5. To sum up history in one sentence, it would be "Life gets better — not for everyone all the time, but for most people most of the time. " And the reason is energy. Without access to energy, poor people are stuck in the dark and deny all of these benefits and opportunities that come with power. For thousands of years, people burned wood for fuel and their lives were hard. But when we started using coal in the 1800s, life started getting better a lot faster. Pretty soon we had lights, refrigerators, elevators, cars, planes, and all the other things that make up modern life. So if we really want to help the poor, we need to find a way to get them cheap and clean energy.
Millions of the poorest families work as farmers. Changes in climate often mean that their crops won't grow because of too little rain or too much rain. That's particularly unfair because they're the least responsible for emitting (排放) CO2, which is causing the problem in the first place.
Scientists say that to avoid these great long-term changes to the climate, the world must cut greenhouse gas emissions by up to 80 percent by 2050, and eliminate them completely by the end of the century. Many scientists agreed that wouldn't be enough. The problem is that CO2 lingers (残留) in the atmosphere for decades.
In 2015, the world emitted 36 billion tons of CO2 to produce energy. Someone may tell you they know how to remove 100 million tons of CO2 per year. That sounds like a lot, but if you do the math 100 million divided by 36 billion you'll see that they're talking about 0. 3 percent of the problem.
P × S × E × C =CO2
(P — world's population; S — services used by each person; E — energy to provide service, C — carbon dioxide produced by energy)
As you learned in math class, any number multiplied by zero will equal zero. So if we want to get to zero CO2, then we need to make at least one of the four factors zero. But the world's population(P) is currently 7 billion and expected to increase to 9 billion by 2050. In terms of services used by each person(S), there are a lot of things like food, living, transportation and so on, which means the need of much energy in providing them. Therefore, it is carbon dioxide produced by energy (C) that matters the most in cutting down CO2.