The clear signs of human-induced climate change reached unprecedented levels in 2024, with some consequences expected to be irreversible for centuries
The clear signs of human-induced climate change reached unprecedented levels in 2024, with some consequences expected to be irreversible for centuries, if not millennia, the World Meteorological Organisation (WMO) has warned.
The report found that 2024 was probably the first calendar year to be more than 1.5°C above the pre-industrial era, with a global mean near-surface temperature of 1.55°C to about 0.13°C above the 1850 to 1900 average. This is the warmest year in the 175-year observational record.
Key findings are that:
- The atmospheric concentration of carbon dioxide is at the highest levels in the last 800 000 years;
- Globally each of the past 10 years were individually the 10 warmest years on record;
- Each of the past eight years has 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; and
- The rate of sea level rise has doubled since satellite measurements began.
“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.
Long-term global warming is estimated to be between 1.34°C and 1.41°C warmer compared with the 1850 to 1900 baseline, although the WMO noted the uncertainty ranges in global temperature statistics. A team of international experts from the WMO is examining this further to ensure consistent, reliable tracking of long-term global temperature changes aligned with the Intergovernmental Panel on Climate Change.
Even slight increases bring higher risks and costs to society, the WMO said. The record global temperatures are primarily driven by rising greenhouse gas emissions, compounded by the shift from a cooling La Niña to a warming El Niño event.
Other factors, including changes in the solar cycle, a major volcanic eruption and a decrease in cooling aerosols, may have contributed to the high temperature spikes.
Data for 2024 show continued ocean warming and rising sea levels. “The frozen parts of Earth’s surface, known as the cryosphere, are melting at an alarming rate. Glaciers are retreating, and Antarctic sea ice has reached its second-lowest extent ever recorded,” Saulo said.
Tropical cyclones, floods, droughts and other natural disasters in 2024 led to the highest number of new displacements of people in 16 years. These events worsened food crises and caused economic losses.
In response, the WMO and the global community are strengthening early warning systems and climate services to help decision-makers and society become more resilient.
Saulo stressed the need for greater investment in weather, water and climate services to build safer, more resilient communities. “Only half of all countries worldwide have adequate early warning systems. This must change.”
Atmospheric carbon dioxide
The atmospheric concentration of carbon dioxide, methane and nitrous oxide are at the highest levels in the lpst 800 000 years.
Carbon dioxide concentrations in 2023, the last year for which consolidated global annual figures are available, were 420.0 ± 0.1 parts per million, 2.3 ppm more than in 2022 and 151% of the pre-industrial level (1750). The WMO said 420 ppm corresponds to 3 276 Gt – or 3.276 trillion tonnes of carbon dioxide in the atmosphere.
The WMO said real-time data from specific locations show that levels of these three main greenhouse gases continued to increase in 2024. Carbon dioxide remains in the atmosphere for generations, trapping heat.
In addition to 2024 setting a new record, each of the past 10 years, 2015 to 2024, were individually the 10 warmest years on record.
The record temperature in 2024 was boosted by a strong El Niño, which peaked at the start of the year. In every month from June 2023 to December 2024, monthly average global temperatures exceeded all monthly records prior to 2023.
“Record levels of greenhouse gases were the primary driver, with the shift to El Niño playing a lesser role,” the WMO said.
About 90% of the energy trapped by greenhouse gases in the Earth system is stored in the ocean.
In 2024, ocean heat content reached its highest level in the 65-year observational record. Each of the past eight years has set a new record. The rate of ocean warming for 2005 to 2024 is more than twice that in the period 1960 to 2005.
Ocean warming leads to degradation of marine ecosystems, biodiversity loss and reduction of the ocean carbon sink. It fuels tropical storms and contributes to sea-level rise and is irreversible on centennial to millennial time scales.
“Climate projections show that ocean warming will continue for at least the rest of the 21st century, even for low carbon emission scenarios,” the WMO said.
Acidification of the ocean surface is continuing, as shown by the steady decrease of global average ocean surface pH, the WMO said. The most intense regional decreases are in the Indian Ocean, the Southern Ocean, the eastern equatorial Pacific Ocean, the northern tropical Pacific and some regions in the Atlantic Ocean.
“The effects of ocean acidification on habitat area, biodiversity and ecosystems have already been clearly observed, and food production from shellfish aquaculture and fisheries has been hit as have coral reefs.”
Projections show that ocean acidification will continue to increase in the 21st century, at rates dependent on future emissions. “Changes in deep-ocean pH are irreversible on centennial to millennial time scales.”
Global mean sea level
In 2024, global mean sea level reached a record high. The long-term rate of sea-level rise has more than doubled since the start of the satellite record, increasing from 2.1mm a year from 1993 to 2002 to 4.7mm/year from 2015 to 2024.
Most of the world’s megacities are in coastal areas, with millions of people living in low-elevation coastal zones. Even just a few millimeters of rise can influence coastal flooding and erosion, putting populations at increased risk from storms, floods and salt-water intrusion.
Losses of coastal ecosystems and ecosystem services, groundwater salinisation, flooding and damage to coastal infrastructure cascade into risks to livelihoods, settlements, health, well-being, food, displacement, water security and cultural values in the near to long-term.
The WMO said the period 2022 to 2024 represents the most negative three-year glacier mass balance on record. Seven of the 10 most negative mass balance years since 1950 have occurred since 2016.
“Exceptionally negative mass balances” were experienced in Norway, Sweden, Svalbard and the tropical Andes. Glacier retreat increases short-term hazards, harms economies and ecosystems and long-term water security.
The 18 lowest Arctic sea-ice minimum extents in the satellite record occurred in the past 18 years. The annual minimum and maximum of Antarctic sea-ice extent were each the second lowest in the observed record from 1979.
The minimum daily extent of sea-ice in the Arctic in 2024 was 4.28 million km2, the seventh lowest extent in the 46-year satellite record. This was 1.17 million km² below the 1991–2020 average, nearly the size of South Africa.
In Antarctica, the minimum daily extent tied for the second lowest minimum in the satellite era and marked the third consecutive year that minimum Antarctic sea-ice extent dropped below two million km2. These are the three lowest Antarctic ice minima in the satellite record.
Extreme weather events last year led to the highest number of new annual displacements since 2008 — 824 500 people — and destroyed homes, critical infrastructure, forests, farmland and biodiversity. There were at least 151 unprecedented extreme weather events last year.
The compounded effect of various shocks, such as intensifying conflict, drought and high domestic food prices drove worsening food crises in 18 countries by mid-2024.
Tropical cyclones were responsible for many of the highest-impact events of 2024. These included typhoon Yagi in Vietnam, the Philippines and southern China.
In the United States, hurricanes Helene and Milton in October made landfall on the west coast of Florida as major hurricanes, with economic losses of tens of billions of dollars. More than 200 deaths were associated with the exceptional rainfall and flooding from Helene, the most in a mainland US hurricane since Katrina in 2005.Tropical cyclone Chido caused casualties and economic losses in the French Indian Ocean island of Mayotte, as well as in Mozambique and Malawi. It displaced about 100 000 people in Mozambique.
