What’s the hottest the Earth’s ever been?

Without any knowledge in the field I wonder if the timescale difference could be attributed to the measurement methods used for the last centuries vs literal ages ago.

I.e. if we (or someone a million years from now) tried to estimate the 21th century's temperatures using the same techniques used to estimate temperatures a million years ago, would we be able to detect that 4 degree change?

Conversely, can scientists today detect or rule out that there was an outlier century a million years ago in which temps varied as much as today?

Trouble is most politicians are incentivised to think in the short term and are increasing just in a perpetual campaigning mode. They are thinking about their careers and re-election. They cannot except and talk about bad news, and a 3-5degC increase is bad news.

On top of that you have had climate activists pushing for very large change to happen incredibly quickly (arguably needed). But it’s an incredibly hard sell to the public who won’t except a negative impact on their quality of life.

Basically:

1. People are unwilling to make changes that they perceive as being a net negative to their quality of life.

2. Businesses are unwilling to make changes that they expect to have a net negative to their bottom line.

3. Politicians are unwilling to ask for either of the above to happen because they want to be re-elected.

The thing is that, for businesses and governments, complying with the 1.5ºC goals/projections is already a monumental task. If it does happen, even though it won't be enough, we should at least get an A for effort ... too bad nature is not forgiving.

Anyway, what is still nice is that it should be easier to adapt to 3-5ºC once we're all doing something for 1.5ºC than if we were doing nothing at all, i.e. static friction is always higher than kinetic friction. I think the true covert goal at the moment is to at least get things moving and have everyone jump on it asap.

Source: I build/code software related to sustainability.

Which data sources have persuaded you that the realistic and likely increases of 3 or 5 degrees are more probable?

"In 1979, the Charney Report from the US National Academy of Sciences suggested that ECS was likely somewhere between 1.5C and 4.5C per doubling of CO2. Nearly 40 years later, the best estimate of sensitivity is largely the same. This has led some to question why there has been so little progress on estimating climate sensitivity."

Is this quote above now no longer true? If not, please provide a link.

I can't imagine anything most countries could reasonably do to prepare for 5c, what type of things would you suggest?

Except Biden has stationed troops halfway across the world and if the MIC gets its way, we might get to pre 1800 levels of temperature, so, thanks Biden I guess. Let's go Biden

Yes, the article acknowledges that but also makes the point that it's not interesting from a human perspective.

"None of these techniques help with the very early Earth. During the time known as the Hadean (yes, because it was like Hades), Earth’s collisions with other large planetesimals in our young solar system—including a Mars-sized one whose impact with Earth likely created the Moon—would have melted and vaporized most rock at the surface. Because no rocks on Earth have survived from so long ago, scientists have estimated early Earth conditions based on observations of the Moon and on astronomical models. Following the collision that spawned the Moon, the planet was estimated to have been around 2,300 Kelvin (3,680°F)."

"Even after collisions stopped, and the planet had tens of millions of years to cool, surface temperatures were likely more than 400° Fahrenheit. Zircon crystals from Australia, only about 150 million years younger than the Earth itself, hint that our planet may have cooled faster than scientists previously thought. Still, in its infancy, Earth would have experienced temperatures far higher than we humans could possibly survive."

"But suppose we exclude the violent and scorching years when Earth first formed. When else has Earth’s surface sweltered?"

Our Sun probably ate a planet thereby disrupting the solar cycle.

There's like... six millibars of pressure on mars? Admittedly almost all of those six millibars are CO2, but still. Turning all that into O2 might still not support ~photosynthesis~ bootstrapping plant life, let alone humans breathing.

Edit: also sorry to be a party pooper but I studied organocatalysis for a while and you must understand that these research papers about catalysts are almost always so incredibly far away from industrial viability. The ligands take long to prepare, the metals are expensive... and whilst these things might be solvable with enough money, the fact remains that they have turnover numbers that are finite.

(The TON is the amount of substrate the catalyst can transform before becoming deactivated)

Even with a TON of 1.000 (paper quotes < 10) you'd be able to produce 1.000 moles (32 kg) of O2 from one mole (has 100 g Ru, 2000 USD) of this expensive ruthenium gizmo. Oh and it's an electrocatalyst so better get some planet-scale power generation in place, first.

First we would need to create a huge magnetic field protecting Mars from the solar wind that has blown away the atmosphere Mars previously had.

https://www.sciencefocus.com/space/how-did-mars-lose-its-atm...

https://astrobiology.nasa.gov/news/how-to-give-mars-an-atmos...

I wonder if terraforming is possible, not because of technological limitations but just because of the limitation of humanity's ability to execute such large scale projects.

Given an unlimited amount of raw materials and energy, terraforming a planet like mars would probably take decades (centuries?).

Private funded projects usually have a TTL of a couple of months to at best 4/5 years and are driven by short to medium term profits. Public funded projects are on a longer timeframe. Taking a recent example, according to Wikipedia, "serious planning" for James Webb started in early 90s. So that's ~30 years.

But do we have example, in modern times, of project lasting more than a century? I have Notre-Dame in mind, any other? The construction of Notre-Dame was driven by religious fervor. I wonder if we could muster the same amount of will based only on a profit motive.

Perhaps we'd better make sure we try to terraform Earth, as it's much closer to being liveable, than Mars.

Colonizing Mars is like the whole 'I can't bother to learn Bash, so let's rewrite our whole app to Kubernetes in next 5 years' thing. A procrastination.

even if we could generate oxygen, isnt the gravity on mars not strong enough for normal human development?

That's a relief. I'm old enough to have gone through the 1970s global cooling scare stories https://en.wikipedia.org/wiki/Global_cooling

Yes, we live in a relatively cold era in the history of our earth. It’s a great, very informative article.

The efforts are to reduce the degree of change. Full on stop is not likely at point. Adaptation will be even more expensive, but we still get people complaining that efforts to head off climate change are too expensive.