Ten years ago, , an international treaty��designed to cut greenhouse gas emissions and curtail global warming. Under the treaty, most nations made a 15-year promise to reduce emissions. Now, armed with a decade of data, a new 91̽��-led study shows global progress, but not enough to compensate for the environmental cost of economic growth.

With its adoption in 2015, the Paris Agreement kicked off a concerted effort to reduce emissions by prioritizing renewable energy, reducing waste and tracking impact. The treaty aimed to keep the planet from warming more than 2 degrees Celsius by 2100, with a target of 1.5 C. A new statistical analysis of the data shows that the agreement has helped some nations cut emissions, but the net impact is still too high to curb warming.

“The efforts made in response to the Paris Agreement did change the course of things, but the effects were knocked out by an increase in gross domestic product,” said , a 91̽��professor emeritus of statistics and sociology who led the study.

The results were .

This study is the third in a series of papers by Raftery and colleagues. The first, published in 2017, provided a probability-based assessment of what would happen if every country satisfied its , as defined by the Paris Agreement. The researchers’ predictions were based on three components: total world population, GDP and carbon intensity, a measure of carbon emissions per dollar.

“One of the key findings from that work was that basically, it’s not going to be enough,” Raftery said. “Even if every country met their goal, there was just a 5% chance that we would stay below the 2-degree mark.”

Meeting the collective goal would require everyone to do more, but just how much more was unclear.

Four years later, in 2021, the authors came back to say that emissions goals needed to be about 80% more ambitious to keep warming below 2 C. If each country increased its emissions reduction goal by 1.8% annually, and continued doing so after the Paris Agreement lapses in 2030, temperatures might stay just under the threshold.

This new study updates the statistical methods developed in 2021 and applies them to data collected in the past decade. It reveals that carbon intensity is trending downward by 3.1% each year, compared to 1.1% before the Paris Agreement was signed in 2015.

“It’s an improvement,” Raftery said, but the net result is not positive because world economies grew faster than expected. Even though less carbon was released to produce each economic unit, global GDP increased enough to drive total emissions up.

“Reducing economic growth is unpopular,” Raftery said, and the world population is growing. “So realistically, carbon intensity is the only factor under some kind of policy control.”

Still, the data does contain promising trends. The chance of “the most catastrophic climate change,” where temperature increases by 3 or more degrees, has gone down since 2015, from 26% to 9%. The likelihood of keeping warming below 2 degrees has also increased from 5% in 2015 to 17%.

All countries can and should continue looking for ways to contribute but some have more power than others, according to Raftery. The bigger the economy, the greater its impact on carbon intensity.

China, which is responsible for nearly one-third of total global carbon emissions, saw dramatic economic growth over the past decade. Although the country managed to reduce its carbon intensity 36% by 2024, its emissions shot up as GDP rose.

Both India and Russia followed similar trends, with observed emissions climbing far above their projected goals.

“China and the U.S. have the biggest economies and are among the most wasteful countries,” Raftery said. The carbon intensity for China was three times that for Germany, which is the largest economy in the European Union. Carbon intensity for the U.S. was 50% higher than that for Germany.

When President Donald Trump took office earlier this year, from the Paris Agreement for a second time. After he withdrew during his first term, former President Joe Biden rejoined and pledged that the U.S. would reduce its emissions 60% from peak levels by 2035. To evaluate how the climate will change if the U.S. makes no contribution, the researchers ran the numbers again without it.

If all the other participating countries meet their goals, the projected temperature increase goes up by 0.1 C and the chance of staying below 2 C decreases from 34% to 27%. The researchers note that this is an optimistic projection. It assumes that the U.S. will stop making cuts, but does not account for the possibility that it will reverse the trend by increasing carbon intensity.

“The fact that the Paris Agreement did work in reducing at least carbon intensity is good news,” Raftery said. “There need to be bigger efforts made to offset economic growth, but there is reason for hope.”

Coauthors include and , both former 91̽��graduate students of statistics. This research was funded by the National Institutes of Health.

For more information, contact Raftery at raftery@uw.edu.

Warmer weather across the globe is reshaping the landscape of human health. Case in point:��Dengue fever incidence could rise as much as 76% by 2050 due to climate warming across a large swath of Asia and the Americas, according to a new study led by , a researcher at the 91̽��.��

Dengue fever, a mosquito-borne disease once confined largely to the tropics, often brings flu-like symptoms. Without proper medical care, it can escalate to severe bleeding, organ failure, and even death. ��

The study,, is the most comprehensive estimate yet of how temperature shifts affect dengue’s spread. It provides the first direct evidence that a warming climate has already increased the disease’s toll.����

“The effects of temperature were much larger than I expected,” said Childs, a 91̽��assistant professor of environmental and occupational health sciences who conducted much of the research as a doctoral student at Stanford University. “Even small shifts in temperature can have a big impact for dengue transmission, and we’re already seeing the fingerprint of climate warming.”��

The study analyzed over 1.4 million observations of local dengue incidence across 21 countries in Central and South America and Southeast and South Asia, capturing both epidemic spikes and background levels of infection.����

