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700 | AR6_WGI | 390 | 7 | Neither the IOD nor the IOB have exhibited behaviour outside the range implied by proxy records | low | 0 | train |
701 | AR6_WGI | 392 | 12 | In summary, no sustained change in AMV indices has been observed over the instrumental period | high | 2 | train |
702 | AR6_WGI | 441 | 11 | High-resolution models exhibit reduced biases in some but not all aspects of surface and ocean climate (medium confidence), and most Earth system models, which include biogeochemical feedbacks, perform as well as their lower-complexity counterparts | medium | 1 | train |
703 | AR6_WGI | 441 | 12 | The multi-model mean captures most aspects of observed climate change well | high | 2 | train |
704 | AR6_WGI | 441 | 13 | The multi-model mean captures the proxy-reconstructed global-mean surface air temperature (GSAT) change during past high- and low-CO 2 climates (high confidence) and the correct sign of temperature and precipitation change in most assessed regions in the mid-Holocene | medium | 1 | train |
705 | AR6_WGI | 441 | 14 | The simulation of paleoclimates on continental scales has improved compared to AR5 (medium confidence), but models often underestimate large temperature and precipitation differences relative to the present day | high | 2 | train |
706 | AR6_WGI | 441 | 19 | The likely ranges for human-induced GSAT and global mean surface temperature (GMST) warming are equal | medium | 1 | train |
707 | AR6_WGI | 441 | 26 | CMIP6 models broadly reproduce surface temperature variations over the past millennium, including the cooling that follows periods of intense volcanism | medium | 1 | train |
708 | AR6_WGI | 441 | 28 | The latest updates to satellite-derived estimates of stratospheric temperature have resulted in decreased differences between simulated and observed changes of global mean temperature through the depth of the stratosphere | medium | 1 | train |
709 | AR6_WGI | 441 | 31 | All the observed estimates of the 1998–2012 GMST trend lie within the 10th–90th percentile range of CMIP6 simulated trends | high | 2 | train |
710 | AR6_WGI | 441 | 32 | Internal variability, particularly Pacific Decadal Variability, and variations in solar and volcanic forcings partly offset the anthropogenic surface warming trend over the 1998–2012 period | high | 2 | train |
711 | AR6_WGI | 442 | 1 | Since 2012, GMST has warmed strongly, with the past five years (2016–2020) being the warmest five-year period in the instrumental record since at least 1850 | high | 2 | train |
712 | AR6_WGI | 442 | 5 | New attribution studies strengthen previous findings of a detectable increase in Northern Hemisphere mid- to high-latitude land precipitation | high | 2 | train |
713 | AR6_WGI | 442 | 6 | Human influence has contributed to strengthening the zonal mean precipitation contrast between the wet tropics and dry subtropics | medium | 1 | train |
714 | AR6_WGI | 442 | 7 | Yet, anthropogenic aerosols contributed to decreasing global land summer monsoon precipitation from the 1950s to 1980s | medium | 1 | train |
715 | AR6_WGI | 442 | 9 | Despite improvements, models still have deficiencies in simulating precipitation patterns, particularly over the tropical ocean | high | 2 | train |
716 | AR6_WGI | 442 | 13 | The magnitude and frequency of extreme precipitation simulated by CMIP6 models are similar to those simulated by CMIP5 models | high | 2 | train |
717 | AR6_WGI | 442 | 16 | The causes of the observed strengthening of the Pacific Walker circulation since the 1980s are not well understood, and the observed strengthening trend is outside the range of trends simulated in the coupled models | medium | 1 | train |
718 | AR6_WGI | 442 | 17 | While CMIP6 models capture the general characteristics of the tropospheric large-scale circulation (high confidence), systematic biases exist in the mean frequency of atmospheric blocking events, especially in the Euro-Atlantic sector, some of which reduce with increasing model resolution | medium | 1 | train |
719 | AR6_WGI | 442 | 19 | There is new evidence that increases in anthropogenic aerosols have offset part of the greenhouse gas-induced Arctic sea ice loss since the 1950s | medium | 1 | train |
