The study, published in the journal PLOS ONE, also found that climate change has been consistently pushed further towards the back of textbooks over the last five decades.

The authors of the study argued that understanding climate change should be a priority for the US, as Americans are among the top carbon emitters per capita.

"Climate change is the most important issue that human society is facing," said study co-author Jennifer Landin, a science education researcher at North Carolina State University.

"Covering it in a few pages and relegating it to the end of the textbooks implies that it's not important," she told AFP.

The researchers analysed 57 university-level biology textbooks published between 1970 and 2019.

They found that the number of sentences about climate change increased from a median of less than 10 before 1990 to 30 in the 1990s.

That number jumped to 52 sentences in the 2000s -- which the researchers attribute to a boost in climate research during this time -- but fell back to 45 sentences in the 2010s.

The research also showed that sections addressing climate change are being increasingly pushed to the end of textbooks, moving from the last 15 percent in the 1970s to the last 2.5 percent in the 2010s.

Coverage of climate change solutions meanwhile fell from 15 percent of the passages dedicated to climate in the 1990s to just three percent in recent decades.

"I was surprised at how few personal, behavioural actions were included, and the ones that were included were not that important in terms of reducing carbon emissions," Landin said.

The researchers called for textbook publishers to increase their climate coverage, push it higher up in their books, pair climate impacts with solutions and include more environmental researchers as authors.

"Most educators are amazing, passionate and informed, but sometimes we do things because that's how it's always been done," Landin said.

"I have a feeling that once educators see this and recognise that it is a problem, they will probably reflect on their own approach to teaching. I know I have."