Coal is forever-ingrained in the minds of many as having a negative connotation – after all, there’s the saying that the naughty little boys and girls get coal in their stockings on Christmas. However, the negative connotation of coal expands far beyond just being a punishment for those on Santa’s naughty list – though it is a natural resource it, when being used as a source of energy, has detrimental side effects.

“Coal is by far the dirtiest energy source in terms of both greenhouse gas emissions and fatal particulate emissions,” according to Puskher Kharecha, the deputy director of the Climate Science, Awareness and Solutions program at Columbia University, “In the U.S., coal plants are responsible for the large majority of both of these emission types.”

A recent study carried out by the United Nations October 7 found that “many effects [of global warming] once expected only several decades in the future will arrive by 2040,” according to the New York Times. Coal, despite how harmful it is to the environment, is still being used as a major source of energy worldwide. And if this current trend of coal usage remains the same as it has for the past years, there may be a mass extinction of coral reefs, more food shortages, and an increased frequency of wildfires as early as 2040.

President Trump is notorious for his view of climate change and coal. Observations of his speeches and Tweets from 2012 until the present day have found that whenever he mentions coal, he refers to it as “clean” energy. He’s also consistently said that global warming is a “hoax.” Trump is under the impression that coal can be a “cleaner” energy source after it is washed following extraction; in reality, the process of “cleaning” coal, known formally as carbon sequestration, “involves capturing the greenhouse gases generated by burning coal and storing them underground, to keep the burning of coal from accelerating climate change,” according to the Los Angeles Times. This might be a solution to the coal problem though it’s very costly and it’s highly likely that Trump was not referring to this process.

According to the New York Times’ report on the United Nations study, “in order to combat the problems caused by coal, greenhouse pollution must be reduced by 45 percent from 2010 levels by 2030, and 100 percent by 2050.”

It also found that, by 2050, use of coal as an electricity source would have to drop from nearly 40 percent today to between 1 and 7 percent. Renewable energy such as wind and solar, which make up about 20 percent of the electricity mix today, would have to increase to as much as 67 percent.” However, doing this would be very costly; the cost wouldn’t outweigh the damage done by the rise in 2.7 degrees that is projected to happen by 2040, though. Such damage would cost the world $54 trillion.