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The document reports that 2023 is virtually certain to be the hottest year on record, with global surface temperatures from January to November 2023 ranking highest in the 144-year record at 1.4°C above the 1881-1910 baseline. In the U.S., 25 billion-dollar weather and climate disasters occurred between January and November 2023, surpassing the previous annual record of 22 in 2020. These events caused an estimated 482 deaths and $81 billion in damages, with severe storms accounting for 76% of these disasters. The average time between such disasters in 2023 dropped to 10 days, compared to 82 days in the 1980s.

The document outlines the bidirectional relationship between aviation and climate change, noting that global air travel emitted over 780 Mt CO2 in 2022 while simultaneously facing operational disruptions from the resulting warming. It identifies five primary climate-driven disruptions: coastal flooding threatening airport infrastructure, high temperatures reducing aircraft lift and capacity, increased lightning strike risks, shifting jet stream patterns affecting flight duration, and a rise in severe clear-air turbulence. The text emphasizes the need for the aviation industry to implement adaptation measures, such as coastal defenses and adjusted flight scheduling, to maintain safety and manage costs.

An analysis of 241 U.S. locations from 1970 to 2022 shows that 82% experienced rising November temperatures, with an average increase of 2.1°F.

Climate Central's analysis of U.S. locations from 1970 to 2022 shows that winter is the fastest-warming season for 74% of analyzed sites, with average winter temperatures increasing in 97% of locations. This warming is characterized by more warmer-than-normal days, fewer freezing nights, and shrinking cold snaps, particularly in the Northeast and Upper Midwest. These trends affect critical sectors including the $27 billion fruit and nut industry, western water supplies, and residential energy use.

Climate Central's analysis using the Climate Shift Index (CSI) reveals that 90% of the global population experienced at least 10 days of temperatures strongly influenced by climate change between November 2022 and October 2023. The study highlights that one in four people faced extreme heat streaks of at least five days driven by carbon pollution, with the strongest influences observed in the developing world and specific high-impact areas like Jamaica and several U.S. cities.

The period from November 2022 to October 2023 was the hottest 12-month stretch in recorded history, with a global average temperature 1.32°C above the pre-industrial baseline. Using the Climate Shift Index (CSI), Climate Central found that 90% of the global population (7.3 billion people) experienced at least 10 days of temperatures very strongly affected by climate change (CSI level 3 or higher). Approximately 1.9 billion people (24%) experienced a five-day heat wave strongly influenced by carbon pollution (CSI level 2 or higher). The report highlights an inequitable distribution of impacts, with small island developing states and least developed countries facing higher exposure, although heat waves also occurred in G20 nations. The analysis also links human-induced climate change to severe weather events, including deadly flooding in Africa and Libya, and record-breaking wildfires in Canada and Hawaii.

Since 1970, fall temperatures in the U.S. have increased by 2.7°F on average, with October nights warming by 2.2°F. Analysis of 244 U.S. cities shows that 89% have experienced warming October nights, and 153 locations saw increases exceeding 2°F.

Climate Central analyzed precipitation data from 1969-70 to 2022-23 for the contiguous U.S., finding that while some regions have balanced seasonal rainfall, others rely heavily on a single season. Specifically, the West and Northwest are dominated by winter precipitation, while the Plains and Upper Midwest rely on summer rainfall. Climate change is altering these patterns, with a general increase in precipitation east of the Rockies and a decrease to the west. Warmer temperatures are increasing atmospheric moisture—approximately 10% more since 1970—which enhances extremes such as heavy downpours and intensifying droughts.

The document reports that the average person in the U.S. breathed more harmful wildfire smoke in 2023 than in any year since 2006, driven largely by record-shattering wildfires in Canada. It details how fine particle pollution (PM2.5) from these fires travels thousands of miles, affecting every county in the contiguous U.S. and stalling air quality improvements in 30 states. The text links these trends to a warming climate and increasing 'fire weather,' noting that human-caused climate change accounts for at least two-thirds of the rapid increase in fire weather in the western U.S.

The document reports that the annual frequency of high tide flooding in the U.S. has more than doubled since 2000 and is projected to more than triple again by 2050. This trend is driven by global sea level rise caused by ocean warming and melting ice, with U.S. coasts expected to see as much rise in the next 30 years (10-12 inches) as they did in the last 100 years. High tide flooding, which occurs when water levels exceed 1-2 feet above the daily average high tide, disrupts infrastructure, ecosystems, and supply chains, particularly affecting the Northeast, Southeast, and Gulf Coasts.

