From floods and hurricanes to wildfires and mudslides, climate change set the stage for numerous natural disasters across the U.S. in 2018. In the list below, we rank ten of the year’s most noteworthy events by their “climate buzz,” as measured by the volume of climate change-related discussion they generated on Twitter and in the news. We identify the trends and physical processes behind each event fueled by climate change.
For more details on these events, follow the links or visit Climate Signals, a digital platform that identifies the long-term climate change trends behind extreme events as they unfold in real time. The platform hosts a database of climate change impacts organized as trends (the “signals”) and individual events.
Scroll down and hover over each image to find out which event’s climate connections sparked the most conversation in the news and Twitterverse.
*For this exercise, we utilized social media analytics platform Crimson Hexagon’s buzz monitor tool, which scoured the web for specified types of content fitting ten different Boolean keyword searches.
1. HURRICANE FLORENCE
Hurricane Florence may have weakened to a Category 1 storm when it made landfall in North Carolina, but it shattered rainfall records as predicted in the first advanced forecast attribution statement about climate change influence on a tropical cyclone. The attribution study found rainfall would be significantly increased by more than 50% in the heaviest precipitating parts of the storm due to human-caused climate change. North Carolina received a record-breaking 35 inches of rain, and more than 20 inches in South Carolina. Overall, Florence dumped 11 trillion gallons of water.
The conditions for Florence parallelled the setup for Hurricane Harvey: unusually warm seas and a warmer atmosphere helped supercharge deluge and the storm stalled at the coast due to a high blocking pressure area. These conditions are consistent with the long-term trend of increasing stalling of tropical cyclones that has been observed worldwide and attributed to climate change.
Hurricane Florence September 2018
2. CALIFORNIA WILDFIRES
Four of California’s 20 largest wildfires have burned in the last year: the Thomas Fire, the Mendocino Complex Fire, the Carr Fire and the Camp Fire. Sixteen of the state’s largest wildfires have occurred since 2000.
Climate change is driving up the heat and increasing wildfire risk. Since 1970, temperatures in the American West have increased by about twice the global average, and western wildfire season has lengthened from five to seven months on average. For example, the Thomas Fire started burning in December and wasn’t contained until January. This paved the way for another top climate event of 2018: the Southern California mudslides.
From 1979 to 2015, climate change was responsible for more than half of the observed increases in dryness of western forests, as well as the increased length of fire season. Parched forests and longer fire seasons extended fire-prone land by 16,000 square miles—about the size of Massachusetts and Connecticut combined—putting more communities in harm’s way. Scientists continue to identify the fingerprint of climate change in wildfire activity in California.
Western Wildfire Season 2018
3. Hurricane Michael
For the third consecutive year, Florida was hit by a hurricane when Hurricane Michael made landfall as a high-end Category 4 hurricane. Michael is the first Category 4 storm to hit Florida on record, and 3rd strongest landfalling hurricane on record in the contiguous United States (measured by pressure).
Storm surge at Mexico Beach reached 15.55 feet, half a foot higher than the original 14 foot projections. Water levels reached up to 20.6 feet if you add waves to the storm surge. Global warming is driving up sea levels, which allows storms along low-lying areas to push more seawater further inland. Storm surge is often the most important impact of tropical cyclones in coastal regions. Storm surge accounted for 49 percent of storm-related fatalities between 1963 and 2012.
Hurricane Michael October 2018
4. HURRICANE LANE
Hurricane Lane was the second-wettest tropical cyclone on record in the U.S., coming in just behind Harvey with 52 inches of rainfall. The superstorm hit the islands with deluge 4 months after an earlier record was broken in April when 50 inches of rain was dumped on the islands within a 24-hour period.
Hurricanes making landfall in Hawaii are rare due to cooler water temperatures in that region, along with drier and more stable air, and an increase in wind shear (the change in wind speed and/or direction with height). However, on August 20th, sea surface temperatures along the path of Hurricane Lane were as much as 4.5°F above the average from 1961 to 1990, which fueled the hurricane to Cat 5 strength. Lane comes on the heels of Hurricane Hector, which nearly reached Category 5 strength in its run by Hawaii earlier in August.
Hurricane Lane August 2018
5. SOUTHERN CALIFORNIA MUDSLIDES
Record heat and drought, followed by record fire, set the stage for flash floods and mudslides—all signals of climate change. The area where the January mudslides occurred had just been ravaged by the Thomas Fire, which was the largest wildfire in California history until the Mendocino Complex Fire 8 months later. The Thomas fire began in December and was still burning in Santa Barbara County when the rainfall began.
