What causes the threat to the Earth known as 'global warming'?

Answer 1

Global warming is being caused by burning of fossil fuels (coal, oil and natural gas) in industry, transport and the generation of electricity, which releases carbon dioxide (CO2).

A second cause is deforestation (cutting down trees which previously removed carbon dioxide (CO2) from the atmosphere).

A:No matter what names people choose to label other people - hoaxers, deniers, sceptics, whatever - regarding "global warming" (or nowadays "global climate change"!), major physical processes and events have been happening to the Earth throughout its long history and will keep on happening.

Some physical processes are continuous, taking place over a very long periods of time. Other physical processes take very little time by comparison: we humans have chosen to call some of those "catastrophic events" because they seem to have taken place with hardly any warning.

For the past 4,000 million years the outer crust of the Earth has been changing. Its tectonic plates, continually move around forming continents which then break up and re-form in other configurations. The friction caused by the sliding and subduction of the edges of plates against one another causes mountain chains to be thrown up and fiery volcanos to spew out new soil and smokey, noxious gases which pollute the atmosphere.

65 million years ago the dinosaurs were wiped out by a major event. It was probably a huge meteorite from outer space which suddenly hit the Earth. The resulting air pollution caused thousands of years of continuing global darkness and bitter cold because heat and light from our Sun could not reach the surface until the pollution was eventually absorbed by the Earth.

An ice sheet on Antarctica began to grow some 20 million years ago. The current ice age, the Pliocene-Quaternary glaciation, started about 2.58 million years ago during the late Pliocene when the spread of ice sheets in the Northern Hemisphere began. Since then, the world has seen cycles of glaciation with ice sheets advancing and retreating on 40,000- and 100,000-year time scales called glacials (glacial advance) and interglacials (glacial retreat).

The Earth is currently in an interglacial, and the last glacial period ended about 10,000 years ago. All that remains of the continental ice sheets are the Greenland ice sheet, the Antarctic ice sheet and smaller glaciers such as on Baffin Island. It is likely that people lived in the temperate zones of the Earth before that last glacial period began, along with other animals and plants. After the maximum had occured and the glaciers receded, modern humans were able to migrate from a belt of land around the Earth's Equator towards its poles.

All this says that the physical processes and systems which affect the Earth are much bigger - both in scale and in time - than anything which can be created by creatures who live on its surface or in its oceans. Is it credible that any of those creatures can really affect what happens to the Earth?

Answer 2

Global warming is primarily caused by the increase in greenhouse gases, such as carbon dioxide and methane, in the Earth's atmosphere. These gases trap heat from the sun, leading to a rise in global temperatures. Human activities, such as burning fossil fuels, deforestation, and industrial processes, are the main sources of these greenhouse gas emissions.