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The study finds that the extreme two-day rainfall during Tropical Storm Imelda in September 2019 was made more likely and more intense by anthropogenic climate change. Observational data suggests the probability of such an event has increased by a factor of 2.6 since 1900, while climate model synthesis indicates a probability increase of 1.5 to 3.1 times and an intensity increase of 9% to 21%. The report also notes that rapid urban expansion and loss of impervious cover in Southeast Texas have exacerbated flooding risks for approximately 6.6 million people in the impacted counties.

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 analysis concludes that human-induced climate change has made the June 2019 heatwave in France more likely and more intense. Observational data suggests that a heatwave of this intensity is occurring at least 10 times more frequently today than a century ago, with temperatures approximately 4C higher. While climate models qualitatively agree on the strong human influence, they show smaller trends and fewer severe heatwaves than observations, simulating a probability increase of between a factor of 2 and 20. The study emphasizes that early-season heatwaves in June have more severe health and organizational impacts than mid-summer events.

The World Weather Attribution (WWA) consortium investigated the possibility of analyzing the effect of climate change on Super Typhoon Mangkhut's rainfall but determined an analysis was not feasible. The decision was based on three primary constraints: the availability of only one high-resolution model for the region, poor quality of public observational data in the affected area (with 50% missing data in most stations), and a lack of manpower and stable funding. The document notes that while greenhouse gases are expected to increase the precipitation of the strongest storms globally, region-specific projections have low confidence. Additionally, the WWA stated that while sea level rise affects storm surges, such impacts are not currently part of their attribution assessments.

The World Weather Attribution (WWA) consortium states it is unable to conduct a formal analysis of climate change's effect on Hurricane Florence's rainfall due to observational challenges, a lack of high-resolution models, and insufficient funding and manpower. While acknowledging a separate study by Reed et al. and the general scientific consensus that global warming increases precipitation, the WWA notes that storm surges—affected by sea level rise—are also expected but are not part of their current attribution assessment.

The study assesses the 2018 heatwave in Northern Europe using observational data and climate models to determine the role of human-induced warming. It finds that the probability of such an event has increased across the region, with the most significant increases in probability estimated in Ireland, Denmark, and the Netherlands. While the heat was most extreme in the high Arctic (northern Finland), where it exceeded historical records, the risk ratio was more easily quantified in southern regions. The authors conclude that anthropogenic climate change made these heatwaves more likely, though the exact magnitude of the increase is harder to quantify in Scandinavia due to high natural variability.

In early July 2018, southwestern Japan experienced extreme rainfall, with some interior stations recording more than twice the usual amount for the wettest day of the year, leading to local return times exceeding 200 years. Observational data from 94 stations show a higher prevalence of positive trends in extreme rainfall probability than negative trends, suggesting a systematic influence beyond natural variability. While a single high-resolution model (EC-Earth T799) qualitatively reproduces these positive trends from 1850 to 2098, the authors state that a lack of sufficient climate models and manpower prevents a robust quantitative attribution statement. The analysis concludes that climate change likely increased the probability of such extreme rains, though the exact magnitude remains undetermined.

An international team of scientists used a multi-method attribution approach to determine that anthropogenic climate change increased the likelihood of the 2015-2017 Western Cape drought by a factor of 3.3. The drought, characterized by three consecutive years of below-average rainfall, led to a severe water crisis in Cape Town, nearly resulting in 'day zero'. The study finds that drought risk in this region scales linearly with warming, suggesting that further temperature increases will continue to raise the probability of such extreme events.

The study concludes that human-induced climate change had no significant influence on the occurrence of Storms Eleanor and Friederike. While observational data from the past 40 years show a decrease in near-surface wind speeds, climate models suggest a marginal increase in the probability of extreme hourly winds (0-20%) by the middle of the century due to greenhouse gases. The observed decline in storminess is attributed to factors other than climate change, such as increased surface roughness, aerosols, and decadal variability.

The analysis finds that heat and cold extremes are warming globally in line with average temperatures, with cold extremes in Siberia and Canada warming particularly fast. Extreme daily precipitation is generally increasing at a rate of approximately 7% per degree Celsius, though regional variations exist. While trends in tropical cyclone frequency are difficult to determine, their impacts have increased due to higher precipitation and sea level rise. Drought trends remain complex and highly dependent on the specific definition used.

