47
Current Status and Trends
Section 2
Table 2.1: Assessment of observed changes in large-scale indicators of mean climate across climate system components, and their attribution to human 
inﬂuence. The colour coding indicates the assessed conﬁdence in / likelihood76 of the observed change and the human contribution as a driver or main driver (speciﬁed in that case) 
where available (see colour key). Otherwise, explanatory text is provided. {WGI Table TS.1}
76 
Based on scientiﬁc understanding, key ﬁndings can be formulated as statements of fact or associated with an assessed level of conﬁdence indicated using the IPCC calibrated language.
likely range of human contribution 
([0.8-1.3°C]) encompasses the very likely 
range of observed warming ([0.9-1.2°C])
Observed change
assessment 
Human contribution
assessment 
Main driver
Main driver 1979 - mid-1990s
Southern Hemisphere
Main driver
Main driver
Main driver
Limited evidence & medium agreement 
Main driver
Main driver
Main driver
Main driver
Change in indicator
Warming of global mean surface air temperature since 1850-1900
Warming of the troposphere since 1979
Cooling of the lower stratosphere since the mid-20th century
Large-scale precipitation and upper troposphere humidity changes since 1979
Expansion of the zonal mean Hadley Circulation since the 1980s
Ocean heat content increase since the 1970s
Salinity changes since the mid-20th century
Global mean sea level rise since 1970
Arctic sea ice loss since 1979
Reduction in Northern Hemisphere springtime snow cover since 1950
Greenland ice sheet mass loss since 1990s
Antarctic ice sheet mass loss since 1990s
Retreat of glaciers
Increased amplitude of the seasonal cycle of
atmospheric CO2 since the early 1960s
Acidiﬁcation of the global surface ocean
Mean surface air temperature over land
(about 40% larger than global mean warming)
Warming of the global climate system since preindustrial times
medium
conﬁdence
likely / high
conﬁdence
very likely
extremely
likely
virtually
certain
fact
Atmosphere 
and water cycle
Ocean
Cryosphere
Carbon cycle
Land climate
Synthesis
Key