TFE.9, Table 1 - Extreme weather and climate events: Global-scale assessment of recent observed changes, human contribution to the changes and projected further changes for the early (2016–2035) and late (2081–2100) 21st century

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TFE.9, Table 1 - Extreme weather and climate events: Global-scale assessment of recent observed changes, human contribution to the changes and projected further changes for the early (2016–2035) and late (2081–2100) 21st century
Phenomenon and direction of trend	Assessment that changes occurred (typically since 1950 unless otherwise indicated)	Assessment of a human contribution to observed changes	Likelihood of further changes
Phenomenon and direction of trend		Assessment of a human contribution to observed changes	Early 21^st century	Late 21^st century
* The direct comparison of assessment findings between reports is difficult. For some climate variables, different aspects have been assessed, and the revised guidance note on uncertainties has been used for the SREX and AR5. The availability of new information, improved scientific understanding, continued analyses of data and models, and specific differences in methodologies applied in the assessed studies, all contribute to revised assessment findings. Notes: ^a Attribution is based on available case studies. It is likely that human influence has more than doubled the probability of occurrence of some observed heat waves in some locations. ^b Models project near-term increases in the duration, intensity and spatial extent of heat waves and warm spells. ^c In most continents, confidence in trends is not higher than medium except in North America and Europe where there have been likely increases in either the frequency or intensity of heavy precipitation with some seasonal and/or regional variation. It is very likely that there have been increases in central North America. ^d The frequency and intensity of drought has likely increased in the Mediterranean and West Africa and likely decreased in central North America and north-west Australia. ^e AR4 assessed the area affected by drought. ^f SREX assessed medium confidence that anthropogenic influence had contributed to some changes in the drought patterns observed in the second half of the 20th century, based on its attributed impact on precipitation and temperature changes. SREX assessed low confidence in the attribution of changes in droughts at the level of single regions. ^g There is low confidence in projected changes in soil moisture. ^h Regional to global-scale projected decreases in soil moisture and increased agricultural drought are likely (medium confidence) in presently dry regions by the end of this century under the RCP8.5 scenario. Soil moisture drying in the Mediterranean, Southwest USA and southern African regions is consistent with projected changes in Hadley circulation and increased surface temperatures, so there is high confidence in likely surface drying in these regions by the end of this century under the RCP8.5 scenario. ⁱ There is medium confidence that a reduction in aerosol forcing over the North Atlantic has contributed at least in part to the observed increase in tropical cyclone activity since the 1970s in this region. ^j Based on expert judgment and assessment of projections which use an SRES A1B (or similar) scenario. k Attribution is based on the close relationship between observed changes in extreme and mean sea level. ^l There is high confidence that this increase in extreme high sea level will primarily be the result of an increase in mean sea level. There is low confidence in region-specific projections of storminess and associated storm surges. ^m SREX assessed it to be very likely that mean
Warmer and/or fewer cold days and nights over most land areas	Very likely {2.6} Very likely Very likely	Very likely {10.6} Likely Likely	Likely {11.3}	Virtually certain {12.4} Virtually certain Virtually certain
Warmer and/or more frequent hot days and nights over most land areas	Very likely {2.6} Very likely Very likely	Very likely {10.6} Likely Likely (nights only)	Likely {11.3}	Virtually certain {12.4} Virtually certain Virtually certain
Warm spells/heat waves. Frequency and/or duration increases over most land areas	Medium confidence on a global scale Likely in large parts of Europe, Asia and Australia {2.6} Medium confidence in many (but not all) regions Likely	Likely^a {10.6} Not formally assessed More likely than not	Not formally assessed^b {11.3}	Very likely {12.4} Very likely Very likely
Heavy precipitation events. Increase in the frequency, intensity, and/or amount of heavy precipitation	Likely more land areas with increases than decreases^c {2.6} Likely more land areas with increases than decreases Likely over most land areas	Medium confidence {7.6, 10.6} Medium confidence More likely than not	Likely over many land areas {11.3}	Very likely over most of the mid-latitude land masses and over wet tropical regions {12.4} Likely over many areas Very likely over most land areas
Increases in intensity and/or duration of drought	Low confidence on a global scale Likely changes in some regions^d {2.6} Medium confidence in some regions Likely in many regions, since 1970^e	Low confidence {10.6} Medium confidence^f More likely than not	Low confidence^g {11.3}	Likely (medium confidence) on a regional to global scale^h {12.4} Medium confidence in some regions Likely^e
Increases in intense tropical cyclone activity	Low confidence in long term (centennial) changes Virtually certain in North Atlantic since 1970 {2.6} Low confidence Likely in some regions, since 1970	Low confidenceⁱ {10.6} Low confidence More likely than not	Low confidence {11.3}	More likely than not in the Western North Pacific and North Atlantic^j {14.6} More likely than not in some basins Likely
Increased incidence and/or magnitude of extreme high sea level	Likely (since 1970) {3.7} Likely (late 20th century) Likely	Likely^k {3.7} Likely^k More likely than not^k	Likely^l {13.7}	Very likely^l {13.7} Very likely^m Likely

TFE.9, Table 1 - Extreme weather and climate events: Global-scale assessment of recent observed changes, human contribution to the changes and projected further changes for the early (2016–2035) and late (2081–2100) 21st century. Bold indicates where the AR5 (black) provides a revised* global-scale assessment from the Special Report on Managing the Risk of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX, blue) or AR4 (red). Projections for early 21st century were not provided in previous assessment reports. Projections in the AR5 are relative to the reference period of 1986–2005, and use the new RCP scenarios unless otherwise specified. See the Glossary for definitions of extreme weather and climate events.

Source: IPCC Climate Change 2013: Technical Summary, p.110