Solar energy radiation
Without sun energy, earth would be a very cold place, about -243C almost the same as average universe temperature -270C. Since the solar emits just enough energy to earth, or about 1368 W/m2 (also known as solar constant), which is then absorbed by the surface of the earth about 168W/m2, and the cloud about 67W/m2, the earth surface will maintain its warm temperature about 15C to make the life on earth possible.
But, what about the other side of the earth which is not directly get the solar radiation?, or we can say “night” part of the earth. Theoretically, the temperature will be -18C, the water will be freezing, and it is not an ideal place to life.
Greenhouse gases
Fortunately, our earth is covered with a blanket of gases known as greenhouse gases. These gases absorb 90% of the radiation emitted by the earth’s surface, let’s say about 390W/m2 at 15C, hence about 350 W/m2 absorbed. This keeps the earth’s surface temperature warm even at night.
The effect of warming underneath the ground from the trapped heat reflected back is analogous to the effect that occurs in the greenhouse for gardening. So, we call it the greenhouse gases.
The composition of natural greenhouse gases is O2 (55%), CO2 (39%), CH4 (2%), N2O (2%), O3 (2%), and halocarbons.
Global Warming
The right amount of greenhouse gasses in the atmosphere makes the temperature of the earth just right. But, if the gases increase, the surface temperature of the earth will increase. Maybe on average, it is just 1-2C, but this slight change in temperature could affect dramatically for human life. The ice in the pole can melt, then raise the sea water level, which can cause a flood in some countries.
Natural events such as Mountain eruptions could cause this change. However, this increase is mostly due to human activities, and the emission is also called anthropogenic greenhouse gases.
These are the following anthropogenic gas emissions due to the activities of energy (84%), agriculture (8%), industrial processes (5.5%), and waste (2.5%). the data was measured in 2003. The proportions of CO2 (74.4%), CH4 (16.7%), NO2 (6.4%), and Other (2.2%) were measured in 2010.
Water vapor actually makes a huge contribution to the greenhouse gas proportion (55%), but the cycle is very fast, following the water cycle. The bad news is that some gases, such as CO2, will remain in the atmosphere for more than a century. Unfortunately, our source of energy is fossil fuel, which emits mostly CO2 gas.
This is why most countries are pursuing a new “clean” source of energy or making some transition in their energy consumption. This has also become a major issue of concern because of the almost irreversible effects caused by it.
source: Christian Ngo, Joseph B. Natowitz. Our energy future: resources, alternatives, and the environment. Second edition. John Wiley & soons, inc. 2016