Computational “time machine” shows solar and wind on track for 2°C target but not for 1.5°C

Chalmers University of Technology

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

Avi Jakmola, PhD Student, Department of Environmental and Energy Sciences, Chalmers University of Technology, Sweden

view more 

Credit: Chalmers University of Technology | Christian Löwhagen

Wind and solar power have grown faster than almost anyone predicted but projecting their future expansion remains surprisingly difficult. Researchers at Chalmers University of Technology, Sweden, have developed what they call a computational “time machine” – a model that outperforms existing projection methods by using AI techniques to analyse historical growth patterns across countries. Their central projection shows that onshore wind is likely to supply around 25 per cent of global electricity by 2050, with solar reaching about 20 per cent. This is consistent with the 2°C target, but falls short of what is required for 1.5°C.

Predicting the future is particularly challenging for technologies like wind and solar, where rapid cost declines are offset by growing barriers such as public opposition, infrastructure constraints and policy shifts.

“Existing models are very good at identifying what needs to happen to reach climate targets, but they can’t tell us which developments are most likely. That’s the gap we wanted to fill”, says Jessica Jewell, Professor at Chalmers University of Technology.

Across more than 200 countries, the researchers identified a recurring pattern in how wind and solar power grow: long periods of relatively steady expansion punctuated by sudden growth spurts often triggered by policy shifts.

“Most models assume a smooth S-shaped growth curve, but that’s not how it actually looks in the real world. Growth often comes in bursts, and if you ignore that, you can misjudge how fast technologies will expand,” says Avi Jakhmola, PhD Student at Chalmers University of Technology and first author of the paper published in Nature Energy.

13,000 virtual worlds for the future

So, with the goal of improving the predictions, Jakhmola created a model built on 13,000 virtual worlds. In each of these worlds, solar and wind power develop in different ways – from the fastest possible expansion to the slowest – and everything in between. A machine learning algorithm was then trained on all these worlds to learn to predict global outcomes from early national trends.

“When we apply the model to real-world data, it can tell us what is the most probable outcome for the future – given what we have seen so far and given all the virtual worlds it has seen”, says Jakhmola.

By 2050, the model projects onshore wind reaching around 26 per cent of global electricity (central range: 20-34 per cent), and solar around 21 per cent (15-29 per cent). This broadly aligns with 2°C-compatible pathways but falls short of what’s needed for 1.5°C.

The projections also put the COP28 pledge to triple renewables capacity by 2030 in perspective. The pledge falls near the 95th percentile meaning that it would require growth rates rarely observed.

“The tripling of renewables pledge is not impossible, but it would require everything to go extremely well in all countries”, says Jewell.

The researchers also tested what would actually be required if we are to reach the 1.5°C goal.

“If we start now, the required growth rates are demanding but not unprecedented, comparable to what the EU targets for wind with REPowerEU and what India has planned for solar power,” says Jakhmola. “But if we delay until 2030, the acceleration needed becomes much steeper and much more abrupt. The window for ramping up closes quickly.”

Going back in time to ensure the model’s reliability

The researchers also used the model to test the reliability of its projections – by going back in time.

“We wanted to know if our projections will hold up ten or twenty years from now. When we fed the model only data from 2015, we found that it correctly predicts what has happened since then. This is what we mean by a ‘computational time machine’ and it gives us real confidence in the projections going forward”, says Jakhmola.

The study points toward a broader ambition to develop scientifically-rigorous methods for projecting the most likely growth paths for other low-carbon technologies, not just wind and solar.

Jessica Jewell says: “It’s long been a joke how bad technology forecasts are. But if you’re a decision maker, trying to figure out how hard to push for change, you need a realistic baseline. Our study is the first step towards developing such a realistic view of the future.”

