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Comment by aszantu | Hacker News Reader

I recently thought... sure everyone says it's the CO², but then I saw articles that said, the CO² didn't change as much as they said it did. 4% of the atmosphere or so, because water takes it up and some kinds of stones do the same. What if we generally just generate too much heat? And the heat gets trapped in the atmosphere? Every time someone uses energy, it generates heat. Everytime we make energy from hydrocarbon, we generate heat. Would there be a way to let the heat go to space? Or if we want to preserve it on earth, a way to turn heat back into hydrocarbon?

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> And the heat gets trapped in the atmosphere?

That's what CO2 does. It is a greenhouse gas, meaning it traps heat that would otherwise have escaped into space.

> Or if we want to preserve it on earth, a way to turn heat back into hydrocarbon?

It is literally impossible to turn heat, by itself, into anything useful. That's the 2nd law of thermodynamics, and it's a cruel mistress.

It's nice to think about alternative solutions to these problems, but you need to have at least a basic understanding of basic level physics if you want to discuss this sort of thing.

My biggest frustration with global warming deniers has been that I understood the basics of global warming as a 6-7 year old, when I first read something about the greenhouse effect (it wasnt even in the context of global warming).

The only basic pieces of information you need to understand climate change are:

1) The greenhouse effect exists. That is, when you have something like glass, it will let energy in in the form of light, but it won't let as much energy escape once it's converted to heat. This concept can be grasped by anyone who has walked into a car that has been parked out in the sun. And by the massive clue in the name, that is the existence of greenhouses.

2) Carbon Dioxide is a greenhouse gas. That is, it acts like glass does in a greenhouse. This is harder to believe from first principles, but it's not that hard to believe. For me the clinching explanation (again, as a kid) was learning Venus was hotter than Mercury. And there is no reason to believe folks are lying about this, and I don't believe anyone is even contesting this.

3) Understanding how fossil fuels came into existence (basically, organic material trapped over centuries in the ground. again, the clue is in the name) and understanding the CO2 lifecycle, and how burning fossil fuels adds material to the CO2 lifecycle that was not there earlier. This isn't something that can be determined easily by a kid from 1st principles, but it's something that no one is really contesting either.

Once you accept these 3 fairly straightforward basic physics phenomena, global warming is inevitable.

The only questions are whether the release of CO2 is significant enough to have an impact, where we have to rely on measurements and scientists. But seeing that there was a fairly standard progression in how deniers would first deny global warming was ever happening, then deny that it was anthropogenic, then claim it wouldnt have as negative an impact, and now claim that well, it's too late...let's look at mitigation; I was able to filter them out when they were at step 1 itself.

Aside: I also want to point out the horrific misunderstanding people have about the terms "global warming" and "climate change" which are fairly self descriptive, but apparently is a nefarious effort to "hide the spike". Global Warming (i.e., more energy in the earth's ecosystem due to the greenhouse effect) leads to Climate Change (that is, changes in our climate behavior).

One is a cause, and the other is the effect. Both are valid and orthogonal concepts, and not some sort of conspiracy.

> 3) Understanding how fossil fuels came into existence (basically, organic material trapped over centuries in the ground. again, the clue is in the name) and understanding the CO2 lifecycle, and how burning fossil fuels adds material to the CO2 lifecycle that was not there earlier.

Adds material to the CO2 lifecycle that was not there earlier? Isn't it just rereleasing CO2 that was in the atmosphere earlier?

> Isn't it just rereleasing CO2 that was in the atmosphere earlier?

I don't know the facts here, but I'm pretty sure carbon can slowly be added from other sources. So sure, that CO2 might have been in the atmosphere before, but then we added more CO2 as well.

The point being, the CO2 we're digging up wasn't in our atmosphere before. The atmosphere that we and all the animal and plants have been adapted too. Sure, there's a time when the CO2 concentration (and even O2) was wildly different. But then there were other animals living on earth, that was adapted to those conditions. Slow change is fine, rapid change is disastrous.

>Isn't it just rereleasing CO2 that was in the atmosphere earlier?

Yes, and the Arctic was once tropical.

Much of the coal comes from a unique period in earth's history when there were many trees, but enzymes that could deal with lignins hadn't yet evolved. Which led to a steady and significant accumulation of carbon in that coal.

