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500 | AR6_WGI | 203 | 24 | By contrast, Antarctic sea ice extent overall saw no statistically significant trend for the period 1979–2018 | high | 2 | train |
501 | AR6_WGI | 204 | 1 | It also found evidence for an increase in the annual global proportion of Category 4 or 5 tropical cyclones in recent decades | low | 0 | train |
502 | AR6_WGI | 204 | 4 | The natural response of land to human-induced environmental change – such as increasing atmospheric CO 2 concentration, nitrogen deposition and climate change – caused a net CO 2 sink equivalent of around 29% of total CO 2 emissions (medium confidence); however, the persistence of the sink is uncertain due to climate change | high | 2 | train |
503 | AR6_WGI | 204 | 7 | However, the report estimated that the resulting net effect on globally averaged surface temperature was small over the historical period | medium | 1 | train |
504 | AR6_WGI | 204 | 8 | The SROCC found that the carbon content of Arctic and boreal permafrost is almost twice that of the atmosphere | medium | 1 | train |
505 | AR6_WGI | 204 | 9 | Projections of climate change The SR1.5 concluded that global warming is likely to reach 1.5°C between 2030 and 2052 if it continues to increase at the current rate | high | 2 | train |
506 | AR6_WGI | 204 | 11 | The SR1.5 also found that reaching and sustaining net zero anthropogenic CO 2 emissions and reducing net non-CO 2 radiative forcing would halt anthropogenic global warming on multi-decadal time scales | high | 2 | train |
507 | AR6_WGI | 204 | 12 | The maximum temperature reached is then determined by (i) cumulative net global anthropogenic CO 2 emissions up to the time of net zero CO 2 emissions (high confidence) and (ii) the level of non-CO 2 radiative forcing in the decades prior to the time that maximum temperatures are reached | medium | 1 | train |
508 | AR6_WGI | 204 | 13 | Furthermore, climate models project robust differences in regional climate characteristics between the present day and a global warming of 1.5°C, and between 1.5°C and 2°C, including mean temperature in most land and ocean regions and hot extremes in most inhabited regions | high | 2 | train |
509 | AR6_WGI | 204 | 15 | The SROCC projected that global-scale glacier mass loss, permafrost thaw, and decline in snow cover and Arctic sea ice extent will continue in the period 2031–2050 due to surface air temperature increases | high | 2 | train |
510 | AR6_WGI | 204 | 16 | The Greenland and Antarctic ice sheets are projected to lose mass at an increasing rate throughout the 21st century and beyond | high | 2 | train |
511 | AR6_WGI | 204 | 19 | For the RCP8.5 scenario, projections of GMSL rise by 2100 are higher by 0.1 m than in AR5 due to a larger contribution from the Antarctic Ice Sheet | medium | 1 | train |
512 | AR6_WGI | 204 | 20 | Extreme sea level events that occurred once per hundred years in the recent past are projected to occur at least once per year at many locations by 2050, especially in tropical regions, under all RCP scenarios | high | 2 | train |
513 | AR6_WGI | 204 | 21 | According to SR1.5, by 2100 GMSL rise would be around 0.1 m lower with 1.5°C global warming compared to 2°C | medium | 1 | train |
514 | AR6_WGI | 204 | 23 | However, instability and/or irreversible loss of the Greenland and Antarctic ice sheets, resulting in a multi-metre rise in sea level over hundreds to thousands of years, could be triggered at 1.5°C–2°C of global warming | medium | 1 | train |
515 | AR6_WGI | 204 | 24 | According to SROCC, sea level rise in an extended RCP2.6 scenario would be limited to around 1 m in 2300 (low confidence) while under RCP8.5 multi-metre sea level rise is projected by then | medium | 1 | train |
516 | AR6_WGI | 204 | 25 | The SROCC projected that over the 21st century, the ocean will transition to unprecedented conditions, with increased temperatures (virtually certain), further acidification (virtually certain), and oxygen decline | medium | 1 | train |
517 | AR6_WGI | 204 | 26 | Marine heatwaves are projected to become more frequent (very high confidence) as are extreme El Niño and La Niña events | medium | 1 | train |
518 | AR6_WGI | 205 | 20 | Starting from year 2018, the remaining carbon budget for a one-in-two (50%) chance of limiting global warming to 1.5°C is about 580 GtCO 2, and about 420 GtCO 2 for a two-in-three (66%) chance | medium | 1 | train |
