Climate change is changing the character of the West’s warmest periods; making them more frequent, more persistent and more lethal.
Throughout almost all of human history, heat waves have been driven by natural variability, or the tendency for weather patterns to occasionally deviate from their typical patterns. However, the accumulation of greenhouse gases from burning fossil fuels now increases the likelihood and severity of such extreme temperature events.
Although California and the American West will continue to experience cool days and periods of heavy snowfall, scientists say the long-term trend is for the planet to get warmer as fossil fuels continue to burn. Since 1880, the global average temperature has increased by about 2 degrees.
How does climate change affect the length and duration of heat waves? How will rising temperatures affect people and ecosystems? How much warmer is the weather expected to get if current emissions continue unabated?
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Here’s what the experts say:
How do we know the planet is warming?
Temperature measurements in the Earth’s atmosphere and oceans are monitored by thousands of weather stations, buoys and ships around the world. Scientists use this data to calculate the global average temperature.
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“We know the planet is warming because all of these groups are independently documenting a clear, long-term increase in our global average temperature,” said Kristina Dahl, chief climate scientist at the Union of Concerned Scientists, a national nonprofit organization.
“This is a trend that cannot be explained by any natural cause, such as volcanic eruptions or changes in solar radiation,” he said. “Emissions of carbon dioxide and methane, which are known potent heat-trapping gases, very clearly explain the trend we’re seeing.”
According to the National Oceanic and Atmospheric Administration, 19 of the 20 hottest years on record have occurred since 2000.
The year 2023 was the planet’s hottest year ever recorded. In July, Phoenix recorded temperatures of 110 degrees or higher for 31 consecutive days; this was the hottest month on record for any US city.
In 2021, an abnormal and extreme heat wave in the Pacific Northwest killed hundreds of people and an estimated 1 billion marine animals off the coast of British Columbia. A study of this phenomenon found that the likelihood of such heatwaves could be 20 times greater if current carbon emissions continue.
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How much warmer is the weather expected to get if current emissions continue unabated?
Scientists use a range of potential future emissions scenarios to try to discern how emissions choices will affect all aspects of our climate, Dahl said. Here’s an example of what these scenarios show:
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If emissions continue at current levels until 2050 and begin to fall thereafter, global temperatures will warm by about 5 degrees by the end of the century. This is what the Intergovernmental Panel on Climate Change considers a “middle-of-the-road scenario.”
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With current policies in place, we will face a similar amount of warming in the range of 4.3 to 5 degrees unless these policies are significantly strengthened. While California aims to reach carbon neutrality by 2045, the country generally aims for 2050. Other countries have longer goals, such as China, which aims for 2060.
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In a worst-case scenario where our heat-trapping emissions would triple by about 2075, the planet would experience warming of about 8 degrees. This is unlikely because it would mean higher emissions than the road we are on.
How does climate change affect the length and duration of heat waves?
The frequency of extreme heat events across much of the United States has been increasing since the mid-1960s, and the number of high temperature records has outstripped the number of low temperature records since the mid-1980s.
“While there is no single definition of what a ‘heat wave’ is, we know that cities in the United States and around the world have experienced more intense and longer-lasting heat waves over the past 60 years,” Dahl said. said. “Looking globally, the number of days with heat waves has almost doubled since the 1980s. The duration of heat waves has also increased during this time.”
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What are the potential consequences of rising temperatures for people and ecosystems?
Extreme temperatures are one of the deadliest effects of climate change. Extreme heat kills more Americans each year than other climate-related hazards, including hurricanes, floods and wildfires, but it gets much less attention because it kills so quietly.
A 2021 Times investigation found that California chronically undercounts the death toll from extreme heat, disproportionately harming poor people, the elderly and others who are vulnerable.
High temperatures can affect the human body in many ways. Heat can cause dehydration, dizziness, and headaches and can worsen underlying health problems such as cardiovascular disease. Health trackers often show spikes in deaths due to heart problems during heatwaves and in the days immediately following them.
A severe heat wave killed 395 people in California in September 2022, according to state health officials.
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During Phoenix’s record heat in the summer of 2023, emergency rooms also saw an increase in the number of people suffering from pavement burns as concrete reached 170 degrees or higher in high temperatures. Many burn patients may have collapsed on the pavement due to dehydration, poisoning or other factors that prolonged their exposure and complicated their treatment, officials said.
People who work outdoors or who do not have air conditioning are at particular risk of heat-related illness and death during extreme heat events. California has set temperature standards for outdoor workers but has not yet done the same for indoor workers.
Aside from health risks, “more frequent, more severe extreme temperatures also shape the way we live and experience the world around us; from whether we can enjoy visiting a national park to whether it’s safe to walk a few blocks to an ice cream cone,” Dahl said.
This includes impacts on ecosystems.
For example, rising temperatures have enabled pests such as bark beetles to survive and expand their range over the winter; This destroyed much of the Western forests. Avery Hill, a postdoctoral researcher at the California Academy of Sciences, noted that for every 1.8 degrees of global warming, up to 40% more trees could die from insect infestations.
Warming temperatures also cause vegetation to dry out, which can contribute to larger, faster and more frequent wildfires.
What’s more, forests that fail to recover from severe fires can turn into completely different ecosystems, affecting not only the diversity of plants and animals in the region but also the broader food web, Dahl said.
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It was hot before. Isn’t the planet always changing?
Earth’s climate is always changing and will continue to change as a result of things like changes in the shape of our orbit around the sun, Dahl said. But the changes documented over the last 150 years are unprecedented.
He said there is now more carbon dioxide in our atmosphere than at any point in the last 2 million years. Sea levels have risen faster in the past century than in any previous century in the last 3,000 years. Glaciers and the critical freshwater they contain are retreating faster than at any time in more than 2,000 years.
“The source of these changes is clear: We are. We are changing our climate because of our thirst for fossil fuels and the energy they provide,” Dahl said.
From a geological perspective, it could be argued that these changes are natural because humans are part of the planet, or that we should do nothing to correct the changing climate.
“But the truth is that humans have never experienced this kind of change before, and if we want to alleviate the suffering of the people, plants and animals experiencing this change most acutely, we will have to wean ourselves,” Dahl said. “We will get rid of fossil fuels and it is not too late.”
This story was first published in the Los Angeles Times.