720 | AR6_WGI | 442 | 20 | In the Arctic, despite large differences in the mean sea ice state, loss of sea ice extent and thickness during recent decades is reproduced in all CMIP5 and CMIP6 models | high | 2 | train |
721 | AR6_WGI | 442 | 23 | The seasonal cycle in Northern Hemisphere snow cover is better reproduced by CMIP6 than by CMIP5 models | high | 2 | train |
722 | AR6_WGI | 442 | 29 | Updated observations and model simulations show that warming extends throughout the entire water column | high | 2 | train |
723 | AR6_WGI | 442 | 30 | The structure and magnitude of multi-model mean ocean temperature biases have not changed substantially between CMIP5 and CMIP6 | medium | 1 | train |
724 | AR6_WGI | 442 | 32 | The associated pattern of change corresponds to fresh regions becoming fresher and salty regions becoming saltier | high | 2 | train |
725 | AR6_WGI | 442 | 33 | Changes to the coincident atmospheric water cycle and ocean-atmosphere fluxes (evaporation and precipitation) are the primary drivers of the observed basin-scale salinity changes | high | 2 | train |
726 | AR6_WGI | 443 | 1 | The basin-scale changes are consistent across models and intensify through the historical period | high | 2 | train |
727 | AR6_WGI | 443 | 2 | The structure of the biases in the multi-model mean has not changed substantially between CMIP5 and CMIP6 | medium | 1 | train |
728 | AR6_WGI | 443 | 9 | However, biases are apparent in the modelled circulation strengths (high confidence) and their variability | medium | 1 | train |
729 | AR6_WGI | 443 | 12 | Earth system models simulate globally averaged land carbon sinks within the range of observation-based estimates | high | 2 | train |
730 | AR6_WGI | 443 | 18 | The influence of ozone forcing on the SAM trend has been small since the early 2000s compared to earlier decades, contributing to a weaker SAM trend observed over 2000–2019 | medium | 1 | train |
731 | AR6_WGI | 443 | 19 | Climate models reproduce the summertime SAM trend well, with CMIP6 models outperforming CMIP5 models | medium | 1 | train |
732 | AR6_WGI | 443 | 21 | Models reproduce the observed spatial features and variance of the SAM and NAM very well | high | 2 | train |
733 | AR6_WGI | 443 | 23 | Further assessment since AR5 confirms that climate and Earth system models are able to reproduce most aspects of the spatial structure and variance of the El Niño–Southern Oscillation and Indian Ocean Basin and Dipole modes | medium | 1 | train |
734 | AR6_WGI | 443 | 28 | Uncertainties remain in quantification of the human influence on AMV and PDV due to brevity of the observational records, limited model performance in reproducing related sea surface temperature (SST) anomalies despite improvements from CMIP5 to CMIP6 | medium | 1 | train |
735 | AR6_WGI | 449 | 6 | CMIP6 models broadly reproduce surface temperature variations over the past millennium, including the cooling that follows periods of intense volcanism | medium | 1 | train |
736 | AR6_WGI | 449 | 7 | Simulated GMST anomalies are well within the uncertainty range of temperature reconstructions | medium | 1 | test |
737 | AR6_WGI | 449 | 8 | Before the year 1300, larger disagreements between models and temperature reconstructions are expected because forcing and temperature reconstructions are increasingly uncertain further back in time, but specific causes have not been identified conclusively (Ljungqvist et al., 2019; PAGES 2k Consortium, 2019) | medium | 1 | train |
738 | AR6_WGI | 454 | 18 | CMIP6 models also reproduce historical GSAT changes similarly to their CMIP5 counterparts | medium | 1 | train |
739 | AR6_WGI | 461 | 26 | In summary, based on the latest updates to satellite observations of stratospheric temperature, we assess that simulated and observed trends in global mean temperature through the depth of the stratosphere are more consistent than based on previous datasets, but some differences remain | medium | 1 | train |
740 | AR6_WGI | 462 | 13 | Therefore, the observed 1998–2012 trend is consistent with both the CMIP5 or CMIP6 multi-model ensemble of trends over the same period | high | 2 | train |
741 | AR6_WGI | 463 | 12 | Although there is noticeable uncertainty among observational products (H. Su et al., 2017) and observation quality changes through time, global ocean heat content continued to increase during the slower surface warming period | very high | 3 | test |
