To get around that problem, researchers led by Luciana Gatti of the National Institute for Space Research in Sao Jose dos Campos in Brazil used aircraft to collect nearly 600 CO2 and carbon monoxide samples, from 2010 to 2018, at elevations up to 4.5 kilometres (2.8 miles) above the forest floor. Northwestern Amazon, they found, was in carbon balance, absorbing as much CO2 into the atmosphere as it gave off.