Global Warming Would Stop Quickly After Emissions Go To Zero

[Sciguy]

A lot of people still assume that temperatures would continue to increase after emissions go to zero.  However, that's no longer what the science shows.

https://insideclimatenews.org/news/03012021/five-aspects-climate-change-2020/

Many Scientists Now Say Global Warming Could Stop Relatively Quickly After Emissions Go to Zero
That’s one of several recent conclusions about climate change that came more sharply into focus in 2020.
By Bob Berwyn
January 3, 2021

Some scientists punctuate their alarming warmings with hopeful messages because they know that the worst possible outcome is avoidable.

Recent research shows that stopping greenhouse gas emissions will break the vicious cycle of warming temperatures, melting ice, wildfires and rising sea levels faster than expected just a few years ago.

There is less warming in the pipeline than we thought, said Imperial College (London) climate scientist Joeri Rogelj, a lead author of the next major climate assessment from the Intergovernmental Panel on Climate Change.

“It is our best understanding that, if we bring down CO2 to net zero, the warming will level off. The climate will stabilize within a decade or two,” he said. “There will be very little to no additional warming. Our best estimate is zero.”

The widespread idea that decades, or even centuries, of additional warming are already baked into the system, as suggested by previous IPCC reports, were based on an “unfortunate misunderstanding of experiments done with climate models that never assumed zero emissions.”

Those models assumed that concentrations of greenhouse gases in the atmosphere would remain constant, that it would take centuries before they decline, said Penn State climate scientist Michael Mann, who discussed the shifting consensus last October during a segment of 60 Minutes on CBS.

The idea that global warming could stop relatively quickly after emissions go to zero was described as a “game-changing new scientific understanding” by Covering Climate Now, a collaboration of news organizations covering climate.

[vox_mundi]

Agriculture is responsible for 11% of all Greenhouse Gas emissions globally. Together with related emissions from changing land use and cutting down forests, it accounts for around 30% of GHG emissions globally.

How do they make that part of the pie disappear.

[The Walrus]

Agriculture is responsible for 11% of all Greenhouse Gas emissions globally. Together with related emissions from changing land use and cutting down forests, it accounts for around 30% of GHG emissions globally.

How do they make that part of the pie disappear.

The article was not about how emissions could go to zero, but the outcome of such action.

[wili]

Ken, that rosy estimate seems to be contradicted by these paragraphs form the same article:

Parts of the world economy may have been on pause during 2020, dampening greenhouse gas emissions for a while. But that didn’t slow the overall buildup of atmospheric carbon dioxide, which reached its highest level in millions of years.

If anything, research during the year showed global warming is accelerating. Symptoms of the fever include off-the-charts heat waves on land and in the oceans, and a hyperactive and destructive Atlantic hurricane season.

And through November, the last year was on pace to end up as either the hottest, or second-hottest on record for the planet, almost 1 degree Celsius above pre-industrial times

Sooo, if stopping emissions would immediately stop warming, then slowing down emissions should at least somewhat slow down warming, right? But that hasn't happened.

And if the the intended meaning is that the minute we stop emitting GHGs, we will immediately return to pre-industrial temperatures and atmospheric ghg levels....well, that's just absurd on the face of it, given that 90 some percent of warming and a good portion of the CO2 went into the oceans, which will start 'giving back' said gasses and heat if we ever stop emitting GHGs.

This also seems to ignore multiple feedbacks that have already started and that also interact with (feedback on) each other in a way that is difficult to impossible to accurately model...but not likely to be pretty.

But of course I'm all for ending emissions as soon as possible. But we will have then figure out ways to re-sequester at least some of the CO2, etc, if we want anything like a livable climate any time soon.

[El Cid]

Agriculture is responsible for 11% of all Greenhouse Gas emissions globally. Together with related emissions from changing land use and cutting down forests, it accounts for around 30% of GHG emissions globally.

How do they make that part of the pie disappear.

Regenerative agriculture can make the soil a net carbon sink

[KiwiGriff]

Recent research shows that stopping greenhouse gas emissions

Not going to happen in the next fifty years...
We seem to have solutions for energy generation and personal transport  that we may be able roll out over the coming decades if we can muster the political will.
That still leaves the emissions from.
Steel, Cement , Shipping, Air transport , Mining and Agriculture.
I doubt anyone alive today will live to see net zero.
Our efforts   will not be enough to  stop the amazon collapsing and much of the worlds permafrost melting out. Both feedback's that will result in increasing CO2 .

Magic thinking and hyping  mythical scenarios  is not going to solve climate change .

[crandles]

Sooo, if stopping emissions would immediately stop warming, then slowing down emissions should at least somewhat slow down warming, right? But that hasn't happened.

I don't think that is the correct interpretation. I see the article as saying if co2 levels stay at the same level, warming does continue for decades to hundreds of years (as ocean slowly gets into balance with atmosphere which has changed much more quickly) and this hasn't changed.

The new understanding is that if we get to net zero emissions then natural sinks will continue to soak up CO2 and so CO2 levels will then fall with continuing net zero emissions.

Meanwhile CO2 is this year is around 2.3ppm higher than last year a similar level to previous decade so we shouldn't expect a "somewhat slow[ed] down warming" nor has there been. So this doesn't contradict what is being said in the article.


I agree with other posts saying it will be difficult to cut emissions by 80% let alone 100%.

[The Walrus]

Sooo, if stopping emissions would immediately stop warming, then slowing down emissions should at least somewhat slow down warming, right? But that hasn't happened.

I don't think that is the correct interpretation. I see the article as saying if co2 levels stay at the same level, warming does continue for decades to hundreds of years (as ocean slowly gets into balance with atmosphere which has changed much more quickly) and this hasn't changed.

The new understanding is that if we get to net zero emissions then natural sinks will continue to soak up CO2 and so CO2 levels will then fall with continuing net zero emissions.

Meanwhile CO2 is this year is around 2.3ppm higher than last year a similar level to previous decade so we shouldn't expect a "somewhat slow[ed] down warming" nor has there been. So this doesn't contradict what is being said in the article.


I agree with other posts saying it will be difficult to cut emissions by 80% let alone 100%.

I think the interpretation was correct, based on the article:

“It is our best understanding that, if we bring down CO2 to net zero, the warming will level off. The climate will stabilize within a decade or two,” he said. “There will be very little to no additional warming. Our best estimate is zero.

The widespread idea that decades, or even centuries, of additional warming are already baked into the system, as suggested by previous IPCC reports, were based on an “unfortunate misunderstanding of experiments done with climate models that never assumed zero emissions.”

