by Climate change is changing the character of the hottest periods in the West – making them more frequent, longer lasting and more deadly.
For most of human history, heat waves — or the tendency of weather patterns to occasionally deviate from their normal patterns — have been caused by natural variability. Now, however, the accumulation of greenhouse gases due to the burning of fossil fuels is increasing the likelihood and severity of these extreme heat events.
While California and the American West will continue to experience cool days and periods of heavy snowpack, scientists say the long-term trend is for the planet to grow warmer with the continued burning of fossil fuels. Since 1880, the average global temperature has increased by about 2 degrees.
How is climate change affecting the length and duration of heat waves? How will rising temperatures affect people and ecosystems? How much warmer is expected if current emissions continue unabated?
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Here’s what the experts have to say:
How do we know the planet is warming?
Temperature readings of the Earth’s atmosphere and its oceans are monitored by thousands of weather stations, buoys and ships around the world. Scientists use this data to calculate global average temperatures.
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“We know the planet is warming because all these groups are independently documenting a clear, long-term increase in our average global temperature,” said Kristina Dahl, chief climate scientist with the Union of Concerned Scientists, a national nonprofit organization.
“It is a trend that cannot be explained by any natural causes, such as changes in volcanic eruptions or solar radiation,” she said. “Human emissions of carbon dioxide and methane, two known powerful heat-trapping gases, explain the trend we’ve seen very clearly.”
Nineteen of the 20 warmest years on record have occurred since 2000, according to the National Oceanic and Atmospheric Administration.
The year 2023 was the hottest year on record on the planet so far. In July, Phoenix recorded 31 consecutive days of temperatures of 110 degrees or higher — the hottest month on record for any US city.
In 2021, an anomalous and extreme heat wave in the Pacific Northwest killed hundreds of people and an estimated 1 billion sea creatures off the coast of British Columbia. A study of that event found that such heat waves could become 20 times more likely if current carbon emissions continue.
Read more: The LA Times investigation into the deadly toll of extreme heat
How much warmer is it supposed to get if current emissions continue unabated?
Scientists use a range of possible future emissions scenarios to try to determine how emissions choices will affect all aspects of our climate, Dahl said. Here is an example of what those cases show:
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If emissions continue at current levels until about 2050, then begin to fall thereafter, global temperatures would warm by nearly 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 the policies currently in place, we would get the same amount of warming — in the range of 4.3 to 5 degrees — unless those policies are strengthened significantly. California aims to achieve carbon neutrality by 2045, and the nation as a whole aims for 2050. Other countries, such as China, aim for 2060 .
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In the worst-case scenario, where our heat-trapping emissions triple by about 2075, the planet would warm by about 8 degrees. This is unlikely to be the case, as it implies higher emissions than the path we are on.
How is climate change affecting the length and duration of heat waves?
For much of the US, the frequency of extreme heat events has increased since the mid-1960s, and the number of high-temperature records has exceeded the number of low-temperature records since the mid-1980s.
“While there is no single definition of what a ‘heat wave’ is, we do know that cities across the US and around the world have been experiencing more intense and longer heat waves over the past 60 years,” said Dahl. “If we look globally, the number of days with heat waves has almost doubled since the 1980s. During that time, heat waves have also increased.”
Read more: Climate change is increasing the frequency and temperature of extreme heat waves
What are the possible consequences of rising temperatures for people and ecosystems?
Extreme heat is one of the deadliest effects of climate change. Each year, extreme heat kills more Americans than any other climate-fueled hazard, including hurricanes, floods and wildfires, but it gets far less attention because it kills so quietly.
A 2021 Times investigation found that California has a low death toll from extreme heat, which disproportionately harms the poor, the elderly and other vulnerable people.
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 tend to show spikes in deaths related to heart problems during and in the days immediately following heat waves.
California’s blistering heat wave in September 2022 killed 395 people, according to state health officials.
Read more: Heat waves are much more deadly than we think. How California ignores this climate threat
During Phoenix’s record heat in the summer of 2023, the number of people suffering from sidewalk burns in emergency rooms also increased, as concrete can reach 170 degrees or hotter amid high air temperatures. Officials said many burn patients may have died on the trail from dehydration, intoxication or other factors that increased their exposure and complicated their treatment.
People who work outside or otherwise lack air conditioning are at risk of heat-related illness and death during an extreme heat event. California has established heat standards for outdoor workers, but has not yet done the same for indoor workers.
Beyond the health risks, “more frequent and more severe extreme heat is shaping the way we live and experience the world around us, from whether we can enjoy a visit to a national park to whether it’s safe to walk a few blocks to an ice cream cone,” said Dahl.
This includes effects on ecosystems.
For example, warming temperatures have enabled pests like bark beetles to survive the winter and expand their range, causing the decline of Western forests. Avery Hill, a postdoctoral researcher at the California Academy of Sciences, noted that for every 1.8 degrees of additional global warming, up to 40% more trees could die from beetle infestation.
Warming temperatures are also associated with drying out vegetation, which can contribute to larger, faster and more frequent wildfires.
In addition, forests that do not survive severe fires can completely transition into different ecosystems, which not only affects the range of plants and animals in the area, but can also affect on the larger food web, said Dahl.
Read more: It was just August – and Earth’s hottest summer – on record, prompting warnings
It has been hot before. Isn’t the planet constantly changing?
Earth’s climate has always changed and will continue to change as a result of things like changes in the shape of our orbit around the sun, Dahl said. However, the changes documented for 150 years or so are unprecedented.
There is more carbon dioxide in our atmosphere now than at any point in the last 2 million years, she said. Sea levels have risen more rapidly in the last century than in any previous age in the last 3,000 years. Glaciers — and the vital fresh water they contain — are retreating faster than at any time in more than 2,000 years.
“The source of these changes is very clear: It is ours. We are changing our climate because of our thirst for fossil fuels and the energy they provide,” said Dahl.
From a geological point of view, it could be argued that because humans are part of the planet, these changes are natural changes, or that we should not do anything to solve our changing climate.
“But the reality is that humans have never lived through this kind of change before,” said Dahl, “and if we want to alleviate the suffering of the people, plants and animals that are experiencing this change on the sharpest way, we will have to overtake ourselves. off fossil fuels, and sooner rather than later.”
This story originally appeared in the Los Angeles Times.
