Climate chronicles

Global CO₂ emissions in 2024 increased 0.9% on the previous year, totalling 36.3 Gt CO₂. These ongoing emissions further deplete remaining carbon budgets, with some estimates suggesting the 1.5 °C budget will be surpassed within the next 5 years â€” and may have been already.

Sea ice extent remained anomalously low in 2024. Annual mean Antarctic and Arctic sea ice extent was 10.38 million km² and 10.42 million km², respectively, the 2nd and 7th lowest of the satellite record.

Global full-depth ocean heat content (OHC) gain since 1960 reached a record 452 ± 77 ZJ in 2024. OHC was 15 ± 9 ZJ higher than in 2023, primarily associated with warming in the Atlantic and Indian Oceans.

Global sea level rose 0.59 cm in 2024 relative to 2023, reaching a total increase of 10.5 cm over the 31-year satellite record of sea level. Regionally, over 40% of the ocean reached its highest annual sea level value in 2024.

Wildfire burned area was 367 Mha in 2024, ranked 17th since 2001. An estimated 1,965 Tg C was released from these fires, 41% of which came from the Americas, far exceeding their usual 25% contribution.

2024 was one of the wettest years on record, witnessing record-breaking extreme precipitation events across the globe, several of which were compound events. Extreme rainfalls were unprecedented in arid regions and parts of the Global South, with severe monsoon rains and rapidly intensifying tropical cyclones causing severe casualties and economic losses.

2024 shattered temperature records, surpassing 2023’s historic highs to become the warmest year ever recorded. Extreme heatwaves hit West Africa in February, South America and Eastern Europe in March, Southeast Asia in April, and Mexico in June.

2024 saw multiple high-impact compound events. Record-breaking global temperatures combined with regional weather variability to create compound floods, spatially compounding droughts and heatwaves, and hazard sequences with often devastating impacts.

2024 witnessed record-high global vegetation greenness, far outpacing the previous high set in 2020. A total of 67.7% of vegetated land surfaces experienced greening, notably in Eurasian and tropical grasslands, and global croplands.

Global terrestrial water storage (TWS) anomalies continue to decrease, reaching a record low of –7,404 km³ in 2024, a reduction of 796 km³ from 2023. TWS gains in Africa, Australia, Europe, and central and western Antarctica were offset by substantial losses in northwestern Canada, South America, southern Africa and Greenland.

2024 global mean lake surface water temperature (LSWT) was 0.3 °C greater than the 2001–2023 average, the fourth highest on record. Particularly strong positive — and record-breaking — LSWT anomalies occurred throughout Canada and north-eastern Europe, in some cases exceeding 2 °C.

In 2023, global full-depth ocean heat content (OHC) reached a record increase of 464 ± 55 ZJ since 1960, with strong heat gain observed in the Southern and Atlantic Oceans. OHC was 16 ± 10 ZJ higher than in 2022, continuing the long-term increasing trend that started in 1960.

Antarctic sea ice extent was the lowest on record in 2023, with an annual mean of 9.81 million km², beating the previous minimum of 2022. Arctic sea ice extent was also low, with an annual mean of 10.49 million km², but did not break any records.

Wildfires burned 384 Mha of land in 2023, the highest since 2017 but 5% lower than the 2001–2022 average. These fires emitted an estimated 2,524 Tg C, 30% of which came from Canada’s record fire season.

Global greening continued into 2023, reaching near-record values that were dominated by regional enhancement in the mid-western USA, Europe, northern Australia and parts of equatorial Africa. In contrast, climatic events contributed to browning signals in Russia, Canada, Mexico and tropical drylands.

Multiple relentless heatwaves occurred in 2023, with much of the world experiencing at least 20 more heatwave days than the 1991–2020 average. Prominent and record-breaking events included exceptional wintertime and spring heat in South America, large heatwaves over Europe, Africa and Asia, and a prolonged event over south-eastern USA and Central America.

Global terrestrial water storage (TWS) anomalies reached a record low of −6697 km³ in 2023, decreasing 759 km³ from 2022. These reductions reflect widespread droughts across North and South America, Europe and Asia, and ongoing TWS losses from glacial melt and groundwater use for irrigation.

2023 saw a multitude of extreme precipitation events across the globe, causing flash flooding, countless fatalities and huge economic losses. Fuelled by a combination of a strong El Niño, record ocean warmth and anthropogenic warming, these events highlight the ongoing risks posed by extreme precipitation in a warming climate.

Global CO₂ emissions for 2023 increased by only 0.1% relative to 2022 (following increases of 5.4% and 1.9% in 2021 and 2022, respectively), reaching 35.8 Gt CO₂. These 2023 emissions consumed 10–66.7% of the remaining carbon budget to limit warming to 1.5°C, suggesting permissible emissions could be depleted within 0.5–6 years (67% likelihood).

In 2023, national and international climate policy advanced in many areas but also faced substantial domestic hurdles in others. Countries agreed on new global initiatives and many major emitters expanded national climate policies. However, others rolled back existing policies and continued to support fossil fuels, slowing down global progress.

Greenhouse gas forcing has increased ocean heat content, with large impacts on the Earth system. This Review outlines observed and projected global and regional changes, revealing an observed 0–2,000 m global increase of 351.4 ± 59.8 ZJ from 1958 to 2019, and a projected increase of 1,874 [1,637–2,109] ZJ by 2100 under SSP5-8.5.

With continued anthropogenic warming, an ice-free Arctic (sea ice area <1 million km²) is inevitable. This Review outlines the various characteristics of an ice-free Arctic, highlighting that future emission trajectories will determine where, how frequently and how long the Arctic will be ice free each year.

Vegetation fires are integral to some ecosystems but can be economically and environmentally destructive. This Review discusses contemporary and future fire regimes, adaptation to fire in the Anthropocene and the need for increased transdisciplinary research to achieve better fire management.

Vegetation on Earth is increasing, potentially leading to a larger terrestrial carbon sink. In this Review, we discuss the occurrence of this global greening phenomenon, its drivers and how it might impact carbon cycling and land-atmosphere heat and water fluxes.

Heatwaves are occurring with increasing frequency and intensity, necessitating prediction so as to minimize loss of life and other impacts. This Review outlines heatwave predictive capabilities at daily to decadal timescales, and discusses heatwave projections with anthropogenic warming.

Water resources are threatened by human activities and climate variability. This Review discusses trends in water storage and availability and examines ways to enhance water-resource resilience through green and grey solutions.

Short-duration rainfall extremes are determined by complex processes that are affected by the warming climate. This Review assesses the evidence for the intensification of short-duration rainfall extremes, the associated drivers and the implications for flood risks.

Climate change affects lakes worldwide and is predicted to continue to alter lake ice cover, surface temperature, evaporation rates, water levels and mixing regimes. This Review discusses recent and expected lake responses to climate change and looks towards future research opportunities in lake monitoring and modelling.

Research on compound events has increased vastly in the last several years, yet, a typology was absent. This Review proposes a comprehensive classification scheme, incorporating compound events that are preconditioned, multivariate, temporally compounding and spatially compounding events.