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

The summer of 2025 (June to August) was the third-warmest on record for the Northern Hemisphere, surpassed only by the two previous ones in 2024 and 2023, according to new data analyzed by the Copernicus Climate Change Service (C3S).

Globally, last month also ranked as the third-warmest August on record, with an average surface air temperature of 61.88 degrees Fahrenheit.

While global air and sea surface temperatures are currently falling short of record highs, climate scientists warn this pause is unlikely to last as human-caused greenhouse gas emissions continue to fuel the long-term warming trend. Scientists anticipated a temporary decrease in global temperatures due to the recent La Niña event in the Pacific Ocean. This climate pattern usually results in a short-lived drop in global average temperatures.

The world's oceans remain warmer than average across the globe. Between the latitudes of 60 degrees south and 60 degrees north, the average global sea surface temperature was 69.48 degrees Fahrenheit, the third-highest value on record for August, according to Copernicus.

While the Atlantic Basin is currently quiet in terms of hurricane activity, unusually warm sea surface temperatures can play a key role in tropical cyclone development when more favorable atmospheric conditions return in the coming weeks.

In the polar regions, sea surface temperatures also frequently registered above average, negatively impacting sea ice. Antarctic sea ice coverage was 7% below average in August, ranking as the third-lowest value on record for the month. In the Arctic, it registered 12% below average, Copernicus said.

The Arctic region is warming much faster than the global average. After serving as a vital carbon sink for thousands of years, it has turned into a source of carbon dioxide emissions due to rapidly warming conditions and increasing wildfire activity, according to the National Oceanic and Atmospheric Administration.

-ABC News meteorologist Dan Peck

The Amazon rainforest plays a vital role in regulating our climate and is one of the most biologically diverse ecosystems on Earth. But recent shifts in land use, vegetation and climate have disrupted the delicate balance between ecosystems and the atmosphere, significantly impacting the water, energy and carbon cycles of the rainforest. The full extent and long-term consequences of these disruptions, however, are not fully understood.

Now, for the first time, research led by scientists at the University of São Paulo in Brazil has identified the impacts of forest loss and human-amplified climate change on the Amazon.

To differentiate the regional effects of deforestation from the global impacts of climate change, researchers analyzed long-term atmospheric and land cover data from 29 sites across the Amazon, between 1985 and 2020.

The findings, published Tuesday in Nature Communications, show that deforestation accounted for a nearly 74% of the reduction in rainfall over the 35 years. It also accounted for 16.5% of the temperature increase during the Amazon's dry season. The researchers found global climate change was largely behind the warming trend.

Researchers focused their study on the dry season, as previous studies have shown that the regional climate effects of deforestation are more substantial and more consequential during this time. It's when the forest is most vulnerable to moisture deficits, and surface–atmosphere interactions become more pronounced.

The team warns that if deforestation remains unchecked, a further decline in total precipitation during the dry season and an even greater rise in temperature could occur. They say the findings underscore the importance of restoring and maintaining forest cover in the Amazon as a "crucial strategy for mitigating climate change and ensuring the stability of ecosystems."

In November, the government of Brazil, home of the Amazon, will host the 30th Conference of the Parties to the U.N. Framework Convention on Climate Change (COP30). Since the conference is being held in the Amazon, forests are expected to be a key topic of discussion.

"Forests can provide a crucial reprieve in the climate action agenda amidst a rapidly narrowing window of opportunity," COP30 President André Corrêa do Lago said in his inaugural official letter to the conference earlier this year.

-ABC News meteorologist Dan Peck

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