The short, heavy rainfall that caused the mudslides was consistent with observed trend of increasingly heavy downpours, a trend driven by climate change. armer air can hold more water–and therefore dump–more rainfall.Intense bursts of rainfall are more likely to cause flooding. Climate change has also contributed to California’s longer fire seasons, the growing number and destructiveness of fires and the increasing area of land consumed, and experts say a landscape charred by fire is more susceptible to mudslides.
Southern California Mudslides January 2018
6. TYPHOON YUTU
Super Typhoon Yutu was the strongest U.S. tropical cyclone in 2018, passing over the North Mariana Islands as a Category 5 storm. The eye of the superstorm sustained a maximum a wind speed of 180 mph. Yutu devastated the islands of Tinian and Saipan, marking it the second-strongest system to hit the United States and its unincorporated territories by wind speed, and third most intense by pressure.
Individual studies have found the fingerprint of climate change in hurricane activity in the Central Pacific region of Hawaii as well as in the Northwest Pacific, where Typhoon Yutu devastated the U.S. territories of Guam and the Northern Mariana Islands and inflicted heavy damage on the Philippines.
7. ELLICOTT CITY FLOODS
Ellicott City was hit with a second 1-in-1,000 year rainfall event since 2016. Ellicott City is particularly vulnerable due to the city being bordered by the Patapsco river and by areas of higher elevation, which means heavy rain could trigger flooding from two directions. Eight inches of rainfall within a two-hour period triggered flash flooding.
Climate change contributes to extreme rainfall and flooding. Climate change loads storms with more rainfall, increasing the threat of flooding. A warmer atmosphere holds and dumps more moisture. In the northeastern region of the US that includes Maryland, extreme precipitation has increased 55 percent from 1958 to 2016.
An October 2015 study shows that extreme rainfall events in Maryland are increasing communities’ risk of Salmonella poisoning. The study by Jiang et al finds a 5.6 percent increase in salmonellosis risk associated with increases in the heaviest 10 percent of storms, with the impact disproportionately felt in coastal areas. The study provides evidence that heightened risk of extreme rainfall and flooding due to climate change has a direct impact on the overall burden of infectious diseases such as salmonellosis.
Ellicott City Floods May 2018
8. BOMB CYCLONE
A combined arctic outbreak and the intensified nor’easter, called a bomb cyclone, kicked off a season of four intense snow storms slamming the Northeast and driving record-breaking flooding. The combined impact of the arctic outbreak and the intensified nor’easter made for a double whammy that broke record-cold temps from West Virginia to Maine. Climate change contributed to the conditions of the megastorm in two major ways: a rapidly-warming Arctic pushed arctic air south and an unusually warm Atlantic fueling the storm.
The unusually warm offshore waters amplified the temperature contrast between land and ocean surfaces. This temperature contrast is what generally fuels nor’easters. These conditions over the Atlantic are consistent with the long-term climate change trends that intensify nor’easters, researchers report.
Ahead of the third extreme winter storm, a March study confirmed human-induced climate change increase the frequency of extreme winter storms. The study found Arctic amplification is playing a role in the occurrence of the storms because because severe winters in the eastern US tend to occur when the Arctic is unusually warm. The Arctic is warming two to three times as fast as the rest of the globe due to unique feedbacks in the Arctic climate system—a phenomenon known as Arctic amplification.
9. EXTREME JET STREAM & TX HEAT WAVE
An extreme jet stream wreaked havoc in the Northern Hemisphere, from wildfires in the Arctic to deadly heat waves in Texas, Japan and Africa, to flooding rain along the U.S. east coast. An August study confirmed the fingerprint of climate change in how a warming Arctic continues to fuel weather extremes.
A warming Arctic slowed the circulation of the jet stream, which means high and low pressure fronts are getting stuck, or stalling, making weather less able to moderate itself. The engine driving many extreme weather events often is a major change in global atmospheric circulation. This amplifies heat waves, drought conditions (which help fuel wildfires in combination with higher temps), and extreme precipitation and flooding.
10. OKLAHOMA RHEA FIRE
The Rhea Fire is the third major fire in three years to tear through hundreds of thousands of acres in the Oklahoma Plains. Unusually hot temperatures amplified drought conditions fueled the fire. The average temperature in Oklahoma during March was 3.6°F above the 20th century average.
Back-to-back-to-back annual extreme events are a classic signal of climate change. Each of the three big fires featured similar conditions: unusually wet summers and falls, followed by unusually hot and dry winters. This creates unusually lush landscape that can transform into highly flammable wildfire fuel under dry and hot winter conditions.
Since the 1970s, large grass and shrubland fires have increased by more than 100,000 acres per decade. The frequency and intensity of wildfires in the Great Plains are increasing as the combination of higher temperatures, untamed underbrush and more extreme drought elevate wildfire risk.
Rhea Fire 2018