519 | AR6_WGI | 205 | 22 | Using GMST instead of GSAT gives estimates of 770 GtCO 2 and 570 GtCO 2, respectively | medium | 1 | train |
520 | AR6_WGI | 209 | 1 | It is likely that there was a net anthropogenic forcing of 0.0 –0.3 Wm–2 in 1850 –1900 relative to 1750 | medium | 1 | train |
521 | AR6_WGI | 209 | 11 | Combining these different sources of evidence, we assess that from the period around 1750 to 1850–1900 there was a change in global temperature of around 0.1 [–0.1 to +0.3] °C (medium confidence), with an anthropogenic component in a likely range of 0.0°C–0.2°C | medium | 1 | train |
522 | AR6_WGI | 212 | 15 | Overall, tropical regions show earlier emergence of temperature changes than at higher latitudes | high | 2 | train |
523 | AR6_WGI | 227 | 7 | In summary, the observational coverage of ongoing changes to the climate system is improved at the time of AR6, relative to what was available for AR5 | high | 2 | train |
524 | AR6_WGI | 228 | 2 | Overall, the number, temporal resolution and chronological accuracy of paleoclimate reconstructions have increased since AR5, leading to improved understanding of climate system processes (or Earth system processes) | high | 2 | train |
525 | AR6_WGI | 228 | 28 | In summary, while the quantity, quality and diversity of climate system observations have grown since AR5, the loss or potential loss of several critical components of the observational network is also evident | high | 2 | train |
526 | AR6_WGI | 230 | 6 | In summary, the improvements in atmospheric reanalyses, and the greater number of years since the routine ingestion of satellite data began, relative to AR5, mean that there is increased confidence in using atmospheric reanalysis products alongside more standard observation-based datasets in AR6 | high | 2 | train |
527 | AR6_WGI | 231 | 10 | In summary, reanalyses have improved since AR5 and can increasingly be used as a line of evidence in assessments of the state and evolution of the climate system | high | 2 | train |
528 | AR6_WGI | 239 | 1 | Overall, we assess that increases in computing power and the broader availability of larger and more varied ensembles of model simulations have contributed to better estimations of uncertainty in projections of future change | high | 2 | train |
529 | AR6_WGI | 297 | 25 | The remainder is due to improved scientific understanding and changes in the assessment of aerosol forcing, which include decreases in concentration and improvement in its calculation | high | 2 | train |
530 | AR6_WGI | 298 | 24 | The total 20th century rise is estimated to be 0.17 [0.12 to 0.22] m. The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia | high | 2 | train |
531 | AR6_WGI | 298 | 26 | The average rate of sea level rise was 1.3 [0.6 to 2.1] mm yr–1 between 1901 and 1971, increasing to 1.9 [0.8 to 2.9] mm yr–1 between 1971 and 2006, and further increasing to 3.7 [3.2 to 4.2] mm yr–1 between 2006 and 2018 | high | 2 | train |
532 | AR6_WGI | 299 | 1 | Such warming causes seawater to expand, contributing to sea level rise.Ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90% of the energy accumulated between 1971 and 2010 | high | 2 | train |
533 | AR6_WGI | 299 | 5 | The observed average rate of heating of the climate system increased from 0.50 [0.32 to 0.69] W m–2 for the period 1971–2006 to 0.79 [0.52 to 1.06] W m–2 for the period 2006– 2018 | high | 2 | train |
534 | AR6_WGI | 299 | 6 | Ocean warming accounted for 91% of the heating in the climate system, with land warming, ice loss and atmospheric warming accounting for about 5%, 3% and 1%, respectively | high | 2 | train |
535 | AR6_WGI | 299 | 10 | The ocean has absorbed about 30% of the emitted anthropogenic carbon dioxide, causing ocean acidification.In 2019, atmospheric CO 2 concentrations were higher than at any time in at least 2 million years (high confidence), and concentrations of CH 4 and N 2O were higher than at any time in at least 800,000 years | very high | 3 | train |
536 | AR6_WGI | 299 | 11 | Since 1750, increases in CO 2 (47%) and CH 4 (156%) concentrations far exceed – and increases in N 2O (23%) are similar to – the natural multi-millennial changes between glacial and interglacial periods over at least the past 800,000 years | very high | 3 | train |
