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Author Topic: Global Warming Would Stop Quickly After Emissions Go To Zero  (Read 49868 times)

John_the_Younger

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Re: Global Warming Would Stop Quickly After Emissions Go To Zero
« Reply #350 on: June 27, 2023, 07:12:57 PM »
The whole concept of 350.org (never a member, myself) is that the (CO2) blanket is too warm as it is - a thinner blanket is what the doctor calls for.  So, even when (I'm hopeful) we get to Net Zero emissions, required efforts remain to save future generations (and existing species). 

Analogy: the steam engine we're being pulled by is headed for a junction where straight ahead leads to a collapsed bridge (FOX news reports no problems) and the curved rail option is sharp and must be approached slowly to prevent a serious derailment (naysayers say the posted speed limit is unnecessarily slow, by an order of magnitude).  Right now the fireman and a brakeman are shoveling coal.  Not only must the brakeman do what he's supposed to do, the fireman needs to cool the flames.  All we've done so far is to get the second brakeman to put down his shovel.  The engineer (conductor), meanwhile, is fussing with payroll and job descriptions [inflation? employment statistics?], and is reviewing résumés.

kiwichick16

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Re: Global Warming Would Stop Quickly After Emissions Go To Zero
« Reply #351 on: July 16, 2023, 07:12:15 AM »
this paper suggests we have a problem Houston

https://www.nature.com/articles/s41598-020-75481-z

Sciguy

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Re: Global Warming Would Stop Quickly After Emissions Go To Zero
« Reply #352 on: July 16, 2023, 08:05:39 AM »
this paper suggests we have a problem Houston

https://www.nature.com/articles/s41598-020-75481-z

A study from 2020 based on one model. 

This study in 2022 based on many models found otherwise.

https://ui.adsabs.harvard.edu/abs/2022EGUGA..24.2539M/abstract

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Estimated effect of the permafrost carbon stability on the zero emissions commitment to climate change

MacDougall, Andrew H.
Abstract
Zero Emissions Commitment (ZEC), the expected change in global temperature following the cessation of anthropogenic greenhouse gas emissions has recently been assessed by the Zero Emissions Commitment Model Intercomparison Project (ZECMIP). ZECMIP concluded that the component of ZEC from CO2 emissions will likely be close to zero in the decades following the cessation of emissions. However, of the 18 Earth system models that participated in ZECMIP only two included a representation of the permafrost carbon feedback to climate change. To better assess the potential impact of permafrost carbon decay on ZEC a series of perturbed parameter experiments were conducted with an Earth system model of intermediate complexity. The experiment suggest that the permafrost carbon cycle feedback will directly add 0.06 [0.02 to 0.14]oC to the benchmark ZEC value assesses 50 years after 1000 PgC of CO2 has been emitted to the atmosphere. An additional 0.04 [0 to 0.06]oC is likely to been added relative to the benchmark ZEC value from the thaw-lag effect unaccounted for in the ZECMIP experiment design. Overall we assess that the permafrost carbon feedback is unlikely to change the assessment that ZEC is close to zero on decadal timescales, however the feedback is expected to become more important over the coming centuries.

kiwichick16

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Re: Global Warming Would Stop Quickly After Emissions Go To Zero
« Reply #353 on: July 16, 2023, 09:39:59 AM »
@  science guy  .... their conclusions are based on one experiment ...  and the last line says..." the feedback is expected to become more important over the coming centuries "

kassy

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Re: Global Warming Would Stop Quickly After Emissions Go To Zero
« Reply #354 on: July 16, 2023, 07:31:06 PM »
The permafrost has been a source instead of a sink for years. This will not change until it gets colder then the temperature that triggered that change which is about 1C over the global temperature baseline. The actual range of effects predicted varies so wildly we will have to wait and see. It might be limited by the way siberian permafrost deformes then again the melting will make lakes which might be really good at producing methane under certain conditions.

Anyway to stop this we should first get our emissions to as close to zero as we can and then compensate via various different methods for the rest including whatever the mix of emissions is that is escaping from the permafrost at that time (as energy builds in the Earth system it will get warmer, also see albedo loss and the added energy from fall out of cooling pollution).

The problem is basically the generic climate problem. Trigger these things and there is no way back.
Þetta minnismerki er til vitnis um að við vitum hvað er að gerast og hvað þarf að gera. Aðeins þú veist hvort við gerðum eitthvað.

