Atmospheric greenhouse gases (GHG's), such as carbon dioxide and methane, that come from the combustion of fossil fuels are changing the Earth's climate. The world is warming, and there are many different phenomena that force the Earth's climate to become hotter or colder. While some of these are anthropogenic and some are natural (see here for a discussion of the difference), carbon dioxide released from pursuing energy services is by far the largest contributor to the planet's current changes in climate.
There is no magic temperature that the Earth should be at, but the climate is changing rapidly and this causes problems for all living things, including people. Some of the troubling aspects of climate change include:
There are various signs indicating that climate change is already happening, and will continue to happen. In the Intergovernmental Panel on Climate Change's 2018 special report, it stated on average the Earth's temperature raises by 0.2°C every decade. From pre-industrial levels, the special report states the Earth's average temperature has already increased by approximately 1.0°C. This report, written by 86 leading scientists from 39 countries, outlines how irreversible and unprecedented damage will occur when the Earth's average temperature raises by 1.5°C from pre-industrial times. If you are interested in checking out the full report, click here
GHG's mix in the atmosphere and travel around the world. This means that it is a global issue which will effect everyone, regardless if they are the source that emitted the GHG's or not. In contrast, something like air pollution, is more localized.
Humans use energy to maintain a high energy society that provides a good quality of life. As a result, the amount of energy that people use continues to increase to meet this high energy demand (see the pages on the BRIC and N11 countries for great examples of this). Unfortunately, most of the world's primary energy comes from fossil fuels, which is why climate change is so hard to stop.
There are lots of fossil fuels left. In fact, one of the biggest problems the world is facing today is that fossil fuels aren't going to run out! This has resulted in a lack of urgent need to find renewable and sustainable energy sources to replace fossil fuels. We have enough to continue burning these fuels for many decades to come, however, it will continue to induce problematic global warming, and climate change in general.
Governments will need to intervene to slow down the effects of climate change, however, individuals also make choices on their daily energy consumption as well. In the future, how climate change will affect the globe will depend both on how much and at what rate fossil fuels are burnt.