In 1896 the Swedish scientist Svante Arrhenius published a new idea that when humans burned fossil fuels such as coal, it would increase the average temperature of the planet, as it added carbon dioxide to the Earth atmosphere. This “greenhouse effect” was just one of many theories about climate change, but not the most logical. Scientists have found reasons to argue that these emissions could not change the climate, the main belief being that humanity, on such a small scale, could never have any effect on something as large as climate cycles. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay Past ice ages demonstrated that the climate could change dramatically across the entire planet, which seemed to be beyond anything humanity could bring about. In the 1930s, people realized that the United States and the North Atlantic region had warmed significantly during the previous half-century, which scientists thought was just one phase of a mild natural cycle. Only the amateur GS Callendar insisted that greenhouse warming was occurring. In the 1950s, Callendar's claims prompted some scientists to look into the topic, and new studies showed that carbon dioxide could actually accumulate in the atmosphere and should lead to warming. By 1960, evidence that gas levels were rising year by year began to open eyes to the issue. Others have found ways to recover past temperatures by studying ancient pollen and fossil shells. It seemed that climate change could occur, and had occurred in the past, within a few centuries. In the early 1970s, the rise of environmentalism fueled public doubts about the positive effects humans were having on the planet. Curiosity soon turned to concern. In addition to the greenhouse effect, some scientists have pointed out that human activity is putting dust particles and smog into the atmosphere, where they could block sunlight and decrease the planet's temperature, which was supported by an analysis of Northern Hemisphere weather statistics showing a cooling trend that began in the 1940s. After a few years, warnings of a new ice age were abandoned as only a few scientists supported this theory, and attention now turned to global warming. Evidence of huge temperature changes was shown when the Greenland ice sheet was drilled, and also of sudden changes. Greatly improved computer models began to suggest how such enormous temperature changes could occur, for example through a change in the circulation of ocean currents. Experts predicted droughts, storms, rising sea levels and other disasters due to global warming. An unexpected discovery was that the level of methane and some other gases was increasing, which would seriously contribute to global warming. Some of these gases have also degraded the atmosphere's protective ozone layer, and the news has inflamed public concerns about the fragility of the atmosphere. Furthermore, by the late 1970s, global temperatures had begun to rise again, and the public began to worry again when the summer of 1988 arrived, which was the hottest on record until then. Scientists did not fully understand the effect of pollution on the climate. and the processes involved, so it was difficult to persuade the..