evidence: Nearly all actively publishing climate scientists say humans are causing climate change.[4][5] Surveys of the scientific literature are another way to measure scientific consensus. A 2019 review of scientific papers found the consensus on the cause of climate change to be at 100%,[6] and a 2021 study concluded that over 99% of scientific papers agree on the human cause of climate change.[7] The small percentage of papers that disagreed with the consensus often contained errors or could not be replicated.[8] [...] In 2013, a study which found that out of over 4,000 peer-reviewed papers on climate science published since 1990, 97% agree, explicitly or implicitly, that global warming is happening and is human-caused.[37][38] Surveys of scientists' views on climate change – with a focus on human caused climate change – have been undertaken since the 1970s.[20][21] A 2016 reanalysis confirmed that "the finding of 97% consensus [that humans are causing recent global warming] in published climate research is robust and consistent with other surveys of climate scientists and peer-reviewed studies."[39] A 2019 study found scientific consensus to be at 100%,[6] and a 2021 study found that consensus exceeded 99%.[7]