Veille 2.1

Global temperature in 2025 declined 0.1°C from its El Nino-spurred maximum in 2024, making 2025 the second warmest year. The 2023-2025 mean is +1.5°C relative to 1880-1920. The 12-month running-mean temperature should decline for the next few months, reaching a minimum about +1.4°C. Later in 2026, we expect the 12-month running-mean temperature to begin to rise, as dynamical models show development of an El Nino. We project a global temperature record of +1.7°C in 2027, which will provide further confirmation of the recent global warming acceleration.

German scientists warn global warming is accelerating faster than expected, raising the risk of a 3 °C rise by 2050 and forcing Europe to confront unthinkable adaptation plans.

The Production Gap Report finds that 10 years after the Paris Agreement, governments plan to produce more than double the volume of fossil fuels in 2030 than would be consistent with limiting global warming to 1.5°C, steering the world further from the Paris goals than the last such assessment in 2023.

Several, more recent global warming projections in the coupled model intercomparison project 6 contain extensions beyond year 2100–2300/2500. The Atlantic meridional overturning circulation (AMOC) in these projections shows transitions to extremely weak overturning below the surface mixed layer (<6 Sv; 1 Sv = 106 m3 s−1) in all models forced by a high-emission (SSP585) scenario and sometimes also forced by an intermediate- (SSP245) and low-emission (SSP126) scenario. These extremely weak overturning states are characterised by a shallow maximum overturning at depths less than 200 m and a shutdown of the circulation associated with North Atlantic deep water formation. Northward Atlantic heat transport at 26°N decreases to 20%–40% of the current observed value. Heat release to the atmosphere north of 45°N weakens to less than 20% of its present-day value and in some models completely vanishes, leading to strong cooling in the subpolar North Atlantic and Northwest Europe. In all cases, these transitions to a

The startup Gigablue announced with fanfare this year that it reached a historic milestone: selling 200,000 carbon credits to fund what it describes as a groundbreaking technology in the fight against climate change . But outside scientists frustrated by the lack of information released by the company say serious questions remain about whether Gigablue’s technology works as the company describes. Their questions showcase tensions in an industry built on little regulation and big promises — and a tantalizing chance to profit.

In a rapidly changing climate, evidence-based decision-making benefits from up-to-date and timely information. Here we compile monitoring datasets (published at https://doi.org/10.5281/zenodo.15639576; Smith et al., 2025a) to produce updated estimates for key indicators of the state of the climate system: net emissions of greenhouse gases and short-lived climate forcers, greenhouse gas concentrations, radiative forcing, the Earth's energy imbalance, surface temperature changes, warming attributed to human activities, the remaining carbon budget, and estimates of global temperature extremes. This year, we additionally include indicators for sea-level rise and land precipitation change. We follow methods as closely as possible to those used in the IPCC Sixth Assessment Report (AR6) Working Group One report.

The human fingerprint on global warming was likely evident in Earth’s atmosphere far earlier than previously thought—even before the invention of modern cars, a new study says. Using a combination of scientific theory, modern observations and multiple, sophisticated computer models, researchers found a clear signal of human-caused climate change was likely discernible with high confidence as early as 1885, just before the advent of gas-powered cars but after the dawn of the industrial revolution.

Recent simulations using the Community Earth System Model (CESM) indicate that a tipping event of the Atlantic Meridional Overturning Circulation (AMOC) would cause Europe to cool by several degrees. This AMOC tipping event was found under constant pre-industrial greenhouse gas forcing, while global warming likely limits this AMOC-induced cooling response. Here, we quantify the European temperature responses under different AMOC regimes and climate change scenarios. A strongly reduced AMOC state and intermediate global warming (C, Representative Concentration Pathway 4.5) has a profound cooling effect on Northwestern Europe with more intense cold extremes. The largest temperature responses are found during the winter months and these responses are strongly influenced by the North Atlantic sea-ice extent. Enhanced North Atlantic storm track activity under an AMOC collapse results in substantially larger day-to-day temperature fluctuations. We conclude that the (far) future European temperatures are dependent o

Earth’s albedo (reflectivity) declined over the 25 years of precise satellite data, with the decline so large that this change must be mainly reduced reflection of sunlight by clouds. Part of the cloud change is caused by reduction of human-made atmospheric aerosols, which act as condensation nuclei for cloud formation, but most of the cloud change is cloud feedback that occurs with global warming. The observed albedo change proves that clouds provide a large, amplifying, climate feedback. This large cloud feedback confirms high climate sensitivity, consistent with paleoclimate data and with the rate of global warming in the past century.

