and Environment, the Hon. Dr Maina Talia, will address attendees on the existential threat his nation faces from worsening heat and rising seas.

Scientific projections suggest Tuvalu could become uninhabitable by 2050, a reality already shaping policy with over 80 per cent of Tuvalu’s population applying for the world’s first climate migration visa as of July this year.

“There is another invisible threat closing in: lethal heat and humidity,” Dr Talia said. “Scientists warn that when temperatures and humidity climb beyond a critical threshold, the human body can no longer cool itself. This is not just uncomfortable. It is deadly. Death can occur within hours – even for young, healthy people.

“We must be clear about what is driving this. This danger is not random. It is the direct result of burning oil, gas, and coal. Fossil fuels are responsible for 86 per cent of carbon pollution over the past decade. They are the root cause of the climate crisis and are triggering this lethal heat.”

The urgency of the issues confronted by the LHGC was reinforced this month by a new study from European and US climate researchers which directly linked the deadliest climate disasters – heatwaves, many of which are exacerbated by humidity – to major fossil fuel companies and their products.

“It’s getting harder and harder for fossil fuel companies, and the governments that enable them, to argue their business isn’t putting lives in jeopardy,” Dr Forrest said. “What was once excused as lazy inaction will soon be recognised for what it truly is: culpable negligence.

“The Lethal Humidity Global Council was created to provide further scientific evidence that climate change will result in catastrophic outcomes, including loss of life, if the world does not start cracking down on emissions and the companies responsible for them.”

Holly Buschman, Executive Director of Natural Ecosystems at Minderoo Foundation, added: “Lethal humidity is one of the clearest examples of how climate change is already reshaping lives and livelihoods. By convening a global coalition of leading scientists, health experts, economists and policymakers, we’re helping connect world-leading science with the realities faced by vulnerable communities.

“Our focus is on generating the evidence and partnerships needed to inform practical responses, while addressing the root cause – the continued burning of fossil fuels.”

The LHGC is funding a suite of pioneering projects, including:

A global early warning system for deadly humid heatwaves, led by researchers at Oxford, the Australian National University, Monash University and the University of New South Wales, using machine learning to forecast excess mortality weeks in advance.

One of the largest studies ever conducted to map real-world exposure and health impacts of lethal humidity among working women in informal economies, with a focus on how housing and buildings amplify the lethality of humid heat.

The LHGC is also advocating for a shift from “net zero” to Real Zero – a call to eliminate fossil fuel emissions entirely, without reliance on offsets or carbon capture.

This year’s event builds on momentum from UNGA 2024, where Minderoo Foundation committed A$6 million to advance research into lethal humidity.

“Lethal humidity is not just a scientific phenomenon. It’s a human crisis,” Dr Forrest said.

“We must act now to protect the world’s most vulnerable and prevent irreversible harm.”

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