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. It is going to 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]

The US presidential election will matter for 10,000 years

Now let's pull our perspective back to the current political situation in the US.

The recent unexpected death of Supreme Court Justice Antonin Scalia highlights and heightens the stakes involved.

If Hillary Clinton (or Bernie Sanders) is elected, she will appoint a liberal justice to replace Scalia. Obama's Clean Power Plan (CPP) will be upheld when it reaches the Supreme Court. Clinton will implement the CPP and build on it.

If Trump (or Ted Cruz or Marco Rubio) wins, he will appoint a conservative to the Court, and the CPP will be struck down. Or he'll just scrap the rule outright. And he will work to ease regulatory pressure on coal, boost oil and gas extraction, and remove policy supports for clean energy.

Numerous commentators have rushed to argue that the transition to clean energy will continue regardless of the CPP. And that's probably true; there are long-term drivers at work.

However, the lack of CPP would leave the door open to an unexpected spike in natural gas prices that revives coal, at least for a while. And it leaves no backstop to protect against moves by a Republican president to prop up the coal industry. Maybe it couldn't halt the transition in the US, but it could certainly slow it down, and it's already going way too slow.

More importantly, the CPP is of immense symbolic value on the international stage, as the tangible expression of Obama's promises at the Paris climate talks. It is those promises that pulled China on board, which in turn led to a snowball effect, pulling other developing countries in, yielding the unprecedented unity that emerged from Paris.

If the foundation of Obama's domestic climate plans is yanked away, it could strengthen the hand of skeptics and nationalists in China, India, and elsewhere, leading the whole superstructure to crumble.

If the Paris agreement falls apart — and especially if a Republican is elected president of the US in 2016 — it is very difficult to see international agreement building itself back up from the wreckage anytime soon.

Again, there are long-term drivers involved that probably make a global clean energy transition inevitable on some timescale. But the fracturing of the Paris consensus could render those efforts far more disparate, inconsistent, and slow than they might otherwise have been, which will mean many more gigatons of carbon in the atmosphere.

And as we've just learned, those extra gigatons will drive changes that endure, for all intents and purposes, forever.

Wrapping our heads around the connection between Trump and millennia

So the logic is inescapable: This presidential election will have effects that will be felt by the next 100 generations of Americans.

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.

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.

So it feels a little abstract and weird to say a presidential election will shape the Earth for centuries. But it is true.

More thoughts on this subject from the New York Times's Andrew Revkin and scientist Raymond T. Pierrehumbert, one of the authors of the Nature piece.