[beachykeen]

That still leaves the emissions from.
Steel, Cement , Shipping, Air transport , Mining and Agriculture.
I doubt anyone alive today will live to see net zero.

And, I have yet to see anyone detail how the military will deal with not having these produced at the rate they can be with fossils until we have fully electrified all of the economy.  No military is going to give up it's industrial backing.  Production /volume/ is a strategic asset, not just the ability to ramp up production.

As long as humans are competitive, those fossils won't stay in the ground. IMO.

[kassy]

This is the science article Rogelj is referring too:

Is there warming in the pipeline? A multi-model analysis of the Zero Emissions Commitment from CO2

https://bg.copernicus.org/articles/17/2987/2020/

[The Walrus]

This is the science article Rogelj is referring too:

Is there warming in the pipeline? A multi-model analysis of the Zero Emissions Commitment from CO2

https://bg.copernicus.org/articles/17/2987/2020/

"Overall, the most likely value of ZEC on multi-decadal timescales is close to zero, consistent with previous model experiments and simple theory."

[kassy]

“It is our best understanding that, if we bring down CO2 to net zero, the warming will level off. The climate will stabilize within a decade or two,” he said. “There will be very little to no additional warming. Our best estimate is zero.”

The widespread idea that decades, or even centuries, of additional warming are already baked into the system, as suggested by previous IPCC reports, were based on an “unfortunate misunderstanding of experiments done with climate models that never assumed zero emissions.”

So they fight models with models.

What would you learn from doing a model with zero emissions vs one with ongoing emissions?

At the point you actually go net negative or you have reached the top the warming will bottom out in the atmospheric forcing push which then some time later translate into a max push with respect to the Earth system.

They still skip over some things.

Before we go negative which will take a few decades (and that is being optimistic) we will trigger such events as the loss of Arctic ice (somewhere between this decade and the 2040ies) and possibly we will murder the Amazon. If we plug for the 40ies that is two more decades of melting Siberia and all that comes out of there. Maybe Siberia is minute wrt humanities total output but you still have to achieve our net negative + compensate for what we triggered.

And we might very well trigger an Antarctic response that can not be stopped on any conceivable time scale (IPCC words) before we get there.

And that all depends on when we go overall carbon negative.

With hindsight we should define losing ASI as dangerous climate change and act on that but that is already too late.

Maybe the question is what we have to do to actually go carbon negative...

[Tom_Mazanec]

Wouldn't the thermal inertia of the oceans keep heating the atmosphere for may years, even decades after GHG emissions ceased?

[harpy]

I just want to point out that OP literally doesn't even link actual science in the post.

Nice one OP, link a news article and assert "the science".

@ken Feldmen,  How about a real scientific reference?

I have faith in you Ken, just look around and find some actual science, I look forward to your post!~ 

[kassy]

It was rather annoying that the article linked to the twitter account and not the paper.

The paper is in post #9.

And there is more but i will put that in another post.

[crandles]

Wouldn't the thermal inertia of the oceans keep heating the atmosphere for may years, even decades after GHG emissions ceased?

Depends what you assume.

Climate models generally have GHG levels as inputs not emissions.

If ghg levels are held steady then atmosphere has warmed but oceans haven't yet warmed up to match and as ocean warms up then that further warms the atmosphere. This can take hundreds of years to fully get in balance but most of effect is in first several decades.

If we go to zero emissions and keep at that then oceans keep overturning and new water can take up more CO2 so GHG levels fall. This cools the atmosphere which means much less time for oceans and atmosphere to get in balance because the ocean has already done a lot of the warming to get more into balance with where the atmosphere was 20 years ago.

If we just cut emissions by half then the sinks will decline but not disappear so GHG will continue to rise and the situation is worse than holding GHG level.

Pandemic may have cut short term pollution a lot but CO2 levels have continued to rise at pretty much same rate as last decade.

[kassy]

The linked article explains it a lot better.

https://www.cjr.org/covering_climate_now/michael-mann-60-minutes-emissions-warming.php

Until recently, Mann explained in The Guardian, scientists believed the climate system—a catch-all term for the interaction among the Earth’s atmosphere, oceans, and other parts of the biosphere—carried a long lag effect. This lag effect was mainly a function of carbon dioxide remaining in the atmosphere and trapping heat for many decades after being emitted. So, even if humanity halted all CO2 emissions overnight, average global temperatures would continue to rise for 25 to 30 years, while also driving more intense heat waves, droughts, and other climate impacts. Halting emissions will take at least twenty years, under the best of circumstances, and so humanity was likely locked in to at least 50 more years of rising temperatures and impacts.

Research over the past ten years, however, has revised this vision of the climate system. Scientists used to “treat carbon dioxide in the atmosphere as if it was a simple control knob that you turn up” and temperatures climb accordingly, “but in the real world we now know that’s not what happens,” Mann said. Instead, if humans “stop emitting carbon right now … the oceans start to take up carbon more rapidly.” The actual lag effect between halting CO2 emissions and halting temperature rise, then, is not 25 to 30 years but, per Mann, “more like three to five years.”

But that is the modelling part.

Here is some new research from last year:

Some new research with troubling consequences:

Ocean uptake of CO2 could drop as carbon emissions are cut

Volcanic eruptions and human-caused changes to the atmosphere strongly influence the rate at which the ocean absorbs carbon dioxide, says a new study. The ocean is so sensitive to changes such as declining greenhouse gas emissions that it immediately responds by taking up less carbon dioxide.

...

"We didn't realize until we did this work that these external forcings, like changes in the growth of atmospheric carbon dioxide, dominate the variability in the global ocean on year-to-year timescales. That's a real surprise," said lead author Galen McKinley, a carbon cycle scientist at Columbia University's Lamont-Doherty Earth Observatory. "As we reduce our emissions and the growth rate of atmospheric carbon dioxide slows down, it's important to realize that the ocean carbon sink will respond by slowing down."

The paper, published today in the journal AGU Advances, largely resolves the uncertainty about what caused the ocean to take up varying amounts of carbon over the last 30 years. The findings will enable more accurate measurements and projections of how much the planet might warm, and how much the ocean might offset climate change in the future.

...

McKinley cautions that as global emissions are cut, there will be an interim phase where the ocean carbon sink will slow down and not offset climate change as much as in the past. That extra carbon dioxide will remain in the atmosphere and contribute to additional warming, which may surprise some people, she said.
https://www.eurekalert.org/pub_releases/2020-06/eiac-ouo060320.php

Paper:
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019AV000149

See link for full version.
Not sure that they modelled that correctly. Then again it is hard to model what you see less like negative emissions or changes beyond ´ice age earth´ since that is where most of our knowledge comes from.