Dengue thrives in a “Goldilocks zone” of temperatures — incidence peaks at about 27.8 degrees Celsius, or 82 degrees Fahrenheit, rising sharply as cooler regions warm but dropping slightly when already-hot areas exceed the optimal range. As a result, some of the largest increases are projected for cooler, high-population regions in countries such as Mexico, Peru and Brazil. Many other endemic regions will continue to experience larger, warming-fueled dengue burdens. By contrast, a few of the hottest lowland areas may see slight declines.����

Still, the net global effect is a steep rise in disease.��

The findings suggest that higher temperatures from climate change were responsible for an average 18% increase of dengue incidence across 21 countries in Asia and the Americas from 1995 to 2014 — translating to more than 4.6 million extra infections annually, based on current incidence estimates. Cases could climb another 49% to 76% by 2050 depending on greenhouse gas emissions levels, according to the study. At the higher end of the projections, incidence of dengue would more than double in many cooler locations, including areas in the study countries that are already home to over 260 million people.����

“Many studies have linked temperature and dengue transmission,” said senior author, a professor of biology in the. “What’s unique about this work is that we are able to separate warming from all the other factors that influence dengue — mobility, land use change, population dynamics — to estimate its effect on the real-world dengue burden. This is not just hypothetical future change but a large amount of human suffering that has already happened because of warming-driven dengue transmission.”��

The researchers cautioned that their estimates are likely conservative. They do not account for regions where dengue transmission is sporadic or poorly reported, nor do they include large endemic areas such as India or Africa where detailed data is lacking or not publicly available. The researchers also highlighted recent locally acquired cases in California, Texas, Hawaii, Florida, and in Europe — a signal of the expanding range of dengue. Urbanization, human migration and the evolution of the virus could amplify risks, while medical advances may help blunt them, making projections uncertain.��

Aggressive climate mitigation would significantly reduce the dengue disease burden, according to the study. At the same time, adaptation will be essential. This includes better mosquito control, stronger health systems and potential widespread use of new dengue vaccines.��

In the meantime, the findings could help guide public health planning and strengthen efforts to hold governments and fossil fuel companies accountable for climate change damages. Attribution studies are increasingly entering courtrooms and policy debates, used to assign responsibility for climate damages and to support funds compensating countries most affected.����

“Climate change is not just affecting the weather — it has cascading consequences for human health, including fueling disease transmission by mosquitoes,” Mordecai said. “Even as the U.S. federal government moves away from investing in climate mitigation and climate and health research, this work is more crucial than ever for anticipating and mitigating the human suffering caused by fossil fuel emissions.”��

Co-authors of the study include of Arizona State University, of the University of Maryland, and of Stanford. Lyberger and Harris completed much of their work while at Stanford.������

The research was funded by the Illich-Sadowsky Fellowship through the Interdisciplinary Graduate Fellowship program at Stanford University; an Environmental Fellowship at the Harvard University Center for the Environment; the National Institutes of Health; the National Science Foundation (with the Fogarty International Center); �ٳ��  �ٳ��  and the Stanford Woods Institute for the Environment.��

Adapted from a. For more information or to contact the researchers, email Alden Woods at acwoods@uw.edu.

As insect populations decrease worldwide — in what some have called an “insect apocalypse” — biologists seek to understand how the six-legged creatures are responding to a warming world and to predict the long-term winners and losers.

A new study of grasshoppers in the mountains of Colorado shows that, while the answers are complicated, biologists have much of the knowledge they need to make these predictions and prepare for the consequences. The , published Jan. 30 in PLOS Biology, compares thousands of grasshoppers collected in Colorado between 1958 and 1960 with modern-day specimens.

“Understanding what species are likely to be winners and losers with climate change has been really challenging so far,” said corresponding author , a professor of biology at the 91̽��. “Hopefully this work starts to demonstrate some principles by which we can improve predictions and figure out how to appropriately respond to ecosystem changes stemming from climate change.”

Comparing museum specimens and newly collected insects allowed the research team to assess the impact of 65 years of climate change on the sizes of six species of grasshopper. Because insects are cold-blooded and don’t generate their own heat, their body temperatures and rates of development and growth are more sensitive to warming in the environment.

Despite much speculation that animals will to lessen heat stress as the climate warms, the study found that some of the grasshopper species actually grew larger over the decades, taking advantage of an earlier spring to fatten up on greenery.

Growth was seen only in species that overwintered as juveniles and thus could get a head start on chowing down in the spring. Species that hatched in the spring from eggs laid in the fall did not have this advantage and became smaller over the years, likely as a result of vegetation drying up earlier in the summer.

“This research emphasizes that there will certainly be species that are winners and losers, but sub-groups within those species’ populations, depending on their ecological or environmental context, will have different responses,” said co-author , a postdoctoral researcher at both the 91̽��and the University of California, Berkeley.

The authors of the new study predicted much of this based on the lifecycles of the grasshoppers and the environmental conditions at the site.

