And the Earth will be just fine after us humans have ceased to exist. As humans I think we should be concerned just a little.

Humans don't start to show negative effects until the CO2 level in air reaches at least 2,000 ppm (and some won't show any effects until about 5,000 ppm). That's around 4 times the "threshold" that the article is concerned about.

Humans will also be fine.

Yes, we'll be safe from the direct effects of CO2 increases. But the indirect effects could be much more severe. That's the interesting part of the problem, we don't have accurate models of all the side effects. Ecosystems are complicated and fragile.

"But the indirect effects could be much more severe."

Or they could make things better.

"That's the interesting part of the problem, we don't have accurate models of all the side effects."

In fact, we do know that the CO2 level of the earth's atmosphere has been much higher in the past, and that this didn't produce anything like the "all life on earth dies" scenario that the doomsayers keep touting.

"Ecosystems are complicated and fragile."

The ecosystem survived the Chicxulub event, dude. It's not going to be knocked out by 410 ppm of CO2.

The ecosystem did not survive the Chicxulub event.

"Ecosystem" is not shorthand for "life exists on Earth somewhere." An ecosystem is a particular state of the dependencies between life forms.

The ecosystem that existed before the big asteroid strike was thoroughly and rapidly destroyed; a new ecosystem developed afterward. That's fine from a general "life finds a way" perspective, but it sucked for the sauropods, who went extinct.

EDIT: if you want a sense of why the indirect effects of anthropogenic climate change might be bad, look at the social unrest reacting to a couple million people migrating out of Syria. What do you think it's going to be like when about a billion people have to migrate inland due to sea level rise?

By your definition "the ecosystem" never "survives", because it has been in a state of constant change since life first developed on earth.

"What do you think it's going to be like when about a billion people have to migrate inland due to sea level rise?"

Considering that even the worst-case doom-crying scenarios issued by the IPCC predict a sea level increase of the order of 1 meter over the period of a century (i.e., ~1 cm per year), your (and Hollywood's) suggestion of rioting mobs fleeing the tsunami-like rising ocean is just not based in reality.

Yes, ecosystems change constantly. An ecosystem is a state and the state changes as its components change.

The fact that this is news to you is a clue that perhaps you know less about this subject than you think you do.

Now you're just getting nasty, without any substantive response to my assertions.

Hint: that means I won.

You claimed that the ecosystem "didn't survive" the Chicxulub event because there were different organisms afterward. I pointed out that by that "definition" the ecosystem has never "survived", because it has been in a state of constant change since day one.

Rather than responding to this, you just got nasty.

I repeat: I win. Sorry.

I did respond: I said that you are correct that ecosystems are always changing.

The question is, what do those changes mean for individual organisms? Because that's what you and I are.

Changes to the climate and ecosystem are like changes to velocity. Whether the change is good or bad for people depends on the magnitude and direction.

I do think that your focus on who is "winning" an imaginary Internet slap fight is detracting from your understanding.

I think the "all life on earth dies" scenario is mostly a straw man. I mean, I'm sure there are some people speculating about such things and making comparisons with Venus, but so far as I can tell the overwhelming majority of people who are concerned about climate change are worried about much more modestly-bad scenarios.

So. Yes, the CO2 level has been much higher in the past. For instance, in the Cambrian period it was much higher than it is now. ... And, in the Cambrian, the surface temperature of the earth was about 7 degrees C higher than it is now.

As someone else remarked: no, "the ecosystem" did not survive the Chicxulub event. Life survived it, sure, but it wiped out the dinosaurs (other than the birds). That's kinda a big deal.

Let's be honest. Climate science also needs to decide if it will be anthropocentric or not. As harsh as it sounds, if science is not supposed to be anthropocentric, then it doesn't matter to science if humanity becomes extinct or suffers. By definition. So if climate science is going to make human suffering or survival the key important issue, it should completely discard any language that it's about the earth and environment, and discard any pretense that it's not trying to be anthropocentric.

Science is the process of learning how the universe works. It is not anthropocentric.

What we choose to do with that knowledge is anthropocentric because we are humans.

Science can tell us how fire works. We still have to decide what to do when our house catches on fire.

I'm being pedantic, but what to do with the knowledge seems to be a policy and political question, not a science question.

I agree.

>all of the carbon in fossil fuels used to be in the atmosphere... The earth was just fine.

A problem with that argument is that the sun was about 20% dimmer back then. Hence it may get hotter this time around.

> the sun was about 20% dimmer back then

According to wikipedia[1], the Sun increases in brightness steadily about 1% every 100M years, yet we had CO2 levels 10 times higher than now about 500M years ago.

[1] https://en.wikipedia.org/wiki/Solar_luminosity