In short, this game-changing new scientific understanding suggests that humanity can turn down the heat almost immediately by slashing heat-trapping emissions. “Our destiny is determined by our behavior,” said Mann, who finds that information “empowering.”

All that says is that when you go carbon negative you start impacting the heat trapping emissions. I think we knew that.

The whole thing nobody mentions is all the damage done on the way there.

To prevent a catastrophic rise in global temperature, humanity must cut emissions in half by 2030, Mann said, citing 2018’s landmark report by the UN’s Intergovernmental Panel on Climate Change. That will require a rate of change “unprecedented” in human history

So lets say we make that goal then we are still on target to lose the Arctic ice.
Most reefs will have given up by then etc.

It is nice to know we can fix it when we get around to it but aren´t we behind schedule anyway?

[kassy]

And this also fits here:

Study finds we’re already committed to more global warming—sort of

Someday, humans will get it together and dramatically reduce greenhouse gas emissions. But—not to fact check your daydreams too strictly here—how exactly will global temperatures respond to that day? This is a question climate science has long worked to answer, although devils in the details have led to some confusion.

A new study led by Nanjing University’s Chen Zhou tracks down another devil and puts it on display. Research has increasingly shown that it’s not just the planet’s average surface temperature that matters for tracking warming, but the spatial pattern of those temperatures. That can be important for calculating things like the climate’s sensitivity to greenhouse gases, but it hasn’t been accounted for in some methods of estimating how emissions cuts affect warming.

Seeing a pattern
This “pattern effect” of warming in different areas of the globe influences the way the planet sheds heat back to space. For example, if warming is a little stronger in the western equatorial Pacific Ocean—which it has been—that region is better at producing sunlight-reflecting cloud cover and releasing heat upward. If you assume the warming is occurring evenly around the world, you will miss that slightly offsetting behavior.

...

Calculations of the warming that we’re already committed to also depend critically on assumptions about what our future emissions will look like—a major source of confusion. The scenario used in this paper is one where we reduce emissions enough to simply maintain current greenhouse gas concentrations.

With that in mind, the results show that accounting for the pattern effect should increase committed warming. For concentrations stabilizing at 2020 levels, if we wait centuries for temperatures to equilibrate, total warming since pre-Industrial times grows from about 1.3°C to 2.3°C. (We have so far experienced about 1.1°C warming.)

An alternate version of this scenario allows short-lived gases and particulate matter to fade out; here, the ultimate warming grows from 1.6°C to 2.8°C. Restricting this very long-term view to just the year 2100, warming grows from 1.3°C to 1.8°C when accounting for the pattern effect.

The exact numbers aren’t really the point here—the researchers note that using a different dataset for past ocean temperatures causes the differences to shrink. It's the general finding—the existence of the pattern effect implies more committed warming—that's potentially important. It could mean that if you really want to permanently limit warming to a certain goal, like 1.5°C or 2°C, you need to err on the side of even lower emissions (or plan on actively removing more CO2 later on).

https://arstechnica.com/science/2021/01/study-finds-were-already-committed-to-more-global-warming-sort-of/

[Sciguy]

This is the science article Rogelj is referring too:

Is there warming in the pipeline? A multi-model analysis of the Zero Emissions Commitment from CO2

https://bg.copernicus.org/articles/17/2987/2020/

Kassy,

Thanks for posting the link to the science study.  I apologize for not including it in my original post.

Here's the abstract and some supporting excerpts:

MacDougall, A. H., Frölicher, T. L., Jones, C. D., Rogelj, J., Matthews, H. D., Zickfeld, K., Arora, V. K., Barrett, N. J., Brovkin, V., Burger, F. A., Eby, M., Eliseev, A. V., Hajima, T., Holden, P. B., Jeltsch-Thömmes, A., Koven, C., Mengis, N., Menviel, L., Michou, M., Mokhov, I. I., Oka, A., Schwinger, J., Séférian, R., Shaffer, G., Sokolov, A., Tachiiri, K., Tjiputra , J., Wiltshire, A., and Ziehn, T.: Is there warming in the pipeline? A multi-model analysis of the Zero Emissions Commitment from CO2, Biogeosciences, 17, 2987–3016, https://doi.org/10.5194/bg-17-2987-2020, 2020.

Abstract
Back to top

The Zero Emissions Commitment (ZEC) is the change in global mean temperature expected to occur following the cessation of net CO2 emissions and as such is a critical parameter for calculating the remaining carbon budget. The Zero Emissions Commitment Model Intercomparison Project (ZECMIP) was established to gain a better understanding of the potential magnitude and sign of ZEC, in addition to the processes that underlie this metric. A total of 18 Earth system models of both full and intermediate complexity participated in ZECMIP. All models conducted an experiment where atmospheric CO2 concentration increases exponentially until 1000 PgC has been emitted. Thereafter emissions are set to zero and models are configured to allow free evolution of atmospheric CO2 concentration. Many models conducted additional second-priority simulations with different cumulative emission totals and an alternative idealized emissions pathway with a gradual transition to zero emissions. The inter-model range of ZEC 50 years after emissions cease for the 1000 PgC experiment is −0.36 to 0.29 ∘C, with a model ensemble mean of −0.07 ∘C, median of −0.05 ∘C, and standard deviation of 0.19 ∘C. Models exhibit a wide variety of behaviours after emissions cease, with some models continuing to warm for decades to millennia and others cooling substantially. Analysis shows that both the carbon uptake by the ocean and the terrestrial biosphere are important for counteracting the warming effect from the reduction in ocean heat uptake in the decades after emissions cease. This warming effect is difficult to constrain due to high uncertainty in the efficacy of ocean heat uptake. Overall, the most likely value of ZEC on multi-decadal timescales is close to zero, consistent with previous model experiments and simple theory.

