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600 | AR6_WGI | 323 | 31 | Surface/low altitude ozone trends since the mid-1990s are variable at northern mid-latitudes, but positive in the tropics [2 to 17% per decade] | high | 2 | train |
601 | AR6_WGI | 323 | 32 | Since the mid-1990s, free tropospheric ozone has increased by 2–7% per decade in most regions of the northern mid-latitudes, and 2–12% per decade in the sampled regions of the northern and southern tropics | high | 2 | train |
602 | AR6_WGI | 323 | 33 | Limited coverage by surface observations precludes identification of zonal trends in the SH, while observations of tropospheric column ozone indicate increases of less than 5% per decade at southern mid-latitudes | medium | 1 | test |
603 | AR6_WGI | 326 | 1 | Satellite data and ground-based records indicate that AOD exhibits predominantly negative trends since 2000 over NH mid-latitudes and SH continents, but increased over South Asia and East Africa | high | 2 | train |
604 | AR6_WGI | 326 | 30 | In summary, biophysical effects from historical changes in land use have an overall negative ERF | medium | 1 | train |
605 | AR6_WGI | 326 | 31 | The best-estimate ERF from the increase in global albedo is –0.15 W m–2 since 1700 and –0.12 W m–2 since 1850 | medium | 1 | train |
606 | AR6_WGI | 326 | 32 | Biophysical effects of land-use change likely resulted in a net global cooling of about 0.1°C since 1750 | medium | 1 | train |
607 | AR6_WGI | 327 | 11 | The net effect of aerosols (Sections 2.2.6 and 6.4) on the radiation budget, including their effect on clouds, and cloud adjustments, as well as the deposition of black carbon on snow (Section 7.3.4.3), was negative throughout the industrial period | high | 2 | train |
608 | AR6_WGI | 328 | 1 | The relative importance of aerosol forcing compared to other forcing agents has decreased globally in the most recent 30 years | medium | 1 | train |
609 | AR6_WGI | 328 | 3 | This effect increased since 1750, reaching current values of about –0.20 W m–2 | medium | 1 | train |
610 | AR6_WGI | 330 | 14 | The AR5 concluded that the reconstructed GMST during the PETM was 4°C–7°C warmer than pre-PETM mean climate (low confidence), and that the EECO and the MPWP were 9°C–14°C and 1.9°C–3.6°C warmer than pre-industrial, respectively | medium | 1 | train |
611 | AR6_WGI | 330 | 15 | The GMST during the LIG was assessed at 1°C–2°C warmer than pre-industrial | medium | 1 | train |
612 | AR6_WGI | 331 | 3 | Together, these studies indicate that GMST was 4°C–10°C warmer during the MCO | medium | 1 | train |
613 | AR6_WGI | 331 | 15 | In summary, GMST during the warmest millennia of the LIG (within the interval of around 129–125 ka) is estimated to have reached 0.5°C–1.5°C higher values than the 1850–1990 reference period | medium | 1 | train |
614 | AR6_WGI | 331 | 26 | In summary, GMST is estimated to have been 5°C–7°C lower during the LGM (around 23–19 ka) compared with 1850–1900 | medium | 1 | train |
615 | AR6_WGI | 331 | 32 | For average annual NH temperatures, the period 1983–2012 was assessed as very likely the warmest 30-year period of the past 800 years (high confidence) and likely the warmest 30-year period of the past 1.4 kyr (medium confidence); the warm multi-decadal periods prior to the 20th century were unsynchronized across regions, in contrast to the warming since the mid-20th century | high | 2 | train |
616 | AR6_WGI | 333 | 4 | Taking all lines of evidence into account, the GMST averaged over the warmest centuries of the current interglacial period (sometime between around 6 and 7 ka) is estimated to have been 0.2°C–1.0°C higher than 1850–1900 | medium | 1 | train |
617 | AR6_WGI | 333 | 11 | Moreover, the new proxy data compilation shows that the warming of the 20th century was more spatially uniform than any other century-scale temperature change of the CE | medium | 1 | train |
618 | AR6_WGI | 333 | 14 | To conclude, following approximately 6 ka, GMST generally decreased, culminating in the coldest multi-century interval of the post-glacial period (since 8 ka), which occurred between around 1450 and 1850 | high | 2 | train |
