I was halfway through my post when I reworded it to avoid this point. Not really sure how hn likes the doom talk yet, but seeing as you brought it up.. I watched a ted talk a while back where the speaker basically laid it out like this:

2 degrees c = screwy weather patterns, extreme storms

4 degrees c = sea level rise, no real seasons anymore, just a big swinging mess from extreme drought to extreme storms

6 degrees c = mad max

8 degrees c, he basically said humans were long gone at this point.

Remember, 1 degree average = massive localised changes.

Hmm now that I've written all this, I'm not sure, were you speaking in celsius or fahrenheit?

edit, specified celcius, also I think this may have been the guy but not quite the same talk https://www.youtube.com/watch?v=pznsPkJy2x8

I would place a bet that at 5c rise they still would let all the behaviors in the USA that are causing the warming to continue.

Because the corporate lobbys would insist "jobs jobs jobs" even while the Florida keys would be completely under water - all the ceos and politicians would just literally sit in their towers and keep voting to continue.

I was talking Celsius / Kelvin. I'm assuming the speaker was referring to Fahrenheit - I'm thinking mankind as a whole might be able to survive +8 degree K iff we find efficient synthetic food sources that work in such a climate (which I assume we will) - however it would probably be at a fraction of the population we have today - whether our civilization could survive an indirect genocide on a global scale to have the infrastructure to do this is another question.

edit: re your edit: if it's true that +6 degrees sets perpetual heating mechanisms in motion which lead to +12 degrees by 2300 (as suggested in the ted talk), yes, we probably wouldn't survive +8 in the long run. it's damn scary, really - if we screw this up in the next 20 years, we basically damn the whole planet.

You mean, mankind might survive +8 degrees F (about +4.5 deg celcius)

I meant Celsius, but see my edit - I have to revise that guess. Given that +6 degree C will probably cause runaway warming processes to initiate (which I wasn't thinking about before), surviving for even a few more centuries suddenly becomes a tough order.

> The most recent studies suggest one degree of warming per decade on average

There's been a total of approximately 0.8 degrees C increase in temperature since about 1880, at about 1.5 degrees C per doubling of CO2 concentration. Although part of that increase may be due to the increase in solar activity over the period. And, it hasn't gotten any warmer since 1998.

I'm no big proponent of fracking, but in general peak oil/gas is a much more pressing issue than global warming. I'm pretty much convinced at this point global warming is just a front used to push anti-peak oil policies.

So, you're sitting in a car driving 100mph towards a wall. The car's safety system warns you, saying 'collision ahead, break NOW'. You're thinking "hey, no problem, no car since 1880 has driven into this wall, it must be a hallucination - I'm keeping my foot down baby".

Analogies used here:

The car - Energy policies

The safety system - Climate models

The warning - Result of these models

You driving into a wall - Laymen's opinions about why these models don't apply.

To put it differently:

1) There's a time delay of several decades between putting out the CO2 and temperature rise. What we're feeling now is the effects of energy policies in the 60ies and 70ies.

2) Since the 70ies our CO2 output has risen considerably, mainly due to emerging markets.

3) Most of this 0.8 degree warming you're talking about has occurred in the last 30 years.

Well - would you bet on the wall being an illusion, or would you rather brake just in case?

If my car's system had the same track record and fundamental flaws as the climate models commonly cited, I would be inclined to ignore it. By track record I mean predicting a 3 degree C increase per doubling of CO2 and experience showing only half of that. The fundamental flaw is the assumption that positive feedback effects will triple the 1 degree C per doubling CO2 greenhouse effect, when these feedback effects (clouds and water vapour) are so difficult to model correctly.

Pretty sure the time lag of decades for temperature increase is simply false. Most of these models were predicting temperature increases since 1998 which haven't happened.

Finally, I probably would consider not braking at all if I couldn't possibly come close to stopping in time to prevent a fatal impact. If you really think a 3-6 degree C temperature increase is coming, the only thing that is going to do anything is something like a 50% drop in fossil fuel consumption. The world can't even agree on a 10% cut that won't do anything. EDIT: That's why I think these are really anti-peak oil policies, because a 10% cut actually helps there.

I see where you're coming from. When it comes to climate models, lots of feedback loop, both positive and negative ones, are being thrown around - you can basically adjust models arbitrarily to your political liking. Adjusting these models to real data is a never-ending process as long as we don't have the computational power to both resolve much denser grids and timesteps and include more parts of the equation than we do now. However, when it comes to balancing these things out to give an accurate prediction, I tend to trust organizations like NASA, IPCC and NOAA over the typical right wing think tanks that you see throwing together these denialist reports. Yes, we do know about negative feedback loops, the scientific consensus is just that they're much weaker than what we're doing to the atmosphere. Also, the 1998 measurement that gets thrown around is very misleading - have a look at [1].

Noone is claiming these models are perfect and the temperature increase estimates may be off by some margin - all I'm saying is that as long as we're sure current CO2 levels aren't going to kill our future, we better stop increasing them, given scientific consensus. When the doomsday scenarios come from scientific studies and stop including low probabilities, it's better to take them seriously rather than bet our home planet on them being all wrong.

[1]http://www.nasa.gov/topics/earth/features/upsDownsGlobalWarm...

I don't trust the IPCC because the actual results haven't matched their models, regardless of what the "scientific consensus" is on negative feedback loops.

And again, stopping the increase of CO2 would require massive global emissions cuts, which would require a new energy infrastructure.