Global greenhouse gas emissions have reached an all-time high, with 56.8 billion tonnes of carbon dioxide released in 2024, according to the annual Indicators of Global Climate Change report. The majority of these emissions stem from the burning of fossil fuels, alongside contributions from other industrial activities such as agriculture.
The concentration of CO2 in the atmosphere has now reached 425.6 parts per million in 2025, the highest level ever recorded. Concentrations of methane and nitrous oxide have also hit record highs, reaching 1936.3 parts per billion and 339.4 parts per billion, respectively. Despite a global shift towards green energy, overall greenhouse gas emissions continue to increase, although at a slower rate than during the peak years of the 2000s.
Seventy scientists contributing to the report warn that this accumulation of gases is causing the planet to warm at a rate far exceeding natural processes. Dr. Matt Palmer, Science Fellow at the UK Met Office, stated, "we are emitting more greenhouse gases than ever before, causing rising greenhouse gas levels which are trapping more and more heat in the atmosphere and pushing the world out of balance."
Lead author Professor Piers Foster of the University of Leeds explained that greenhouse gases function like an insulating blanket around the Earth, trapping heat. When this blanket thickens, it disrupts the planet's energy balance, which measures heat accumulation. This balance, which should naturally be near zero without human influence, has been growing since the 1970s and has now doubled in recent decades, leading to a steady and inevitable warming trend. The rate of human-caused warming in 2025 remained at a record high of 0.27°C (0.49°F), the same as in 2024. The decade from 2016 to 2025 was 0.32°C hotter than the preceding decade, marking it as the hottest ten-year period on record. While natural cycles like El Niño cause annual temperature fluctuations, Professor Foster emphasized that "all" of the warming observed over the last decade can be directly attributed to human activity.
Dr. Samantha Burgess, Strategic Lead for Climate at the Copernicus Climate Change Service, added, "Our study demonstrates that nearly all of the warming over the last decade is driven by human activities."
At the current rate, researchers anticipate the world will exceed 1.5°C (2.7°F) above pre-industrial averages in approximately four years. The remaining carbon budget, the amount of CO2 that can be emitted without exceeding 1.5°C warming, is estimated to be 130 gigatonnes as of the start of 2026, which would be exhausted in just three years at current emission rates.
The disruption to Earth's energy balance is already causing widespread effects globally. A warmer climate increases the likelihood and intensity of extreme weather events, including heatwaves. The number of days experiencing marine heatwaves has more than tripled globally between 1991 and 2025, consistent with human-caused climate change. In 2025 alone, the world experienced 65 days of marine heatwaves, significantly impacting marine ecosystems.
Warmer oceans also contribute to accelerated global sea level rise due to water expansion and melting land ice. Dr. Aimée Slangen, Research Leader at the Royal Netherlands Institute for Sea Research, reported that in 2025, global sea level rise reached a new record of 23 cm since 1901, with the rate of approximately 1.8 mm per year now accelerating. This rise is already increasing coastal flooding in low-lying areas worldwide, affecting livelihoods and ecosystems. The Paris Agreement, established in 2015, aims to limit global average temperature increase to well below 2°C above pre-industrial levels, with efforts to limit it to 1.5°C, a goal that appears increasingly critical as the planet warms and the carbon budget dwindles.