There isn't a definitive number of years that it would take for the environment to return to "normal" if all usage of fossil fuels stopped immediately. There are too many variables at work to give a specific number of years. What is definite is that it would take a long...
There isn't a definitive number of years that it would take for the environment to return to "normal" if all usage of fossil fuels stopped immediately. There are too many variables at work to give a specific number of years. What is definite is that it would take a long time for the environment to return to pre-Industrial Revolution levels.
The reason is that even if we completely stopped fossil fuel usage, the carbon emissions that have already been released stay in the atmosphere, oceans, plants, and animals for thousands of years. It would take many millennia for that carbon to make its way back into Earth's rocks, minerals, etc.
But what about rising temperatures? Would the temperature stabilize if all fossil fuel emissions ceased? The short answer is no. Scientists believe that there is a 40 year delay between current carbon emissions and the related temperature increase. This delay is called "climate lag." The lag is present because of Earth's oceans. It takes a lot longer to warm Earth's oceans than it does to warm Earth's atmosphere. The air warms up, which warms the oceans (but at a slower rate). As the oceans heat, they add to the overall rise in global temperatures. Think about a pot of water on the stove. If you turn the flame on high, the flame is hot immediately. The pot also gets hot very quickly because it has a high thermal conductivity; however, the water takes much longer to register those temperature changes. Even if you turned off the heat, the water will still continue to heat because the pot is still radiating heat into it. Earth's oceans do the same thing with climate change. If we stopped all fossil fuel usage tomorrow, the oceans are still warming due to the last 40 or so years of burning those fossil fuels.
To further complicate the matter is the fact that ecosystems and organisms within those areas adapt. They have been adapting, and they will continue to adapt to a changing environment. In all likelihood, stopping the usage of fossil fuels won't cause ecosystems to revert back to what they were like 200 years ago. They will have adapted to the recent changes, and they will find ways to work best within that current model.