Ken Fabian

I'm not sure we know how any typical forest planted now will be faring in 200 to 300 years; do we choose which species to grow based on what the climate is now or what we expect it to be? Sounds like a concept with benefits to farmed and gardened forests but not necessarily useful at very large scale. There are good reasons to have forests and natural ecosystems but emissions mitigation isn't one of them. I think it is more appropriate to think of the CO2 reforestation sequesters as counting towards reductions in land use emissions rather than to justify ongoing fossil fuel burning. The impacts on emissions of mass forest plantings are going to be complex but ultimately they'll be finite and won't exceed what was emitted from prior deforestation; this kind of forest cultivation might take down the Carbon faster but it will reach peak biomass faster and stop being a carbon sink sooner. I don't think we can depend on sustained, non-reversible increases in global biomass to make a significant difference to the climate problem. If it doesn't reduce fossil fuel burning it isn't fixing the climate problem. And in my view it is a travesty to plant forests in order to protect fossil fuels from global warming.

To be serious about zero emissions we need these kinds of mechanisms in place in the world's major trading economies. Preferably pricing at rates like we really mean it, that ramp up predictably over time, like we mean it and without rafts of exemptions and exceptions, like we really mean it. But anything tariff related gets bent by geo-political concerns and I fear that anti-China sentiment will be used expressly to impede global growth of RE and EV's, in ongoing efforts to save fossil fuels from global warming.

If you want to make arguments to support these assertions you are welcome, but stating them doesn't make them true. In my experience pretty much only staunch doubt, deny, delay opponents of addressing global warming seem chronically unable to update what they are sure they know about climate science or climate policy or options for doing something, like renewable energy. Around 3/4 of all new electricity generation being added around the world is now solar and wind, on their merits, as commercial decisions - not out of deep commitment to zero emissions (although the possibility of emissions accountability emerging in the future does figure into investment decisions) but because of this - .

Sure, with fictional propulsion systems the impediments don't look so overwhelming. Reality is not so easy. Not that I would expect chemical propellants to be the favored choice apart from the initial launch - I would be looking at solar electric/arc-jets using asteroid water for reaction mass (or something like), ie something with barest minimum of consumables sourced from Earth. Whilst examples of electric arc-jets do exist that is not the same as large scale, long lasting versions with proven extreme reliability suitable for such a job; every part of such a mining project would be bespoke.

I have no fear of corporate tyranny in space because space lacks opportunities for profitable enterprise. It is only in fiction that there are opportunities that are worth the effort. Space companies milking the taxpayer funded agencies is a depressingly ordinary kind of bad behavior. Unless there is something I am missing, something big, it looks like if we take away the taxpayer funding there is no self funding commercial opportunity in space exploration or any space activities that don't directly service Earth customers. I don't count transporting astronauts to and from the ISS - or the ISS itself - as self funding. No space tourism venture comes close to recovering costs, let alone makes a profit. If anyone can point to anything we do in space apart from ground sensing and communications satellite services that earns income from Earth customers and can be self funding I'd be interested. Asteroid mining, in potential, is the best I can see and even that appears to be far short of viable. For unashamedly taxpayer funded ambitions in space I think meteor defense is as good as it gets - far reaching enough to support ongoing space R&D with big ambitions, with multi-nation participation, that might end up opening up and spinning off something commercially self funding, but will be worthwhile even if doesn't.

I expect the rate of success for self made wealth from initial poverty is very low compared to those starting from even modest (well short of "wealthy") inheritances - or just with families that can afford to be loan guarantors. "Just try hard and you will succeed" works much better for those with existing resources to draw upon - including being able to try again if not succeeding first time around more readily too.

I prefer to have the video contents summarised for discussion - if I watch every one that gets suggested to me there would not be enough hours. I don't doubt that, given enough funding, aerospace companies will attempt Mars sample return missions, with reasonable expectations (but no guarantee) of success. But I expect it to continue to be easier and more cost effective to send remote operated robotic equipment to Mars to analyze mineral samples than bring samples back. If something of exceptional interest worthy of the kinds of study that can only be done on Earth gets found then the case could be made for a sample return mission. The knowledge is what is valuable although no doubt the samples would have collector value. Not sure the extent to which Mars colony hype influences exploration priorities but it seems to be explicit in objectives for many Mars missions.

I think it is an oversimplification - or at least the quoted bit without the context and explanation of what that means could be misconstrued. Yes, some individual critter was a common ancestor of both baboons and humans, but it was not their only ancestor (or even only pair of ancestors). Their progeny would be a lot more like the parents and parent population than like baboons or humans and I would expect generations of "common ancestors" for each to coexist and for some of (and possibly all of) their progeny to also be common ancestors of both later lines. A whole lot of evolution would be still to come, including some cause for divergence into separate populations.