“We sat down and looked at all that was known about the system, such as elevational gradients and how that should modify responses and how different grasshoppers might respond, with all the wealth of information we knew about their natural history. And while not all our predictions were supported, many of them actually were,” said co-author of the University of California, Berkeley.

The 65-year-old was first assembled over three summers by the late entomologist Gordon Alexander of the University of Colorado Boulder. He not only collected and mounted the specimens from plots in the Rocky Mountains near Boulder, but also documented the timing of six different life stages of the grasshoppers. His death in a plane crash in 1973 left the specimens, pinned in neat rows in 250 wooden boxes, in limbo.

The collection languished until 2005, when , then a postdoctoral fellow at CU Boulder, set about curating the collection and initiated a re-survey of the same sites to collect more grasshoppers.

Nufio and many others eventually collected about 17,000 new grasshopper specimens from the same or similar sites. While the new paper is the first to report the grasshopper size changes between 1960 and 2015, the authors conducted other studies to help explain the patterns.

The insects were from a large group of nondescript grasshoppers in the Acrididae family that are known as . Most graze on many types of plants, though some specialize in grasses. Two species (Eritettix simplex and Xanthippus corallipes) achieve adulthood as early as May; two (Aeropedellus clavatus and Melanoplus boulderensis) mature in mid-June; and two (Camnula pellucida and Melanoplus sanguinipes) mature in late July.

The researchers found that the grasshopper species that achieve adulthood in May increased in size at lower elevations, around 6,000 feet, while the early and late emergers in these locations decreased in size over the decades.

“The data are consistent with grasshoppers either being able to take advantage of warming by getting bigger and coming out earlier, or for grasshoppers to experience stress and get smaller,” Buckley said.

“We would expect similar trends for grasshoppers in mountains in Washington, but some later snow melt in Washington state might alter the importance of seasonal timing,” she added.

Other experiments Buckley performed on in Colorado show some of the same trends.

“We find a pretty similar message with butterflies, which is hopeful to me, in that if we can consider some basic biological principles, we really increase our ability to predict climate change responses,” Buckley said.

At the UW, Buckley’s research group is repeating surveys begun in 1995 of cabbage white butterflies in Seattle and western white butterflies in central Washington to see how those insects might have changed over the past 30 years.

Buckley also recently became an adjunct curator of entomology at the Burke Museum, where she hopes to continue leveraging museum collections for ecological research.

Other co-authors on the new study are , a graduate student in biology at the UW; Simran Bawa of UC Berkeley; and Ebony Taylor, Michael Troutman and Sean Schoville of the University of Wisconsin, Madison. The work was supported by the National Science Foundation.

For more information, contact Buckley at lbuckley@uw.edu, Williams at cmw@berkeley.edu and Sheffer at msheffer@berkeley.edu.

This article is adapted from a UC Berkeley

NSF grants: DEB-1951356, DEB-1951588, DEB-1951364

Amid all the changes in Earth’s climate, sea ice in the stormy Southern Ocean surrounding Antarctica was, for a long time, an odd exception. The maximum winter sea ice cover remained steady or even increased slightly from the late 1970s through 2015, despite rising global temperatures.

That began to change in 2016. Several years of decline led to , more than five standard deviations below the average from the satellite record. The area of sea ice was 2.2 million square kilometers below the average from the satellite record, a loss almost 12 times the size of Washington state. The most recent winter’s peak, recorded in September 2024, was to the previous year’s record low.

91̽�� researchers show that the all-time record low can be explained by warm Southern Ocean conditions and patterns in the winds that circled Antarctica months earlier, allowing forecasts for sea ice coverage around the South Pole to be generated six or more months in advance. This could support regional and global weather and climate models.

The open-access was published Nov. 20 in Nature Communications Earth & Environment.

“Since 2015, total Antarctic sea ice area has dramatically declined,” said lead author , a 91̽��doctoral student in atmospheric and climate science. “State-of-the-art forecasting methods for sea ice generally struggle to produce reliable forecasts at such long leads. We show that winter Antarctic sea ice has significant predictability at six- to nine-month lead times.”

The authors used a global climate model to simulate how ocean and air temperatures, including longer-term cycles like El Niño and La Niña, affect sea ice in the Southern Ocean.

Results showed that the 2023 El Niño was less important than previously thought. Instead, an arching pattern of regional winds, and their effects on ocean temperatures up to six months in advance, could explain 70% of the 2023 record-low winter sea ice. These winds cause ocean mixing in the Southern Ocean that can pull deeper warm water up to the surface, thus suppressing sea ice growth. Winds can also push sea ice poleward toward Antarctica to prevent the sea ice edge from expanding north, transport heat from lower latitudes toward the poles, and generate ocean waves that break up sea ice.

Using the same approach for the 2024 observations correctly predicted that this would be another low year for Southern Ocean sea ice cover.

“It’s interesting that, despite how unusual the winter sea ice conditions were in 2023 and again in 2024, our results show they were remarkably predictable over 6 months in advance,” said co-author , a 91̽��research associate professor of atmospheric and climate science.

