HN Reader

The last IPCC report estimates that to limit warming to 2C, humans can only emit at most 1150 GtCO2 (at 67% likelihood) [1].

There are 8.2 billion humans, so about 140tCO2/person left on average. If we assume that we get to net zero by 2050, that means the average person can emit about 5.4tCO2/person/year from today to 2050 (hitting 0tCO2/person/year in 2050). This is what emissions look like currently [2]

    Top 5 countries > 10m population
    Saudi Arabia  22.1t 
    United Arab Emirates 21.6t  
    Australia            14.5t 
    United States  14.3t
    Canada          14.0t
    Some others
    China           8.4t
    Europe 6.7t
    World average 4.7t
    Lower-middle-income countries of 1.6t
    Low-income countries 0.3t

Guess what's going to happen and who is going to suffer, despite not doing anything.

[1] Page 82 https://www.ipcc.ch/report/ar6/syr/downloads/report/IPCC_AR6...

[2] https://ourworldindata.org/co2-emissions-metrics

Looking into the numbers a couple if months ago I was surprised how little it costs to stop climate change.

On the order of 100-200 trillion USD. Which is roughly 100-200% of global yearly GDP. Or 2-5% of yearly GDP until 2050. This could well be provided by printing money at all the federal reserve banks.

This investment will likely bring in a positive return on investment because it reduces the negative climate impacts.

Without such investments the downstream costs in climate change adaptation will be very expensive

The Earth is a complex system.

Warming is one aspect of climate change, but we'll likely see cascading effects in the system.

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For example, as global temperatures rise we are seeing that AMOC (Atlantic Meridional Overturning Circulation), and as a result the Gulf Stream, are "slowing down". [1]

This could result in EU cooling down.

The clathrate gun hypothesis suggests that large releases of methane could cause abrupt climate shifts due to methane’s strong greenhouse effect. [2]

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Its likely developing nations and their citizens will increase CO2 usage as they move towards a more western lifestyle.

That means there will be an increasing amount of energy production and usage.

Ideally we generate more with solar and nuclear.

Decreasing energy production and consumption is not a real solution.

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[1] https://www.nature.com/articles/s41467-023-39810-w

[2] https://en.wikipedia.org/wiki/Clathrate_gun_hypothesis

Long-term should be defined. We can cool the planet the same amount long-term. Why is it taken as a given that any warming is irreversible when we have historical natural patterns showing global cooling (ice age)?

Doesn't seem like there is any foreseeable future where climate change can be addressed. It's not just the leadership of the u.s, but the citizens themselves reject climate change as a real issue. Hopefully I'm just being pessemsitic.

It feels like we're getting much more than 1.5 degrees. Here in NYC it used to snow several times a month, we've had one tiny storm the last two years. Just 20 years ago I rarely used AC in the summer, now its on nearly every day from May to September. Its not just that the temperatures are more variable, and the rainfall patterns are much more random it really feels like we're at +4 degrees already.

Call me pessimistic but I don't think anything is going to change and a lot of people are going to die due to climate-forced migration.

That being said, it's a difficult topic to discuss rationally. Part of the issue is deciding on what your baseline is. Looking at the last 200 years tells a pretty limited view. Consider around 100,000 years ago when global temperatures were similar [1].

That raises some questions about what caused that spike but, more importantly, what caused it to lower. You can say "an ice age" but what really triggers an ice age?

My point here is that doomsday predictions of Venus-like runaway inflation I think are both unrealistic and unhelpful in actually motivating people about an otherwise very real problem. We really have no idea of the mechanics in place.

But like I say, we're going to do absolutely nothing about it anyway.

[1]: https://www.pbs.org/newshour/science/analysis-is-it-actually...

Don't take me wrong, I'm not in the denial camp, quite the opposite in fact. But I cringe when I read a non sequitur like this:

> “If you plot global temperatures against the concentration of CO2 in the atmosphere, they both fall on a remarkably straight line, much straighter than current theory would predict,” said Dr Jarvis. “That line tells you not only how much the Earth has warmed since pre-industrial times, but also how much of that warming can be blamed on human activity.”

How can a straight line tell us anything more than a mere correlation between the two measures, without any hint about which is the cause and which is the effect?

