Climate and environment updates: 7 key measures of Earth's health in danger, report warns

Fall has always been a season of change, but human-amplified climate change is bringing its own unwanted shifts in temperature.

Meteorological fall, which began Sept. 1, is getting warmer across the United States, affecting everything from public health to ecosystems and agriculture, according to a new analysis by Climate Central.

Since 1970, 237 cities (98% of the areas included in the research) across the U.S. have experienced significant warming during the fall season, with an average increase of 2.8 degrees Fahrenheit.

The Southwest region has experienced the most warming, with Reno, Nevada, El Paso, Texas and Las Vegas, Nevada ranking as the top three cities, warming by 7.7, 6.5 and 6.2 degrees Fahrenheit, respectively.

To streamline data collection and analysis, meteorologists and climate scientists use meteorological seasons that are based on the annual temperature cycle and fixed calendar days. Meteorological fall includes the months of September, October and November.

Extreme heat is the deadliest weather-related hazard in the United States, according to the National Weather Service (NWS). Lingering unseasonably warm conditions can prolong and exacerbate extreme heat dangers, especially for children who are among the most vulnerable to heat-related illnesses and death. Many school-aged children are returning to classrooms without adequate cooling, and after-school activities can further increase their exposure to dangerous heat during the early fall months, according to a report from the Center for Climate Integrity.

The warming trend is also disrupting the typical behavior and activity of many animal and plant species. Shifting seasonal cues is altering the timing of important events like bird migration. At the same time, warmer conditions allow disease-carrying insects such as mosquitoes to remain active later into the fall, increasing the risk of disease transmission, according to the Centers for Disease Control and Prevention (CDC).

While milder fall temperatures can benefit some agricultural crops by extending the growing season, shifting seasons and prolonged heat can be detrimental to fall favorites like apples. Human-amplified climate change is influencing when apples are ready for harvest and affecting their quality, according to the U.S. Department of Agriculture (USDA). Certain varieties, like McIntosh, do not develop as much red color and are less crisp when late summer and early fall temperatures are too high.

-ABC News meteorologist Dan Peck

Extreme heat is the leading cause of weather-related deaths in the United States. However, long before it becomes dangerous or life-threatening, heat can have a profound impact on the human body, especially over time. According to a new study published in Nature Climate Change, one of those long-term effects may be accelerating the human body's aging process.

Researchers analyzed data from nearly 25,000 people in Taiwan between 2008 and 2022. They tracked how an individual's biological age changed compared to the number and intensity of the heat waves they experienced. Their findings suggest that an increase in the frequency and intensity of heat waves can lead to accelerated biological aging.

People who went through more heat waves aged a little faster. Their bodies looked about 8 to 11 days older than those less exposed -- similar to the aging effect seen with smoking or drinking.

"While the number itself may look small, over time and across populations, this effect can have meaningful public-health implications," lead author Cui Guo, an environmental epidemiologist at the University of Hong Kong, said.

Manual workers and residents of rural areas experienced the most pronounced health impacts, likely due to spending more time outdoors and having reduced access to air conditioning. However, the study also found that over the 15 years, the aging impact of heat waves decreased as people adapted to more intense and frequent extreme heat events, a trend consistent with previous studies.

The exact mechanisms behind the adaptation remain unclear. But improved access to air conditioning and enhanced preparedness for extreme heat could be contributing factors, according to the authors.

Since the study focused solely on people in Taiwan, the findings may differ for individuals living in the U.S. and other parts of the world. However, the researchers say their findings underscore the importance of mitigating the more nuisance adverse impacts of heat waves, particularly over time. The findings could pave the way for similar research in other regions, offering a more comprehensive view of how humans are responding to a warming world.

-ABC News meteorologist Dan Peck

Europe's weather satellites are getting an upgrade that will improve the quality of forecasts and climate science around the world.

On Aug. 13, the European Space Agency (ESA) launched the MetOp Second Generation satellite, known as MetOp-SG, the first of a new series of satellites intended to monitor the weather and climate from a polar orbit.

The launch is a collaboration between the ESA and EUMETSAT, Europe's intergovernmental organization that oversees the operations of Europe's weather and climate satellites.

