Not only is Earth’s surface warming, but the troposphere — the lowest level of the atmosphere, where weather occurs — is heating up too, U.S. and British meteorologists reported on Monday.

In a review of four decades of data on troposphere temperatures, the scientists found that warming in this key atmospheric layer was occurring, just as many researchers expected it would as more greenhouse gases built up and trapped heat close to the Earth.

This study aims to put to rest a controversy that began 20 years ago, when a 1990 scientific report based on satellite observations raised questions about whether the troposphere was warming, even as Earth’s surface temperatures climbed.