742 | AR6_WGI | 463 | 20 | Nonetheless, the heating of the climate system continued during this period, as reflected in the continued warming of the global ocean (very high confidence) and in the continued rise of hot extremes over land | medium | 1 | train |
743 | AR6_WGI | 463 | 23 | The past five-year period (2016–2020) is the hottest five-year period in the instrumental record up to 2020 | high | 2 | train |
744 | AR6_WGI | 465 | 7 | Records of tree ring width have provided evidence that recent prolonged dry spells in the Levant and Chile are unprecedented in the last millennium | high | 2 | train |
745 | AR6_WGI | 465 | 10 | Likewise, tree rings indicate that the 2012–2014 drought in the south-western United States was exceptionally severe in the context of natural variability over the last millennium, and may have been exacerbated by the contribution of anthropogenic temperature rise | medium | 1 | train |
746 | AR6_WGI | 465 | 13 | Nonetheless, tree rings also indicate the presence of prolonged megadroughts in western North America throughout the last millennium that were more severe than 20th and 21st century events | high | 2 | train |
747 | AR6_WGI | 466 | 4 | However, prescribing changes in vegetation and dust was found to improve the match to the paleoclimate record (Pausata et al., 2016; Tierney et al., 2017) suggesting that vegetation feedbacks in the CMIP5 models may be too weak | low | 0 | train |
748 | AR6_WGI | 468 | 30 | Based on these results we assess that despite some improvements, CMIP6 models still have deficiencies in simulating precipitation patterns, particularly over the tropical ocean | high | 2 | train |
749 | AR6_WGI | 470 | 11 | Global land precipitation has likely increased since the middle of the 20th century | medium | 1 | train |
750 | AR6_WGI | 472 | 11 | New attribution studies strengthen previous findings of a detectable increase in mid to high latitude land precipitation over the Northern Hemisphere | high | 2 | train |
751 | AR6_WGI | 472 | 36 | Moreover, human interventions and water withdrawals, while affecting streamflow, cannot explain the observed spatio-temporal trends | medium | 1 | train |
752 | AR6_WGI | 473 | 17 | The overall performance of CMIP6 models in simulating extreme precipitation intensity and frequency is similar to that of CMIP5 models | high | 2 | train |
753 | AR6_WGI | 477 | 9 | For the strong ozone depletion period of 1981–2000, human influence is detectable in the summertime poleward expansion in the Southern Hemisphere | medium | 1 | train |
754 | AR6_WGI | 477 | 11 | The causes of the observed strengthening of the Pacific Walker circulation over the 1980–2014 period are not well understood, since the observed strengthening trend is outside the range of variability simulated in the coupled models | medium | 1 | train |
755 | AR6_WGI | 477 | 18 | AR5 assessed that CMIP5 models simulated monsoons better than CMIP3 models but that biases remained in domains and intensity | high | 2 | train |
756 | AR6_WGI | 479 | 15 | In summary, while greenhouse gas increases acted to enhance the global land monsoon precipitation over the 20th century (medium confidence), consistent with projected future enhancement (Section 4.5.1.5), this tendency was overwhelmed by anthropogenic aerosols from the 1950s to the 1980s, which contributed to weakening of global land summer monsoon precipitation intensity for this period | medium | 1 | train |
757 | AR6_WGI | 479 | 19 | While CMIP5 models can capture the domain and precipitation intensity of the global monsoon, biases remain in their regional representations, and they are unsuccessful in quantitatively reproducing changes in paleo reconstructions | high | 2 | train |
758 | AR6_WGI | 479 | 20 | CMIP6 models reproduce the domain and precipitation intensity of the global monsoon observed over the instrumental period better than CMIP5 models | medium | 1 | train |
759 | AR6_WGI | 480 | 23 | Section 2.3.1.4.3 assesses that the total number of extratropical cyclones has likely increased since the 1980s in the Northern Hemisphere | low | 0 | train |
760 | AR6_WGI | 480 | 28 | Section 2.3.1.4.3 assesses that the extratropical jets and cyclone tracks have likely shifted poleward in both hemispheres since the 1980s with marked seasonality in trends | medium | 1 | train |
