Search Climate Insights Directory

A World Weather Attribution analysis concludes that the extreme heatwave affecting the Sahel in early 2024, which coincided with Ramadan and power cuts, would have been impossible without the 1.2°C of global warming caused by human activities. The event was particularly severe in Mali and Burkina Faso, where 5-day maximum temperatures had a return time of 200 years. The study finds that human-induced warming increased 5-day maximum temperatures by 1.5°C in Mali/Burkina Faso and 1.4°C across the wider Sahel, while the current El Niño event contributed only a small amount (approximately 0.2°C). In Bamako, Mali, the Gabriel Touré hospital reported 102 deaths between 1-4 April, significantly exceeding the 130 deaths recorded for the entire month of April 2023.

A study of heavy rainfall in eastern Mindanao (Caraga and Davao regions) between December and February found a strong upward trend in extreme rainfall in observations, though climate models failed to replicate this trend, preventing a quantified attribution to human-induced climate change. The analysis notes that El Niño typically reduces rainfall in this region during the Northeast monsoon, suggesting rainfall could have been more extreme without it. High vulnerability to flooding is attributed to poverty, protracted conflict, deforestation, urban wetland loss, and stalled disaster risk management policies, including the failure of automated sensors since 2022.

An attribution study by the World Weather Attribution initiative found that human-induced climate change doubled the likelihood of the heavy precipitation associated with Storm Bettina and increased its intensity by approximately 5 percent. In contrast, the study found no clear evidence that climate change influenced the wind speeds of the event, attributing observed decreases in wind speed to natural variability. The analysis notes that warming increases the proportion of precipitation falling as rain rather than snow, exacerbating flood damages, and that the ongoing Russia-Ukraine war increased the vulnerability of affected populations.

The study finds that human-induced climate change and a positive phase of the Indian Ocean Dipole (IOD) contributed approximately equally to the magnitude of extreme rainfall in the Horn of Africa during the 2023 OND season. While the IOD is a natural oscillation, the warming of 1.2C from fossil fuel combustion approximately doubled the rainfall magnitude. The researchers report high confidence that climate change increased rainfall intensity, though they have low confidence in the specific quantification due to limited model correlation and short records. The impact was compounded by previous droughts, unsustainable land management, and systemic challenges in early warning systems, leading to over 300 deaths and the displacement of more than one million people in Kenya and Somalia.

A study by World Weather Attribution found that human-induced climate change significantly increased the intensity and likelihood of an early spring heat event in South America, which affected Argentina, Brazil, Paraguay, and Bolivia. The event, occurring approximately once every 30 years in the current climate, would have been 1.4 to 4.3 °C cooler without human-caused warming. The study notes that the likelihood of such an event has increased by at least 100 times due to climate change. Future warming of 2°C above pre-industrial levels is projected to make similar events five times more likely and 1.1 to 1.6 °C hotter. The researchers highlight a lack of heat action plans in the affected region, which increases vulnerability for the urban poor and ecosystems, despite the fact that adaptation can reduce morbidity and mortality.

A World Weather Attribution study found that human-induced climate change significantly increased the likelihood and intensity of extreme rainfall events in the Mediterranean region in September 2023. In Libya, a 1-in-300 to 600 year event became up to 50 times more likely and 50% more intense compared to a 1.2C cooler climate. In a region encompassing Greece, Bulgaria, and Türkiye, similar events became up to 10 times more likely and 40% more intense. The study highlights that while climate change exacerbated the weather, the scale of the disaster—particularly in Libya—was compounded by state fragility, lack of dam maintenance, and inadequate emergency communication.

The research finds that human-induced climate change significantly increased the intensity and probability of extreme fire weather in eastern Canada in 2023, particularly in Québec, where the cumulative severity of the fire season was approximately 50% more intense and at least seven times more likely to occur.

A collaborative study by international scientists found that the extreme heatwave in the Western Mediterranean from 26-28 April 2023 was likely made at least 100 times more probable by human-induced climate change. The event, which saw temperatures up to 20 degrees higher than normal and broke national records in Spain and Portugal, would have been at least 2°C cooler in a world 1.2°C colder. The researchers note that climate models likely underestimate the increase in extreme heat in Western Europe, suggesting their findings are conservative.

