If you live under the false premise that doomsday will never come, some basic laws of nature (concerning energy) may be appropriate for you to note. Roughly speaking, since I am no physicist and neither are most of you, Entropy is the tendency of a system to move from a higher state of potential energy to a lower state. It measures the "unavailability" of a system's energy to do work. Anything (energy-wise) that is useful must move to a higher state of Entropy, or it is useless to us.
My high school physics teacher used the example of an object placed on a desk. Potential energy was stored, because it was raised up in resistance to gravity. Gravity wants to return the object to the ground, and if the object is allowed to fall, the object's Entropy has increased. On the ground, it has a high level of Entropy, because the availability of the object's energy to do work no longer exists.
Conservation of Energy, not to be confused with blind draconian howls for energy conservation, is the idea that energy is not created nor is it destroyed. Instead, energy always flows from one system to the other.
The driving force in the Universe is that energy is always seeking the highest level of Entropy, or the state in which energy has the least potential to do work. If the Universe or closer to home, our planet ever were to reach that final highest level of Entropy, then that is the end. The Universe and the Earth will be dark, cold, and utterly dead.
When we consume fossil fuels, stored potential energy does work for us in useful ways. That work drives pistons in our engines. It also boils water to steam that spins turbines, which then drive electrical generators.
There are always consequences to "consuming" energy. When energy does work, things change and what existed before now exists in different forms. Remember, when we consume potential energy, that energy is moved to a higher state of Entropy. Things are always on the move… downhill.
Alternative energy sources are not without consequences either. Just apply some of this basic understanding of energy, and how it is that energy is useful to us, and you can begin to suspect that within the panacea, there may be dangers that are not apparent.
Solar energy panels are used to collect the sun's energy, converting it directly to electricity. That sounds terrific, but there are some things to consider. These panels are dark surfaces, which will capture the heat of the sunlight. Much of that light would have been reflected back into space, but now it has been converted to heat and will remain a part of our planet. Did you know that the photovoltaic panels are not sliced from silicon trees?