/sci/ - Science & Math

>>4166345

You mean 5 degrees in a hundred years?

That's the difference between today and the middle of a glaciation and New York under a mile of ice. Except in the opposite direction.

http://journals.ametsoc.org/doi/abs/10.1175/2009JCLI2863.1

http://globalchange.mit.edu/resources/gamble/

>>4012120

>What information do you base this on? What effect(s) do you think global warming will have that we can't adapt to?

Well, let's go with the hypothetical zero-mitigation, all-adaptation scenario. This means continuous business-as-usual emissions patterns until the global economy is wiped out or all fossil fuels become uneconomic to extract. CO2 concentrations breach 1000 ppmv, while CO2e is 1200 ppmv or higher.

The mean projection for temperature at this level is 5 degrees Celsius of global average surface temperature increase above 1991-2000 levels, or about 6 degrees above preindustrial temperatures, by the year 2100.

Last time the Earth was anywhere close to this hot was the Eocene "hothouse." Let's look at only the most obvious impact. No ice caps on either pole, so sea levels would rise 80 metres eventually (plus 10 or so metres with thermal expansion), but "only" 1-3+ metres in the first century. Now, unless you know of a fabulously cheap way of constructing tens of thousands of kilometres of flood defenses and seawalls, you're looking at inundating cities with populations totalling several hundreds of millions.

What is the adaptation cost for moving entire cities inland? Conventional economic estimates don't even try. The Stern Review estimated an average of 10% of global GDP per year would be lost on adaptation and damages, but figures exceeding 20% could not be excluded, and it extended into the indefinite future. By contrast, the most pessimistic cost analysis of mitigation was 4% of GDP over about half a century, while most other estimates placed it at 1.5%.

Just entered the thread, so I apologize if I missed something that was already mentioned.

>>2452583

>Climate change in all probability will cause a 1.5 C increase in global temperatures by 2100 (IPCC, 1995).

>1995

Shit's outdated yo

Here's the most up-to-date projection for temperature change by 2100 under business-as-usual. 5 C increase is now a strong possibility.

http://globalchange.mit.edu/resources/gamble/
http://journals.ametsoc.org/doi/abs/10.1175/2009JCLI2863.1

And the guy you were arguing with was correct. The last interglacial was 2 C warmer than the temperatures that predominated during the current interglacial. Not that this is any cause for celebration, current changes are occurring much faster. Sea levels were something like 20 m higher back then.

Also, do you have links for the Huey papers and the Mitchell paper? I'm not exactly sure which ones those are supposed to be.

>>2230507

So far we've only experienced an increase in 0.8 degrees C in global average temperatures since the instrumental record began. There's a 1-in-11 chance that we could exceed 7 degrees warmth by 2100 under a do-nothing policy. This sort of change has not been experienced on Earth since the dinosaurs were killed off 65 million years ago.

http://globalchange.mit.edu/resources/gamble/

>>1328763

Also note that in the Met Office projection, the "rapid but early decline" scenario still "locks in" over 2 C of temperature increase by 2100. That scenario is now physically impossible to accomplish as 2010 has ended without much significant movement towards action.

Another projection from MIT:

http://globalchange.mit.edu/resources/gamble/

From the business-as-usual projection, we see each pie slice representing the probability of different ranges of temperature increases by 2100. Compared to the Met Office projections, we see better the various probabilities of the projections. What's important to note here is how increases of >5 C are disturbingly likely. At this level in the past, mass extinctions occurred.

>>1284137
>>1284176

Maybe it's pretty unlikely as things stand now, but there are a lot of uncertainties about how soon positive feedbacks start kicking in. Even if something like a repeat of P-T seems very unlikely now, we don't know how bad things could get a century or two from now. Of course, that brings us out of the realm of the impacts with much greater certainty which should be alarming enough on its own.

I'm mostly basing my presumption that a mass extinction event might occur based on the MIT Greenhouse Gamble project. If by 2100, we really do hit a 6 C anomaly, that will be the fastest change the Earth has ever gone through short of an asteroid impact.

>>1224513

Uncertainty should be a motivator for more substantive action. We don't know for sure how much worse it's going to get, but it's very likely to be extremely bad. It might be only "very bad," but it might also be "catastro-fuckingly bad." If we, say, trigger a mass extinction event (which some scientists argue is actually occurring right now), we would have made the wrong choice. Observe this projection "roulette wheel" for 2100. If you hit above 6 C anomaly, we could end up triggering the same kind of mass extinction as the P-T event.

On the other hand, land-use changes, energy efficiency, technology grants, ending fossil fuel subsidies - all these things are doable and technologically very feasible. The main obstacle is political. Carbon taxes and cap-and-X schemes are recommended only because the world is so market-oriented that we don't want to try actually being serious about climate change. If we did get serious, we wouldn't regret it. In fact, ending fossil fuel subsidies, deregulating nuclear, and energy efficiency are all money-SAVING or -making reforms.