Yes. Sunscreen reduces the incidence of skin melanomas. And skin melanomas kill.
Taking those two claims separately:
- Does sun-screen reduce melanomas?
ABC News reported in December 2010 on some randomly-controlled research, with 1600 people participating, and published in the Journal of Clinical Oncology.
"It provides the first scientific data that shows that sunscreen can be beneficial for melanoma prevention," [...]
They randomly assigned participants to either receive standard advice on how to use SPF15+ sunblock, or to were given sunblock along with careful instructions and supervision.
After 15 years, there were twice the number of melanomas in the group members who applied sunblock 'now and then', compared to the daily use group.
Original Study: Reduced Melanoma After Regular Sunscreen Use: Randomized Trial Follow-Up, Adèle C. Green, Gail M. Williams, Valerie Logan and Geoffrey M. Strutton, JCO January 20, 2011 vol. 29 no. 3 257-263, doi: 10.1200/JCO.2010.28.7078]
NationMaster.com have mortality statistics for malignant melanomas. The incidence depends on the country, but with 7,420 reported deaths in the USA, it is quite serious (per year? it isn't 100% clear, but that's my assumption.)
It is difficult to compare countries due to different reporting systems, but Australia has only 7% of the population of the USA, but 14% of the malignant melanoma deaths (and a health care system that is at least comparable), suggesting that some countries have a more serious problem with melanoma deaths than others.
A critical review of the existing evidence for sun-screens has been published.
According to it:
Routine use of sunscreen has been shown to be effective at reducing the development of both [Squamous cell carcinoma] SCC and actinic keratoses, which are known precursors to SCC. However, a statistically significant protective benefit of sunscreen has not been demonstrated against either [basal cell carcinoma] BCC or malignant melanoma.