The analysis here has shown that across models decadal-scale ZEC is poorly correlated to other metrics of climate warming, such as TCR and ECS, though relationships may exist within model frameworks (Fig. 12). However, the three factors that drive ZEC, ocean heat uptake, ocean carbon uptake, and net land carbon flux correlate relatively well to their states before emissions cease. Thus, it may be useful to conceptualize ZEC as a function of these three components each evolving in their own way in reaction to the cessation of emissions. Ocean heat uptake evolves due to changes in ocean dynamics (e.g. Frölicher et al., 2015) as well as the complex feedbacks that give rise to changes in ocean heat uptake efficacy (Winton et al., 2010). Ocean carbon uptake evolution is affected by ocean dynamics, changes to ocean biogeochemistry, and changes in atmosphere–ocean CO2 chemical disequilibrium, where the latter is also influenced by land carbon fluxes (e.g. Sarmiento and Gruber, 2006). The response of the land biosphere to cessation of emissions is expected to be complex with contributions from the response of photosynthesis to declining atmospheric CO2 concentration, a continuation of enhanced soil respiration (e.g. Jenkinson et al., 1991), and release of carbon from permafrost soils (Schuur et al., 2015), among other factors. Investigating the evolution of the three components in detail may be a valuable avenue of future analysis. Similarly, given their clearer relationships to the state of the Earth system before emissions cease, focusing on the three components independently may prove useful for building a framework to place emergent constraints on ZEC. Future work will explore evaluation opportunities by assessing relationships between these quantities in the idealized 1 % simulation and values at the end of the historical simulations up to present day.

Our analysis has suggested that the efficacy of ocean heat uptake is crucial for determining the temperature effect from ocean heat uptake following cessation of emissions. Efficacy itself is generated by spatial patterns in ocean heat uptake and shortwave cloud feedback processes (Rose et al., 2014; Andrews et al., 2015). Thus, evaluating how these processes and feedbacks evolve after emissions cease is crucial for better understanding ZEC. As the spatially resolved outputs for ZECMIP are now available (see Data availability at the end of the paper), evaluating such feedbacks presents a promising avenue for future research.

Here we have analysed model output from the 18 models that participated in ZECMIP. We have found that the inter-model range of ZEC 50 years after emissions cease for the A1 (1 % to 1000 PgC) experiment is −0.36 to 0.29 ∘C, with a model ensemble mean of −0.07 ∘C, median of −0.05 ∘C, and standard deviation of 0.19 ∘C. Models show a range of temperature evolution after emissions cease from continued warming for centuries to substantial cooling. All models agree that, following cessation of CO2 emissions, the atmospheric CO2 concentration will decline. Comparison between experiments with a sudden cessation of emissions and a gradual reduction in emissions show that long-term temperature change is independent of the pathway of emissions. However, in experiments with a gradual reduction in emissions, a mixture of TCRE and ZEC effects occur as the rate of emissions declines. As the rate of emission reduction in these idealized experiments is similar to that in stringent mitigation scenarios, a similar pattern may emerge if deep emission cuts commence.

Overall, the most likely value of ZEC on decadal timescales is assessed to be close to zero, consistent with prior work. However, substantial continued warming for decades or centuries following cessation of emissions is a feature of a minority of the assessed models and thus cannot be ruled out purely on the basis of models.

[El Cid]

Once we lose all the summer ice on the Arctic shan't we have such a change in albedo that would result in much more solar energy to enter the Earth system and thereby keeping it warmer even if we cut all Co2 emissions?

Meaning that we have a system change that can not simply be undone even by going to zero?

[Sciguy]

Once we lose all the summer ice on the Arctic shan't we have such a change in albedo that would result in much more solar energy to enter the Earth system and thereby keeping it warmer even if we cut all Co2 emissions?

Meaning that we have a system change that can not simply be undone even by going to zero?

A recent study calculated that the complete loss of Arctic Sea ice would raise global temperatures by an addition 0.19C over the assumed 1.5C of warming that caused the loss.

https://www.nature.com/articles/s41467-020-18934-3

Wunderling, N., Willeit, M., Donges, J.F. et al. Global warming due to loss of large ice masses and Arctic summer sea ice. Nat Commun 11, 5177 (2020). https://doi.org/10.1038/s41467-020-18934-3

27 October 2020

Global warming due to loss of large ice masses and Arctic summer sea ice

Abstract

Several large-scale cryosphere elements such as the Arctic summer sea ice, the mountain glaciers, the Greenland and West Antarctic Ice Sheet have changed substantially during the last century due to anthropogenic global warming. However, the impacts of their possible future disintegration on global mean temperature (GMT) and climate feedbacks have not yet been comprehensively evaluated. Here, we quantify this response using an Earth system model of intermediate complexity. Overall, we find a median additional global warming of 0.43 °C (interquartile range: 0.39−0.46 °C) at a CO2 concentration of 400 ppm. Most of this response (55%) is caused by albedo changes, but lapse rate together with water vapour (30%) and cloud feedbacks (15%) also contribute significantly. While a decay of the ice sheets would occur on centennial to millennial time scales, the Arctic might become ice-free during summer within the 21st century. Our findings imply an additional increase of the GMT on intermediate to long time scales.

With CLIMBER-2, we are able to distinguish between the respective cryosphere elements and can compute the additional warming resulting from each of these (Fig. 2). The additional warmings are 0.19 °C (0.16–0.21 °C) for the Arctic summer sea ice, 0.13 °C (0.12–0.14 °C) for GIS, 0.08 °C (0.07–0.09 °C) for mountain glaciers and 0.05 °C (0.04–0.06 °C) for WAIS, where the values in brackets indicate the interquartile range and the main value represents the median. If all four elements would disintegrate, the additional warming is the sum of all four individual warmings resulting in 0.43 °C (0.39–0.46 °C) (thick dark red line in the Fig. 2). Our results regarding the amount of warming are of comparable magnitude to previous efforts computed for late Pliocene realisations (PRISM) of the ice sheets40,41. Both studies show a pronounced warming in the proximity of the locations where ice is removed, which is in good agreement with our results (see Fig. 1 and Supplementary Fig. 2). The disintegration of all elements at the same time can very closely be approximated by the sum of single elements disintegrated indicating that their effects on GMT add up linearly. This can be found in Fig. 3, where we also show the warming for CO2 concentrations from 280 to 700 ppm. Fig. 2 highlights the additional warming of 1.5 °C above pre-industrial.

Warming from the Arctic summer sea ice

We obtain that the warming results are independent from the CO2 concentration forcing between 280 and 700 ppm apart from the Arctic summer sea ice (see Fig. 3a), which shows a decreasing additional warming for higher CO2 concentrations (Fig 4). This can, in turn, be explained: In CLIMBER-2 simulations we find, with increasing prescribed CO2 concentrations corresponding to increasing GMT, that the Arctic summer sea ice area declines in a linear way, which was also found in observational records42 and in GCM simulations9. For a CO2 concentration of 400 ppm corresponding to 1.5 °C in CLIMBER-2 above pre-industrial GMT levels, the additional warming is 0.19 °C (0.16–0.21 °C). The actual minimal sea ice cover observed by NERSC (Nansen Environmental & Remote Sensing Center) as an average area from 1979 to 2006 is on the order of 5.5–6.5 × 106 km2 which would correspond to a warming of approximately 0.15 °C in our simulations (see Fig. 4). In Supplementary Fig. 3, we show the sea ice area over the course of 1 year for the control and the perturbed run.

