This is a difficult question. The atmosphere of Earth has been changing for as long as the Earth has existed, but these changes for the most part happen over immense time-scales. For instance, scientists believe that Earth’s atmosphere changed over from being heavy dominated by nitrogen to containing significant amounts of oxygen about 3.8 to 3.4 billion years ago. The dinosaurs, however, came much later, dying out about 65 million years ago. How much has the atmosphere changed since then? It’s difficult to tell, and also difficult to define because you have to establish a baseline for what constitutes “change.” Something happened all over the Earth about the time of the K-T Event (the asteroid impact that is theorized to have killed the dinosaurs) and atmospheric changes may have played some role in the evolution of the mammalian species, such as humans, that now dominate the land masses of the Earth. Humans have changed the atmosphere in an extremely short period of time through the greenhouse gases that cause global warming. This may be the most alarming change of all because it’s so sudden; the K-T event happened millions of years ago, and global warming has only been going on since the dawn of the Industrial Revolution in very recent history.
Click here to cancel reply.
Sorry,At this time user registration is disabled. We will open registration soon!
Don't have an account? Click Here to Signup
© Copyright GreenAnswers.com LLC