The ultimate source for all life’s energy, growth, and behavior is the Sun. ~ Lynn Margulis
Global climate is a confluence of entangled factors involving air, sea, and land. The oceans act as the primary planetary thermostat. They do so by conveying absorbed heat from the tropics toward the polar regions, as warm equatorial waters are carried to higher latitudes by prevailing winds.
Approaching the high latitudes, surface waters surrender their warmth. In losing heat, water becomes dense and descends to the depths, where it contributes to the cold-water currents flowing toward the equator.
The other aspect of oceanic thermal regulation is the removal and storage of carbon dioxide from the atmosphere: the carbon cycle. The atmosphere is naturally more a conduit and climatic expression than regulator. The exhausts of life on land greatly affect the atmosphere’s influence on climate.
Plants inhale atmospheric CO2 and respire O2. Further, greenery has a relatively low albedo. Thus, vegetation tends to keep the planet cool.
To the converse, the accumulative impact of humans has dramatically altered global climate, as industrially fueled atmospheric release of greenhouse gases and other pollutants tilts the planet toward hothouse. Humans are wrenching Earth’s thermostat into a severe mass extinction.