Antarctic sea ice is important because it affects marine and coastal ecosystems and interactions between ocean and atmosphere in the Southern Ocean. It also affects global climate by reflecting sunlight in the Southern Hemisphere and influencing ice sheets and global currents.

“Antarctic sea ice is a major control on the rate of global warming and the stability of ice on the Antarctic continent,” Espinosa said. “In fact, the sea ice acts to buttress ice shelves, increasing their stability and slowing the rate of global sea level rise. This ice is also important for marine and coastal ecosystems.”

As summer arrives in the Southern Hemisphere, the remains sparse around Antarctica, close to a record low for this time of the year.

“Our success at predicting these major sea ice loss events so far in advance demonstrates our understanding of the mechanism that caused them,” said co-author , a 91̽��professor of atmospheric and climate science. “Our model and methods are geared up to predict future sea ice loss events.”

The research was funded by the National Science Foundation and the U.S. Department of Energy.

For more information, contact Espinosa at zespinosa97@gmail.com, Bitz at bitz@uw.edu and Blanchard-Wrigglesworth at edwardbw@uw.edu.

From its base at the southwest corner of the Seattle campus, the provides expertise, tools and resources on “all things climate” to partners and communities across the state.

was announced in the spring as the . Mauger is a research scientist with the 91̽��Climate Impacts Group, which now houses the state climatologist’s office. Mauger’s research focuses mainly on water and floods in the context of climate change.

, a 91̽��research scientist and the deputy state climatologist, studies such things as nighttime heat in Seattle and new ways to display weather data, as well as other trends involving heat and drought.

Together, they provide data and share news on whatever’s in the skies. From heat domes to hailstorms, from snowpack to summer drought, they provide perspective on the short-term and long-term weather woes and questions facing Washingtonians.

“Our goal is to help people understand the climate and how it affects their daily lives,” Mauger said.

Right now, many people in the region are curious about the upcoming winter season.

“This year we’re expecting to see a weak La Niña develop in the tropical Pacific Ocean,” Bumbaco said. For Washington that means “on average, we tend to have cooler-than-normal temperatures, a little bit more precipitation, and more snowpack by the end of our winter season during La Niña winters.”

Mauger and Bumbaco also conduct research on changes in rainfall patterns and flood risks, and on temperatures and wildfire risks for the coming season and over the longer term. Visit the Office of the Washington State Climatologist’s website to check out the seasonal , a list of or to subscribe to a on the current state of Washington’s climate.

For more information, contact Mauger at mauger@uw.edu or Bumbaco at kbumbaco@uw.edu.

As Earth faces unprecedented climate change, a look into the planet’s deep past may provide vital insights into what may lie ahead. But knowledge of the natural world millions of years ago is fragmented.

A 15-year study of a site in Bolivia by a joint U.S.-Bolivia team has provided a comprehensive view of an ancient ecosystem when Earth was much warmer than it is today. The researchers’ findings online Nov. 1 by the journal Palaeogeography, Palaeoclimatology, Palaeoecology.

Located in the Andes Mountains of southern Bolivia, the site, known as the — or QHB — was deposited 13 million years ago during the Miocene Epoch, when Earth’s climate was rebounding from a prior period of warming. Globally, temperatures were 3-4 degrees Celsius warmer than today, and mammal biodiversity was increasing markedly.

Today, the site is 11,500 feet above sea level. Back in the Miocene, the site was lower, but exactly how much was a matter of debate. Previous studies using geochemical methods estimated that the Miocene QHB was relatively high, close to 10,000 feet. But the team’s new findings, based on careful analysis of plant and animal fossils and other features at the site, favor an alternative theory: That the Miocene QHB was at a much lower elevation, likely less than 3,000 feet.

“Our new data indicates that this area was once covered by mosaic vegetation with a mix of trees, including palms, bamboos and other grasses,” said lead author , a 91̽�� professor of biology. “Although this vegetation lacks a good comparison in today’s South America, it was likely most similar to modern neotropical dry forest or wooded savanna growing at low elevation.”

A lower-elevation Miocene QHB site has potentially global consequences.

“When put together with previous work at QHB, our study — including looking at fossil soils, turtles and other ectothermic vertebrates, and mammal ecologies — suggests that the��Central Andes still had not undergone substantial uplift by 12 million years ago,” said Strömberg. “This is important because it helps us understand when this major mountain chain formed. The rise of the Andes is thought to have contributed to making tropical South America the most biodiverse area on Earth.”

Understanding ecosystems of the past can help predict what might happen in the future due to human-related climate change.

“Sites like this one in Bolivia are essential for helping us calibrate climate models,” said co-author and project leader , professor of anatomy at Case Western Reserve University. “Our understanding of climate change is based on models, and those models are based on information from the past.”

Between 2007 and 2017, Croft and co-author Frederico Anaya, a professor of geology at Universidad Autonóma Tomás Frías in Bolivia, led six international teams to the QHB to collect fossils. Despite its warmer, forested past, the site today is a high-altitude desert grassland.