More about the research:

The paper 'Probabilistic projections of global wind and solar power growth based on historical national experience',  has been published in Nature Energy. The researchers have also made an online visualisation tool of the results, available at the Energy Technology and Policy website. The authors are Avi Jakhmola,  Jessica Jewell, Vadim Vinichenko and Aleh Cherp. The researchers are active at Chalmers University of Technology and Lund University in Sweden, University of Bergen in Norway, International Institute for Applied Systems Analysis and Central European University in Austria.

 

More about the targets and the Paris Climate Agreement:

The Paris Climate Agreement is a legally binding international treaty on climate change. It was adopted by 196 Parties at the UN Climate Change Conference (COP21) in Paris, France, on 12 December 2015 and entered into force on 4 November 2016. Its overarching goal is to hold “the increase in the global average temperature to well below 2°C above pre-industrial levels” and pursue efforts “to limit the temperature increase to 1.5°C above pre-industrial levels.”

---

Journal

Nature Energy

DOI

10.1038/s41560-026-02021-w 

Method of Research

Computational simulation/modeling

Article Title

Probabilistic projections of global wind and solar power growth based on historical national experience

 

U of A research finds improved weather forecasts could reduce heat deaths as climate warms

Experts found that technological advancements could reduce U.S. mortality from heat by 18% to 25% in the year 2100.

University of Arizona

Facebook

X
BlueskyMessageWhatsAppEmail

 

image: 

Depending on the range of technological improvements and climate change, researchers found that improving short-term temperature forecasts in alignment with expert predictions of technological development could reduce U.S. mortality from heat by 18% to 25% in the year 2100.

view more 

Credit: Chris Richards/University of Arizona Communications

When extreme weather looms, timely and accurate warnings can give people the chance to adjust their plans, brace for danger and, in the most severe cases, make decisions that keep them safe. Does that mean improving weather forecasts could save more lives in a warming climate?

Derek Lemoine, Arizona Public Service professor of economics at the University of Arizona Eller College of Management, is part of a team that recently answered that question. The team's research, published in the journal PNAS, suggests that improving short-term temperature forecasts in alignment with expert predictions of technological development could reduce U.S. mortality from heat by 18% to 25% in the year 2100.

"That could offset the extra heat-related deaths caused by climate change," Lemoine said. "To be clear, we would still rather not experience the climate change – but at least we can find ways to potentially cancel out the increased mortality. While extreme cold is very deadly, people primarily use weather forecasts to avoid the heat. Considering climate change will increase the frequency of extreme heat, accurate weather forecasts will become more valuable."

Lemoine worked alongside researchers from Columbia University, the University of Oregon and Princeton University.

To reach their conclusions, Lemoine and his colleagues used day-ahead National Weather Service forecasts across the contiguous United States dating back to the summer of 2004. They combined that information with actual weather data collected by Oregon State University's PRISM Climate Group, which collects tens of thousands of weather station observations from across the country every day. After compiling their historical weather data, the researchers then incorporated county‑level mortality records from the Centers for Disease Control and Prevention, which tracks vital events across the country.

After eliminating deaths caused by factors other than weather, the team found that a key element in the relationship between temperature and mortality is the accuracy of weather forecasting. The greatest risk came when forecasts underestimated hot conditions. Lemoine said the team established that more accurate forecasts could help reduce deaths on dangerously hot days.

The researchers then examined the future of weather forecasting, and how technological improvements could further enhance its life‑saving potential. They did so by surveying professional meteorologists in early 2025 to gauge how forecasting technology might evolve in the future. Respondents offered insights into a variety of factors, including advancements in artificial intelligence, the effects of climate change and shifts in funding and staffing levels.

Those responses informed the development of three future forecasting scenarios: one in which forecast accuracy matches meteorologists' most optimistic expectations, another based on their most pessimistic projections and a third in which weather prediction becomes perfectly accurate. Using their historical data on mortality and climate, the researchers then estimated how each scenario would affect future mortality under several climate conditions: a no‑climate‑change case where temperatures from 2095 to 2100 resemble those from 2015 to 2020, a warming scenario of 1.6 degrees Celsius, another of 2.7 degrees Celsius and an extreme scenario in which the contiguous United States warms by 3.8 degrees Celsius.

