An Intergovernmental Panel on Climate Change (IPPC) Special Report in 2018 states that human activities are estimated to have caused approximately 1.0 degree C of global warming with a likely range of 0.8 degrees C to 1.2 degrees C. Global warming is likely to reach 1.5 degree C between 2030 and 2052 if it continues to increase at the current rate (high confidence). .
This coincided with an increase in the average global temperature of 0.74°C between 1906 and 2005. In 2013, the U.S. National Oceanic and Atmospheric Administration announced that CO2 levels had reached 400ppm . The World Meteorological Organization (WMO) Greenhouse Gas Bulletin (No.14/22 Nov 2018) showed that globally averaged concentrations of carbon dioxide (CO2) reached 405.5 parts per million (ppm) in 2017, up from 403.3 ppm in 2016 and 400.1 ppm in 2015. . As far back as 2013, the IPCC concluded that "human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes.... it is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century" . The IPPC Climate Change 2014 Synthesis Report summed up observed changes in the climate system as follows: ‘Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished and sea level has risen. . In 2019, a research paper in the journal ‘Advances in Atmospheric Sciences’ states that 2018 has set a new record of ocean heating, surpassing 2017, which was the previous warmest year ever recorded. The vast majority of global warming heat ends up deposited in the world’s oceans, and ocean heat content change is one of the best – if not the best – metric for climate change.  While the World Meteorological Organization (WMO)  released its analysis in 2013 that shows that the decade spanning 2001-2010 was the warmest ever recorded in all continents of the globe, a February 2019 newsletter from the Climate Central organisation uses NASA and NOAA data to declare that 2018 was the fourth-hottest year on record globally, with the five warmest years on record happening during the past five years – and the 20 warmest occurring over the past 22 years.