The story of climate change has always been more of worst-case, or at least, worser-case scenarios developing and less about good news showing up out of nowhere and making us unexpectedly happy.
A few decades ago, it became clear that the release of fossil Carbon into the atmosphere primarily as CO2 was going to cause a greenhouse effect (yes, dear reader, we've known this for looooong time ... the idea that this is a recent and still untested idea is a lie you've been fed so many times some of you may have begun to believe it). At that time climate scientists thought, reasonably, that there would be a diverse set of responses to the increase in CO2 and/or the increase in heat, some of which would accentuate the effects (positive feedback) and others would reduce the effects (negative feedback). Over time, the list of possible ameliorating effects became shorter and shorter and eventually pretty much disappeared. There is no double secret save-our-butts-at-the-last-minute Carbon "sink" nor is there any natural response that would cause cooling to somehow be caused by warming. Meanwhile, the list of accentuating effects has grown. Melting permafrost releases copious green house gasses. Melting sea ice in the Arctic allows the Arctic Sea to warm even more. Global warming-caused aridity causes numerous fires which coat the Greenland ice with soot, causing it to melt faster and do less of the work of reflecting sunlight back into space. And so on and so forth.
For these reasons, several years go you'd have climate scientists saying "well, this is important, and change is coming, but there's good news and bad news" and then the good news all went away and the bad news all stuck around, and every now and then, a new bad news item not previously thought of came along and lengthened that list. So already, climate change is worse than we thought.
Then we have the problem of scary empirical reality.
The Ghost of the Eemian
One of the most significant negative effects of global warming is likely to be sea level rise. Sea level rise so far has been significant, measurable, and important, but not large. As the earth warms because of increased levels of greenhouse gasses, the temperature of the ocean has increased, and this has caused the water in the ocean to expand, raising the level of the sea. At the same time, glaciers have been melting all across the planet, adding additional water to the sea, causing additional sea level rise.
So you can see that there is a link between temperature and sea level rise. More heat, more sea level rise. But there's a problem with this model. Based on prior experience, it seems that our planet normally responds to heat like we are experiencing now with a much higher sea level. During the Eemian period, the last time conditions were similar to the present, sea level was about 5 to 7 meters higher than now. In other words, given an admittedly small sample of 2 instances, when global temperatures are roughly like they are now, sea level can be anywhere between their current levels and 7 meters higher than current levels.
This is not the kind of relationship between important variables that allows us to say that sea levels are going to go down, or stay at their current level, or rise very slowly. These are the kinds of numbers that tell us that we really don't know what is going to happen over the next few decades, but that the chance that sea level will drop is zero, and the chance that sea level will rise only a little is slim, and the chance that sea level will rise quickly and a great deal at some point in time, or in a few spurts, is pretty good.
Predicting genocide using information about voting patterns
Which brings us to more details about the problem of sea level. Sea levels will rise the most not because of warming oceans but because of glaciers ... whopping big continental glaciers ... falling apart and slipping into the sea, or melting very rapidly and sending copious meltwater into the sea. Everything we know about the Greenland and Antarctic glaciers seems to indicate that at least some of this is going to involve large events, where big parts of big glaciers slide into the sea, rather than melting slowly like an ice cube in your sink. Also, the rates of melting during a handful of events observed over the last couple of years were entirely unpredicted and shocked scientists watching the process. Also, previously unknown causes of rapid melting are as we speak being discovered and measured.
Putting this another way, it would be a reasonable guess that the rate of continental glacial melting will be much higher than previously estimated, but also, the timing and speed of this ice wastage is pretty much unknown, and quite possibly unknowable except in very broad terms.
We have some very fancy models based on physics of ice melting and a few other variables that can be used to estimate ice melt and sea level rise. The problem is, these unpredictable and large scale catastrophic events have never been observed to happen. Yet, we think that they can happen in part because the rate of sea level rise thousands of years ago at the end of the last glacial maximum was so fast at times that it must have involved some pretty rapid events, more rapid than our models are able to predict. Our models can't predict these events not because the events can not happen but because the models have no way of dealing with them.
This problem reminds me of my days living in the Eastern Congo. Things were mostly peaceful. But, there were some tensions among various social factions, including different ethnic groups, different classes, and so on. There was tension along the borders between Zaire, Rwanda, and Uganda. But there was nothing whatsoever going on during my time there that would have predicted the Rwandan Genocide, the Congo War I or the Congo War II, or any of the troubles that I now realize were just starting then. This would be especially true if we were making careful sociological observations, measuring variables, taking polls, counting things, and so on and so forth. Major social upheaval comes when it comes, and is rarely accurately predicted by those carefully measured and modeled variables, and the timing and magnitude of those upheavals is never known in advance. And as human society so often goes, so may well go the glaciers of Greenland and the Antarctic. Our physics based models are going to look rather silly, predicting a melting rate of several centimeters a year, when three or four big-gigantic glacial monster fragments fall into the ocean within a year or two of each other along with a steady stream of slush causing ten years worth of sea level rise faster than you can say "property values in New York City may be slightly depressed" three times.
