The Year 2024 Was Warmest-Ever on Record – Temperature Rise Likely Exceeded 1.5°C
Climate change 19/03/2025 •
Record warming has led to cascading impacts, such as a higher rate of glacier melting and ocean warming, which threaten fisheries and freshwater supplies.

The past ten years (2015-2024) were the ten warmest years on record, individually and collectively, according to the State of the Global Climate 2024 report released on 19 March.

The year 2024 was also the warmest year in the 175-year observational record of temperature tracking, according to the United Nations’ agency World Meteorological Organization (WMO), in the annual report.

And it was the first calendar year during which average temperatures were “likely” more than 1.5°C above the pre-industrial era (1850-1900) baseline, WMO experts said at a press conference on the report’s findings on Tuesday.

They use the term “likely” due only to a highly technical scientific debate over what exactly may be considered the pre-industrial temperature baseline.

2024 was the warmest year on record and an estimated 1.55°C above the pre-industrial average, with a margin of error of ±0.13 C.

Key climate indicators worsening

Key climate indicators have worsened and some of the consequences are irreversible over hundreds if not thousands of years, said, Chris Hewitt, WMO’s Director of Climate Services at Tuesday’s press briefing.

“The climate has always been changing, if we look back at the distant past, then these rates of change are pretty high and not very welcome,” he said.

Among those, atmospheric concentrations of the greenhouse gas, carbon dioxide (CO2), are now at the highest levels it has been in the last 800,000 years.

The largest three-year loss of glacier mass on record also has occurred over the past three years. This has pushed up the rate of sea level rise which has doubled since satellite measurements began.

In 2024, extreme weather events like tropical cyclones, floods, droughts, and other hazards also led to the highest-ever number of people displaced in the past 16 years. Those events  also contributed to worsening food crises and caused massive economic losses.

“While a single year above 1.5°C of warming does not indicate that the long-term temperature goals of the Paris Agreement are out of reach, it is a wake-up call that we are increasing the risks to our lives, economies and to the planet,” said WMO Secretary-General Celeste Saulo in a press statement.

Rising planetary distress

Record temperatures extended over a wide area.

Rising heat is also affecting the integrity of the world’s oceans, critical habitats for fish, upon which one-third of the world’s population depends as a key source of protein, with each of the past eight years having set a new record for ocean heat content.

“Our planet is issuing more distress signals — but this report shows that limiting long-term global temperature rise to 1.5°Celsius is still possible. Leaders must step up to make it happen — seizing the benefits of cheap, clean renewables for their people and economies  —  with new National climate plans due this year,” United Nations Secretary-General António Guterres said in a press statement.

Right now, precisely the contrary is happening in the world’s largest economy and second largest GHG emitter, the United States.  The US government has fired key scientists affiliated with the National Oceanic and Atmospheric Administration (NOAA), which monitors oceans and temperatures; removed key climate data and pollution references from websites; abolished climate-related Environmental Protection Agency pollution regulations, rescinded incentives for clean energy production.

See related story: US EPA Rollback of Dozens of Air, Water and Chemical Pollution Regulations Threatens America’s Health, Experts Warn

In the case of the 2024 report, data was not affected, WMO experts at the conference said. But they did not elaborate on the extent to which scientific collaborations with US government scientists were still continuing.

“So, in the world of meteorology, whether in climates and oceanography, we exchange and share data and science and knowledge. So that would apply to any country and the US is clearly one of the world leaders in the field of climate. So, we certainly value the engagement in collaboration with us scientists and US organizations,” Hewitt said.

Scientists also stressed that the WMO report relies on multiple datasets, including, but not limited to data provided by NOAA.

Long-term warming hasn’t yet exceeded 1.5°C

While the average temperature in 2024 may have been above 1.5°C, the average over the past several decades was estimated at 1.34-1.41°C above the 1850-1900 baseline, the scientists said. Effectively, this means that the 1.5°C limit set out in the 2015 UN Paris Agreement, hasn’t yet been formally breached.

The record global temperatures seen in 2023 and broken in 2024 were also due to the ongoing rise in greenhouse gas emissions, coupled with a shift from a cooling La Niña to warming El Niño event, the report said.

Several other factors may have contributed to the unexpectedly unusual temperature jumps, including changes in the solar cycle, a massive volcanic eruption and a decrease in cooling aerosols, according to the report.

A WMO team of international experts is working to ensure even more reliable tracking of long-term global temperature changes, in collaboration with the Intergovernmental Panel on Climate Change (IPCC) – the UN body set up to assess science related to climate change.

Why Oceans are warming faster

Annual global ocean heat content down to 2000 m depth for the period 1960–2024.

Around 90% of the energy trapped by greenhouse gases in the earth’s system is absorbed by the oceans. The rate of ocean warming over the past two decades, 2005-2024, is more than twice that in the period 1960-2005.

“The ocean is warming, and it’s a continued warming, and in 2024 we observed ocean heat content which reached the highest levels in a 65-year observational record,” Karina von Schuckmann, an oceanographer at Mercator Ocean in France said during a press conference held to release the report.

“Data for 2024 show that oceans continued to warm, and sea levels continued to rise. The frozen parts of Earth’s surface, known as the cryosphere, are melting at an alarming rate: glaciers continue to retreat, and Antarctic sea ice reached its second-lowest extent ever recorded. Meanwhile, extreme weather continues to have devastating consequences around the world,” said Saulo of WMO.

The 18 lowest Arctic sea-ice extents on record were all in the past 18 years.

Cascading impacts of extreme weather events

In 2024 extreme weather events worsened around the world.

Meanwhile, extreme weather driven by rising temperatures, such as cyclones, forest fires and floods, displaced over 100,000 people, the highest number since 2008, and destroyed homes, critical infrastructure, forests, farmland and biodiversity.

The compounded effect of various shocks, such as intensifying conflict, drought and high domestic food prices drove worsening food crises in 18 countries globally by mid-2024, the WMO report said.

Tropical cyclones were responsible for many of the highest-impact events of 2024. Tropical Cyclone Chido on 14 December 2024 caused casualties and economic losses in the French Indian Ocean island of Mayotte, Mozambique and Malawi.

But high displacement numbers are not all bad, experts stressed.

“Early warning systems, when they’re effective, say, for a tropical storm, can often mean that people have moved out of an area and may be counted amongst displaced people,” explained John Kennedy, co-chair of WMO’s expert team on Climate Monitoring and Assessment.

“So rather than seeing casualties, we see people being moved to safer areas.”

Ocean warming will continue until the end of century, even in low-carbon scenarios

Real-time data from specific locations show that levels of the three main greenhouse gases – carbon dioxide, as well as methane and nitrous oxide – already at the highest levels in the last 800,000 years – continued to increase in 2024.

Gases like carbon dioxide remain in the atmosphere for generations, trapping heat.

Ocean warming leads to the degradation of marine ecosystems, biodiversity loss, and reduction of the ocean’s ability to act as a carbon sink. It fuels tropical storms and contributes to sea-level rise. Ocean warming is even more irreversible – on centennial to millennial time scales.

Climate projections thus show that ocean warming will continue for at least the rest of the 21st century, even for low-carbon emission scenarios.

Along with the urgent need to reduce greenhouse gas emissions, experts stressed on the need to strengthen early warning systems for countries.

Investments in weather, water and climate services are more important than ever to meet the challenges and build safer, more resilient communities, Saulo stressed.

“Only half of all countries worldwide have adequate early warning systems. This must change,” said Saulo.

Image Credits: WMO, WMO , WMO.

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