How will the Earth system change in the 21st century?

As the world consumes ever more fossil fuel energy, greenhouse gas concentrations will continue to rise and Earth's average temperature will rise with them. The Intergovernmental Panel on Climate Change (or IPCC) estimates that Earth's average surface temperature could rise between 2°C and 6°C by the end of the 21st century.

For most places, global warming will result in more hot days and fewer cool days, with the greatest warming happening over land. Longer, more intense heat waves will happen more often. High latitudes and generally wet places will tend to receive more rainfall, while tropical regions and generally dry places will probably receive less rain. Increases in rainfall will come in the form of bigger, wetter storms, rather than in the form of more rainy days. In between those larger storms will be longer periods of light or no rain, so the frequency and severity of drought will increase. Hurricanes will likely increase in intensity due to warmer ocean surface temperatures. So one of the most obvious impacts of global warming will be changes in both average and extreme temperature and precipitation events.

Scientists are also monitoring the great ice sheets on Greenland and West Antarctica, both of which are experiencing increasing melting trends as surface temperatures are rising faster in those parts of the world than anywhere else. Each of those ice sheets contains enough water to raise sea level by 5 meters and if our world continues to warm at the rate it is today then it is a question of when, not if, those ice sheets will collapse. Some scientists warn we could lose either, or both, of them as soon as the year 2100.

Ecosystems will shift as those plants and animals that adapt the quickest will move into new areas to compete with the currently established species. Those species that cannot adapt quickly enough will face extinction. Scientists note with increasing concern the 21st century could see one of the greatest periods of mass extinction of species in Earth's entire history. Ultimately, global warming will impact life on Earth in many ways. But the extent of the change is up to us.