Humans, and much of the life we see around us, evolved in the subsequent periods of higher oxygen and depleted CO2. As we reverse that effect, we return the atmosphere nearer to how it once was - when humans and such weren't around. The planet and its life will be fine. Us and the multiple species on which we depend may well not be.

By burning it we are releasing carbon that has been stored for millennia and accumulated over millennia. It's introduced as though it were new into our carbon cycle.

Extremely solid explanation. You should put this into an article or video if you have a website.

> now claim that well, it's too late...let's look at mitigation

That's a pragmatic position, not a denier's position. I'm very progressive but I realized long ago we were never going to get anywhere with the 'everyone reduce' strategy. We should have started looking at mitigation options decades ago.

Isn't the controversy over second order effects though?

For example water vapor contributes far more to warming than CO2. The calculations are all about CO2 increasing temperatures, increasing water evaporation, which then increases heat trapping.

If all it was was a simple first order "how much warming does co2, and co2 alone" produce, then there wouldn't be the arguing there is now.

If it was about honest discovery of scientific facts, then there wouldn't be the arguing there is now. In fact, outside of the US, there isn't much arguing (there are a few fringe climate deniers, but they're not mainstream). The problem is vested interests, and people burying their heads in the sand because they're unwilling to give up aspects of their lifestyles.

An important aspect of the impact part is that there are many highly non-linear processes. A change from -10 deg C to -7 deg C might not be a huge deal, but a change from -2 deg C to +1 deg C can be as ice melts around 0 deg C.

Another important aspect is that "average temperature" conceals change, by virtue of being an average. The average of (10, 10, 11, 13) is 11, but so is the average of (5, 7, 15, 17).

Comparing Venus to Earth is silly. Venus's atmosphere is mainly carbon dioxide. On Earth it is a trace gas, measured in parts per million.

Carbon dioxide blocks a narrow spectrum of radiation. It acts a lot like food coloring dye mixed in water. If you mix in a couple of drops, the change is dramatic, but if you double it and mix in a couple more, the change is much less so.

If the only effect on the atmosphere was the CO2 greenhouse effect, and we added 10x the CO2 the average global temperature would only rise a couple of degrees.

The issue and the controversy that surrounds CO2 is how the Earth will respond to this added heat that it can't get rid of. If it's a tipping point, and will end up in a death spiral of factors compounding upon each other (ex. the permafrost melts and changes the albedo of the earth and that causes more warming, etc.) is where the science of climate change actually is.

The problem is that climate is complicated and no one can predict exactly how it will behave. This is why there are ton of models and it seems no one can agree upon how much the effect will be.

Climate skeptics will argue this is because the science done so far is mostly conjecture and very weak, and the conspiratorial among them will say that only studies that support climate change are being published/funded, so there is a lot of bias to make out that their evidence is stronger than it is. There has also been a lot of modifications to historical temperature readings, (this seems to be with good justification), but I personally can't judge.

Whether the effect of CO2 is going to be large or small is outside of both of our grasps, and we really have to trust on others to make that determination, unless you're willing to really learn the science behind it.

However, your list of reasons are just muddying the situation even further. They are easily debunked and if you proclaim them, and people find out they don't hold muster, you may drive people further into the climate change skeptic camp, which I don't think you really are trying to do.

"It is literally impossible to turn heat, by itself, into anything useful. That's the 2nd law of thermodynamics"

That's not quite true/relevant.

Matter can be turned into energy, energy can be turned into matter, theoretically at least. More practically a Stirling engine or peltier will turn heat into electricity, and filament bulbs did a good enough job of turning heat into light.

Plus you can still cheat the 2nd law locally. I can heat my house in winter for example, it isn't just a slow uniform slide to the heat death of the universe.

> That's not quite true/relevant.

It’s actually extremely true and relevant.

> Matter can be turned into energy, energy can be turned into matter, theoretically at least.

None of these conversions are 100% efficient. The second law effectively puts limits on the efficiency of heat engines[1] that depend on the difference between “hot” and “cold” in the engine. At low temperature differences, the theoretical efficiency is extremely poor[2] and the practical efficiency is even worse.

Peltiers are not exempt from this either.