Depending on the range of technological improvements and climate change, the researchers discovered several scenarios in which more accurate weather forecasts could largely offset projected increases in heat-related deaths due to climate change. They also concluded that if investment in forecasting declines and forecast quality deteriorates, lower‑quality predictions could in turn contribute to more heat‑related fatalities.

"Economists aren't valuing life itself," Lemoine said. "We're valuing reductions in the risk of dying. The government conducts a cost‑benefit analysis of new policies, and a key part of that involves assigning a standardized value to any lives saved. That value is so large that it often dominates the analysis. In this case, the number of lives saved by improved forecasting – and the likelihood that this benefit will grow as climate change increases risks – translates into a very high economic value. Once you apply that value to the number of lives saved through better forecasting, you end up with a substantial benefit to investing in weather forecasting."

---

Journal

Proceedings of the National Academy of Sciences

Method of Research

Data/statistical analysis

Subject of Research

Not applicable

Article Title

Weather forecasts become more important for reducing mortality as the climate warms

Article Publication Date

13-Apr-2026

 

Tiny particles in Arctic ponds may play role in cloud formation, climate change

Findings offer insight into why Arctic clouds behave differently, filling a major gap in current climate and weather models

Colorado State University

Facebook

X
BlueskyMessageWhatsApEmail

 

image: 

Cloud cover seen from the ground.

view more 

Credit: Colorado State University/Walter Scott, Jr. College of Engineering

Tiny particles bubbling up from the tops of melting sea ice into the Arctic sky may be a key, understudied element of cloud formation in that climate-sensitive region.

Researchers from Colorado State University have published findings in Geophysical Research Letters that highlight how these airborne “ice-nucleating particles” from biological sources, such as bacteria, provide a platform for the creation of clouds. Because cloud cover plays an important role in the balance between incoming solar energy and outgoing heat, as well as precipitation, these particles may be key to developing a better understanding of climate change in the Arctic.

Ice-nucleating particles can come in the form of things like mineral dust, microbes or sea spray. As they make their way into the atmosphere, they act as templates for water vapor to freeze on to support cloud formation. The new paper highlights ponds of melted water that sit on top of sea ice as a key source of these particles.

The ponds are made of melted snow but can also include a mix of seawater that has seeped in as well as released soil sediment or melted ice from the pack of ice below that hosts small organisms. By taking sea-ice core samples and measuring aerosol emissions around these pools, the team was able to show that ice-nucleating particle concentrations were higher there than in seawater. That likely means there are specific biological processes at play in these pools, contributing to their formation.

Researchers in the Department of Atmospheric Science led the work with samples collected during the MOSAiC Expedition – the Multidisciplinary Drifting Observatory for the Study of Arctic Climate. The expedition is a $150 million international effort to develop a better understanding of declines in Arctic sea ice and how they are linked to climate change. Germany’s Alfred Wegener Institute led the expedition, with key support from the Cooperative Institute for Research in Environmental Sciences – a partnership of the University of Colorado Boulder and the National Oceanic and Atmospheric Administration. In total, scientists and funding agencies from 20 nations were involved, including support from the National Science Foundation, Department of Energy, NOAA and NASA.

The 2019-2020 MOSAiC project offered an opportunity to gather data on these particles in a region that is already feeling the effects of climate change in the form of glacial melt, permafrost thaw and sea-ice decline. So far, only a few specific particles are known to be a part of this cloud formation process. And their path into the atmosphere has rarely been studied in the northernmost, extreme high Arctic, partially because it is difficult to gather samples in that challenging environment.

Camille Mavis, a CSU doctoral student, served as lead author on the paper. She said the Arctic environment lent itself to studying these particles because it is a somewhat simpler system with fewer animals and variables than others around the globe.

She said the Arctic is warming four times faster than the rest of the globe. That could mean more ponds may form in the future, or small changes in their composition could significantly alter the entire system.