Sciguy

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Re: Global Warming Would Stop Quickly After Emissions Go To Zero
« Reply #355 on: July 17, 2023, 07:42:45 AM »
The Arctic is still a carbon sink, although it could reach a tipping point and begin weakening between 2050 and 2080.

https://iopscience.iop.org/article/10.1088/1748-9326/acb226/meta

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Renato K Braghiere et al 2023 Environ. Res. Lett. 18 025008
Tipping point in North American Arctic-Boreal carbon sink persists in new generation Earth system models despite reduced uncertainty

Abstract
Estimating the impacts of climate change on the global carbon cycle relies on projections from Earth system models (ESMs). While ESMs currently project large warming in the high northern latitudes, the magnitude and sign of the future carbon balance of Arctic-Boreal ecosystems are highly uncertain. The new generation of increased complexity ESMs in the Intergovernmental Panel on Climate Change Sixth Assessment Report (IPCC AR6) is intended to improve future climate projections. Here, we benchmark the Coupled Model Intercomparison Project (CMIP) 5 and 6 (8 CMIP5 members and 12 CMIP6 members) with the International Land Model Benchmarking (ILAMB) tool over the region of NASA's Arctic-Boreal vulnerability experiment (ABoVE) in North America. We show that the projected average net biome production (NBP) in 2100 from CMIP6 is higher than that from CMIP5 in the ABoVE domain, despite the model spread being slightly narrower. Overall, CMIP6 shows better agreement with contemporary observed carbon cycle variables (photosynthesis, respiration, biomass) than CMIP5, except for soil carbon and turnover time. Although both CMIP ensemble members project the ABoVE domain will remain a carbon sink by the end of the 21st century, the sink strength in CMIP6 increases with CO2 emissions. CMIP5 and CMIP6 ensembles indicate a tipping point defined here as a negative inflection point in the NBP curve by 2050–2080 independently of the shared socioeconomic pathway (SSP) for CMIP6 or representative concentration pathway (RCP) for CMIP5. The model ensembles therefore suggest that, if the carbon sink strength keeps declining throughout the 21st century, the Arctic-Boreal ecosystems in North America may become a carbon source over the next century.

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Modeling if an Arctic-Boreal carbon cycle tipping point will occur is rather complex and dependent on a number of feedback loop interactions, but results indicate newer ESMs are generally better at capturing the present-day carbon cycle picture over the Arctic-Boreal ecosystems than were previous model versions. The exception to the general improvement in more recent ESMs is related to the representation of carbon in soils.

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Under high emissions scenarios, a relative strengthening of global land carbon–climate feedbacks leads the terrestrial biosphere to shift from a carbon sink to a carbon source at some point after 2100 in all of the CMIP5 ESMs (IPCC 2007, Tokarska et al 2016). Likewise, Koven et al (2022) evaluated land carbon fluxes globally from 5 CMIP6 members until 2300 and found that terrestrial ecosystems are projected to switch from being a net sink to either a neutral state or a net source of carbon depending on the model and the scenario used in the projections. Nevertheless, Koven et al (2022) highlight that land models qualitatively disagree in the spatial patterns, the timing, and the magnitudes of the carbon responses to climate change. Therefore, the diverse potential for global and regional carbon cycle dynamics to change sign under different scenarios highlights the continued need for improved comprehension of the major drivers of terrestrial carbon cycle dynamics.

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Nevertheless, both CMIP ensemble members across different carbon emission scenarios project a tipping point between 2050 and 2080. The carbon sink strength over the ABoVE domain starts to decrease during these years, indicating that sometime in the next century the North American Arctic-Boreal ecosystems will likely become a source of carbon to the atmosphere. This will amplify the local and global impacts of climate change already attributed to a local physical component, the permafrost (Natali et al 2019).

Sciguy

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Re: Global Warming Would Stop Quickly After Emissions Go To Zero
« Reply #356 on: July 17, 2023, 08:10:32 AM »
The Arctic Ocean carbon sink has been increasing as sea ice losses have increased.

https://www.authorea.com/doi/full/10.22541/essoar.168476524.42265823

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An assessment of CO2 uptake in the Arctic Ocean from 1985 to 2018

Sayaka Yasunaka, Manfredi Manizza, Jens Terhaar, Are Olsen, Ryohei Yamaguchi, Peter Landschützer, Eiji Watanabe, Dustin Carroll, Hanani Adiwara, Jens Daniel Müller, Judith Hauck

