Scientific studies on cloud climate influence

A crucial aspect of climate science is the role clouds play in the climate system. Clouds influence Earth's energy balance by reflecting sunlight and trapping heat, but their response to warming remains one of the biggest uncertainties in climate projections. Recent research provides strong observational evidence that cloud feedback amplifies global warming. A study conducted by scientists at Imperial College London and the University of East Anglia used Earth observations and climate model simulations to analyse how clouds respond to environmental changes. Their findings indicate that global cloud feedback is primarily influenced by surface temperature and tropospheric stability, leading to an amplifying effect on global warming. The study constrained global cloud feedback to 0.43 ± 0.35 W⋅m⁻²⋅K⁻¹with 90% confidence, suggesting that the likelihood of equilibrium climate sensitivity (ECS) being below 2°C is only 0.5%. This reinforces the idea that clouds contribute positively to climate change rather than mitigating it. This research is vital for improving climate models and informing policy decisions. P. Ceppi,& P. Nowack, Observational evidence that cloud feedback amplifies global warming, Proc. Natl. Acad. Sci. U.S.A. 118 (30) e2026290118, https://lnkd.in/e736-pjS (2021).

A second opportunity to examine the cloud reduction effects from shipping fuel pollution measures has revealed that the 80% cut in sulphur emissions reduces cloud droplet formation by 67%. When militia attacks disrupted the shipping lane in the Red Sea, many cargo ships were re-routed around the Cape of Good Hope. This provided researchers a unique opportunity to quantify aerosol-cloud interactions, reducing the largest source of uncertainty in global climate projections. In January 2020, the International Maritime Organisation (IMO) mandated a major reduction in sulphur content in marine fuels to decrease air pollution. Aerosols from ship emissions, especially sulphate, influence cloud formation and brightness, which in turn affect Earth's energy balance. Referred to as aerosol-cloud interactions, these particles cause clouds to form with smaller, more numerous droplets, making them brighter and longer lasting, thus more reflective of sunlight. This creates a cooling effect, which has historically masked about one-third of the warming caused by greenhouse gases. There has been large uncertainty about the strength of the aerosol effect which leads to large differences in future global warming projections. Different groups report effects between 10 and 80%. The new study used shipping NO2 measurements as their indicator of shipping levels in the Red Sea and South Atlantic, since those emissions were not effected by the IMO2020 rule change. By comparing NO2 levels with cloud droplets count, the relationship could be calculated. They found a 67% reduction in ships' cloud-altering abilities after the IMO regulations went into effect. The findings should help refine global climate models, offering policymakers and scientists more accurate climate predictions and insight into how environmental policy can protect human health. Being at the high end of previous estimates, this work supports high climate sensitivity (ECS), meaning more warming will unfold as pollution levels decline. It also helps explain the recent acceleration of global warming and adds urgency to decarbonisation efforts. A high ECS suggests warming of at least 3ºC well before the end of the century. Paper: https://lnkd.in/e8JTnH4k #aerosols #climatechange #clouds #IMO2020 #ECS

🌡️ what role had the Reduced Planetary Albedo in the Rapid Surge in Global Warming in 2023? 2023 has shattered alarming climate records, with global temperatures nearing 1.5°C above preindustrial levels. Researchers are now spotlighting a critical, underexplored factor: a sharp decline in Earth's planetary albedo—the planet's reflectivity—which could explain a 0.2°C gap in our understanding of the sudden temperature rise. 🧐 Low-altitude clouds are diminishing in the northern mid-latitudes and tropics, particularly over the Atlantic, contributing significantly to reduced albedo. Planetary albedo in 2023 may have hit its lowest point since at least 1940. This decline is linked to reduced cooling effects from clouds and lower surface reflectivity due to diminishing Arctic and Antarctic ice. Anthropogenic changes, such as stricter marine fuel regulations reducing aerosols, play a role, but global warming itself may be driving this feedback loop. If warming and reduced cloud formation reinforce each other, global warming could accelerate faster than projected, pushing us beyond 1.5°C sooner than anticipated. This calls for: Immediate carbon budget recalculations aligned with the #ParisAgreement. Intensified measures to adapt to escalating climate extremes. 🛰️ This groundbreaking research by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research and ECMWF, leveraging satellite data and advanced climate models, underscores the urgent need for action. Read the article here 👇 https://lnkd.in/eunzEK-a