619 | AR6_WGI | 333 | 16 | Since around 1950, GMST has increased at an observed rate unprecedented for any 50-year period in at least the last 2000 years | high | 2 | train |
620 | AR6_WGI | 334 | 15 | The effect of this change from trend-based to change-based metrics is currently relatively minor at –0.03°C (<5%) for the most recent decade, but this may not remain the case in future | high | 2 | train |
621 | AR6_WGI | 336 | 10 | Given the projected future sea ice losses, the effect will grow in future | low | 0 | test |
622 | AR6_WGI | 337 | 19 | The other half arises because, for central estimates of climate sensitivity, most scenarios show stronger warming over the near term than was assessed as ‘current’ in SR1.5 | medium | 1 | train |
623 | AR6_WGI | 339 | 16 | The assessment of the implications of limiting global warming to 1.5°C compared to 2°C will also remain broadly unchanged by the updated estimate of historical warming, as this depends on the relative impacts rather than the absolute impacts at any specific definition of global temperature anomaly | high | 2 | train |
624 | AR6_WGI | 339 | 20 | The SRCCL concluded that since the pre-industrial period, surface air temperature over land areas has risen nearly twice as much as the global mean surface temperature | high | 2 | train |
625 | AR6_WGI | 346 | 7 | There are indications from multiple sources of a wetting trend during the Holocene, particularly for the NH and parts of the SH tropics | medium | 1 | train |
626 | AR6_WGI | 346 | 8 | Hydroclimate during the CE is dominated by regional variability, generally precluding definitive statements on changes at continental and larger scales, with a general reduction of mega-drought occurrences over the last about 500 years | medium | 1 | train |
627 | AR6_WGI | 348 | 27 | In summary, globally averaged land precipitation has likely increased since the middle of the 20th century | medium | 1 | train |
628 | AR6_WGI | 348 | 28 | A faster increase in global land precipitation was observed since the 1980s | medium | 1 | train |
629 | AR6_WGI | 351 | 14 | In summary, the sign of global streamflow trends remains uncertain, with slightly more globally gauged rivers experiencing significantly decreasing flows than significantly increasing flows since the 1950s | low | 0 | train |
630 | AR6_WGI | 353 | 10 | This has been accompanied by a strengthening of the Hadley circulation, particularly in the NH | medium | 1 | train |
631 | AR6_WGI | 353 | 41 | In summary, observed trends during the last century indicate that the GM precipitation decline reported in AR5 has reversed since the 1980s, with a likely increase mainly due to a significant positive trend in the NH summer monsoon precipitation | medium | 1 | train |
632 | AR6_WGI | 355 | 7 | In summary, the total number of extratropical cyclones has likely increased since the 1980s in the NH | low | 0 | train |
633 | AR6_WGI | 355 | 8 | The number of strong extratropical cyclones has likely increased in the SH | medium | 1 | train |
634 | AR6_WGI | 355 | 9 | The extratropical jets and cyclone tracks have likely been shifting poleward in both hemispheres since the 1980s with marked seasonality in trends | medium | 1 | train |
635 | AR6_WGI | 357 | 32 | This was confirmed by SROCC reporting the strongest reductions in September (12.8 ± 2.3% per decade; 1979–2018) and stating that these changes were likely unprecedented in at least 1 kyr | medium | 1 | train |
636 | AR6_WGI | 357 | 33 | The spatial extent had decreased in all seasons, with the largest decrease for September | high | 2 | train |
637 | AR6_WGI | 357 | 34 | The AR5 reported also that the average winter sea ice thickness within the Arctic Basin had likely decreased by between 1.3 m and 2.3 m from 1980 to 2008 | high | 2 | train |
638 | AR6_WGI | 358 | 1 | Lower sea ice volume in 2010–2012 compared to 2003–2008 was documented in AR5 | medium | 1 | train |
