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mean surface temperature increases. As well as it was also projected that the
global
volume of glaciers would continue to decrease.
The Working Group I Sixth Report was published in 2021 (Arias et al., 2021)
and generally confirms the findings, predictions, and conclusions of the Fifth
and previous Reports. Once again, the unequivocal human influence on the
atmosphere, ocean, and biospheric warming is highlighted. In addition, the
Report points out that the several rapid changes in the atmosphere, ocean,
cryosphere, and biosphere observed in the last two decades are signs that:
Climate change is already manifesting itself in the present and will become
more evident in the coming decades.
The scale of recent changes and the present state of many aspects of the climate
system have been unprecedented in the last hundreds and thousands of years.
All regions of the planet are already affected by extreme weather and climate
events, such as heat waves, heavy precipitation events, droughts, and tropical
cyclones. Advances in knowledge of climate processes incorporated into new
climate change simulations, paleoclimate evidence, and the climate system
response to increased radiative forcing give the best estimate for the sensitivity
of the equilibrium climate at 3ºC with a narrower range compared to the Fifth
Report. The global surface temperature will continue to increase until at least
the middle of this century under the emissions scenarios considered.
Global warming of 1.5ºC and 2ºC will be exceeded unless significant CO2
and other GHGs are reduced in the coming decades.
Many changes in the climate system have increased in direct relation to global
warming. These include increased frequency and intensity of heat waves,
marine heat waves and heavy precipitation, agricultural and ecological droughts
in some regions, intense tropical cyclones, and reduction in Arctic sea-ice and
snow cover and permafrost. Global warming is projected to continue and
intensify the water cycle, including its variability, global monsoon precipitation,
and the severity of dry and wet events.
In addition, the latest report evaluates the results of climate models participating
in Phase 6 of the Coupled Model Intercomparison Project (CMIP6) of the World
Climate Research Program. These models include new representation, higher
resolution in global climate models, and improvements in physical, chemical,
and biological processes compared to models considered in previous reports.
This has improved the simulation of the present mean state of most large-scale
environmental indicators of climate change and many other aspects of the
climate system. Information about how well the models simulate past warming