I remember about 20 years ago I was pretty entrenched in circles of thought that were not quite "denialist" so much as they were "it's not gonna be as bad as they say it is-ist". I remember a prevailing line of thought was that climate "alarmists" only chose the most extreme predictions of the various models in order to sell the urgency of acting quickly to stop it. There were those that said that the most extreme predictions came from models that emphasized positive feedback loops (like arctic permafrost thawing), and ignored or de-emphasized negative feedback loops (like increasing vegetation growth rates). And above all, I remember one particular number standing out as where they thought we would plateau. It was at 1C of warming arriving around 2030.

Whoops. Maybe the scientific consensus should be listened to more often, and the fringe less often.

Title:

> Humans have caused 1.5 °C of long-term global warming according to new estimates

First sentence of the article:

> humans may have already caused 1.5 °C of global warming

Our response to a global pandemic was a disaster other than getting the vaccines made. The most recent large scale collective effort to defeat an existential threat prior to that was probably WWII. We’ve gotten pretty good at waging war but I fear that’s probably where our evolution in the matter of dealing with existential threats will probably remain.

With USA going full climate denial in next 4 yrs and SCOTUS packed with O&G friendly judges. It’s going to get worsw

The simple reality is that humanity is unable to reduce greenhouse gas emissions without an alternative that is superior.

For every ton of CO2 that the west has reduced in the past decade China has produced three tons of CO2.[1]

We need another breakthrough on the scale of the Haber process.

[1] https://ourworldindata.org/explorers/co2?country=OWID_WRL~Hi...

Governments won’t act. The best you can do to help with the climate crisis is to have one less kid than what you wanted to have.

Since this is the most important and urgent topic humanity should be working on: why isn’t this the case? Idiocracy is here. Don’t look up.

We have to throw everything into the race. But how to do this with the current inner workings of our societies? How to overcome greed? What about the power of (social) media? Why do we have Netflix and so on? How can we make people spend their time solving climate crisis, saving our planet earth?

This article spends a lot of time worrying about which baseline to use as that determines how much global warming has occurred. Which is important because the 1.5 C limit was raised in the Paris accords. But wouldn't the measurement be absolute. The 1.5 increase is just because that was the baseline they used then.

No, we have caused AT LEAST 1.5°C long-term global warming.

Sure, but let's keep voting based on culture wars and the new satanic panic.

Wasn't it just a week ago we discovered that widely used models were significantly underestimating CO2 absorption by plants?

I think we'll blow through these limits. Humanity has never ceased to disappoint me.

Genuine question to experts: what could be the positive contribution of agriculture on this and exactly how?

I care far more about pollution than carbon in the short and medium terms but focus has completely been dissolved from that in the interests of the big carbon grift. It's all a scam for large institutions to rake in more money and not fix the problems. So many people in this thread are putting the entire onus on the US but giving passes and ignoring the real problems like China who don't even bother to follow or participate in climate solutions.

Asking sincerely because I'm not well-versed on this topic - do we have actual proof that humans are causing global warming?

My understanding is that the climate will change independently of human activity. For example, we know that there was an Ice Age and it was not ended by human activity but rather natural processes. So the climate has been known to change historically without human involvement.

So here is where I'm looking for clarification: I thought the "controversy" over climate change was the degree to which human activity is accelerating a natural process of warming?

Said differently, the planet is warming by itself, but humans pumping hydrocarbons and other things into the atmosphere is speeding up that process. But the cause is not solely because of human activity.

Thanks in advance for thoughtful responses, I'm really just trying to learn here.

At the scale we've hit, I fail to see how anyone except billionaires, mega corps and investment funds can solve this problem. The economic incentives aren't there yet without pumping billions of dollars into the problem without a financial return.

Governments have clearly failed, and several corporations have won their plays to become more rich and influential anyway in many countries.

I don't doubt that humans will continue to survive on this planet if all the worst predictions come true. Many other species won't be so lucky, which is a shame. We have all the technology and power to be caretakers for our home but we just trash it anyway.

That seems… very low?

All the people who usually make a big deal out of this usually oppose density and reducing car dependence. Degrowthers always seem to assume that the only job worthwhile is “guy writing meta-analysis paper” and “coffee shop”. They ally with groups that protect golf courses and oppose geothermal energy and nuclear energy.

So it’s fine. We’ll tech our way out of this without them. If we don’t, we die. So be it.

We are on the natural rise after a natural ice period. Just check long term temperature curves and stop looking short term, making it look like there has ever been the same average temperature on earth.

Enjoy the warmer weather.

Does the IPCC account for asphalt expansion (added heat) around all the airport sensors as cities expand? What data source do they use to track and compensate for this growth?