[WildFit]

I think that alone the fact that this non-sense theory (nice word for it) is discussed in serious over 19 posts before thisone is kind of proof that something's wrong. To discuss this is like starting to discuss any obstruse theory that diverts from important matters and splits society where joint forces would be needed.

At least such threads should NOT appear under the undread posts every day because I'm sure that I'm not the only one who's HBR spikes on a regular basis over such non-sense.

[Sciguy]

It's important to note that the IPCC projects that the Arctic Ocean would see substantially fewer summers with an ice free Arctic with 1.5C global warming then with 2C.  This is from the special report on 1.5C, Global Warming of 1.5 ºC, produced by the IPCC in 2018.

https://www.ipcc.ch/sr15/chapter/chapter-3/

The probability of a sea-ice-free Arctic Ocean during summer is substantially higher at 2°C compared to 1.5°C of global warming (medium confidence). Model simulations suggest that at least one sea-ice-free Arctic summer is expected every 10 years for global warming of 2°C, with the frequency decreasing to one sea-ice-free Arctic summer every 100 years under 1.5°C (medium confidence). An intermediate temperature overshoot will have no long- term consequences for Arctic sea ice coverage, and hysteresis is not expected (high confidence). {3.3.8, 3.4.4.7}

...However, the modelled sea ice loss in most CMIP5 models is much smaller than observed losses. Compared to observations, the simulations are less sensitive to both global mean temperature rise (Rosenblum and Eisenman, 2017) and anthropogenic CO2 emissions (Notz and Stroeve, 2016). This mismatch between the observed and modelled sensitivity of Arctic sea ice implies that the multi-model-mean responses of future sea ice evolution probably underestimates the sea ice loss for a given amount of global warming. To address this issue, studies estimating the future evolution of Arctic sea ice tend to bias correct the model simulations based on the observed evolution of Arctic sea ice in response to global warming. Based on such bias correction, pre-AR5 and post-AR5 studies generally agree that for 1.5°C of global warming relative to pre-industrial levels, the Arctic Ocean will maintain a sea ice cover throughout summer in most years (Collins et al., 2013; Notz and Stroeve, 2016; Screen and Williamson, 2017; Jahn, 2018; Niederdrenk and Notz, 2018; Sigmond et al., 2018). For 2°C of global warming, chances of a sea ice-free Arctic during summer are substantially higher (Screen and Williamson, 2017; Jahn, 2018; Niederdrenk and Notz, 2018; Screen et al., 2018; Sigmond et al., 2018)
.

That means that if we can achieve zero emissions in the next few decades and keep the global warming to 1.5C, we haven't locked in the additional 0.19C of warming from losing the remaining sea ice in the Arctic. 

With the energy transition well underway, we have a realistic chance of achieving zero emissions within the lifetimes of most people reading these posts.

[Tor Bejnar]

Per ASIF's recent post,

•   2020 was 0.6°C warmer than the standard 1981-2010 reference period and around 1.25°C above the 1850-1900 pre-industrial period"

So, we went from first reaching about 1.0° above to having a second 1.25° above in 6 years (not yet averaging 1.25° above, yet).  I'm not saying we'll get to 1.5°  in 6 more years, but I wouldn't bet against getting there by the end of 2030 and staying there by 2035.  Electric vehicle adoption and coal-fired electricity generation shut downs will certainly put a dent in the increases.  Will it approach being enough? I doubt it.  All car sales would have to be EVs after 2025 to do their part ...

[El Cid]

1,5 C? Very funny. We shall not stop there for sure.

https://data.giss.nasa.gov/gistemp/maps/index.html

2015-20 was 0,29 C above 2005-10
2005-10 was 0,22 C above 1995-2000
1995-2000 was 0,15 C above 1985-95

The picture is clear. By 2030 we will hit 1,5 C and then, sky is the limit.

In 2030 Electricity/heating is still going to be a major Co2 emitter (Chinese, Indian coal, globally natgas). Cars will also be still mostly gas/diesel. Agriculture and industry will change only slowly. So emissions will be not much lower than now.

By 2050 we will be at 1/3-1/5 of emissions as now, but still positive. This means that we will hit 1,5C by 2030 and I guess 1,7-1,9 C by 2050. We might only be slightly above 2 C by 2100.

[kassy]

I think that alone the fact that this non-sense theory (nice word for it) is discussed in serious over 19 posts before thisone is kind of proof that something's wrong. To discuss this is like starting to discuss any obstruse theory that diverts from important matters and splits society where joint forces would be needed.

I would not call it a non sense theory since it is one actually pursued in science. These models are one way we try to make sense of things.

The whole what should society do is another thing for another thread.

[harpy]

https://bg.copernicus.org/articles/17/2987/2020/

The study is, by the authors own admission, not even complete.  The title of this thread should read "preliminary modeling of a wishful thinking scenario indicates interesting theoretical results, but is not yet complete and inconclusive"

The present iteration of ZECMIP aims to answer part
of this question by examining the temperature response in
idealized CO2-only climate model experiments. To answer
the question in full, the behaviour of non-CO2 greenhouse
gases, aerosols, and land use change must be accounted for
https://doi.org/10.5194/bg-17-2987-2020 Biogeosciences, 17, 2987–3016, 2020
2990 A. H. MacDougall et al.: Zero Emissions Commitment
in a consistent way. Such efforts will be the focus of future
iterations of ZECMIP.

[Hefaistos]

Tor and El Cid:
You seem to make calculations where forcings are linearly related to emissions, or to concentrations of GHGs in the atmosphere.
However, forcings from CO2 are logarithmic.

"The relationship between carbon dioxide and radiative forcing is logarithmic, at concentrations up to around eight times the current value, and thus increased concentrations have a progressively smaller warming effect."

Thus, with flat emissions, the forcings will slowly decline. The decay function for CO2 is central for the argument.



https://en.wikipedia.org/wiki/Radiative_forcing

[El Cid]

Tor and El Cid:
You seem to make calculations where forcings are linearly related to emissions, or to concentrations of GHGs in the atmosphere.
However, forcings from CO2 are logarithmic.

Forcing from Co2 LEVELS are logarithmic. As Co2 atmospheric lifetime is many many years, therefore it seems to me a near certainity that (as shown in the above post) we will see at least 0,3 C warming in the 2020s. Since we are 1,1-1,3 C above baseline (depending on its definition) we will hit 1,5 C by 2030. And even then, Co2 levels will continue to increase and there are some longer term effects from previous years. So, I do not see how we would stay below 1,5C.

