The effect was largely caused by human activities that caused large concentrations of greenhouse gasses in the atmosphere, along with the removal of large swaths of forests on Earth which absorbed such gases and produced oxygen. (Historical accounts)
By the mid 21st century many low lying coastal areas on Earth were flooded due to the rising sea levels brought on by the global warming. The nuclear winter that followed the Third World War temporarily halted the warming process. In the years following first contact with the Vulcans in 2063, humanity was finally able to stabilize the planetary climate with technology and expertise provided by the Vulcans.
During one of their shared meditation sessions with Trip Tucker, T'Pol reflected on how one of Trip's favorite vacation spots - Sanibel Island - had nearly become a victim of global warming. (ENT - Rise of the Federation novel: A Choice of Futures)
In 2367 Lieutenant Commander Data constructed computer simulations that led him to conclude that Beta Moon of Peliar Zel II would experience global warming due to the Alpha Moon's use of Beta Moon's magnetic field as their primary energy source. (TNG episode: "The Host")