Arguments
The consequences of climate change (in our lifetimes)
Posted on 17 April 2014 by Rob Honeycutt
Journalist Peter Hadfield (aka Potholer54) has a new video out on climate change issues. Peter takes his usual effective approach of imploring people to not rely solely on blogs for information. You have to actually read the published scientific literature, which is a proposition even Skeptical Science adheres to. (Authors at SkS are expected to cite references for their claims and we hope our readers take the time to follow through and check those sources.)
It's interesting that Peter is taking on the "in our lifetimes" aspect of climate change, because this is an issue I've often noticed that many people don't grasp. There are far too many people out there who somehow erroneously came to believe that all the predictions in Al Gore's An Inconvenient Truth were going to happen in a few years.
One of the most deeply complex aspects of climate change is cross generational responsibility. There are definitely impacts that we are already seeing, and we there are more impacts that we are going to see in the coming decades. But the worst is being saved for those who follow us. Our children and grandchildren.
Peter takes the time to carefully walk us through several aspects of climate change – ice melt, sea level rise, crop production, precipitation and feedbacks – with his engaging wit. And, with appropriate balance, he doesn't hesitate to address errors related to extreme climate impacts that are not scientifically supportable.
Peter also introduces us to a fantastic new meme that I think we should all consider adopting. He notes the often used "C" concatenated to AGW, saying we can't actually measure how "catastrophic" something is. We can, though, measure how expensive something is, and so maybe the better acronym would be EAGW.
As usual, Potholer gives us another well spent 18 minutes of video addressing climate change in an even handed manner.
When I heard about EAGW, I thought why not just rename CAGW to Costly AGW?
Hansen's 2012 statement, shows in the video, that we could get to a condition where the oceans would begin to boil was unfortunate and opened him to ridicule by the deniers. It shows the danger of simplifying complex matters for the public. In his most recent paper he was more careful in assessing the possibility of such an occurrence:
"In principle, an extreme moist greenhouse might cause an instability with water vapour preventing radiation to space of all absorbed solar energy, resulting in very high surface temperature and evaporation of the ocean [105]. However, the availability of non-radiative means for vertical transport of energy, including small-scale convection and large-scale atmospheric motions, must be accounted for, as is done in our atmospheric general circulation model. Our simulations indicate that no plausible human-made GHG forcing can cause an instability and runaway greenhouse effect as defined by Ingersoll [105], in agreement with the theoretical analyses of Goldblatt & Watson [128]." http://rsta.royalsocietypublishing.org/content/371/2001/20120294
I discount the possibility of the oceans evaporating based on the fact that it did not happen before when conditions on the earth were similiar.
Harry Twinotter - If you listen just a few seconds past that point Peter points out that boiling oceans aren't going to happen. That statement by Hansen is often taken out of context; the context that Hansen notes that while physically _possible_, it's not going to happen on Earth as the result of our emissions.
Context context context...
Harry Twinotter... I don't want to give any credence to the boiling oceans idea, but I don't believe the earth has had similar conditions as today. This is specifically because the rate at which we're introducing CO2 into the atmosphere is greater than even the Siberian Traps could have achieved.
I would also add that, eventually the oceans on earth will boil away. It's just not likely to be because of human carbon emissions.
Harry Twinotter @3, Rob Honneycutt @5, for some impacts of climate change (eg, extinction rates), rate of change in temperature is the most important factor. For others (eg, melting sea ice), it is absolute temperature that is the most important factor. For the potential of a runaway greenhouse effect it is the later. Of course, neither you nor I think the later is at all likely, and on current best evidence is not even possible in the coming millenia.
Having said that, it is possible that the Earth will soon face absolute temperatures conditions never faced before while complex life has existed on Earth. Below is a modified graph showing the radiative forcing due to CO2 concentration and insolation over the history of the phanerozoic (last 550 million years). The original is from Royer (2006). I have drawn in lines representing the radiative forcing in 2011 (2.23 W/m^2), and the expected radiative forcing for RCP 8.5 for 2100 (8.3 W/m^2) and 2300 (12 W/m^2).
As you can see, even in 2100, radiative forcing is expected to exceed any in the past 550 million years due to changes in insolation and CO2 concentrations. Those are not the only factors effecting radiative forcing, and the resolution of the graph is low. It is likely, therefore, that for shorter intervals than shown radiative forcing has exceeded that expected fro 2100, and possible that it has exceeded that expected for 2300. It is, however, by no means certain that worst cast BAU scenarios have ever been matched in the Earth's past.
BojanD @1, my preffered acronym is AGW, but I am happy to go with PCAGW, ie, Potentially Catastrophic Anthropogenic Global Warming. The point, however, is that catastrophic effects from global warming are not certain. Depending on what you consider to be catastrophic, they are even unlikely (0-33% chance) or very unlikely (0-10%). Therefore the use of CAGW, implying as it does a belief in a certain, or almost certain catastrophe from AGW, is a strawman. I have only ever seen it used for rhetorical effect by AGW deniers. Having said that, I, and I hope global policy makers, am not comfortable with even a 10% chance of a global catastrophe, and think we should do something about it.
