That is true. I say that because I'm already convinced there is a problem and Greta was speaking at an event that's been gathered by the UN because enough people believe there is a problem. The majority of that event actually focused on solutions.
Interestingly, I did a quick check on global climate change opinion and here's what I found. Plenty of people believe there is a problem, but still some pockets (including Australia) that aren't convinced.
Currently, 61% of people in Africa consider climate change to be a very serious problem.
74% of people in Latin America consider climate change to be a serious problem.
In Europe, there is a range from 88% to 97% of people feeling that climate change is happening and similar ranges are present for agreeing that climate change is caused by human activity and that the impacts of it will be bad.
In Asia and the Pacific, around 45% of people believe that climate change is a very serious problem.
In the Middle East, 38% of people believe that climate change is a very serious problem.
In North America, Mexico is the most concerned about climate change of the three countries in North America. 90% consider climate change to be a very serious problem. Canadians are also seriously concerned, 20% are extremely concerned, 30% are definitely concerned, 31% are somewhat concerned and only 19% are not very/not at all concerned about climate change. 61% of Americans say they are concerned about climate change, which that is 30% lower than Mexico and 20% lower than Canada.
https://en.wikipedia.org/wiki/Climate_change_opinion_by_country