evidence: Geological records of Earth's history show that sea levels have risen and fallen during Earth's periods of warming and cooling. During past warming periods millions of years ago when global temperatures were around 1.5-3.6°C above preindustrial levels, global average sea levels could have been as much as 100 feet higher than they are today. Global average sea levels have risen 8-9 inches since 1880, a third of that rise occurring in the last 25 years. The IPCC is "virtually certain" that SLR will continue through the 21st century and for centuries to come due to continued ocean warming and ice sheet melt. Global average sea levels are predicted to rise 2-3 meters in the 21st century, even if drastic GHG reductions are successful in limiting global warming to 2°C.