4 LEARNING UNIT 1: INTRODUCTION TO THE IMPACT OF HUMAN ACTIVITY ON EARTH Climate changes have always been, throughout the history of the planet, but the climate warming we have been witnessing for about 150 years is anomalous because it is triggered by humans and their activities. It is called the anthropogenic greenhouse effect and is in addition to the natural greenhouse effect. With the industrial revolution, humans suddenly spilled millions of tons of carbon dioxide and other greenhouse gases into the atmosphere, bringing the amount of Co2 in the atmosphere to double the lows of the last 700,000 years. For about 15 years, data produced by thousands of scientists around the world, analysed and systematized by the intergovernmental panel on climate change (ipcc), have agreed that global warming stems directly from human activities. Officially, we are in the geologic epoch called the Holocene that began at the end of the last ice age, but the influence of human activity on the earth's ecosystems has become so extreme that it now seems to be the main cause of environmental change, leading some scientists to say that we should call the epoch in which we live the Anthropocene. According to the Dutch chemist and nobel Laureate Paul Crutzen (2000), is the age of man, that period when humans have an enormous impact on the entire Earth's ecosystem. As you can see, the greenhouse effect is the main cause of climate change. Certain gases in the Earth's atmosphere act somewhat like the glass in a greenhouse: these imprison the sun's heat, preventing it from returning to space and causing global warming. These gases for the most part is already present in nature but our activities cause their concentrations in the atmosphere to increase. In particular: ü carbon dioxide (CO2) ü methane ü nitrogen oxide ü fluorinated gases. Carbon dioxide produced by human activities is the main factor in global warming. In 2020 the concentration in the atmosphere exceeded the preindustrial level (before 1750) by 48 percent. The other greenhouseinducing gases are methane, which, however, is a gas with a more powerful greenhouse effect than CO2 but has a shorter atmospheric lifetime. Nitrous oxide, on the other hand, like CO2, is a long-lived greenhouse gas that accumulates in the atmosphere for decades and even centuries. Pollutants other than greenhouse gases, including aerosols such as soot, have different warming and cooling effects and are also associated with other problems such as poor air quality. Suffice it to say that natural causes, such as changes in solar radiation or volcanic activity, contributed only 0.1ºC to the total warming between 1890 and 2010. Source: https://theroundup.org/co2-greenhouse-gas-emission-statistics/
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