Global warming refers specifically to observations that the overall average surface temperature of the world seems to be rising. Scientists are aware that temperatures around the world naturally vary widely, but after taking readings at specific locations over a long period of time, it can be seen that more places are warming up than are cooling down. Between 1901 and 2012, it is believed that the earths average surface temperature has risen by 0.89°C.
The vast majority of contemporary scientists have come to the agreement that the Earth's climate is observably getting warmer, and that it is 95% probable or higher that most of the warming is caused by gases such as carbon dioxide which are becoming more concentrated in the Earth's atmosphere as a result of human activity such as deforestation and burning fossil fuels.
The IPCC Fifth Assessment Report Summary for Policymakers (2014) stated that there is no doubt that the earth's climate system is warming, and that the various changes now taking place have not been seen for periods ranging from decades to millenia, including warming of the atmosphere and oceans, loss of snow and ice, and rises in sea level.
Global warming is causing climate change. Even small changes in the overall average surface temperature of the planet will cause large changes in climate in many different areas worldwide, and even though some temperate or cold areas may benefit, the overall effects are extremely likely to be negative.