The world 's getting hotter , the sea 's rising and there 's increasing evidence neither are naturally occurring phenomena . So says a report from the U.N. International Panel on Climate Change , a document released every six years that is considered the benchmark on the topic . More than 800 authors and 50 editors from dozens of countries took part in its creation . The summary for policymakers was released early Friday , while the full report , which bills itself as `` a comprehensive assessment of the physical science basis of climate change , '' will be distributed Monday . Other reports , including those dealing with vulnerability and mitigation , will be released next year . Here are the highlights from Friday 's summary : . Man-made climate change is almost certain . Climate scientists are 95 % confident -- that is to say , surer than ever -- that humans are responsible for at least `` half of the observed increase in global average surface temperatures since the 1950s . '' This is the major headline from the report , as it marks a stark spike in confidence over the last 12 years , as scientists were 90 % confident in 2007 and 66 % confident in 2001 of the same conclusion . An increase in carbon dioxide concentrations that is `` unprecedented '' in the last 20,000 years , along with increases in other emissions , have driven up average temperatures by about 0.6 degrees Celsius ( 1 degree Fahrenheit ) since 1950 , the report states . Worst-case predictions are that by 2100 , temperatures could increase by as much as 3.7 degrees Celsius ( 6.6 Fahrenheit ) , the report says . Climate change is already affecting extreme weather . Since 1950 we 've seen a dramatic increase in extreme weather . This is especially true of record heat and heavier precipitation events . While it 's difficult to determine the exact role climate change plays in an individual event , such as Hurricane Sandy or the EF-5 tornado that struck Moore , Oklahoma , because there are so many ingredients necessary to brew a single storm , the links are clearer when you look at overall patterns . According to a study released this month in the Bulletin of the American Meteorological Society , scientists found strong links between global warming and extreme weather around the globe in 2012 . Among the 2012 events were the July heat wave in the northeastern and north-central United States , the spring heat wave in the eastern United States , the Great Plains drought , the winter drought in Spain and Portugal and the heavy rains and flooding in Europe . According to a paper in the journal Nature , this year , weather events that have previously been classified as `` storms of the century '' could become the storm of `` every 20 years or less . '' `` Climate change will probably increase storm intensity and size simultaneously , resulting in a significant intensification of storm surges , '' the paper said . The last 30-year period is `` very likely '' the warmest in the last 800 years . Scientists are 90 % sure that 1981-2010 was the warmest such span in the last eight centuries , and there 's a 66 % chance that it was the warmest 30-year period in the last 1,400 years . While the last 15 years have not warmed as quickly , we 've seen steady warming over most of the globe , and we have n't seen a below-average temperature month since February 1985 . Scientists are also 99 % certain that we will see more hot days and nights -- and fewer chilly ones -- as the 21st century progresses . `` Each of the last three decades has been significantly warmer than all preceding decades since 1850 , '' according to the IPCC report . To give you an idea of how the Earth has heated up , the combined land and ocean temperature increased by about 0.8 degrees Celsius between 1901 and 2010 , yet between 1979 and 2010 , the temperature spiked about 0.5 degrees Celsius . Sea level rise will increase due to warming oceans and loss of ice . Better climate models give scientists more confidence that sea level rise will accelerate in the 21st century . Scientists are 99 % sure that sea level rise has accelerated over the last 2 centuries at a rate higher than at any time in the last 2,000 years . They 're also highly confident that if the global surface temperature increases by more than 2 degrees Celsius over present temperatures we could see `` a nearly ice-free Arctic Ocean in late summer . '' The report further notes that there is increasing evidence that ice sheets are losing mass , glaciers are shrinking , Arctic sea ice cover is diminishing , snow cover is decreasing and permafrost is thawing in the Northern Hemisphere . As for the rise in sea level , scientists asserted in the IPCC report that tide gauges and satellite data make it `` unequivocal '' that the world 's mean sea level is on the upswing . Even if we end emission tomorrow , climate change could continue for centuries . This may be one of the more harrowing findings in the report , as it suggests we 're too far gone to effect any meaningful change in our lifetimes . Even if we end carbon dioxide emissions today , effects could linger for hundreds , if not thousands , of years . And certain changes may already be irreversible . `` Many aspects of climate change will persist for centuries even if concentrations of greenhouse gases are stabilized . This represents a multicentury commitment created by human activities today , '' the report states .
Scientists surer than ever humans play major role in climate change , report says . Global warming already affecting extreme weather , and it could get worse , report says . U.N. 's IPCC convenes every six years to put together report ; it 's considered benchmark on topic . Comment: