Agreed. We are already beyond the tipping point. Positive feedback loops already kicked in (thawing of Tundra, lower albedo due to glaciers melting, ...). We would need to go carbon negative right away and stay at those levels for years. Or go big about engineering the climate until we carbon levels return to normal levels.
I believe, but obviously cannot prove, that we've already passed the tipping point. Thawing tundra, ocean acidification, and burning forests are all now in positive feedback loops. Meaning we could stop all human activity tomorrow and atmospheric CO2 would continue to increase.
But the great unknown that scares me is the thawing methane clathrate. Hard to imagine mitigating this one.
Said another way, within two full human lifetimes the planets climate could further be irreversibly changed locking in 23 feet of sea level rise from Greenland alone.
Though, generally for emissions we are talking about a first order derivative. Just because you've slowed down from 100 to 50 does not mean you won't still run out of roadway.
So, if we are a hair away from that tippingpoint, and magically go to zero emissions, we'll still hit the tipping point. Hence, it's not two lifetimes, but that is the total runway left so far for this.
You can also consider the other extreme where CO2 is dumped into the atmosphere that everything shortens up. Another analogy, boil some water, put it off the burner, drop a small amount if ice in the water. The water won't cool off fast enough for the ice to not melt. It may take 10 minutes for that to happen, but the point of no return was when the water started at a boil.
The scary thing is that even if we stopped carbon emissions today, the world would keep getting hotter for many years, even if don't trigger any more of the climate tipping points.
Let me preface this by saying that I believe climate change and decarbonization to be one of the critical challenges of our time. That said…
This article’s title and its content are completely at odds. Here’s a critical passage:
> As the ice sheet melts, its surface will be at ever-lower elevations, exposed to warmer air temperatures. Warmer air temperatures accelerate melt, making it drop and warm further. Global air temperatures have to remain elevated for hundreds of years or even longer for this feedback loop to become effective; a quick blip of 2 degrees Celsius (3.6 degrees Fahrenheit) wouldn’t trigger it, Höning said. But once the ice crosses the threshold, it would inevitably continue to melt. Even if atmospheric carbon dioxide were reduced to pre-industrial levels, it wouldn’t be enough to allow the ice sheet to regrow substantially.
> “We cannot continue carbon emissions at the same rate for much longer without risking crossing the tipping points,” Höning said. “Most of the ice sheet melting won’t occur in the next decade, but it won’t be too long before we will not be able to work against it anymore.”
So…we potentially have hundreds of years to bring temperatures back down before the “tipping point” triggers? Forgive me for not being super alarmed.
100 years ago we’d just barely started dumping carbon into the atmosphere. That is a long time.
EDIT: to be clear, yes of course it not enough to stop dumping carbon into the atmosphere in the next hundred years, but it does give us (potentially) decades to figure out large-scale carbon capture and sequestration even if we exceed the thresholds described here (1000 gigatons).
Going carbon-neutral might have been the right answer 20 years ago. To avoid 1.5 degrees of warming above pre-industrial levels, we need to go carbon-negative today.
Even if we reach 0 in 13 years, the road to flipping the magnitude will be long, and I estimate longer than the time to build a reactor.
This is a nice notion, but ignores the feedback cycles which have already been set in motion - at this point, reducing our emissions to zero may provide little benefit, as as the Arctic and Antarctic thaw, relict methane is being emitted at an alarming rate, wildfires are becoming far more frequent globally, and oceans are no longer functioning terribly well as carbon sinks, further pushing emissions.
I'm not saying we shouldn't try, but I fear we're already past the point of no return for catastrophic climate change.
I don't think it's a given we can reverse or even stop climate change. There are many positive feedback loops going on right now.
AFAIK neither the Paris accords or any climate management proposals entertain the idea of stopping climate change.
Edit: positive feedback loops are things like the melting ice caps. Less sunlight is reflected back to space by the white ice which means more is absorbed by the dark sea. This causes the earth to warm and more of the ice caps to melt....
In climate science there is something called the tipping point. This is when mechanisms like positive feedback will make drastic climate change inevitable (with current technology).
When the tipping point will happen is up for debate. IMO the idea that we have already passed the tipping point is also up for debate.
Unfortunately we already emitted enough carbon to force pretty catastrophic warming, so we'll need to become net negative for at least a couple of decades before we can talk about low net positive emissions.