Analysis using the Climate Shift Index (CSI) reveals that 97% of the U.S. population experienced at least one summer day in 2023 with temperatures made at least twice as likely by climate change. The strongest impacts were concentrated in the U.S. South, Southwest, and Southeast, with San Juan, Puerto Rico, and Victoria, Texas, among the most affected cities. The period was also characterized by record-breaking heat streaks and a record number of billion-dollar weather disasters in the U.S.

Analysis using the Climate Shift Index (CSI) shows that human-caused climate change significantly increased the likelihood of record-shattering heat during the June-August 2023 period. Approximately 48% of the global population experienced at least 30 days where heat was made at least three times more likely by climate change (CSI level 3 or higher). The report highlights a stark inequity in exposure, noting that countries with the lowest historical emissions experienced three to four times more days of very strong climate fingerprints than G20 countries.

Analysis of 241 U.S. locations from 1970 to 2022 shows that fall temperatures have increased by an average of 2.4°F in 232 cities, with the most intense warming occurring in the Southwest. This trend is characterized by an increase in above-normal fall days, which prolongs risks related to heat-related illness, wildfires, and allergies, while increasing energy demand for cooling.

Global sea surface temperatures reached unprecedented levels from April to July 2023, driven primarily by human-caused carbon pollution and El Niño. This warming increases the likelihood of rapid intensification in hurricanes and causes severe heat stress for coral reefs, particularly around Florida and the Caribbean. The document highlights that 48% of the global ocean experienced marine heat waves in July 2023, and warns that 70–90% of tropical coral reefs could disappear even if warming is limited to 1.5°C.

Analysis of July 2023, likely Earth's record hottest month, shows that human-caused climate change significantly increased the likelihood of extreme heat globally. Using the Climate Shift Index (CSI), the report finds that 6.5 billion people experienced at least one day where heat was at least three times more likely due to climate change. Particularly strong influences were noted in the Caribbean, Mexico, the southern U.S., and parts of Africa and Asia. In the U.S., 73% of the population experienced at least one day at CSI level 3 or higher, with several cities in Florida, New Mexico, and Arizona showing the strongest climate fingerprints.

The analysis finds that July 2023 was likely Earth's hottest month on record, with human-caused climate change making extreme heat significantly more likely for a vast majority of the global population. Using the Climate Shift Index (CSI), the report demonstrates that 81% of people experienced at least one day where temperatures were at least three times more likely due to climate change. The strongest signals were observed in tropical regions and small island developing states, where conditions were often five times more likely due to human influence. The report highlights specific record-breaking temperatures in Africa, Asia, Europe, and North America, emphasizing that such extremes will increase in frequency as long as fossil fuel combustion continues.

The document argues that climate change is increasing the frequency and intensity of floods, which leads to damp buildings and the growth of mold. This process degrades indoor air quality and poses significant respiratory and mental health risks, particularly for vulnerable populations. It highlights that mold can grow on absorbent materials within two to three days after a flood and notes that in the U.S., up to 20% of common respiratory infections may be attributed to dampness and mold.

Climate Central analyzed 18,945 census tracts across 44 major U.S. cities, finding that 41 million people (approximately 55% of the analyzed population) live in areas where the urban heat island (UHI) effect increases temperatures by 8°F or more. The study identifies albedo, green space percentage, and population density as the primary drivers of this effect, with New York City exhibiting the highest average UHI index. The analysis categorizes cities by heat patterns—concentrated cores, diffused zones, or sprawling intensity—and highlights that structural inequities often lead to disproportionate heat exposure for people of color and low-income populations.

The document describes a six-step process to calculate the Urban Heat Island (UHI) index for U.S. cities by overlaying city boundaries, census tracts, and Land Cover Zone (LCZ) maps. The methodology involves calculating the percentage of various LCZ types within each tract and applying temperature parameters based on impervious cover, permeable surfaces, building height, albedo, and population density. City-wide values are then determined by summing the population in census tracts that exceed specific UHII temperature thresholds.

Climate Central reports that 97% of 240 analyzed U.S. locations saw an increase in annual cooling degree days (CDD) between 1970 and 2022, with the most significant rises in the Southwest, South, and Southeast. Projections suggest U.S. household cooling demand will increase by 71% by 2050, while global demand is expected to more than triple. The document highlights that rising demand can strain power grids, increase greenhouse gas emissions from fossil fuels and HFCs, and exacerbate urban heat islands. It also notes a disproportionate energy burden on low-income and minority households, who may delay cooling use due to cost. Proposed solutions include transitioning to renewable energy, adopting high-efficiency heat pumps, and implementing building retrofits.