Climate change is forever: considerable carbon emitted to date and in the next 100 years will remain in the atmosphere for tens to hundreds of thousands of years

April 7, 2016

The next decade or two offer “a brief window of opportunity to minimize large-scale and potentially catastrophic climate change that will extend longer than the entire history of human civilization thus far. Policy decisions made during this window are likely to result in changes to Earth’s climate system measured in millennia rather than human lifespans, with associated socioeconomic and ecological impacts that will exacerbate the risks and damages to society and ecosystems that are projected for the twenty-first century and propagate into the future for many thousands of years.”  Is there a moral argument for some threshold of environmental conditions that we must preserve for future generations?

temps stay high(NatureTemperature goes up … and stays up.

David Roberts reflects on the short, important article at: http://www.nature.com/articles/nclimate2923.epdf

The great irony of climate change is that it’s so big we can barely care about it.

I don’t mean out of malice or ignorance, though there’s plenty of both of those to go around. I just mean that the quantities, numbers, and timespans involved in climate change are so gargantuan that they dwarf our workaday human experience. They are literally difficult to think about, much less to connect to any personal meaning.

That’s why those green “change your lightbulb” campaigns always feel faintly ridiculous. It doesn’t take much thought to realize that the amount of energy involved in a lightbulb is a drop of water in the ocean of current human energy use, its emissions a tiny gust in a globe-spanning hurricane.

Because we have such trouble connecting the vastness of climate change to the limited horizons of our lived experience, we have trouble caring. It is a strenuous task to translate all the billions and gigatons into affective impact, into feelings. And most people are not in the market for more strenuous tasks. “If you try really hard, you can appreciate the horror” is not a pitch they want to hear. Life is hard enough already.

This is especially true at a time when current events are measured in “hours since Donald Trump last said something stupid,” when the #content torrent is so unending and unmanageable that it can lead to “popcorn brain,” a difficulty concentrating on extended chains of reasoning.

And yet, scientists tell us again and again that we are in a brief window of time when it is still possible to blunt the worst effects of climate change. Despite the enormity of climate change’s other numbers, that one is small: the time we have left to effectively act.

So let’s try an imaginative exercise. Let’s talk long-term climate consequences and then try to connect them to our current political moment.

Climate change is, for all intents and purposes, forever

Almost all climate models and reports, including those by the Intergovernmental Panel on Climate Change, focus on the near-term effects of rising greenhouse gas emissions. They almost all extend their analysis out to 2100 and then stop.

There are obvious reasons for this — the current century is of intense interest to those planning on living in it — but it also distorts our perspective in subtle ways. Most notably, it renders the post-2100 damages of climate change invisible; it allows us to think of the damage we’re doing as short-term or temporary.

As it happens, however, time is not going to stop in 2100. (And spatial aspects and place are of key importance, as Pope Francis and our Original Nations brothers and sisters remind us!)  2100 will be followed by 2101, and so forth. And the effects of climate change put into motion in this century will also continue accumulating.

A large group of scientists recently submitted a comment to the journal Nature in which they stressed this point. They note that a “considerable fraction of the carbon emitted to date and in the next 100 years will remain in the atmosphere for tens to hundreds of thousands of years.”

They argue for taking a longer view, modeling the previous 20,000 and the next 10,000 years, to put the climate changes being initiated today into proper geologic context.  If you’re interested in detailed results, read the paper (it’s pretty short), but the takeaway from the modeling is this: The changes we are setting in motion are irreversible.

  • Elevated atmospheric levels of CO2 will stay elevated for 10,000 years.
  • Global average warming over the 21st century “will substantially exceed even the warmest Holocene conditions, producing a climate state not previously experienced by human civilizations.” That unprecedented climate state will continue for 10,000 years.
  • Global mean sea level (GMSL), which has been reasonably stable throughout human civilization, is now rising, as the Earth seeks a new equilibrium with its higher temperatures. The rate of rise will itself increase, possibly higher than it’s been in 8,000 years. Total GMSL rise over 10,000 years is between 25 and 52 meters, several orders of magnitude higher than IPCC’s projections for 2100.

Though the scientists don’t go into it, such a large, rapid change in the Earth’s climate should be expected to radically reshape its flora and fauna as well, most notably through a rise in the rate of extinctions.

Because of the time lags involve in the climate system, short-term changes can be very difficult to predict, but over a long enough timescale, these kinds of effects become all but certain.

That means it’s not just our children who will inherit a world that’s hotter, more chaotic, and less biodiverse than the one their parents inherited. That will also be true for their children, and their children, and so on, for hundreds of generations. We are imposing adverse changes on more humans than have ever existed.

The scientists conclude:

This long-term view shows that the next few decades offer a brief window of opportunity to minimize large-scale and potentially catastrophic climate change that will extend longer than the entire history of human civilization thus far. Policy decisions made during this window are likely to result in changes to Earth’s climate system measured in millennia rather than human lifespans, with associated socioeconomic and ecological impacts that will exacerbate the risks and damages to society and ecosystems that are projected for the twenty-first century and propagate into the future for many thousands of years. [my emphasis]

Our decisions now will be felt by the next 100 generations.

Now, back to the dilemma with which we opened: Do you care about this?  Economists don’t think you do. In any calculation about possible future costs and benefits, economists use a “discount rate,” whereby we value future benefits less than present-day benefits.