Springtails illustrate in new research how global warning and antibiotic resistance creates synergistic effects: warming increases pesticide toxicity, triggering antibiotic resistance which spreads through horizontal gene transfer and predation.

2023 set a number of alarming new records. The global mean temperature also rose to nearly 1.5 degrees Celsius above the preindustrial level, another record.A team led by the Alfred Wegener Institute puts forward a possible explanation for the rise in global mean temperature: our planet has become less reflective because certain types of clouds have declined. The work is published in the journal Science.

We investigate the probabilities of triggering climate tipping points under five Shared Socioeconomic Pathways (SSPs) and how they are altered by including the additional carbon emissions that could arise from tipping points within the Earth's carbon cycle. The crossing of a climate tipping point at a threshold level of global mean surface temperature (threshold temperature) would commit the affected subsystem of the Earth to abrupt and largely irreversible changes with negative impacts on human well-being. However, it remains unclear which tipping points would be triggered under the different SSPs due to uncertainties in the climate sensitivity to anthropogenic greenhouse gas emissions, the threshold temperatures and timescales of climate tipping points, and the response of tipping points within the Earth's carbon cycle to global warming. We include those uncertainties in our analysis to derive probabilities of triggering for 16 previously identified climate tipping points within the Earth system.

Tipping elements within the Earth system are increasingly well understood. Scientists have identified more than 25 parts of the Earth’s climate system that are likely to have “tipping points” – thresholds where a small additional change in global warming will cause them to irreversibly shift into a new state. The “tipping” of these systems – which include the Atlantic Meridional Overturning Circulation (AMOC), the Amazon rainforest and the Greenland ice sheet – would have profound consequences for both the biosphere and people. More recent research suggests that triggering one tipping element could cause subsequent changes in other tipping elements, potentially leading to a “tipping cascade”. For example, a collapsed AMOC could lead to dieback of the Amazon rainforest and hasten the melt of the Greenland ice sheet.

Morgan Stanley, JPMorgan and an international banking group have quietly concluded that climate change will likely exceed the Paris Agreement’s 2 degree goal.Top Wall Street institutions are preparing for a severe future of global warming that blows past the temperature limits agreed to by more than 190 nations a decade ago, industry documents show.

Dozens of companies and academic groups are pitching the same theory: that sinking rocks, nutrients, crop waste or seaweed in the ocean could lock away climate-warming carbon dioxide for centuries or more. Nearly 50 field trials have taken place in the past four years, with startups raising hundreds of millions in early funds. But the field remains rife with debate over the consequences for the oceans if the strategies are deployed at large scale, and over the exact benefits for the climate. Critics say the efforts are moving too quickly and with too few guardrails.

Global temperature leaped more than 0.4°C (0.7°F) during the past two years, the 12-month average peaking in August 2024 at +1.6°C relative to the temperature at the beginning of last century (the 1880-1920 average). This temperature jump was spurred by one of the periodic tropical El Niño warming events, but many Earth scientists were baffled by the magnitude of the global warming, which was twice as large as expected for the weak 2023-2024 El Niño.

... An “acid” test of our interpretation will be provided by the 2025 global temperature: unlike the 1997-98 and 2015-16 El Ninos, which were followed by global cooling of more than 0.3°C and 0.2°C, respectively, we expect global temperature in 2025 to remain near or above the 1.5°C level. Indeed, the 2025 might even set a new record despite the present weak La Nina. There are two independent reasons. First, the “new” climate forcing due to reduction of sulfate aerosols over the ocean remains in place, and, second, high climate sensitivity (~4.5°C for doubled CO2) implies that the warming from recently added forcings is still growing significantly.

Human-driven ocean warming is increasingly overwhelming El Niño, La Niña, and other natural climate patterns.

Climate change will set the parameters of our post-Princeton lives. The fires that devastated the Palisades earlier this month were, as our nation’s exasperated and exhausted climate scientists continue to remind us, only harbingers of the floods, tornados, and heatwaves to come. Global warming is surpassing the climate models that scientists built in the 2010s and early 2020s that already forecasted a borderline-apocalyptic future. Undoubtedly, by the time current Princeton students reach middle age, they will have witnessed a slew of societal structures sag — or collapse entirely — under the weight of extreme weather events and ever-worsening ecological decline.