Abstract
As a contribution to the Regional Carbon Cycle Assessment and Processes phase 2 (RECCAP2) project, we present synthesized estimates of Arctic Ocean sea-air CO2 fluxes and their uncertainties from 8 surface ocean pCO2-observation products, 18 ocean biogeochemical hindcast and data assimilation models and 6 atmospheric inversions. For the period of 1985−2018, the Arctic Ocean was a net sink of CO2 of 116 ± 4 TgC yr−1 in the pCO2 products and 92 ± 30 TgC yr−1 in the models. The CO2 uptake peaks in late summer and early autumn, and is low in winter when sea ice inhibits sea-air fluxes. The long-term mean CO2 uptake in the Arctic Ocean is primarily caused by steady-state fluxes of natural carbon (70 ± 15 %), and enhanced by the atmospheric CO2 increase (19 ± 5 %) and climate change (11 ± 18 %). The annual mean CO2 uptake increased from 1985 to 2018 at a rate of 31 ±13 TgC yr−1dec-1 in the pCO2 products and 10 ± 4 TgC yr−1dec-1 in the models. Moreover, 77 ± 38 % of the trend in the net CO2 uptake over time is caused by climate change, primarily due to rapid sea ice loss in recent years. Both, the mean CO2 uptake and the trend, is substantially weaker in the atmospheric inversions. Uncertainties across all estimates are large, in the pCO2 products because of scarcity of observations and in the models because of missing processes.

Sciguy

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Re: Global Warming Would Stop Quickly After Emissions Go To Zero
« Reply #357 on: February 05, 2024, 03:11:14 AM »
This recent article (November 2023) explains the zero emissions commitment and the reason why the IPCC projects little to no warming after net zero greenhouse gas emissions are achieved.

https://www.frontiersin.org/journals/science/articles/10.3389/fsci.2023.1256273/full?utm_source=twitter&utm_medium=social&utm_content=editorial&utm_campaign=imp_fsci-nz_11-23_fsci_en_n-jour-focm

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Warming ends when carbon pollution stops
Michael E. Mann

Front. Sci., 14 November 2023
Volume 1 - 2023 | https://doi.org/10.3389/fsci.2023.1256273

A recent article in The Hill insisted that “scientists failed for decades to communicate” (1) the threat of climate change. The scientific paper on which the article was reporting did not really say that—it was instead providing a more nuanced discussion of sea level rise “tail risk”. But the irony here is that the opposite of what was asserted by the news article is arguably true. If anything, we scientists have failed to communicate the prospects for averting catastrophic warming.

In the days when I was working on my PhD, in the early 1990s, we were taught that the warming of the planet would persist for decades even if we suddenly stopped burning fossil fuels and emitting carbon into the atmosphere. This is due to what is known as “thermal inertia”—the slow, sluggish response of the oceans. Climate models showed that surface warming would continue for 30 years or more, as the oceans slowly continue to warm, even after carbon pollution ceases. This so-called “committed warming” would seem to render our efforts to avert disaster somewhat futile. Even if we turned off the metaphorical carbon faucet, the water level of warming would continue to rise. Extending the metaphor, that water would soon spill from our kitchen sink onto the kitchen floor. With apologies to Greta Thunberg, rather than burning, our house would instead be flooding.

But that picture is fundamentally incomplete—there is a “drain” too in the form of the ocean carbon cycle. That drain causes the water level, i.e., the planetary temperature, to stabilize. Through a somewhat fortuitous coincidence of nature, there are offsetting tendencies in ocean physics and ocean chemistry. The positive “thermal inertia” (the physics) is almost perfectly offset by a negative “carbon cycle inertia” (the chemistry). To be more specific, the rate at which the ocean surface tends to continue to warm up due to the carbon already emitted is nearly identical to the rate at which the oceans absorb and bury atmospheric carbon dioxide (CO2), lowering the atmospheric greenhouse effect and cooling the lower atmosphere and surface. The two effects essentially cancel each other out. And so, instead, we get an essentially flat temperature curve—the stable metaphorical water level—when human carbon emissions approach zero.

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This is hardly a minor technical matter. It fundamentally changes our sense of agency in averting disaster. It means our efforts to reduce carbon emissions have a direct and immediate impact. It is the reason we can meaningfully define a “carbon budget”—there is a fixed amount of fossil fuel we can afford to burn and stay below critical planetary temperature levels such as 1.5°C or 2.0°C. We can estimate that budget and work toward policies that can keep us collectively within it, at least in principle.

Old habits die hard, and some scientists have remained skeptical of this revised understanding. Indeed, I myself took several years to accept the paradigm-shifting implications of this finding. But this finding appears quite robust, having been affirmed by a solid body of work over the past decade. The current state of the science is adroitly summarized in a comprehensive new review “The Zero Emissions Commitment and climate stabilization” by a team of nearly two dozen experts on this research topic in the current Frontiers in Science Lead Article by Palazzo Corner et al. (4).

kiwichick16

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