Honest to God, they think we’re happy about this.
WE DIDN’T KNOW WHEN IT WAS GOING TO HIT THE FAN
But I’m very sad and worried that we might know now.
See there are a bunch of questions. Let’s do a Q and A. I’ll ask the questions in the right order, and then I’ll answer them. See if things come a little clearer as a result, and let me know.
HOW MUCH OF THE CARBON STAYS IN THE AIR?
First, despite odd year-to-year variability on WHERE the carbon seems to be going, the amount that stays in the atmosphere seems a relatively constant fraction. For big picture approximation, a half is just fine, though some argue it might slip to three quarters.
HALF THE CARBON WE EMIT STAYS IN THE AIR PRETTY MUCH PERMANENTLY ON POLICY TIMESCALES.
WHY DOES THAT MATTER?
I think everybody agrees that until the Great Bush Economic Glitch, (and let’s call it by such a name, please) this amount was increasing rapidly, and there is enormous pressure, especially in China and the US, to get this back on track. Anyway, the amount we dig up out of the ground and spew isn’t going down much. And because carbon doesn’t really go away on the time scale of human lifetimes, the amount in the atmosphere keeps growing, and roughly speaking, will keep growing until we stop emitting carbon altogether.
SO IS THAT ACCUMULATING, LIKE, ALOT?
“A lot”. Two words, there, dude. Pet peeve. You get allotments, I get allitlements, and you end up allotted with a lot. Anyway…Carbon accumulates, as do other greenhouse gases, but let’s assume we can at least get a grip on those. But those others make matters worse. Either way the upshot of what ALL the economists tell us is that if we work really hard, we can, if we try really hard, limit the damage at the point where we get just shy of a doubling of preindustrial CO2, if you count all the other greenhouse gases as if they were CO2.
ACCUMULATING CARBON DIOXIDE AND OTHER GREENHOUSE GASES ADDED IN AS EQUIVALENT CARBON DIOXIDE IN THE ATMOSPHERE WILL AT THE VERY LEAST BE ALMOST THE EQUIVALENT OF DOUBLE PREINDUSTRIAL CONCENTRATIONS. (WHICH IN TURN WERE QUITE HIGH COMPARED TO THE MOST RECENT 3 MILLION YEARS. SO THE EARTH IS AT LEAST TEMPORARILY ENTERING A RADIATIVE REGIME WHICH IS LITERALLY WITHOUT PRECEDENT.)
UM, WITHOUT PRECEDENT? SO MEANS THATS GONNA WARM US UP AL… ER, A GREAT DEAL, RIGHT?
No, hang on. I knew we were gonna jump the gun on this “global warming” thing,So there’s a lot of attention to Global Mean Surface Temperature. A lot of it is greatly overvalued. I think this is because of the dreadful misnomer “Global Warming”.Yes, we are warming but that isn’t really the point. That’s inside baseball. The thing that the general public should understand is we are monkeying with the whole climate, not just the temperature.The globe, which is to say, the surface of the earth, is indeed warming, and that is indeed as a result of greenhouse gas accumulations (and somewhat counterweighed by dust form pollution).