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There’s a great deal of controversy over the correct discount rate to use in climate modeling — should we use the same rate we use for personal financial decisions? or some special, lower “intergenerational” rate? — but the fact is that any discount rate (above zero) is going to discount what happens 10,000 years from now.

We simply don’t have the economic language to discuss it. Nor do we have the moral imagination, really. Our intuitions about such vast temporal distances are soft and uncertain.

When you think about humans 100 years from now, do you see anything in particular? Do you feel any attachment to those people or responsibility toward them?

How about 200 years from now? How about 500?

The terror of the Anthropocene — our new geologic epoch, in which humans are the primary driver of global change — is that we have now grown in scale and power so much that our decisions echo across centuries. But our brains and moral instincts remain as tribal and parochial as ever.

Consequences of twenty-first-century policy for multi-millennial climate and sea-level change,” an important new Nature Climate Change analysis reinforcing past work showing a very, very, very long impact (tens of millenniums) on the Earth system — climatic, coastal and otherwise — from the carbon dioxide buildup.  The core conclusion:

This long-term view shows that the next few decades offer a brief window of opportunity to minimize large-scale and potentially catastrophic climate change that will extend longer than the entire history of human civilization thus far. [Read the Boston College news release for even more.]**

A summary from Columbia University’s Lamont-Doherty Earth Observatory captures the basic findings:

Humans have been burning fossil fuels for only about 150 years, yet that has started a cascade of profound changes that at their current pace will still be felt 10,000 years from now.

Another author of the Nature Climate Change paper, Daniel Schrag of Harvard, gave a highly relevant talk at the Garrison Institute a couple of years ago in which he raised a question to ponder:

Is there a moral argument for some threshold of environmental conditions that we must preserve for future generations?

10 Years Ago This Spring (by Joe Romm, cross-posted from Climate Progress):

Ten years ago Time magazine published a landmark cover on global warming with the headline, “Be Worried. Be Very Worried.”  The main story was a very solid, even prescient, piece of reporting — warning about polar ice loss, sea level rise, severe drought, and other extreme weather:

TimeSubHed2006

Indeed, Time warned that “global climate systems are booby-trapped with tipping points and feedback loops, thresholds past which the slow creep of environmental decay gives way to sudden and self-perpetuating collapse” — tipping points that a decade of inaction has brought us right to the edge of. The article even warns of the possible ramifications if warming shuts down the Gulf Stream or if our dawdling locks in multi-meter sea level rise — much the same concerns that James Hansen and 18 leading climatologists warned of in their recent bombshell peer-reviewed paper.

Except Time magazine laid it all out for all Americans to see 10 years ago when the possibility of avoiding the worst impact would have been far easier to achieve.

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What’s amazing is that not only did some members of the mainstream media pooh-pooh the cover story and the notion that we should be very worried about global warming back in 2006, but some of the very same “Very Serious” members still pooh-pooh the cover’s message and the entire notion of being very worried — as recently as this month!

Let’s be very clear that 10 years ago, anyone who spent a lot of time talking to leading climate scientists would have become “very worried” about what was likely to happen on the business-as-usual path of CO2 emissions. I did. That’s why I titled the book I wrote in 2006 “Hell and High Water” — and that’s why I launched this blog that same year.

The main differences in climate science between now and 10 years ago are:

  • Until the last year or two, emissions were tracking at the very highest end of what scientists had projected they would
  • Many of the most worrisome impacts have happened at a faster pace than climate scientists had expected
  • Most of the worst fears of climate scientists in 2006 are now part of the published peer-reviewed literature — and the worst fears of climate scientists today are beyond alarming

So people should be even more worried today — and they are! That’s why more and more leading climate scientists have become uncharacteristically blunt and why dozens of them told the world’s governments last year that we have to stay as far below 2°C as possible — preferably 1.5°C. And it’s why the world’s leading governments unanimously pledged to do just that in Paris in December.

Unfortunately, the amount of worry-generated climate action today — while vastly greater than the amount 10 years ago — is still lagging far behind the science. Beating 2°C requires a World War II-scale effort sustained for decades.

The good news is that we have the technology in hand or in the pipeline needed to ensure that beating 2°C is super-cheap, especially compared to the alternative.

The bad news is that our level of worry is nowhere near WWII scale. I’m sure we will have that level of desperation by, say, 2030, as the increasingly obvious and painful impacts continue to speed up. But after 25 years of dawdling, after 25 years of (most of) the major media downplaying the danger, we are out of time.

Even Time magazine — which nailed both the science and the need for urgent concern — underestimated the impact of the massive fossil-fuel-funded disinformation campaign and the anti-science lobbying effort. Ten years ago, Time wrote:

Environmentalists and lawmakers spent years shouting at one another about whether the grim forecasts were true, but in the past five years or so, the serious debate has quietly ended. Global warming, even most skeptics have concluded, is the real deal, and human activity has been causing it. If there was any consolation, it was that the glacial pace of nature would give us decades or even centuries to sort out the problem.

But glaciers, it turns out, can move with surprising speed, and so can nature.

How quaintly optimistic that sounds today. Again, Time got the science right: In the past decade, glaciers in Antarctica and Greenland have been moving much faster than the vast majority of scientists ever imagined. We are frighteningly close to the point of irreversible disintegration of both of the Greenland and West Antarctic ice sheets.