Scientists have long been very confident that the accelerating long-term increase of Earth’s average temperature is also causing spikes in regional daily and weekly high temperatures. For example, if it’s 95 degrees outside and you turn on the heater in your house, it will get much hotter than normal. Just in the last five years, research has shown that human-caused warming greatly increased the likelihood of many recent deadly heat waves, including in late June 2021 in the Pacific Northwest, in Siberia in 2020 and across much of Europe in 2003.
Scientists have also documented a big increase in marine heat waves, which have killed fish, birds, marine mammals, starfish and crabs along the West Coast, shifted fishing grounds in the waters off New England and promoted the growth of potentially toxic algae like red tide in Florida. Research shows how global warming causes such ocean heat waves, which can also fuel extra-strong tropical storms and up the wildfire danger in California.
Global warming can also intensify heat waves by sucking the moisture out of the ground in the spring, and scientists also have shown that ocean heat waves and heat waves over land are linked. Extreme heat that spills from land over the sea damages coastal ecosystems, and that heat waves and droughts that start over the ocean and then move over land are often the most intense of all.