Do bloggers know more about sea level change than the NSF?

See that's exactly why you have to rely on science. Sea levels have gone up 100 meters in the last 20,000 years. On average, that's only 5mm per year on average, or 1.2 inches in 69 years---far smaller than the random variation in that time. But even that is misleading--most of that change occured before 10,000 years ago, and in the last thirty years, the real--measured--change has averages 1.3mm per year.

Here is the reality:
1. Sea level has been increasing for a long time and will continue to increase for a long time.
2. Human activities are a contributing factor. No one know how much, but it's probably modest at this time.
3. The scientific community only notices these changes late in the game, and the overreaction of a few needlessly polarized the issue. (Eliminating cars for a wold of flower children might help, but only a bit, and not enough to justify the new problems it created.
4. Conservative overreaction to this overreaction has only made the needless polarization worse. Climate IS changing. Sea levels ARE rising. Pretending that all the world climatologists are just drug addled liberals will not make it stop.
5. This is all going to continue. We are NOT going to stop, or even curtail fossil fuel use because of it, though we can and should slow expansion where we can.
6. Long term, we need to ensure that CO2 stays well below the 900 parts per million that we know the biosphere can handle.
7. Mid-term (next century or so), ocean acidification, accelerated by fossil fuel consumption is probably a bigger risk to more people than seal level, climate change or weather.
8. Climate change is going to continue. We can adapt by pissing on one another until war and famine break out, or we can use these fancy brains to solve the problems it brings about.
9. Oh yeah, and at the rate things are going, Antarctica will be the world's bread basket inside 500 years
10. Lot's of species are going to die. We all like Penguins and Polar bears, but we are not Gods. Deal with it.

That's the way it is.

Yes and no.

A 4 cm sea level rise is no big deal, but adds to the total due to thermal expansion and antarctic ice melt. Even that is currently only projected to be modest in the next century. Eventually, there is enough ancient freshwater ice sitting atop Antarctica and Siberia to raise sea levels by 100 meters.

Sea level was 100 meters higher during much of the cretaceous and 100 meters lower during the height of the ice age. Current climate change is mostly due to the end of that ice age---which, contrary to popular opinion, is still going on and has been abating throughout human history. While burning fossil fuels is unquestionably speeding the process, it is NOT the cause. Pundits on both sides consistently get this wrong. The few inches of sea level rise projected over the next century are mostly NOT anthropogenic. But if we keep burning fossil fuels as we are now, the 100 meter rise over the next few centuries will be.

No climatologist is worried about annual sea ice extent. Scientists are not stupid. Only permanent ice counts. BTW, as long as permanent ice exists, the last ice age is not over--that's the definition of an ice age. We talk about it ending 10,000 years ago, but in fact, it peaked 20,000 years ago and has been retreating since. 10,000 years ago is when it got warm enough for most of the temperate latitude to be clear of ice and available to human exploitation.

The 2.6% volume increase accounts for the desalination gradient you speak of and many other factors. Again, while journalist on both side of the issue often are, scientists, as a general rule, are not stupid.