Sunday, June 19, 2011

IPCC reports should make projections based on a maximum human lifetime: 110 years

Supercentenarians - people who live to be 110 or older - are interesting for their own sake and as a reminder of the timescale we should keep in mind for climate change. We aren't just talking about future generations, we're talking about what the world will be like for people who are alive today.

Conveniently, the first IPPC report in 1990 focused on a 110-year time frame ending in 2100. Less conveniently, subsequent reports have each decided to emphasize a shorter time frame than the one before it, because each one also emphasized the 2100 time frame. If the Fifth AR due out in 2013-2014 time frame does the same thing, then people now alive will be in their 80's and still have their remaining lives relegated to a far-off time bin.

Choosing a maximum human life span is a good boundary zone for long term analysis. What that life span would be needs somewhat arbitrary delineation. The link above shows there are hundreds of people now alive who reach 110, so that seems pretty safe as a minimum number for a reasonable, maximum life span even under current, primitive technology, and again it matches what we started with in 1990. It would also have the advantage of reversing the increasing tendency of recent reports to downplay climate impacts by emphasizing shorter time periods.

The Fourth Assessment did look at conditions after 2100, but not in great detail and grouped together with impacts heading out to 2300. The Fifth Report will also look at impacts after 2100, in an as-yet unclear fashion. It should change the categories to say, up to 2125 and then after 2125 (UPDATE: corrected my problems with the advanced mathematics of addition). If not, then at least should provide much more detail as to what could happen in the early 22d Century, because it's appropriate to consider what current generations are going to face.


bruced said...

As a quadrodecadian scientist, I do not like this idea. Projections to 2100 and beyond are way past our data and understanding of a complex system. To plead my case consider a bit of basic physics i.e. doing a Hooke's Law experiment on a rubber band. Initially its all sweet and linear, but then chemistry intervenes and it gets non-linear. And then finally, gravity wins and the band goes snap.
Where are we with understanding the consequences of climate change? I'd suggest we are still in the equivalent of the linear phase but already the consequences of warming are beyond our predictive powers e.g. the massive rainfall events that have occurred worldwide. In my country (Aus) the national banana crop has been destroyed twice in the past few years by storms. Will this happen even more often with global warming to the point where we can't grow bananas?
An what of the non-linear events - the so called tipping points. If we can't predict their timing and effects then we are fooling ourselves if we think we can say what will happen in 2015.

badger badger badger said...

Perhaps it's all the better to say something along the lines of: We'd love to say something more definitive about later in the study period, but the increasing chances of everything jumping off the rails make that difficult. Sorry.

Recovering in the Florida Keys said...

Using the maximum human lifetime is interesting. It limits the fun we can have with statistics though. A small fraction of society will live to see 100 candles and a large percentage of those will not have the mental capacity to realize the magnitude of the event.

Those that live to 100 and retain enough mental capacity, may not be the desired poster model for healthy living.

Why not use the average life expectancy of non-smoking, vegan yoga practitioners devoted to homeopathic medicines? :)

Anonymous said...

The short-bias creep is happening even to Eli! I think you meant your "should" date to be 2125, not 2115.

Brian said...

Whoops! Thanks, Rust, it's corrected.

Anonymous said...

Our NRC report, "Climate Stabilization Targets," considered a big chunk of the whole Anthropocene -- out to the year 10,000 or so. There are certain things one can say over that time frame, and some things actually get simplier (e.g. it's much easier to melt Greenland if you have 5000 years to do it in). My understanding is that AR5 will specifically deal with the long term consequences of CO2 emissions -- Archer's "Long Thaw."

The full NRC report can be downloaded for free from the NAS web site. Just google "climate stabilization targets" and you'll get right there.


EliRabett said...

Since Mom Rabett made it to 100 and her mom to 95 (Dad was shorter lived, but the grandpas did ok) Eli eagerly looks forward to the coming apocalypse. If you make it past 75, 100 is not a totally unlikely outcome but you may have to give up food as the thin live much longer. OTOH, they don't enjoy it.

Anonymous said...

For the curious—a group I would argue includes all scientists and science geeks—the overwhelming incentive for staying alive is seeing what happens next.

I'm 64 and hoping for 40 more years, even if I have to watch my last sunset from a mud hut.

-Adam R.

Anonymous said...