Tom,
What an extraordinarily depressing graph! If positive feedbacks are bad (say a bunch of Arctic Methane) what will it look like? Hopefully renewable energy will continue to go down in price and replace fossil fuels more rapidly.
Tom... What also often gets missed in the statement that the earth has seen similar conditions is the fact that those conditions were such that the tropics we uninhabitable by complex organisms.
Going back to those conditions would, indeed, be catastrophic... And very expensive along the way.
Rob @9, I think the claim that the tropics were uninhabitable by complex organisms is overstated. What is true is that the tropics were seasonally uninhabitable by large mammals, where large means anything larger than a labrador. It would also have been extremely restrictive for some large cold blooded creatures, and for some small warm blooded creatures. Further, all warm blooded creatures would have been at a competitive disadvantage relative to cold blooded competitors, and relative to todays conditions. On top of that, small animals would have been at a competitive advantage relative to large animals, and relative to todays conditions.
That set of restrictions applies once you get sustained wet bulb temperatures of 35 C or more. In contrast, to truly limit complex organisms in general, you need sustained dry buld temperatures above 50-60 C.
Siberian gas venting and the end-Permian environmental crisis
Are you not comfortable with 10% chance of catastrophe?
Even 1 ppm (i.e. 0.0001% ) of chance of triggering the greatest massacre in human history (and possibly in all the planet history) would me be very very anxious if I were a policymaker.
To give one idea of what I am talking about, see this paper [insert link here] (moderator, please put my link inside the [])
It is about the most likely cause of the so-called Great Dying (officially Permian-Triassic extinction): a massive flood basalt eruption inside a oil and coal field in Siberia, the Tunguska Basin.
Basically the magma ignited the oil and coal releasing 100 000 Gt of CO2 (and some methane). Sounds familiar?
Tom, @7, I agree totally, that's why I like (C)ostly, because I could just refuse to play their game by acting obtuse and use costly instead.
For me human behaviour is the most frightening aspect of climate change. Not only the denial that it is happening but the breakdown of civilized society when food and water become inadequate to sustain a population growing at a rate of 200,000 a day. At what point you call it a catastrophe much depends on how well fed you are.
Another great potholer video, and the caveat at the end is a classic! (Make sure you hang around for it.) I'll just add that I would have liked to see more attention to Ocean Acidification...
To me the issue with it beng "too hot" is can agriculture continue. If it is too hot for cattle they cannot be raised. It is impossible to provide shelter to large scale agriculture animals. Can agriculture continue with goats? Will enough plants grow for the plants to live all year as food? Can food crops continue to be raised? If only weeds will grow few humans will be able to live there
Humans could devise shelters so that they can continue to live in areas that are too hot for them without shelter. Humans cannot live where they cannot raise food. It takes a lot of locally grown food to support a city. We see the interior of Australia does not support any cities because it is too hot to grow enough food. Even in the wet north they cannot support cities because the climate is hostile to cities.
Tom @10 is, as always, correct. We're talking about large mammals which could not survive at the tropics.
Sherwood and Huber 2010 is a good read on the human aspect of this topic. They state:
So, the broader point is that, the fact that "the earth has seen such conditions" in the past, doesn't preclude the catastrophic nature of such conditions on humans. Going back to PETM conditions would reduce the carrying capacity of the earth down to a small fraction of today's human population.
"For me human behaviour is the most frightening aspect of climate change."
Yes, but is it possible to change this?
Re: 6, It's interesting..
The Late Cretaceous is noted for very high sea levels compared to today - it seems that the whole ocean went over to thermohaline based circulation and warmed up significantly. Most currently inhabited areas were underwater in huge 'epicontinental' seas.
It's worrying that all other things being equal, the blue line on the graph for 2011 puts us at or around the point where no ice sheets are stable - certainly not the GIS and WAIS.
Peter says AGW does not alarm him, but (to paraphrase) the human reaction to the threat is alarming. I have to agree, with the caveat that I am alarmed by what AGW could do to our civilisation and, by inference, to our population. If our current cereal producing areas go out of production, what guarantees do we have that we can migrate our food plants as we migrate toward the poles? Sure, the cool areas may become warm enough to support our current prey organisms (plant and animal), but what will happen to plants adapted to a different day length, for example?
Will we see any concerted action before large numbers of people become alarmed enough to apply political pressure? I don't think so.
At the very least, the C in CAGW should stand for 'Concerning'.
How much will be said on here about the recent run-up in polar ice? It seems like my world got so cold this winter. 15 below zero on the saturday morning after my ski trip Feb 10th. I'm happy that 97% of the Arctic ice is back and Antarctic ice is above normal. But I know next winter will be another one with high heating bills. My house uses nat gas so that tempers things a little, but electricity per kwh has gone up 40% since 2009.
One thing I don't get is how the 33 cu miles of land melt on Antarctica can be the reason for a run uo to 13 million sq km of sea ice there? Seems like a drop in the bucket to me.