Irreversible but Not Unstoppable: the Ghost of Climate Change Yet to Come

Unlike Scrooge, we don’t get a spirit to show us what the future holds if we don’t change our ways.

That’s what we have science for.  In recent years, observations have confirmed the key projections climate scientists have been making for decades.  But some of the most important impacts have been occurring much faster than scientists expected, including sea level rise.  As recently as a decade ago, scientists did not expect that the great ice sheets of Greenland and Antarctica would melt enough this century to contribute much to total sea level rise.  Now, observations suggest they will be a primary if not the primary driver of sea level rise.

Recently, we’ve had many of the world’s leading scientists and scientific bodies warning us of what is to come.

Yes, it seems unlikely that we will adopt the aggressive but near-zero-net-cost policies needed to stabilize at 450 ppm atmospheric concentrations of carbon dioxide, and then quickly come back to 350 ppm, thanks in large part to the deniers, along with their political pals and media enablers.  But the two biggest carbon polluters (China and U.S.) have struck a game-changing deal that could ultimately avoid some of the worst impacts — if other key countries join in and then all countries pursue even stronger emissions cuts in the coming decades.
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The question of whether it’s “too late,” doesn’t have one purely scientific answer.  It does seem clear that the most dangerous carbon-cycle feedback — the defrosting permafrost — hasn’t kicked in yet but likely will within two decades, adding 0.4°F – 1.5°F to total global warming by 2100.  On the other hand, part of the West Antarctic ice sheet now does appear close to if not past the point of irreversible collapse.  That said, the worst case of sea level rise can still be avoided, as can many other of the most serious impacts.

If humanity gets truly serious about emissions reduction — and by serious I mean “World War II serious” in both scale and urgency — we could go to near-zero global emissions in, say, two decades and then quickly go carbon negative.  It wouldn’t be easy, far from it in fact.  But it would be vastly cheaper and preferable to the alternative.  A few years ago, scientists found the “net present value of climate change impacts” to be an astronomical $1240 trillion on our current emissions path, making mitigation to under 450 ppm a must.
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“Delaying action is a false economy: for every $1 of investment in cleaner technology that is avoided in the power sector before 2020, an additional $4.30 would need to be spent after 2020 to compensate for the increased emissions.”

Action now will save trillions and trillions of dollars.

Read more at Irreversible but Not Unstoppable:  the Ghost of Climate Change Yet to Come