The Western half of the United States is entering a historic heat wave that will subject millions of Americans to sweltering conditions and is forecast to break records across California, Arizona, and neighboring states. Already on Monday, 39 million people were under heat alerts, and the heat wave will continue expanding and intensifying as the week progresses, pushing temperatures 20–30 degrees above normal across the region.This heat wave will have massive costs. Big Oil companies should be required to help pay for these costs, given that this is exactly the kind of climate disaster these corporations predicted their products would cause.This heat wave will impose massive costs.This heat event will likely inflict massive costs on the region’s public health, economy, and water availability.Extreme heat is the most lethal weather-related killer, and a heat wave in March is particularly dangerous, since people are not yet accustomed to such high temperatures. As the National Weather Service warned, this event will be “very dangerous, particularly for those not acclimated to the heat and/or traveling from cooler climates.” The 2021 Pacific Northwest Heat Wave directly caused well over 1,000 deaths. This event, which features a heat dome similar to the one that drove the 2021 disaster, will likely not have as high of a death toll, but mortality could still be considerable. Extreme heat also has profound economic effects. Heat waves have cost the world trillions of dollars in recent decades, and $162 billion in losses in the U.S. in 2024, equivalent to nearly 1% of GDP. This month’s heat wave will undoubtedly drain billions of dollars from the affected families, businesses, cities, and states.Also alarming is the effect this event will have on water availability and fire risk across the region in the coming months. After the warmest winter on record, the Western U.S. has already been experiencing one of the worst snow droughts in decades. This heat wave is forecast to melt the region’s already disastrously low snowpack at least a month ahead of schedule, resulting in a summer of serious drought and dangerous wildfire conditions during the upcoming dry season.This heat wave is a climate disaster.Though we’ll have to wait for a weather attribution study to confirm the exact causal connection between this heat wave and human-caused climate change, it is clear that global warming is a key driver of this disaster. As the National Weather Service stated, “Many locations are likely to set both all-time high temperatures for the month of March and their earliest 100-degree temperature on record.” This intensity is at least comparable to—and possibly more extreme than—prior heat waves that studies have shown were caused by climate change. For example, multiple extreme event attribution studies determined that the 2021 Pacific Northwest Heat Wave would have been “virtually impossible” without human-caused climate change. A metastudy of these kinds of analyses found that climate change made that event between 340 times more likely and infinitely more likely, and that “the probability of the 2021 heat wave’s intensity in a preindustrial climate was essentially zero.” Scientists have drawn similar conclusions about the heat wave that baked the Southwestern U.S. in July 2023. This month’s heat wave is similarly outside the parameters of historical precedent.As Daniel Swain, a climate scientist at the University of California Agriculture and Natural Resources, put it: “We know that in a warming world we see both more frequent and more extreme heat events. In particular, that’s the most slam-dunk type of event when it comes to thinking about extremes and climate change. And this is going to be exactly that type of event. It will be, in a climatological and statistical sense, record-shattering. I’m using that language intentionally because we’re not just breaking records—we’re breaking long-standing records by enormous margins. Essentially to a point where it would be almost impossible to have heat waves of this kind of magnitude if it weren’t for the warming that’s already occurred.”Big Oil predicted heat waves like this one and chose to cause them anyway, while lying about climate science.A relatively small number of major fossil fuel companies are responsible for the majority of all greenhouse gas emissions generated by humanity. Just 100 companies are responsible for 71% of all global greenhouse gas emissions generated since 1854, and just 57 companies are responsible for 80% of the emissions generated since 2016. Climate attribution science can increasingly quantify the impact of specific companies’ emissions on specific heat waves.