No, the polar bear population is not decreasing. In fact in Canada and other areas they are having more negative encounters with the bears due to the increased populations. Polar bears don't live on ice flows, think about this as well, most sea ice is frozen for the entirety of the winter months. The bears need open water to hunt prey.
The pictures used to show a bear desperately clinging to a small iceberg are distortions of reality, they don't need ice burgs to survive. A few years back the World Wildlife Foundation ran a fundraiser showing two scientists in white lab coats standing over a dead Panda, with the premise that people were randomly and senselessly killing Pandas, implying that this was going one almost daily. The fact is, they were two Chinese veterinarians who were preparing to do an autopsy on a Panda that died in a zoo in the 1950's. WWF made a fortune off of not telling the truth, the same scenario is happening with polar bears.
Not to be disparaging, but most people who are convinced of man made climate change live in the most densely populated and most intensely industrialized areas of the US. If I looked at Newark, NJ everyday, I could be persuaded to believe that mankind controls climate. I live in a very rural area, near 5 Wilderness areas and have temperature and weather records kept by members of my family for the last 100 years for the area. I took the time and crunched the numbers and there is no evidence of warming. What is revealed is a range that falls within normal variation. What really clued me in (being a descendant of weather geeks) was that as I travel for my occupation I check weather everywhere I go. If we had this widespread generalized warming, we should see it in record high temperatures. Most of the record highs should be fairly recent, with a heavier distribution in more recent years, but most record highs and lows occurred in 1906 and in the 1930s around the time of the Dust Bowl. According to the USDA 50% of the US was still farmed by horse teams in 1950. 1/3 of farm production was required to feed the livestock used to raise the crops. There was one paved highway from coast to coast, US 6. Most global warming happened before 1950.
CO2 numbers are listed as an absolute, 412 ppm. In the Amazon CO2 can be as high as 3000ppm, on the poles as low as 50 ppm. There is no absolute ideal CO2 number, and scientifically it should be listed in a range, in this worldwide example it would be 50-3000ppm. CO2 varies seasonal