The problem with the "Tipping Point" is that we humans have gotten to the point where we could cool the earth if we got desperate enough. We know from studying volcanoes that injecting large amounts of sulphur particulates into the stratosphere will cool the earth quite effectively. Any number of industrialized nations could do enough of this to counteract global warming for modest fractions of their GDPs. There are other materials we could use that would persist higher than the stratosphere and reduce certain negative consequences.
Unlike other things we can do about climate change, this is also quick!
Of course, the problem with this, is that there are sure to be unintended consequences. Perhaps this is another sort of "Tipping Point" -- where humanity follows a spiral of ever-increasing interventions with unintended consequences that spiral out of control.
More important: the ability to manipulate the global climate will have profound geopolitical and strategic ramifications. These are perhaps just as dangerous as the CO2 tipping point.
We have already kickstarted positive feedback loops like thawing of the tundra, reduced albedo due to smaller ice sheets, ... . We actually need to go carbon negative for a while to offset those. The technology you mention surely will help greatly in avoiding speeding things up, but they won't take us back to preindustrial levels alone.
We had to hit net zero 10-20 years ago. We’re already hitting climate tipping points, so we’re already committed to some form of climate engineering. The lowest risk approach to that is carbon capture.
Since we already triggered feedback loops (eg. thawing of permafrost) we probably need to go carbon negative for a while to stop said phenomena. This means over-provisioning our clean energy supply to power CO2 scrubbers or some similar tech.
I fear that, considering how hard is to get the world to agree to net 0 emissions, the negative emissions discussion will probably be a bloodbath.
Let's start things off on the proper foot, scientifically:
Even if we stopped all CO2 emissions today, the world is very likely to hit significant tipping points already, unless you're the sort of person who doesn't consider the disintegration of the Larsen B ice shelf, the massive Greenland glacier melts, and the increase of Siberian methane emissions (that lovely, pants-shitting and realistic close-range extinction scenario) to be "tipping points".
The only way this plays out is that the less damage you do, the easier it will be future generations to stabilize the situation through proper technology and policy (or you think people will just idly accept 500 years from now that the actions of today will lead to their demise?).
So models have curves where depending on the different scenarios, the amount of damage varies. Since this is a continuum of environmental effects, not discrete points, picking a single point as a goal is a mix of what you can do realistically and the amount of political buy-in we can get about how much guilt we can take for fucking things up, plus/minus the inherent uncertainty in any model.
So yeah, you can say that it's arbitrary about as much as a recommended dietary intake is arbitrary, or a recommended maximum radiation dosage is arbitrary, or the number of minutes of exercise per day is arbitrary.
This is a great example on how to turn a one-paragraph response into a two-page fluff article.
Doing solar radiation management as a substitute for drawing down CO2 would be disastrous.
But we're starting to see various positive feedbacks kick in, where rising temperatures cause the planet to release CO2 and methane of its own. We see evidence of this in geologic history too, where a modest temperature increase due to an orbital variation causes greenhouse releases that tip the planet into a warming cycle.
If we cross that tipping point, reducing our emissions to zero won't keep the CO2 from increasing further. We might need SRM to keep that from happening. The tipping point could be as low as +1.5C, we're already over +1C, and we've made essentially zero reductions to our emissions so far.
There is a school of thought that suggests that if we've already hit the climate change tipping point, we should put more efforts at this sort of terraforming-type approach instead of playing the long game by slowly curbing emissions.
We're past the tipping point to run away warming according to some reputable climate scientists. Im not saying we can't reverse it but we're not even attempting to at the moment beyond half hearted deals like the Paris climate accord.
I'm under the impression that the climate feedback loops have developed too much inertia for us to counter with a technical solution that could reduce or even reverse climate change at this point. Even if the world stopped emitting carbon tomorrow we're still going to coast past the IPCC's recommended limits and straight into the worst-case scenarios before the end of the century.
While I still think it's a worthy cause to reduce and sequester carbon I think we shouldn't be thinking about how to reverse this.
We're going to have to live in a world with reduced fresh-water supplies, a dwindling supply of usable soil, and migrant populations. That's going to require a radical shift in global politics and economics.
I think a big part of our role as engineers will be helping society to adapt to these new conditions. How do we continue to deliver power to cooling systems during record-breaking heat-waves, build nuclear reactors that are safe against the new kinds of natural disasters we're encountering, manage housing and construction to reduce emissions and local heat, etc.
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