537 | AR6_WGI | 300 | 11 | In the Northern Hemisphere, 1983–2012 was likely the warmest 30-year period of the last 1400 years | medium | 1 | train |
538 | AR6_WGI | 300 | 12 | Global surface temperature has increased faster since 1970 than in any other 50-year period over at least the last 2000 years | high | 2 | train |
539 | AR6_WGI | 300 | 13 | Temperatures during the most recent decade (2011–2020) exceed those of the most recent multi-century warm period, around 6500 years ago [0.2°C to 1°C relative to 1850–1900] | medium | 1 | train |
540 | AR6_WGI | 300 | 14 | Prior to that, the next most recent warm period was about 125,000 years ago, when the multi-century temperature [0.5°C to 1.5°C relative to 1850–1900] overlaps the observations of the most recent decade | medium | 1 | train |
541 | AR6_WGI | 300 | 16 | There is very high confidence that maximum global mean sea level during the last interglacial period (129,000 to 116,000 years ago) was, for several thousand years, at least 5 m higher than present, and high confidence that it did not exceed 10 m above present.Global mean sea level has risen faster since 1900 than over any preceding century in at least the last 3000 years | high | 2 | train |
542 | AR6_WGI | 300 | 17 | The global ocean has warmed faster over the past century than since the end of the last deglacial transition (around 11,000 years ago) | medium | 1 | train |
543 | AR6_WGI | 300 | 18 | A long- term increase in surface open ocean pH occurred over the past 50 million years | high | 2 | train |
544 | AR6_WGI | 300 | 19 | However, surface open ocean pH as low as recent decades is unusual in the last 2 million years | medium | 1 | train |
545 | AR6_WGI | 302 | 4 | Relative to 1995–2014, the likely global mean sea level rise by 2100 is 0.28–0.55 m under the very low GHG emissions scenario (SSP1-1.9); 0.32–0.62 m under the low GHG emissions scenario (SSP1-2.6); 0.44–0.76 m under the intermediate GHG emissions scenario (SSP2-4.5); and 0.63–1.01 m under the very high GHG emissions scenario (SSP5-8.5); and by 2150 is 0.37–0.86 m under the very low scenario (SSP1- 1.9); 0.46–0.99 m under the low scenario (SSP1-2.6); 0.66–1.33 m under the intermediate scenario (SSP2- 4.5); and 0.98–1.88 m under the very high scenario (SSP5-8.5) | medium | 1 | train |
546 | AR6_WGI | 302 | 5 | Global mean sea level rise above the likely range – approaching 2 m by 2100 and 5 m by 2150 under a very high GHG emissions scenario (SSP5-8.5) | low | 0 | train |
547 | AR6_WGI | 306 | 9 | Present-day global concentrations of atmospheric carbon dioxide (CO 2) are at higher levels than at any time in at least the past two million years | high | 2 | train |
548 | AR6_WGI | 306 | 10 | Changes in ERF since the late 19th century are dominated by increases in concentrations of greenhouse gases and trends in aerosols; the net ERF is positive and changing at an increasing rate since the 1970s | medium | 1 | test |
549 | AR6_WGI | 306 | 12 | Solar activity since 1900 was high but not exceptional compared to the past 9000 years | high | 2 | train |
550 | AR6_WGI | 306 | 13 | The average magnitude and variability of volcanic aerosol forcing since 1900 have not been unusual compared to the past 2500 years | medium | 1 | train |
551 | AR6_WGI | 306 | 17 | These changes are larger than those between glacial and interglacial periods over the last 800,000 years for CO 2 and CH 4 and of comparable magnitude for N 2O | very high | 3 | train |
552 | AR6_WGI | 306 | 21 | Aerosol optical depth (AOD) has decreased since 2000 over Northern Hemisphere mid-latitudes and Southern Hemisphere mid-latitude continents, but increased over South Asia and East Africa | high | 2 | train |
553 | AR6_WGI | 306 | 25 | Stratospheric ozone has declined between 60°S and 60°N by 2.2% from the 1980s to 2014–2017 | high | 2 | train |
554 | AR6_WGI | 306 | 26 | Since the mid-20th century, tropospheric ozone has increased by 30–70% across the Northern Hemisphere | medium | 1 | train |
555 | AR6_WGI | 306 | 27 | Since the mid-1990s, free tropospheric ozone increases were 2–7% per decade in the northern mid-latitudes (high confidence), 2–12% per decade in the tropics (high confidence) and <5% per decade in southern mid-latitudes | medium | 1 | train |
556 | AR6_WGI | 306 | 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 | test |