AAAS: "Earth's clouds are shrinking, boosting global warming." Over more than 2 decades, NASA satellites have tracked a growing imbalance in Earth’s solar energy budget, with more energy arriving than leaving the planet. Most of this imbalance is explained by humanity’s greenhouse gases emissions, which trap heat in the atmosphere like a blanket. "The loss of reflective ice, exposing darker ground and water that absorb more heat, isn’t enough to explain the deficit, and the decline in light-reflecting hazes as countries clean up or close polluting industry falls short as well." George Tselioudis, a climate scientist at NASA’s Goddard Institute for Space Studies, states, “Nobody can get a number that’s even close.” Tselioudis, who presented the work last week at a meeting of the American Geophysical Union, declares, “I’m confident it’s a missing piece. It’s the missing piece.” One band of cloud, the 'equatorial cloud band,' stretches around the planet like a belt. "It forms as trade winds [easterlies] of the Northern and Southern hemispheres converge, forcing moist air upward to cool and condense into clouds." Other bands, the 'midlatitude storm tracks,' are established by the northern + southern jet streams. Using NASA's satellite Terra, which has been monitoring the planet for nearly a quarter-century, the team established equatorial cloud coverage is falling by about 1.5% per decade. Concurrently, the midlatitude storm tracks have been pushed poleward in both North + South Hemispheres. [Except of course when the jet streams get wavier + loop toward the equator, allowing frigid arctic air to reach down to Texas, as I discussed yesterday]. "The team also found that 80% of the overall reflectivity changes in these regions resulted from shrinking clouds, rather than darker, less reflective ones, which could be caused by a drop in pollution." If global circulation changes are occurring, 'an urgent question is whether they will continue, says Tiffany Shaw, a climate dynamicist at the University of Chicago.'

Head up in the clouds? NASA too ☁️ Recent NASA studies found that Earth’s clouds are shifting away from subtropical ocean regions, adding to Earth’s energy imbalance… The studies looked at two areas that frequently have cloud cover from stormy weather: one near the equator and one in the mid-latitudes, where countries including the U.S are primarily located: These storm clouds reflect incoming sunlight, which helps keep the planet cooler… However, the areas these clouds cover are shrinking: One of the studies found that the band of clouds around the equator has narrowed and the clouds in the mid-latitudes have shifted poleward, and this has created larger dry zones in the subtropical oceans… When there are less clouds to reflect incoming sunlight, the energy instead gets absorbed by the ocean, which stores it as heat, and instead of reflecting the energy back out to space to keep a balance, the energy gets trapped on Earth… This contributes to planetary warming and adds to Earth’s energy imbalance that has already been measured by NASA’s CERES satellite instruments… https://lnkd.in/gsK455Zi

New research published in Science Magazine suggests a connection between the startling rise in global temperatures observed in 2023 and diminishing low-level cloud cover. Scientists from Germany’s Alfred Wegener Institute found that the decrease in low-altitude clouds, which reflect sunlight and help regulate Earth’s temperature, intensified warming last year and allowed more sunlight to reach the planet’s surface. This climate phenomenon is creating a kind of feedback loop—where rising temperatures reduce cloud cover which in turn accelerates warming, a consequence of #climatechange that models had not previously predicted.    As we collectively work to address global warming, understanding these dynamics between Earth’s systems is crucial for devising effective strategies—and the stakes could not be higher. Insights like these remind us why #science must remain at the forefront of policy and education as we confront the climate crisis.    Astronomy magazine breaks down the research further here: https://lnkd.in/enHmkuqD