[gerontocrat]

Is there not research indicating that the key is energy imbalance, and even if Global warming stopped how long before the energy imbalance returned to zero?
Is there not also a question of unhelpful changes to land and ocean carbon sinks, including some sinks becoming carbon emitters?

And anyway, if they are right we will just have to rely on all the other stuff humankind does to continue to successfully trash the planet.

[crandles]

Is there not research indicating that the key is energy imbalance, and even if Global warming stopped how long before the energy imbalance returned to zero?
Is there not also a question of unhelpful changes to land and ocean carbon sinks, including some sinks becoming carbon emitters?

And anyway, if they are right we will just have to rely on all the other stuff humankind does to continue to successfully trash the planet.

>unhelpful changes to land and ocean carbon sinks
Indeed.

With land, if the CO2 stops going up, there isn't much inertia in the system. Tree live a long time but if atmospheric levels of CO2 are not going up why would trees continue to take up more? I believe land sinks would fall to practically nil over just 5 years or so.

However the ocean is a bigger sink than land. Surface water gets into balance with atmosphere in a few months so this sink also disappears quickly. However with 1000 year overturning circulation new water comes to surface which for next 500-1000 years has low levels of dissolved CO2. So there is a much bigger difference between CO2 it has dissolved and the equilibrium level compared to surface waters which were in equilibrium at last years level of atmospheric CO2.

So this part of the sinks remains for quite some time even if other parts of the sinks should be expected to disappear quickly. Temperature rises do of course cause new sources but I believe I would suggest that so far these new sources have been small compared to the sinks. Yes there is some risk here that while these new sources may be small they might grow and continue for a long period unless the temperature goes down quite markedly soon.

Anyway if we get our emissions to net zero then I think the conclusion that CO2 levels will fall will be fairly robust.

If we struggle to reduce our net emissions to 20% of current levels then it will be much less clear whether there will be a (fall or) short term stabilisation of CO2 levels.

Unlikely to be adequate as an eventual target, but it might buy more time to work out how to do further cuts in net emissions.

80% cut in net emissions is a very tough target to reach let alone 100% but anything that helps should be welcomed rather than dismissing as non-sense because we prefer a "we're all doomed" commentary.

[KiwiGriff]

There is a new post on this subject over at ATTP.
https://andthentheresphysics.wordpress.com/2021/01/08/warming-commitments/

[El Cid]

There is a new post on this subject over at ATTP.
https://andthentheresphysics.wordpress.com/2021/01/08/warming-commitments/

Good article!

Makes me remember the vulgar version of the Pareto rule. 20% of the effort gets you 80% of the way. We MIGHT be able to reduce emissions very much, but some will very likely remain for quite a long time, thereby keeping Co2 LEVELS at least steady (if not still rising slowly), making the globe warmer and warmer...

[Richard Rathbone]

Is there not research indicating that the key is energy imbalance, and even if Global warming stopped how long before the energy imbalance returned to zero?
Is there not also a question of unhelpful changes to land and ocean carbon sinks, including some sinks becoming carbon emitters?

And anyway, if they are right we will just have to rely on all the other stuff humankind does to continue to successfully trash the planet.

It all depends on what you mean by warming.

If you mean temperature greater than it would have been without anthropogenic interference, there's hundreds of thousands of years, multiple ice age cycles, of that.  (it requires negative emissions to drive warming in that sense to zero on a shorter timescale)

If you mean the anthropogenic effect increasing, then there are all sorts of factors in play pulling in opposite directions and this sort of research is needed to evaluate them. It says temperature stops going up at the same time as emissions hit zero (central estimate, it might be a bit earlier or it might be a bit later, but with a rather smaller error margin than there was previously). The global energy imbalance is a way of measuring warming in this sense. If its zero, the temperature isn't changing any more.

There are caveats to this. ZEC=0 has slightly different implications to GEI=0 due to ice sheets. GEI=0 only implies dT/dt=0 after the ice sheets have stabilised, but it does imply they will stabilise, while ZEC ignores the longer term (beyond a few decades) effects of ice continuing to melt. To get GEI to 0 on any reasonable timescale will require a lot of negative emissions (350ppm CO2 is the most recent estimate for where the atmosphere needs to be for GEI=0 I've seen) because the ice sheets have to be stabilised and they are very far from stable at the moment.

[Shared Humanity]

If we let this thread focus on the difficulty of getting to total zero emissions than I think this new research will get lost. I have always been curious about this chart, specifically the spike that occurred in the 1940's and the drop following it.

Industrial production spiked during WWII and a decade long worldwide recession followed it. Wouldn't CO2 emissions track with this? The steep climb in temperatures beginning around 1970 coincides with the rapid industrialization of much of the third world. Does this trend suggest that temperatures are much more sensitive to current CO2 emissions?

[El Cid]

I have always been curious about this chart, specifically the spike that occurred in the 1940's and the drop following it.

Industrial production spiked during WWII and a decade long worldwide recession followed it. Wouldn't CO2 emissions track with this? The steep climb in temperatures beginning around 1970 coincides with the rapid industrialization of much of the third world. Does this trend suggest that temperatures are much more sensitive to current CO2 emissions?

Interesting study about the early 20th century warming and its causes:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6033150/

Basically we do not know what caused it, and climate models do not replicate it.

My conclusion has long been that our models are still very very bad, they can not replicate even quite well documented changes in climate (eg. green sahara, Holocene optimum precipitation and temperature, early 20th c. warming, etc.)

I do not trust them a bit. Climate is much more complex than we currently figure

[anthropocene]

Tor and El Cid:
You seem to make calculations where forcings are linearly related to emissions, or to concentrations of GHGs in the atmosphere.
However, forcings from CO2 are logarithmic.

"The relationship between carbon dioxide and radiative forcing is logarithmic, at concentrations up to around eight times the current value, and thus increased concentrations have a progressively smaller warming effect."

Thus, with flat emissions, the forcings will slowly decline. The decay function for CO2 is central for the argument.

https://en.wikipedia.org/wiki/Radiative_forcing

Incorrect. You are treating CO2 concentration and emissions as interchangeable. This is NOT the case (at least in the short term). El Cid is correct in treating cumulative emissions and temperature as having a (almost) linear relationship. See the temperature diagrams half way down this post: https://www.easterbrook.ca/steve/2013/02/how-big-is-the-climate-change-deficit/

The failure is by taking in isolation the physical process of increasing CO2 concentration and its warming potential (radiative forcing) and directly applying it to emissions rather than modelling the entire earth system (In other words: If we lived on a barren planet with no ocean and so 100% emissions enter the atmosphere then the CO2 concentration and emissions would be interchangeable - fortunately we don't).

