N.C.’s Coast Can Live with Warming

It’s that time of year in North Carolina, when everyone from Bird Island to Carova Beach fears the Big One that washes away the beach house. According to the state Coastal Resources Commission, each passing year brings an even greater threat, thanks to rising sea levels.

The CRC scared everybody by predicting a median of 38 additional inches of sea-level rise in the next 86 years. For comparative purposes, global warming was associated with an 8-inch rise since 1900.

It’s enough to make people panic before the apocalypse. So sell me your beach house. Please.

I’d like to offer you bottom dollar because a) everyone thinks your house is doomed and b) because everyone is probably wrong.

Note: Global warming is real and is caused, in part, by increasing atmospheric carbon dioxide, and a warmer world has higher sea levels.

So what? In climate, it’s not whether things change (they will, with or without our help), but how much they change.

Remember the adage, “It’s not the heat, it’s the humidity”? With regard to climate, that should be “It’s not the heat, it’s the sensitivity.”

“Sensitivity” is the amount of warming one gets for a doubling of carbon dioxide. Thanks to other greenhouse gas emissions, like methane, we’re already way past halfway there. The sensitivity is also a pretty good estimator of the change in surface temperature expected in this century.

Generally speaking, the ballpark “sensitivity” is estimated around 3.0°C (5.4°F). But the earth has been very reluctant to get with such a rapid warming program.

Global warming first burst onto the political scene on June 23, 1988, when NASA astrophysicist (and political activist) James Hansen testified that there was “a strong cause and effect relationship between the [then] current climate and human alteration of the atmosphere.” He also made a forecast, based upon two plausible scenarios for future carbon dioxide emissions. He predicted twice as much warming as has been observed.

In climate change, that’s the difference between something pretty substantial and something that is easily (and often unconsciously) adapted to. In North Carolina, there’s been an additional 10 inches of sea-level rise (for a total of 18 inches, since 1900) at Duck, thanks to the fact that the land there is sinking. People slowly adapted by stabilizing the dunes and building new homes on pilings.

No regulatory fiat, by the CRC or anyone else, is going to stop the coast from subsiding. But Duck is kind of an outlier. Further south, by Wilmington and Southport, the rise of the ocean is pretty much in step with the global average.

Other forecasts of warming are also too high. For example, the “midrange emissions” suite of models used by the United Nations Intergovernmental Panel on Climate Change appears to be predicting about a third more warming than we are getting.

CRC forecasts curiously use a much higher emission scenario than this, and it is clearly wrong. It was made before the discovery of hundreds of years supply of shale gas, which emits about half of the carbon dioxide of coal when used for electrical generation. Adjusting for CRC’s forecast errors (as well as for observed warming trends) yields a sea-level rise of about 13 inches from now to 2100.

But won’t the temperature rise accelerate and sea-level rise quicken?

Not if we believe the mathematical form of the Intergovernmental Panel’s midrange computer models. Contrary to talk about “ever-increasing warming rates,” these models in fact tend to predict a constant rate of warming. Indeed, a graph of the globe’s temperature history since the second warming of the 20th century began, over a third of a century ago, shows a remarkably constant rate of about 1.6°C (2.9°F) per century.

The CRC’s 38-inch projection is based upon almost three times as much warming as is being observed. For CRC to be right, the rate of warming will have to increase dramatically, but that would violate the U.N.’s models showing a constant rate.

Which reminds me, here’s my offer for your beach house….