The Good News
There is no good news. But what often happens is that a bit of research comes along and looks like good news. This research is then identified, pointed to, repeated again and again, over-interpreted, used to argue that global warming is not real, and even used to argue that those who have been saying all along that global warming is real are making it up, on someone's payroll, are part of some huge conspiracy, etc. etc.
In other words, the progress of understanding of the potential future effects of climate change is set back significantly every time a research project with slightly good news, or even just less bad news than usual, is reported. This is ironic, because so many of those research projects have flaws in them that if taken account of suggest that the good news is not really there to begin with.
For example, a recent study seemed to show that the response of the planet to increased Carbon Dioxide is less than we expected it to be, but only over the short term. The difference between long term "climate sensitivity" (the amount of warming you get from a certain amount of greenhouse gas) and short term is probably where the heat goes not how much is added. Over the last few years, the ocean has been taking on a larger share of the heat from global warming, so the atmosphere has not warmed up as much (though it has warmed). But, the partial story ... that "sensitivity" is less for the present decade has been translated by various re-tellers of the science to suggest that we'll be fine. In fact, the slowdown in rate of atmospheric warming, which is still warming (like I just said) is called a "stall" in warming. But it is not a stall. It is a slow down in rate in atmospheric warming and a speed up in rate of oceanic warming. That is not really good news though it is reported as good news. But there isn't good news, just slightly more complicated news. (See this for a summary of that particular story.)
Not long ago another set of nuanced scientific observations were converted by the once reputable Matt Ridley in a piece in the Wall Street Journal, an outlet guilty of publishing this sort of misleading commentary on a regular basis, into "good news." In ...
“Cooling Down the Fears of Climate Change,” [Ridley] (falsely) asserts observations suggest global warming will be so low as to “be benificial.” This risible piece by Matt Ridley is so riddled with basic math and science errors it raises the question of how the Journal can possibly maintain its reputation as a credible source of news and financial analysis.
Of particular poignancy at the moment, since as I'm writing this the bodies of third graders are being pulled from a tornado-ravaged elementary school in Oklahoma, is discussion of the relationship between global warming and storminess. Storms are complicated. They vary in number from year to year, they vary in where they strike, and they vary in intensity per storm. Nonetheless there are patterns. There has been exactly one Atlantic hurricane in the south Atlantic ever, as far as we know. They only occur in the north. Tornadoes don't occur randomly; they are clustered mostly in certain regions of the world and mostly occur during certain months, though there is a lot of variation. (I discuss this at length here and here.)
Hurricanes are fueled by warm seas, and ripped apart by high level winds. Global warming causes sea surfaces to warm, and may also strengthen tropical and subtropical high level winds. So, does global warming mean more hurricanes or fewer? Or fewer but when they happen, stronger ones? Or what?
In the US, severe thunderstorms, bad straight line winds, and swarms of tornadoes typically arise from moist and warm unstable air masses organized along west to east and south to north moving fronts, with the heat and moisture starting out in the Gulf of Mexico, which is a big warm wet place during the summer. It stands to reason that if you heat up the Gulf, you'll get more of this, and global warming is heating up the Gulf. But the actual distribution and behavior of these fronts will also depend on the distribution of the famous "Jet Streams" and that is potentially altered by climate change. So, will global warming involve more tornadoes, stronger ones, or will they simply occur somewhere else? Or what?
There is one thing we know about storms. They are ultimately manifestations of heat, and more specifically, they result from the uneven redistribution of heat originally from the sun concentrated in tropical regions and moving towards polar regions by currents of water and air. In a heated up world there is more energy to feed storms. It is impossible to imagine a significantly warmed ocean and a significantly warmed atmosphere without significantly more storm activity and/or stronger storms, and maybe even some new kinds of storms. The problem is that it is hard to say what kinds of storms will increase, if there will be more of some kind of storm or more severe instances. For that matter, maybe all storm types will "increase" at one time or another, taking turns being the big storm problem for a few years, and sometimes that increase will be in numbers, sometimes in strength, sometimes manifest as a change in location of the patterned storm activity. That would be a statistical nightmare. It would be a lot of "moreness" of various phenomena but distributed across a range of different manifestations so that counting storms or measuring storms of specific types will show a pattern only after decades. This is why we sometimes look at overall damage to property from meteorological events over time, and there we do see a steady increase. It is also why the insurance companies, who are not stupid about these things, are so worried.
"Global warming appeasers" (people who pretend to understand the science but who are really trying to make climate change sound like it is not a big deal, like Ridley) and denialists alike are taking advantage of the statistical difficulty of measuring changes in patterns of storms to assert that "we can't link storms, or storminess, to climate change." But we can. We know there will be a link between a heated up earth and storm patterns, we are just more than a little uncertain as to what kind of change that will ultimately consist of.
Again, there will be no good news about storminess. Just more detailed news, and possibly a more nuanced understanding, which unfortunately will require more nuanced reporting and commentary.
Good luck with that.
Thanks, Greg, for putting this into perspective. I noticed that while Ridley is arguing "do nothing" at the same time he is saying he expects renewables to dominate in a few decades. Why he thinks that when he wants to do nothing now is anyone's guess. A fairy waving a magic wand perhaps?