“Clouds are complex, and there is still a lot of uncertainty associated with how aerosol interactions affect cloud radiative effects overall. Developing an understanding of the role these particles play will help with weather modeling and a host of other benefits in the future,” Mavis said. “Our current models don’t do a good job of mimicking these clouds right now, especially in polar regions.”

CSU Research Scientist Jessie Creamean traveled with the MOSAiC Expedition to collect the samples used in this study and is the senior author on the paper. She said only a handful of research papers have considered meltwater as a source for these key particles prior to this work.   

“The clouds in the Arctic are different than you would find in the Pacific or Atlantic. They behave differently despite having some of the same general materials and processes,” she said. “That is part of the reason we want to understand how they are formed there, because each region is unique in this small but important process. Our work shows the complex interactions and composition of these ponds and how they contribute to that process.”   

University Distinguished Professor Sonia Kreidenweis also served as an author on the research. The project continues her decades-long work in the characterization of the physical, chemical and optical properties of atmospheric particulate matter, and its effects on visibility and climate.   

She said the team will now investigate the makeup of the particles and how conditions and processes contribute to their release.   

“The particles studied can trigger ice formation at relatively warm temperatures and appear to be more closely associated with time spent over ice rather than the open ocean,” she said. “More research is needed to understand how they are released from meltwater, and how big a role they play in the radiation budget as Arctic melt seasons grow longer and larger.”

Camille Mavis (left) and Jessie Creamean review samples from the project.

Camille Mavis (left) and Jessie Creamean

Camille Mavis reviews samples used in the study. 

Credit

Colorado State University/Walter Scott, Jr. College of Engineering

---

Journal

Geophysical Research Letters

DOI

10.22541/essoar.175408160.06725900/v1 

Article Title

Meltwater as a Local Source of Ice Nucleating Particles in the Central Arctic Summer

Article Publication Date

13-Apr-2026

Climate warming may reduce urban vitality

PNAS Nexus

Facebook

X
BlueskyMessageWhatsAppEmail

Mobile phone data on 13 million people in Spain—more than a quarter of the population—show that hot days reduce individual mobility, thereby reducing social mixing and making city centers less vibrant. As the climate warms, heat could reshape society, increasing heat-related illness, shifting some physical and outdoor activities to evening and night hours, and altering daily movement patterns. Andrew Renninger and Carmen Cabrera focused on Spain, where heat waves are predicted to become more extensive and intense in the coming decades. Using aggregated, anonymous data from the Spanish Ministry for Transport and Sustainable Mobility, which collects location information via mobile phone usage for 27% of Spanish residents, the authors explored how heat changes movement. The authors find that mobility falls by as much as 10% on hot days and by 20% during hot afternoons. Extreme heat reduces mobility most for the elderly, with no significant gender differences. Lower-income people are less likely than affluent people to reduce mobility, likely because they are unable or unwilling to skip work or  work remotely. This socioeconomic effect causes a reduction in social mixing between classes during hot weather. According to the authors, initiatives to install more air conditioning may help people endure heat, but they may not sustain urban dynamism, as people increasingly stay isolated inside during hot weather. Greening and shading of urban cores could help keep them livable and attractive as the climate warms.  

---

Journal

PNAS Nexus

Article Title

Extreme heat reduces and reshapes urban mobility

Article Publication Date

14-Apr-2026

 

Global urban methane emissions are growing more than estimated

Satellite measurements suggest that scientific and government reports don't capture how methane emissions are rising, which could hamper mitigation efforts

University of Michigan

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

 

Photos

 

Key takeaways

• Satellite measurements show that urban methane emissions around the globe have risen 6% since 2019, and emissions from C40 cities partaking in climate pledges are rising at a similar rate as non-participating cities.

• The observed growth in methane emissions is not captured by accounting-based emissions estimates, suggesting that some methane sources are missing or underestimated.

• C40 cities will have to account for nearly 2 additional teragrams of methane emissions—about 30% of their emissions reduction target.

