Eleven Warmest Years, One Persistent Gap
Eleven warmest years, one persistent gap
This morning I want to speak, firstly, as a meteorologist. There are many of us in the room — from the Thai Meteorological Department, the UK Met Office, PAGASA in the Philippines. Find one during your coffee break today.
We fall in love with the weather early in our lives — some of us awestruck by a hailstorm or a cyclone, some of us drawn to the certainty that math and physics can bring to a chaotic system. Turn a cyclone into equations, and you feel like you have some control over it, because you can predict what comes next.
But anyone who has studied meteorology learns that the control is limited. The atmosphere is chaotic. Every gain in forecast skill — better observations, better models, decades of research — still run into the same uncomfortable truth: there will always be some chaos left to contend with.
What meteorology has always been about, from the start, is using that imperfect prediction to protect people anyway — at sea, in our food systems, in the air. Not just skill, but the judgment to act on it in time.
This century, we're confronting a new kind of chaos — one that is human-driven, but one we can still make progress on. That's what brought us to this room. I want to start with what we know to be true, as meteorologists and as Earth scientists.
The warmest eleven years humanity has ever measured
Every March, WMO publishes the State of the Global Climate report. Here is what we observed this year: the eleven years from 2015 to 2025 were the eleven warmest years humanity has ever recorded. And 2025 alone was about 1.43 degrees Celsius above the pre-industrial average, despite La Niña, which normally exerts a slight cooling influence on global temperatures.
Even with that natural reprieve, 2025 still ranked among the warmest years on record. Our baseline has shifted.
That heat doesn't stay in the air. Ninety percent of it is absorbed by the ocean, which set a new record high for the ninth year running in 2025. A warmer ocean feeds a more volatile atmosphere. Cyclones crossing marine heatwaves tend to intensify faster, and here in Thailand, ocean heat helps shape the monsoon rainfall this region depends on..
The driver is not a mystery -CO2 concentration curve as background
None of this has a mysterious cause. Greenhouse gases: Carbon dioxide, methane, and nitrous oxide all reached their highest recorded concentrations again in 2024, the last year we have fully consolidated data — and the jump in CO2 from 2023 to 2024 was the largest single-year increase since modern measurements began in 1957.
We'd still have heatwaves and drought even without this rise. But with it, we're supercharging the ocean and the atmosphere — and meteorologists are racing to keep pace with heatwaves, tropical cyclones, and rainstorms intensifying faster than our historical baselines prepared us for.
The future of heat is already being written — and suffered
This average warming, as you know, is triggering more frequent and intense extreme events. This summer Météo-France's main network crossed the 40°C threshold 178 times between June and August 2026 — more than double the previous record years, 2003 and 2019, which saw 88 and 72 crossings respectively.
And in India and Pakistan this year their heat season saw unbelievable conditions, including a fifteen-day heatwave that hit northwestern India and Pakistan before the monsoon arrived. Ninety seven of the world’s hottest cities in May 2026 were located in India, where a brutal heatwave pushed temperatures above 45°C in many cities. In Karachi, Pakistan’s most populated city, temperatures reached 44C in May – the highest recorded there since 2018. Over the five years from 2020 to 2024, eighty-four percent of the life-threatening heatwave days people experienced worldwide would not have happened without climate change. The heat we are suffering through today is the result of decisions made decades ago.
El Niño / ONI time series, 1950–2026, with 2026 forecast marked "very strong"
Now look at the forecast bar on the right. That's a multi-model ensemble forecast — not an observation yet — pointing to this year's event reaching that same very strong threshold, potentially approaching or exceeding those two benchmark years. What gives us confidence in that forecast is that the spread across individual forecasting systems is narrow — the models agree with each other, which matters going into a live event like this one.
El Niño doesn't add new heat to the planet. It releases heat the ocean has already been storing beneath the surface — which is why a strong event so often becomes one of the hottest years measured. No two events behave identically, so we won't claim this one will mirror 1997 or 2015. But the ocean it's drawing from is the warmest we've ever measured it. There is simply more heat available to release.
ENSO remains one of meteorology's best sources of seasonal predictability. This is powerful information – but knowing what's coming only matters if the warning reaches someone able to act on it.