During those trips, the team found many different types of fossils: bones and teeth of mammals and other vertebrates, microscopic plant remains, ancient soils, and tracks and traces of insects and other invertebrates. Analyzing these fossils contributed to the researchers’ conclusion that the Miocene QHB was at a lower elevation. For example, fossils from “cold-blooded” animals found at the site — a giant tortoise, a side-necked turtle and a very large snake — suggest the site’s elevation when these animals lived was less than 3,000 feet, based on modern-day distributions of closely related species.

Strömberg studied fossilized phytoliths from QHB. These are microscopic pieces of silica found in the cells and cell walls of plants, and the shapes of phytoliths differ depending on the type of plant they came from. She compared the fossilized phytoliths with those found in contemporary vegetation to identify the assortment of plants at the site during the Miocene.

Layers of volcanic ash and magnetic signatures in rocks at QHB allowed the fossils to be accurately dated. The diversity of preserved material allowed the team to make detailed reconstructions of the plants and animals and their living conditions. The team named 13 new species of fossil mammals based on remains from the site, including marsupials, hoofed mammals, rodents and armadillos. Most of the species have not been found anywhere else in South America and have no modern descendants.

“Nature has a wide variety of body plans, often much greater than the limited variety we see today,” said co-author Russell Engelman, a Case Western Reserve University graduate student who worked on the mammal fossils.

Moving forward, Croft is hoping to study another Bolivian Miocene site of a similar age, but over a longer time period.

“We are getting into uncharted territory in terms of climate, and you have to go deeper in time to get conditions that are similar,” said Croft.

Other co-authors are Beverly Saylor, Case Western Reserve University professor of Earth, environmental and planetary sciences; Angeline Catena, geology professor at Diablo Valley Community College in California; and Daniel Hembree, professor of Earth and planetary sciences at the University of Tennessee. The research was funded by the National Science Foundation.

For more information, contact Strömberg at caestrom@uw.edu.

Adapted from a by Case Western Reserve University.

To deal with those threats and prepare for the impacts still to come, 10 state agencies collaborated on the . Using the latest science as a foundation, the state’s new climate strategy, released Sept. 30, identifies actions that agencies will take to address the top climate change threats facing Washington: drought, changing ocean conditions, flooding, extreme heat, and wildfires and smoke.

The strategy’s creation was directed by the Washington Legislature, bringing together the state departments of agriculture, commerce, ecology, fish and wildlife, health, natural resources, transportation, the Washington State Conservation Commission, the Emergency Management Division and the Puget Sound Partnership. The 91̽��Climate Impacts Group grounded the work with the most up-to-date science and developed a framework to measure progress on climate resilience.

The Legislature has also directed the 10 agencies to update the plan every four years to incorporate the latest science, resources and concerns into the strategy.

“This plan gives our state a road map to respond to major climate impacts like wildfires, smoke, severe heat, drought and flooding,” said , interim director of the 91̽��Climate Impacts Group, which acts as a hub for climate information and adaptation strategy for Washington state agencies and communities. “By understanding what the state can do, what resources are available, and where they can have the greatest impact, we can limit the damage caused by these events, protecting lives, livelihoods and the environment that supports us all.”

In the plan, each of the responsible agencies will act as the lead for specific actions, based on their existing roles and expertise.

“Washington got lucky this summer. We had fewer major wildfires and more moderate drought,” said Laura Watson, director of the state Department of Ecology. “We know that was just a temporary reprieve. We’ve seen devastating proof in recent years of how vulnerable our state is. We are very susceptible to rising temperatures, summer wildfires, drought and winter floods. We have to prepare now so we’re ready for what’s to come.”

91̽��Climate Impacts Group contributors also included , Washington’s State Climatologist, and , a climate resilience specialist. , who’s now deputy director at the , of which the 91̽��is a member, contributed while based at the 91̽��Climate Impacts Group.

Adapted from a Department of Ecology . For more information, contact Stowe at stowec@uw.edu.

A launch event will take place 11 a.m. Thursday, Oct. 10, at the UW. Space is limited but reporters are welcome to register . At the launch, 91̽��researchers who contributed to the 5th National Climate Assessment will also share the latest science and findings from the assessment’s Northwest chapter.��

Many Tribes in Washington and Oregon call coastal areas home, meaning they are especially affected by climate change. They also face changes in wildfire risk and in changes to fisheries that are economically and culturally important.

A led by the 91̽��’s Climate Impacts Group, the Affiliated Tribes of Northwest Indians, and Washington Sea Grant compiles the experiences of Washington and Oregon coastal Tribes as they prepare for climate change. The report aims to build on successes and identify common barriers to progress.

“Every year the climate crisis continues to elevate and accelerate. The lack of a coordinated federal response is what causes Northwest coastal Tribes — and other coastal communities — to suffer from hazards which are imminently impacting life, property, Tribal rights and resources,” said project co-lead of the . “With direct quotes from Tribal citizens and staff with lived personal and professional experiences, [this report] describes the immediate urgency of the federal government to take coordinated climate action.”