"With increasingly erratic weather patterns, timely and precise forecasting has never been more crucial, and the MetOp-SG mission is now set to play a critical role in improving weather forecasts and climate monitoring. Sentinel-5 too will bring timely data for air pollution monitoring and more," said Simonetta Cheli, ESA's director of Earth Observation Programmes.

On board the new satellite is a suite of new instruments to monitor different climate and weather information, including infrared detectors, a new air-quality monitoring instrument, a cloud and surface imager and an atmospheric aerosol analyzer.

"The data will allow us to monitor air quality, track greenhouse gases, and observe clouds, trace gases and ozone in more detail than ever," said Simonetta Cheli, Director of Earth Observation Programmes at ESA.

According to NOAA, 85 to 95 percent of the data used in weather forecasting models comes from satellites.

"By feeding these insights into models and tools, we can strengthen climate action, improve public health, and deliver benefits for communities across Europe and beyond," Cheli added.

The A1 satellite is slated to be a part of one of the three planned pairs of satellites for the MetOp-SG mission, with each pair having two types of satellites that will carry different, but complementary instruments to capture a wide range of weather and climate data.

"Whether it's droughts, fires or floods, the world needs sharper tools to understand and respond to climate change," said Philippe Chorier, Space Business Development Manager at LYNRED, which designed several of the critical components for the satellite.

These satellites differ from the more well-known geostationary satellites, such as GOES, which orbit in sync with the Earth's rotation, maintaining a fixed view.

The next satellite launch, MetOp-SG-B2, is planned for the summer of 2026. The MetOp-SG satellite series will have satellite launches extending into 2039.

EUMETSAT and the European Space Agency are also planning additional launches of their Meteosat Third Generation satellite series later this year.

"The launch of Metop-SG-A1 is a major step forward in giving national weather services in our member states sharper tools to save lives, protect property, and build resilience against the climate crisis," said Phil Evans, Director General at EUMETSAT.

-ABC News meteorologist Kyle David Reiman

The extreme dry conditions that have persisted for more than two decades across the western United States and the resulting megadrought are likely being fueled by human activity, according to a new study from the University of Colorado Boulder.

Researchers found that the prolonged megadrought in the West is driven by a complex connection with ocean patterns in the Pacific, which are influenced by human-amplified climate change.

"Our results show that the drought and ocean patterns we're seeing today are not just natural fluctuations -- they're largely driven by human activity," said Jeremy Klavans, a postdoctoral researcher in CU Boulder's Department of Atmospheric and Oceanic Sciences and the lead author of the study.

The study found that a natural climate pattern in the north Pacific Ocean, known as the Pacific Decadal Oscillation, or PDO, is being impacted by human-created emissions.

The PDO is a natural variation of warmer and cooler sea surface temperatures across the mid-latitudes of the Pacific Ocean, with conditions along the U.S. West Coast typically opposite to those near Japan.

Natural fluctuations of the PDO, classified as either positive or negative phases, drive large-scale weather patterns over the Pacific and eventually North America. But the PDO has been stuck in its negative phase since the 1990s, with cooler waters in the eastern North Pacific near the U.S. West Coast and warmer waters in the western North Pacific near Japan. Klavans noted that this is quite unusual for the natural cycle of the ocean.

The researchers examined a new collection of over 500 climate model simulations developed by climate scientists around the world. They found that existing models tend to overestimate the role of natural variability and underestimate the impact of greenhouse gas and aerosol emissions on the PDO, concluding that the majority of variations since the mid-20th century were driven by human activity.

"People have been trying for a long time to find out why this part of the country is so dry, and we have an answer for that finally," Klavans said.

A previous study found that this megadrought across the western United States, as well as northwestern Mexico, has become the worst drought across the region in at least 1,200 years.

Klavans noted that if greenhouse gas emissions continue to rise, the PDO will likely remain locked in its negative phase and prolong the megadrought for at least the next three decades. This has far-reaching and long-term impacts, influencing weather patterns and keeping much of the West drier than usual, as cooler air and water hold less moisture.

"This study can allow us to better quantify the costs of continued greenhouse gas emissions for Americans," Klavans said. "That can only help our region plan for a better future."

-ABC News meteorologists Kyle David Reiman and Dan Peck