The effects of global warming :There is a scientific consensus that climate change is occurring, and that human health are the primary driver. Evidence of climate change includes the instrumental temperature record, rising sea levels, and decreased snow cover in the Northern Hemisphere.Greenhouse gases greatly affect the temperature of the Earth; without them, Earth's surface would average about 33 C° (59 F°) colder than the present average of 14 °C (57 °F)