Results will be shared with Northwest coastal Tribes and other governmental and nongovernmental entities.

“The report is based on listening sessions with Northwest coastal Tribes, and summarizes the barriers and unmet needs they face in their efforts to prepare for climate change,” said project co-lead Meade Krosby, who is director of the UW-based and senior scientist at the 91̽��. This report was funded by the National Oceanic and Atmospheric Administration through the .

The project team held six Tribal listening sessions, each 2.5 hours long, in varying formats. Three listening sessions took place during Affiliated Tribes of Northwest Indians conferences already attended by many Northwest coastal Tribal members.��Two sessions were held virtually, and one was hosted by an individual Tribal Nation. Participants in each session met in small groups and shared information with each other and with a moderator.

All participants had the choice of making their comments public or not, and of contributing anonymously or under their name. Researchers later coded all the contributions and summarized the overall findings. Contributions represented 13 Tribal nations, roughly half of the federally recognized Tribes within the study’s coastal regions. The overall findings include:

• Despite being national leaders in climate adaptation, Northwest coastal Tribes face significant needs in realizing their adaptation goals
• Key barriers and unmet needs centered in five areas: funding, staffing, technical expertise, partnerships and communications
• Successful efforts noted strengths in many of these same areas, such as securing external funding, the dedication of Tribal staff, and building robust partnerships

Participants described specific situations and frustrations, including the piecemeal nature of federal funding; challenges recruiting and retaining key staff; potential partners’ lack of familiarity with Tribal processes and priorities; and establishing stable support for long-term initiatives.

Participants’ quotes included:

“If you just looked at the total amount of Tribal land, you’d say: ‘Well, there’s lots of places that the Tribe can move,’ but if you take away all the places that are sacred or culturally significant, or habitat for important species, or landslide hazard, or some other hazard, the options are diminished. We must also be careful not to move away from one hazard into another. How bad would it be if we move away from the shoreline, and we put ourselves in harm’s way for fire?”

– Robert Knapp, environmental planning manager and climate resilience lead, Jamestown S’Klallam Tribe

“Some of the challenges that we face on the coast are due to the magnitude of some of the projects that we need to undertake. For example, we are in the midst of relocating our two main Quinault villages on the Washington coast. That’s a multimillion-dollar, multi-agency effort … It’s very difficult to integrate our plans and priorities for village relocation with those of the agencies and constrains on available funding.”

– Gary Morishima, natural resources technical advisor, Quinault Indian Nation

“To build capacity we need funding sources that are long-term, that we can say to Tribal leadership: ‘We know we’re going to have funding for five or six years, so we want to hire this person who’s an engineer, who’s a project manager, who can take on these projects, talk to other [external] engineers, and who can make these projects happen.’”

– Rochelle Blankenship, Tribal council member and executive director, Jamestown S’Klallam Tribe

The report concludes: “While these findings do not fully represent the depth and breadth of [the challenges faced by Northwest coastal Tribes] and what is required to address them, we hope they will help build awareness among funders, policymakers, climate service providers and others to mobilize necessary action in support of the climate adaptation efforts of Northwest coastal Tribes.”

In related upcoming work, the Northwest Climate Resilience Collaborative’s Tribal Coastal Resilience effort at the 91̽��was as part of a to support coastal readiness in Washington state.

The grant will support hiring a full-time climate adaptation specialist to provide technical assistance to Northwest coastal Tribes, Krosby said. That person will also coordinate a small grants program that will distribute most of the funds to Tribes to support their adaptation efforts. The grants program was designed to respond to Tribal priorities without imposing barriers that often make funds difficult to apply for and administer. Awards will be made starting in 2025.

“We’re really excited that this is happening at the same time our report is coming out,” Krosby said. “So it’s not just describing the problem. It’s also: Here, let’s bring some resources to bear based on what we learned.”

Other co-authors on the report are Ryan Hasert at the 91̽��Climate Impacts Group; Kylie Avery at the Affiliated Tribes of Northwest Indians; and Chandler Countryman and Melissa Poe at UW’s Washington Sea Grant. The project’s Tribal advisory group and report reviewers include representatives from the Makah, Tulalip, Coquille, Squaxin Island, Swinomish and Quinault Tribes and the Northwest Indian Fisheries Commission.

For more information, contact Marchand at amarchand@atnitribes.org, and Krosby at mkrosby@uw.edu or 206-579-8023.��

Corn is one of the planet’s most important crops. It not only provides sweet kernels to flavor many dishes, but it’s also used in oils, as a sweetener syrup, and as a feed crop for livestock. Corn has been bred to maximize its yield on farms around the world.

But what will happen under climate change? Research led by the 91̽�� combined climate projections with plant models to determine what combination of traits might be best adapted to future climates. The study used projections of weather and climate across the U.S. in 2050 and 2100 with a model that simulates corn’s growth to find the mix of traits that will produce the highest, most reliable yield under future conditions across the country.