761 | AR6_WGI | 482 | 22 | The recent Arctic sea ice loss during summer is unprecedented since 1850 | high | 2 | train |
762 | AR6_WGI | 483 | 10 | Sea ice thermodynamic considerations indicate that the magnitude of sea ice variability and loss depends on ice thickness (Bitz, 2008; Massonnet et al., 2018) and hence the climatology simulated by different models may influence their simulated sea ice trends | medium | 1 | train |
763 | AR6_WGI | 483 | 11 | An important consideration in comparing Arctic sea ice loss in models and observations is the role of internal variability | medium | 1 | train |
764 | AR6_WGI | 484 | 12 | Increases in anthropogenic aerosols have offset part of the greenhouse gas induced Arctic sea ice loss since the 1950s | medium | 1 | train |
765 | AR6_WGI | 487 | 6 | CMIP6 models better represent the seasonality and geographical distribution of snow cover than CMIP5 simulations | high | 2 | train |
766 | AR6_WGI | 488 | 9 | Section 2.3.2.4.1 assesses that Greenland Ice Sheet mass loss began in the latter half of the 19th century and that the rate of loss has increased substantially since the turn of the 21st century | high | 2 | train |
767 | AR6_WGI | 488 | 25 | It further assessed that Antarctic ice loss is dominated by acceleration, retreat and rapid thinning of the major West Antarctic Ice Sheet outlet glaciers (very high confidence), driven by melting of ice shelves by warm ocean waters | high | 2 | train |
768 | AR6_WGI | 492 | 1 | Nevertheless, the CMIP6 models show a somewhat more realistic pattern of SST trends | low | 0 | test |
769 | AR6_WGI | 493 | 6 | The multi-model means of both CMIP5 and CMIP6 historical simulations forced with time varying natural and anthropogenic forcing shows robust increases in ocean heat content in the upper (0–700 m) and intermediate (700–2000 m) ocean | high | 2 | train |
770 | AR6_WGI | 494 | 14 | It is extremely likely that human influence was the main driver of the ocean heat content increase observed since the 1970s, which extends into the deeper ocean | very high | 3 | train |
771 | AR6_WGI | 494 | 15 | Updated observations, like model simulations, show that warming extends throughout the entire water column | high | 2 | train |
772 | AR6_WGI | 495 | 14 | The structure of the salinity biases in the multi-model mean has not changed substantially between CMIP5 and CMIP6 | medium | 1 | test |
773 | AR6_WGI | 497 | 5 | All available multi-decadal assessments have confirmed that the associated pattern of change corresponds to fresh regions becoming fresher and salty regions becoming saltier | high | 2 | train |
774 | AR6_WGI | 497 | 6 | CMIP5 and CMIP6 models are only able to reproduce these patterns in simulations that include greenhouse gas increases | medium | 1 | test |
775 | AR6_WGI | 497 | 7 | Changes to the coincident atmospheric water cycle and ocean-atmosphere fluxes (evaporation and precipitation) are the primary drivers of the basin-scale observed salinity changes | high | 2 | train |
776 | AR6_WGI | 497 | 9 | The basin-scale changes are consistent across models and intensify on centennial scales from the historical period through to the projections of future climate | high | 2 | train |
777 | AR6_WGI | 499 | 27 | As reported in Section 2.3.3.4.1, estimates of AMOC since at least 1950, which are generated from observed surface temperatures or sea surface height, suggest the AMOC weakened through the 20th century | low | 0 | train |
778 | AR6_WGI | 501 | 21 | In summary, while there have been improvements across successive CMIP phases (from CMIP3 to CMIP6) in the representation of the Southern Ocean circulation, such that the mean zonal and overturning circulations of the Southern Ocean are now broadly reproduced, substantial observational uncertainty and climate model challenges preclude attribution of Southern Ocean circulation changes | high | 2 | train |
779 | AR6_WGI | 501 | 24 | That increase was attributed to direct land use and management changes, as well as to CO 2 fertilization, nitrogen deposition, increased diffuse radiation and climate change | high | 2 | train |
780 | AR6_WGI | 503 | 40 | In summary, Earth system models simulate globally averaged land carbon sinks within the range of observation-based estimates | high | 2 | train |