The analysis finds that while the December 2017-January 2018 cold wave in the northeastern U.S. and southeastern Canada was not unprecedented in absolute terms, it is now a rare event due to global warming. Cold waves of this intensity have become approximately fifteen times less frequent over the last century, with temperatures of such events increasing by about 4ºF (2ºC). The study finds no evidence that Arctic warming has intensified these cold waves; instead, it suggests that Arctic air moving south is now less cold.

The summer of 2017 saw extreme heat across Southern Europe, including the 'Lucifer' heat wave in early August. World Weather Attribution analysis indicates that human-induced climate change significantly increased the likelihood of these events. A summer as hot as 2017 is now estimated to have a 1 in 10 annual chance in the Euro-Mediterranean region and is projected to become normal weather by the middle of the century under continued greenhouse gas emissions.

The analysis concludes that while Hurricane Harvey was an extremely rare event, global warming increased the intensity of its precipitation by approximately 15% and made such an event about three times more likely. Observational data and climate models indicate a trend of increasing extreme precipitation along the US Gulf Coast, often exceeding the standard Clausius-Clapeyron scaling. The study emphasizes that while the storm's rarity makes it difficult to attribute its existence to climate change, the increased rainfall intensity contributed significantly to the flooding in Houston, which was further exacerbated by urban development and subsidence.

The study concludes that anthropogenic climate change significantly increased the likelihood of the June 2017 heat event across Western Europe. Using observational data and multiple climate model ensembles, researchers found that such extreme heat is now more frequent, occurring every 10 to 30 years depending on the country. The risk ratio was highest in Portugal and Spain, where the probability of such heat increased by more than ten times due to global warming. The report also notes that under high-emission scenarios (RCP8.5), temperatures similar to June 2017 could become normal by the end of the century.

The analysis concludes that climate change had a small effect on the 2016 autumn drought in Somalia and Somaliland, with no significant trend in observed rainfall. However, a strong La Niña event significantly increased drought risks and explained approximately one third of the precipitation deficit. The severe food insecurity resulting from the drought was primarily driven by high human vulnerability caused by decades of conflict and political upheaval rather than meteorological factors alone.

The 2016 drought in Kenya was primarily driven by sea-surface temperature patterns, specifically La Niña, rather than human-induced climate change. While climate change did not significantly increase the likelihood of the rainfall deficit, it did lead to hotter temperatures that exacerbated the drought's impact. The event was less severe than the 2010-11 drought but still triggered a national emergency, affecting millions of people in arid and semi-arid lands.

The analysis finds that February 2017 was the second warmest February on record for the contiguous United States, with temperatures 3.1°C above the 1981–2010 normal. By combining historical observations with CMIP5, HadGEM3-A, and Weather@Home model ensembles, the study concludes that the probability of such a warm event has increased more than threefold due to human-induced greenhouse gas emissions. While the 2017 event had a return period of approximately 12 years in the current climate, it would have been a 1-in-160-year event around 1900. Projections suggest that by 2050, temperatures like those seen in February 2017 will be 'completely normal', occurring roughly every three years.

The analysis finds that climate change significantly increased the likelihood of the record-breaking summer heat in New South Wales and the three-day heatwave in Canberra, while the influence on Sydney's heatwave was less clear due to high variability.

The North Pole experienced unprecedented warmth in November and December 2016, with temperatures reaching 15 ºC above normal on November 11. Analysis using historical observations and climate models (CMIP5 and Weather@Home) indicates that such an event would have been extremely unlikely—with a probability of less than 0.1 percent per year—in a climate without human-induced greenhouse gas emissions and aerosols. The study highlights that Arctic amplification, driven by albedo-feedback and lapse-rate feedback, makes the region the fastest-warming on Earth. Under a high-emissions scenario (RCP8.5), such extreme heat events are projected to become commonplace by approximately 2047, corresponding to a global mean temperature increase of 2 to 3 ºC above pre-industrial levels.

The December 2016 cold air outbreak in the United States was found to be a common winter occurrence and not evidence that global warming is increasing the extremity of cold weather. Analysis of stations in Boulder, Colorado, and New Orleans, Louisiana, indicates that cold extremes are generally decreasing in intensity, particularly in New Orleans where the coldest day of the year is 3.2°F warmer than a century ago. The study concludes that while northerly wind patterns show no significant trend, the Arctic source regions for this cold air are warming rapidly, leading to a general decrease in the intensity of such outbreaks in both observations and climate models.