The open-access was published in April in Environmental Research Food Systems. 91̽��News asked senior author , a 91̽��professor of atmospheric sciences and of biology, about the study and its findings.

Our future climate will be warmer, have drier air and have a higher concentration of atmospheric carbon dioxide. Is there a broad understanding of how all these changes together will affect plant growth?

Abigail Swann: For corn, a by our group found that higher temperatures and drier air have about the same size impact, with both leading to less corn yield, while more CO2 available for photosynthesis increased yield. The increase in yield from CO2 wasn’t enough to counteract the decrease from the other two changes, however, so corn yields went down overall.

Overall, hotter temperatures like those we expect in the future will make crops grow faster but be less productive. Of course, shifts in precipitation also affect their growth in different locations, though that has less impact overall, and particularly for agricultural crops that rely on irrigation.

Typically, many people think of climate change as something that will shift where certain crops can grow. Your study says the crop varieties we plant today aren’t ideal for any location in the future. Why is that?

AS: As climate continues to warm, we can adapt by moving existing crop varieties closer to the poles, where the air is cooler. But shifting existing varieties to new places isn’t enough to make up for the loss in crop yield that we expect in a hotter climate because the impacts of higher temperatures are so detrimental.

Our study looked at 100 possible corn varieties, and we find that those that will be most successful in the future are not varieties that are successful now — we need new crops for the new climate.

Can you describe the corn that will perform best in future climates, according to your study, compared to the varieties that do best today?

AS: Corn plants first grow leaves, and then switch to growing grain. We find that today, corn plants must make a tradeoff between growing a lot of leaves and still having enough time left in the growing season to grow a lot of grain. This means the most successful varieties today don’t grow very many leaves, so they can switch to growing grain early in the season.

Growing more leaves could potentially allow corn to increase how much the plant can photosynthesize, which would also increase how much grain it could grow, but today this comes at a cost of a shorter growing season.

In the future, it will be warmer overall, and corn may be planted earlier and harvested later in the season. This longer growing season relieves corn from this tradeoff and allows it to both grow more leaves and still have plenty of time to grow grain (there is an additional boost from faster growth under hotter temperatures).

So basically, in this sense the corn plants of the future can have their cake and eat it too. The varieties we simulated that took advantage of the ability to grow more leaves yielded more under future climate than the varieties with less leaf growth. This isn’t good news for corn, though. While corn will be able to grow more leaves and still have plenty of time to grow grain, the adverse impacts of hot temperatures and drier air will decrease the overall yields. Growing more leaves and having a longer growing season help buffer these adverse impacts, but overall, all of the corn plants we simulated did worse under future climate conditions.

Is there any way to verify these results on real plants before these climate conditions become reality?

AS: While the plants that we found would do best under future climate conditions don’t exist right now, plants with many of these characteristics can be bred quickly, using genetic techniques like CRISPR. Then they can be grown under controlled climate conditions to see if our findings hold up for real plants. That part of the process is surprisingly fast, so we can create and trial new plant varieties before they are needed.

Why is it helpful to use computer models, rather than just selective breeding as has been done in the past?

AS: Breeding new crop varieties is a very slow process. It can take decades to go from initial breeding to testing and adoption by farmers. The process starts with selecting among the existing crop varieties for desirable characteristics, including high yield. Then these new potential varieties are combined, grown and tested in multiple environments and with different management. Finally, the final varieties are released commercially and then can be adopted by farmers.

With simulations we can test a much wider range of possible combinations of characteristics that could work well for a new variety, and use that knowledge to guide the first stages of breeding. This can speed up the breeding process and accelerate our ability to adapt to a changing climate. It also gives us information about what characteristics we might try to create that are farther from our existing varieties.

How does your study fit into the broader field of climate adaptation?

AS: We will need to adapt agriculture in many ways to support a growing population with a growing demand for food, combined with the loss in crop yield that we expect as climate gets hotter. Our study helps to jumpstart the process of breeding climate-resilient crops by envisioning what those crops should look like. Our study also provides a blueprint for how to do this analysis for other crop types, besides corn.

Although we focus on corn for this study, we see our work as a demonstration of an approach that can be applied to any crop, and so more of a blueprint of how we can incorporate the expected impacts of climate change into the breeding of new crop varieties.

In the U.S. we heard recently about population leveling off due to lower birth rates and about shifts to less resource-intensive, plant-based diets. Can you explain why, worldwide, we still expect an increase in demand for corn?

AS: Worldwide population is still growing, and in addition to growing in total number, the global population is growing more affluent and increasing its consumption of meat. In the U.S. our diet is already very meat-intensive, and so shifts towards less resource-intensive and plant-based diets make a lot of sense from a health and environmental standpoint.

But meat consumption in many parts of the world is currently very low. As these populations increase their wealth, we expect that in some cases meat consumption will grow. This increase in wealth is a good thing for the well-being of those people. By adapting agriculture, we hope to buffer the losses in yield expected from hotter temperatures and help provide enough food for everyone.

What’s next for this research?