639 | AR6_WGI | 359 | 14 | In summary, over 1979–2019 Arctic SIA has decreased for all months, with the strongest decrease in summer | very high | 3 | train |
640 | AR6_WGI | 359 | 16 | Arctic sea ice has become younger, thinner and faster moving | very high | 3 | train |
641 | AR6_WGI | 359 | 17 | Snow thickness on sea ice has decreased in the western Arctic Ocean | medium | 1 | train |
642 | AR6_WGI | 359 | 19 | Current pan-Arctic sea ice coverage levels (annual mean and late summer) are unprecedentedly low since 1850 | high | 2 | train |
643 | AR6_WGI | 359 | 22 | The SROCC stated also that historical Antarctic sea ice data from different sources indicated a decrease in overall Antarctic sea ice cover since the early 1960s, but was too small to be separated from natural variability | high | 2 | train |
644 | AR6_WGI | 360 | 15 | The 2020 September level (OSISAF) remains below the levels observed over 2012–2014.In summary, Antarctic sea ice has experienced both increases and decreases in SIA over 1979–2019, and substantively lower levels since 2016, with only minor differences between decadal means of SIA for the first (for February 2.04 million km2, for September 15.39 million km2) and last decades (for February 2.17 million km2, for September 15.75 million km2) of satellite observations | high | 2 | train |
645 | AR6_WGI | 361 | 5 | In summary, substantial reductions in spring snow cover extent have occurred in the NH since 1978 | very high | 3 | train |
646 | AR6_WGI | 361 | 6 | Since 1981 there has been a general decline in NH spring snow water equivalent | high | 2 | train |
647 | AR6_WGI | 361 | 9 | The SROCC reported a globally coherent picture of continued glacier recession in recent decades | very high | 3 | train |
648 | AR6_WGI | 362 | 5 | The current global character of glacier mass loss is highly unusual (almost all glaciers simultaneously receding) in the context of at least the last 2 kyr | medium | 1 | train |
649 | AR6_WGI | 362 | 6 | Glacier mass loss rates have increased since the 1970s | high | 2 | train |
650 | AR6_WGI | 362 | 7 | Although many surveyed glaciers are currently more extensive than during the MH | high | 2 | train |
651 | AR6_WGI | 362 | 11 | It reported that the GrIS had lost ice during the prior two decades (very high confidence), that the ice loss had occurred in several sectors, and that high rates of mass loss had both expanded to higher elevations | high | 2 | train |
652 | AR6_WGI | 362 | 13 | The SROCC also found that summer melting rate had increased since the 1990s to a rate unprecedented over the last 350 years (very high confidence), being two to five times greater than the pre-industrial rates | medium | 1 | train |
653 | AR6_WGI | 363 | 2 | In summary, the GrIS was smaller than present during the MPWP (medium confidence), LIG (high confidence) and the MH | high | 2 | train |
654 | AR6_WGI | 363 | 3 | GrIS mass loss began following a peak volume attained during the 1450–1850 period and the rate of loss has increased substantially since the turn of the 21st century | high | 2 | train |
655 | AR6_WGI | 363 | 8 | The SROCC concluded that over 2006–2015, the AIS lost mass at an average rate of 155 ± 19 Gt yr –1 | very high | 3 | train |
656 | AR6_WGI | 363 | 21 | Overall, during the MH, the AIS was retreating, but remained more extensive than present, while some parts of the ice sheet might have been smaller than now | low | 0 | train |
657 | AR6_WGI | 364 | 1 | In summary, the AIS has lost mass between 1992 and 2020 | very high | 3 | train |
658 | AR6_WGI | 364 | 2 | During the MPWP and LIG, the ice sheet was smaller than present | medium | 1 | train |
659 | AR6_WGI | 364 | 6 | The AR5 also noted positive trends in active layer thickness (ALT; the seasonally thawed layer above the permafrost) since the 1990s for many high latitude sites | medium | 1 | train |
660 | AR6_WGI | 364 | 7 | The SROCC concluded permafrost temperatures have increased to record high levels since the 1980s | very high | 3 | train |