 

Urban emissions of methane—a potent greenhouse gas—are rising faster than "bottom-up" accounting estimates anticipated, according to a study led by University of Michigan Engineering and funded by NASA and the National Institute of Standards and Technology.

 

The discrepancy was found with satellite measurements of methane over 92 major cities around the world. For 72 of the cities, there were sufficient data to track changes in methane emissions between 2019 and 2023. Overall, global urban methane emissions in 2023 were 6% higher than 2019 levels and 10% higher than 2020 levels, although they tended to decrease in European cities. 

 

In contrast, accounting methods—which tally emission estimates of individual methane sources—suggest that urban methane emissions have only risen between 1.7% and 3.7% since 2020. 

 

The study included over half of the C40 network, a group of 97 cities around the world aiming to reach net-zero emissions by 2050. Total methane emissions across all the studied C40 cities in 2023 were also 10% higher than 2020 levels, and the cities will have to contend with an extra 2 teragrams of methane emissions per year, which is about 30% of their emission reduction targets. The gap between official estimates and satellite measurements warn that city policies designed with accounting estimates may not reduce methane emissions as desired.

 

"In order to reduce greenhouse gas emissions and set good emissions policy, cities need to know how much they are emitting and what those sources are. But there is quite a bit of uncertainty with that for methane," said Eric Kort, corresponding author of the study published in Proceedings of the National Academy of Sciences. He advised the study's lead author as a U-M professor of climate and space sciences and engineering, and is now director of the Atmospheric Chemistry Department at the Max Planck Institute for Chemistry.

 

Checking emission books

 

The study continues Kort's work identifying gaps in accounting of methane, which can enter the atmosphere from old or leaky natural gas infrastructure, landfills and wastewater treatment plants, and is 80 times more potent at warming the planet than carbon dioxide over a 20-year period. 

 

With measurements from airplane surveys, Kort's research group has shown that flaring at oil and gas production sites leaks 5 times more methane than previously estimated, and that the true climate impact of offshore oil and gas production is double the official estimates. The findings helped make flares an emissions-reduction target in the Inflation Reduction Act, leading to a $30 million Department of Energy call for new technology to reduce leaks from gas flaring.

 

In 2019, similar aerial measurements suggested that several large cities across the U.S. were also emitting more methane than previously thought. The new study showed that this is a global problem.

 

"Cities have the motivation and power to reduce greenhouse gas emissions and therefore, present significant opportunities for impactful emissions reduction," said Erica Whiting, U-M doctoral student in climate and space sciences and engineering and the study's first author. "However, there was not previously a method to quantify and monitor urban methane emissions around the globe and, therefore, no observation-based method to evaluate emission reduction strategies."

 

The researchers' global satellite measurements suggest that urban emissions accounted for 10% of all human methane emissions in 2023, and city methane emissions overall were nearly four times higher than the oil and gas "ultra emitters" that have been the focus of previous studies and emission policies.

Monitoring methane from space
 

The new findings come from the TROPOMI instrument, which was launched aboard the European Copernicus Sentinel-5 Precursor satellite in 2017 to track atmospheric pollution and climate change. TROPOMI measures the amount of sunlight reflected by the atmosphere back into space. It separately measures many wavelengths of light, each of which provides information on the concentration of a particular gas or pollutant, and it has sufficient spatial resolution to pinpoint individual cities. 

 

TROPOMI's resolution is too coarse to identify where exactly unreported methane is coming from within the city, however. The researchers think that higher-resolution measurements could help cities update their accounts and emission policies.

 

"We, and others in the field, are looking into higher-resolution satellite measurements so that we can tease apart the contribution of large localized sources," Kort said. "Those satellites can't necessarily tell you the whole city's emissions, but they could tell you what individual landfills or facilities are doing."
 

Study: Space-based observation of global increase in urban methane emissions from 2019-2023 (DOI: 10.1073/pnas.2504211123)

---

Journal

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2504211123