Human consciousness seems to be a predictive machine, anticipating the present out of near-past perceptions. Observations are never truly in the present yet it all seems to work. And maybe revisiting observations after actually makes for greater clarity.

As for restricting home computers (the OP) - the deaths of innocent victims from AI are hypothetical, and even more hypothetical from home computers. Deaths of innocent victims from misuse of assault rifles are not hypothetical. Not sure many home computers can even support the kinds of AI that can (hypothetically) be dangerous; AI as a tool used nefariously by military and intelligence services (including by despotic regimes) seems more likely to me than rogue AI. But assault rifles are designed for one purpose - injuring, maiming and killing people. I'd prefer that power to use such force be in the hands of trained people who understand proportional and appropriate responses as well as operate within the rule of law. (Which I would want to be the case for government agencies using AI as well). In functioning democracies with rule of law armed citizens rising up to support and protect their government and institutions when attacked by enemies, including insurrectionists makes more sense than as a standing tool, just in case, FOR insurrectionists. Without an existing, credible threat and absence of military capability to face it there seems no good cause for a standing armed populace. No government as better - Libertarianism - is delusional; the solution to bad governance is better governance, not absence of governance - and a lot of nations with high levels of personal freedom have made their institutions, like independent courts, their bulwarks against tyranny. From outside the USA it looks like the day the armed populace there rises up will be the nation's ruination - those weapons are for use against other Americans and the designation of "enemy of America" for those with different politics, religion, ideals as promoted through free speech and voting will be self serving justification at best. The historic Revolution may be the aberration, where the winners did not put themselves above the rule of law - eventually - once those who supported the King were ousted, or summarily executed, or had their property taken or were forced to flee (to Canada). The kinds of insurrection the US faces now doesn't look legitimate in any sense, and unlikely to result in greater freedom or prosperity even if it succeeds.

You could, but that wouldn't have the horsepower of a gasoline vehicle. Not correct; a gasoline vehicle might have greater range than an EV but weight for weight the power of electric motors beat ICE easily by a huge margin. If the vehicle has to carry oxygen as well as fuel an ICE won't have much range either. And if you have to bring the fuel AND the oxygen (or oxidant) from Earth then EV's running off solar power looks like the better choice every time. Somewhere like the moon might manage with direct solar power for 2 weeks out of 4; large lightweight solar wings in vacuum would not even present serious stability problems without wind - but may need shock absorbing stabilisers for rough ground. Or unfold and unfurl them when stopped to charge batteries. Traveling by lunar night would probably present other problems besides energy storage - scheduling to avoid it may be more practical.

All interesting, if disappointing. Does it mean this - "Demonstration of resonant tunneling effects in metal-double-insulator-metal (MI2M) diodes" (a demonstration of an optical rectenna in IR) only works because the source is in phase? Would not work otherwise? I suppose that means it was in phase but I don't know. "Linearly polarized" ? "Modulated by a 3320A function generator"? Polarized to a specific axis? It is all beyond my paygrade - but my surmise that it had to do with the heat emissions of the receiver overlapping with it's tuning seems wrong as well.

I don't know why Dr Novack thinks it but I think it because I think the photons interacting with an antenna don't add (all of) their energy as heat to the antenna, some energy making electrical potential. Some gets converted to electrical energy and carried away. It may initially be at thermal equilibrium but it isn't a closed system. Note, I don't think this as a certainty - I don't know enough. But if the antenna can't absorb IR because the temperature of the antenna makes it radiate IR - not the antenna transmitting IR because that takes electricity from somewhere else, but the materials radiating it in the normal way things that are warm radiate - then, yes, it is at thermal equilibrium and an IR rectenna cannot work. I had thought that interaction between EMR and an antenna was independent of antenna temperature but that was most likely ignorance - most working antenna aren't tuned to the band the antenna normally radiates in.

@sethoflagos I understand that antennae work as transmitters and receivers (but little real understanding of how they work). I am simply looking at energy flows. Antennae do turn EMR - if only narrow bands of it - into electricity and that energy is not being absorbed into the substance of the receiver. Simply, the energy that is diverted away isn't turned into heat in the receiver. In an otherwise closed system it has a leak; there will be loss of energy, ie cooling. Are you (or Kirchoff) saying an antenna won't work if the substance of an antenna radiates within the band it is tuned to - that IR emissions (specifically) are too close in wavelength to the receiver and prevent it working? This may indeed be the case - ie there isn't any flow of energy away as electricity in a rectenna tuned to the bands that materials radiate heat because it doesn't work. But at shorter or longer wavelengths - outside the IR - they will? Yet my understanding is optical rectennae have been shown to work - albeit at very low conversion efficiencies; at just what wavelengths, at what temperatures and under what conditions I don't know.

Thanks Sethoflagos. I admit I still can't say I understand. Seems to me the materials of an antennae will get warmed by what the antenna doesn't turn into electricity - but a warmer antenna should work at similar efficiency as a cold one, it not being a thermal phenomena; unlike an ordinary material less energy/heat is added to the material of an IR antenna than the total energy received and absorbed by it. I still think diverting it away as electricity diverts energy away from the combined emitter + receiver and should result in loss of energy within them, ie cooling.

I admit I am still unclear on this. Won't the receiver in this case only gain heat from what is not converted to electricity and will radiate back less than reaches it? Seems to me the rate of absorption by the antennae is independent of temperature of the antennae. A cooling emitter - radiating away some of it's energy, yes - but a cooling receiver too (?), diverting what reaches it to electricity instead of raising it's temperature (and radiating it back). Again, adding to efficiency?? I recall one of the suggested possible uses for Optical Rectenna is surface coatings on walls for cooling rooms, an alternative to A/C - "waste" heat turned to electricity as a bonus.

Off the top of my head I don't think that is correct. I think IR intensity of the emitter is purely temperature dependent but is not dependent on a difference in temperature - ie is independent of the temperature of the receiver. Except maybe will be receiving IR or conducted heat back - which, if the receiver is heated by the process would counter intuitively increase the efficiency... ?? Doesn't sound correct, but... @sethoflagos Any thoughts on this?

I would expect waste heat in it's most accessible forms eg warm or hot water, would not radiate IR strongly. Maximising surface area, perhaps like filter cartridges do - folded or coiled sheets - would give better results but more area means more cost too. The antenna part looks suited to cheap roll to roll "printing" (already tried successfully) but they need very fast response diodes included, of yet unknown suitability for "printing" on thin films. Get fast enough diodes and the potential conversion efficiency is very high, better than photovoltaics and, significantly, able to utilize bands like IR that PV cannot. PV struggles with longer (IR) wavelengths whereas Optical Rectennas should be a bit easier, with slower diodes. I suppose Optical Rectenna's are more likely to be a rival to photovoltaics for daytime energy before being rival to energy storage - worthwhile but I think PV costs are not the constraining factor anymore. Until or unless it is very cheap to make and use scavenging waste heat may still be out of reach. Not sure I see much significance for EV's directly. Whilst a high fossil fuels (or nuclear) grid suits overnight charging a high renewables one will likely suit daytime charging better. We are seeing a couple of ways forward eg faster charging is a highly sought option, to be more like fast filling up our tanks from service stations. But other options include abundance of charger fitted parking spaces that suit daytime charging and I expect there will be benefits to electricity grids by having EV's plugged in when not in use. A parked and plugged in (or for convenience a hands free, perhaps wireless induction connected) EV can be more than just another unresponsive source of demand - just the option to vary charge rates according to overall balance of supply and demand would make them a load leveling option for electricity grid managers. Drive to work, have the charge rate to a set to reach minimum requirement as priority and vary charge rates after that to achieve full charge by a set time, at the grid operator's discretion. Even potentially they can draw on those batteries, (under agreed terms and conditions) as well as have them contribute to household electricity use. I believe there is a trial section of road somewhere in the US with induction charging built into it - ie charge as you drive. Which I think may be more the kind of solution we will need for decarbonising road freight vehicles, that we don't want to have to sit idle for long periods. Railway style overhead (being trialed in Europe) is probably more efficient and cost effective than in-road induction... not electrification everywhere but strategically, so battery electric vehicles charge up on approaches and exits to cities and town and on long, heavily used inclines. Faster charging would also reduce how much of this style of highway electrification is needed too. I also expect it will be possible to unify electricity accounts so that charging an EV anywhere is billed to a household account - and for solar fitted households to have their contributions to the grid count towards it, wherever the car is used.

Optical Rectenna can convert Infrared radiation - radiant heat - directly into electricity but in practice so far the yields are extremely low. Like an antenna does with longer (radio) wavelengths - like the old "crystal radio" that powered itself from the radio waves. Not sure how that works in entropy terms - heat loss in the conversion? Of all the out there possibilities this would be one I'd like to see get some serious attention because if they can be made to work we could not only make electricity from waste heat but from radiant heat of all kinds, including down-radiation from clouds and atmosphere by night as well as from sunshine by day.

Not sure it is intelligence but natural selection does work a bit like trial and error, where the errors get left out in future iterations and the things that work persist. It can look like Life is making choices... but I think it is survivor bias.

