Reduce Fossil Fuel use by 20%. This is becoming a very serious problem. It is increasing the Earth's atmosphere temperature by a lot. Earth's land and ocean surface temperatures warmed up about 1.53 F from 1880 to 2012. If this continues then the oceans will heat up and Kill a lot of species. It can also cause a lot of droughts. There are many more ways the Earth heating up can cause problems.
Source
https://www2.ucar.edu/climate/faq/how-much-has-global-temperature-risen-...