This seems to be a common theme among the delayers. They assume that future generations will be much wiser than us, much more willing to take action in response to rising sea levels, much more willing to invest in adaptation than are the delayers of today.
From a sociological/psychological persepective this doesn't make a lot of sense. "Human nature" isn't going to change. If we cannot show that we are willing and able to invest in mitigation as well as adaptation today, why would we expect any different from future generations?
As for hanging all one's hope on only those 'predictions' that are supremely conservative without considering the whole, particularly the evidence from past climates - you've summed it up very well. It's called cherry-picking I believe.
Another possibility is that there will be fewer and weaker tornadoes, but in approximately the same location. We don't really know. Tornadoes are dependent upon large vertical wind shear in terms of occurrence and intensity. Wind shear is related strongly to horizontal temperature gradients. If the poles warm more than the equator, we'd expect wind shear to decrease.
It's more likely that we'll see an increase in the number, but not necessarily the intensity, of non-tornadic thunderstorm wind events.
Harold: We currently have one of the flattest gradients ever seen between equator and pole, so even though what you say here makes sense and in some way must be true, we are having some pretty bad tornadoes anyway. Perhaps these giant 1+ mile wide beasts that stay on the ground for tens of miles are a different thing. For that matter, the major known types of tornadoes may be different from each other in enough ways that we should be counting them differently.
Sou, I agree, and I would think he would be the kind of guy that would NOT expect a sudden change in human nature, given what he's written about human nature. In any event, we can all agree that could use more fairies, but that seems unlikely.
Even with the poles warming faster than the equator, horizontal temperature gradients aren't going away. As anybody who has ever lived near the ocean knows, the higher heat capacity of water means that inland areas warm faster during the day than areas along the immediate coast. The resulting sea breezes lead to thunderstorms in certain areas, such as Florida, although usually not tornadoes.
The key thing will be what happens to the jet stream. If it simply moves poleward, then Tornado Alley will probably shift poleward as well. But if we see more meandering, as has been the case the last few years, the likely result will be more tornadoes over a wider area than previously. That would be bad news for places like the Canadian prairie and New England, where tornadoes have been rare (although the Canadian prairie is the only place outside the US that has ever seen an F5/EF5 tornado).
Amongst those who recognize a problem, there is this sense that once we wise up and stop treating the atmosphere as a dump thing will magically get better. Unfortunately this is not true.
Mainly because of the large amount of heat the oceans hold and therefore the time they take to heat up, there are some huge lags in the system.
We have yet to see the extra heating from the Arctic Sea Ice that has already disappeared. No sea ice, less albedo, more heat stays in.
As well as all the CO2 we emit, we are also emitting aerosols. These aerosols are masking about half of the impact of the CO2 we have put up there. If we stopped polluting today they would wash out in twelve months or so.
So when we stop polluting, it will get worse and get worse very quickly. The longer we leave, it the higher the price of our Faustian bargain.
Forget the Eemian, we are headed to the Pliocene at a rate a biosphere will not be able to keep up with.
"...there is no good news..."
We have recently hosted a debate about global warming and I was surprised how personal and aggressive it could get. I can not see how this can resolve in the upcoming years.
The problem is the research itself. There are many theoretical flaws and biased researches nowadays.
My own goal is to promote veganism - it is probably the first reasonable step to reducing CO2 after the heavy industry and many coal plants that are still in work.
Changing our lifestyle can have a serious impact on how global warming proceeds. And I don't even mention the problem with droughts and the shrinkage of the drinking water in many regions of the world.
why does no-one mention the latent heat required to melt all this ice, this is ameliorating the temperature rise (I got this from James Lovelock) but I have yet to see it come up in an article
Yes, melting ice lowers the temperature of the atmosphere and/or ocean water nearby, which slows down the rate of global warming somewhat.
But, when the ice cubes in a drink melt, the drink will continue to get warmer because the room air is warmer still. So with the globe.
For the globe, this does give us some extra time. How much is impossible to say at present. But this would only matter if the heat imbalance were somehow corrected soon. Prospects for that appear dim.
By the way, this is not "amelioration." That word implies a permanent fix for some problem.
Good news, revised data, I guess you didn't get the memo..;
"... sea level was about 5 to 7 meters higher than now."
Was based on wrong data.
New data is here;
"...new research suggests this shoreline is actually about 30 feet (10 meters) lower than previously thought, meaning less ice melted than suspected."
Yeah, that would be nice. The situation is indeed complicated, but the high strandline is not confined to that coast, it is found around the world. Each case has to be examined on its own merits. The land moves up and down, and the shape of the surface of the sea varies. You can't just look at a single shoreline and make an estimate of earlier sea level. However, nor can you look at a single interplay between sea level surface and tectonics and rule out a particular strand line.
I've not looked at this specific research project, so I can't comment on it specifically yet but I'd be surprised if a single attempt at revision of a single area obviates all the research around the world that seems to come to the same conclusion.
Also, this is not the shoreline we are looking at to predict sea level rise. The relevant shoreline is the Eemian shoreline, not this one. So, this is only very marginally relevant.