661 | AR6_WGI | 365 | 2 | In summary, increases in permafrost temperatures in the upper 30 m have been observed since the start of observational programs over the past three to four decades throughout the permafrost regions | high | 2 | train |
662 | AR6_WGI | 365 | 3 | Limited evidence suggests that permafrost was less extensive during the MPWP | low | 0 | train |
663 | AR6_WGI | 365 | 4 | Permafrost that formed after 3ka still persists in areas of the NH, but there are indications of thaw after the mid-1800s | medium | 1 | test |
664 | AR6_WGI | 366 | 6 | In summary, current multi-decadal to centennial rates of OHC gain are greater than at any point since the last deglaciation | medium | 1 | train |
665 | AR6_WGI | 366 | 7 | At multi-centennial timescales, changes in OHC based upon proxy indicators demonstrate a tight link with surface temperature changes during the last deglaciation (high confidence), as well as during the Holocene and CE | low | 0 | train |
666 | AR6_WGI | 368 | 18 | The differences between high-salinity and low- salinity regions are linked to an intensification of the hydrological cycle | medium | 1 | train |
667 | AR6_WGI | 369 | 2 | AR5 reported that GMSL during the LIG was, over several thousand years, between 5 and 10 m higher than 1985–2004 (medium confidence) whereas SROCC concluded it was virtually certain that GMSL exceeded current levels (high confidence), and reached a peak that was likely 6–9 m higher than today, but did not exceed 10 m | medium | 1 | train |
668 | AR6_WGI | 369 | 7 | Given that GMSL change must be due to some combination of transient land ice growth and changes in terrestrial water storage, additional global mean thermosteric sea-level increase of 7 ± 2 m (Fischer et al., 2018) implies a peak EECO GMSL of 70–76 m | low | 0 | train |
669 | AR6_WGI | 369 | 10 | Thus, consistent with SROCC, GMSL during the MPWP was higher than present by 5–25 m | medium | 1 | train |
670 | AR6_WGI | 369 | 14 | It shows that GMSL during the Holocene was among the highest over this entire interval, and was surpassed only during the LIG (Marine Isotope Stage (MIS 5e)) and MIS 11 | medium | 1 | train |
671 | AR6_WGI | 369 | 32 | The fastest rise occurred during Meltwater Pulse 1A, at about 14.6–14.3 ka (Deschamps et al., 2012; Sanborn et al., 2017), when GMSL rose by between 8 m and 15 m | medium | 1 | test |
672 | AR6_WGI | 371 | 16 | In summary, GMSL is rising, and the rate of GMSL rise since the 20th century is faster than over any preceding century in at least the last three millennia | high | 2 | train |
673 | AR6_WGI | 371 | 21 | SROCC assessed that there was emerging evidence in sustained observations, both in situ (2004–2017) and revealed from SST-based reconstructions, that the AMOC had weakened during the instrumental era relative to 1850–1900 | medium | 1 | train |
674 | AR6_WGI | 372 | 15 | In summary, proxy-based reconstructions suggest that the AMOC was relatively stable during the past 8 kyr (medium confidence), with a weakening beginning since the late 19th century | medium | 1 | train |
675 | AR6_WGI | 372 | 16 | From the mid-2000s to mid-2010s, the directly observed weakening in AMOC (high confidence) cannot be distinguished between decadal-scale variability or a long-term trend | high | 2 | train |
676 | AR6_WGI | 373 | 12 | In summary, over the past 3–4 decades, the WBC strength is highly variable (high confidence), and WBCs and subtropical gyres have shifted poleward since 1993 | medium | 1 | train |
677 | AR6_WGI | 373 | 13 | Net Arctic Ocean volume exchanges with the other ocean basins remained stable over the mid-1990s to the mid-2010s | high | 2 | train |
678 | AR6_WGI | 374 | 9 | To conclude, it is virtually certain that surface open ocean pH has declined globally over the last 40 years by 0.003–0.026 pH per decade, and a decline in the ocean interior has been observed in all ocean basins over the past 2–3 decades | high | 2 | train |
679 | AR6_WGI | 374 | 10 | A long-term increase in surface open ocean pH occurred over the past 50 Myr, and surface open ocean pH as low as recent times is uncommon in the last 2 Myr | medium | 1 | test |
