In general, human activity has potentially caused some major, irreversible climate changes. According to the Intergovernmental Panel on Climate Change, human activity has very likely contributed to the continuous rising of the sea level the past 50 years and has likely affected wind patterns, affecting tropical storms. It has also likely increased the temperature of extreme hot nights and extreme cold days, and has somewhat likely increased the risk of heat waves [7].
Specifically in terms of the effects of fossil fuel burning by humans, it is very likely that fossil fuel burning has increased the global average temperature. If this is the case, it is possible that ice sheets on polar land could start melting more and more if fossil fuel burning does not stop. Also, it is slightly possible that the irreversible process of extinction of 20-30 percent of species could become extinct if the global average warming exceeds 1.5°C to 2.5°C (relative to 1980-1999) [7].
