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Comment by kbutler | Hacker News Reader

Skimmed parts of it.

Read this bit:

"""

    Right now, we are at net positive emissions. Every year, we add more CO2 to the atmosphere. Even if we reach net zero emissions by 2050, we’ll keep adding more greenhouse gases to the atmosphere for 30 years. Thus, we’ll keep increasing the rate of heating. Even in 2050, the planet will continue heating up - faster than today, but at net zero, the rate will stabilise.

    Imagine a car on a super long path2 that ends in a cliff. We are pushing this car harder and harder, which makes the car keep going faster and faster. We will continue pushing for 30 years, and when we stop, the car will continue going at its current speed. This roughly translates to the car falling off the cliff. It doesn’t matter how long the path is, we will get to the cliff.

"""

This view that a given CO2 level determines a rate of global heating does not match any scientific view of the greenhouse effect of which I'm aware.

View on HN

Yeah I got to that, too, and it's not correct. A given CO2 level basically determines the temperature at which the Earth will be in net radiative equilibrium between heating and cooling.

The Earth can't simply continue heating up until the oceans boil and the rocks melt because the CO2 level has gone up a bit. That would only be possible in the presence of a very strong positive feedback loop that made the Earth better and better insulated the hotter it got, which would be unlike any other thermal system we know of.

Edit: there are some positive feedback effects, like water vapor being a greenhouse gas, that will likely make the end result hotter than that expected based on the change in CO2 alone, but it will not lead to heating just continuing indefinitely.

Isn't there a bunch of methane trapped in icebergs or something?

I'll be honest, I'm convinced humans have a big hand in climate change, but I can't seem to determine whether I merely need to lobby my rep for green legislation or start taking survival classes for an impending collapse of JIT supply chains and society in general.

You're right, there is time of methane trapped in permafrost. Those are melting now and realising the gas.

Lobby for green legislation. We need to influence politics to finally act in a serious manner. As we accomplished with the ozone hole as mentioned in the article

https://climate.nasa.gov/news/2785/unexpected-future-boost-o...

He's either confused or has trouble expressing himself.

If human CO2 emissions stopped, atmospheric temperature would still go up for a while (perhaps decades), because of thermal inertia - for instance, the oceans haven't fully warmed to equilibrium, so they currently have a cooling effect on the atmosphere. There could then be some further increase in atmospheric CO2 because warm water holds less CO2 than cold water. There could be other positive and negative feedbacks (eg, higher CO2 and warmer temperatures may increase plant growth, sequestering CO2.)

It's very unlikely that any of these feedbacks are of the "runaway" variety, because if that's how the earth worked, it would have become uninhabitable long ago, since there have been various temperature shocks over the last billion years or so that haven't lead to this fate. (If there were really "runaway" feedbacks, it wouldn't even take a big shock - the tiniest change would be amplified and push the climate into either extreme heat or cold.)

> a given CO2 level determines a rate of global heating

This IS the greenhouse effect. Increased levels of greenhouse gasses result in a warmer planet over time as Earth reflects less solar energy back into space. This warming leads to many known runaway feedback loops: increased wildfires that release more CO2 and destroy natural carbon sinks, reduced albedo from ice melt, increased moisture in the atmosphere, warmer oceans leading to less carbon sequestration by phytoplankton, methane release from ice melts.

There are more. Please read some recent literature to understand this better than anyone can summarize on HN. I recommend The Uninhabitable Earth

It's just slightly badly worded. They're saying that we won't stop emitting until 2050, so until then we'll be heating, because a given CO2 level (assuming it is static e.g. no feedback) determines an equilibrium temperature.

> at net zero, the rate will stabilise

should read something like; at net zero [emissions], the temperature will stabilise.

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