@Eli: you may have to give up food as the thin live much longer

That may not be an optional course in coming years.

Another beneficial effect of global warming!

-Adam R.

Brian said...

Raypierre - thanks for the info. I've read Archer's book, it's great.

What I'm trying to do is to maximize the time frame that people can relate to. Saying a person now alive will see the consequences in 2125 might help do that. We should definitely look beyond that time frame to what future generations will be facing, as well.

Anonymous said...


My mother-in-law is now 97. She weighs < 90 lbs. My wife and I keep urging her to "eat, eat..." Pretty rare to have your weight (in lb) < your age (in years).

As the baby boomers age, the centenarian fraction of the US population will increase.

-Anonymous son-in-law.

Sou said...

I'd like to see short (30 year), medium (50 to 75 year), long (100 -150 year) and longer term (250 to 500 year) projections if that were possible. Especially so if there is the possibility of stabilising or not stabilising climate over the medium, long and longer term.

Don't people want to know if humans will survive 200 or 300 years hence? That's only a very short time in the history of civilisation. I remember seeing a cathedral in Cologne I think, that took 300 years or so to build.

I realise that the further out you go the more generalised the projections would be. Some projection is preferable to none at all.

Anonymous said...

I very much appreciate raypierre's approach to detailing the long-term consequences.

After all, even for lay people thinking back to the time of Jesus is a trivial matter, whether they comprehend the scale of time or not. Humans are very concerned about what happened thousands of years in the past, and they have used such history to justify wars, and the taking-back of land from peoples who have lived there for centuries when the newcomers have had no ties for as long, or longer, and all of this in the name of ancestors and traditions that no longer care a whit for - and never had any concept of what happens - in the future.

And yet here we are, making decisions for endless generations of our decendants and the biosphere in which they will live, and caring about what happens more than a decade or so hence is too much bother for the vast majority of people. Even for the thinkers, the century scale seems to be as much as they want to consider, as if everything plateaus at that time.

Um, no.

Frankly, if living with a 60" flatscreeen and a vehicle for every family now, means that my decendants in 500 years time will be living in the New Dark Ages, I'm happy to take on board the long-term consequences of the demand for such a contemporary lifestyle.

The problem is that Western society in general walks backward, not forward.

If the ethics and morals with which we live were good enough to draw from, from thousands of years ago, they should be just as good for projecting with, for thousands of years into the future. So why do we not extend the benefit of those ethics and morals to our great-great...grand kids 500 or a thousand years down the track?

Are we really that collectively self-indulgent?

Bernard J. Hyphen-Anonymous XVII

[Heh, Recaptcha said "chipless", as if it knew that humans seem to be collectively acting as though there is nothing to follow, from the old block...]

Bob Brand said...

Interesting post.

There is 'The Long Now Foundation', with eminent members like Brian Eno, John Baez and Kevin Kelly, which promotes the idea that we have crossed a cultural threshold into an age where past, present and future meld into one transparent 'Long Now'.

Technology, the Internet and digitization mean that sources and ideas are no longer tied to a particular epoch but become 'timeless', and just as accessible in the far future as they are now. In many ways that is already the case in scientific literature and even in entertainment, where digitized content is now available at the touch of a mouse.

In a sense, the Internet and digitization are as much of a cultural watershed as the invention of writing: not just written language becomes intergenerational but that goes for all kinds of content and interaction. They have a range of seminars and projects going at

Back on topic: yes, I'd say that projections ought to extend to 2150 at least.

Not only because of people getting older, but the relaxation time of perturbations to the atmosphere are of the order of 60 years to a 100 years at least (oceans and troposphere), but much longer once you factor in slow feedbacks such as icesheets, permafrost and changes in vegetation.

Consequences of our decisions are no longer limited to the immediate future and direct surroundings - they are irreversible. We need to move into The Long Now.

susan said...

Philosophical Society average age 89, but self-selected as (a) older to begin with (survived challenges of first half-century in many cases) and (b) tending to make rational lifestyle choices.

On history and memory, consider 1950s popularized TV and airplane travel (cheap tix new, though). Computers for common use started in 80s. Cell phones very new. Rock and roll new, hiphop even newer. Less than 100 years ago baths were not common; indoor plumbing also newish. I could go on. We have very short memories. 200 years of industrialization provided unimaginable things to consume with.