PhD, climate scientist @IPSL/LSCE, Paris Saclay; co-chair of @IPCC_CH WGI (#AR6). Tweets are my own. I like birds, books, e-bike commuting, tennis. Vegetarian.

France
Joined July 2009
Bonjour! Voici une présentation pour les francophones des principales conclusions du 6ème rapport d'évaluation du GIEC sur les bases physiques du changement climatique. ➡️🧵 (1/...)
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Future scenario-based climate simulations account for projected changes in solar irradiance and the long-term mean background forcing from volcanoes (in addition to contrasted human influence), but not for (unpredictable) individual volcanic eruptions. (57/...)
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Based on paleoclimate and historical evidence, it is likely that at least one large explosive volcanic eruption would occur during the 21st century. (58/...)
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A sequence of large explosive volcanic eruptions within decades has occurred in the past, causing substantial global and regional climate perturbations over several decades. Such events cannot be ruled out in the future. (59/...)
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By exploring possible volcanic futures under an intermediate emission scenario, it has been demonstrated that inclusion of time-varying volcanic forcing may enhance climate variability on annual to decadal timescales. (60/...)
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Clustered eruptions would have substantial impact upon the global surface temperature throughout this century. (61/...)
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For the near-term, the central estimate of crossing 1.5°C of global warming (for a 20-year period) occurs in the early 2030s, assuming no major volcanic eruption. (62/...)
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A factor that could substantially alter projections in the near-term would be the occurrence of a large explosive volcanic eruption, or even a decadal to multi-decadal sequence of small-to-moderate volcanic eruptions as witnessed since 2000 CE. (63/...)
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An eruption similar to Mount Pinatubo (1991) is expected to cause substantial northern hemisphere cooling, peaking between 0.1 and 0.4°C and lasting for 3 to 5 years. (64/...)
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Although temporary, close to pre-industrial temperatures could be experienced globally for a few years after a 1257 Samalas-sized eruption. (65/...)
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The central estimate of crossing 1.5°C of global warming (for a 20-year period) occurs in the early 2030s, assuming no major volcanic eruption. (66/...)
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A factor that could substantially alter projections in the near-term would be the occurrence of a large explosive volcanic eruption, or even a decadal to multi-decadal sequence of small-to-moderate volcanic eruptions as witnessed since 2000 CE. (67/...)
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In addition to effects on the water cycle described above, regional drought events may be enhanced by the occurrence of volcanic eruptions in addition to the effect of human-caused global warming. (68/...)
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A major eruption would reduce global precipitation, especially over land, for one to three years, alter the global monsoon circulation, modify extreme precipitation and change many climatic impact-drivers. (69/...)
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Considerable climate prediction skills can be attributed to volcanic eruptions. (70/...)
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Monitoring volcanic eruptions is of course critical for early warning systems, related to local and regional hazards, associated tsunamis, atmospheric transport of ashes and harmful gases... (71/...)
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Monitoring stratospheric effects of major eruptions is also crucial to assess stratospheric volcanic aerosols, and update near-term climate predictions, to inform risk management (72/...)
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This illustrates the role of natural drivers in modulating human-caused climate changes in the near-term and at regional scales, and why it is important to take into account the eventuality of major volcanic eruptions in planning for the full range of possible changes. (73/...)
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This thread has been prepared a few days after a violent eruption of Hunga Tonga, leading to widespread damage and urgent need for immediate aid, with intense ongoing scientific activities to assess from satellite data the potential implications of this eruption. END -
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