Transition from science to action
Meteorologists don't only issue forecasts - we're in the field working with emergency managers, labour ministries, and health officials to make sure the weather forecast drives actions to protect people from harm.
The International Labour Organization tells us that 2.4 billion people or 70% of the global workforce — face workplace heat risk at some point every year, concentrated among outdoor and agricultural workers.
Yet by our last full assessment of climate services, in 2023, only around half of countries provide heat warning services tailored to the needs of the health and labour sectors. Even fewer have fully integrated climate information into health decision-making processes.
That is a gap this Forum can help close: between a meteorological service issuing an authoritative warning, and a health and labour system ready to act on it. Every person on Earth should be covered by an early warning system, and that system must be impact-based and actionable — not just a temperature reading.
One planet, diverse ways to measure and warn for dangerous heat
How hot we feel isn't just air temperature — it's humidity, radiant heat from the streets and buildings around us, how hard we're working, what we're wearing, what conditions or medications we're managing. That's why heat is not only personal, it's place-based: 35 degrees is rare in London, but normal in Bangkok. So the threshold has to be local, and it has to account for how excessive that heat is against what's normal there, for that time of year.
That is why there is no universal definition of heatwave and that there are also many ways to manage heat. And for much of the world, heat isn't episodic — it's chronic.
Consider the many people who work outside in agriculture, construction, and other sectors. We use the Wet Bulb Globe Temperature, which includes humidity, thermal radiation, and wind to characterize heat stress on outdoor workers. The population exposed to outdoor levels of wet-bulb globe temperatures (WBGT) that carry extreme heat stress risk is projected to rise from 275 million at 1 °C of global warming to 789 million at 2 °C. That's why one warning size never fits all.
Cities keep and release heat after dark
Heat isn't a single moment; it's sustained. Overnight cooling doesn’t fully clear what built up during the day — that's the urban heat island effect at work. A series of hot days and nights compounds the risk, and the resulting cumulative excess heat, climbing over days, is often what drives real harm.
In some cities, like Bangkok, that pattern isn't just citywide, it's hyperlocal, varying block by block. Concrete and asphalt hold the sun's heat long after sunset, so some neighbourhoods are still radiating that heat back into the night air while others nearby have already cooled.
This map, from a World Bank study done with the Bangkok Metropolitan Administration last year, shows exactly that — at the district level. And it found what these studies often find: the districts with the greatest urban heat island intensity tend to have limited tree cover and high concentrations of vulnerable populations. For many people living in this city, the urban heat island effect means their homes are dangerously hot overnight, every night.
When hazards arrive together
Heat rarely strikes alone. Heat and drought reinforce each other directly: dry soil heats the air above it faster, and that hotter air pulls still more moisture out of the soil — the same conditions threatening a crop, threaten the people harvesting it.
Last year we saw this pattern again and again making the damages worse. Communities impacted by both heat and drought, wildfire, flooding — each hazard making recovery from the others harder. Our scientists call this compound and cascading hazards. In plain terms: a community rarely finishes recovering from one disaster before the next one arrives.
The invisible infrastructure
Take a breath.
Everything I have shown you so far: the heat trends, the El Niño outlook, the health risks and the early warnings, depends on a system most people never see.
It begins with observations: satellites, ocean buoys, weather balloons, aircraft, ships and ground stations operated by WMO Members around the world. Every day, millions of observations are shared through global systems that WMO helps coordinate.
This idea goes back to 1873, when the world’s first national weather services recognized a simple truth: weather does not respect borders, so the data that describes it must cross borders too.
Today, that data is exchanged globally, combined with models and scientific expertise, and translated by National Meteorological and Hydrological Services into the forecasts, warnings and climate services people rely on.
So when a heat warning reaches a city, a hospital, a farmer, a school or a worker, it is not the product of one institution alone. It is the result of a shared global architecture: observations, data exchange, forecasting and prediction, early warnings and climate services.
But this infrastructure is not guaranteed. It must be maintained, modernized and strengthened.
Between 1970 and 2021, weather, climate and water-related extremes caused more than US$4.3 trillion in reported economic losses worldwide. Yet the systems designed to help prevent and reduce these losses remain underfunded in many parts of the world.
We know that closing observation gaps improves forecasts not only locally, but globally. Better observations in one part of the world can improve forecasts far beyond national borders.