But the cartoon version, that it is a direct result, leaves a lot out. We hear people saying that “global warming is gonna cause HUUGE CHANGES in the weather” but that is causally all screwed up when you really look at it. Aerosols change the pattern of incoming energy, and greenhouse gases change the pattern of outgoing energy, and the land surface is also changing more and more rapidly in various places. We are kicking around the only home we have in the universe as if it were an old tin can. One of the things that happens when you kick this can in this way, we are pretty sure, is warming. But the can never warms that much without a whole lot of other crazy stuff going down. You don’t just hold a match to it. You change where the energy comes in and where it goes out. The whole engine of climate is to move the energy from where it comes in to where it goes out and we are changing THAT.THE HUGE CHANGES WE ARE MAKING IN THE CLIMATE ARE GOING TO CAUSE GLOBAL WARMING
There are a bunch of reasons, some good ones and some really terrible ones. A lot of confusion comes from the fact that people insist on calling the problem “global warming” and not “climate change”. In fact, just to make things clear, I’m not going to say “global warming” again after this paragraph. The words “global warming” confuse and obscure. If I’m going to talk about the surface of the earth warming on average, I’ll talk about increasing Global Mean Surface Temperature or “increasing GMST” or if I’m feeling particularly geeky, “++GMST”.But it’s also the fact that, left to its own devices, the global mean surface temperature is extremely stable. One place may have a cold year and another place may have a warm year, but the world pretty much stays the same temperature. Now that is only relatively recent. It’s only been like that for ten thousand years. But if humans hadn’t come along, the signs are the happy animals would be having a long break before the next ice age would kick in. Because the ice sheets have settled down, because the orbital forcing is in a very moderate part of the cycle, and because the sun is calm and stable these days, and because there haven’t been any asteroids or supervolcanoes, the climate was able to settle down. And once it settled down, its temperature became almost solid as rock, like Uncle Sam’s pulse, constant, unvarying. The energy was coming in and going out at the same rate, year after year, decade after decade, century after century. The ocean sloshed around enough to move mild hot spots from one place to another on longish time scales, but the average seems to have been very steady.So things have stayed the same until pretty much the last few decades, but they’re starting to drift. Pretty much in exactly the way that was predicted by a conclave of the world’s best meteorologists and oceanographers in 1979.So if things start to drift, it isn’t because the climate fairy went around the world giving an extra 0.7 degrees C to every town and village and keeping the weather the same. It’s because the weather is changing that the system can find a new temperature. Climate change causes increasing GMST, not the other way around. So one of the reasons we study GMST is because it gives us a measure of how much the climate is changing.Think of taking the planet’s temperature as being, like, seeing how bad a fever the earth has.INCREASING GMST IS A MEASURE OF CLIMATE CHANGE
LET ME GET BACK TO THIS ONE, AFTER WE TALK ABOUT HOW MUCH WARNING WE’RE GOING TO GET
THE QUESTION HAS TWO PARTS. THE FIRST PART IS WHAT THE SENSITIVITY IS.
Climate sensitivity. Actually, that has a bunch of meanings, and I suspect that’s why Lindzen and Spencer keep managing to get the answer they want. What we usually mean is, what’s the number that connects CO2 radiative forcing to temperature change.Now for various technical reasons, it’s usually stated as equilibrium change in GMST per CO2 doubling. There are reasons to expect that that number is roughly the same, no matter where you start the doubling from, over a broad enough range to cover what humans could ever possibly do.And we think we have a good grip on this number. It’s probably between 2.5 C and 3.0 C per doubling, pretty much certainly between 1.5 and 5 C.Now this number does sweep under the rug the problem that we may jostle the system enough to inadvertently release natural carbon too. Methane deposits are especially scary because there is a lot of methane, it causes a lot of greenhouse effect, and when it finally breaks down its carbon ends up as CO2 anyway, to plague us approximately forever. Fortunately, this looks not to be fast enough of a process to change the picture too drastically. That’s not a lock, though. Let’s hope it holds up.SO IF CO2 DOUBLES, WE’RE LOOKING AT A WARMING OF AROUND 2.5 C, GIVE OR TAKE
A couple of years ago, it looked like we would run out of fossil fuels pretty soon, but there’s been a huge burst of invention. There are various deposits around the world that nobody would have dreamed of touching a few years back that are now online and producing at scale, notably tar sands and nonporous rocks. So at this point it’s hard to come up with a constraint on natural gas or coal, though petroleum itself is getting harder to find. Now some people think that is a showstopper, but I don’t see it. It will drive up the price of gasoline, so electric cars and trains will replace cars and trucks. The question is mostly where we get our electricity.And basically, between the day we decide to take this problem seriously, and the day it stops getting worse, there’s probably about forty years.Deciding to take the problem seriously mostly has costs immediately and benefits decades in the future. This is why it is an ethical problem. And it gets more and more expensive to deal with the longer action is delayed. The increase in technological prowess will have a very hard time even keeping up with the increasing population, increasing demand, increasing dirtiness of the remaining fossil fuels, and increasing climate impacts on aggregate wealth. Those who insist we delay while progress gets us further are asking us to bet the farm on an inside straight.So, we could be looking at anywhere from double to eight times CO2 by the time all is said and done. Maybe more but nobody even has the remotest idea of what life would be like at 16xCO2. The good news, I suppose, is it would promote space travel.WE COULD BURN ENOUGH CARBON TO PROMOTE SPACE TRAVEL
WELL, THERE’D BE NO PARTICULAR ADVANTAGE TO STAYING ON THE SURFACE OF THE EARTH, REALLY. IT’S SPACESUITS OR NOTHING AT THAT POINT.