557 | AR6_WGI | 306 | 33 | Over the past several decades, key indicators of the climate system are increasingly at levels unseen in centuries to millennia, and are changing at rates unprecedented in at least the last 2000 years | high | 2 | train |
558 | AR6_WGI | 306 | 34 | Temperatures as high as during the most recent decade (2011–2020) exceed the warmest centennial-scale range reconstructed for the present interglacial, around 6,500 years ago [0.2°C–1°C relative to 1850–1900] | medium | 1 | train |
559 | AR6_WGI | 306 | 35 | The next older warm period is the last interglacial when the multi-centennial temperature range about 125,000 years ago [0.5°C–1.5°C relative to 1850–1900] encompassed the recent decade values | medium | 1 | train |
560 | AR6_WGI | 306 | 40 | Over the last 50 years, observed GMST has increased at a rate unprecedented in at least the last 2000 years | high | 2 | train |
561 | AR6_WGI | 307 | 4 | In the Tropics, the upper troposphere has warmed faster than the near-surface since at least 2001, the period over which new observational techniques permit more robust quantification | medium | 1 | train |
562 | AR6_WGI | 307 | 8 | Global land precipitation has likely increased since 1950, with a faster increase since the 1980s | medium | 1 | train |
563 | AR6_WGI | 307 | 15 | Global monsoon precipitation has likely increased since the 1980s, mainly in the Northern Hemisphere | medium | 1 | train |
564 | AR6_WGI | 307 | 20 | Between 1979 and 2019, Arctic sea ice area has decreased in both summer and winter, with sea ice becoming younger, thinner and more dynamic | very high | 3 | train |
565 | AR6_WGI | 307 | 22 | Antarctic sea ice area has experienced little net change since 1979 | high | 2 | train |
566 | AR6_WGI | 307 | 24 | Reductions in spring snow cover extent have occurred across the Northern Hemisphere since at least 1978 | very high | 3 | train |
567 | AR6_WGI | 307 | 25 | With few exceptions, glaciers have retreated since the second half of the 19th century and have continued to retreat at increased rates since the 1990s (very high confidence); this behaviour is unprecedented in at least the last 2000 years | medium | 1 | train |
568 | AR6_WGI | 307 | 26 | Greenland Ice Sheet (GrIS) mass loss has increased substantially since 2000 | high | 2 | train |
569 | AR6_WGI | 307 | 27 | The Greenland Ice Sheet was smaller than at present during the Last Interglacial period (high confidence) and the mid-Holocene | high | 2 | train |
570 | AR6_WGI | 307 | 28 | The Antarctic Ice Sheet (AIS) lost mass between 1992 and 2020 (very high confidence), with an increasing rate of mass loss over this period | medium | 1 | train |
571 | AR6_WGI | 307 | 29 | Although permafrost persists in areas of the Northern Hemisphere where it was absent prior to 3000 years ago, increases in temperatures in the upper 30 m over the past three to four decades have been widespread | high | 2 | train |
572 | AR6_WGI | 307 | 32 | The average rate of sea level rise was 1.3 [0.6 to 2.1] mm yr –1 between 1901 and 1971, increasing to 1.9 [0.8 to 2.9] mm yr –1 between 1971 and 2006, and further increasing to 3.7 [3.2 to 4.2] mm yr –1 between 2006 and 2018 | high | 2 | test |
573 | AR6_WGI | 307 | 35 | Since 1971, it is virtually certain that global ocean heat content has increased for the upper (0–700 m) layer, very likely for the intermediate (700–2000 m) layer and likely below 2000 m, and is currently increasing faster than at any point since at least the last deglacial transition (18 to 11 thousand years ago) | medium | 1 | train |
574 | AR6_WGI | 307 | 37 | The Atlantic Meridional Overturning Circulation (AMOC) was relatively stable during the past 8000 years (medium confidence) but declined during the 20th century | low | 0 | train |
575 | AR6_WGI | 307 | 38 | Ocean pH has declined globally at the surface over the past four decades (virtually certain) and in all ocean basins in the ocean interior | high | 2 | train |
576 | AR6_WGI | 307 | 39 | A long-term increase in surface open ocean pH occurred over the past 50 million years (high confidence), and surface ocean pH as low as recent times is uncommon in the last 2 million years | medium | 1 | train |
577 | AR6_WGI | 308 | 1 | Oxygen minimum zones are expanding at many locations | high | 2 | train |
578 | AR6_WGI | 308 | 3 | The ranges of many marine organisms are shifting towards the poles and towards greater depths | high | 2 | train |