AS: We would like to work with breeders to create some of the corn varieties our study proposed, and do similar studies on other major global food crops. We are currently seeking additional funding sources to conduct these next steps.

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Lead author did the work as part of her 91̽��doctoral degree in biology. Co-authors are , 91̽��professor of environmental and forest sciences; at the U.S. Department of Agriculture; and at Colorado State University. The research was funded by the National Science Foundation, the U.S. Department of Agriculture and the UW’s Royalty Research Fund.

For more information, contact Swann at aswann@uw.edu.

As carbon dioxide accumulates in the atmosphere, the Earth will get hotter. But exactly how much warming will result from a certain increase in CO2 is under study. The relationship between CO2 and warming, known as climate sensitivity, determines what future we should expect as CO2 levels continue to climb.

New research led by the 91̽�� analyzes the most recent ice age, when a large swath of North America was covered in ice, to better understand the relationship between CO2 and global temperature. It finds that while most future warming estimates remain unchanged, the absolute worst-case scenario is unlikely.

The open-access was published April 17 in Science Advances.

“The main contribution from our study is narrowing the estimate of climate sensitivity, improving our ability to make future warming projections,” said lead author , a 91̽��doctoral student in atmospheric sciences. “By looking at how much colder Earth was in the ancient past with lower levels of greenhouse gases, we can estimate how much warmer the current climate will get with higher levels of greenhouse gases.”

The new paper doesn’t change the best-case warming scenario from doubling CO2 — about 2 degrees Celsius average temperature increase worldwide — or the most likely estimate, which is about 3 degrees Celsius. But it reduces the worst-case scenario for doubling of CO2 by a full degree, from 5 degrees Celsius to 4 degrees Celsius. (For reference, CO2 is currently at 425 ppm, or about 1.5 times preindustrial levels, and unless emissions drop is headed toward double preindustrial levels before the end of this century.)

As our planet heads toward a doubling of CO2, the authors caution that the recent decades are not a good predictor of the future under global warming. Shorter-term climate cycles and atmospheric pollution’s effects are just some reasons that recent trends can’t reliably predict the rest of this century.

“The spatial pattern of global warming in the most recent 40 years doesn’t look like the long-term pattern we expect in the future — the recent past is a bad analog for future global warming,” said senior author , a 91̽��associate professor of atmospheric sciences and of oceanography.

Instead, the new study focused on a period 21,000 years ago, known as the Last Glacial Maximum, when Earth was on average 6 degrees Celsius cooler than today. Ice core records show that atmospheric CO2 then was less than half of today’s levels, at about 190 parts per million.

“The paleoclimate record includes long periods that were on average much warmer or colder than the current climate, and we know that there were big climate forcings from ice sheets and greenhouse gases during those periods,” Cooper said. “If we know roughly what the past temperature changes were and what caused them, then we know what to expect in the future.”

Researchers including co-author , a 91̽��professor of atmospheric sciences, have created new statistical modeling techniques that allow paleoclimate records to be assimilated into computer models of Earth’s climate, similar to today’s weather forecasting models. The result is more realistic temperature maps from previous millennia.

For the new study the authors combined prehistoric climate records — including ocean sediments, ice cores, and preserved pollen — with computer models of Earth’s climate to simulate the weather of the Last Glacial Maximum. When much of North America was covered with ice, the ice sheet didn’t just cool the planet by reflecting summer sunlight off the continents, as previous studies had considered.

By altering wind patterns and ocean currents, the ice sheet also caused the northern Pacific and Atlantic oceans to become especially cold and cloudy. Analysis in the new study shows that these cloud changes over the oceans compounded the glacier’s global cooling effects by reflecting even more sunlight.

In short, the study shows that CO2 played a smaller role in setting ice age temperatures than previously estimated. The flipside is that the most dire predictions for warming from rising CO2 are less likely over coming decades.

“This paper allows us to produce more confident predictions because it really brings down the upper end of future warming, and says that the most extreme scenario is less likely,” Armour said. “It doesn’t really change the lower end, or the average estimate, which remain consistent with all the other lines of evidence.”

The research was funded by the National Science Foundation, the Department of Defense’s National Defense Science and Engineering Graduate Fellowship, the Alfred P. Sloan Foundation, the National Oceanic and Atmospheric Administration and the European Union’s Horizon 2020 program. Other co-authors are Jessica Tierney at the University of Arizona; Matthew Osman at the University of Cambridge in the U.K.; Cristian Proistosescu and Philip Chmielowiec at the University of Illinois Urbana-Champaign; Yue Dong at the University of Colorado; Natalie Burls at George Mason University; Timothy Andrews at the U.K. Met Office Hadley Centre; Daniel Amrhein and Jiang Zhu at the NSF National Center for Atmospheric Research in Boulder; Wenhao Dong at the University Corporation for Atmospheric Research in Boulder and Geophysical Fluid Dynamics Laboratory; and Yi Ming at Boston College.

For more information, contact Cooper at vcooper@uw.edu or Armour at karmour@uw.edu.