I DON’T KNOW. BUT IF WE DON’T TAKE THIS ON NOW, WHEN WILL WE? NOT WHEN WE’RE RUNNING AROUND IN SPACESUITS, I’LL WAGER.
THE BETTING IS, IF WE TAKE WHAT IS CALLED “NO ACTION”, MEANING WE KEEP MONKEYING WITH THE SYSTEM FOR INDIVIDUAL GAIN AND NO REGARD FOR MUTUAL LOSS, ABOUT 3 OR 4 C INCREASE IN GMST AND STILL RISING IN 2100; SOME SAY EVEN MORE.
SO HOW BAD DOES THAT SUCK?
Well, now we come to the hard question. How much suckage comes with each degree.Mark Lynas wrote a relatively alarmist book about that, and there has been some TV made around the book. It’s plausible. But we are somewhat out of the physical sciences and into economics and biology with that question. The science of ice sheets, while quite physical, has no precedents to base its predictions on. So to some extent we’re guessing.We haven’t talked about climate simulation models yet. The thing about climate models is that they have to be tuned to present day conditions to be useful as simulations. The more phenomena you add, the harder that is in principle. So the models have always had kind of a stodginess to them; one of their worst they do not deliver extreme events at the rate and extent that the real system does. And one of the biggest questions we have to ask is about extreme events. Eventually, it is possible that reality will be too far afield from where the models are tuned, and the models will get much further from reality than they are in present and recent past simulations. One of the ways they may fail is in telling us about extreme events.Now there are lots of theoretical reasons to expect more extreme events. And lots of reasons to expect the models can’t predict them well. At some point, it is plausible that the models will simply not represent some of the phenomena that the system actually gets.AT SOME LEVEL OF CLIMATE CHANGE MODELS LOOK LIKELY TO FAIL TO TRACK THE GENERAL WEIRDNESS LEVEL
So we don’t know if or when that time will arrive. We know climate will change, but in what ways, with what consequences. In other words, we don’t know at what temperature the changed climate really starts to bite. This has allowed us to delay policy, after all a change of 0.7 C locally is barely even measurable, never mind noticeable. How could it possibly matter as a change in GMST?WE DON’T KNOW AT WHAT GMST LEVEL THE WEATHER CONSEQUENCES OF CLIMATE KICK IN. OR…
OR AT LEAST WE DIDN’T UNTIL RECENTLY
WELL, IT APPEARS AS IF IT MAY BE HITTING THE FAN ALREADY
IT’LL HAVE TO WAIT FOR ANOTHER DAY
As one takeaway, names are important. Let’s call increasing GMST “increasing GMST” and anthropogenic climate change “climate change” please, or we will continue to get horribly confused by calling just about everything “global warming”.
Update: Woot! Moranoed on account of the spacesuits bit.
Welcome, folks, please come back for the planned sequel…