An international group of scientists, led by King's College London, has revealed how continued global warming will lead to more parts of the planet becoming too hot for the human body over the coming decades. the amount of landmass on our planet that would be too hot for even healthy young humans (18 to 60-year-olds) to keep a safe core body temperature will approximately triple (to 6%)—an area almost the size of the US—if global warming reaches 2°C above the preindustrial average.

An engaging discussion on groundbreaking research that reveals the unexpected drivers behind the recent unprecedented rise in global temperatures. Moderated by SDSN President Professor Jeffrey Sachs, this virtual event explored Dr. James Hansen and colleagues' findings in the latest publication, “Global Warming Has Accelerated,” their implications for climate sensitivity, and the urgent need for alternative approaches to mitigate the looming "point of no return."

Some scientists fear the risk of a collapse to warm Atlantic currents has not been taken seriously.

Human-caused climate change increased the likelihood and intensity of the hot, dry and windy conditions that fanned the flames of the recent devastating Southern California wildfires, a scientific study found. But the myriad of causes that go into the still smoldering fires are complex, so the level of global warming's fingerprints on weeks of burning appears relatively small compared to previous studies of killer heat waves, floods and droughts by the international team at World Weather Attribution. Tuesday's report, too rapid for peer-review yet, found global warming boosted the likelihood of high fire weather conditions in this month's fires by 35% and its intensity by 6%.

Heatwaves can lead to considerable impacts on societal and natural systems. Accurate simulation of their response to warming is important for adaptation to potential climate futures. Here, we quantify changes of extreme temperatures worldwide over recent decades. We find an emergence of hotspots where the hottest temperatures are warming significantly faster than more moderate temperatures. In these regions, trends are largely underestimated in climate model simulations. Globally aggregated, we find that models struggle with both ends of the trend distribution, with positive trends being underestimated most, while moderate trends are well reproduced. Our findings highlight the need to better understand and model extreme heat and to rapidly mitigate greenhouse gas emissions to avoid further harm.

Surpassing 1.5°C of warming can be undone at a later date – using tech, land and resources that don’t exist.

Carbon Brief provides an updated analysis of when the world will likely exceed the Paris 1.5C limit

Global temperature (12-month mean) is still rising at 1.56°C relative to 1880-1920 in the GISS analysis through April (Fig. 1). [Robert Rohde reports that it is 1.65°C relative to 1850-1900 in the BerkeleyEarth analysis.[3]] Global temperature is likely to continue to rise a bit for at least a month, peak this summer, and then decline as the El Nino fades toward La Nina. Acceleration of global warming is now hard to deny. The GISS 12-month temperature is now 0.36°C above the 0.18°C/decade trend line, which is 3.6 times the standard deviation (0.1°C). Confidence in global warming acceleration thus exceeds 99%, but we need to see how far temperature falls with the next La Nina before evaluating the post-2010 global warming rate.

Over the past year, there has been a vigorous debate among scientists – and more broadly – about whether global warming is “accelerating”.

Anthropogenic emissions drive global-scale warming yet the temperature increase relative to pre-industrial levels is uncertain. Using 300 years of ocean mixed-layer temperature records preserved in sclerosponge carbonate skeletons, we demonstrate that industrial-era warming began in the mid-1860s, more than 80 years earlier than instrumental sea surface temperature records. The Sr/Ca palaeothermometer was calibrated against ‘modern’ (post-1963) highly correlated (R2 = 0.91) instrumental records of global sea surface temperatures, with the pre-industrial defined by nearly constant (<±0.1 °C) temperatures from 1700 to the early 1860s. Increasing ocean and land-air temperatures overlap until the late twentieth century, when the land began warming at nearly twice the rate of the surface oceans. Hotter land temperatures, together with the earlier onset of industrial-era warming, indicate that global warming was already 1.7 ± 0.1 °C above pre-industrial levels by 2020. Our result is 0.5 °C higher than IPCC estim

Global warming is accelerating because the drive for warming, Earth’s energy imbalance, has doubled in the past decade. Measurement of the acceleration is hampered by unforced tropical (El Nino/La Nina) variability, but a good measuring stick is provided by warming between successive large El Ninos. Strengthening of the current (2023-24) El Nino has raised it to a level similar to the 1997-98 and 2015-16 El Ninos. The first six months of the current El Nino are 0.39°C warmer than the same six months of the 2015-16 El Nino, a global warming rate of 0.49°C/decade, consistent with expectation of a large acceleration of global warming. We expect the 12-month mean temperature by May 2024 to eliminate any doubt about global warming acceleration. Subsequent decline of the 12-month temperature below 1.5°C will likely be limited, confirming that the 1.5°C limit has already been passed.