clasa axa b
whats known for certain
scientists know for certain that human activities are changing the composition of earths atmosphere. increasing levels of greenhouse gases, like carbon dioxide co2 , in the atmosphere since pre-industrial times have been well documented. there is no doubt this atmospheric buildup of carbon dioxide and other greenhouse gases is largely the result of human activities.
its well accepted by scientists that greenhouse gases trap heat in the earths atmosphere and tend to warm the planet. by increasing the levels of greenhouse gases in the atmosphere, human activities are strengthening earths natural greenhouse effect. the key greenhouse gases emitted by human activities remain in the atmosphere for periods ranging from decades to centuries.
a warming trend of about 1f has been recorded since the late 19th century. warming has occurred in both the nor...
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