Climate change spans the impact on physical environment, ecosystems and human societies due to ongoing human caused climate change. The future impact of climate change depends on how much nations reduce greenhouse gas emissions and adapt to climate change. Effects that scientists predicted in the past loss of sea ice, accelerated sea level rise and longer, more intense heat waves are now occurring. The changes in climate are not expected to be uniform across the Earth. In particular, land areas change more quickly than oceans, and northern high latitudes change more quickly than the tropics. There are three major ways in which global warming will make changes to regional climate: melting ice, changing the hydrological cycle (of evaporation and precipitation) and changing currents in the oceans.