Who in 1990 was being surveyed about global warming? It really didn't become a mainstream issue until the IPCC's Third Assessment Report, which introduced the world to the infamous Hokey Stick.
In order to attract public interest environmentalists must make more shrill, more ridiculous statements as the following article from the Peruvian Times:
Climate change continues to wreck havoc in Peru's southern altiplano, where the arrival of freezing temperatures since March - almost three months earlier than usual - have killed more than a dozen people. The extreme cold has claimed the lives of 16 people so far in Puno, and 5,053 others are suffering from respiratory ailments, most of them children under 5, Elsa Paredes, of Puno's Regional Health Institute, told Enlace Nacional.No wonder the line on the graph above is mostly flat.