[Sciguy]

There is a new post on this subject over at ATTP.
https://andthentheresphysics.wordpress.com/2021/01/08/warming-commitments/

The "And Then There is Physics" blog post refers to a 2010 Real Climate post about a study published in Nature.com about Zero Energy Commitments.

Here is the Real Climate post:

http://www.realclimate.org/index.php/archives/2010/03/climate-change-commitments/

Climate change commitments
— gavin @ 3 March 2010 - (Español)

There is an interesting letter in Nature Geoscience this month on what climate changes we have actually already committed ourselves to. The letter, by Mathews and Weaver (sub. reqd.), makes the valid point that there are both climatic and societal inertias to consider.

And here is the letter in Nature that they were describing:

https://www.nature.com/articles/ngeo813

Matthews, H., Weaver, A. Committed climate warming. Nature Geosci 3, 142–143 (2010). https://doi.org/10.1038/ngeo813

To the Editor

The perception that future climate warming is inevitable stands at the centre of current climate-policy discussions. We argue that the notion of unavoidable warming owing to inertia in the climate system is based on an incorrect interpretation of climate science. Stable atmospheric concentrations of greenhouse gases would lead to continued warming, but if carbon dioxide emissions could be eliminated entirely, temperatures would quickly stabilize or even decrease over time. Future warming is therefore driven by socio-economic inertia, and is only as inevitable as future emissions. As a consequence, mitigation efforts to minimize future greenhouse-gas emissions can successfully restrict future warming to a level that may avoid dangerous anthropogenic interference with the climate system. The challenge of climate mitigation, although daunting, is fully within the scope of human control.

Climate change commitment is defined as the future warming to which we have committed ourselves by virtue of past human activities. Because of the slow response time of the climate system, the equilibrium climate consistent with current levels of greenhouse gases will not be reached for many centuries. This so-called constant-composition commitment results as temperatures gradually equilibrate with the current atmospheric radiation imbalance, and has been estimated at between 0.3 °C and 0.9 °C warming over the next century2 (Fig. 1).

Constant-composition commitment is often misinterpreted as the unavoidable warming that is yet to manifest in response to past greenhouse-gas emissions3. However, the climate warming commitment from past greenhouse-gas emissions is more correctly defined as a 'zero-emissions commitment' — that is, the future climate change that would occur, should greenhouse-gas emissions be eliminated entirely4. In response to an abrupt elimination of carbon dioxide emissions, global temperatures either remain approximately constant, or cool slightly as natural carbon sinks gradually draw anthropogenic carbon out of the atmosphere at a rate similar to the mixing of heat into the deep ocean5,6,7,8 (Fig. 1). From this we conclude that the elimination of carbon dioxide emissions leads to little or no further climate warming; that is, future warming is defined by the extent of future emissions, rather than by past emissions.

This is a fundamentally hopeful conclusion; if we can successfully coordinate international emissions reductions in the coming decades, we can successfully restrict global temperature increases to a level that will prevent dangerous impacts on both human and environmental systems.

[The Walrus]

Is there not research indicating that the key is energy imbalance, and even if Global warming stopped how long before the energy imbalance returned to zero?
Is there not also a question of unhelpful changes to land and ocean carbon sinks, including some sinks becoming carbon emitters?

And anyway, if they are right we will just have to rely on all the other stuff humankind does to continue to successfully trash the planet.

Yes, the key is energy imbalance.  It is not as simple has just atmospheric CO2 concentrations, but we can use a simplistic case for our argument.  Namely, neglecting all other factors, the temperature will increase in response to an increase in CO2.  Simple physics.  The temperature will rise until it reaches a new equilibrium, but not instantaneously.  Instead it will increase based on the rate of change.  Much has been written on how long this would take.

If CO2 were to somehow be held constant, a new equilibrium will be established with a new average temperature.  This is not zero emissions.  Rather it is an emission rate equal to the carbon sinks. 

If net emissions were to drop to zero, atmospheric concentration would begin to fall, until a new equilibrium is reached.  The temperature change would be a summation of the previous increase and the new decrease.  There would likely be a continued rise, but not for long, until the new energy imbalance forces a temperature decrease.  The authors of this paper (Michael Mann, et. al.) suggest that this time frame would be rather short, compared to previous claims.

[gerontocrat]

And this study says conmmitted warming greater than current conventional wisdom but will take longer to happen. Note the importance of clouds again.

https://apnews.com/article/climate-climate-change-pollution-3f226aed9c58e36c69e7342b104d48bf
Study: Warming already baked in will blow past climate goals

The amount of baked-in global warming, from carbon pollution already in the air, is enough to blow past international agreed upon goals to limit climate change, a new study finds.

But it’s not game over because, while that amount of warming may be inevitable, it can be delayed for centuries if the world quickly stops emitting extra greenhouse gases from the burning of coal, oil and natural gas, the study’s authors say.

Dessler and colleagues at the Lawrence Livermore National Lab and Nanjing University in China calculated committed warming to take into account that the world has warmed at different rates in different places and that places that haven’t warmed as fast are destined to catch up.

Places such as the Southern Ocean, surrounding Antarctica are a bit cooler, and that difference creates low-lying clouds that reflect more sun away from earth, keeping these places cooler. But this situation can’t keep going indefinitely because physics dictates that cooler locations will warm up more and when they do, the clouds will dwindle and more heating will occur, Dessler said.

Outside experts said the work is based on compelling reasoning, but want more research to show that it’s true. Breakthrough Institute climate scientist Zeke Hausfather said the new work fits better with climate models than observational data.

Study - paywalled
https://www.nature.com/articles/s41558-020-00955-x
Greater committed warming after accounting for the pattern effect

Abstract
Our planet’s energy balance is sensitive to spatial inhomogeneities in sea surface temperature and sea ice changes, but this is typically ignored in climate projections. Here, we show the energy budget during recent decades can be closed by combining changes in effective radiative forcing, linear radiative damping and this pattern effect. The pattern effect is of comparable magnitude but opposite sign to Earth’s net energy imbalance in the 2000s, indicating its importance when predicting the future climate on the basis of observations. After the pattern effect is accounted for, the best-estimate value of committed global warming at present-day forcing rises from 1.31 K (0.99–2.33 K, 5th–95th percentile) to over 2 K, and committed warming in 2100 with constant long-lived forcing increases from 1.32 K (0.94–2.03 K) to over 1.5 K, although the magnitude is sensitive to sea surface temperature dataset. Further constraints on the pattern effect are needed to reduce climate projection uncertainty.

