These concerns will linger both in the short and long term. In the long term, heat waves are becoming hotter and happening more frequently than in the past because of the added heat trapped by greenhouse gases in the atmosphere as a result of humans burning fossil fuels. An analysis by the nonprofit Climate Central found that human-caused climate change made this extreme heat event at least three times more likely for nearly 160 million people, almost half of the U.S. population. {read}