781 | AR6_WGI | 504 | 15 | The decrease in ocean oxygen content in the upper 1000 m, between 1970 and 2010, is further confirmed in SROCC | medium | 1 | train |
782 | AR6_WGI | 505 | 6 | Section 5.2.1.3 assesses that both observational reconstructions based on the partial pressure of CO 2 and ocean biogeochemical models show a quasi-linear increase in the ocean sink of anthropogenic CO 2 from 1.0 ± 0.3 PgC yr–1 to 2.5 ± 0.6 PgC yr–1 between 1960–1969 and 2010–2019 in response to global CO 2 emissions | high | 2 | train |
783 | AR6_WGI | 509 | 9 | CMIP5 and CMIP6 models are skilful in simulating the spatial features and the variance of the NAM/NAO and associated teleconnections | high | 2 | test |
784 | AR6_WGI | 510 | 20 | However, despite the aforementioned limitations of the reconstructions, Section 2.4.1.2 assesses that the recent positive trend in the SAM is likely unprecedented in at least the past millennium | medium | 1 | train |
785 | AR6_WGI | 510 | 24 | While ozone depletion contributed to the trend from the 1970s to the 1990s (medium confidence), its influence has been small since 2000, leading to a weaker summertime SAM trend over 2000–2019 | medium | 1 | train |
786 | AR6_WGI | 510 | 25 | Climate models reproduce the spatial structure of the summertime SAM observed since the late 1970s well | high | 2 | train |
787 | AR6_WGI | 510 | 26 | CMIP6 models reproduce the spatiotemporal features and recent multi-decadal trend of the summertime SAM better than CMIP5 models | medium | 1 | train |
788 | AR6_WGI | 510 | 27 | However, there is a large spread in the intensity of the SAM response to ozone and greenhouse gas changes in both CMIP5 and CMIP6 models | high | 2 | train |
789 | AR6_WGI | 511 | 1 | CMIP5 and CMIP6 models do not capture multicentennial variability of the SAM found in proxy reconstructions | low | 0 | train |
790 | AR6_WGI | 511 | 16 | As assessed in Section 2.4.2, ENSO amplitude since 1950 is higher than over the pre-industrial period from 1850 as far back as 1400 | medium | 1 | train |
791 | AR6_WGI | 517 | 1 | Nevertheless, CMIP5 models have medium overall performance in reproducing both the interannual IOB and IOD modes, with an apparently good performance in reproducing the IOB magnitude arising from compensation of biases in the formation process, and overly high IOD magnitude due to the mean state bias | high | 2 | train |
792 | AR6_WGI | 520 | 3 | As such, PDV is an important driver of decadal internal climate variability which limits detection of human influence on various aspects of decadal climate change on global to regional scales | high | 2 | train |
793 | AR6_WGI | 520 | 5 | Despite the limitations of these model-observation comparisons, CMIP5 models, on average, simulate broadly realistic spatial structures of the PDV, but with a clear bias in the South Pacific | medium | 1 | train |
794 | AR6_WGI | 522 | 5 | In particular, anthropogenic and volcanic aerosols are thought to have played a role in the timing and intensity of the negative (cold) phase of AMV recorded from the mid-1960s to mid-1990s and subsequent warming | medium | 1 | train |
795 | AR6_WGI | 522 | 23 | The pattern of ocean salinity changes indicate that fresh regions are becoming fresher and that salty regions are becoming saltier as a result of changes in ocean-atmosphere fluxes through evaporation and precipitation | high | 2 | test |
796 | AR6_WGI | 526 | 1 | Earth System models characterized by additional biogeochemical feedbacks often perform at least as well as related more constrained, lower-complexity models lacking these feedbacks | medium | 1 | train |
797 | AR6_WGI | 526 | 2 | In many cases, the models score similarly against both observational references, indicating that model errors are usually larger than observational uncertainties | high | 2 | train |
798 | AR6_WGI | 526 | 3 | Moreover, synthesizing across Sections 3.3–3.7, we assess that the CMIP6 multi-model mean captures most aspects of observed climate change well | high | 2 | train |
799 | AR6_WGI | 528 | 27 | Overall, the PMIP multi-model means agree very well (within 0.5°C of the assessed range) with GSAT reconstructed from proxies across multiple time periods, spanning a range from 6°C colder than pre-industrial (Last Glacial Maximum) to 14°C warmer than pre-industrial (Early Eocene Climate Optimum) | high | 2 | train |
Subsets and Splits