"The suggestion that humans are responsible for at least a significant component of climate change comes from several lines of evidence. Theoretical considerations suggest that discharging carbon dioxide and methane into the atmosphere will cause atmospheric warming, as can be directly observed above all cities in the developed world where energy use involves burning fossil fuels. Measurements of carbon dioxide and methane preseved in ice cores from Antarctica and Kallaallit Nunaat (Greenland) indicate that the concentrations have been relatively stable over the past 10000 years. However, since 1800, the concentration of carbon dioxide in the ice and the atmosphere has increased by about 30% and the concentration of methane has doubled.
Proxy data, historical records, and numerical temperature and precipitation observations allow comparison between what has happened under the purely natural circumstances that undoubtedly existed prior to 1800 AD, and what has happened since then. The most striking difference is not in the type of climate changes, or the areas of occurrence, or the consequences to organisms: it is the speed at which the changes are occuring. Changes that required hundreds , thousands, or tens of thousands of years in the natural and geological records are now seen within the span of decades. The rates of climate change are increasing, along with increased human production of carbon dioxide and methane. The acceleration of the rate of change began in the early 1800s, just as human consumption of fossil fuels increased. Ongoing climate changes directly above cities are proportional to the amount of energy consumed by each, with differences evident due to city size, lifestyle, and economic wealth. Taken all together, the acceleration of climate change cannot be explained solely by natural causes: human activity is the only factor that has changed substantially in Earth's climate system since 1800."
- Geography 1050: Introduction to the Principles & Practice of Geography. Memorial University of Newfoundland Department of Geography. 2008-2009 version.
(My geography textbook from last semester)
I doubt it's a hoax.
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