the concern is that we aren’t in an ice age so even if global warming is natural, it will still melt the ice caps and flood the coasts unless we do something about it
There is absolutely nothing humans can do about it, any more than we can cap off a volcano to keep it from erupting.
The "20 foot sea level rise in 100 years" claim has been refuted by the IPCC itself:
The IPCC says sea-level increases up to 7 m (23 ft) above today’s levels have happened naturally in the past climate, and would only be likely to happen again after several millennia. In the next 100 years, according to calculations based on figures in the IPCC’s 2007 report, these two ice sheets between them will add a little over 6 cm (2.5 inches) to sea level, not 6 m (this figure of 6 cm is 15% of the IPCC’s total central estimate of a 43 cm or 1 ft 5 in sea-level rise over the next century). Gore has accordingly exaggerated the official sea-level estimate by approaching 10,000 per cent.
And so what if the sea level does creep up over the next 100, 200, or 300 years? People will just have to stop hitting up the US government for insurance for their beachfront property, that's all.
Use every one them, one at a time.
1) Right now, temperatures have risen: 1/2 of ONE degree in 36 years. In the last 9 years, temperatures have actually decreased slightly. 1/2 of ONE degree warmer temperatures are NOT causing serious weather problems ANYWHERE worldwide.
2) Increased CO2 has increased EVERY crop yields for wheat, barley, corn, beans, oats, maize, and peas AND EVERY OTHER natural and farmed plant has increased between 12% and 26% worldwide. Increased CO2 means EVERYBODY is getting more to eat. Longer growing seasons and more cropland mean even more areas can be set aside for nature, and also used for trees, plants, and growing food. More nitrogen's and fertilizers from better energy use will mean even more acres can be used for natural parks and wildlife rather than being cut down for burning as firewoood.
3) Man-caused CO2 has increased the greenhouse effect from 1.0000 in 1890 to 1.0028 right now. This little bit of change is present, but very little compared to the change in what the sun puts out.
4) Temperatures have cycled up and down before: There is NO indication that measured temperatures are rising any faster now than any time before. Temperatures rose in the 1870’s, 1930’, and 1990’s: Temperatures in the past have been much hooter than they are right now.
In the Roman era, in the 1000's, and right after the Ice Ages it was warmer than it is right now.
5) The Arctic is NOT melting: it was hotter before - in the 1930’s and 1950’s, and ALL of the animals survived just fine. Greenland ice packs are thicker now in most areas than they were before, and most areas of the Antarctic are COLDER now than they were earlier in the century. (One area in the Antarctic near the seacoast (about 3% of the total) is warmer than before. The rest is getting thicker ice, which means sea levels are going down - not up.
6) The UN doesn’t know how much sea levels will rise: They think between 3 and 18 inches. MAXIMUM. NO islands are in danger of sinking ANYWHERE in the world. If we decide to evacuate any islands, we have room for the 12,000 refugees from the lowest areas - but we don’t need to do that for another 150 years!
My concern is that there are people who actually believe we can halt the natural processes that have been going on for billions of years.
This is impossible by any significant criteria.
Plus, the effort to work against the natural cycles of the planet will bankrupt every economy on the planet foolish enough to try it.
Cities that MIGHT be affected by a improbably severe change in climate need to do the same thing our ancestors did when ice came down from the north and buried their villages... move.