I wonder to what extent the emergence of heavier hairs on older women's faces is them just not bothering to pluck or depilate in pursuit of beauty anymore, ie it actually began at puberty and has been happening all along.

If it is electricity from collecting plant material you want you might do better with gasification and running an internal combustion engine off that - you won't need a steam boiler which is a dangerous piece of equipment that usually requires regular testing and certification for safety - and possibly certification for the operator as well. But not sure that steam or gasification will be compact or easy to transport. A small, mobile gasifier generator -

An obvious issue to me is that the graph is based on relative "per molecule" impact, not atmospheric concentration, ie number of molecules. Less effect per molecule with a lot more molecules still adds up to warming. And the scaling makes a Watt/m2 change look small and insignificant when it is not. If you believed the interpretation of graphs like that by sources like CO2 Coalition global warming should already be slowing and the observed warming isn't actually continuing to accelerate - as if the observations must be wrong. But that graph isn't being used to inform people who have a good understanding, who might know that - it is intended to mislead people who do not. If enhanced greenhouse effect is self limiting and the effect is going to save us from having to do anything about it it should be saving us already and it isn't. We don't have long running observations from space but over the time the Ceres satellite has been operational we observe that the net imbalance between incoming and outgoing energy has been rising. This is a graph based on Ceres satellite data - Without delving deeper into how the graphs were calculated (which I have no wish to do) it isn't clear if this is theoretical (modeled) direct IR to space in the absence of all those complicating indirect flows to space.

I think our current path has already changed in significant ways almost entirely due to the successes of renewable energy (and batteries and EV's). RCP8.5 scenarios are considered very unlikely now, not because climate science was wrong about the impacts of emissions but because we now expect renewable energy to - at the very least - to displace growth of fossil fuel use significantly, with less emissions than otherwise. For all the disparaging it is an extraordinary achievement. To call it on purpose might be a stretch; for some it was on purpose, but those were initially considered fringe. More widely the supporting of renewables seemed more about empty gestures, with it actually working and being cost competitive coming as a surprise. Now that the renewable options are cost effective in most of the world it might still get some government support (as fossil fuels still do) but fundamentally, now and for the near future, it is market economics at work. As well to channel Canute and get the tide to stop - but it is clear that Doubt, Deny, Delay politickers around here have shifted their focus to obstructing the things that will make renewables reliable as their scale grows - opposing transmission lines, battery farms and wind, especially off-shore wind. Astro turf nimby opposition and trying to wedge them between climate concerns and local environmental impacts. But I think that - having made up the for, by, about environmentalist framing themselves - they underestimate the wider community support for emissions reductions with renewables, from people who do not identify with environmentalism, who's commitment is because of the science based advice, not green politics. Ultimately we will require strong, enduring commitment to climate stability at levels we are yet to see, but governments even being able to say they are committing to zero emissions is a remarkable shift. Economic alarmist fear of what has to be done to reach zero emissions (along with denying climate change's harms) has been one of the most successful denier memes, yet the most direct and effective and acceptable emissions reduction pathway is building an abundance of low emissions energy to displace fossil fuels and, hey, that is the one thing we are succeeding at. Much better than expected. The enormous stocks of fossil fuel capacity in place make early contributions by renewables seem small but within just one decade of crossing price equivalence thresholds renewables have become the most built new capacity additions, by a very large margin. That quickly. Less than 7 years ago Australia installed a Big Tesla Battery, to widespread derision. More than 20 times that capacity of batteries are up and running. That quickly. Not just Tesla but multiple mega batteries factories are already up and running. That quickly. Amongst all the cause for pessimism there is one thing going right - renewable energy. So we should not be surprised that the deniers are going all out to undermine public confidence in it.

@thidmir There are some scientists who think we underestimate the potential for non-linear ice sheet collapse but even a pessimistic James Hansen doesn't expect sea level rise of 50m to 100m 70m. The hypothetical maximum is around 70m - where Antarctica and Greenland lose all their ice sheets. The sea level impacts are likely to continue for a long time after reaching zero emissions, which, by necessity is a near term goal, within the next few decades, ie well before sea levels can stabilise. But there is an expectation amongst those that study the cryosphere aspects of climate change that the rate will slow with zero emissions. I suppose the worse case scenarios where emissions reductions are abandoned and there are ongoing high emissions that put us back on the RCP8.5 pathway, but even that looks like a trend that must top out, as fossil fuel stocks decline. Better prediction can help us work out what to expect for varying emissions scenarios but we don't need precise sea level rise predictions to know we urgently need to bring emissions down. Sea level rise, however it develops, will require adaptation but apart from locally at small scale (levies, imported fill to raise ground levels, building better for those that can afford it) that looks like a global retreat to higher ground and accepting an irrevocable loss of environmental capital (land).