579 | AR6_WGI | 308 | 4 | This mismatch in responses across species means that the species composition of ecosystems is changing | medium | 1 | train |
580 | AR6_WGI | 308 | 5 | At multiple locations, various phenological metrics for marine organisms have changed in the last 50 years, with the nature of the changes varying with location and with species | high | 2 | train |
581 | AR6_WGI | 308 | 6 | In the last two decades, the concentration of phytoplankton at the base of the marine food web, as indexed by chlorophyll concentration, has shown weak and variable trends in low and mid-latitudes and an increase in high latitudes | medium | 1 | train |
582 | AR6_WGI | 308 | 7 | Global marine primary production decreased slightly from 1998–2018, with increasing production in the Arctic | medium | 1 | train |
583 | AR6_WGI | 308 | 9 | Over the last century, there have been increases in species turnover within many ecosystems | high | 2 | test |
584 | AR6_WGI | 308 | 10 | Over the past half century, climate zones have shifted poleward, accompanied by an increase in the length of the growing season in the Northern Hemisphere extratropics and an increase in the amplitude of the seasonal cycle of atmospheric CO 2 above 45°N | high | 2 | train |
585 | AR6_WGI | 308 | 11 | Since the early 1980s, there has been a global-scale increase in the greenness of the terrestrial surface | high | 2 | train |
586 | AR6_WGI | 308 | 13 | CO2 levels during the MPWP were similar to present for a sustained period, within a range of 360–420 ppm | medium | 1 | test |
587 | AR6_WGI | 308 | 14 | Relative to the present, GMST, GMSL and precipitation rate were all higher, the Northern Hemisphere latitudinal temperature gradient was lower, and major terrestrial biomes were shifted northward | very high | 3 | train |
588 | AR6_WGI | 308 | 22 | Both polar annular modes have exhibited strong positive trends toward increased zonality of mid-latitude circulation over multi-decadal periods, but these trends have not been sustained for the Northern Annular Mode since the early 1990s | high | 2 | train |
589 | AR6_WGI | 308 | 23 | For tropical ocean modes, a sustained shift beyond multi-centennial variability has not been observed for El Niño–Southern Oscillation | medium | 1 | train |
590 | AR6_WGI | 308 | 24 | Modes of decadal and multi-decadal variability over the Pacific and Atlantic oceans exhibit no significant trends over the period of observational records | high | 2 | train |
591 | AR6_WGI | 314 | 1 | To conclude, solar activity since the late 19th century was relatively high but not exceptional in the context of the past 9 kyr | high | 2 | train |
592 | AR6_WGI | 314 | 25 | However, the average magnitude and variability of SAOD and its associated volcanic aerosol forcing since 1900 are not unusual in the context of at least the past 2.5 kyr | medium | 1 | train |
593 | AR6_WGI | 315 | 13 | Based on boron and carbon isotope data, supported by other proxies (Hollis et al., 2019), atmospheric CO2 during the EECO (50 Ma) was between 1150 and 2500 ppm | medium | 1 | test |
594 | AR6_WGI | 316 | 6 | High-resolution sampling (about 1 sample per 3 kyr) with the boron-isotope proxy indicates mean CO 2 mixing ratios for the Marine Isotope Stage KM5c interglacial were 360–420 ppm | medium | 1 | train |
595 | AR6_WGI | 316 | 21 | Although ice core records present low-pass filtered time series due to gas diffusion and gradual bubble close- off in the snow layer over the ice sheet (Fourteau et al., 2020), the rate of increase since 1850 CE (about 125 ppm increase over about 170 years) is far greater than implied for any 170-year period by ice core records that cover the last 800 ka | very high | 3 | train |
596 | AR6_WGI | 319 | 15 | The last time CO 2 concentrations were similar to the present-day was over 2 Ma | high | 2 | train |
597 | AR6_WGI | 319 | 18 | Between 1750–2019 mixing ratios increased by 131.6 ± 2.9 ppm (47%), 1137 ± 10 ppb (156%), and 62 ± 6 ppb (23%), for CO 2, CH 4, and N 2O, respectively | very high | 3 | train |
598 | AR6_WGI | 323 | 29 | In summary, limited available isotopic evidence constrains the global tropospheric ozone increase to less than 40% between 1850 and 2005 | low | 0 | train |
599 | AR6_WGI | 323 | 30 | Based on sparse historical surface/low altitude data tropospheric ozone has increased since the mid-20th century by 30–70% across the NH | medium | 1 | train |
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