[kassy]

Also the liquid form:

Volgens de wetenschappers namen oceanen in 2020 fors meer warmte op dan in 2019. De onderzoekers spreken van 20 zettajoule,

...

Omdat oceanen vertraagd reageren op het broeikaseffect, wordt verwacht dat de opwarming van het water in ieder geval nog enkele decennia aanhoudt. Cheng waarschuwt dat "samenlevingen zich daarom moeten aanpassen aan de onvermijdelijke gevolgen van de onverminderde opwarming".

https://www.nu.nl/buitenland/6101706/oceaantemperatuur-bereikte-in-2020-nieuwe-recordhoogte.html

2020 ocean heat uptake is a new record with 20 ZJ. We also have at least some decennia of warming water ahead.

Upper Ocean Temperatures Hit Record High in 2020 (OS) :
https://link.springer.com/article/10.1007/s00376-021-0447-x

And linked in there, possibly interesting but haven´t read it yet.
https://essd.copernicus.org/articles/12/2013/2020/

Maybe it is more interesting to figure out when we go net negative or at which rate we approach that?

After all that decides what damages we will incur.

The whole nagging issue is this vague 1,5C safe limit which totally ignores the rather imminent loss of most Arctic sea ice and the consequences that brings.

[interstitial]

I thought the limit was 1.5 C or 2.0 C by 2100 not that it would stop at that number but just it was far enough away to ignore.

[kassy]

Per ASIF's recent post,

•   2020 was 0.6°C warmer than the standard 1981-2010 reference period and around 1.25°C above the 1850-1900 pre-industrial period"

So, we went from first reaching about 1.0° above to having a second 1.25° above in 6 years (not yet averaging 1.25° above, yet).  I'm not saying we'll get to 1.5°  in 6 more years, but I wouldn't bet against getting there by the end of 2030 and staying there by 2035.  Electric vehicle adoption and coal-fired electricity generation shut downs will certainly put a dent in the increases.  Will it approach being enough? I doubt it.  All car sales would have to be EVs after 2025 to do their part ...

I added the bolding.
So we have about 0,25C margin.

The ASI Vol trend is heading for 0 sometime in the 2020ies to 2030ies, see (start at last posts) :
https://forum.arctic-sea-ice.net/index.php/topic,2348.msg298252.html#new

So this is the trend at about 1,0 to 1,25C. So we do not need to hit 1,5C overall to lose it.
Also it is not an either or thing. Every year sees more open water adding heat into the system.

That Polarstern north pole picture was so alarming. It was all shattered while a couple of years ago people still tried to walk and ski to there...

So we will see a part of the ASI loss temperature effect early (because we will lose part of the ice cover first) so that will gradually add  up to 1,9C. (see #20 above) but it will start doing so earlier along the way. , it does not need 1,5C. This means we will hit that any way.

The other question is when we think we could be carbon negative...

[interstitial]

the Us and Europe still talk like they should be aplauded for getting to net zerro by 2050. we need a ban on new ff infrastructure ice vehicles today. net zero by 2030 or 2035 should be our goal.

[El Cid]

There is a clear acceleration in temperature trends globally, especially in NH midlatitudes. This is likely related to ASI loss. This is not going to stop. We shall definitely NOT hit zero emissions by 2030 and likely will not even get there by 2050. 1,5 C is a pipedream.

all we can realistically expect is for Co2 LEVELS to stabilize after 2050, meaning that we shall see at least 3 more decades of cca +0,2 C/decade rise in temperatures. Mind you, that is rather +0,5 C / decade in NH midlatitudes and likely more during winter as you get closer to the Arctic.
Non-Mediterranean Europe saw a cca 2C+ temperature rise during the past 40 years (and 1 C during the past 20 yrs). I pretty much expect the same amount until 2050. This is theoretically avoidable (just like the global spread of COVID was) but will happen due to our stupidity anyway.

[blu_ice]

the Us and Europe still talk like they should be aplauded for getting to net zerro by 2050. we need a ban on new ff infrastructure ice vehicles today. net zero by 2030 or 2035 should be our goal.

It should, but it isn't. If net zero goal is placed within a decade, people currently in power would have to make the tough decisions. They don't want to do that.

As net zero goal is placed further into the future, it's all business as usual until the powers-that-be conveniently retire. Technology may reduce some emissions so everybody can pretend things are being done, when in fact nothing isn't.

[El Cid]

100% right bluice

[Shared Humanity]

I have always been curious about this chart, specifically the spike that occurred in the 1940's and the drop following it.

Industrial production spiked during WWII and a decade long worldwide recession followed it. Wouldn't CO2 emissions track with this? The steep climb in temperatures beginning around 1970 coincides with the rapid industrialization of much of the third world. Does this trend suggest that temperatures are much more sensitive to current CO2 emissions?

Interesting study about the early 20th century warming and its causes:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6033150/

Basically we do not know what caused it, and climate models do not replicate it.

My conclusion has long been that our models are still very very bad, they can not replicate even quite well documented changes in climate (eg. green sahara, Holocene optimum precipitation and temperature, early 20th c. warming, etc.)

I do not trust them a bit. Climate is much more complex than we currently figure

Thanks. I knew the question was pretty naive.

[ArgonneForest]

the Us and Europe still talk like they should be aplauded for getting to net zerro by 2050. we need a ban on new ff infrastructure ice vehicles today. net zero by 2030 or 2035 should be our goal.

It should, but it isn't. If net zero goal is placed within a decade, people currently in power would have to make the tough decisions. They don't want to do that.

As net zero goal is placed further into the future, it's all business as usual until the powers-that-be conveniently retire. Technology may reduce some emissions so everybody can pretend things are being done, when in fact nothing isn't.

This is a rather simplistic and untrue explanation

[El Cid]

the Us and Europe still talk like they should be aplauded for getting to net zerro by 2050. we need a ban on new ff infrastructure ice vehicles today. net zero by 2030 or 2035 should be our goal.

It should, but it isn't. If net zero goal is placed within a decade, people currently in power would have to make the tough decisions. They don't want to do that.

As net zero goal is placed further into the future, it's all business as usual until the powers-that-be conveniently retire. Technology may reduce some emissions so everybody can pretend things are being done, when in fact nothing isn't.

This is a rather simplistic and untrue explanation

how is it untrue?