[1] https://en.m.wikipedia.org/wiki/Carnot_cycle

[2] https://en.m.wikipedia.org/wiki/Heat_engine#Efficiency

I'm not saying any of it is efficient, just not 'literally impossible'.

I said "heat, by itself", not just "heat". And I stand by what I said. It is fundamentally correct. The state of entropy of the an isolated system will always increase over time.

Yes, you can bring in other things, like an outside system or additional useable energy, but that only disproves the misquoted version of my statement.

> you need to have at least a basic understanding of basic level physics if you want to discuss this sort of thing.

I'm sure when you talk to people like that it makes you feel really good and secure about your own beliefs and like you're on The Winning Team, but being a dick like this to someone who is asking a question makes everything more divisive and worse. If you like arguments and preserving your own sense of intellectual superiority over others, congratulations on perpetuating more of the same stagnation. If you're interested in anything productive, sorry, but you done goofed.

Does talking down to people and calling them dicks often yield the kind of results you're looking for? Remove the beam from thine own eye, buddy.

CO2 did increase a lot. The ratio of CO2 in our atmosphere got up by more than 40% since 2 centuries ago. And that's despite effects which slow down the CO2 increase, like absorption by the ocean.

Source: https://www.co2levels.org/

edit: fixed increase ratio from 1800 to now.

It hasn't tripled; we've gone from about 280 ppm to about 420 ppm. That graph's y-axis doesn't start at zero.

(That isn't to say that 420 ppm isn't really bad.)

You're right. My tired brain bugged when seeing 30% lower than today.

That's what's so striking. For most other global warming phenomena, the actual change recorded to date isn't that big. But for CO2, it's huge.

Taking your comment seriously:

People have done the math on the heat directly released by burning fossil fuels, and it isn't that high.

What CO2 does is keep more of the SUN'S heat on Earth. And that turns out to be a much more important contribution to the temperature of the Earth than the heat directly released by burning fossil fuels.

Current CO2 levels are a full 50% higher than they were 80 years ago or so, and that makes a big, big difference.

https://climate.nasa.gov/evidence/

All that is insignificant compared to the heat output of a certain nearby star.

The star's output is so significant that even the tiniest change in how that energy is absorbed and retained has large effects on the little planet.

So we find ourselves where we are.

To elaborate, the solar energy hitting earth is about 1,000 W per square meter near the equator near noon. The total per capita energy consumption in the US is roughly 10,000W. That means that the energy hitting the Mediterranean Sea (or clouds above it) in a single hour in early afternoon is roughly equivalent to the total annual energy needs of about 250 billion people at US per capita energy usage. And The Mediterranean is only about half of one percent of the planet's surface area.

I am actually curious about how much land use changes and heat from human activities contributes to climate change.

Theoretically the limit to the number of people we could support on earth with unlimited energy (eg cheap fusion) is not limited by space or food or water (the later solved by energy) but by simple thermodynamics. We'd cook ourselves if there were too many of us. Note this happens at many orders of magnitude more population than we currently have.

IIRC someone crunched the numbers that even with unlimited fusion power, if you extrapolate the growth in energy use in the 20th century, we could only continue for ~200 years before significantly increasing global temperature due to waste heat.

An innocent-seeming 5% growth turns in to four orders of magnitude if it continues for two centuries.

Fascinating. Of course any exponential growth tends to come to an end long before the impossible predictions, but it still highlights what a unique time we live in where we take growth of the population and the economy for granted. It has to slow down in the "near" future. Near being probably fifty years or more.

The total yearly energy consumption of the world is equivalent to a couple hours of the total sun energy hitting the surface of the Earth, so, I doubt it.

https://www.sandia.gov/~jytsao/Solar%20FAQs.pdf

Peter F. Hamilton had a sci-fi scenario where that was a real problem. In the Greg Mandel books I believe. We invented cheap fusion, and build so many fusion reactors that the added heat creates insane hurricanes all over the planet (if I remember correctly)

But yeah, I think it'd take an unbelievable amount of heat production to change the atmosphere directly. But the thing is the sun does bombard us with a mind-blowing amount of heat energy every day, so that's why changing the amount that's trapped by the atmosphere by a very tiny amount can have devastating consequences.

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