The study finds that while human-induced climate change did not significantly alter the likelihood of the overall 24-month rainfall deficit, it drastically increased drought severity through higher temperatures and evapotranspiration. In a world 1.2°C cooler, the combination of low rainfall and high evapotranspiration observed would not have led to drought; however, in the current climate, it is classified as an 'exceptional drought'. The researchers estimate that such droughts have become approximately 100 times more likely due to climate change.

The analysis finds that while the low rainfall during the October-December 2022 period in Central South America cannot be attributed to climate change and is partly driven by La Niña, human-induced climate change likely reduced water availability by increasing temperatures and evapotranspiration. This exacerbates the agricultural drought, which has already caused severe crop losses in Argentina and water shortages in Uruguay.

World Weather Attribution (WWA) reports on its activities from October 2021 to October 2022, during which it published eight rapid analyses and several peer-reviewed papers. These studies examined the role of human-induced climate change in events such as heatwaves in India, Pakistan, and the UK, as well as flooding and droughts in various regions. The organization emphasizes that while climate change is a major driver for heatwaves, its role in other events like tropical cyclones can be less clear, often compounding with high levels of vulnerability to increase human impacts.

The analysis finds that human-caused climate change made the July 2022 UK heatwave, which saw record temperatures of 40.3°C, at least 10 times more likely. Observational data suggests such a heatwave would have been approximately 4°C cooler in preindustrial times, while model-based estimates suggest a 2°C difference in a 1.2°C cooler world. The event was extreme even in the current climate, with some 1-day maximum temperatures having return periods of 1 in 1000 to 1500 years.

A collaborative scientific study found that human-induced climate change approximately doubled the probability of the extreme 2-day rainfall that caused devastating floods in eastern South Africa in April 2022, increasing the event's intensity by 4-8%.

A collaborative scientific analysis concludes that greenhouse gas and aerosol emissions contributed to the increased likelihood and intensity of heavy rainfall during Tropical Storm Ana and Tropical Cyclone Batsirai in early 2022. While Tropical Storm Ana was a rare event for Malawi and Mozambique (1 in 50 years), Cyclone Batsirai was more common for Madagascar (1 in 2 years). The study highlights that existing vulnerabilities, including prior flooding, conflict in northern Mozambique, and drought in southern Madagascar, exacerbated the humanitarian impacts.

The study finds that human-induced climate change did not significantly increase the occurrence of the poor rains observed in southern Madagascar between July 2019 and June 2021, as trends remain overwhelmed by natural variability. While the region experienced a 1-in-135 year dry event with only 60% of normal rainfall, the resulting severe food insecurity was driven primarily by high pre-existing vulnerability, poverty, COVID-19 restrictions, and pest infestations rather than climate change.

A rapid analysis of the June 2021 Pacific Northwest heatwave concludes that the event was virtually impossible without human-caused climate change. The study estimates the event as a 1-in-1000-year occurrence in the current climate, noting it was approximately 2°C hotter than it would have been before the industrial revolution. Projections indicate that with 2°C of global warming, such events could occur every 5 to 10 years.

The analysis finds that while human-caused climate change made the absolute temperatures of the April 2021 frost event less cold, it simultaneously triggered an earlier start to the growing season. This shift exposed young leaves to winter-like conditions, making the 2021 event 20% to 120% more likely. The study notes that in a 2°C warming scenario, such frost events are projected to intensify further by 0.2°C to 0.5°C.

The analysis finds that anthropogenic climate change has significantly increased the probability of extreme fire weather and heatwaves in southeastern Australia, while having no attributable trend in dry extremes. Specifically, the probability of a Fire Weather Index as high as in 2019/20 has increased by more than a factor of four since 1900. Heatwaves of similar intensity are now approximately 10 times more likely than they were around 1900. While climate change increased the overall risk, the specific severity of the 2019 event was further amplified by natural variability, specifically the Indian Ocean Dipole and the Southern Annular Mode.

The analysis finds that the July 2019 heat wave in Western Europe was made significantly more likely and more intense by human-induced climate change. In France and the Netherlands, the event would have been extremely unlikely without human influence, with return periods increasing by at least 10 times (and up to a hundred times). In the U.K. and Germany, the likelihood of such an event is estimated to be about 10 times higher (at least 3 times) due to climate change. Across all studied locations, temperatures would have been 1.5 to 3 ºC cooler in an unchanged climate.

The document details the rising trends of heat waves and heat stress in the US, attributing recent increases to human-caused climate change and projecting more severe events by 2100 unless emissions are stabilized.