This is why WMO launched the WMO Commons earlier this year: a pooled financing mechanism to sustain and modernize the global weather, climate and water intelligence system.
The Commons supports the full chain I have just described: data and fact exchange, standard settings, knowledge sharing and capacity development.
No country can sustain this system alone. Yet every country depends on it. When one part weakens, all countries are affected.
The WMO Commons is our way of inviting governments, business, philanthropy and partners to invest in the shared global backbone behind the information we all rely on. Not only to understand heat, but to act on it in time.
Resilience decisions need to be backed with sound climate information. Partnerships bring trust
This invisible system is vital because all resilience decisions need to be backed by authoritative and reliable information you can trust.
This trust and support comes only through partnerships. We co-founded the IPCC with UNEP in 1988, and remain the scientific backbone behind its assessments. In 2009, WMO established the Global Framework for Climate Services, which laid the groundwork for exactly the conversation we're having this week: how to move from raw climate data to services tailored for specific sectors — agriculture, water, disaster risk, and health among them. It led to our Joint Programme with WHO and since 2016, together with WHO and NOAA, we founded the Global Heat Health Information Network. Its Technical Support Unit has been hosted at WMO headquarters ever since. That Network - launched at the first Global Heat Forum, in Hong Kong, in 2018 and convenes us here today to strengthen the partnership and shape a Roadmap for Investment and Action this week.
WMO is here with you. Meteorologists need to be core partners in all resilience work, to help you make better investments, understand the risks, and translate the complexity of weather science into meaningful and actionable information. We have built the groundwork already to support heat resilience.
WMO leads the observations and forecasting pillar of UN launched Early Warnings for All to help scale heat warning systems, urban heat mapping, the data and analytics everyone is asking for. The WCRP, the Drought Management Programme all offer opportunities to strengthen this community.
WMO is here, because you need our community and our “invisible infrastructure” to be informed.
Our heat work has a global footprint, and it’s growing
What comes next isn't just a plan, it's already running — and it brings together the latest science, implementation at met services, health ministries, and other partners, and critically, the heat governance that builds the institutional connections to make everything work together. And as you can see, the footprint of our heat and our health work is global, and growing.
Earlier this year, the African Centre of Meteorological Applications for Development launched the first Climate and Health Desk for Africa, in Niger — meteorologists and health experts, co-located, each bringing their own science, working from shared data toward co-produced climate services for health, including warning systems for extreme heat and vector-borne disease. More Desks are coming online to be operational worldwide by next year.
But climate services only work inside a system designed to act on them. That's why, alongside the Desks, WMO, UNDRR, GHHIN, and Duke University co-created a toolkit for extreme heat governance — a practical guide that lets ministries, mayors, and met services turn a warning into cooling centres, adjusted work hours, and hospital readiness, and turn long-range heat projections into coordinated investment. It's being piloted in Belize, Senegal, and Nepal.
That guidance exists because GHHIN's core role is gathering the best evidence, the top experts and sharing what's actually been tried and worked. If you want to see that in practice, the "What Works" track running during this Forum all week is where to look.
Data shows heat warnings and heat plans work
I want to close by acknowledging how far we've already come.
In May 2010, a heatwave in Ahmedabad, India, contributed to more than 1,300 excess deaths in a single month. The Ahmedabad Municipal Corporation and partners took action. In 2013, they built South Asia's first Heat Action Plan, linking early warning directly to hospital preparedness, worker protections, and a public alert system anyone in the city could understand. It's now estimated to save roughly eleven hundred lives every year — and the model has since spread to more than a hundred cities and districts across India and inspired cities worldwide.
Ahmedabad proves that heat governance, early warning, and health action plans save lives. The only question left is whether we scale this everywhere it's needed.
Closing: When I started in this field, I expected mathematical certainty and found chaos instead. What I didn't expect was how much of that chaos we could still answer — not with certainty, but with observation, with cooperation, and with the discipline to share what we've learned. That's the architecture I've walked you through this morning: the observations that start in 1873, the cooperation that built a system to share them, the governance that turns a warning into an action. Success stories like Ahmedabad is what happens when all three hold together — a city that shows what is possible when we take action: eleven hundred lives saved every year.
The chaos was never going to disappear. The only real question is how much of it we choose to meet prepared.
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