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Comment by OroPla | Hacker News Reader

Given how we are at the tail end of a small ice age, shouldn't it be expected that temperatures recover to what they were previously? I never quite understood how climate is simultaneously too complicated to understand and predict the weather accurately while also a solved problem that we just need to take action on. And somehow the action we need to take is more taxation?

Since I keep hearing about this for at least 30 years now and still nobody took action the whole thing might be a bit more complicated than what the news media would have you know.

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It's pretty easy to model to a first approximation. Gases like Carbon Dioxide reflect certain wavelengths of infrared. When they are present in the atmosphere, they are present at a certain percentage concentration, and as that increases they reflect more infrared.

This matters because there are three ways for a body to eliminate thermal energy: radiation, convection, and conduction. Earth is not in contact with anything else, so it cannot conduct. It does not share an atmosphere with anything else, so it cannot convect. So that leaves radiation, which is largely in the form of infrared. Then it stands to reason that if you change how much IR is reflected back to the surface by the atmosphere, say by changing the amount of CO2 in the atmosphere, then you will increase the amount of heat the Earth contains as long as there is a source of heat nearby or within. Earth has both in the form of a molten core and the Sun.

This is why they call them "greenhouse gases." Because they cause the Earth to retain more heat than it radiates in the infrared spectrum, like the glass on a greenhouse.

I'm not having trouble understanding the physics.

CO2 levels are now around 400ppm. During the Cambrian age it was ten times of that at around 4000ppm.

If CO2 levels were so much higher before humans existed, then how did it go down? (My understanding is that plants store it by growing.) And how can we be sure that it is emissions that makes it go up, rather than killing forests that used to store it? Wouldn't it be effective to just plant a bunch of forests in our deserts that store the CO2? California used to be mostly desert, too, but then some guy from Germany came and redirected some water to make it not as much of a desert anymore and that was over 200 years ago.

People have continually been taking significant action! CFCs were banned in 1987. High GWP refrigerants, like R-12 and R-22 have been banned, and even newer ones like R-401 are now significantly regulated: The days of bleeding an air conditioning system to atmosphere are _long_ gone. Cars in developed countries are annually inspected for emissions systems performance, so NOx and other GHG-producers have been cut to nearly 0% from vehicles since the 1990s in those regions. Transoceanic shipping has recently implemented its sulfur-free requirement, and we're visibly seeing fewer sulfuric clouds over the ocean. Stricter gas milage requirements in cars have seen a drop in CO2 emissions in the US from 2007 to 2025 by 102 million metric tons of CO2, despite having 23,000,000 more people.

The Paris accords have been running for years. No country has met its targets but nearly every country has seen a reduction.

The reductions aren't as big as we'd like. The temperature is still rising faster than we'd like. But the idea that we haven't taken any action is completely false.

>Transoceanic shipping has recently implemented its sulfur-free requirement

While probably a good thing for ecosystems, this has removed an unintended "geoengineering" effect. Sulphur dioxide forms a relatively effective reflector for incoming solar radiation.

1. The global temperature has never in human history done what it's doing now. 2. Weather isn't the same as climate. They operate on way different scales and timelines. Uncertainty in the one does not necessarily map to uncertainty in the other. 3. Climate change is most definitely not a solved problem. We know some big things we can do, and none of them are easy.

1. The further back we go, the less reliable the methods of estimating such properties. We only have values for a "global temperature" from the past few years or so.

2. Weather and climate are names for the same underlying nonlinear system. This system is the archetype of a chaotic system - predictions of values and corresponding locations becomes increasingly unreliable and then impossible on larger timescales. Climate modelling was the very thing that lead to our current understanding of sensitive dependence on initial conditions.

1. Sure we have values for earlier periods, estimated through abundant and reliable (in its own way) geologic evidence. But you don't even need to bo back further than 100 years to see how wildly our climate is whiplashing right now.

2. Yes, which is why climate scientists put lots of error bars on their predictions and document carefully the assumptions they're making. To wit, the assumption that we will continue to be as bone-headed about our impact on these systems as we have been. But it is still the case that I have little idea what the weather will be in my back yard in 3 mos but a pretty good idea of what global mean temperature we're looking at in 5 years.

Shouldn't the smaller scale be a lot more easy to figure out? The larger the scale the more variables there are the harder everything becomes.

Nope! C.f. classical mechanics at scale vs. statistical mechanics.

The only thing that matters is that we're pumping insane amount of greenhouse gases in the atmosphere and basically terra forming ourselves and most of nature out of the equation.

Nature is infinitely more complex than most people believe, we don't even know how basic things like soil ecosystems truly works, the thing that supports 100% of life on earth, we have virtually no clue about it, so what do we know about the rest...

Nobody is taking action because the whole system is made for growth and continuous improvement, you can't tell people "we have to work more to simply keep the status quo", let alone "we may even lose a lot of nice things and convenience in the process"

> you can't tell people "we have to work more to simply keep the status quo", let alone "we may even lose a lot of nice things and convenience in the process"

And yet this is what will happen. The question is are we walking into this prepared, or not? Just like a war, it’s unpleasant, most people would rather not do it, but would you rather be on the side that prepared for it or on the side that gets “surprised” by it?

So you are in favor of more defense spending?

How is this relevant to what we’re discussing in this thread?

Lot's of people can't get out of the Hollywood end of the world cliché where the people who survive are the ones with the biggest bombs, they just can't get past the myths we built... Cooperation is foreign to them, and it's a big part of why we can't seem to build anything cohesive past the country level.

> a war, it’s unpleasant, most people would rather not do it, but would you rather be on the side that prepared for it or on the side that gets “surprised” by it?

> Given how we are at the tail end of a small ice age, shouldn't it be expected that temperatures recover to what they were previously?

The speed at which the temperature is increasing is what is concerning, it’s much faster than a usual warming cycle. The XKCD comic of the timeline of human history and climate really drives home how steep the increase in temperature has been vs in the past: https://m.xkcd.com/1732/

> temperatures recover

Not. so. fast.

The little ice age was between ~1300 and 1850. It's now nearly 200 years later and I don't think it unreasonable that, say, glaciers melt faster the smaller they get.

Nobody took action because the global south (logically) decided that economic growth and rising living standards is worth the global cost.

Warming today is because of historic emissions from developed countries. If the global south didn't develop they'd still face climate catastrophe, only maybe 40 years later. And they'd have weaker economies to face it with.

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