Which of the following is true regarding the greenhouse effect? increased levels of human-produced carbon dioxide have enhanced the greenhouse effect the greenhouse effect did not exist before humans "greenhouse gases work by magnifying incoming solar radiation onto earth's surface, just like in a greenhouse" volcanoes are the largest source of greenhouse gases all of the above are true regarding the greenhouse effect

- increased levels of human-produced carbon dioxide have enhanced the greenhouse effect

- volcanoes are the largest source of greenhouse gases

Explanation:

The greenhouse effect is cause by the presence of greenhouse gases in the atmosphere, such as the carbon dioxide and methane. These gases have the ability to trap the heat into the Earth's atmosphere in much greater percentage, resulting in warming up of the atmosphere, thus the global climate as well. The biggest source of these gases are the volcanoes, being responsible for pretty much all of the greenhouse gases in the atmosphere for most of the geological history of the Earth. Despite still being number one, the volcanoes get assisted by the human activity in the past two centuries when it comes to greenhouse emissions into the atmosphere. By using the fossil fuels to produce energy, which means burning them, the humans have constantly been increasing their contribution in the amount of greenhouse gases released into the atmosphere. If that trend continues with this tempo, we might experience more dramatic climate change in the near future which can have been consequences.