Heat wave. flood. Catastrophe. This year's weather shows us that climate change has arrived and is deadly.
From punitive heat in North America to record-breaking flooding in Europe and Asia, this year's weather shows us what it's like to live in a world that's warmed by 2 degrees Fahrenheit (1.1 degrees Celsius) over the past century.
"Dangerous climate change is already here. Michael Weiner, an extreme weather researcher at lawrence Berkeley National Laboratory, said: "This is a harsh reality that we need to acknowledge.
Extreme weather is already claiming homes, businesses and lives. Canada's recent flooding may be the most expensive in the country's history, with an estimated $7.5 billion in damage. According to the latest estimates, the 18 weather disasters that hit the United States in 2021 will cost more than $100 billion in total.
In August, Weiner and other scientists at the Intergovernmental Panel on Climate Change published a report showing that they are now more confident than ever that climate change is affecting the world's worst weather events, including these five.
The Pacific Northwest and southwestern Canada — a region that feeds about 13 million people and is known for its rainy, mild weather — experienced deadly heat this summer. Major cities such as Portland, Seattle and Vancouver, where many residents lack air conditioning, have seen their highest temperatures in history, exceeding 100 degrees Fahrenheit (38 degrees Celsius).
Intense heat is caused by a weather phenomenon called a heat dome in which an area of high pressure acts like a pot lid, trapping the heat in a specific area.
Studies of heat waves have found that the intensity would be "nearly impossible" without the greenhouse gases that have warmed the planet that have been emitted into the atmosphere over the past 120 years. Hundreds of people have died in the area as a result of the heat wave. A study published this summer suggests that more than a third of all heat-related deaths worldwide can be attributed to climate change. And those who have already suffered the most — from low-income, poor health or old age — have been hurt the hardest by the heat.
Plants and animals are also struggling to cope with extreme heat. In the Pacific Northwest, millions of marine animals have died, as have many on land. Farmers see berries being burned on their vines.
In August, the United States declared a water shortage on the Colorado River — the first for the waterway. Lake Mead is one of the river's most important reservoirs, falling to historic lows. While the announcement sparked water cuts for farmers in Arizona and parts of Nevada, and about 40 million people depend at least partially on the river's water, future droughts could prompt broader water cuts.
Since 2000, a "mega-drought" has hung over the western region. While the region may experience drought without taking into account human impacts, scientists say climate change is making it worse than it has been for more than 1,000 years.
Drought creates dangerous feedback loops. As the air warms, it sucks more moisture out of rivers, lakes, plants, and even the soil, which in turn makes the ground hotter and drier.
While the drought in the western United States is historic, climate change could worsen droughts around the world, with arid regions in the history of Africa and the Middle East being hit the hardest.
This year, the Dixie fire in California was the second largest in the state's history. It burned 500,000 acres of land and about 400 homes, contributing to a series of busy fire seasons that plagued the West. North America is not alone. Turkey, Greece – perhaps most surprisingly – Russia in Siberia also erupted in large wildfires.
When extreme heat and drought occur at the same time, the moisture of the soil is destroyed, forming dry vegetation that requires only a small spark to ignite a deadly fire. As climate change worsens high temperatures and droughts, it creates the conditions for larger and more frequent fires. In some parts of the west, the fire season lasts for an entire year.
This year's wildfires not only immediately threatened homes and businesses, but also produced unhealthy air pollution and threatened endangered species, including California's famous yew tree.
Canada, the United States, Germany, China – extreme rainfall this year and the floods they caused have plagued the world. In each of these places, precipitation is historic.
In British Columbia, 20 towns set record rainfall; Nashville saw its fourth wettest day on record; Central Park received more rain in an hour than ever before; German towns were flooded in two days with more rain than in a normal month; and Zhengzhou, China, received more rain in a day than the average annual precipitation of a year.
More intense rainstorms are caused by rising temperatures; for every 1.8 degrees Fahrenheit (1 degree Celsius) increase in temperature, the atmosphere can hold 7 percent more moisture. With more water at your disposal, storms have the potential to pour enough rainwater to cause flooding.
Many of this year's floods have shown how population centers and transportation routes are designed for a climate that may not last long. For example, goods entering and leaving Asia stagnated in Vancouver's port, blocked by flooding. In major cities, underground train tunnels were flooded and streets were turned into rivers.
Extreme rainfall is a major way climate change worsens hurricanes. Hurricane Harvey, which hit Houston in 2017, is one of the most extreme examples of this. The storm poured 60 inches of rain in some areas of Texas.
But Hurricane Ada embodied another dangerous feature of hurricanes caused by climate change: rapid intensification. This occurs when the hurricane's wind speed increases by at least 35 mph in a 24-hour period. Ida far exceeded that rate, growing by about 60 mph in one day, from a Category 1 storm to a Category 4 with a top wind speed of 150 mph.
While Ida is moving relatively fast, scientists expect future hurricanes to move more slowly on land on average, pouring more rain in one place and causing extreme flooding. Hurricane Harvey did just that over Houston; in 2020, Hurricane Sully stalled over Alabama. The researchers expect strong, rainy, slow storms to cause more damage in the future; as sea levels continue to rise, the deadly storm surges from hurricanes will also worsen.
Scientists are still studying how climate change will affect winter weather, and they are increasingly convinced that Arctic warming is producing harsher winter storms.
A recently published study found a possible link between September's Texas freeze and climate change, suggesting that the barrier between arctic cold air and tropical warm air is becoming more unstable, and that polar swirls — air currents moving through the stratosphere — are becoming increasingly likely to bring intense winter storms.
As the world's weather becomes more volatile, the public may begin to see different views on climate change.
A recently updated national survey found that 70 percent of Americans surveyed believe climate change is affecting the weather. In the survey's 14-year history, beliefs in climate change are the highest ever. 76 percent of Americans surveyed believe it is happening, and 52 percent believe they are personally being affected by it.
Temperatures will continue to rise, so extreme weather is likely to continue to influence climate change, one of the survey's authors, Edward Maybach, a climate change communication expert at George-Mason University, said by email.
"The ironclad truth is that most American communities will almost certainly experience more and worse climate events in the coming decades."