680 | AR6_WGI | 374 | 14 | Multidecadal rates of deoxygenation showed variability throughout the water column and across ocean basins | high | 2 | train |
681 | AR6_WGI | 375 | 17 | In summary, episodes of widespread and long-lasting (100 ka scales) open-ocean deoxygenation were related to warm climate intervals of the Permian-Cretaceous, with conditions becoming generally better oxygenated as the climate cooled over the course of the Cenozoic | high | 2 | train |
682 | AR6_WGI | 375 | 18 | The largest expansions of oxygen depleted waters over the past 25 ka were strongly linked to rapid warming rates | medium | 1 | train |
683 | AR6_WGI | 375 | 19 | Open-ocean deoxygenation has occurred in most regions of the open ocean during the mid-20th to early 21st centuries (high confidence), and shows decadal variability | medium | 1 | train |
684 | AR6_WGI | 375 | 20 | Evidence further confirms SROCC that OMZs are expanding at many locations | high | 2 | train |
685 | AR6_WGI | 376 | 8 | Similarly, globally-integrated results from the SH also show an increase in seasonal amplitude of atmospheric CO 2 signal, from around 2009 to 2018 | low | 0 | train |
686 | AR6_WGI | 376 | 12 | With respect to distributions of marine organisms, AR5 WGII reported range shifts of benthic, pelagic, and demersal species and communities | high | 2 | train |
687 | AR6_WGI | 378 | 12 | A small decrease in productivity is evident globally for the period 1998–2015, but regional changes are larger and of opposing signs | low | 0 | test |
688 | AR6_WGI | 378 | 30 | New in situ data as well as satellite observations strengthen AR5 and SROCC findings that various phenological metrics for many species of marine organisms have changed in the last half century | high | 2 | test |
689 | AR6_WGI | 378 | 31 | The changes vary with location and with species | high | 2 | train |
690 | AR6_WGI | 378 | 32 | There is a strong dependence of survival in higher trophic-level organisms (fish, exploited invertebrates, birds) on the availability of food at various stages in their life cycle, which in turn depends on phenologies of both | high | 2 | train |
691 | AR6_WGI | 380 | 10 | Similarly, SRCCL assessed that many land species have experienced range size and location changes as well as altered abundances over recent decades | high | 2 | train |
692 | AR6_WGI | 380 | 11 | SROCC noted that species composition and abundance have markedly changed in high mountain ecosystems in recent decades | very high | 3 | train |
693 | AR6_WGI | 381 | 12 | The SRCCL subsequently concluded that greening had increased globally over the past 2–3 decades | high | 2 | train |
694 | AR6_WGI | 383 | 9 | Many more integrative components of the climate system (e.g., glaciers, GMSL) are experiencing conditions unseen in millennia, whereas the most slowly responding components (e.g., ice-sheet extent, permafrost, tree line) are at levels unseen in centuries | high | 2 | train |
695 | AR6_WGI | 383 | 10 | The rate at which several assessed climate indicators (e.g., GMSL, OHC, GSAT) have changed over recent decades is highly unusual in the context of preceding slower changes during the current post-glacial period | high | 2 | train |
696 | AR6_WGI | 386 | 3 | Moreover, periods of persistent negative or positive NAO states observed during the latter part of the 20th century were not unusual, based on NAO reconstructions spanning the last half millennium | high | 2 | train |
697 | AR6_WGI | 386 | 18 | In summary, positive trends for the NAM/NAO winter indices were observed between the 1960s and the early 1990s, but these indices have become less positive or even negative thereafter | high | 2 | train |
698 | AR6_WGI | 387 | 11 | In summary, historical station-based reconstructions of the SAM show that there has been a robust positive trend in the SAM index, particularly since 1950 and for the austral summer | high | 2 | train |
699 | AR6_WGI | 387 | 14 | It was also found | high | 2 | train |